INTRODUCTION TO AOCS HARDWARE AND GPS

Paripat Pairat

Updated (05/04/2021)

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Introduction to AOCS Hardware

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Topic

• What are the ADCS and AOCS?

• A0CS Hardware

• AOCS Engineer for SPACE Mission

• Design and select AOCS Equipment

• AOCS Equipment List

• Process Flow

• AOCS Hardware Verification process

What are the ADCS and AOCS?

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ADCS DefinitionAttitude Determination and Control System (ADCS)Terminology by Olivier L. de Weck

• Attitude Determination : Real-Time or Post-Facto knowledge, within a given tolerance, of the spacecraft attitude

• Attitude Control: Maintenance of a desired, specified attitude within a given toleranceF. Landis Markley and John L.Crassidis described as

“Spacecraft attitude determination and control covers the entire range of techniques for determining the orientation of a spacecraft and then controlling it so that the spacecraft points in some desired direction”

Ref.1 Attitude Determination and Control (ADCS) Olivier L. de Weck p.5

Ref. 2 F. Landis Markley and John L.Crassidis, Fundamentals of Spacecraft Attitude Determination and Control (2014) p.1

What is ADCS and AOCS?

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AOCS DefinitionAttitude and Orbit Control System (AOCS)

AOCS stands for Attitude and Orbit Control System, ECSS-E-ST-60-30C provides a formal definition:

“Functional chain of a satellite which encompasses attitude and orbit sensors, attitude estimation and guidance, attitude and orbit control algorithms, attitude and orbit control actuators”.

Ref.3 Gavin Johnston_AOCS Customer Engineer Training_2019-2020

Ref.4 http://www.s3l.be/usr/files/di/fi/2/Lecture13_ADCS_TjorvenDelabie_20181111202.pdf

Attitude (Rotation)

• Angular Momentum

• Motion relative to center of mass

Orbit (Translation)

• Linear momentum

• Motion of the center of mass

Note: The European Cooperation for Space Standardization (ECSS)

AOCS Team

5Credits & Ref.5 David Feltham_Theos-2 AOCS Hardware Course _2019-2020

AOCS Team

– Overall ownership and responsibility of AOCS delivery

– Defines requirements for the equipment and position in the S/C according to

mission requirements

– Tests the AOCS suite as a sub-system

AOCS Equipment Team

• Designs according to requirements

• Monitors and supervises manufacturing

• Tests according to requirements

• Delivers to the AOCS Team

• Supports AOCS Team acceptance and validation campaign

• Supports Spacecraft environmental tests

• Supports Spacecraft commissioning and operation

Mission of A0CS requirements: Earth Observation

Typical pointing from 0.01 to 0.1 degrees. Angular rate stability for imaging < 1 millidegree/sec On-ground post processing of AOCS data (image processing and geolocation) Guidance – nadir pointing, target tracking, off-pointing.

ATTITUDE REQUIREMENTS AND ERRORS Earth Science Ref.4

Design and Selection AOCS Equipment

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Consideration of choosing this AOCS equipment is looking at the Technical, e.g. Accuracy and quality to meet

the requirement. Besides, the management factor is important such as supplier, pricing and lead time.

• Control Modes and Requirements

• Selection of S/C Control Type

• Effect of Control Accuracy on Sensor e.g. Accurate, pointing

• Required Accuracy e.g. 1 to 5 deg

• Quantify the Disturbance Environment

• Select and Size AOCS Hardware

• Define and control Algorithms

Design

• Technical

• Resolution and Accuracy

• Size, Mass and Power

• Limits or avoid

• Management

• Supplier

• Standard and Warranty

• Pricing

• Price and Performance, Procurement e.g. MOQ

• Time

• Long lead time item?

