1 SECTION I Introduction. 2 This page intentionally left blank.

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SECTION I

Introduction

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Introductions

• Recognition of the Review Committee and Gemini

• Introductions

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We will start with the current status of the project including an overview of the project schedule, summary of the opto-mechanical design, electrical design, systems design, and the cost performance to date.

The summary of the committee report items will include an issues compliance matrix, and address specific committee concerns.

In the project overview section we will present both the plan to the RR and the plan to completion. A discussion of the remaining issues between Gemini and NOAO is included.

Project management will cover the GNIRS project organization, the schedule, critical path, remaining capital and labor costs, cost performance tracking, reporting, etc.

The new GNIRS configuration will be presented in summary to familiarize the committee with the new instrument design. We will present examples of the requirements flowdown process, the top level configuration, and system integration.

Risk ID and mitigation is planned for the second day and will address all risk items previously pointed out by the committee plus additional items related to the new design, and the plan to mitigate these risks.

Sidney Wolff will then conclude our presentations and we will adjourn for the committee to caucus.

Overview of the Presentation

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Overview of the Presentation

• Current status of the project• Summary of committee report items• Project overview• Project management• The new GNIRS configuration• Risk identification and mitigation plan• Conclusion• Committee Caucus

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Committee Charge What is NOAO’s current cost estimate to complete GNIRS and on what

schedule? Is this estimate consistent with NOAO’s planned resources over the

duration of the GNIRS project? Have the technical issues (AURA report attached for reference)

identified by the AURA review committee been addressed adequately to permit continuation of GNIRS?

Does NOAO now have in place an appropriate management structure to track, plan, and control resources to ensure that GNIRS will be delivered on time and budget?

Are there any approaches to designing and fabricating GNIRS that can significantly accelerate the planned delivery, e.g., through the injection of additional NOAO resources, outsourcing the fabrication of components, etc.?

Have all contractual matters involving out of scope work, definition of work, and interfacing requirements been settled with IGPO?

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GNIRS Reprogramming Addresses All Committee Report Items

USGP WPM meets nearly daily with PM All information USGP requests is provided, in the format requested USGP attends all weekly staff meetings, notified of all other meetings in

advance PM solicits USGP input frequently More involvement of USGP in daily GNIRS activities Actively soliciting IGPO input Responsive to IGPO concerns More direct communication with NOAO Director Between Project and USGP WPM Systems engineering is a critical capability Meets all technical requirements Meets original weight requirements

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GNIRS Reprogramming Addresses All Committee Report Items

Clearly defined NOAO/USGP relationship We have a new philosophy of working

IGPO is a customer Our project is open (e.g., web site)

We have a new management structure Full time Project Manager who reports directly to NOAO Director USGP WPM reports to NOAO Director

GNIRS has new engineering & systems team Engineers do the design Formed systems engineering team (3 scientists plus PM)

GNIRS is a new configuration Optical design is essentially intact Repackaged or redesigned entire instrument

Addresses all technical issues in the AURA committee report

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SECTION II

Summary of Committee Report Items

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Committee Report Identified 9 Basic Concerns

New design addresses technical issues Systems engineering guided the design effort We have addressed the risk items and have a mitigation plan We have the best engineers in the organization on the project The project has high priority and reports directly to Sidney Wolff The IFU and OIWFS interfaces and integration have been addressed The instrument integration will be led by the project scientists Project Management shortcomings have been addressed We are confident the instrument will meet requirements

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Committee Report Identified 9 Basic Concerns

Unresolved technical issues No rigorous requirements flow down Lack of risk ID and mitigation plan Capability of engineering staff Organizational hierarchy IFU and OIWFS integration issues Lines of responsibility for systems integration Project management Overall technical capabilities of the GNIRS instrument

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Committee Report Pointed Out 5 Technical Risk Areas

Cool down time and thermal gradients Optical focus, alignment, mirror finish and

baffling Handling frame and local handling OIWFS modularity and integration/test IFU ICD and space constraints

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Compliance MatrixManagement/Design Compliance

Item # Committee Issue Yes No Comments

1 Recommendations x Appoint a PM and a PE x Only program manager appointed Separate PM and systems engineer x Systems engineering team Assign a Systems Engineer x Systems engineering team Adopt more rigourous PM tools x Institute configuration control x extensive control system using Access Use ICD's x Used for OIWFS, IFU, Gemini interfaces Create a systems error budget x Create a risk management plan x plan created Change from individual to team culture x implemented on GNIRS project Put more emphasis on importance of engineering x working on this Define the customer x Gemini viewed as the customer

2 Risk Mitigation Cool down time x cool down time within 4 day limit Temperature gradients x disk modules no longer used Focus changes x focus mechanism included in baseline Optical alignment x new plan simpler Mirror finish x Mirrors: 3 Al, 10 glass Radiation from gaps in shields x handled in design Handling frame x special frame no longer needed OIWFS modularity and alignment x OIWFS is mounted on a modular bench IFU space allowance and ICD x ample space provided by new design Requirements flowdown x SDN's for every level of design created

3 Issues and Concerns failed to recognize sched/bud problems x admitted and corrected failed to recognize unresolved problems x admitted and corrected failed to recognize issues/design shortcomings x admitted and corrected technical capabilities of GNIRS instrument x will meet science requirements soundness of the GNIRS design x redesigned instrument GNIRS worth investments to build it x meets a need and will be on time GNIRS will be an operational asset x multi-mode capabilites

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SECTION III

Current Status of the GNIRS Project

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Activities Chart to Restart Review Major milestones:

1/18 Hawaii review 2/10 OIWFS ICD deficiencies

identified 3/9 Durham IFU meeting 3/15 Interim review #1 5/25 Interim review #2 6/21 Baseline completed for RR 6/1,7/2 ICD reviews 7/20-21 Restart Review

Major activities: Preliminary opto-mechanical layout Cold motor T&E Final configuration design Requirements flowdown Electrical systems design Restart Review preparation

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Activities Chart to Restart Review

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Labor budget: $443.8K Projected thru 8/1: $337.1K Capital budget: $ 59.0K Projected thru 8/1: $ 75.0K Total under plan $ 90.7K

Projected Cost Performance Through July 31, 1999

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Restart Review work is approximately 89% complete

Budgeted labor dollars through RR is 76% spent RR budgeted non-payroll capital is 127% spent Performance (1/1-7/30)

BCWS = $443.8K (budgeted cost of work scheduled) BCWP = $394.9K (budgeted cost of work performed, total project to RR) ACWP = $337.1K (actual cost of work performed total project to RR) CPI = 1.17 (cost performance index = BCWP/ACWP) SPI = 0.89 (schedule performance index = BCWP/BCWS) Project is 11% behind schedule (overall to RR)

Critical path is 19% behind schedule (opto-mechanical design) Schedule to completion takes this into account

Under-spending reflects actual costs vs average rate planning FTE loading very close to prediction Cost delta’s related to actual salary rated vs planning numbers

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Virtual reviews solicited from Tom O’Brien, OSU Donald Pettie, ROE Bobby Ulich, Kaman Aerospace

In-process reviews: March 15 May 25

Reviews Prior to Restart Review

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Engineering Design will Finish December ‘99

Under-estimated the opto-mechanical design task OIWFS more complicated than anticipated

