Attitude Determination of Small Satellite: The GNSS Paradigm

Transcription

1 Attitude Determination of Small Satellite: The GNSS Paradigm Dr. Najam Abbas Naqvi Assistant Professor Department of Aeronautics and Astronautics Institute of Space Technology Islamabad, Pakistan

2 Personal Profile Academics PhD. Aerospace (GNC-GNSS), China Specialized MS-GNSS, Italy MS Electrical Engineering, NUST, PK BS Electrical Engineering, UET, PK Professional Experience Assistant Professor, IST, PK Satellite Control Engineer, SUPARCO Publications Attitude Determination and Control Global Navigation Satellite System

3 Scope Motivation and Objective Attitude Determination (AD) Global Navigation Satellite System Research Design and Methodology Results and Analysis Conclusion

4 Motivation and Objective To design and implement a short baseline, multiantenna, stand-alone, commercial-off-the-shelf (COTS), GPS based attitude determination system for a Spacecraft using the Code measurements of GPS signals.

5 Attitude Determination and Control System Spacecraft Computer Desired Attitude None (Passive) Linear Limit Cycle Non-Linear Control Law Real Time Attitude Estimation Control Commands Attitude Actuators Thrusters Magnetic Torque Rod Momentum and Reaction wheel Movable Components Deterministic Filters Real Time Attitude Determination Internal Disturbance Torques Spacecraft Dynamics External Disturbance Torques Definitive Attitude Determination Solar Arrays Flexible Components Rotating Mechanisms Fuel Slosh People Aerodynamics Magnetic Gravity Gradient Solar Radiation Filter Bias Determination Attitude Measurement Earth, Sun, Stars Magnetometer Gyroscopes Payload Sensors Attitude Sensors

6 ADS Flow diagram Mission Requirements Attitude Representation Selection Attitude Coordinate System Selection Attitude Sensors Selection Modeling of Orbit Propagator Satellite Kinematics Dynamics Modeling Modeling of Disturbance s & Sensors AD Algorithm Selection and Implementation

7 Attitude Sensors Sensor Pros Cons Sun Sensor Horizon Scanner Reliable, Simple, Cheap Expensive No measurement in eclipse Orbit dependent, Poor in yaw Magnetometer Cheap Continuous Coverage Low Altitude only Star Tracker Gyroscope Very Accurate High Band Width Expensive-Heavy- Complex Expensive-Drifts with time GPS Receiver Single Sensor Several Errors

8 Accuracy Comparison of Sensors Sensor Mass (Kg) Power (Watt) Accuracy (3σ) Measured Angles Cost (K$ U.S) Gyroscope Drift Rate: o to 1 o /hour Roll, Pitch, Yaw Sun Sensor o -3 o Roll Coarse, Precise Yaw Star Sensor o o Roll, Pitch, Yaw Horizon Sensor o -1 o Roll Coarse, Precise Pitch Magneto-meter <1 0.5 o -3 o Roll, Pitch, Yaw GPS (for Space) o -1 o Roll, Pitch, Yaw >100

9 Attitude Representation Comparison Method Euler Angles Direction Cosines Quaternions Pros If given φ, ψ, θ, then a unique orientation is required Orientation defines a unique DCM Computationally Robust Cons Singularity 6 constraints Non Intuitive Not Intuitive Need Transforms Application Best for Analytical and Design work Best for Design and analysis Ideal for digital control Implementation

10 Attitude Determination Algorithms

11 AD : Recursive Estimation Algorithms REQUEST OPTIMAL REQUEST MME Euler-q Adaptive Optimal REQUEST Kalman Filter Unscented Filters Particle Filter The Orthogonal filter The Predictive filter Nonlinear observers Adaptive approaches

12 GNSS: Global Navigation Satellite System GNSS is a generic name for Global Navigation Satellite System, consisting of a Space Segment having a constellation of satellites in Medium Earth orbit at the height of 20,000 Km and above, Control Segment having Monitoring and Control stations to monitor / control/update the constellation of satellites and the User Segment; consisting of Receivers to give POSTION, VELOCITY and TIME of the static and mobile user all over the globe at all time using at least four satellites of the constellation in view.

13 Architecture of GNSS Space Segment Ground Control Segment User Segment

14 The Evolution Of GNSS Four Major GNSS GPS (US Fully Operational Since 1994) GLONASS (USSR - Fully Operational Since 1995 suspended and partially operated after collapse- since 2011 Soviet GLONASS is fully operational) Galileo (Europe expected fully operational in 2020) Beidou (CHINA expected fully operational in 2020)

15 Regional Navigation Satellite System Satellite Based Augmentation System Quasi-Zenith Satellite System (QZSS) Indian Regional Navigation System IRNSS Wide Area Augmentation System (WAAS) European Geostationary Navigation Overlay Service (EGNOS) Multi-functional Satellite Augmentation System (MSAS) GPS Aided Geo Augmented Navigation (GAGAN) The GLONASS System for Differential Correction and Monitoring (SDCM), proposed by Russia. The Satellite Navigation Augmentation System (SNAS) proposed by China.

