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Project Documentation Document SPEC-0146
Revision A
High-Order Adaptive Optics Design Requirements
Luke Johnson, Keith Cummings, Mark Drobilek, Scott Gregory, Erik Johansson, Kit Richards, Friedrich
Wöger
WFC Group
April 2018
Name Date
Released By: Rob Hubbard
Systems Engineer 30-April-2018
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page ii
REVISION SUMMARY:
1. Date: August 2016 Revision: Draft Changes: First draft of the requirements.
2. Date: April 2018 Revision: A Changes: Significant updates. Initial revision-controlled release for CDR.
3.
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Table of Contents
1. Overview .............................................................................................................. 1
1.1 Document Scope ................................................................................................ 1
1.2 Related Documents ............................................................................................ 1
1.3 Interface Control Documents ............................................................................ 1
1.4 Verification Methods .......................................................................................... 1
1.5 Specific Definitions and Terminology .............................................................. 2
2. General Requirements ........................................................................................ 4
2.1 WFC general requirements ................................................................................ 4
3. HOAO Optical Requirements .............................................................................. 5
3.1 M5 Optical Requirements .................................................................................. 5
3.2 M10 Optical Requirements................................................................................. 5
3.3 HOWFS Optical Requirements .......................................................................... 5
3.3.1 Optical Interface ........................................................................................................... 5
3.3.2 Optical Design .............................................................................................................. 5
3.3.3 Optical Performance .................................................................................................... 8
3.3.4 HOWFS Field steering mirror....................................................................................... 9
3.3.5 Lenses ........................................................................................................................... 9
3.3.6 Microlens array ............................................................................................................19
3.4 NCP Wavefront Sensor .................................................................................... 20
3.4.1 Beam expansion optics...............................................................................................20
3.4.2 PA&C reflective sphere ...............................................................................................20
3.4.3 NCP reference flat .......................................................................................................21
4. HOAO Mechanical Requirements .................................................................... 22
4.1 M5 Assembly ..................................................................................................... 22
4.1.1 Mount positioning: resolution ....................................................................................22
4.1.2 M5 dummy ...................................................................................................................22
4.1.3 Uniformity between M5 Assembly and M5 dummy ...................................................22
4.1.4 Mechanical Performance ............................................................................................23
4.2 DM Assembly .................................................................................................... 23
4.2.1 M10 dummy..................................................................................................................23
4.2.2 Uniformity between M10 Assembly and M10 dummy ...............................................23
4.2.3 Mechanical Performance ............................................................................................23
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4.3 HOWFS Stages and Mechanisms .................................................................... 23
4.3.1 Locking mechanisms ..................................................................................................23
4.3.2 Field Steering mirror ...................................................................................................24
4.3.3 Objective lens assembly .............................................................................................24
4.3.4 Field stop mount assembly ........................................................................................25
4.3.5 Pupil lens mount assembly ........................................................................................26
4.3.6 Lenslet array mount assembly ...................................................................................26
4.3.7 Relay lens #1 mount assembly ...................................................................................27
4.3.8 Relay lens #2 mount assembly ...................................................................................28
4.3.9 Camera mount assembly ............................................................................................29
4.4 HOWFS Optics mount stability ........................................................................ 29
4.5 HOWFS Camera ................................................................................................ 30
4.5.1 Format ..........................................................................................................................30
4.5.2 Pixel size ......................................................................................................................30
4.5.3 Quantum efficiency .....................................................................................................30
4.5.4 Fill factor ......................................................................................................................30
4.5.5 Full Well .......................................................................................................................30
4.5.6 Linearity .......................................................................................................................31
4.5.7 Artifacts ........................................................................................................................31
4.5.8 Frame Rate ...................................................................................................................31
4.5.9 Flexible Integration time .............................................................................................31
4.5.10 Read Noise ...................................................................................................................31
4.5.11 Internal Noise ...............................................................................................................31
4.5.12 Bias Frame Stability ....................................................................................................32
4.5.13 Pixel Gain Stability ......................................................................................................32
4.5.14 Digitization ...................................................................................................................32
4.5.15 Faint Image Tracking ...................................................................................................32
4.5.16 Granulation tracking ...................................................................................................32
4.5.17 Streaming readout .......................................................................................................32
4.5.18 Read latency ................................................................................................................33
4.5.19 Full-frame read time ....................................................................................................33
4.5.20 Simultaneous readout .................................................................................................33
4.5.21 Power dissipation ........................................................................................................33
4.5.22 Heat management........................................................................................................33
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4.6 HOAO calibration sources ............................................................................... 33
4.6.1 HOAO GOS pinhole .....................................................................................................33
4.6.2 GOS calibration lamp ..................................................................................................35
4.6.3 GOS reflective sphere .................................................................................................35
5. HOAO Algorithm Functionality REQUIREMENTS ........................................... 36
5.1 Extract multiple Regions of Interest from Full Frame ................................... 36
5.2 Dark Calibration ................................................................................................ 36
5.3 Gain Calibration ................................................................................................ 36
5.4 Calibration of subaperture images ................................................................. 37
5.5 Subaperture Shift Measurement ..................................................................... 37
5.5.1 Cross-correlation algorithm .......................................................................................37
5.5.2 Computation of image displacements to subpixel accuracy ...................................38
5.6 Wavefront Reconstruction ............................................................................... 38
5.7 PI Servo Loop ................................................................................................... 38
5.8 Tip-Tilt Derotation ............................................................................................. 39
5.9 Fast Tip-Tilt Offload to Mount .......................................................................... 39
5.10 R0 calculation .................................................................................................... 40
5.11 Residual error calculation................................................................................ 40
5.12 DM rms calculation ........................................................................................... 41
5.13 HOAO Modal Coefficient Computation from Subaperture Shifts ................. 41
5.14 HOAO Modal Coefficient Computation from Actuator Commands .............. 42
5.15 HOAO Modal Coefficient Confidence ............................................................. 42
5.16 DM Interactuator Voltage Limitation ............................................................... 43
5.17 OOB Subaperture Shift Detection ................................................................... 43
5.18 DM Interaction Matrix Calibration ................................................................... 44
5.19 HOAO Automatic Gain and Reconstruction Matrix Optimization ................. 44
5.20 Mitigation of Bad Seeing or Loop Instability .................................................. 44
5.21 HOWFS Automatic exposure time adjustment .............................................. 46
5.22 HOWFS Pupil position measurement ............................................................. 46
5.23 Absolute Error after Calibration ...................................................................... 47
5.23.1 Total wavefront error ...................................................................................................47
5.23.2 HOAO error budget .....................................................................................................47
6. HOAO Software Requirements ......................................................................... 48
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6.1 General Requirements ..................................................................................... 48
6.1.1 Division of software tasks ..........................................................................................48
6.2 HOAO System Settings Requirements ........................................................... 48
6.2.1 WFC mode ...................................................................................................................48
6.2.2 r0 Calculation Period ...................................................................................................48
6.2.3 r0 Calculation Frameskip .............................................................................................49
6.2.4 aO Engine Event Period ..............................................................................................49
6.2.5 aO Engine Event Basis ...............................................................................................49
6.2.6 aO Engine Event Frameskip .......................................................................................50
6.2.7 HOAO Frame Rate .......................................................................................................50
6.2.8 HOAO Camera Exposure Control Method .................................................................50
6.2.9 HOAO Camera Exposure Time ...................................................................................51
6.2.10 HOAO Minimum Flux per Exposure ...........................................................................51
6.2.11 HOAO Maximum Flux per Exposure ..........................................................................51
6.2.12 HOAO Exposure Time Update Period ........................................................................52
6.2.13 Load High-Order Reconstruction Matrix ....................................................................52
6.2.14 Load Low-Order Shift Reconstruction Matrix ............................................................52
6.2.15 Load Low-Order Actuator Reconstruction Matrix .....................................................53
6.2.16 Servo Gain Update period ...........................................................................................53
6.2.17 High-Order Servo Loop DM Gain Control Method .....................................................53
6.2.18 High-Order Servo Loop DM Gains ..............................................................................54
6.2.19 High-Order Servo Loop FTT Gain Control Method ....................................................54
6.2.20 High-Order Servo Loop FTT Gains .............................................................................54
6.2.21 Load Actuator Gains Array .........................................................................................55
6.2.22 Load Actuator Offsets Array .......................................................................................55
6.2.23 Reference Subaperture ID ...........................................................................................55
6.2.24 Reference Image Update Method ...............................................................................55
6.2.25 Reference Image Update Period .................................................................................56
6.2.26 Reference Image Tolerance Threshold ......................................................................56
6.2.27 Reference Image Contrast Threshold ........................................................................56
6.2.28 Get New Reference on Lock .......................................................................................57
6.2.29 Get Immediate Reference ............................................................................................57
6.2.30 Get Tolerance Reference ............................................................................................57
6.2.31 Apply DM Actuator Map ..............................................................................................58
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6.2.32 Apply DM Modal Coefficients .....................................................................................58
6.2.33 DM Out of Bounds Threshold .....................................................................................58
6.2.34 DM OOB Gain Increment .............................................................................................59
6.2.35 DM OOB recovery period ............................................................................................59
6.2.36 FTT Out of Bounds Threshold ....................................................................................59
6.2.37 FTT Out of Bounds Gain Increment ...........................................................................60
6.2.38 FTT OOB recovery period ...........................................................................................60
6.2.39 FTT Range Offload Threshold ....................................................................................60
6.2.40 FTT Offload Period ......................................................................................................61
6.2.41 FTT Offload Gain .........................................................................................................61
6.2.42 Pupil Motion Subaperture Selection ..........................................................................61
6.2.43 Pupil Motion Measurement Period .............................................................................62
6.2.44 Number of Images to Accumulate ..............................................................................62
6.2.45 Load DM registration pattern ......................................................................................63
6.3 HOAO System Mode Requirements ................................................................ 63
6.3.1 Off .................................................................................................................................63
6.3.2 Idle ................................................................................................................................63
6.3.3 Calibrate .......................................................................................................................63
6.3.4 WFC-OPM1: Diffraction limited on-disk .....................................................................67
6.3.5 WFC-OPM2: Seeing limited on-disk ...........................................................................68
6.3.6 WFC-OPM3: Seeing limited coronal ...........................................................................68
6.3.7 WFC-OPM4: Limb occulting with image stabilization ...............................................69
6.4 Mechanism Control Requirements ................................................................. 69
6.4.1 Field Steering Mirror Postion......................................................................................69
6.4.2 Objective Lens Look-up Table ....................................................................................69
6.4.3 Objective Lens Position ..............................................................................................69
6.4.4 Active Field Stop Assembly Aperture .............................. Error! Bookmark not defined.
6.4.5 Microlens Array Position ............................................................................................70
6.4.6 Relay Lens #1 Position ...............................................................................................70
6.4.7 Relay Lens #2 Position ...............................................................................................70
6.4.8 Camera Mount Position...............................................................................................70
6.4.9 Camera Relay Optics Assembly Position ..................................................................71
6.5 Interface Requirements .................................................................................... 71
6.5.1 WCCS interface ...........................................................................................................71
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6.5.2 Engineering user interface .........................................................................................71
6.5.3 HOAO status screen ....................................................................................................71
6.6 Real-Time system requirements ..................................................................... 72
6.6.1 Compute time ..............................................................................................................72
6.6.2 FPGA firmware ............................................................................................................72
6.7 HOAO telemetry data products ....................................................................... 72
6.7.1 Telemetry latency ........................................................................................................72
6.7.2 Telemetry data format .................................................................................................73
6.7.3 Header Data .................................................................................................................73
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1. Overview
1.1 Document Scope
The High-Order Adaptive Optics (HOAO) Design Requirements Document (DRD) details all
requirements used to guide the design of the HOAO component of the Wavefront Correction (WFC)
system.
1.2 Related Documents
SPEC-0001, Science Requirements Document
SPEC-0005, Software and Controls Requirement
SPEC-0012, DKIST Acronym List and Glossary
SPEC-0013, Software Concepts Definitions
SPEC-0014, Software Design
SPEC-0022, Common Services Framework Reference Design
SPEC-0058, Wavefront Correction System Specifications Document
SPEC-0063, Interconnects and Services
SPEC-0061, Hazard Analysis Plan
SPEC-0068, M5 Tip Tilt Module Specification
SPEC-0070, DKIST Standard Environmental Conditions
SPEC-0109, M5 Tip Tilt Mirror Specification
SPEC-0111, M10 Deformable Mirror Specification
SPEC-0125, High Order Adaptive Optics Real Time FPGA Firmware Specification
SPEC-0129, Wavefront Correction Operational Concepts Model
SPEC-0147, High Order Adaptive Optics Critical Design Document
SPEC-0149, Haleakala Environmental Design Specification
SPEC-0174, WFC Generic Requirements
[1] Generic Criteria for Vibration-Sensitive Equipment, Colin G. Gordon, Proc. SPIE 1619, 1991.
1.3 Interface Control Documents
ICD 1.2-2.3 M1 Assembly to Wavefront Correction Control System
ICD 1.3-2.3 Top End Optical Assembly to Wavefront Correction Control System
ICD 1.5-2.3 Feed Optics to Wavefront Correction Control System
ICD 2.1-2.3 Wavefront Correction Coudé to Wavefront Correction Control System
ICD 2.3-4.4 Wavefront Correction Control System to Telescope Control System
1.4 Verification Methods
Included in each major numbered specification listed in this document is a requirement verification
method. These verification methods specify the minimum standards of verification required to ensure that
the individual requirements and specifications are met.
Examples of verification methods include:
Design Review. Verification by design review means that it is shown during an appropriate
design review that the system meets specification by way of its intrinsic design and configuration.
Analysis. Verification by analysis demonstrates that the design meets the specification through
use of performance modeling metrics.
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Test. Verification by test and/or measurement means that it is demonstrated that the as-built
system meets the specification through measurements of its operation performance. Testing is
performed during acceptance testing and/or as part of a pre-ship readiness review.
Inspection. Verification by inspection means that visual inspection verifies that the specification
has been achieved on the as-built system during preassembly and/or during Site assembly.
1.5 Specific Definitions and Terminology
Daniel K. Inouye
HOAO
K-L
High Order Adaptive Optics
Abbreviation Meaning
α
β
γ
aO
CDD
CSF
CV
DIQ
DKIST
Slow rotation about the local x-axis
Slow rotation about the local y-axis
Slow rotation about the local z-axis
Active Optics
Critical Design Document
Common Services Framework
Context Viewer
Delivered Image Quality
Daniel K. Inouye Solar Telescope
DM
DRD
Deformable Mirror
Design Requirements Document
FOV
FTT
GOS
HOAO
HOWFS
IT&C
K-L
LOWFS
LT
LUT
M1CS
ms
NCP
nm
Field-of-view
Fast Tip-Tilt
Gregorian Optical Station
High-Order Adaptive Optics
High-Order Wavefront Sensor
Integration, Testing, and Commissioning
Karhunen-Loéve (modal basis)
Low Order Wavefront Sensor
Limb Tracker
Lookup Table
M1 Control System
millisecond, 10-3 second
Non-Common Path
nanometer, 10-9 meter
OCD Operational Concepts Definition
OCS
OOB
QSA
RTC
SRD
TCS
TEOACS
TMA
VC-B
Observatory Control System
Out-of-box, shifts that are larger than the subaperture capture range
Quasi-Static Alignment
Real-Time Controller
Science Requirements Document
Telescope Control System
Top End Optical Assembly Control System
Telescope Mount Assembly
Vibration Criterion, class B (25 µm/sec rms)
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WBS
WCCS
WFC
Work Breakdown Structure
Wavefront Correction Control System
Wavefront Correction System
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2. General Requirements
High Order Adaptive Optics (HOAO) requirements flow down from top-level Wavefront Correction
(WFC) science and operational requirements as well as general facility requirements for DKIST. In some
instances, the flowdown is explained in more detail in the HOAO Critical Design Document (CDD), in
which case the HOAO CDD will be referenced as a secondary origin of the requirement.