Design is mature enough to qualify for this review Three in-process reviews held Virtual reviews solicited from individuals outside

NOAO Reviewed by NSF and AURA in May ‘99

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Systems Done by the systems engineering team led by Jay Elias Primary vehicle is the System Design Note (SDN)

Major way of communicating requirements and analysis/test results Can be initiated by any member of the GNIRS team Not restricted to the requirements definition Produced for every level of the design

Optical-Mechanical Main optical bench, bulkhead structure, and thermal/structural interfaces are on critical path of

the project All mechanisms have been addressed and preliminary designs exist

More work to do on all Final designs will be tied to results of the drive prototyping

Optical design update is complete Only adjustments in camera lens spacing, etc., and stray light analysis remain

The preliminary mechanical design will be complete in the last quarter of this year

Electrical Details on specifics of connector panels and wiring remain to be defined All major electrical interfaces are defined and specified Includes planning for the integration of OIWFS hardware

Design Status

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Design Status

• Systems Engineering and Requirements Flowdown Activity is 95% complete

• Preliminary Opto-Mechanical Design is 81% Complete

• Preliminary Electrical Design is 75% Complete

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SECTION IV

Project Overview

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Outline

WBS Total Project including work to RR

Project schedule Plan to completion Critical path Capital and labor costs Resource needs

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Work Breakdown Structure (WBS)

The WBS covers the entire project from January to Completion in June, 2000 Main Elements:

Management and Reporting Systems Engineering Mechanical Electronics Software Alignment and Integration Deliverables Procurement

Charge numbers are derived from the WBS

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WBS

Chart on wall Accounts for activities to 6th level Contains summary rollups of costs of each

work element Main tool for tracking costs and assessing cost

performance

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Milestones

Complete Engineering Design Final Manuals Complete Analysis Complete Mechanism Drive Prototype Complete Prefab Review Mechanism

Filter Wheel Decker Slit slide Slit Module Prism Turret Grating Turret Camera Turret Camera Focus Environmental Cover Acquisition Mirror

System Software Complete Receive WFS Hardware Integration Start Integration Complete System Test Complete Deliverables

Pre-Acceptance Test

Ship to Hilo

Final Acceptance Test

Training

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Project Schedule

Schedule overview to completion Summary schedule chart Detail schedule on wall Project plan on wall

Highlights of the Project Plan

Plan to completion key milestones

milestone chart

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Critical Path

Engineering design Prototype mechanism drive testing Pre-Fab review Integration and test Camera turret assembly Acceptance Test

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Projected Labor and Capital CostFY99 FY00 FY01 FY02 Total MM Labor ($K) Capital ($K)

MD 11.8 30.4 54.8 11.5 108.4 $601.6ED 0.5 0.0 1.9 0.0 2.5 $13.7ET 3.1 8.6 4.0 4.4 20.1 $111.6ME 2.9 21.7 21.4 6.2 52.2 $289.6MT 2.4 13.9 13.9 9.3 39.4 $218.6OE 0.0 0.6 0.3 2.3 3.2 $17.7IM 1.0 9.4 81.3 14.0 105.7 $586.6P 0.0 16.2 11.0 2.1 29.3 $162.3OMT 0.0 0.1 0.8 3.1 4.0 $22.2PS 2.5 17.1 15.7 19.3 54.7 $303.6PM 2.5 15.6 15.0 10.6 43.8 $242.7PA 1.7 6.7 6.4 4.3 19.2 $106.3AA 1.2 7.0 6.9 4.9 20.0 $110.7EE 2.6 6.1 1.9 3.6 14.1 $78.5Eng 0.0 0.8 0.4 1.2 2.4 $13.1

Total 32.2 154.1 235.7 96.8 518.9

Labor Cost $178.9 $855.2 $1,307.5 $537.2 $2,878.8 $2,878.8

Capital $75.0 $41.4 $283.7 $9.0 $409.1

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Capital and Labor Cost

Cost to complete is $3.9 million Includes expenditures from January 1, 1999

Labor cost to Restart Review was $443.8K and capital cost was $75K.

Labor cost to go is $2.88 million for 519 man months Capital cost to go is $409K, including outsourcing of

fabrication items

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Sufficient Key Resources are Committed to do this Project

Facilities are available and designated for this project effort Shop Lab space Cleanroom Test dewar Equipment

ME’s, MD’s, IM’s are key resources to complete design and fabrication

PS(s) will be involved in and supervise integration and test PS(s) form systems engineering team to monitor all technical

activities

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Strategy Based on New Design with Proven Concepts

No new development Design for ease of fabrication/assembly/test Fabrication strategy

In-house IM’s used primarily for mechanism fabrication and assembly with conventional machining

Out-sourcing to vendors where cost effective Castings are planned for several large assemblies

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SECTION V

Project Management

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Outline

• Project organization

• Management methods

• Reporting

• Reviews planned

• Configuration control

• Customer relations

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The Project Reports Directly to Sidney Wolff

Lines of authority and responsibility All project functions report to the Project Manager Mechanical design is under mechanical engineering Systems engineering has technical prerogative

GNIRS Project Staff Project Manager Neil Gaughan Project Scientists Jay Elias/Brooke Gregory/Dick Joyce Mechanical Engineers Larry Goble/Gary Muller Electrical Engineers Andy Rudeen Optical Engineer Ming Liang Mechanical Designers John Andrew/Dave Rosin/Eric Downey Mechanical Tech Al Davis Electrical Tech Ken Don Programmer Richard Wolff Instrument Maker 4 assigned Project Assistant Dan Eklund Administrative Assistant Melissa Bowersock

Draw on other ETS resources as required

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The Project Reports Directly to Sidney Wolff

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Project Management will Employ Standard CSCS Methods

Project progress status will be assessed weekly Allows early identification of problems for critical item tracking Weekly project meetings

Cost data will be gathered bi-weekly from NOAO Accounting System Cost tracking will be done to the 5th and 6th level, as applicable

Charge numbers used on the project reflect the WBS

Cost/performance report types generated Accounting system generates custom reports of both labor dollars and

hours, and capital Summary progress report generated by PM Report to USGP monthly showing cost status MS Project standard performance reports

Vendor management and progress tracking

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Monthly Budget Labor & Capital ($K) to Restart Review

GNIRS Project Monthly StatusGNIRS Project as of June 30, 1999 Previous

Budget Actual Delta Cum Plan Cum Actual Cum Delta Total Cumthis Month this Month this Month to Date to Date to Date Budget to Dec 1998

Manpower $69,350 46,500$ 22,850$ 378,651$ 287,140$ 91,511$ 2,981,495$ 1,629,705$ Capital 10,000$ 2,900$ 7,100$ 59,000$ 72,797$ (13,797)$ 860,000$ 748,851$

Total 79,350$ 49,400$ 29,950$ 437,651$ 359,937$ 77,714$ 3,841,495$ 2,378,556$

J F M A M J J CUM'sLabor Costs ($K): Planned Labor 58.3 58.3 56.9 66.6 69.4 69.4 65.2 443.8 Actual Labor 65.4 46.5 43.9 37.5 47.3 46.5 287.1 CUM Over/Under 7.1 -4.6 -17.6 -46.6 -68.7 -91.5 -91.5

FTE Loading (FTE) Planned 10.5 10.5 9.8 10.5 10.5 10.5 10.5 72.8 Actual 12.5 9.3 8.9 9.7 9.7 10.7 60.8

Capital ($K) Planned Capital 11.0 10.0 5.0 5.0 8.0 10.0 10.0 59.0 Actual Capital 10.5 7.7 40.6 0.3 10.8 2.9 72.8

April labor is for first portion of the month only.