Selection

Principle of consideration

Ref. Attitude Determination and Control John S. Etemo, Ball Aerospace & Technologies Corporation

A0CS Hardware Engineer for SPACE Mission

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Design (PDR&CDR)

Design & Selecting process

• Design, Developing and verification plan: DDVP

• Detail Design Document: DDD

Manufacturing

• Build instruction

• Flight Assembly

Verification Process

• TVM

Module (MRR)

Specification document (COTs)

Equipment & Facility

Verification Process (Detail)

• TVM

• Test Procedure

Test (TRR)

Test & Report

• Test Procedure

• Report Template

Review Results Subsystem (TRB)

• Test report

• Calibration report

AIT & Spacecraft (ARR)

Initial Integration

Test & Report

Review Results

PSR

ON GROUND IN SPACE•AOCS Event Support

•GPS Event Support

The AOCS Hardware knowledge• Can use Electronic Measuring Instrument, the measuring tools and software such as data acquisition, instrument control. • Related to Attitude determine equipment following AOCS sensor and AOCS Actuator • Related to GNSS including radio signals e.g. Antenna performance and measurement, Network Analyzer • Electronic design or design FPGA and using the boundary scan (testing interconnects)

A0CS Hardware

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A0CS Hardware DefinitionThe AOCS hardware is equipment to use for Attitude and Obit Control System. Spacecraft attitude control is essential to meet mission pointing requirements.

AOCS Hardware divided into

• Sensors: To determine current attitude

• Actuators: To modify attitude as per operational mission requirements

Credit & Ref.5 David Feltham_Theos-2 AOCS Hardware Course _2019-2020

Sensors Actuator

Nano-SSOC-A60 analog sun sensor

A small reaction wheel https://en.wikipedia.org/wiki/Reaction_wheel

A0CS Hardware

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AOCS Equipment ListSensor

Sun Sensor Magnetometer Star Sensors Gyroscopes GNSSEarth/Horizon

Sensors Accelerometer Integrated Units

Credit & Ref.6 Professor Craig Underwood, SPACECRAFT SYSTEMS, 15th – 19th July 2019 (Lecture)Ref.7 Small Spacecraft Systems Virtual Institute, Ames Research Center, Moffett Field, California, NASA. State of the Art: SmallSpacecraft Technology. (2020).

Note: The Guidance, Navigation & Control (GNC) subsystem includes both the components used for position determination and the components used by the Attitude Determination and Control System (ADCS). (Ref.7)

Actuator

Momentum and Reaction Wheels

Magnetic Coils (Torquers)

Thruster Nutation DampersControl Moment

GyrosOnboard Computers

Processer

Performance of AOCS Equipment

AOCS Equipment Performance TRL

Propulsion Thrust range 10 μN to 260 N Unk-9

Reaction Wheels 0.0006 – 0.3 Nm peak torque, 0.005 – 8 N m s storage 9

Magnetic Torquers 0.1 A m2 – 15 A m2 9

Star Trackers 8 arcsec pointing knowledge 9

Sun Sensors 0.1° accuracy 9

Earth Sensors 0.25° accuracy 9

Inertial Sensors Gyros: 0.15° h-1 bias stability, 0.02° h-1/2 ARW Accels: 3 µg bias stability, 0.02 (m s-1)/h-1/2 VRW

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GPS Receivers 1.5 m position accuracy 9

Integrated Units 1 – 0.002° pointing capability 9

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Ref.7 Small Spacecraft Systems Virtual Institute, Ames Research Center, Moffett Field, California, NASA. State of the Art: Small Spacecraft Technology. (2020).

Table: The State of the Art for GNC Subsystems

https://en.wikipedia.org/wiki/Technology_readiness_level

AOCS Equipment List

Sun Sensors (SAS) are used to estimate the direction of the Sun in the spacecraft body frame. Sun direction estimates can be used for attitude estimation. Because the Sun is easily identifiable and extremely bright.

Function: The sensors determine the Sun’s Position relative to the unit for attitude

Key parameter ( Without Environment, mass & size, power)

• Accuracy : 0.1° to 5° (0.005 ° to 3 ° Ref.6)

• The field of view (FOV)

• Type of SAS: Analog or Digital and type of detectors

• Sun sensors cannot be used in eclipse.

Performance of Sun sensor

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Ref.6 Professor Craig Underwood, SPACECRAFT SYSTEMS, 15th – 19th July 2019 (Lecture)Ref.7 Small Spacecraft Systems Virtual Institute, Ames Research Center, Moffett Field, California, NASA. State of the Art: SmallSpacecraft Technology. (2020).