2.1 WFC general requirements
The WFC HOAO shall meet all applicable WFC Generic requirements. These requirements shall be
tracked in the HOAO Compliance Matrix (CMX-0007) and assigned numbers prefixed with the HOAO
WBS number, 2.1.1.
Verification: Varies
Requirement Origin: Science, Engineering, Operations, Safety (SPEC-0174)
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3. HOAO Optical Requirements
3.1 M5 Optical Requirements
M5 optical requirements are contained in SPEC-0109. The compliance matrix associated with these
requirements appears in the L3/Brashear contract documents.
3.2 M10 Optical Requirements
M10 optical requirements are contained in SPEC-0111. The compliance matrix associated with these
requirements appears in the AOA Xinetics contract documents.
3.3 HOWFS Optical Requirements
3.3.1 Optical Interface
REQ# 2.1.1-1000
The HOWFS optical interface shall be defined by the reflective surface of the HOWFS/CV beamsplitter.
Verification: Design Review
Requirement Origin: Engineering
3.3.2 Optical Design
The Optical Design Requirements that appear in this section are those used to drive the optical design of
the HOWFS. After completion of the design, requirements on optical components were created based on
the accepted final optical design. Many of the component-level requirements in following sections
supersede the requirements in this section. However, the requirements in this section remain to justify the
decisions made during the HOWFS optical design process.
3.3.2.1 Sensor Type
REQ# 2.1.1-1005
The HOWFS shall be a Shack-Hartmann wavefront sensor.
Verification: Design Review, & Inspection
Requirement Origin: Science (SPEC-0058, 2.1.1-0010)
3.3.2.2 Pupil imaging capability
REQ# 2.1.1-1010
The HOWFS shall be able to be reconfigured so that the pupil-plane lenslet array is imaged on the
detector, with the full pupil diameter not exceeding the active sensor length or width, but extending at
least 80% across the smaller of active sensor length and width. The steps required to achieve this
configuration shall be automated through the use of translating stages.
Verification: Design Review, Inspection, & Test
Requirement Origin: Engineering (SPEC-0129, 4.3.6)
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3.3.2.3 HOWFS Off-Pointing
REQ# 2.1.1-1015
The HOWFS shall be able to adjust its pointing so that the center of the HOWFS field of view is
displaced from the telescope boresight by 20 arcseconds in any direction.
Verification: Design Review, Analysis & Test
Requirement Origin: Science (SPEC-0058, 2.1.1-0125)
3.3.2.4 Subaperture count
REQ# 2.1.1-1020
The HOWFS shall contain 43 fully-illuminated subapertures across the pupil diameter, with a total of
1405 fully-illuminated subapertures.
Note: For purposes of this requirement, a fully-illuminated subaperture is defined as a subaperture whose
active lenslet area is ≥ 90% filled by the telescope pupil.
Verification: Design Review & Analysis
Requirement Origin: Engineering (SPEC-0111, DMS-REQ-0004)
3.3.2.5 Subaperture Field of View
REQ# 2.1.1-1025
Each subaperture of the HOWFS shall have a FoV of 10 0.5 arcseconds.
Verification: Design Review, Analysis & Test
Requirement Origin: Science (SPEC-0058, 2.1.1-0025; SPEC-0147)
3.3.2.6 Pupil Size
REQ# 2.1.1-1030
The pupil diameter on the HOWFS lenslet array shall be larger than 16.0 mm and smaller than 25.0 mm.
Verification: Design Review, Analysis & Inspection
Requirement Origin: Engineering (SPEC-0147)
3.3.2.7 Pupil Adjustability
REQ# 2.1.1-1035
The pupil size on the HOWFS lenslet array shall be adjustable to at least 15% of its nominal value.
Note: This adjustability is to allow for compensation of manufacturing defects during alignment.
Verification: Design Review, Analysis & Test
Requirement Origin: Science (SPEC-0058, 2.0-0015, SPEC-0147)
3.3.2.8 Lenslet focal length
REQ# 2.1.1-1040
The focal length of the lenslets in the HOWFS lenslet array shall be greater than or equal to 25 mm and
less than or equal to 100 mm.
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Verification: Design Review & Test
Requirement Origin: Engineering (SPEC-0147)
3.3.2.9 Subaperture image separation
REQ# 2.1.1-1045
Subaperture images at the detector plane of the HOWFS shall not overlap each other, nor shall any two
adjacent subaperture images be separated by more than one pixel (11.5 microns).
Verification: Design Review & Inspection
Requirement Origin: Engineering (SPEC-0147)
3.3.2.10 Plate Scale
REQ# 2.1.1-1050
The final focal plane of the HOWFS shall have a plate scale of 43.48 2.17 arcseconds per mm.
Note: the HOWFS camera is required to have 11.5 micron square pixels (REQ# 2.1.1-2155) and each
subaperture has a 10 arcsecond square field of view. To obtain 20 pixels across each subaperture, the final
plate scale must be (100.5)/(20 *11.5e-3) = 43.48 2.17 arcseconds/mm
Verification: Design Review, Analysis & Test
Requirement Origin: Science (SPEC-0058, 2.1.1-0025; SPEC-0147)
3.3.2.11 Plate Scale Adjustability
REQ# 2.1.1-1055
The plate scale at the final focal plane of the HOWFS shall be adjustable to at least 15% of its nominal
value.
Note: This adjustability is to compensate for manufacturing defects during alignment.
Verification: Design Review & Inspection
Requirement Origin: Science (SPEC-0058, 2.0-0015, SPEC-0147)
3.3.2.12 HOWFS total length
REQ# 2.1.1-1060
The final detector plane of the HOWFS shall be no more than 1.5 meters from the HOWFS field stop.
Verification: Design Review & Inspection
Requirement Origin: Engineering (SPEC-0147)
3.3.2.13 Wavelength
REQ# 2.1.1-1065
The HOWFS shall be optimized for operation at a wavelength of 525 nm with a bandpass of 100 nm.
Note: The HOWFS is expected to use a Schott VG-9 filter or equivalent.
Verification: Design Review & Analysis
Requirement Origin: Science (SPEC-0058, 2.1.1-0010)
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3.3.3 Optical Performance
3.3.3.1 Dynamic Refocus
REQ# 2.1.1-1070
When off-pointing, the HOWFS shall use a lookup table to automatically move the objective lens to
compensate for mean field curvature.
Note: It is expected that gradual image quality degradation will occur when pointing off-axis. Dynamic
refocus will compensate for much of the image degradation but the Strehl requirement is only specified
on-axis.
Verification: Design Review, Analysis & Test
Requirement Origin: Science (SPEC-0058, 2.0-0015)
3.3.3.2 Pupil Distortion
REQ# 2.1.1-1075
Maximum distortion between the M10 pupil and the pupil at the HOWFS lenslet array shall be less than
5% of a HOWFS subaperture.
Verification: Design Review, Analysis & Test
Requirement Origin: Science (SPEC-0058, 2.1.1-0015)
3.3.3.3 Image Distortion
REQ# 2.1.1-1080
Maximum distortion between the lenslet array focal plane and the detector focal plane shall be less than
11.5 microns (one pixel).
Verification: Design Review & Analysis
Requirement Origin: Science (SPEC-0058, 2.1.1-0015)
3.3.3.4 Image Quality over central FOV
REQ# 2.1.1-1085
As designed, mean Strehl over the on-axis 10 arcsecond field of view shall be greater than 0.96 when
measured at the HOWFS field stop.
Verification: Design Review, Analysis
Requirement Origin:Science (SPEC-0058, 2.0-0015), Engineering (SPEC-0147)
3.3.3.5 HOWFS Lens Manufacturing Tolerances
REQ# 2.1.1-1090
Including manufacturing error, the final mean Strehl in every subaperture shall be greater than or equal to
0.90 over the on-axis 10 arcsecond HOWFS field of view.
Verification: Design Review, Analysis & Test
Requirement Origin: Engineering (SPEC-0058, 2.0-0015), Engineering (SPEC-0147)
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3.3.4 HOWFS Field steering mirror
REQ# 2.1.1-1095
Verification: Design Review, Analysis & Test
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1085)
3.3.5 Lenses
The HOAO lenses shall have properties within the tolerances specified in the lens drawings below
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3.3.5.1 Objective lens
REQ# 2.1.1-1100
Verification: Design Review, Analysis & Test
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1085)
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3.3.5.2 Pupil lens, element #1
REQ# 2.1.1-1105
Verification: Design Review, Analysis & Test
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1090)
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3.3.5.3 Pupil lens, element #2
REQ# 2.1.1-1110
Verification: Design Review, Analysis & Test
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1090)
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3.3.5.4 Pupil lens, element #3
REQ# 2.1.1-1115
Verification: Design Review, Analysis & Test
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1090)
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3.3.5.5 Relay lens 1, element #1
REQ# 2.1.1-1120
Verification: Design Review, Analysis & Test
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1090)
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3.3.5.6 Relay lens 1, element #2
REQ# 2.1.1-1125
Verification: Design Review, Analysis & Test
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1090)
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3.3.5.7 Relay lens 1, element #3
REQ# 2.1.1-1130
Verification: Design Review, Analysis & Test
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1090)
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3.3.5.8 Relay lens 2, element #1
REQ# 2.1.1-1135
Verification: Design Review, Analysis & Test
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1090)
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3.3.5.9 Relay lens 2, element #2
REQ# 2.1.1-1140
Verification: Design Review, Analysis & Test
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1090)
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 19 of 73
3.3.5.10 Relay lens 2, element #3
REQ# 2.1.1-1145
Verification: Design Review, Analysis & Test
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1090)
3.3.6 Microlens array
3.3.6.1 Array dimensions
REQ# 2.1.1-1150
The HOWFS microlens array shall have a clear aperture that is a minimum of 21.5 mm in diameter and
contains at least 43 complete subapertures across its diameter. The array shall be 1.5 0.1 mm thick.
Verification: Design Review & Inspection
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1020)
3.3.6.2 Focal length
REQ# 2.1.1-1155
All microlenses within the clear aperture of the HOWFS microlens array shall have focal length equal to
56 0.5 mm.
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 20 of 73
Verification: Design Review & Inspection
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1090)
3.3.6.3 Pitch
REQ# 2.1.1-1160
The HOWFS microlens array shall consist of square microlenses with lateral dimensions equal to 0.500
0.005 mm.
Verification: Design Review & Inspection
Requirement Origin: Engineering (SPEC-0147)
3.3.6.4 Optical quality
REQ# 2.1.1-1165
Each microlens within the clear aperture of the HOWFS microlens array shall introduce a maximum of
/10 P-V wavefront distortion @ = 633 nm.
Verification: Design Review & Test
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1090)
3.4 NCP Wavefront Sensor
REQ# 2.1.1-1170
The NCP wavefront sensor shall consist of an interferometer, beam expansion optics, a reflective sphere
at the GOS, a stabilized laser, and a reference flat. The NCP wavefront sensor shall be able to be inserted
and removed without perturbing any DKIST optics.
Verification: Design Review
Requirement Origin: Science (SPEC-0058, 2.0-0015; SPEC-0009, Case1a)
3.4.1 Beam expansion optics
REQ# 2.1.1-1175
The NCP wavefront sensor beam expansion optics shall be insertable into the optical path of the science
light just past BS1. The NCP wavefront sensor shall be capable of measuring the wavefront over the
diameter of the full telescope pupil at that point. The beam expansion optics shall add less than 20 nm rms
wavefront aberration to the interferometer measurement and any aberrations shall be known and
repeatable to within 5 nm rms wavefront.
Note: The beam exiting BS1 is approximately 222 mm in diameter.
Verification: Design Review& Test
Requirement Origin: Engineering (SPEC-0147)
3.4.2 PA&C reflective sphere
REQ# 2.1.1-1185
The PA&C shall provide a reflective sphere as a selectable target at the Gregorian (second) focus of the
telescope. The sphere shall be positioned at the center of the telescope FoV, have a surface figure that
deviates from a perfect sphere by less than 20 nm rms over the surface illuminated by the laser source.
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 21 of 73
Note: Further requirements for the reflective sphere, including mechanical drawings, are in the PA&C
DRD.
Verification: Design Review& Test
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1170)
3.4.3 NCP reference flat
REQ# 2.1.1-1190
The NCP wavefront sensor shall have a reference flat that serves as an absolute wavefront reference. This
flat shall have a maximum deviation from flatness of 7.0 nm rms wavefront (3.5 nm rms surface figure).
Note: This requirement is the equivalent of a /20 flat assuming = 632.8 nm
Verification: Design Review& Test
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1170)
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 22 of 73
4. HOAO Mechanical Requirements
This section contains the requirements for mechanical stages, mounts, motors, and other HOAO
mechanisms. Requirements in this section can be traced through the HOAO compliance matrix to their
justifications in the CDD or higher-level documents.
4.1 M5 Assembly
4.1.1 Mount positioning: resolution
REQ# 2.1.1-2000
The mount for the M5 Assembly shall allow the mirror surface to be manually adjustable to within the
following resolutions:
x translation: 0.5 mm
y translation: 0.5 mm
z translation: 0.5 mm
x-tilt: 5 arcseconds (24.2 microradians)
y-tilt: 5 arcseconds (24.2 microradians)
Verification: Design Review& Test
Requirement Origin: Engineering (SPEC-0147)
4.1.2 M5 dummy
REQ# 2.1.1-2005
The M5 FTT module and mirror shall be replaceable by a “dummy” mirror and module in order to allow
testing or repair of the M5 FTT mirror and/or module. The dummy mirror shall meet all non-dynamic
requirements of the M5 mirror as described in SPEC-0109. The M5 dummy module shall be a static
mount that meets all requirements in SPEC-0068 except those that deal with dynamic motion or
adjustability.
Verification: Design Review& Test
Requirement Origin: Engineering (SPEC-0147)
4.1.3 Uniformity between M5 Assembly and M5 dummy
REQ# 2.1.1-2010
When exchanging the M5 assembly with the M5 dummy or vice-versa, any resulting misalignment of the
optical surface shall be less than the following:
x translation: 1 mm
y translation: 1 mm
z translation: 1.5 mm
x-tilt: 20 arcseconds (97.0 microradians)
y-tilt: 20 arcseconds (97.0 microradians)
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 23 of 73
Note: Manual realignment is allowed to achieve this requirement, however, any necessary manual
alignment must be easily done without sunlight and require less than 30 minutes to perform.
Verification: Design Review& Test
Requirement Origin: Engineering (SPEC-0147)
4.1.4 Mechanical Performance
M5 module mechanical performance requirements are contained in SPEC-0068. A full compliance matrix
is contained in the M5 assembly contract documents.
4.2 DM Assembly
4.2.1 M10 dummy
REQ# 2.1.1-2015
The M10 assembly shall be replaceable by a “dummy” mirror in order to allow testing or repair. The
dummy mirror shall meet all non-dynamic requirements of the DM as described in SPEC-0111.
Verification: Design Review& Test
Requirement Origin: Engineering (SPEC-0147)
4.2.2 Uniformity between M10 Assembly and M10 dummy
REQ# 2.1.1-2020
When exchanging the M10 assembly with the M10 dummy or vice-versa, any resulting misalignment of
the optical surface shall be less than the following:
x translation: 1 mm
y translation: 1 mm
z translation: 1.5 mm
x-tilt: 20 arcseconds (97.0 microradians)
y-tilt: 20 arcseconds (97.0 microradians)
Note: Manual realignment is allowed to achieve this requirement, however, any necessary manual
alignment must be easily done without sunlight and require less than 30 minutes to perform.