Explanations:March: FTE: Ilness's accounted for lower numbers for March Capital: filter order 29.8K Staff FTE's

contract labor7.0K ME Goblecold motors2.9K ME Mullermisc 0.15K EE Rudeen 80%

April ET Don 10% FTE: CAS data shows a low number MD Andrew Capital: contract labor2.6K MD Downey

software 0.76K MD Rosinelectronics material0.69K MD Davismisc material0.28K IM Rathcredit 3.84K Psced Eklund

May AA Bowersock 75% FTE: Contract designer joins staff full time PM Gaughan Capital: travel 7.1K Total FTE 10.65

contract labor2.9Kelectronics material0.52Kmisc 0.1K Scientists

June PS Elias 100% FTE Project scheduler added to staff PS Joyce 50%

cold motors1.76K PS (CTIO) Gregory 4 momisc 0.9K

Costs

0

10

20

30

40

50

60

70

80

J F M A M J JMonth Planned Labor

Actual Labor Planned Capital Actual Capital

Cumulative Over/UnderLabor Budget

-100

-80

-60

-40

-20

0

20

J F M A M J

Month

CUM Over/Under- - - - - Labor Budget

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Reporting is done Monthly to Gemini and Bi-Weekly to NOAO

Written report Cost status report to Gemini

Compares actuals to budget both monthly and cum

Bi-weekly reports to Sidney Wolff Designed to give project status to Director Reports financial and progress performance Bi-weekly report example in Appendix A

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Gemini review participation All formal reviews given to Gemini as the Customer Gemini is encouraged to attend and participate in all reviews

Web reviews Our design will be placed on the GNIRS web site as it matures Review and comments are always welcome GNIRS is publicly accessible <http://www.noao.edu/ets/gnirs>

Reviews

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Formal and Informal Reviews are Planned

Pre-Fabrication review Formal review at completion of prototyping and

engineering design Design will be frozen at this point and placed under

configuration control

Mid-Fabrication review to assess schedule performance

Held approximately one year after fabrication start

Internal reviews will be held as required Informal to assess readiness for fabrication,

procurement, etc.

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Configuration Control is Already Implemented on the Project Example is on the table Provides for complete tracking of all assemblies Contained in an Access Data Base Managed by Gary Muller, Sr. Mechanical

Engineer responsible for design and fabrication

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Customer Relations

Improved NOAO/USGP relationship USGP WPM meets nearly daily with PM All information USGP requests is provided, in the format

requested USGP attends all weekly staff meetings, notified of all other

meetings in advance PM solicits USGP input frequently More involvement of USGP in daily GNIRS activities

IGPO is viewed as the customer Actively soliciting IGPO input Responsive to IGPO concerns

Our project is open (e.g., web site)

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Section VI

GNIRS Configuration

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GNIRS is a New Configuration

• Requirements (Elias)• Top Level Configuration (Elias)• Detailed Configuration

(Gregory,Muller,Goble,Elias, Rudeen)• Sub-System Integration (Elias)• System Integration and Test (Elias)

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Requirements were analyzed and documented (1)

• System Design Notes (SDNs):The System Design Notes serve several purposes. First of all, they provide a written

definition and discussion of requirements. Second, they provide a discussion of the flow down of the requirements to individual sub-systems within the instrument. This discussion of allocations is critical to a sensible design. Third, they may provide a discussion of design trade-offs required to achieve required performance. This can in principle lead to a re-allocation of requirements.

• Interface Control Documents (ICDs):The Interface Control Documents define interfaces between external (Gemini telescope)

systems and GNIRS, and between IGPO-supplied subsystems (OIWFS, IFU, array controller) and GNIRS. Except for the IFU, the interfaces are common to more than one instrument, and GNIRS must conform to the ICD. The IFU is unique to GNIRS so the interface definition is more of a joint effort.

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• Role of SDNs: Define requirements Flow-down of requirements Analysis of design trade-offs

• Role of ICDs Define interfaces to external Gemini systems Define interfaces to IGPO-supplied sub-systems

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• Requirement Flow-Down:The design notes include summaries of the requirements and an allocations to sub-

systems. The flow-down chart illustrates this.

What is particularly important is that the requirements, as they flow down to individual sub-systems, are taken seriously by the engineering team. Thus, the approach to designing mechanisms is to design each within a weight budget rather than charging a “weight czar” to find out afterward whether the budget has been met. The design note approach permits feedback from the engineers in defining the allocations, and helps ensure that they “sign on” to the requirements.

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• Requirements Flow-Down: Formal allocation of requirements Engineering team understands requirements and

implements them in design

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Key Science Requirements (1)

• Optical Performance Image Quality: several requirements, can be simplified as design image quality of 85%

of light in 1 pixel with fabrication and assembly tolerances producing less than 5% degradation of delivered image.

Throughput: to be maximized, expectations >40%. Excess Background: light leaks and other excess thermal emission to be less than

detector dark current. Scattered light: scattered light to be less than detector dark for short wavelengths

(scattered light from night sky airglow).

• Flexure Flexure between OIWFS and spectrograph slit to be <12 microns (at slit) in 1 hour (5%

light loss with narrow slit) Flexure between spectrograph slit and detector to be <2.7 microns (at detector) in 1

hour (0.1 pixel) Shift of telescope secondary image on cold stop to be 1% of diameter maximum Should include effects of thermal variations as well as gravity

• Repeatability Repeatability during acquisition < 0.1 pixel Repeatability between configurations <10 pixels

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• Optical Performance• Flexure• Repeatability

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Cool-Down and Warm-Up Cool-down to take place in 4 days or less (96 hours). Warm up to take place in 1 day or less (24 hours).

Weight and Center of Gravity Instrument weight = 2000 kg (ballast if necessary) Instrument center of gravity located 1000 mm from ISS face, on optical axis Allowable error in moment is 400 N-m relative to telescope elevation axis.

Supports On-Instrument Wave-Front Sensor Provides near-IR guiding on stars within 3 arcmin field (excluding those in

spectrograph slit and acquisition field) Minimizes flexure effects (ISS, instrument and bench support) Parallel “instrument” within GNIRS: optical system, detector/controller, 3 mechanisms

(4 axes) Provided as sub-system by IfA (Hawaii) through IGPO

Support of Multiple Observing Modes Detailed below

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• Cool-Down and Warm-Up• Weight and Center of Gravity• Supports OIWFS• Support of Multiple Observing Modes

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Several Observing Modes Supported• 2 spatial scales: 0.05 arcsec/pixel for match to AO and best seeing; 0.15 arcsec/pixel for

more routine non-AO conditions (also gives longer slit coverage, more IFU coverage)

• 3 spectral resolutions: R~1800 for full coverage of atmospheric “window”; R= 5400/6000 for observations between OH airglow lines and general higher resolution; R= 18,000 (0.05 arcsec pixels only) for highest spectral resolution.