BiSon64-ET FM (drw-nr: 110T000)Credit: Lens R&D

AOCS Equipment List

Company Performance (°)

Type TRL

Adcole Space 0.1 to 5 Analog, Digital 9

Bradford Engineering 0.2 to 3 Analog Unk

CubeSpace 0.2 Digital 9

GomSpace 0.5, 2 Digital Unk

Lens R&D 0.5 to Unk Analog Unk

NewSpace Systems 0.1 to 0.5 Analog, Digital 9

Solar MEMS Technologies 0.1 to 5 Analog, Digital Unk

Space Micro 1 to 5 Analog 9

Some typical supplier of Sun sensor

12Technology Readiness Level (TRL)TRL 9 – Actual system "flight proven" through successful mission operations

Quadrant SAS NFSS-11 (0.1°)Credit: New space System

Coarse Sun Sensor Pyramid (5°)Credit: Adcole Space

Table: Small Spacecraft Sun Sensors

AOCS Equipment List

Magnetometer (MTM) are used as spacecraft attitude sensors to providing both the direction and magnitude of the Earth’s magnetic field.

Function: Measures the external magnetic field vector

Key parameter

• Resolution : nT/bit

• Field Measurement Range : ± µT (Earth 25,000 and 65,000 nT)

• Zero Field Bias : < ± nT

• Accuracy : moderate 1-5°accuracy

• Practically limits their use in this capacity to low-Earth orbit

Magnetometer: MTM

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AMR Magnetometer (10 nT/bit )Credit: ZARM

AOCS Equipment List

Company Resolution (nT) Model TRL

GomSpace Unk NanoSense M315 Unk

MEISEI Unk 3-Axis MTM 9

NewSpace Systems 8 NMRM 9

SpaceQuest Unk MAG-3 ($14,500) 9

ZARM Unk AMR Magnetometer Unk

Some typical supplier of Magnetometer

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Technology Readiness Level (TRL)TRL 9 – Actual system "flight proven" through successful mission operations

NanoSense M315 (15nT at 1 sigma)Credit: GomSpace

MAG-3 (Accuracy of ± 0.75% of Full Scale Credit: SpaceQues

Table: Three-axis Magnetometers for Small Spacecraft

AOCS Equipment List

Star Tracker (STR) or Star sensors measure star coordinates in spacecraft frame and provide attitude information when these observed coordinates are compared with known star directions obtained from a star catalogue. The STR is used as fine attitude sensors when Nominal Mode which consists of two units: Camera Head Unit and Data Processing Unit.

Function : Optical device that measures the positions of stars using a camera, Star Extraction > Star Matching

Key parameter

• Accuracy : Attitude accuracy = 1 arc sec to 1 arc min

1 arcsec is a 3600th of a deg or ~ 1m error over 200km

• Type : Scanner & Tracker & Mappers

• Performance : Noise Equivalent Angle(NEA), Relative Accuracy (RA),

Absolute Accuracy (AA)

Star Sensors: STR

15Credits & Ref.6 0255614 David Feltham THEOS-2 Star Tracker Lecture V002

CubeStar Credit: Cube space

AOCS Equipment List

• Noise Equivalent Angle(NEA): Is the Star Tracker’s ability to reproduce the same star position data provided the same optical conditions. This error is almost exclusively driven by the Hardware.

– Photon Count Statistics, Dark Signal/Noise

• Relative Accuracy (RA): Is the Star Tracker’s ability to produce attitude with respect to the Star Tracker’s internal reference under varying optical conditions. This error is dependent on the NEA, software algorithms, quality of calibration and the attitude of the spacecraft.

– NEA, Star Catalogue Error

• Absolute Accuracy (AA): Is the Star Tracker’s ability to produce attitude with respect to the Payload under varying optical conditions. This error is dependent on the RA, stability and accuracy of the calibration of the Payload and Star Tracker interface.