Verification: Design Review& Test
Requirement Origin: Engineering (SPEC-0147)
4.2.3 Mechanical Performance
M10 assembly mechanical performance requirements are contained in SPEC-0111. A full compliance
matrix is contained in the M10 FDR documentation.
4.3 HOWFS Stages and Mechanisms
4.3.1 Locking mechanisms
REQ# 2.1.1-2021
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 24 of 73
All manually-adjustable HOWFS stages and mechanisms shall have locking mechanisms that allow them
to be manually locked in place. Engaging the locking mechanism shall not change the position of the
optic by more than the mechanism’s repeatability requirement.
Verification: Design Review& Test
Requirement Origin: Operations (SPEC-0129, 4.3), Engineering (SPEC-0147)
4.3.2 Field Steering mirror
4.3.2.1 Field Steering mirror: automation
REQ# 2.1.1-2025
The HOWFS field steering mirror shall be motorized so that it can be automatically controlled in α and β
rotation.
Verification: Design Review
Requirement Origin: Science (SPEC-0058, 2.1.1-0125, 2.1.1-0070)
4.3.2.2 Field Steering mirror: automated positioning
REQ# 2.1.1-2030
The HOWFS field steering mirror assembly shall have a minimum resolution of 1 arcseconds (4.8 µrad)
in α and β rotation, a minimum accuracy of 10 arcseconds (48 µrad), and repeatability to within 2
arcseconds (9.7 µrad). The HOWFS field steering mirror shall also have a range of at least 1.0 degrees
in α and β rotation. The α and β rotation velocity shall be greater than or equal to 5 degrees per second in
each axis.
Verification: Design Review & Test
Requirement Origin: Science (SPEC-0058, 2.1.1-0125), Engineering (SPEC-0147)
4.3.3 Objective lens assembly
4.3.3.1 Objective lens assembly: automation
REQ# 2.1.1-2035
The HOWFS objective lens assembly shall be motorized so that it can be automatically controlled in z
translation for focus adjustment.
Verification: Design Review
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1070)
4.3.3.2 Objective lens assembly: automated positioning
REQ# 2.1.1-2040
The HOWFS objective lens assembly shall have a resolution of less than or equal to 5 µm, accuracy of
within 25 µm, and repeatability to within 10 µm in z-translation. Its range in z-translation shall be greater
than 20 mm. The z-translation velocity of the objective lens assembly shall be greater than or equal to 10
mm per second.
Verification: Design Review & Test
Requirement Origin: Engineering (SPEC-0147)
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 25 of 73
4.3.4 Field stop mount assembly
4.3.4.1 Field stop mount assembly: automation
REQ# 2.1.1-2045
The HOWFS field stop mount assembly shall be motorized so that it can be remotely commanded to
insert a field stop, dark slide or pinhole at the focal plane of the objective lens.
Verification: Design Review
Requirement Origin: Operations (SPEC-0129, 4.2.3, 4.3.1)
4.3.4.2 Field stop mount assembly: field stop size and adjustability
REQ# 2.1.1-2050
The HOWFS field stop shall be a square stop centered on the optical axis with a default size of 3.142
0.157 mm per side and be adjustable to, at minimum, 15% from the default size.
Verification: Design Review & Test
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1025)
4.3.4.3 Field stop mount assembly: pinhole size
REQ# 2.1.1-2055
The HOWFS field stop mount assembly pinhole shall be a circular hole with diameter equal to 0.500
0.050 mm.
Verification: Design Review & Test
Requirement Origin: Operations (SPEC-0129, 4.2.3)
4.3.4.4 Field stop mount assembly: pinhole positioning
REQ# 2.1.1-2060
The HOWFS field stop mount assembly pinhole mechanism shall have a y-translation resolution of 25
µm with a repeatability of 25 µm and an accuracy of 50 µm. It shall have a minimum range of 10 mm.
Note: The minimum range requirement ensures that the assembly can be out of the beam during normal
operation, insert the pinhole at the center of the field for calibration, and block the beam entirely for dark
calibration.
Verification: Design Review & Test
Requirement Origin: Engineering (SPEC-0147)
4.3.4.5 Field stop mount assembly: manual positioning
REQ# 2.1.1-2065
The HOWFS field stop mount assembly shall be manually adjustable in x and y translation with an
adjustment resolution of 100 µm and a minimum range of 2 mm in each axis. The HOWFS field stop
mount assembly shall also be adjustable in γ rotation with resolution of 30 arcseconds and a minimum
range of 2 degrees.
Verification: Design Review & Inspection
Requirement Origin: Operations (SPEC-0129, 4.3.7.2)
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 26 of 73
4.3.5 Pupil lens mount assembly
4.3.5.1 Pupil lens mount assembly: manual positioning in x and y
REQ# 2.1.1-2070
The HOWFS pupil lens mount assembly shall be manually adjustable in x and y translation with position
resolution of 5 µm and a minimum range 1.0 mm in each axis.
Verification: Design Review & Inspection
Requirement Origin: Engineering (SPEC-0147)
4.3.5.2 Pupil lens mount assembly: manual positioning in z
REQ# 2.1.1-2075
The HOWFS pupil lens mount assembly shall be manually adjustable in z translation with position
resolution of 5 µm and a minimum range of 40 mm.
Verification: Design Review & Inspection
Requirement Origin: Engineering (SPEC-0147)
4.3.5.3 Pupil lens mount assembly: lens element adjustability
REQ# 2.1.1-2080
Each of the three lens elements of the HOWFS pupil lens shall be manually adjustable in x, y, and z
translation and α and β rotation. X and y translation adjustments shall have a position resolution of 5
µm and a minimum range of 1 mm. Z translation adjustments shall have a position resolution of 5 µm
and adjustment ranges that allow the pupil lens assembly to be configured for any numerical aperture
between 0.0266 and 0.0360, as shown in Table 1. Rotation adjustments in α and β shall have a position
resolution of 10 arcseconds (48.5 µrad) and a minimum range of 5arcminutes (1.45 mrad).
Table 1: Airgap values for full range of pupil lens adjustment
Numerical Aperture 0.0266 0.0313 0.0360
Airgap L1 to L2 (mm) 4.28 27.06 43.07
Airgap L2 to L3 (mm) 43.96 30.86 3.89
Verification: Design Review & Inspection
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1035)
4.3.6 Lenslet array mount assembly
4.3.6.1 Lenslet array mount assembly: automation
REQ# 2.1.1-2085
The HOWFS lenslet array mount assembly shall be motorized so that it can be remotely commanded in x
and y translation.
Verification: Design Review
Requirement Origin: Science (SPEC-0058, 2.1.1-0110)
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 27 of 73
4.3.6.2 Lenslet array mount assembly: automated positioning
REQ# 2.1.1-2090
The HOWFS lenslet array mount assembly shall have maximum x and y-axis resolution of 1 µm with
maximum repeatability of 1 µm and accuracy of 5 µm. Its range in x and y translation shall be a minimum
of 1 mm. The x and y translation velocities of the lenslet array mount assembly shall be a minimum of 1
mm per second.
Verification: Design Review & Test
Requirement Origin: Science (SPEC-0058, 2.1.1-0110), Operations (SPEC-0129, 4.3.7.5)
4.3.6.3 Lenslet array mount assembly: manual positioning
REQ# 2.1.1-2095
The HOWFS lenslet array mount assembly shall be manually adjustable in γ-rotation with a maximum
position resolution of 22 arcseconds and a minimum range of 4 degrees.
Verification: Design Review & Inspection
Requirement Origin: Science (SPEC-0058, 2.1.1-0110)
4.3.7 Relay lens #1 mount assembly
4.3.7.1 Relay lens #1 mount assembly: automation
REQ# 2.1.1-2100
The HOWFS relay lens #1 mount assembly shall be motorized so that it can be remotely commanded in z
translation.
Verification: Design Review
Requirement Origin: Engineering (SPEC-0147)
4.3.7.2 Relay lens #1 mount assembly: automated positioning
REQ# 2.1.1-2105
The HOWFS relay lens #1 mount assembly shall have maximum z-translation resolution of 5 µm with
maximum repeatability of 10 µm and accuracy of 10 µm. Its range in z translation shall be a minimum of
2 mm. The z-translation velocity of the mount assembly shall be minimum 0.2 mm per second.
Verification: Design Review & Test
Requirement Origin: Engineering (SPEC-0147)
4.3.7.3 Relay lens #1 mount assembly: manual positioning
REQ# 2.1.1-2110
The HOWFS relay lens #1 mount assembly shall be manually adjustable in x and y translation with
minimum resolution of 10 µm and minimum range 1 mm.
Verification: Design Review & Inspection
Requirement Origin: Engineering (SPEC-0147)
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 28 of 73
4.3.8 Relay lens #2 mount assembly
4.3.8.1 Relay lens #2 mount assembly: automation
REQ# 2.1.1-2115
The HOWFS relay lens #2 mount assembly shall be motorized so that it can be remotely commanded in z
translation.
Verification: Design Review
Requirement Origin: Engineering (SPEC-0147)
4.3.8.2 Relay lens #2 mount assembly: automated positioning
REQ# 2.1.1-2120
The HOWFS relay lens #2 mount assembly shall have maximum z-translation resolution of 5 µm with
maximum repeatability of 10 µm and accuracy of 10 µm. Its range in z translation shall be a minimum of
20 mm. The z-translation velocity of the mount assembly shall be a minimum of 0.2 mm per second.
Verification: Design Review & Test
Requirement Origin: Engineering (SPEC-0147)
4.3.8.3 Relay lens #2 mount assembly: manual positioning
REQ# 2.1.1-2125
The HOWFS relay lens #2 mount assembly shall be manually adjustable in x and y translation with
minimum resolution of 10 µm and minimum range 1 mm.
Verification: Design Review & Inspection
Requirement Origin: Engineering (SPEC-0147)
4.3.8.4 Relay lens #2 mount assembly: lens element adjustability
REQ# 2.1.1-2130
Each of the three lens elements of the HOWFS relay lens #2 shall be manually adjustable in x, y, and z
translation and α and β rotation. X and y translation adjustments shall have a position resolution of 10
µm and a minimum range of 1 mm. Z translation adjustments shall have a position resolution of 5
µm and adjustment ranges that allow the pupil lens assembly to be configured for any magnification
between -0.391 and -0.529, as shown in Table 2. Rotation adjustments in α and β shall have a position
resolution of 20 arcseconds (87.0 µrad) and a minimum range of 5arcminutes (1.45 mrad).
Table 2: Airgap values for full range of plate scale adjustments
Magnification -0.391 -0.46 -0.529
Airgap T2 L1 to T2 L2 (mm) 6.15 3.30 2.48
Airgap T2 L2 to T2 L3 (mm) 5.03 4.76 4.22
Verification: Design Review & Inspection
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1055)
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 29 of 73
4.3.9 Camera mount assembly
4.3.9.1 Camera mount assembly: automation
REQ# 2.1.1-2135
The HOWFS camera mount assembly shall be motorized so that it can be remotely commanded in x, y,
and z translation. When moving in z-translation, the two relay lenses and the filter shall move with the
camera.
Verification: Design Review
Requirement Origin: Science (SPEC-0058, 2.1.1-0110), Engineering (SPEC-0146, 2.1.1-1010)
4.3.9.2 Camera mount assembly: automated positioning
REQ# 2.1.1-2140
The HOWFS camera mount assembly shall have x and y translation resolution of 10 µm or less with a
repeatability of 20 µm and an accuracy of 20 µm. Its range in x and y translation shall be greater than 1
mm in each axis. Its z translation resolution shall be maximum 5 µm with maximum repeatability of 10
µm and maximum accuracy of 10 µm. Its minimum range in z translation shall 100 mm. Minimum x and
y translation velocities of the camera mount assembly shall be 1 mm per second in each axis. Minimum z
translation velocity of the camera mount assembly shall be 25 mm per second.
Verification: Design Review & Test
Requirement Origin: Engineering (SPEC-0147)
4.4 HOWFS Optics mount stability
REQ# 2.1.1-2145
All HOWFS optical elements shall be mounted so that the total optical surface error and centering error
meet requirements shown in Table 3 when subjected to a VC-B vibration spectrum, a standardized
generic vibration spectrum with max level equal to 25 µm per second rms[1].
Table 3: Mounting requirements for HOWFS optics
Optic Surface error,
defocus only
(nm P-V)
Surface error,
focus removed
(nm rms)
Centering Error
(um)
Field Steering Mirror 25.32 25.32 N/A
Objective Lens (triplet) 949.5 24.80 250
Pupil lens, element #1 949.5 31.65 25
Pupil lens, element #2 949.5 31.65 25
Pupil lens, element #3 949.5 31.65 25
Microlens array 949.5 63.30 25
Relay lens #1, element #1 949.5 63.30 50
Relay lens #1, element #2 949.5 63.30 50
Relay lens #1, element #3 949.5 63.30 50
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 30 of 73
Relay lens #2, element #1 949.5 63.30 40
Relay lens #2, element #2 949.5 63.30 35
Relay lens #2, element #3 949.5 63.30 40
Verification: Design Review & Analysis
Requirement Origin: Science (SPEC-0058, 2.1-0015; SPEC-0009)
4.5 HOWFS Camera
4.5.1 Format
REQ# 2.1.1-2150
The HOWFS camera shall have a minimum 860 x 860 pixel area in which all pixels meet noise, linearity,
and well depth requirements.
Verification: Design Review & Test
Requirement Origin: Science (SPEC-0058, 2.1.1-0025)
4.5.2 Pixel size
REQ# 2.1.1-2155
The HOWFS camera shall have 11.5 x 11.5 0.05 micron square pixels.
Verification: Design Review & Inspection
Requirement Origin: Engineering (SPEC-0147)
4.5.3 Quantum efficiency
REQ# 2.1.1-2160
The HOWFS camera shall have a quantum efficiency of greater than 0.22 over the wavelengths specified
for HOWFS performance (475-575 nm).
Verification: Design Review & Test
Requirement Origin: Engineering (SPEC-0147)
4.5.4 Fill factor
REQ# 2.1.1-2165
The HOWFS camera shall have an optical fill factor of greater than or equal to 60%.
Verification: Design Review
Requirement Origin: Engineering (SPEC-0147)
4.5.5 Full Well
REQ# 2.1.1-2170
The HOWFS camera shall have a minimum linear well depth of 30,000 electrons per pixel.
Verification: Design Review, Analysis, & Test
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 31 of 73
Requirement Origin: Science (SPEC-0058, 2.1.1-0025)
4.5.6 Linearity
REQ# 2.1.1-2175
Pixels of the HOWFS camera shall have a response that is linear to within 2% for a range greater than or
equal to the minimum required full well depth.
Verification: Design Review, Analysis, & Test
Requirement Origin: Science (SPEC-0058, 2.1.1-0025)
4.5.7 Artifacts
REQ# 2.1.1-2180
Any time variant noise or image artifacts shall cause a maximum of 3 nm rms wavefront reconstruction
error.
Verification: Design Review, Analysis, & Test
Requirement Origin: Science (SPEC-0058, 2.1.1-0025)
4.5.8 Frame Rate
REQ# 2.1.1-2185
The HOWFS camera shall be able to read out an 860 x 860 pixel region at a minimum rate of 2 kHz.
Verification: Design Review, Analysis, & Test
Requirement Origin: Science (SPEC-0058, 2.0-0015; SPEC-0009 Case 1a)
4.5.9 Flexible Integration time
REQ# 2.1.1-2190
The HOWFS camera exposure time shall be adjustable independent of the frame rate setting.