• Prism dispersers: spectral cross-dispersion for complete 0.9-2.4 micron spectra at both pixel scales; Wollaston prism for polarization analysis (used at both scales).

• Integral Field Unit (IFU): maps rectangular area onto virtual slit. Two units provide two scales (slightly less than equivalent long-slit modes). Works with all gratings; good performance required to 2.5 microns, desired to longer wavelengths. Provided as sub-system by U Durham through IGPO.

• Acquisition mode (“flip-in” mirror) allows direct, non-dispersed viewing through slit to identify and position objects. Does not require movement of dispersing elements.

• Diagnostic modes. Intended to aid in test or diagnosis of instrument. Pupil viewing (alignment of secondary with cold stop). Focus masks (accurate focus of detector on slit).

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Several Observing Modes Supported

• 2 Spatial Scales• 3 Spectral Resolutions• Cross-Dispersion and Polarization Analysis• Integral Field Unit• Acquisition• Diagnostics

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Top Level Configuration - External View

• Illustrates concept (details of dewar design will conform to internal structure).• Truss structure interfaces to telescope; controls flexure, responds to thermal

variations• Additional trusses support instrument for handling, attach electronics to main

structure. Interfaces to Gemini handling equipment are part of these trusses.• Design leads to minimal complexity in dewar shell• Central bulkhead contains all interfaces to innards: cooling system, structural

(bench support), electrical

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Top Level Configuration - External View

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Top Level Configuration - Internal View

• Illustrates layout of mechanical assemblies.• The design permits use of NIRI layout for OIWFS (2 folds removed). Key

elements of OIWFS identified: field lens, combination lens group (collimator/camera), gimbal mirror (field selection), filter wheel, combination Shack-Hartmann optics group and detector mount (“detector group”)

• The design minimizes folds in spectrograph. Key elements identified: fore-optics (spectrograph pick-off mirror, Offner relay and folds, filters, slit/decker), collimator, prism turret, grating turret, camera turret assembly (cameras, focus, detector)

• The design permits use of acquisition (“flip”) mirror (intercepts light from collimator and directs to camera). Minimizes motion requirements on disperser turrets.

• Central location for most large assemblies simplifies structural and thermal design.

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OIWFS field lens

Lens group

Gimbal mirror

OIWFS Filter wheel

Entrance Window

Pick off, Focal plane # 1

Offner relay

Filter wheels

Decker slide

Collimator

Camera turret

Detector, Focal plane # 4

Prism turret

Grating turret

Long cam fold flats

Flip mirrornot shown

Slit slideIFU’s, Focalplane # 2

OIWFS Detector groupFocal plane # 3

Internal Mechanical Configuration

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Detailed Configuration

• Optical Design (Gregory)• Mechanical Design (Muller, Goble, Elias)• Electronic Design (Rudeen)

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Outline: Optical Design• Overview• Foreoptics• Dispersers• Cameras• Performance• Materials selection and coatings• Background, stray light

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Optical Layout The layout shows a short camera in place in observing mode. Only the science beam (not the

wavefront sensor (WFS) beam) is shown. Light enters the instrument from the lower left and encounters first a weak field lens, which is the vacuum window of the dewar. The science beam is separated from the WFS beam by a narrow pickoff mirror located at the position of the telescope focal plane. The Offner relay optics reimage the focal plane onto the slit. More important, it forms a pupil image where a cold stop is erected. Prior to the slit there is a pair of filter wheels for defining the diffraction orders passed by the instrument. From the slit the light goes to an off-axis paraboloid which collimates the light. The collimated beam is dispersed in a direction along the slit by one set of selectable dispersers (on the “prism” turret, which includes a simple mirror for no cross-dispersion). The beam then passes to a set of selectable gratings (on the grating turret) which disperses the light in the direction perpendicular to the slit Finally the collimated beam is brought to a focus on the detector by one of four cameras on a camera turret.

For field acquisition, a flat mirror is inserted just in front of the cameras, intercepting the light from the collimator before it is dispersed. This permits viewing the field without disturbing the dispersing elements for increased speed and reproducibility.

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Optical Layout

Prism turret

Grating turret

Pickoff mirror

Slit

Camera (short)

Collimatorf.l. 1494 mm

Detector

Window

Offner Relay Filter Acquisition mirror position

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Foreoptics

The purpose of the foreoptics is to reduce the level of background radiation in the instrument.

The Offner Relay reimages the telescope focal plane onto the slit, achromatically, 1:1 and with a very low level of aberration. The combination of the entrance window of the dewar (which is a weak lens) and the primary of the Offner (in first pass) makes an image of the aperture stop of the telescope (the secondary) on the secondary of the Offner.

At the secondary, a black, circular, baffle is erected to suppress light from outside the telescope beam. Additional baffles will be erected before and after the secondary to further suppress out-of-beam light. On the second pass off the primary, the beam is restored to telecentricity. This has the important result that the next image of the pupil in the spectrograph falls one focal length from the collimator mirror, where it is convenient to place the gratings and other dispersers.

Cold filters before slit restrict optical bandwidth entering spectrograph, for order-sorting and suppression of out-of-band radiation.

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Foreoptics To OIWFS

Cold StopOffnerRelay

SlitPlane

Entrance windowPickoff

Fold mirrors

Filter

primary

secondary

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Gratings and Prisms

Two turrets hold sets of gratings (3) and cross-dispersers (3, plus a mirror) to provide several dispersing modes, allowing the user of the instrument to make tradeoffs between:

Spectral coverage vs resolution Slit length vs spectral coverage (cross-dispersion)

as well as to add a simple capability for polarimetry Prism turret:

Prism – for short camera; spectral resolution 1800 Prism – for long camera; spectral resolution 1800 Wollaston prism (for polarimetry) Mirror – for long-slit spectroscopy (100 arcsec with short camera; 50 arcsec with long)

Gratings: 10.44 l/mm - (R= 590 short camera, 1770 long camera) 31.7 l/mm - (R = 1800 short camera, 5500 long camera) 110.5 l/mm - (R = 6000 short camera, 18000 long camera)

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Gratings

Grating Long Short10.44 l/mm 1770 59031.7 5500 1800110.5 18000 6000

Resolution

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Prisms

7th

6th

5th

4th

3rd

1024 pixels

.87u

.94

1.10

1.32

1.65

2.202.37

Order:

Long Blue camera; cross-dispersed

Cross-dispersion options:

•Prism for short blue camera•Prism for long blue camera•Wollaston prism•Mirror for long-slit work

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Cameras

Four cameras are provided: 2 long for high spatial resolution (2 pixels matched to 0.1 arcsec

slit); optimized for 0.9-2.5 and 3-5 microns respectively. 2 short for lower spatial resolution (2 pixels matched to 0.3

arcsec slit); longer slit and most importantly, higher throughput under conditions of poorer seeing; again, optimized for shorter and longer wavelengths respectively.

The long cameras (1305mm focal length) must be folded to make them con-focal with the short cameras.