– RA, Thermo Elastic Distortion

Star Sensors Performance

16Ref.6 0255614 David Feltham THEOS-2 Star Tracker Lecture V002

Hydra's Optical Heads employ Active Pixel Sensors (CMOS)Credit: Sodren

AOCS Equipment List

Company Cross axis accuracy (3s) Model TRL

Adcole Space 5.7" MAI-SS Space Sextant 9

Ball Aerospace 1” CT-2020 9

Berlin Space Tech. 30” ST200 9

Blue Canyon Tech. 6” Standard NST 9

CubeSpace 55.44" CubeStar 9

Leonardo 7.7" Spacestar 9

Sodern 2” Auriga-CP 9

SSTL 10” Altair HB+ 9

Terma 3” HE-5AS 9

Star Sensors: STR

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Table: STR for Small Spacecraft

Developed for NASA’s Chandra X-ray Observatory led to our High Accuracy Star Trackers (HAST) Credit: Ball Aerospace

AOCS Equipment List

Gyros are inertial sensors which measure the speed or angle of rotation from an initial reference. Gyro is used for precision attitude sensing when combined with external reference such as Star tracker in e.g., Nominal Mode.

• Function : measure angular rate of s/c

• Accuracy : Gyro drift rate= 0.003 (°/hr) to 1 (°/hr)

• Type : Fiber optic gyros (FOGs) and Microelectromechanical systems (MEMS) gyros

(e.g., resonator gyros, ring laser gyros)

• Performance : Bias Stability(°/hr) , ARW (°/rt( hr))

Gyroscopes: GYR

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DSP-1760 Fiber Optic GyroCredit: KVH

AOCS Equipment List

Company Bias Stability(°/hr) Model TRL

Gladiator Tech. 1.200 G150Z (MEMS) N/A

KVH 1.000 DSP-3000 (FOG) Unk

L3 8.000 CIRUS (FOG) Unk

Northrop Grumman 0.050 µFORS-3U (FOG) Unk

Sensonor 0.300 STIM308 Unk

NovAtel 1.000 IMU-HG1900 (MEMS) Unk

Silicon Sensing Sys. 3.500 CRS03 (MEMS) Unk

SSTL 10.000 MIRAS-01 (IRU) (MEMS) Unk

Gyroscopes: GYR

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Table: GYR for Small Spacecraft

G-2000 gyroscopeCredit: Northrop Grumman

Unk = Unknow

AOCS Equipment List

• GNSS (Global Navigation Satellite System) is the generic term used to describe the global navigation market including GPS, Galileo, Glonass, Beidou etc

• The Global Positioning System (GPS) is a worldwide radio-navigation system formed from a constellation of multiple satellites and their ground stations.

• For low-Earth orbit spacecraft, GPS receivers are now the primary method for performing orbit determination, replacing ground-based tracking methods. Onboard GPS receivers are now considered a mature technology for small spacecraft.

• GPS units are controlled under the Export Administration Regulations (EAR) and must be licensed to remove COCOM limits.

What is GNSS/GPS?

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GNSS (Global Navigation Satellite System)

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Credit & Ref. Simon M. Presentation and Prof. Enge (video), wikipedia

GNSS is the generic term used to describe the global navigation market including

➢ GPS The United States' Global Positioning System➢ Galileo European Union➢ Glonass Russia➢ Beidou China➢ etc. Japan's Quasi-Zenith Satellite System (QZSS), NAVIC or NAVigation

with Indian Constellation, U.S. Wide Area Augmentation System (WAAS), European Geostationary Navigation Overlay Service (EGNOS)

Global coverage for each system is generally achieved by a satellite constellation of 18–30 medium Earth orbit (MEO) satellites spread between several orbital planes. The actual systems vary, but use orbital inclinations of >50° and orbital periods of roughly twelve hours (at an altitude of about 20,000 km. or 12,000 miles

Figure 1.Orbital information about

GNSS and other systems.