Verification: Design Review & Inspection
Requirement Origin: Engineering (SPEC-0147)
4.5.10 Read Noise
REQ# 2.1.1-2195
The HOWFS camera shall have a maximum of 30 e- rms read noise per frame.
Verification: Design Review, Analysis, & Test
Requirement Origin: Science (SPEC-0058, 2.1.1-0025)
4.5.11 Internal Noise
REQ# 2.1.1-2200
When imaging at greater than 50% of the linear well depth, total measurable image noise shall be a
maximum of 110% of the expected photon noise.
Verification: Design Review, Analysis, & Test
Requirement Origin: Science (SPEC-0058, 2.1.1-0025)
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 32 of 73
4.5.12 Bias Frame Stability
REQ# 2.1.1-2205
The HOWFS camera bias frame shall be stable to within 1 DN rms over a period of four hours.
Verification: Design Review, Analysis, & Test
Requirement Origin: Operations (SPEC-0129, 4.3.1)
4.5.13 Pixel Gain Stability
REQ# 2.1.1-2210
The camera gain correction shall be stable to 0.5% residual rms contrast over a period of four hours. Rms
contrast is defined as the standard deviation of the signal divided by the mean signal.
Verification: Design Review, Analysis, & Test
Requirement Origin: Science (SPEC-0058, 2.1.1-0070), Operations (SPEC-0129, 4.3.2)
4.5.14 Digitization
REQ# 2.1.1-2215
The HOWFS camera shall have greyscale resolution of 10-bit or greater.
Verification: Design Review & Inspection
Requirement Origin: Science (SPEC-0058 , 2.1.1-0025)
4.5.15 Faint Image Tracking
REQ# 2.1.1-2220
The HOWFS camera shall be able to track 1.5% rms contrast targets in a controlled laboratory
experiment.
Verification: Design Review, Analysis, & Test
Requirement Origin: Science (SPEC-0058, 2.1.1-0025)
4.5.16 Granulation tracking
REQ# 2.1.1-2225
The HOWFS camera shall be able to track solar granulation in good seeing conditions.
Note: In good seeing, supaperture images of solar granulation images have rms image contrast values of
approximately 1.5-2.0%.
Verification: Design Review, Analysis, & Test
Requirement Origin: Science (SPEC-0058, 2.1.1-0025)
4.5.17 Streaming readout
REQ# 2.1.1-2230
The HOWFS camera shall be capable of streaming data, in real time, to the HOAO RTC.
Verification: Design Review & Inspection
Requirement Origin: Engineering (SPEC-0147)
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 33 of 73
4.5.18 Read latency
REQ# 2.1.1-2235
The latency between the end of an exposure and the beginning of RTC data processing shall be 20
microseconds or less.
Verification: Design Review, Analysis, & Test
Requirement Origin: Science (SPEC-0058, 2.0-0015; SPEC-0009, Case1a)
4.5.19 Full-frame read time
REQ# 2.1.1-2240
The HOWFS camera shall be capable of copying a full 860 x 860 pixel image into the real-time system
within 500 microseconds from the end of the exposure.
Verification: Design Review, Analysis, & Test
Requirement Origin: Science (SPEC-0058, 2.0-0015; SPEC-0009, Case1a)
4.5.20 Simultaneous readout
REQ# 2.1.1-2245
The HOWFS camera shall be capable of taking an exposure while reading out the previous image.
Verification: Design Review & Inspection
Requirement Origin: Engineering (SPEC-0147)
4.5.21 Power dissipation
REQ# 2.1.1-2250
The HOWFS camera shall dissipate less than 20 W of heat into the coudé environment during operation.
Verification: Design Review & Test
Requirement Origin: Environmental (SPEC-0063, 4.4a)
4.5.22 Heat management
REQ# 2.1.1-2255
Any surfaces of the HOWFS camera that interact directly with the surrounding coudé environment shall
be cooled to within +1.5/-3.0 C of the ambient temperature.
Verification: Design Review & Test
Requirement Origin: Environmental (SPEC-0063, 4.4b)
4.6 HOAO calibration sources
4.6.1 HOAO GOS pinhole
REQ# 2.1.1-2260
The PA&C assembly shall contain a pinhole sized for the HOAO, hereafter referred to as the HOAO GOS
pinhole. The HOAO pinhole and LOWFS pinhole may be combined into a single WFS GOS pinhole,
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 34 of 73
provided the WFS GOS pinhole meets all requirements for both the HOAO GOS pinhole and the LOWFS
GOS pinhole.
Verification: Design Review
Requirement Origin: Operations (SPEC-0129, 4.2.1)
4.6.1.1 HOAO GOS pinhole size
REQ# 2.1.1-2265
The HOAO GOS pinhole shall provide a spot on the HOAO that is 3-6 pixels in diameter
Note: The HOAO pixel scale is 0.5 arcseconds /pixel
Verification: Design Review & Test
Requirement Origin: Operations (SPEC-0129, 4.2.1)
4.6.1.2 HOAO GOS pinhole shape
REQ# 2.1.1-2270
The HOAO GOS pinhole shall deviate from a perfect circle by a maximum of 5% of its diameter.
Verification: Design Review & Test
Requirement Origin: Operations (SPEC-0129, 4.2.1)
4.6.1.3 HOAO GOS pinhole stability
REQ# 2.1.1-2275
The HOAO GOS pinhole shall be stable to within 0.05 arcseconds in the x-y plane and to within 100
microns along the z-axis over any 12 minute window of time.
Verification: Design Review & Test
Requirement Origin: Operations (SPEC-0129, 4.3)
4.6.1.4 HOAO GOS pinhole accuracy
REQ# 2.1.1-2280
The HOAO GOS pinhole shall match the position of the GOS inverse pinhole to within 0.15 arcseconds.
Verification: Design Review & Test
Requirement Origin: Operations (SPEC-0129, 4.3)
4.6.1.5 HOAO GOS pinhole repeatability
REQ# 2.1.1-2285
The HOAO GOS pinhole shall have a minimum positioning repeatability of 0.05 arcseconds.
Verification: Design Review & Test
Requirement Origin: Operations (SPEC-0129, 4.3)
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 35 of 73
4.6.2 GOS calibration lamp
4.6.2.1 GOS calibration lamp power
REQ# 2.1.1-2290
The PA&C assembly shall contain a calibration lamp which emits a minimum of 3.53 x 10-5 Watts per
square arcsecond, measured as emitted power integrated between 475 and 575 nm wavelengths.
Verification: Design Review, Test
Requirement Origin: Operations (SPEC-0129, 4.2.8), Engineering (SPEC-0147)
4.6.3 GOS reflective sphere
REQ# 2.1.1-2300
The PA&C assembly shall contain a reflective sphere target that can be used in the sample arm of the
HOAO NCP interferometer.
Note: Dimensions of the GOS reflective sphere are shown in DKIST project drawing ATST-DWG-0309.
Verification: Design Review
Requirement Origin: Engineering (SPEC-0146, 2.1.1-1185)
4.6.3.1 GOS reflective sphere mounting
REQ# 2.1.1-2305
The GOS reflective sphere shall be mounted so that the reflective sphere is facing optically downstream,
with the sphere centered on the gut ray of the telescope and the base perpendicular to the gut ray of the
telescope. All light between 300 and 1000 nm from upstream of the GOS image plane will be blocked to a
minimum level of 99.999%.
Verification: Design Review
Requirement Origin: Engineering (SPEC-0147)
4.6.3.2 GOS reflective sphere perpendicularity
REQ# 2.1.1-2310
The GOS reflective sphere shall be mounted so that the base of the sphere mount is perpendicular to the
gut ray of the telescope to within 0.1 degrees at the GOS focal plane.
Verification: Design Review
Requirement Origin: Engineering (SPEC-0147)
4.6.3.3 GOS reflective sphere positioning accuracy
REQ# 2.1.1-2315
The center of the GOS reflective sphere shall match the optical center of mass of the GOS inverse pinhole
to within 12.7 microns over any 12-minute period of time.
Verification: Design Review
Requirement Origin: Engineering (SPEC-0147)
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 36 of 73
5. HOAO Algorithm Functionality REQUIREMENTS
5.1 Extract multiple Regions of Interest from Full Frame
REQ# 2.1.1-3000
The HOAO shall be capable of extracting multiple regions of interest (ROI), each corresponding to a
HOWFS subaperture image, from a full HOWFS camera frame.
Verification: Design Review, Test
Origin: Engineering
5.2 Dark Calibration
REQ# 2.1.1-3005
The HOAO shall be capable of computing an image suitable for correction of the pixel offset value in the
acquired subfield data. It shall have the following functionality:
capability to interpret the HOAO camera configuration to ascertain relevant image information
such as date/time, number of frames, number of pixels, camera & software ROI, etc
capability to ingest all HOAO camera data corresponding to the WFC dark calibration
capability to generate a set of K Dark Calibration Images ��(𝑥, 𝑦, 𝑘), k ≤ K, where K is the total
number of active HOAO subapertures, from a set of ingested dark frames, 𝐷𝑖(𝑥, 𝑦, 𝑘):
��(𝑥, 𝑦, 𝑘) =1
𝑁∑𝐷𝑖(𝑥, 𝑦, 𝑘),
𝑁
𝑖=1
∀𝑥, 𝑦, 𝑘 ≤ 𝐾
where N is the total number of frames taken in the dark calibration
capability to verify that the Dark Calibration Images contain values within the expected range of
dark values and notify the user if they do not.
capability to store the K generated Dark Calibration Images ��(𝑥, 𝑦, 𝑘), k ≤ K
Verification: Design Review, Test
Origin: Operations (SPEC-0129, 4.3.1)
5.3 Gain Calibration
REQ# 2.1.1-3010
The HOAO shall be capable of computing a set of K images suitable for correction of - among others -
image defects in the acquired data. It shall have the following functionality:
capability to interpret the HOAO camera configuration to ascertain relevant image information
such as date/time, number of frames, number of pixels, camera ROI, etc
capability to retrieve the latest relevant Dark Calibration Images (see Section 5.2) matching the
current HOAO camera configuration (number of pixels, camera and software ROI, etc)
capability to ingest all HOAO camera data corresponding to the WFC gain calibration mode
capability to generate a set of K Gain Calibration Images 𝐹(𝑥, 𝑦, 𝑘), k ≤ K, from a set of ingested
gain frames, one for each HOAO subaperture ROI, using the following procedure:
Step 1 - Averaging:
𝐹(𝑥, 𝑦, 𝑘) = ∑𝐹𝑖(𝑥, 𝑦, 𝑘) − ��(𝑥, 𝑦, 𝑘), ∀𝑥, 𝑦, 𝑘
𝑁
𝑖=1
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 37 of 73
where N is the total number of frames taken in the gain calibration
Step 2 - Normalization:
𝐺(𝑥, 𝑦, 𝑘) =1
𝑋 ∙ 𝑌(∑ 𝐹(𝑥, 𝑦, 𝑘)𝑥,𝑦
𝐹(𝑥, 𝑦, 𝑘)⁄ ), ∀𝑥, 𝑦, 𝑘
where X and Y are the total number of pixels per subaperture in the x and y directions,
respectively.
capability to store the K generated Gain Calibration Images 𝐺(𝑥, 𝑦, 𝑘), k ≤ K
Verification: Design Review, Test
Origin: Operations (SPEC-0129, 4.3.2)
5.4 Calibration of subaperture images
REQ# 2.1.1-3015
The HOAO shall be capable of calibrating the set of K HOAO subaperture images for each full HOAO
camera frame. It shall have the following functionality:
capability to interpret the HOAO camera configuration to ascertain relevant image information
such as date/time, number of frames per frameset, number of pixels, ROI, etc
capability to retrieve latest relevant Calibration Images (see Section 5.2 and 5.3) matching the
current HOAO camera settings (number of pixels, camera and software ROI, etc)
capability to compute a set of K calibrated images, 𝐶(𝑥, 𝑦, 𝑘), over the K subapertures for each
HOAO camera frame received, in the following way,
𝐶(𝑥, 𝑦, 𝑘) = (𝐼(𝑥, 𝑦, 𝑘) − ��(𝑥, 𝑦, 𝑘)) ∙ ��(𝑥, 𝑦, 𝑘), ∀(𝑥, 𝑦, 𝑘)
where 𝐼(𝑥, 𝑦, 𝑘) is the raw image for subaperture k (see above for the definitions of D and G)
capability to output the set of K calibrated images 𝐶(𝑥, 𝑦, 𝑘), ∀k ≤ K, for further internal
processing
Verification: Design Review, Test
Origin: Science (SPEC-0058, 2.1.1-0025)
5.5 Subaperture Shift Measurement
REQ# 2.1.1-3020
For each HOWFS camera frame, HOAO shall compute shifts between the reference image and all active
HOAO subaperture images using the following algorithms for cross-correlation and subpixel
interpolation.
Verification: Design Review, Test
Origin: Science (SPEC-0058, 2.1.1-0010)
5.5.1 Cross-correlation algorithm
The HOAO shall compute 2-dimensional cross-correlations between
a single reference subaperture image, 𝐶𝑟𝑒𝑓(𝑥, 𝑦) and
each of the K subaperture images in a captured HOAO camera frame, 𝐶(𝑥, 𝑦, 𝑘), k ≤ K, as
follows:
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 38 of 73
𝐶𝐶(𝑝, 𝑞, 𝑘) = ∑ ∑ 𝐶(𝑥, 𝑦, 𝑘) ∗ 𝐶𝑟𝑒𝑓(𝑥 + 𝑝, 𝑦 + 𝑞)
𝑌
𝑦=1
𝑋
𝑥=1
where K is the total number of subapertures, X and Y are the total number of pixels per subaperture in the
x and y directions, p and q are each integers on the interval [-3, 3], and * represents element by element
multiplication of arrays. The shift of Cref in this calculation is a circular shift.
The p and q indices of the location where 𝐶𝐶(𝑝, 𝑞, 𝑘) is at its maximum correspond to the integer shift
between image 𝐶(𝑥, 𝑦, 𝑘) and the reference image.
5.5.2 Computation of image displacements to subpixel accuracy
The HOAO shall be capable of computing image displacements between each of the K HOAO
subaperture images and the selected reference HOAO subaperture image to subpixel accuracy.
For this computation, the HOAO shall use the K 2-dimensional cross-correlation arrays and the following
formula:
𝑆𝑥𝑘 = (𝑥𝑚𝑎𝑥 − 1
2⁄ ) +𝐶𝐶(𝑥𝑚𝑎𝑥, 𝑦𝑚𝑎𝑥, 𝑘) − 𝐶𝐶(𝑥𝑚𝑎𝑥 − 1, 𝑦𝑚𝑎𝑥, 𝑘)
2𝐶𝐶(𝑥𝑚𝑎𝑥, 𝑦𝑚𝑎𝑥 , 𝑘) − 𝐶𝐶(𝑥𝑚𝑎𝑥 − 1, 𝑦𝑚𝑎𝑥, 𝑘) − 𝐶𝐶(𝑥𝑚𝑎𝑥 + 1, 𝑦𝑚𝑎𝑥, 𝑘)
𝑆𝑦𝑘 = (𝑦𝑚𝑎𝑥 − 1
2⁄ ) +𝐶𝐶(𝑥𝑚𝑎𝑥, 𝑦𝑚𝑎𝑥 , 𝑘) − 𝐶𝐶(𝑥𝑚𝑎𝑥, 𝑦𝑚𝑎𝑥 − 1, 𝑘)
2𝐶𝐶(𝑥𝑚𝑎𝑥, 𝑦𝑚𝑎𝑥, 𝑘) − 𝐶𝐶(𝑥𝑚𝑎𝑥 , 𝑦𝑚𝑎𝑥 − 1, 𝑘) − 𝐶𝐶(𝑥𝑚𝑎𝑥, 𝑦𝑚𝑎𝑥 + 1, 𝑘)
where 𝑥𝑚𝑎𝑥 and 𝑦𝑚𝑎𝑥 are the integer pixel positions for which 𝐶𝐶(𝑥, 𝑦, 𝑘) is maximal for a particular
k ≤ K.