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CamerasTwo short cameras, 0.9-2.4 microns,3-5 microns. 0.15 arcsec / pixel

Two long cameras, 0.9-2.4 microns,3-5 microns. 0.05 arcsec / pixel

1 meter

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Design Performance

Post-slit opticsPercent degradation of rms image diameter, as measured on detector:

Allocated to: Allocated to: surf. tilt/wedge decentertotal (rad.,irreg.) [degrees] [mm]

Collimator 2.6% Fabrication 1.3% 2.0% 0Assembly 1.4% 0.0% 0.008 0.1

Prism 1.0% Fabrication 1.0% 1.0% 0Assembly 0.0% 0.0% 0 0

Grating 1.0% Fabrication 1.0% 1.0% 0Assembly 0.0% 0.0% 0 0

Camera 3.6% Fabrication 2.7% 1.0% Assembly 2.3% 0.0% 0.0058 0.02

Total (RSS) 4.6%Requirement 5%

Evaluated at 1.2 microns. Worst case camera, grating and cross-disperser is used.

------worst case-----

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Design Performance Wavelength coverage: 0.9 - 5 microns Field of view:

– 50 arcsec slit with long camera (6 arcsec cross-dispersed)– 100 arcsec with short (10 arcsec cross dispersed)

Spectral resolution 600 -18,000 Imaging: <5% degradation (>85% of light in 27 micron pixel) Throughput: at 2.2 microns, peak, with long camera and 10.44 l/mm

grating: >54% with detector

>60% without detector

94

Materials

Transmissive cameras: use barium fluoride, calcium fluoride and SF6. All well characterized in IR and at low temperatures (we contracted the measurement of CTE and index of SF6 data at low temperatures).

Powered mirrors (Offner and Collimator) are diamond-turned Alumiplate on aluminum for athermal optical performance and very low scattered light.

Flat mirrors are on glass substrates which are economical and have unsurpassed surface regularity and smoothness. (Typical reflectivity 99%)

Coatings: The diamond turned reflectors are all coated with protected Au (for robustness). The glass mirrors are bare gold coated. The transmissive optics are all coated with multi-layer anti-reflection coatings. (Typical average transmission: 98% per element)

95

Materials

Transmissive cameras Diamond turned Offner and Collimator Flat mirrors: Glass Coatings

96

Stray Light

We aggressively reduce extraneous sources of light. This topic may be revisited in the discussion of the thermal design, but it is convenient to summarize the various approaches being used: Low operating temperature (<65K) Scattered light:

No obstructions in beam to scatter Low-scattering surfaces Baffling will be based on scattering analysis

Cold motors to eliminate feedthroughs from ambient temperatures (and active removal of heat evolved by motors)

Thermal stationing of electrical feedthroughs No light leaks:The entire low-temperature portion of the spectrograph from the pickoff mirror to

the detector will be enclosed in a nearly isothermal enclosure at <65K. Joints will be baffled by a labyrinth construction. Path for vacuum pumping interior of instrument will be provided for. The cold, light-tight enclosure will be thoroughly light-leak tested at room temperature.

97

Stray Light

Low operating temperature (<65K) Scattered light:

No obstructions in beam to scatter Low-scattering surfaces Baffling will be based on scattering analysis

Cold motors to eliminate feedthroughs from ambient temperatures (and active removal of heat evolved by motors)

Thermal stationing of electrical feedthroughs No light leaks!

98

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99

Mechanical Design

• Structural Design (Goble)• Mechanism Design (Muller)• Handling (Elias)• Thermal Design (Elias)

100

OIWFS field lens

Lens group

Gimbal mirror

OIWFS Filter wheel

Entrance Window

Pick off, Focal plane # 1

Offner relay

Filter wheels

Decker slide

Collimator

Camera turret

Detector, Focal plane # 4

Prism turret

Grating turret

Long cam fold flats

Flip mirrornot shown

Slit slideIFU’s, Focalplane # 2

OIWFS Detector groupFocal plane # 3

Internal Mechanical Configuration

101

Previous view looking from the bottom

102

RequirementsGravity flexure

Thermal conductionThermal expansion

StressDynamic loading

Temperature

Strategy Material selection

Select fabrication processMaintenance access

Structural Design Procedure

Consider heat flowSteady state

Define structural geometryMechanical desktop solid Simple design rules

Thermal ModelNASTRAN Model

StructuralThermal stress

CompleteDesign

Start

103

Requirementsfor Structural

design

Gravity flexureAlignment to telescope

+/- 620 micro radApplies to instrument rigid

body motion+/- 1 micro rad for summed

effects of thermal andflexure on optical bench

Thermal conductionSteady state temperaturegradients < 1 degree C

Thermal expansionMatch expansion of thematerials in assemblies

Temperature60 Kelvin bench

30 Kelvin detector

StressLow in bench <300psi

for gravity loading1.5 yield margin onhandling of 20 g

Dynamic loadingTransportation

HandlingCryo head vibration

104

Structural Design Strategy

• More flexure of Instrument support is allowed because of the OIWFS, tilt < +/- 0.62 mrad. Optical bench must be very stiff, displacement of the image on the detector < 2.7 micron for 15 degree change in gravity vector, ~+/- 1 microrad

• Central Dewar bulkhead supported on trusses, incorporates mechanical, electrical, and thermal interfaces; Dewar end caps have minimal complexity to reduce weight, fabrication cost, and allow access to the bench parts

• The optical bench is a three dimensional Aluminum casting. Structure is divided at the optimum places, Offner, forward bench, center bench, aft bench. The internal bulkhead truss connects to the center casting.

• Boxes that contain the mechanisms are the structure thus saving weight and enhancing heat transfer.

105

Structural Design Strategy

• Mounting flexure vs Bench flexure• Use of trusses• Central bulkhead for all interfaces• Three dimensional Bench• The Box is the Structure

106

Bench Support

A set of 6 G-10 spokes between the Dewar bulkhead and the center bench casting supports two lateral degrees of freedom and twist about optical axis. Rigidity, ~ 60 Hz lateral resonance, more FEA later Thermal expansion compensating geometry Low thermal conduction, space between used for wiring,

cryo system, and radiation shield support Set of 3 G-10 support flexures constrain the focus translation,

and tilt about X and Y. Design provides mount of bench while cold and also can be

used to hold bench for maintenance while the cover is removed from Dewar

107

Optical Bench Support

Front cover side Rear cover side

Bulkhead casting

Cryo-coolerpair G-10 fiberglass spokes

support laterally andtwist

G-10 flexuressupport tiltsand focus

Center benchcasting

108

Main Bench Assembly

Center section supported on Dewar bulkhead with truss; truss design to compensate for material contraction on cool-down

Bench is totally closed to light except for entrance window. There is a pumping port, opened by the acquisition mirror drive, to be used during cool-down. Bulkhead will have a permanently mounted Turbo pump to be used during temperature transitions

Enclosed volume is connected boxes (mostly of Aluminum castings) designed to fit around the mechanisms

Most mechanisms are inside with access covers Outside parts are:

Drive motors, shafts have light baffles, cold stationed to first cooled radiation barrier (except for 2 OIWFS motors)

OIWFS gimbal mirror Camera/focus/detector assembly

109

Optical Bench, front view

Front bench

Offner

Dewar windowlocation

Support truss,lateral flexuresnot shown

All drive motors are cold

Detector andFocus are outside

Camera access,cover not shown

Bench center section

OIWFS bench

Gimbal mirror driveis outside

Aft bench castingnot shown

Long camera folds,cover not shown Collimator

cover

Pickoff

110

OIWFS Assembly

Main OIWFS components mount on sub-plate Includes all components except field lens (that is, combination lens

group, gimbal mirror, filter wheel, Shack-Hartmann/detector assembly)

Allows external alignment of critical components OIWFS can be removed and tested or worked on without loss of

alignment; this can be in parallel with other GNIRS work

111

OIWFS Bench

Bench box casting attaches to the center section with screws

Cover and elementmounting base

Gimbal mirrorassembly mountedon outside

Field lensmounted inforward bench,bench not shown

Center sectioncasting

Collimator/Cameralens group

Filters, drive motorinside

Focus stage,drive motorinside

Detector assy,only the lensesshown

112

Pre-Slit Optics

Pick-off mirror spans the field of view with 3 point mount at edges. Two points on one end, one on the other.