GNSS (2)

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Wikipedia 18Mar2021

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BeiDou3 Galileo GLONASS GPS NAVIC QZSS

Graph 1 Comparison of systems

Operational Satellites in orbit Plan

Figure 3: GPS, GLONASS and Galileo navigational frequency bands.

https://www.gpsworld.com/wp-content/uploads/2017/09/BCM47755-frequencies-W.jpg

Figure 2 BCM47755 uses two different frequency signals from each satellite. (Image: Broadcom)

GPS❖ Global Positioning System : GPS

❖ GPS uses these satellites as reference points to

calculate positions accurate to a matter of metres

❖ MEO 20,200 km. 24 sat (Now 31) 12 Hr

❖ GPS signals 2MHz signal at 1.575 GHz (L1) and 1.227GHz (L2) Newer Modernised (L1C, L2C, L5 signals 20 MHz encrypted Military L1P(Y), L2P (Y)

❖ DATA format: consists of 1500 bits divided into five 300-bit subframes. A data frame is transmitted every thirty seconds.

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Ref. Simon M. Presentation and Prof. Enge (video)

https://www.gps.gov/systems/gps/space/

• Navigation Sensor Output Position, Velocity & Time •Accurate Positioning / Orbit determination - 10 metres•Time: Better than 1 microsecond•Attitude Determination-Potential of 0.1 degrees

Figure 5. GPS receiver’s location

Figure 4. GPS fourth satellite is needed

https://www.quora.com/Why-are-four-GPS-satellites-required-to-locate-my-position

How does GPS Work?

( ) ( ) ( )uujujujj tcyyyyxx ˆˆˆˆˆ

222+−+−+−=

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Ref. Simon M. Presentation and Prof. Enge (video)

1. Known transmission time2. Known sat. location 3. Speed of Radio Wave (speed of light 3*10^8 m/s)4. Time of Arrival❖ Pseudorange measurements from four satellitesTo determine user position in 3D and the clock offset to requires 4 pseudorange measurements (from 4 satellites)- Satellite clock errors are transmitted in ephemeris data and so can be removed

Eq. 1 Pseudorange measurements from four satellites

Calculation of user position

https://www.quora.com/Why-are-four-GPS-satellites-required-to-locate-my-position

Eq. 2 satellite provides the information for one equation

Figure 6. Range form GPS

Figure 7. Times form GPS

AOCS Equipment List

Company Accuracy (m) Model TRL

APL 3 EGNS 6

Eurotech 1.2 COM-1289 Unk

General Dynamics 5 to 15 Explorer 9

Novatel 1.5 OEM615 9

SkyFox Labs 10 piNAV-NG 9

SSTL 5 to 10 SGR-Ligo, SGR-07, SGR10 5,9

GomSpace 1.5 GPS-kit Unk

Global Navigation Satellite System: GNSS

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Table GPS Receivers for Small Spacecraft

GPS Receiver piNAV-NGCredit: SkyFox Labs

GPS Receiver Explorer Credit: General Dynamics

AOCS Equipment List

Company Parameter Model TRL

SSTL LNA Gain 24 dB filtered2 dB LNA NF

00741-ASY/7 Unk

New Space System Noise figure <2 dB NANT-PTCL1 Unk

• Function: Active antenna with integrated LNA to provide the GPS receiver with Satellite data.

• Key parameter: Frequency for GPS is 1575.42 MHz, LNA, Return loss, Noise figure

GNSS Patch Antenna

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NANT-PTCL1Credit: New Space System

GPS Patch AntennaCredit: SSTL

Table: GPS Patch Antenna

AOCS Equipment List

Magnetic torquers or Magnetorquer (MTR) create a magnetic dipole moment which in turn creates a torque. The torquers are made of turns of wire in a loop of area by sending a current through such a coil produces a magnetic dipole moment of magnitude in a direction perpendicular to the plane of coil.

Function: Detumbling of s/c, dumping momentum of wheels.

• Performance : Magnetic Moment 10 to 4000 𝐴𝑚2

• MTMs are most effective in LEO where B ~ 30-60 mT but may be used all the way out to GEO

• Use of magnetic torquers beyond low-Earth orbit

Magnetic Coils (Torquers): MTR

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Hyperion Technologies B.V.MTQ200 magnetorquer

AOCS Equipment List

Company Peak Dipole (A m2) Model TRL

Adcole Space 0.15 Electromagnet 9

CubeSpace 0.13 to 1.9 CubeTorquer 9

GomSpace 0.31 Nano Torque GST-600 9

ISIS 0.2 Magnetorquer Board 9

MEISEI 12 Magnetic Torque Actuator 9

NanoAvionics 0.3 MTQ3X 9

Sinclair Interplanetary 15 to 48 TQ 9

SSTL 5 MTR-5 9

ZARM 0.1 to 15 MT Unk

Magnetic Coils (Torquers): MTR

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Table: High Heritage Magnetic Torquers