5.6 Wavefront Reconstruction
REQ# 2.1.1-3025
HOAO shall be capable of wavefront reconstruction via a vector-matrix multiply that generates FTT and
DM actuator commands from wavefront sensor residual shift measurements.
𝑎𝑟𝑒𝑠 = 𝑅𝑠
where 𝑎𝑟𝑒𝑠 is a vector of DM and FTT actuator commands, s is a vector of residual x and y shift
measurements, and R is the selected reconstruction matrix.
Verification: Design Review, Test
Origin: Science (SPEC-0058, 2.1.1-0005)
5.7 PI Servo Loop
REQ# 2.1.1-3030
HOAO shall apply gains to the proportional and integral residual wavefront actuator commands produced
by wavefront reconstruction (section 5.6).
𝑎𝐷𝑀,𝑖[𝑘] = 𝐾𝑃,𝐷𝑀𝑎𝑟𝑒𝑠,𝑖 + 𝐾𝐼,𝐷𝑀 ∑ 𝛼𝐷𝑀𝑘−𝜏𝑎𝑟𝑒𝑠,𝑖[𝜏]
𝑘
𝜏=𝑘0,𝐷𝑀
, ∀𝑖 ∈ [1, 𝑁𝑎𝑐𝑡]
and
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 39 of 73
𝑎𝑇𝑇,𝑖−𝑁𝑎𝑐𝑡[𝑘] = 𝐾𝑃,𝑇𝑇𝑎𝑟𝑒𝑠,𝑖 + 𝐾𝐼,𝑇𝑇 ∑ 𝑎𝑟𝑒𝑠,𝑖[𝜏]
𝑘
𝜏=𝑘0,𝑇𝑇
, ∀𝑖 ∈ [𝑁𝑎𝑐𝑡 + 1,𝑁𝑎𝑐𝑡 + 2]
where 𝑎𝐷𝑀,𝑖[𝑘] is the ith element of the DM actuator command vector at timestep k, 𝐾𝑃,𝐷𝑀 is the
proportional gain for the DM servo loop, 𝐾𝐼,𝐷𝑀 is the integral gain for the DM servo loop, 𝛼𝐷𝑀 is the DM
leak factor, and 𝑘0,𝐷𝑀 is the timestep when the DM integrator was last reset. Similarly, 𝑎𝑇𝑇,𝑖[𝑘] is the ith
element of the FTT actuator command vector at timestep k, 𝐾𝑃,𝑇𝑇 is the proportional gain for the FTT
servo loop, 𝐾𝐼,𝑇𝑇 is the integral gain for the FTT servo loop, and 𝑘0,𝑇𝑇 is the timestep when the FTT
integrator was last reset. This notation assumes that the 𝑎𝑟𝑒𝑠 vector is ordered so that its first Nact elements
are DM actuator commands and its last two elements are FTT actuator commands.
Verification: Design Review, Test
Origin: Science (SPEC-0058, 2.1.1-0010)
5.8 Tip-Tilt Derotation
REQ# 2.1.1-3035
HOAO shall rotate the FTT actuator commands from the WFC coordinate plane to the M5 FTT
coordinate plane before sending them to the M5 FTT module.
𝑎𝑀5𝑇𝑇[k] = [cos 𝜃𝑟𝑜𝑡 −sin 𝜃𝑟𝑜𝑡
sin 𝜃𝑟𝑜𝑡 cos 𝜃𝑟𝑜𝑡] 𝑎𝑇𝑇[𝑘]
where
𝜃𝑟𝑜𝑡 = −𝜃𝑎𝑧 − 𝜃𝑐𝑜𝑢𝑑é + 𝐶𝑀5
and 𝜃𝑐𝑜𝑢𝑑é is the coudé rotation angle, 𝜃𝑎𝑧 is the azimuth rotation angle, and 𝐶𝑀5 is a constant offset to
adjust the zeropoint of the M5 rotation angle.
Verification: Design Review, Test
Origin: Engineering (SPEC-0147)
5.9 Fast Tip-Tilt Offload to Mount
REQ# 2.1.1-3040
HOAO shall offload M5 travel to the TCS if the average position of the M5 FTT module, over the user-
set offload period, exceeds the user-set offload range threshold.
In order to offload in the correct basis, the M5 FTT Module axes must be transformed into the TCS
altitude and azimuth coordinate system. This will be done in the following way,
∆𝛉mount = k ∗ 𝐑∅𝐒M5∆𝛉M5
where ∆𝛉mount = [∆θalt, ∆θaz]T is the change in altitude and azimuth angle to be sent to the TCS, 𝐒M5 is
the M5 sensitivity matrix, ∆𝛉M5 is the angular tip-tilt offload desired, and k is a gain factor used to
prevent system stability issues. 𝐑∅ is a rotation matrix that accounts for image rotation due to the altitude
angle of the telescope,
𝐑∅ = [𝐜𝐨𝐬∅ −𝐬𝐢𝐧∅𝐬𝐢𝐧∅ 𝐜𝐨𝐬 ∅
]
∅ = −θalt + C.
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 40 of 73
where θalt is the current altitude angle of the telescope and C is a constant offset determine by calibration.
Initially, 𝐒M5 will be determined by ZEMAX models of the telescope but will be updated based on
calibrations during IT&C.
Verification: Design Review, Test
Origin: Engineering (SPEC-0147)
5.10 R0 calculation
REQ# 2.1.1-3045
HOAO shall be capable of computing an estimate of the mean atmospheric r0 value over a user-defined
time period (default 1 second). The r0 estimate shall be computed by using a linear influence function
model of the DM to estimate the total atmospheric wavefront at each control-loop iteration.
Once the wavefronts have been collected over the desired time-period, they will be converted into
Karhunen-Loéve (K-L) modal coefficients. The sample variances of the K-L coefficients will be fit to the
expected Kolmogorov variance of K-L functions, using a least-squares fit, to find the value of r0 that best
fits the observed data.
The expected variance of K-L functions shall be a user-defined array which can be edited to change
which K-L functions are used for the r0 calculation.
Verification: Design Review, Test
Origin: Science (SPEC-0058, 2.1.1-0055)
5.11 Residual error calculation
REQ# 2.1.1-3050
The HOAO shall be capable of computing the mean tilt-removed rms residual wavefront error as
measured by the HOWFS over a period of one second.
The rms mean-subtracted residual wavefront error shall be computed from the array of wavefront sensor
actuator residuals.
𝛔res[𝑘] = 𝑐𝐷𝑀√��[𝑘]𝑇��[𝑘]
𝑁𝑎𝑐𝑡
with �� defined as the actuator residual error vector with the mean piston and tilt terms removed, 𝛔res[𝑘] is the rms residual wavefront shape in nanometers at timestep k, Nact is the total number of active DM
actuators, and cDM is a constant that converts actuator commands from digital numbers to nanometers
wavefront.
The HOAO shall monitor 𝛔res[𝑘] and record its mean value over one second,
𝛔res =1
𝐾∑ 𝛔res[𝑘 ∗ 𝑛𝑠𝑘𝑖𝑝]
𝐾
𝑘=1
with
𝐾 = ⌈𝑓𝐻𝑂𝐴𝑂
𝑛𝑠𝑘𝑖𝑝 + 1⌉
where fHOAO is the HOAO frame rate, nskip is the user-defined frameskip setting, and ⌈∙⌉ signifies the
ceiling function.
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 41 of 73
Verification: Design Review, Test
Origin: Operations (SPEC-0129. 5.2.1)
5.12 DM rms calculation
REQ# 2.1.1-3055
The HOAO shall be capable of computing the mean rms wavefront correction provided by the DM over
one second.
The DM mean-subtracted rms shape shall be computed from the array of DM actuator commands
immediately following servo loop application and interactuator limitation but before individual actuator
gains and offsets are applied.
𝛔DM[𝑘] = 𝑐𝐷𝑀√��DM[𝑘]𝑇��DM[𝑘]
𝑁𝑎𝑐𝑡
with ��DM defined by
��DM[𝑘] = 𝐚DM[𝑘] − 𝐚DM [𝑘]
and
𝐚DM [𝑘] =1
𝑁𝑎𝑐𝑡∑ 𝐚DM,i[𝑘]
𝑁𝑎𝑐𝑡
𝑖=1
where 𝛔DM[𝑘] is the rms wavefront shape in nanometers due to the DM at timestep k, aDM,i[k] is the ith
element of a column vector containing all DM actuator commands at timestep k, 𝐚DM [𝑘] is the mean of
aDM[k], Nact is the total number of DM actuators, and cDM is a constant that converts actuator commands
from device units to nanometers wavefront.
The HOAO shall monitor 𝛔DM[𝑘] and record its mean value over one second,
𝛔DM =1
𝐾∑ 𝛔DM[𝑘 ∗ 𝑛𝑠𝑘𝑖𝑝]
𝐾
𝑘=1
with
𝐾 = ⌈𝑓𝐻𝑂𝐴𝑂
𝑛𝑠𝑘𝑖𝑝 + 1⌉
where fHOAO is the HOAO frame rate, nskip is the user-defined frameskip setting and ⌈∙⌉ signifies the ceiling
function.
Verification: Design Review, Test
Origin: Operations (SPEC-0129. 5.2.1)
5.13 HOAO Modal Coefficient Computation from Subaperture Shifts
REQ# 2.1.1-3060
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 42 of 73
The HOAO shall be capable of computing 20 Zernike or M1 natural mode coefficients from the set of
subaperture shift measurements.
If Ts is a matrix reconstructing either Zernike or natural modes from the wavefront gradient (represented
by the measured subpixel accuracy image displacements as reported in the telemetry data), the formula to
calculate the modes shall be the matrix multiplication:
�� (𝑡) = 𝐓s𝑠 (t)
where 𝑠 = (… , 𝑠𝑥𝑘−1, 𝑠𝑦
𝑘−1, 𝑠𝑥𝑘 , 𝑠𝑦
𝑘, 𝑠𝑥𝑘+1, 𝑠𝑦
𝑘+1, … ) is the vector with the subpixel accuracy displacements
as elements.
Note: A matrix 𝐓s will be provided, but it must be possible to load different matrices 𝐓s while HOAO is
operational.
HOAO shall average the modal coefficients over a user-defined time period and shall use a CSF event to
report the average modal coefficients, along with their associated confidence coefficients (section 5.15).
Verification: Design Review, Test
Origin: Science (SPEC-0058, 2.1.1-0080)
5.14 HOAO Modal Coefficient Computation from Actuator Commands
REQ# 2.1.1-3065
The HOAO shall be capable of computing 20 Zernike or M1 natural mode coefficients from the set of
DM actuator commands.
If 𝐓act is a matrix reconstructing either Zernike or natural modes from the DM actuator commands (as
reported in the telemetry data), the formula to calculate the modes shall be the matrix multiplication:
�� (𝑡) = 𝐓act�� (𝑡)
where �� (𝑡) is a column vector of the DM actuator commands at time t.
Note: A matrix 𝐓act will be provided, but it must be possible to load different matrices 𝐓act while the
HOAO is operational.
HOAO shall average the modal coefficients over a user-defined time period and shall use a CSF event to
report the average modal coefficients, along with their associated confidence coefficients (section 5.15).
Verification: Design Review, Test
Origin: Science (SPEC-0058, 2.1.1-0075)
5.15 HOAO Modal Coefficient Confidence
REQ# 2.1.1-3070
HOAO shall calculate the confidence of each modal coefficient in sections 5.13 and 5.14 and report these
confidence values in each of the respective CSF events. The confidence of each modal coefficient is equal
to the inverse of that coefficient’s measured variance,
𝐶𝑖 =1
𝜎𝑖2
where
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 43 of 73
𝜎𝑖2 =
1
𝐾 − 1∑(𝑚𝑖[𝑘 ∗ 𝑛𝑠𝑘𝑖𝑝] − ��𝑖)
2𝐾
𝑘=1
and
��𝑖 =1
𝐾∑ 𝑚𝑖[𝑘 ∗ 𝑛𝑠𝑘𝑖𝑝]
𝐾
𝑘=1
for
𝐾 = ⌈𝑓𝐻𝑂𝐴𝑂 ∗ 𝑇𝑚𝑜𝑑𝑒
𝑛𝑠𝑘𝑖𝑝⌉
with 𝑓𝐻𝑂𝐴𝑂 equal to the HOAO frame rate, 𝑇𝑚𝑜𝑑𝑒 is the user-set averaging period for reporting the modal
coefficients, 𝑛𝑠𝑘𝑖𝑝 is the frameskip setting for the relevant modal computation, ⌈∙⌉ signifies the ceiling
function, 𝑚𝑖 is the ith modal coefficient, and 𝐶𝑖 is the confidence of the ith modal coefficient over the user-
defined time period.
If 𝜎𝑖2 ≤ 0.01 then 𝐶𝑖 = 100
Confidence will be calculated and reported in CSF events for both the modal coefficients from the shift
calculations and the modal coefficients from DM actuators. Each of the two modal coefficient
calculations will have their own independent values for 𝑇𝑚𝑜𝑑𝑒 and 𝑛𝑠𝑘𝑖𝑝.
Verification: Design Review, Test
Origin: Engineering (SPEC-0175)
5.16 DM Interactuator Voltage Limitation
REQ# 2.1.1-3075
The HOAO shall limit voltage between adjacent actuators so that commands sent to the DM drive
electronics do not over-drive adjacent actuators.
The Xinetics DM is expected to operate its actuators at voltages between 20-80V with a bias voltage of
50V. It is expected that the interactuator voltage limit will be 30V.
The interactuator limiting algorithm shall prioritize safety of the DM facesheet above all performance
concerns. The interactuator limiting algorithm shall be demonstrated in simulation to be 100% effective in
eliminating interactuator violations from a minimum of one million consecutive DM shapes created by
driving the actuators using white noise with standard deviation equal to half the interactuator limit.
Additionally, the RTC will be run while disconnected from the DM for one million cycles on pure noise
inputs and monitored to ensure that it does not generate any DM patterns that violate the interactuator
stroke limit.
Only once these tests have been successfully completed shall the DM be driven by the HOAO RTC.
Verification: Design Review, Test
Origin: Engineering (SPEC-0147)
5.17 OOB Subaperture Shift Detection
REQ# 2.1.1-3080
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 44 of 73
HOAO shall monitor the HOWFS subaperture shift measurement results in real-time for out-of-bounds
(OOB) measurements. An OOB measurement is a shift measurement that is equal to the maximum
measureable shift in any direction, before subaperture shift references are subtracted. HOAO shall record
the total number of OOB shift measurements in each HOWFS frame and report the OOB statistics as
required.
Verification: Design Review, Test
Origin: Science (SPEC-0058, 2.1.1-0040)
5.18 DM Interaction Matrix Calibration
REQ# 2.1.1-3085
HOAO shall support calibration of the DM interaction matrix using a user-provided matrix of test
patterns, V, where each ith column of the matrix, Vi, represents a vector of DM actuator commands.
To perform the calibration, HOAO shall apply each Vi to the DM and measure the resulting shifts, Si, to
construct the sensor matrix, S = [S1|S2|…]. If there are m active HOWFS subapertures, Nact DM actuators,
and Ntest total test patterns to apply then V is of dimension Nact by Ntest and S is of dimension 2m by Ntest.