Offner entrance fold mirror is 3 point mounted. The points are on the front side of the mirror.

Offner primary and secondary mirrors are Diamond turned 6061 Aluminum with Alumiplate surface. Structural housing is also 6061 Aluminum.

Exit fold mirror is also mounted to three points on the front surface.

Assembly can be tested as a unit.

114

Spectrograph Bench

The slits and IFUs are supported in the forward bench casting which is not shown in the picture.

Aft bench is the only structural part of the system not enclosing optics. Its function is to support the collimator mirror in a cantilevered manner.

Collimator mount has a cover over the mounting details. The 3 blade flexure mounting is shimmed for adjustment.

Prisms are mounted on a turret with a horizontal bearing axis. The spindle is shown but the mount lugs are not.

The Gratings are mounted on a turret with a vertical axis. One drive does the swap and the variable tilt. The axis being orthogonal to the prism axis allows the non-detented drives to compensate orthogonal alignment.

The acquisition mirror is being designed to rotate up into position from below. Not shown in the picture. The drive will incorporate over travel to open a 100 mm diameter pump hole.

The long cameras use the same two stationary fold flats. Detector mounting and focus is being designed. The focus drive range will be 16

mm to allow testing warm with a different chip. The alignment on the stage will be done using a shim. Cold strapping and thermal control of the detector is the same as our other Aladdin mounts.

115

Spectrograph Bench

Slit Focus

Prisms, 3 plus aflat mirror on turret

Gratings, 3on turret

4 Cameras, red &blue, short & longon turret

Aladdin detector,on a focus stage andlight sealed with bellows

Long camera foldflats are stationary

Bench centersection

Bench aft sectionnot shown

Collimator mirrormount, cover notshown

Acquisition mirrornot shown

116

Front Cover Access

All of the pre-slit optics, the prism turret, the OIWFS field lens, and cold heads are accessible from the front cover end of the instrument. Any extended service time such as removal of the forward bench also requires back cover removal first to remove the Aladdin Chip for safe vacuum storage. Servicing the cold heads is possible by removing only the front cover as long as the instrument was back filled with dry N2, the valve is closed, and a temporary cover is used on the optics input hole.

The Offner can be directly removed if needed. Filter wheels are changed by removing the assembly from the side of the forward

bench and then swapping filters. Filters are pre-mounted in filter cells. Decker slide, slits, and IFUs are serviced by first removing the assembly from the

other side of the forward bench and disassembly as required. Motors are mounted outside so therefore are accessible, however the gears and

bearings are inside on each assembly. Prism turret work will require first removing the forward optics bench from the

bench center section. Cryo-head replacement requires disconnection inside before extraction from the

Dewar bulkhead.

117

Front Cover Access

Prism turret

Front bench

Offner & Pick-off

Filter wheels

Slit & Decker slide

Cryo-coolers

118

Rear Cover Access

All other parts, LN2 pre-cool assembly, wiring, gratings,OIWFS, cameras, collimator mirror, acquisition mirror drive and valve, and detector/focus are accessed from the rear cover.

Collimator mirror mount is made so that the mirror could be removed for coating without need for realignment.

Camera turret can be removed from the bench as a unit or each camera can be taken out individually.

Detector can be removed while leaving the focus stage attached. Grating turret is on a sub-plate that is the cover. The center of the turret has a

guide pin so that the gratings cannot bump the center section during insertion. OIWFS parts are mounted onto the OIWFS bench cover plate. First the plate is

removed and then the bench can be detached from the center section. The gimbal mirror can be removed without disturbing the bench.

Acquisition mirror, cooling vacuum valve and pumpout port, are a unit mounted on another plate that forms the cover on the bottom of the center section when installed.

The rapid cool LN2 pre-cool assembly is clamped to the top of the center section with fill, vents, and valves passing through the bulkhead directly above (not shown).

119

Detector, removal is alwaysneeded to protect it duringopen periods

Cameras, access covernot shown Collimator mirror,

cover not shownGrating turretthrough bottom

Wiring and connectorsthrough bulkheadnot shown

Long camerafold mirrors

LN2 coolernot shown

Aft bench castingnot shown

OIWFS sub-plate formscover of OIWFS benchwhich is removable

OIWFS Gimbalmirror on outside

120


121

Mechanism Design Flow Chart

RequirementsRepeatabilityLifeSpeedTemperature & Vacuum

RequirementsRepeatabilityLifeSpeedTemperature & Vacuum

StartStart

Select Mat’l & PartsThermal ExpansionWear ratesLubrication

Select Mat’l & PartsThermal ExpansionWear ratesLubrication

Calc Gear RatiosCalc Gear Ratios

Pick Design ConceptWarm or cold motorsDetents or notEncoders or notStepper or DC motorsControl friction?Home switches?Limit switch strategy?Backlash compensation?

Pick Design ConceptWarm or cold motorsDetents or notEncoders or notStepper or DC motorsControl friction?Home switches?Limit switch strategy?Backlash compensation?

Kinematic AnalysisMathcad calculation

Kinematic AnalysisMathcad calculation

Prototype TestPrototype Test

Qualified DesignQualified Design

DesignSolid model

DesignSolid model

122

Mechanism Design Concepts Use cold stepper motors. No feed through shafts. Concerns about light leaks

around shafts eliminated. Control of heat and radiation from motors requires attention.

Cold motors simplify mechanical design. Open loop control. Count steps from home position to desired position.

Simplifies control algorithms. Reliable and proven. Open loop control simplifies design. No ratchets, detents. Always drive mechanism to final position from one direction to remove backlash.

Positioning from opposite direction requires over-travel and reverse maneuver. Mechanical datum switches define home positions. Datum switch assemblies

contain 2 switches for reliability. Turrets are balanced to prevent motion induced by gravitational vector changes. Friction brakes hold turrets in position against backlash and dynamic forces. Use small, low-torque motors with large gear reductions to meet positioning

requirements and provide required drive torque for large mechanisms. Current limiting can provide mechanism protection plus reserve torque if needed.