The results from Flux meter Credit: SSTL workshop

ISIS Magnetorquer Board (iMTQ)Credit: ISIS

Magnetorquer RodCredit: Newspace

AOCS Equipment List

Reaction wheels are essentially torque motors with high-inertia rotors. There are four wheels to control a vehicle, with the wheel axes aligned with the body principal axis. A fourth redundant wheel is carried in case one of the three primaries fails and to provide greater torque and momentum storage capability.

• Function: Used by the AOCS to control spacecraft attitude.

• Performance : Momentum wheels at 1200 to 5000 rpm 0.4 to 400 Nm

• Accuracy : Peak Torque (Nm), Momentum Capacity (Nms)

– Nominal torque

– Moment of inertia (rotor)

Reaction Wheel: RW

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CubeWheel Large Credit: CubeSpace

AOCS Equipment List

Company Peak Torque (Nm) Model TRL

Adcole Space 0.001 MAI400 9

AAC Clyde Space 0.040 Small Sat RW 9

Berlin Space Technologies 0.016 RWA0 5 9

Blue Canyon Technologies 0.004 RWP0 15 9

CubeSpace 0.001 Cube Wheel Medium 9

NanoAvionics 0.003 RWO 9

Sinclair Interplanetary 0.020 RW3-0.06 9

Vectronic Aerospace 0.020 VRW-02 Unk

Reaction Wheel: RW

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Table: High Heritage Miniature Reaction Wheels

RW1 Credit: Blue Canyon Technologies

AOCS Equipment List

• Function: Thrusters generate both forces and torques, so they can be used for both trajectory control and attitude control

• Types: – In-Space Chemical Prop

• Hydrazine Monopropellantulsion• Hybrids

– In-Space Electric Propulsion (EP)• Electrothermal • Electrosprays• Gridded-Ion• Hall-Effect• Pulsed Plasma and Vacuum Arc Thrusters

– In-Space Propellant-less Propulsion• Solar Sails • Electrodynamic Tethers • Aerodynamic Drag

• Company– Bradford-ECAPS, Aerojet Rocketdyne, Dawn Aerospace, SSTL, GomSpace, VACCO, CU Aerospace,

Aurora Propulsion Technologies, Busek, Rafael, SITAEL, Miles Space, Tethers Unlimited

E.g., Actuator- Thruster

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ConstantQ thruster head. Credit: Miles Space.

BHT-200 Hall Effect ThrusterCredit: Busek.

NASA's OCSD CubeSats use water/steam for propulsionCredit: NASA

AOCS Equipment List

Control Moment Gyros: CMGs

• A CMG consists of a spinning rotor and one or more motorized gimbals that tilt the rotor’s angular momentum. As the rotor tilts, the changing angular momentum causes a gyroscopic torque that rotates the spacecraft

• Company: Airbus

E.g., Actuators

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Nutation Dampers

• Nutation dampers are passive devices designed to dissipate energy, thereby producing steady rotation of a spinning spacecraft about its axis of maximum principal moment of inertia

CMG 15-45 S >high performance CMG optimized for 1,000kg class satellites Credit: Airbus

(Ref. https://en.wikipedia.org/wiki/Control_moment_gyroscope)

ST5 passive nutation damper. Credit: NASA

AOCS Equipment List

Integrated Units • Function: Integrated units combine multiple different

attitude and navigation components to provide a simple, single component solution to a spacecraft’s GNC requirements.

• Company– Blue Canyon Technologies– Adcole Space– Berlin Space Technologies– CubeSpace– KU Leuven > Model ADCS – Tyvak -> Inertial Reference Module (IRM)

E.g., Sensors & Actuators

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MAI-500 0.6U CubeSat ADACS+Star Tracker (1°)Credit: Adcole Space This 0.6U Attitude Determination and Control System features two Star Trackers, three reaction wheels, three electromagnets, a 3-axis magnetometer, and an ADACS computer for a stand-alone, Plug-and-Play attitude control system for small satellites.