It is expected that Ntest will be equal to Nact but HOAO shall be able to accommodate any value for Ntest on
the interval [Nact, 3Nact].
Note: The full matrix construction may be done by a higher level controller (WCCS) instead of at the
HOAO level, provided the time constraint can be met. In this case the only functionality required by
HOAO is the ability to accept a DM command, apply it to the DM, and return the resulting shift
measurements.
Verification: Design Review, Test
Origin: Science (SPEC-0058, 2.1.1-0045)
5.19 HOAO Automatic Gain and Reconstruction Matrix Optimization
REQ# 2.1.1-3090
HOAO shall be capable of estimating the noise in the HOAO reference subaperture and automatically
adjusting proportional and integral gains of its servo loop to minimize residual wavefront error. HOAO
shall also optimize its reconstruction matrix for current seeing conditions and measurement noise.
This shall be accomplished by maintaining a lookup table that uses the current r0 and reference
subaperture noise estimate to set the optimal servo gains and number of K-L modes reconstructed. HOAO
shall use this lookup table to update the gains and reconstruction matrix at a minimum rate of 1 Hz.
Verification: Design Review, Test
Origin: Science (SPEC-0058, 2.1.1-0060)
5.20 Mitigation of Bad Seeing or Loop Instability
REQ# 2.1.1-3095
HOAO shall be capable of automatically adjusting system parameters to compensate for poor seeing or
control loop instability. It will do so by monitoring the number of OOB subapertures and reducing the
control loop gains and number of modal basis functions reconstructed if the OOB subapertures exceed the
user-set thresholds for the DM and FTT.
Separate thresholds and gain offsets will be maintained for the DM and FTT control loops. If the HOAO
controller detects a number of OOB counts in a given frame that exceed the DM OOB threshold, it shall
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 45 of 73
increment the level of the DM gain offset. When incrementing the level of the DM gain offset, the HOAO
controller shall change the control loop gains of the DM loop such that,
𝑘𝐷𝑀,𝐼𝑚 = (1 − 𝑚𝐷𝑀 ∙ 𝑙𝐷𝑀)𝑘𝐷𝑀,𝐼
0
𝑘𝐷𝑀,𝑃𝑚 = (1 − 𝑚𝐷𝑀 ∙ 𝑙𝐷𝑀)𝑘𝐷𝑀,𝑃
0
where 𝑘𝐷𝑀,𝐼0 is the integral gain, set by either manual user input or the automated gain optimization
(depending on whether gains are set manually or automatically), 𝑚𝐷𝑀 is the level of the current DM gain
offset, 𝑙𝐷𝑀 is the DM OOB increment, and 𝑘𝐷𝑀,𝐼𝑚 is the integral gain setting for offset level 𝑚𝐷𝑀.
Similarly, 𝑘𝐷𝑀,𝑃0 is the proportional gain, set by either manual user input or the automated gain
optimization, and 𝑘𝐷𝑀,𝑃𝑚 is the proportional gain setting for offset level 𝑚𝐷𝑀.
Whenever the HOAO controller increases the level of the DM gain offset, it shall zero the DM control
loop accumulators and change the control matrix to the control matrix 𝑚 levels below the one currently
indicated by either manual user input or the automated gain optimization. If the desired reconstruction
matrix is below the lowest level matrix loaded into RTC memory or the gains reach zero then the DM
shall be disabled until the recovery criteria are met.
The FTT OOB threshold will function similarly to the DM OOB threshold. If the HOAO controller
detects a number of OOB counts in a given frame that exceed the FTT OOB threshold, it shall increment
the level of the FTT gain offset. When incrementing the level of the FTT gain offset, the HOAO
controller shall clear the FTT accumulators and change the control loop gains of the FTT loop such that,
𝑘𝐹𝑇𝑇,𝐼𝑚 = (1 − 𝑚𝐹𝑇𝑇 ∙ 𝑙𝐹𝑇𝑇)𝑘𝐹𝑇𝑇,𝐼
0
𝑘𝐹𝑇𝑇,𝑃𝑚 = (1 − 𝑚𝐹𝑇𝑇 ∙ 𝑙𝐹𝑇𝑇)𝑘𝐹𝑇𝑇,𝑃
0
where 𝑘𝐹𝑇𝑇,𝐼0 is the integral gain set by either manual user input or the automated gain optimization, 𝑚𝐹𝑇𝑇
is the level of the current FTT gain offset, 𝑙𝐹𝑇𝑇 is the FTT OOB increment, and 𝑘𝐹𝑇𝑇,𝐼𝑚 is the integral gain
setting for offset level 𝑚𝐹𝑇𝑇. Similarly, 𝑘𝐹𝑇𝑇,𝑃0 is the proportional gain set by either manual user input or
the automated gain optimization and 𝑘𝐹𝑇𝑇,𝑃𝑚 is the proportional gain setting for offset level 𝑚𝐹𝑇𝑇. If the
offset level causes the gains to reach zero then the FTT loop shall be disabled until the recovery criteria
are met.
Recovery from DM or FTT gain offsets shall be done incrementally by decreasing the offset levels
whenever the recovery criteria are met. The recovery criteria are met by observing a number of
consecutive frames equal to the user-set DM and FTT recovery thresholds.
Whenever the DM or FTT recovery periods are met, their respective offsets will be decreased by one
level. For the DM this means the loop gains will be increased and the reconstruction matrix will be
changed to the next highest number of modal basis functions. For the FTT loop, the gains will be
increased. The DM and FTT loop shall never be offset to a level less than zero, i.e. the gains and number
of modes reconstructed will never exceed those set by the user or the automated optimization process.
One of the top-level HOAO controllers, either the Real-Time Manager or Telemetry Processor, shall
monitor the status of the offsets applied to the DM gains and reconstruction matrices due to OOB count
violations. If offsets are applied continuously for longer than a user-set time period (default 3 seconds),
the HOAO health shall be set to ill. Health shall be set back to good if ten continuous seconds are
observed with no applied offsets.
Verification: Design Review, Test
Origin: Science (SPEC-0058, 2.1.1-0040), Engineering (SPEC-0147)
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 46 of 73
5.21 HOWFS Automatic exposure time adjustment
REQ# 2.1.1-3100
HOAO shall be capable of automatically adjusting the HOWFS camera exposure time based on the flux
level in a selected subaperture. When automatic exposure time adjustment is enabled, it will use the
following algorithm.
Parameters required: Minimum intensity threshold (Tmin), Maximum intensity threshold (Tmax), number of
frames between updates (nframes), current exposure time (texp), maximum exposure time based on current
frame rate (texp, max), subaperture selected for intensity monitoring (aref).
Steps:
Collect a sequence of nframes raw images from the chosen subaperture (Iraw(x,y,i) for i =[1, nframes])
and average them:
I𝑚𝑒𝑎𝑛(𝑥, 𝑦) =1
𝑛𝑓𝑟𝑎𝑚𝑒𝑠∑ 𝐼𝑟𝑎𝑤(𝑥, 𝑦, 𝑖)
𝑛𝑓𝑟𝑎𝑚𝑒𝑠
𝑖=1
Find the maximum intensity value of the mean subaperture image:
𝐼𝑚𝑎𝑥 = 𝑎𝑟𝑔𝑚𝑎𝑥{𝐼𝑚𝑒𝑎𝑛(𝑥, 𝑦)}
If Imax > Tmin and Imax < Tmax then do nothing. Else:
o Adjust exposure time
𝑡𝑒𝑥𝑝 =𝑇𝑚𝑎𝑥
𝐼𝑚𝑎𝑥∗ 𝑡𝑒𝑥𝑝
o Check that new exposure time does not exceed max exposure time
If texp > texp, max then texp = texp, max
o Set texp as HOWFS camera exposure time
The exposure time update shall happen at a maximum update rate of 1 Hz.
Verification: Design Review, Test
Origin: Science (SPEC-0058, 2.1.1-0035)
5.22 HOWFS Pupil position measurement
REQ# 2.1.1-3105
HOAO shall be capable of measuring mean intensities in edge subapertures of the HOWFS lenslet array
using the following algorithm. The subaperture intensities will be sent to the aO Engine where it will use
them to estimate the pupil position on the HOWFS lenslet array.
Parameters required: Four selected partially-illuminated subapertures (a1 = si, a2 = sj, a3 = sk, a4 = sm,
where i < j < k < m, si represents subaperture number i and subapertures are numbered in increasing order
from top left to bottom right). Number of images per measurement (nimages)
Steps:
Record initial telescope position (Altitude, Azimuth, Coude rotation)
Collect nimages raw images from each selected subaperture and find the mean intensity of each
image:
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 47 of 73
𝐼𝑚𝑒𝑎𝑛(𝑢) =1
𝑋∗𝑌∗𝑛𝑖𝑚𝑎𝑔𝑒𝑠∑ ∑ ∑ 𝑎𝑢(𝑥, 𝑦, 𝑛)𝑋
𝑥=1𝑌𝑦=1
𝑛𝑖𝑚𝑎𝑔𝑒𝑠
𝑛=1 , 𝑢 ∈ {1,2,3,4}
where X and Y are the total number of pixels in a subaperture image in the x and y directions
Record final telescope position
Report the mean subaperture intensities and initial and final telescope positions to the aO engine
Verification: Design Review, Test
Origin: Science (SPEC-0058, 2.1.2-0040)
5.23 Absolute Error after Calibration
5.23.1 Total wavefront error
REQ# 2.1.1-3110
After all calibration steps have been successfully completed, quasi-static telescope wavefront error due to
all error sources within the HOAO shall be less than or equal to the DIQ case 1 error budget allocation for
“Adaptive Optics Error”.
Verification: Design Review, Analysis, & Test
Origin: Science (SPEC-0058,2.0-0015; SPEC-0009)
5.23.2 HOAO error budget
REQ# 2.1.1-3115
The WFC team shall maintain an internal error budget that tracks all significant contributions to telescope
wavefront error due to HOAO sources. Error budget allocations shall be updated with the latest estimates
based on testing and analytic methods.
Note: The HOAO Error budget will be recorded in the HOAO CDD (SPEC-0147).
Verification: Design Review, Analysis, & Test
Origin: Engineering (SPEC-0147)
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 48 of 73
6. HOAO Software Requirements
6.1 General Requirements
6.1.1 Division of software tasks
REQ# 2.1.1-4260
The HOAO software shall be divided into three main components. One software component, the Real-
Time Manager (RTM) shall handle configuration management, scripting, CSF tasks, and other non-real-
time computations necessary for maintaining the state of the HOAO. The HOAO Real-Time Controller
(RTC) shall handle all real-time processing tasks. The HOAO telemetry processor shall ingest the raw
telemetry output from the RTC and perform the necessary computations and formatting required for the
final telemetry data products to be transmitted via the BDT.
Note: This division ensures that critical real-time computations are not interrupted by configuration and
management activities.
Verification: Design Review
Source: Engineering (SPEC-0147)
6.2 HOAO System Settings Requirements
This section contains requirements for the HOAO subsystem settings. The requirements for each setting
will include a brief description of the functionality the setting will drive, what level it can be changed at,
the range of possible values, the default value, and associated validation rules, where applicable.
System settings can be managed at two levels: user level and engineering level.
User level settings consist of those settings that are needed for setting up routine WFC operation. These
settings are available to the operator or general user. Engineering level settings are settings used during
calibration and alignment procedures or during special operations. These settings require the permission
and assistance of the WFC specialist or designee.
6.2.1 WFC mode
REQ# 2.1.1-4265
HOAO requires the WFC mode to be sent from the WCCS. This mode specifies the overall operation
mode of the WFC system.
Setting details:
Level: User
Range of Values: off, idle, calibrate, diffractionLimited, seeingLimitedOnDisk,
seeingLimitedCoronal, limbTracking
Default Value: idle
Verification: Design Review, Test
Source: Science (SPEC-0058, 2.0-0005), Operations (SPEC-0129, 3.1.1)
6.2.2 r0 Calculation Period
REQ# 2.1.1-4269
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 49 of 73
HOAO shall allow the WFC specialist to set the period of time over which r0 is calculated.
Setting details:
Level: Engineering
Format: float
Range of Values: [0, 60] seconds
Default Value: 1
Verification: Design Review, Test
Source: Science (SPEC-0058, 2.1.1-0055), Engineering (SPEC-0129, 5.2.1)
6.2.3 r0 Calculation Frameskip
REQ# 2.1.1-4270
HOAO shall allow the WFC specialist to set the frameskip parameter for averaging r0 calculations.
Note: When calculating the data products used in estimating r0, HOAO will skip this many frames
between measurements.
Setting details:
Level: Engineering
Format: integer
Range of Values: 0-400
Default Value: TBD
Verification: Design Review, Test
Source: Engineering (SPEC-0147)
6.2.4 aO Engine Event Period
REQ# 2.1.1-4275
HOAO shall allow the WFC specialist to set the period of time for averaging low-order DM corrections
and WFS measurements for offload to the aO engine. The period, HOAO frame rate, and frameskip
settings determine the number of frames averaged for each event that is sent.
Setting details:
Level: Engineering
Format: float
Range of Values: 1-600 seconds
Default Value: 45
Verification: Design Review, Test
Source: Engineering (SPEC-0129)
6.2.5 aO Engine Event Basis
REQ# 2.1.1-4280
HOAO shall allow the WFC specialist to select the modal basis used for the modal coefficients sent to the
aO engine.
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 50 of 73
Note: In operational use cases, the WFC modal basis is controlled by the WCCS. Manual setting of the
WFC modal basis at the subsystem level is for debugging and engineering operations only.
Setting details:
Level: Engineering
Format: string
Range of Values: Zernike, mirrorModes
Default Value: Zernike
Verification: Design Review, Test
Source: Operations (SPEC-0129)
6.2.6 aO Engine Event Frameskip
REQ# 2.1.1-4285
HOAO shall allow the WFC specialist to set the number of frames to skip between updates of DM and
WFS offload measurements.
Setting details:
Level: Engineering
Format: integer
Range of Values: [0, 2000]
Default Value: 0
Verification: Design Review, Test
Source: Engineering (SPEC-0147)
6.2.7 HOAO Frame Rate
REQ# 2.1.1-4290
HOAO shall allow the WFC specialist to set the operating rate of the HOAO real-time system.
Setting details:
Level: Engineering
Format: float
Range of Values: 1 – 2000+ Hz
Default Value: 2000 Hz
Note: The HOAO frame rate constrains the maximum exposure time for the HOAO camera.
Note 2: The maximum value will be determined during assembly and testing, it will be at least 2000 Hz.
Verification: Design Review, Test
Source: Engineering (SPEC-0147)
6.2.8 HOAO Camera Exposure Control Method
REQ# 2.1.1-4295
HOAO shall allow the User to set the method used for controlling the HOAO camera exposure time.
Setting details:
Level: User
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 51 of 73
Format: string
Range of Values: auto, manual
Default Value: auto
Note: If value is manual, HOAO exposure time must have a valid value. If auto then HOAO minimum
flux threshold, HOAO maximum flux threshold, and HOAO exposure time update period must all have
valid values.
Verification: Design Review, Test
Source: Engineering (SPEC-0147)
6.2.9 HOAO Camera Exposure Time
REQ# 2.1.1-4300
HOAO shall allow the User to set exposure time of the HOAO camera.
Setting details:
Level: User
Format: integer
Range of Values: [2, 1,000,000
𝑓𝑟𝑎𝑚𝑒 𝑟𝑎𝑡𝑒− 5] microseconds
Default Value: 350 microseconds
Other Verifications:
Maximum exposure time is set by the frame rate. For the nominal frame rate of 2000 Hz, the
maximum exposure time is 495 microseconds.