123

Mechanism Design Concepts

• Linear & Rotary Mechanisms• Cold Motors• Open Loop Control• Redundant Datum/Limit Switches• Friction Brakes• Small Motors + Gear Reduction

124

Table 1 - Drive Gear RatiosMechanism Range

oftravel

Repeatability

Type ofDrive

Gear ratio ½ motorstep

Range(steps)

Filter Wheel 1&Filter Wheel 2

Infinite 3.7 mrad Ring &Pinion

312/15, 24pitch

0.76mrad

4160/turn

Decker Slide 10 in 50 micron Rack &Pinion +Gearreduction

.4375 Pitchdia + 2/1gear

43.6micron

2910

Slit Slide 11.75 in 1 micron Screw +WormGearreduction

0.2 inchpitch + 30/1worm

0.423micron

352,500

AcquisitionMirror Slide

6 in 50 micron Rack &Pinion +Gearreduction

.4375 Pitchdia + 2/1gear

43.6micron

1746

Prism Turret 300 deg .037 mrad Worm +Gearreduction

180/1 worm+ 2.5/1 gear

.035mrad

75,000

Grating Turret 300 deg .037 mrad Worm +Gearreduction

180/1 worm+ 2.5/1 gear

.035mrad

75,000

Camera Turret 340 deg .07 mrad Worm +Gearreduction

180/1 worm+ 2.5/1 gear

.035mrad

85,000

DetectorFocus Stage

0.75 in 6 micron Screw + Gearreduction

0.2 inchpitch + 3/1gear

4.23micron

2250

GEAR DRIVE RATIOS FROM SDN0002.13

125

Mechanisms• Linear

– Decker Slide– Slit Slide– Detector Focus– Environmental Cover (external to instrument)

• Rotary– Filter Wheel (2)– Prism Turret– Grating Turret– Camera Turret– Acquisition Mirror

126

Slit/Decker Module

Example of a linear mechanism (similar concept used for decker slide and focus drive)

Module view shows location of slit slide (and decker slide) Key points:

Slit slide runs on rollers, spring loaded. Motor is thermally de-coupled from mechanism to minimize heat and

radiation effects Prototype of a linear mechanism will be built and tested to minimize risk

128


130

Gear Drive

Inverted ACME Screw/Nut Design Long Nut (Stretch nut and cut in half) Short Screw Athermal design

Drive Details Initial reduction with worm/wheel (Vespel/brass) Final reduction with linear nut, split screw (Vespel/Al) Split screw reduces backlash, final positioning in standard direction can limit

it further Use Vespel for minimum wear

132

Slit Slide Assembly

Slit Slide Assembly Shows location of pockets for 2 IFU modules, including datum locations for

assembly Shows slit module and its location

134

Removable Slit Module

Slit Module Assembly Holds slit plate, pupil viewer lens (other lenses in filter wheels) Slit plate manufactured as a unit, provides precise control of slit-to-slit

alignment Slit plate can be replaced in future if needs evolve

136

Grating Turret

Rotary mechanism. Similar design used for prism, camera turrets, filter wheels and acquisition mirror.

Rotating part moves <360 degrees, holds 3 gratings Large central post, two bearings define position Friction brake plus final motion in standard direction eliminate backlash

Same axis of motion is used for both grating selection, tilt (requires slightly longer gratings, small motions of footprint on cameras, both effects limited by design).

Motor thermally de-coupled from mechanism support, can be shielded to eliminate thermal, radiation effects.

Entire mechanism mounts on sub-plate that bolts to bench Permits external alignment and test Removal and installation without loss of overall alignment (installation to machining

tolerances is sufficient) Adjustments provided for individual grating alignment (needed to co-align rulings). Drive is initial gear reduction plus final worm/wheel reduction. Prototype of a rotary mechanism will be built and tested to minimize risk shown.

138

Home Switch and Parking Brake

All mechanisms requiring precision positioning use a repeatable, redundant, parallel spring flexure home switch.

Use on filter wheels, decker and slit slides,prism, grating, turrets, and detector focus. Home switch will be tested to characterize repeatability.

Friction brake used on rotary mechanisms. Final drive worm wheel will also serve as a brake disk.

140

Configuration Management Tools

Established Database based on experience gained on 2 previous successful instrumentation projects.

Use database to define drawing/assemblies, track progress of part from design/ draft through fabrication and final assembly.

Engineer defines Drawing Breakdown Structure (DBS) and assigns tasks to designers/drafters.

Compare budgeted weight with calculated/measured weight and adjust budget accordingly.

Tool to flag over budget conditions early so that corrective action can be taken. Make status reports for on a periodic basis for status meetings. All mechanical designs are being solid modeled. Reduces errors and increases

confidence. Extract mass properties from solid models. Weight, CG, Moments of Inertia. Solid model files named per DBS.

141

Configuration Management Tools

• Microsoft Access Database– Drawing Breakdown Structure (DBS)– Weight Budget– Project Tracking– Customize Database as needs evolve

• Autodesk Mechanical Desktop– Solid Modeling– Mass Properties– Interference checking– Produce 2D fabrication drawings

143

Handling complies with Gemini interfaces

• Instrument can be installed in up-looking or horizontal position

• Provides proper interfaces to Gemini handling equipment (cart, hoists)

• Interface to ISS similar to Gemini ballast weight assemblies (better locating features needed)

144


145

Thermal Design

• Meets Gemini cool-down requirements• Provides optical stability for OIWFS and for

camera and collimator focus• Meets Gemini warm-up requirements

146

Instrument Cool-Down

Liquid nitrogen pre-cool system Accelerates cool-down to ~80K Can be by-passed Recommended by review committees

4 cryocoolers Required for cool-down from 80 to 60K Supplement pre-cool; can be used alone

Cool-down meets 4-day Gemini requirement Cool down with cryocoolers alone close to 4 days

147

Instrument Cool-Down

• Liquid Nitrogen Pre-Cool• 4 Cryocoolers• Meets 4-day Gemini Requirement

148

Thermal Stability and Control

Radiation shield design minimizes thermal gradients in optical bench Main effect of gradients in current design is on collimator and OIWFS focus Baseline design is 2 “floating” shields, 1 active shield Use of MLI possible (either as thermal or weight risk mitigation)

Active thermal control of bench required Without control, will see temperature variations due to variations in ambient

temperature, motor use (and control protocols) and in cryocooler performance

Temperature control is needed to ensure stable performance of OIWFS (ability to maintain guide star on slit) -- recommended by ICD

Temperature control also simplifies software control of camera focus (would otherwise need a correction for bench temperature)

149

Thermal Stability and Control

• Radiation Shield Design Minimizes Gradients• Active Thermal Control of Bench Required

150


151

Instrument Warm-Up

• Distributed Heaters Provide Rapid Warm-Up• Stand-Alone Control Box Provides Off-Line

Warm-Up• Warm-Up Meets 1-Day Gemini Requirement

152


153

Dwg #89-NOAO-4201-5025 (postscript),

shown here in book

Title: Instrument External Cabling diagram

B-sized copy in review books (hardcopy)

A-sized viewgraph for R. Rvw is used

(for reference only)

154


155

GNIRS ELECTRICAL DESIGN

System Overview Control Architecture Electrical Packaging

Spectrograph Controller packaging Thermal Enclosure

ALADDIN Detector Controller packaging Thermal Enclosure

156

GNIRS ELECTRONIC CONTROL ARCHITECTURE

Dewar Warm Up

ALADDIN Array Controller

Manual Setpoint

Mechanisms

Dewar Thermal Control

Mechanisms (motors,limit and homeswitches)

Gemini LAN's

Temperatures

Data Processing

Spectrograph Ctlr

Dewar Health

OIWFS Mech Ctlr

Detector Controller

Cryocooler Control

THERMAL ENCLOSURE #2

Detector ThermalControl

A&G SDSU VME I/F

Manual Control

Detector ThermalControl

THERMAL ENCLOSURE #1

Vacuum

OIWFS DetectorController (SDSU)