AOCS Equipment List

Horizon Sensors / Earth Sensors• Horizon sensors have been used on many Earth-orbiting spacecraft, especially on

Earth-pointing spacecraft

• The appearance of the Earth in visible wavelengths is quite complicated; aside from having oceans, vegetation, and deserts, it has phases like the Moon. The appearance is more uniform at infrared wavelengths, especially in the narrow 14–16 m emission band of the CO2 molecule, so almost all horizon sensors are designed to detect infrared radiation in this range

• Horizon sensors are fundamentally of two types: static sensors that look in fixed directions, and scanning sensors that move a small FOV of a detector across the Earth

• Performance: 0.25° accuracy

• Company

– Adcole Space, CubeSpace, Servo, Solar MEMS Technologies

E.g., Sensors

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Servo Model RH 310Horizon Crossing Indicator (HCI)Credit: Servo

CubeSense is an integrated sun and nadir sensor Credit: CubeSpace

AOCS Equipment List

Inertial Sensing

• Is a broad category which includes gyroscopes for measuring angular change and accelerometers for measuring velocity change

• Inertial sensors are packaged in different ways, ranging from single-axis devices (e.g., a single gyroscope or accelerometer), to packages which include multiple axes of a single device type (e.g., Inertial Reference Units are typically three gyroscopes mounted in a triad orientation to provide three-axes angular change), to Inertial Measurement Units (IMUs)

• IMU: An inertial measurement unit is an electronic device that measures and reports a body's specific force, angular rate, and sometimes the orientation of the body, using a combination of accelerometers, gyroscopes, and sometimes magnetometers.

• Company (Refer to Gyro slide)

E.g., Sensors

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Onboard Computers was required for supporting the AOCS software to command, calculate and process the AOCS equipment.

IMU-µIMU-ICCredit: NovAtel

AOCS HARDWARE Process Flow

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AOCS requirement was designed since Preliminary design review: PDR.However, the AOCS equipment has been updated and detailed during the Critical design review: CDR phase as well as preparing the AOCS equipment for Module Readiness Review: MRR and Test readiness review: TRR.Test Readiness Review: TRR has purposing to prepare all documentation and to check all equipment before testing.AIT readiness Review: ARR has the purpose of checking the equipment was passed all AIT requirements, e.g. passed the burn-in process and thermal cycle process before the integration process.Finally to checking all equipment is ready to ship to Launch Vehicle: PSR

Note: The Design Development and Verification plan or DDVP should be create for planning all process to develop equipment

AOCS HARDWARE VERIFICATION PROCESS

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The important document was used in TRR including TVM and test procedure. For the test equipment in laboratory should be checkbefore test e.g. test harness, equipment in procedure and connector saver.

The process diagram was shown below

Reference1. Olivier L. de Weck, Attitude Determination and Control (ADCS) Department of Aeronautics and Astronautics Massachusetts Institute of T

echnology 16.684 Space Systems Product Development 16.684 Space Systems Product Development Spring 2001

2. F. Landis Markley and John L.Crassidis, Fundamentals of Spacecraft Attitude Determination and Control (2014)

3. Gavin Johnston_AOCS Customer Engineer Training_2019-2020

4. http://www.s3l.be/usr/files/di/fi/2/Lecture13_ADCS_TjorvenDelabie_20181111202.pdf

5. David Feltham_Theos-2 AOCS Hardware Course _2019-2020

6. Professor Craig Underwood, SPACECRAFT SYSTEMS, 15th – 19th July 2019 (Lecture)

7. Small Spacecraft Systems Virtual Institute, Ames Research Center, Moffett Field, California, NASA. State of the Art: Small Spacecraft Technology. (2020).

8. David Feltham THEOS-2 Star Tracker Lecture V002

9. Simon Miles GPS Training Material Theos-2_2019

10. Ed. By James R.Wertz, Spacecraft Attitude Determination and Control. (1978)

11. Mohamed M Abid is the author of Spacecraft Sensors, published by Wiley. (2005)

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