Verification: Design Review, Test
Source: Engineering (SPEC-0147)
6.2.10 HOAO Minimum Flux per Exposure
REQ# 2.1.1-4305
HOAO shall allow the WFC Specialist to set the minimum flux threshold for adjusting to longer exposure
times.
Setting details:
Level: Engineering
Format: integer
Range of Values: [0, 1022] DN
Default Value: 512 DN
Other Verifications: Required when exposure control method = auto. Must be less than the maximum flux
per exposure.
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3100)
6.2.11 HOAO Maximum Flux per Exposure
REQ# 2.1.1-4310
HOAO shall allow the WFC Specialist to set the maximum flux threshold for adjusting to shorter
exposure times.
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 52 of 73
Setting details:
Level: Engineering
Format: integer
Range of Values: [1-1023] DN
Default Value: 818 DN
Other Verifications: Required when exposure control method = auto. Must be greater than the minimum
flux per exposure.
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3100)
6.2.12 HOAO Exposure Time Update Period
REQ# 2.1.1-4315
HOAO shall allow the WFC Specialist to set the time between updates for automatic exposure time
control.
Setting details:
Level: Engineering
Format: float
Range of Values: [1-300] seconds
Default Value: 10
Other Verifications: Required when exposure control method is set to auto.
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3100)
6.2.13 Load High-Order Reconstruction Matrix
REQ# 2.1.1-4320
HOAO shall allow the WFC specialist to select a high-order reconstruction matrix to load from the
parameter database or via file upload. The reconstruction matrix shall be loaded into the HOAO Real-
Time Processor memory.
Setting details:
Level: Engineering
Format: string
Range of Values: TBD
Default Value: N/A
Verification: Design Review, Test
Source: Science (SPEC-0058, 2.1.1-0045)
6.2.14 Load Low-Order Shift Reconstruction Matrix
REQ# 2.1.1-4325
HOAO shall allow the WFC specialist to select a low-order shift reconstruction matrix to load from the
parameter database or via file upload. The reconstruction matrix shall be loaded into memory where it
will be used for calculating low-order modal coefficients from residual shift measurements, as in 5.13.
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 53 of 73
Setting details:
Level: Engineering
Format: string
Range of Values: TBD
Default Value: N/A
Verification: Design Review, Test
Source: Engineering (SPEC-0129)
6.2.15 Load Low-Order Actuator Reconstruction Matrix
REQ# 2.1.1-4330
HOAO shall allow the WFC specialist to select a low-order actuator reconstruction matrix to load from
the parameter database or via file upload. The reconstruction matrix shall be loaded into memory where it
will be used for calculating low-order modal coefficients from DM actuator commands, as in 5.14.
Setting details:
Level: Engineering
Format: string
Range of Values: TBD
Default Value: N/A
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3060)
6.2.16 Servo Gain Update period
REQ# 2.1.1-4335
HOAO shall allow the WFC specialist set the period of time for automatic updates to HOAO servo gains.
This update period will also control the rate at which high-order reconstruction matrices are updated.
Setting details:
Level: Engineering
Format: float
Range of Values: [0.01, 100] seconds
Default Value: 1
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3090)
6.2.17 High-Order Servo Loop DM Gain Control Method
REQ# 2.1.1-4340
HOAO shall allow the User to set the method used to control DM servo loop gains. If set to auto, the
high-order reconstruction matrix will also be updated automatically.
Setting details:
Level: User
Format: string
Range of Values: manual, auto
Default Value: auto
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 54 of 73
Other Validations:
If set to manual, DM servo gains must be valid; if auto, gain update period must be valid.
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3090)
6.2.18 High-Order Servo Loop DM Gains
REQ# 2.1.1-4345
HOAO shall allow the User to set the leak factor and proportional and integral gains used in the DM
servo loop.
Setting details:
Level: User
Format: float[3]
Range of Values: TBD
Default Value: TBD
Verification: Design Review, Test
Source: Engineering (SPEC-0147)
6.2.19 High-Order Servo Loop FTT Gain Control Method
REQ# 2.1.1-4350
HOAO shall allow the User to set the method used to control FTT servo loop gains.
Setting details:
Level: User
Format: string
Range of Values: manual, auto
Default Value: auto
Other validations:
If set to manual, FTT servo gains must be valid; if auto, gain update period must be valid.
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3090)
6.2.20 High-Order Servo Loop FTT Gains
REQ# 2.1.1-4355
HOAO shall allow the User to set the proportional and integral gains used in the FTT servo loop.
Setting details:
Level: User
Format: float[2]
Range of Values: TBD
Default Value: TBD
Verification: Design Review, Test
Source: Engineering (SPEC-0147)
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 55 of 73
6.2.21 Load Actuator Gains Array
REQ# 2.1.1-4360
HOAO shall allow the WFC specialist to load an array of actuator gains from the parameter database or
via file upload.
Setting details:
Level: Engineering
Format: string
Range of Values: TBD
Default Value: TBD
Verification: Design Review, Test
Source: Engineering (SPEC-0147)
6.2.22 Load Actuator Offsets Array
REQ# 2.1.1-4365
HOAO shall allow the WFC specialist to load an array of actuator offsets from the parameter database or
via file upload.
Setting details:
Level: Engineering
Format: string
Range of Values: TBD
Default Value: TBD
Verification: Design Review, Test
Source: Engineering (SPEC-0147)
6.2.23 Reference Subaperture ID
REQ# 2.1.1-4370
HOAO shall allow the WFC specialist to select which subaperture to use as a reference for calculation of
image shifts and exposure times.
Setting details:
Level: Engineering
Format: integer
Range of Values: [1, 2304?]
Default Value: TBD
Verification: Design Review, Test
Source: Engineering (SPEC-0147)
6.2.24 Reference Image Update Method
REQ# 2.1.1-4375
HOAO shall allow the user to set the update method for the HOAO subaperture reference image.
Setting details:
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 56 of 73
Level: User
Format: string
Range of Values: auto, manual
Default Value: auto
Other Validations:
Reference image tolerance threshold and reference image contrast threshold must have valid
values.
Verification: Design Review, Test
Source: Science (SPEC-0058, 2.1.1-0030)
6.2.25 Reference Image Update Period
REQ# 2.1.1-4380
HOAO shall allow the user to set the period of time between reference image updates.
Setting details:
Level: User
Format: float
Range of Values: [1, 600] seconds
Default Value: 30
Other Validations:
Reference image tolerance threshold and reference image contrast threshold must have valid
values.
Verification: Design Review, Test
Source: Engineering (SPEC-0147)
6.2.26 Reference Image Tolerance Threshold
REQ# 2.1.1-4385
HOAO shall allow the user to set the tolerance threshold for the reference image. When selecting a new
reference image from a set of potential reference images, the tolerance threshold sets the maximum
difference allowed between the shift of the chosen reference image and the mean shift of all potential
images.
Setting details:
Level: User
Format: float
Range of Values: [0.001, 0.5] pixels
Default Value: 0.05
Verification: Design Review, Test
Source: Engineering (SPEC-0147)
6.2.27 Reference Image Contrast Threshold
REQ# 2.1.1-4390
HOAO shall allow the user to set the contrast threshold for the reference image.
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 57 of 73
Setting details:
Level: User
Format: float
Range of Values: [0, 100] percent
Default Value: 2
Note: The contrast of the reference subaperture is given in percent rms:
𝐶𝑟𝑚𝑠 =√𝑁 ∑ (𝐼(𝑖) − 𝐼)2𝑁
𝑖=1
∑ 𝐼𝑁𝑖=1 (𝑖)
∗ 100
where I is a vector containing all pixel intensity values of the reference subaperture, N is the total number
of pixels in the reference subaperture, and 𝐼 is the mean pixel value, 𝐼 =1
𝑁∑ 𝐼(𝑖)𝑁
𝑖=1 .
Verification: Design Review, Test
Source: Engineering (SPEC-0147)
6.2.28 Get New Reference on Lock
REQ# 2.1.1-4395
HOAO shall allow the WFC specialist to select whether or not HOAO will automatically acquire a new
subaperture reference image upon receiving a request to lock the AO control loop.
Setting details:
Level: Engineering
Format: boolean
Range of Values: yes, no
Default Value: yes
Verification: Design Review, Test
Source: Engineering (SPEC-0147)
6.2.29 Get Immediate Reference
REQ# 2.1.1-4400
HOAO shall allow the WFC specialist to request an immediate reference image. HOAO will save the next
subaperture image as the reference.
Setting details:
Level: User
Format: TBD
Range of Values: N/A
Default Value: N/A
Verification: Design Review, Test
Source: Engineering (SPEC-0147)
6.2.30 Get Tolerance Reference
REQ# 2.1.1-4405
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 58 of 73
HOAO shall allow the user to request a tolerance reference image. HOAO will select a new subaperture
reference image based on tolerance and contrast settings.
Note: When selecting a tolerance reference, HOAO takes a number of consecutive images from the
chosen reference subaperture and measures their shifts relative to the first image if the DM loop is
unlocked or relative to the current reference image if the DM loop is locked. It then chooses an image,
with contrast above the contrast threshold and whose shift difference from the mean is less than the
tolerance threshold, to be the new reference image.
Setting details:
Level: User
Format: TBD
Range of Values: N/A
Default Value: N/A
Other Validations: tolerance threshold and contrast threshold must have valid values.
Verification: Design Review, Test
Source: Engineering (SPEC-0147)
6.2.31 Apply DM Actuator Map
REQ# 2.1.1-4410
HOAO shall allow the WFC specialist to apply a given array of actuator values to the DM.
Setting details:
Level: Engineering
Format: integer[1600]
Range of Values: [-32768, 32767]
Default Value: N/A
Verification: Design Review, Test
Source: Engineering (SPEC-0147)
6.2.32 Apply DM Modal Coefficients
REQ# 2.1.1-4415
HOAO shall allow the WFC specialist to apply a given array of modal coefficients to the DM. The
coefficients given are in the Fringe Zernike basis.
Setting details:
Level: Engineering
Format: float[37]
Range of Values: [-2500, 2500]
Default Value: N/A
Verification: Design Review, Test
Source: Engineering (SPEC-0147)
6.2.33 DM Out of Bounds Threshold
REQ# 2.1.1-4417
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 59 of 73
HOAO shall allow the WFC specialist to set the threshold which, if exceeded, causes the HOAO
controller to reduce the DM gains and number of modes reconstructed by the DM.
Setting details:
Level: Engineering
Format: integer
Range of Values: [0, 2304]
Default Value: TBD
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3080)
6.2.34 DM OOB Gain Increment
REQ# 2.1.1-4419
HOAO shall allow the WFC specialist to set the increment by which the DM gains are reduced when the
DM OOB threshold is exceeded.
Setting details:
Level: Engineering
Format: float
Range of Values: [0, 1]
Default Value: 0.1
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3095)
6.2.35 DM OOB recovery period
REQ# 2.1.1-4420
HOAO shall allow the WFC specialist to set the number of consecutive frames for which OOB shift
counts must be below the DM OOB threshold before HOAO will increase the DM gains and number of
modes reconstructed.
Note: The gains and reconstruction matrices will never be increased beyond those indicated by the
optimization lookup tables.
Setting details:
Level: Engineering
Format: integer
Range of Values: [1, 10,000] frames
Default Value: 10
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3095)
6.2.36 FTT Out of Bounds Threshold
REQ# 2.1.1-4423
HOAO shall allow the WFC specialist to set the threshold which, if exceeded, causes the HOAO
controller to reduce the FTT gains.
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 60 of 73
Setting details:
Level: Engineering
Format: integer
Range of Values: [0, 2304]
Default Value: TBD
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3095)
6.2.37 FTT Out of Bounds Gain Increment
REQ# 2.1.1-4425
HOAO shall allow the WFC specialist to set the increment by which the FTT gains are reduced when the
FTT OOB threshold is exceeded.
Setting details:
Level: Engineering
Format: float
Range of Values: [0, 1]
Default Value: 0.1
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3095)
6.2.38 FTT OOB recovery period
REQ# 2.1.1-4427
HOAO shall allow the WFC specialist to set the number of consecutive frames for which OOB shift
counts must be below the FTT OOB threshold before HOAO will increase the FTT gains.
Note: The gains will never be increased beyond those indicated by the optimization lookup tables.
Setting details:
Level: Engineering
Format: float
Range of Values: [1, 10,000] frames
Default Value: 10
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3095)
6.2.39 FTT Range Offload Threshold
REQ# 2.1.1-4430
HOAO shall allow the WFC specialist to set the threshold which, if exceeded, causes HOAO to offload
the mean FTT mirror position to the TMA.
Setting details:
Level: Engineering
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 61 of 73
Format: float
Range of Values: [0.10, 1.00] fraction of FTT mirror full range
Default Value: 0.33
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3040)
6.2.40 FTT Offload Period
REQ# 2.1.1-4435
HOAO shall allow the WFC specialist to set period of time over which the FTT module position will be
averaged when evaluating whether or not the FTT range threshold has been exceeded.
Setting details:
Level: Engineering
Format: float
Range of Values: [5, 100] seconds
Default Value: 30
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3040)
6.2.41 FTT Offload Gain
REQ# 2.1.1-4440
HOAO shall allow the WFC specialist to set the fraction of total FTT mirror position will be offloaded
when the FTT offload range threshold is exceeded.
Setting details:
Level: Engineering
Format: float
Range of Values: [0, 2.00]
Default Value: 0.50
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3040)
6.2.42 Pupil Motion Subaperture Selection
REQ# 2.1.1-4445
HOAO shall allow the WFC specialist to select which four HOAO subapertures to use for measuring
pupil motion.
Setting details:
Level: Engineering
Format: integer[4]
Range of Values: [0, 2304]
Default Value: TBD
Other validations: Subapertures must be in correct order (ordering TBD) and the same subaperture may
not be used twice.
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 62 of 73
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3105)
6.2.43 Pupil Motion Measurement Period
REQ# 2.1.1-4450
HOAO shall allow the WFC specialist to select the period of time between broadcast of pupil motion
measurements. Subaperture intensity measurements update at a fixed rate (10 Hz) so this parameter sets
the number of frames that are averaged for each measurement.
Setting details:
Level: Engineering
Format: float
Range of Values: [0.1, 300] seconds
Default Value: 3
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3105)
6.2.44 Number of Images to Accumulate
REQ# 2.1.1-4455
HOAO shall allow the WFC specialist to set the number of images to accumulate for dark and gain
calibrations.
Setting details:
Level: Engineering
Format: integer
Range of Values: [1-20,000]
Default Value: 1000
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3005, 2.1.1-3010)
6.2.45 Active Field Stop Assembly Aperture
REQ# 2.1.1-4457
HOAO shall allow the WFC specialist to select an aperture in the field stop assembly.
Setting details:
Level: Engineering
Format: string
Range of Values: fieldstop, pinhole, shutter
Default Value: fieldstop
Other Validations: Values “pinhole” or “shutter” require the WFC mode to be “calibrate”.
Verification: Design Review, Test
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 63 of 73
Source: Operations (SPEC-0129, 4.2.3)
6.2.46 Load DM registration pattern
REQ# 2.1.1-4459
HOAO shall allow the WFC specialist to select a DM registration pattern from an online database or via
file upload.
Setting details:
Level: Engineering
Format: string (filename)
Range of Values: TBD
Default Value: N/A
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-3085)
6.3 HOAO System Mode Requirements
HOAO system modes reflect the overall WFC configuration as controlled by the WCCS. Specific
requirements for HOAO subsystem performance in each mode are contained in SPEC-0129.