(on dewar)

(data &control)

(control LAN)(data/control fiber)(control LAN)

CISCO PORTSWITCH HUB

157

Instrument Sequencer Controls Three Subsystems

• Spectrograph Controller, Thermal Enclosure #1

• OIWFS Controller, Gemini-furnished, Thermal Enclosure #1

• ALADDIN Array Controller, Gemini-furnished, Thermal Enclosure #2

158


159


Title: Spectrograph Control schematic Block Diagram

shown here:

B-sized copy in review books (hardcopy)

A-sized viewgraph for R. Rvw is used (this viewgraph

is for reference only - isn’t shown initially)

160


161

Spectrograph Controller Architecture is Complete

Addresses all Gemini interface requirements All major functions identified

Mechanism control Cryocooler control Dewar thermal control Dewar health (vacuum/temp sensing)

All individual cards identified All control interfaces defined Dewar wiring, cable/connector pinouts remain

162


163


Spectrograph TE Layout, Power,

Grounding schematic

shown here:

A-sized copy in review books (hardcopy)

A-sized viewgraph for R. Rvw is used

164


165

Electronics is Containedin Two Cabinets

Spectrograph Thermal Enclosure Array Controller Thermal Enclosure Additional External Electronics mount on dewar

Set by detector requirements ALADDIN preamp OIWFS SDSU2 controller

Stand-alone warm-up controller box

166


167

Sub-System Integration

3 Externally Provided Sub-Systems: IFU OIWFS Array Controller

168


169

IFU Provided by University of Durham through

IGPO Two modular sub-assemblies

Aligned and tested prior to installation Space provided on slit slide Installed and aligned to datums, following ICD

Final alignment check during GNIRS integration

170

OIWFS

Provided by IfA, Hawaii through IGPO. Includes optical components and sub-assemblies, packaged controller, electronics boards and subassemblies, test cables, software, alignment and test procedures

Optical components and mechanisms mount on modular bench assembly Optical component integration ties to ICD, includes alignment procedures and

tolerances Electronics require wiring and cabling within GNIRS Electronics require installation of controller hardware, which includes Leach

(SDSU2) controller mounted on dewar bulkhead structure and components controller mounted inside instrument thermal enclosure

Testing capability limited to low-level tests (supplied by IfA); essentially limited to functional testing of devices and detector. This is sufficient, in principle, to check instrument flexure (OIWFS to slit).

171

OIWFS• Provided by IfA, Hawaii through IGPO• Opto-mechanical assemblies mount on bench

structure• Requires integration and alignment of

assemblies• Requires installation of controller hardware,

wiring and cabling• Limited testing of capability

172


173

Array Controller

Provided by NOAO through IGPO Requires integration of hardware

Detector Pre-amplifier Thermal enclosure Wiring and cabling

174

System Integration & Test (1)

Critical Assumptions: Sub-systems can be tested externally and independently. These

tests include tests of mechanism flexure, cold tests of functionality (repeatability, torque requirements). Alignment of components within mechanism or modules, where required, can also be done externally (e.g, gratings within turret).

Minimize alignment procedures. This implies design of appropriate interfaces (and proper location) so that assembly tolerances are controlled and are sufficient to meet alignment requirements.

175


Critical Assumptions External Tests and Alignment of Sub-Systems Minimize Alignment

176


Integration and Alignment Plan Sub-systems are assumed to have been “pre-tested” and to have

their optics aligned (if required); system test is therefore primarily a test of the instrument as a whole and not of functionality of individual mechanisms.

Testing vacuum and thermal systems is carried out in two stages and precedes testing of the complete instrument in order to isolate any problems in these areas as early as possible.

Assembly and warm test of the bench with mechanisms provides access for diagnosis. It includes testing for light leaks.

Final integration and cold testing covers full instrument functionality (partial for OIWFS).

177


Integration and Alignment Plan Sub-systems “pre-tested” Test vacuum and thermal systems Assemble and warm test bench Integrate and cold test

178


179

System Integration & Test (3) System Tests Include:

Functionality Repeatability Flexure Thermal (cool-down, warm-up, stability, gradients) Optical (image quality, background [light leaks and

scattering], throughput) Configuration characterization

180


181

SECTION VII

Risk Identification and Mitigation Plan

182


183

Risk Items Risk Items pointed out by the Committee

Thermal (Instrument cool-down and thermal gradients)

Optical (Focus control, alignment procedures, mirror finish, light leaks)

Handling OIWFS Integration and Alignment IFU Integration

Additional Risk Items Software OIWFS performance Mechanism repeatability

184

Risk Mitigation TableImpact = Consequence of Failure on Science Productivity of InstrumentRisk = Probability of Failure Despite Mitigation Plan

Current Item Impact Mitigation Plan

1 Thermal

-Long Cooldown Time LOW LOW Central Positioning of CryocoolersLN2 PrecoolActive Thermal Bench ControlReduced Cold Mass

-Temperature Gradients MEDIUM LOW Central Positioning of Cryocoolers and Stability Active Radiation Shield

Minimize Bolted JointsAbility to Cold Strap CryomotorsActive Thermal Bench Control

2 Optical

-Detector Focus HIGH LOW Detector Focus MechanismActive Thermal Bench Control

-Optical Alignment MEDIUM LOW Cleaner Optical Design (fewer folds)Modular MechanismsSub-system Alignment outside GNIRSSimplified Alignment ProcedureDetector Focus Mechanism

-Diamond Turned Mirrors MEDIUM LOW Now only 3 Diamond Turned MirrorsGlass Substrate Flat Mirrors

Areas of Concern Risk Level

185

Current Item Impact Mitigation Plan

-Radiation Shield Gaps HIGH LOW Internal Motors (no feedthroughs)Spectrograph Completely Enclosed by Bench Structure

3 Handling MEDIUM LOW Instrument Conforms to Gemini InterfacesBulkhead Design Leads to Easier Assembly/Alignment

4 OIWFS

-Assembly/Alignment MEDIUM LOW Now Essentially Independent ModuleUse IfA Layout (except 2 fold mirrors)ICD Complete

-Performance MEDIUM HIGH Active Thermal Bench ControlOperational Alternatives with PWFS

5 IFU

-Assembly LOW LOW ICD Nearing CompletionRepackaged as Self-Contained Units, Install in Slit Mechanism

-Performance MEDIUM HIGH Only IFU Operation Affected

6 Mechanisms MEDIUM MEDIUM Prototype Linear/Rotary MechanismsCold Test of Critical Functions on Prototype (cooldown, torque, repeatability, absolute positioning, flexure)Cold Test Completed Mechanism

7 Software MEDIUM MEDIUM Engineering Test Software Developed for Integration/TestingInstrument Can be Tested Without Gemini Software

Areas of Concern Risk Level

Risk Mitigation Table (cont)

186


187

Risk Mitigation Plan

Risk Mitigation Table Prototyping of mechanism drives Mechanism testing

188


189

SECTION VIII

Conclusion

190


191

Summary

• We have presented the current status of the project and engineering design

• NOAO has put into place the required engineering team and management structure

• GNIRS is a new design configuration which addresses committee concerns and risks

• We have the required resources in place • The GNIRS instrument will deliver in mid-2002

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