16 Comparison of Major GNSS

17 17 The GNSS (Triliteration) Principle ),, ( o o o z y x x y z ),, ( k k k z y x b r ρ k known measured unknown r k k k k b z z y y x x + + = ) ( ) ( ) ( ρ

18 GNSS in 2020 Source: cited from Asia Oceania is the 'Showcase of the New GNSS Era',presented at 5th QZSS user meeting (KOGURE, Satoshi Mr., 10th March 2010)

19 GNSS Market 7 bln GNSS devices by 2022 almost one for every person on the planet (billions) CAGR: 9% Global GNSS market size CAGR: 5% Core revenue (Global) Enabled revenue (Global) The projected long-term growth gives significant business opportunities for GNSS market. Along with the rapid development of new services and applications, the business environment of GNSS market is demanding and requires constant innovation on the supply side. Source: The European GNSS Programmes 19

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21 Basic Principle of AD using GNSS

22 AD Using GNSS: Performance Factors Antenna Baseline Line Bias GPS Geometry Geometric Dilution of Precision; GDOP Attitude Dilution of Precision; ADOP Multipath Measurement Errors Signal To Noise Ratio; SNR Cycle Slip Antenna Positioning Receiver Noise Ambiguity Resolution

23 Error Sources in GNSS Observables

24 GADACS SPARTAN RADCAL REX II Gravity Probe B UNISAT Gyrostat UOSAT-12 ALSAT-1 GPS Based AD: Flying Experiments

25 GNSS based AD Georgi-ION-GNSS-2010 / Dec 2011 (PhD thesis)

26 X-Sat Antenna Platform Lin et.al. IEEE 2004

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28 GNSS Range and Phase Model P ( t) = ρ ( t, t τ ) + I + T + dm + c[ dt ( t) dt ( T τ )] + s s s s s s s s r, f P, r, f r r, f r r, f r r c[ d ( t) + d ( t τ )] + ε s s s r, f f r P, r, f Φ ( t) = ρ ( t, t τ ) I + T + δ m + c[ dt ( t) dt ( t τ )] s s s s s s s s r, f Φ, r, f r r, f r r, f r r + c[ δ ( t) + δ ( t τ )] + λ [ φ ( t ) φ ( t )] + λ z + ε s s s s s s r, f f r f r, f 0 f 0 f r, f Φ, r, f ρ ( t, t τ ) = r ( t τ ) + dr ( t τ ) r ( t) dr ( t) s s s s s s P, r, f r r f r r r, f

29 Single Difference Code and Phase Observables

30 Double Difference Code and Phase Observables

31 Antenna Placements

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33 Time Calculations GPS Master Observation File Time , Julian Day e+006 GPS Week 1399 Second of Week (SOW) e+005

34 Ephemeris Parameters of Visible Satellites SV-PRN af M Root a Delta n -9.57E E E E E-11 E omega Cuc -3.73E E E E E-09 Cus -3.73E E E E E-09 Crc Crs i I dot Cic 1.86E E E E E-09 Cis -1.86E E E E E-09 Omega0-9.03E Omega dot -8.44E E E E E-09 Toe af af Toc

35 SV-PRN af M Root a Delta n -9.57E E E E-11 E Omega Cuc -3.73E E E E-09 Cus -3.73E E E E-09 Crc Crs i I dot Cic 1.86E E E E-09 Cis -1.86E E E E-09 Omega Omega dot -8.44E E E E-09 Toe af af Toc

36 Visible Satellites in Inertial Frame Visible Satellite in ECEF Frame Sub-Satellite Points

37 Visible Satellites by Master Antenna (PRN) Pseudorange from Master Observation File (E+07 meters) Position of Visible Satellites in ECEF Frame (meters) E E E E E E E E E E E E E E E E E E E E E E E E E E E+07

38 Elevation of Visible Satellites (Degrees) Elevation of Visible Satellites`

39 Visibility Window during Mission Sky Plot of Visible Satellites

40 Number of Visible Satellites during Mission

41 Clock Errors (sec) Satellite Clock Offset Error Satellite Clock Relativistic Error E E E E E E E E E-09 Ionospheric Errors (meters) Tropospheric Errors (meters)

42 Corrected Pseudorange (meters) E E E E E E E E E07 Corrected Satellite Positions (meters) E E E E E E E E E E E E E E E E E E E E E E E E E E E+07 Dilution of Precisions GDOP TDOP PDOP HDOP VDOP

43 DOPs Variation

44 Mean Position of Master Antenna from 200 Epoch (meters) X Y Z Master Antenna Position Variations

45 Flow diagram of differential Positioning using code observation

46 Mean Position of Slave-1 Antenna from 400 Epochs (meters) X Y Z Slave-1Antenna Position

47 Mean Baseline Components between Master and Slave-1 (meters) X Y Z Variations of Baseline Components

48 Mean Position of Slave-2 Antenna from 200 Epoch (meters) X Y Z Slave-2 Antenna Position

49 Baseline Components between Master and Slave-2 (meters) X Y Z Variation of Baseline Components

50 Attitude Determination Using Code Observations Direct Method (Degrees) Attitude Mean Std Yaw Pitch Roll

51 Attitude Determination Using Code Observations LS Method Orientation Mean/Degree Std/Degree Yaw Pitch Roll

52 Difference between Direct and Least Square Method (Degrees) Orientation Direct Method Least Square Method Difference Yaw Pitch Roll

53 Precise AD Using GNSS: Future AD Using GNSS AD Using GNSS AD Using GNSS AD Using GNSS LAMBDA Modified LAMBDA Constrained LAMBDA Multi Constrained LAMBDA EKF/UKF EKF/UKF EKF/UKF

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55 GNSS at Institute of Space Technology Islamabad, Pakistan Maters of Science in Global Navigation Satellite System MS-GNSS

56 MS GNSS Curriculum According to the GNSS curriculum designed by the United Nations Office for Outer Space Affairs (UNOOSA)

57 Thank You Q & A Dr.Najam Naqvi najm_naqvi@yahoo.com