6.3.1 Off
REQ# 2.1.1-4460
HOAO shall allow the user or WFC specialist to send shutdown and power off commands.
Settings used:
N/A
Verification: Design Review, Test
Source: Operations (SPEC-0129, 2.4.1)
6.3.2 Idle
REQ# 2.1.1-4465
HOAO shall be ready to act on configurations received from WCCS or the HOAO engineering GUI.
Settings used:
N/A
Verification: Design Review, Test
Source: Operations (SPEC-0129, 2.4.2)
6.3.3 Calibrate
REQ# 2.1.1-4470
HOAO shall allow the user or WFC specialist to command it to perform calibration activites.
Calibrations available:
Dark
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 64 of 73
Gain
Center steering mirror
Focus
DM registration
Subaperture offset internal calibration
Subaperture offset NCP calibration
DM-assisted alignment
Pupil stabilization
Manual
Field sizing and rotation
Verification: Design Review, Test
Source: Operations (SPEC-0129, 2.4.3)
6.3.3.1 Calibrate: dark
REQ# 2.1.1-4475
HOAO shall allow the user or WFC specialist to command it to perform a dark calibration.
Settings used:
HOAO camera exposure time
Number of frames to average
Active field stop assembly aperture
Note: The reason why the exposure time can be fixed and is not tied to ‘auto’ is that the dark current/bias
in the HOWFS camera was found to be constant for all exposure times within those expected during
operational use.
An issue might be that there could be stray light that is recorded in a dark, and subtracted during the
calibration – of course in that case, the dark data will depend on the exposure time.
Verification: Design Review, Test
Source: Operations (SPEC-0129, 4.3.1)
6.3.3.2 Calibrate: gain
REQ# 2.1.1-4480
HOAO shall allow the user or WFC specialist to command it to perform a camera gain calibration. If the
telescope is not in a random pointing mode, the HOWFS field steering mirror will provide the random
pointing needed for gain calibration. Random pointing can be achieved using a WCCS-level script.
Settings used:
HOAO camera exposure time
Active field stop assembly aperture = fieldstop
Number of frames to average
Note: The gain calibration assumes camera linearity over the range of expected exposure times set by the
auto adjust method.
Verification: Design Review, Test
Source: Operations (SPEC-0129, 4.3.2)
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 65 of 73
6.3.3.3 Calibrate: center steering mirror
REQ# 2.1.1-4485
HOAO shall allow the user or WFC specialist to center the HOAO field steering mirror. This automated
calibration procedure shall return the calibration status (pass, fail, error) along with the final centering
error in units of detector pixels.
Settings used:
Active field stop assembly aperture = fieldstop
HOAO camera exposure method
Verification: Design Review, Test
Source: Operations (SPEC-0129, 4.3.7.3)
6.3.3.4 Calibrate: field sizing and rotation
REQ# 2.1.1-4486
HOAO shall allow the user or WFC specialist to command it to verify the field sizing and rotation of the
HOWFS.
Settings used:
HOAO camera exposure time
Active field stop assembly aperture = open
HOAO camera exposure method
Verification: Design Review, Test
Source: Operations (SPEC-0129, 4.3.7.1)
6.3.3.5 Calibrate: focus
REQ# 2.1.1-4490
HOAO shall allow the user or WFC specialist to command it to perform a focus calibration. This
automated calibration procedure shall focus on a point source reference at GOS by moving the HOWFS
objective lens until the Zernike focus term from HOWFS shifts is minimized. The calibration shall return
the calibration status (pass, fail, error) along with the final Zernike focus error.
Settings used:
HOAO camera exposure method
aO Engine event period
aO Engine event modal basis
aO Engine event frameskip
Verification: Design Review, Test
Source: Operations (SPEC-0129, 4.3.7.4)
6.3.3.6 Calibrate: DM registration
REQ# 2.1.1-4495
HOAO shall allow the user or WFC specialist to command it to perform DM registration. This automated
calibration shall poke the DM actuators in a pre-determined pattern or set of patterns and analyze the
resulting shift measurements to determine the registration between the DM and HOWFS. On completion,
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 66 of 73
this calibration shall return the calibration status (pass, fail, error) and the measured registration error (x
shift, y shift, rotation, scaling).
Settings used:
HOAO camera exposure method
DM registration pattern
Verification: Design Review, Test
Source: Operations (SPEC-0129, 4.3.7.5)
6.3.3.7 Calibrate: internal offsets
REQ# 2.1.1-4500
HOAO shall allow the user or WFC specialist to command it to perform internal offset calibration.
Settings used:
HOAO camera exposure method
Verification: Design Review, Test
Source: Operations (SPEC-0129, 4.3.7.6)
6.3.3.8 Calibrate: NCP offsets
REQ# 2.1.1-4505
HOAO shall allow the user or WFC specialist to command it to perform NCP offset calibration.
Settings used:
HOAO camera exposure method
Verification: Design Review, Test
Source: Operations (SPEC-0129, 4.3.8)
6.3.3.9 Calibrate: DM-assisted alignment
REQ# 2.1.1-4510
HOAO shall allow the user or WFC specialist to command it to perform DM-assisted alignment.
Settings used:
HOAO frame rate
HOAO camera exposure control method
Reference subaperture ID
Get new reference on lock
DM Out of bounds threshold
FTT Out of bounds threshold
Field steering mirror position
Field steering mirror LUT
Verification: Design Review, Test
Source: Operations (SPEC-0129, 4.3.11)
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 67 of 73
6.3.3.10 Calibrate: Pupil stabilization
REQ# 2.1.1-4515
HOAO shall allow the user or WFC specialist to command it to perform pupil stabilization in order to
assist calibrations of other instruments.
Settings used:
HOAO frame rate
HOAO camera exposure control method
Pupil motion subaperture selection
Pupil motion measurement period
Verification: Design Review, Test
Source: Operations (SPEC-0129, 4.3.10)
6.3.3.11 Calibrate: manual
REQ# 2.1.1-4520
HOAO shall allow the user or WFC specialist to command it to allow manual calibration through the
engineering GUI.
Settings used:
N/A
Verification: Design Review, Test
Source: Operations (SPEC-0129, 4.3)
6.3.4 WFC-OPM1: Diffraction limited on-disk
REQ# 2.1.1-4525
HOAO shall allow the user or WFC specialist to command it to close the DM and FTT loops, send low-
order DM modal coefficients as events, and report pupil position measurements as events.
Settings used:
DM gain control method
FTT gain control method
aO engine event period
aO engine event basis
aO engine event frameskip
r0 calculation period
r0 calculation frameskip
HOAO frame rate
HOAO camera exposure control method
Reference subaperture ID
Reference image update method
Get new reference on lock
DM out of bounds threshold
DM OOB gain increment
DM OOB recovery period
FTT out of bounds threshold
FTT OOB gain increment
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 68 of 73
FTT OOB recovery period
FTT range offload threshold
FTT offload period
Pupil motion subaperture selection
Pupil motion measurement period
Field steering mirror position
Field steering mirror LUT
Verification: Design Review, Test
Source: Operations (SPEC-0129, 2.4.4)
6.3.5 WFC-OPM2: Seeing limited on-disk
REQ# 2.1.1-4530
HOAO shall allow the user or WFC specialist to command it to close the FTT loop and report pupil
position measurements as events.
Settings used:
FTT gain control method
r0 calculation period
r0 calculation frameskip
HOAO frame rate
HOAO camera exposure control method
Reference subaperture ID
Reference image update method
Get new reference on lock
FTT out of bounds threshold
FTT OOB gain increment
FTT OOB recovery period
FTT range offload threshold
FTT offload period
Pupil motion subaperture selection
Pupil motion measurement period
Field steering mirror position
Field steering mirror LUT
Verification: Design Review, Test
Source: Operations (SPEC-0129, 2.4.5)
6.3.6 WFC-OPM3: Seeing limited coronal
REQ# 2.1.1-4535
This mode shall be identical to idle.
Settings used:
N/A
Verification: Design Review, Test
Source: Operations (SPEC-0129, 2.4.6)
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 69 of 73
6.3.7 WFC-OPM4: Limb occulting with image stabilization
REQ# 2.1.1-4540
This mode shall be identical to idle.
Settings used:
N/A
Verification: Design Review, Test
Source: Operations (SPEC-0129, 2.4.7)
6.4 Mechanism Control Requirements
6.4.1 Field Steering Mirror Position
REQ# 2.1.1-4545
HOAO shall allow the user to adjust the position of the HOAO FSM. Units for HOAO FSM motion are
arcseconds in the telescope focal plane.
Setting details:
Level: User
Format: float[2] or string
Range of Values: [-30, +30] arcseconds or named position
Default Value: default (named position)
Verification: Design Review, Test
Source: Operations (SPEC-0129, 3.1.2)
6.4.2 Objective Lens Look-up Table
REQ# 2.1.1-4550
HOAO shall allow the WFC specialist to select a look-up table for use with the Field Steering Mirror
(FSM) defocus correction.
Setting details:
Level: Engineering
Format: string
Range of Values: TBD
Default Value: N/A
Verification: Design Review, Test
Source: Operations (SPEC-0147, 2.1.1-1070)
6.4.3 Objective Lens Position
REQ# 2.1.1-4555
HOAO shall allow the WFC specialist to adjust the HOWFS objective lens assembly set position along
the z-axis.
Setting details:
Level: Engineering
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 70 of 73
Format: float or string
Range of Values: TBD
Default Value: default (named position)
Verification: Design Review, Test
Source: Operations (SPEC-0129, 4.3.7.4)
6.4.4 Microlens Array Position
REQ# 2.1.1-4565
HOAO shall allow the WFC specialist to position the microlens array assembly along the x and y-axes.
Setting details:
Level: Engineering
Format: float[2] or string
Range of Values: TBD
Default Value: default (named position)
Verification: Design Review, Test
Source: Operations (SPEC-0129, 4.3.7.1)
6.4.5 Relay Lens #1 Position
REQ# 2.1.1-4570
HOAO shall allow the WFC specialist to position the relay lens #1 assembly along the z-axis.
Setting details:
Level: Engineering
Format: float or string
Range of Values: TBD
Default Value: default (named position)
Verification: Design Review, Test
Source: Operations (SPEC-0129, 4.3)
6.4.6 Relay Lens #2 Position
REQ# 2.1.1-4575
HOAO shall allow the WFC specialist to position the relay lens #2 assembly along the z-axis.
Setting details:
Level: Engineering
Format: float or string
Range of Values: TBD
Default Value: default (named position)
Verification: Design Review, Test
Source: Operations (SPEC-0129, 4.3)
6.4.7 Camera Mount Position
REQ# 2.1.1-4580
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 71 of 73
HOAO shall allow the WFC specialist to position the camera mount assembly along the x and y-axes.
Setting details:
Level: Engineering
Format: float[2] or string
Range of Values: TBD
Default Value: default (named position)
Verification: Design Review, Test
Source: Operations (SPEC-0129, 4.3.7.1)
6.4.8 Camera Relay Optics Assembly Position
REQ# 2.1.1-4585
HOAO shall allow the WFC specialist to position the camera relay optics assembly along the z-axis.
Setting details:
Level: Engineering
Format: float or string
Range of Values: TBD
Default Value: default (named position)
Verification: Design Review, Test
Source: Engineering (SPEC-0146, 2.1.1-1010)
6.5 Interface Requirements
6.5.1 WCCS interface
REQ# 2.1.1-4590
HOAO shall provide an interface to the higher-level WCCS control software, as defined by the WCCS
design documentation. This interface shall allow the WCCS to control the configuration of HOAO.
Verification: Design Review, Test
Source: Engineering (SPEC-0129, 3.2)
6.5.2 Engineering user interface
REQ# 2.1.1-4595
HOAO shall provide an engineering user interface that implements all functional operations of the HOAO
system. The engineering user interface shall be based upon the DKIST CSF JES tool and shall be
operable from computers on the DKIST control network.
Verification: Design Review, Test
Source: Operations (SPEC-0129, 3.2.3)
6.5.3 HOAO status screen
REQ# 2.1.1-4600
HOAO shall provide a status screen that displays information on HOAO system operation that is
sufficient to determine the operating mode(s) of HOAO, system performance, and diagnostic information
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 72 of 73
necessary for efficient and accurate operation. The status screen shall display the following information:
HOAO correction mode, HOWFS subaperture images, subaperture shift measurements, DM and FTT
actuator commands, modal aberration spectra (Zernike, both instantaneous and time-averaged), OOB
statistics, residual wavefront error, modal coefficient offloads, r0 graph display, servo loop gains, and
active reconstruction matrix. The status screen shall also be able to calculate and display the temporal
power spectrum of a user-selected DM actuator or wavefront sensor subaperture with a lookback time of
1 second or more. Additionally, the status screen should be able to display the averaged temporal power
spectra of multiple DM actuators overplotted with the averaged residual wavefront error power spectra of
those same actuators.
Verification: Design Review, Test
Source: Science (SPEC-0058, 2.1.1-0080), Operations (SPEC-0129, 3.3.1)
6.6 Real-Time system requirements
6.6.1 Compute time
REQ# 2.1.1-4605
The HOAO real-time system shall have a compute latency of less than 450 microseconds. The compute
latency is defined as the time elapsed between when the real-time system receives the final HOWFS
image pixel and the time at which actuator commands are sent to the DM drive electronics.
Verification: Design Review, Test
Source: Science (SPEC-0058, 2.1.1-0015; SPEC-0009)
6.6.2 FPGA firmware
REQ# 2.1.1-4610
Firmware within the HOAO FPGA real-time processing unit shall meet all requirements in SPEC-0125:
High Order Adaptive Optics Real Time FPGA Firmware Specification.
Verification: Design Review, Test
Source: Engineering (SPEC-0125)
6.7 HOAO telemetry data products
6.7.1 Telemetry latency
REQ# 2.1.1-4615
The HOAO telemetry data shall be streamed to the DHS over the BDT. The total elapsed time allowed
between the end of a HOAO control cycle and the time at which all telemetry data associated with that
cycle is available to other instruments is 100 milliseconds.
Note: The DHS is not designed to handle high frame-rate (2kHz) data so the HOAO telemetry must be
buffered into multi-frame blocks and transmitted at a lower rate. The 100 millisecond requirement is the
amount of delay time that the VBI team estimates to be tolerable before the speckle-processing code is
impacted.
Verification: Design Review, Test
Source: Science (SPEC-0058, 2.1.1-0050)
High-Order Adaptive Optics Design Requirements
SPEC-0146, Revision A Page 73 of 73
6.7.2 Telemetry data format
REQ# 2.1.1-4620
The HOAO telemetry data shall generate the following data products for access by DHS Processing
Plugins (SPEC-0016).
At minimum, but not limited to, the following data shall be published in a DHS Processing Plugin
readable hardware and software format:
Stream Data Product:
Shifts
Residual actuator commands for TT and DM
Final Actuator commands for TT and DM
Stream Data Header:
Time stamp
Frame number
Lock status
WFS RMID
Out-of-bounds count
Interactuator stroke violations
Name of actuator-to-KL transformation matrix
Every Shift/Actuator Command frame shall be published. This data shall be published at a maximum rate
of 2 kHz.
Note: For a full description of the HOAO telemetry data and its formatting, see ICD 2.3-4.3 WCCS to
DHS.
Verification: Design Review, Test
Source: Science (SPEC-0058, 2.1.1-0050)
6.7.3 Header Data
REQ# 2.1.1-4625
The HOAO control system shall generate metadata in accordance with SPEC-0122 (Data Model).
Note: HOAO metadata are both important for the interpretation of its own Data Products as well as
instrument Data Products.
Verification: Design Review, Test
Source: Science (SPEC-0122, 4.3.0122-0070)