On-Orbit Performance of KOMPSAT-2 AOCS Korea Aerospace Research Institute Seung-Wu Rhee, Ph. D.

Transcription

1 SSC07-VII-9 On-Orbit Performance of AOCS Korea Aerospace Research Institute Seung-Wu Rhee, Ph. D. 1

2 Program - is Low Earth Orbit Satellite - Mission : Cartographic Mission of Korean Peninsula for MAP Generation - Program Period : ~ Payload : 1 m PAN + 4 m Multi-Spectral Camera - Launch Date : July 28, Launch Vehicle : ROKOT - Major Responsible Institute : Korea Aerospace Research Institute - Government Funded Program (MOST/MOCIE/MIC) 2

3 Summary - Orbit : Altitude : 685km, Sun Synchronous (LMTAN : 10:50AM), Inc degree - Swath Width of Optical Camera : 15km - Mass : ~800kg, Power : 1.1Kw, Deployed Length : 6.8m - Zero Momentum Biased 3 Axis Stabilized Satellite - Required AOCS Pointing Accuracy : deg - Required AOCS Pointing Knowledge : 0.02 deg - Required Pointing Stability : deg/sec 3

4 Deployed Configuration 4

5 AOCS Control Modes AOCS Modes AOCS Modes Sun Mode (3 (3 Submodes) Science Mode (2 (2 Submodes) Maneuver Mode (2 (2 Submodes) Back-up Mode (3 (3 Submodes) Power Safe Mode Power Safe Mode 5

6 AOCS Control Mode Transition Diagram A2 Back-up Earth Search Submode B1 A2 Back-up Attitude Hold Submode Power Safe Mode B3 A3 A2 B1 Back-up Sun Pointing Submode A1 A2 B2 B1 Safe Hold Submode (Contigency Mode) B1 A1 Sun Pointing Submode B1 B1 A1 Science Fine Submode (Normal Mission Mode) B1 B1 Earth Search Submode A2, A3, B2 and B3 paths in figure are newly developed to increase an operational flexibility and robustness for. A2 A2 Science Coarse Submode A1 Attitude Hold Submode Note: Path A1 is the Recovery Path with Thruster Path A2 is the Recovery Path with RWA Path A3 is the Recovery Path with Ground Gyro Configuration Path B1 is the Contigency Path Path B2 is the Contigency Path for Star Tracker Failure Path B3 is the Contigency Path for Gyro Selection Logic Fail A1 6

7 AOCS Science Mode Science Mode Science mode consists of two submodes : Science Coarse Submode, Science Fine Submode Science Coarse Submode - Purpose : Coarse Earth Pointing for Cartographic Mission - Sensor : Conical Earth Sensor, Fine Sun Sensor, Gyro, Tri-Axis Magetometer - Actuator : Reaction Wheel Assembly, Magnetic Torque Rod 7

8 AOCS Science Mode Science Fine Submode - Purpose : Fine Earth Pointing for Cartographic Mission - Sensor : Star Tracker, Gyro, Tri-Axis Magetometer - Actuator : Reaction Wheel Assembly, Magnetic Torque Rod 8

9 AOCS H/W Connection Local 1553 Data Bus 9

10 AOCS Main Components Valve Drive Electronics Gyro Assembly Remote Drive Unit (On-Board Computer) Thruster Bank Star Tracker Reaction Wheel Assembly 10

11 Pyramid Type of Reaction Wheel Configuration +Z(Yaw) H3 H2 RWA 3 RWA 2 H4 H1 RWA 4 β RWA 1 +Y(Pitch) α +X(Roll) Pyramid Type with Four Reaction Wheels 11

12 Non-Linear Simulation Results Pointing Accuracy in Science Fine Submode(<0.009deg) Pointing Knowledge in Science Fine Submode(<0.008deg) 12

13 Non-Linear Simulation Results S/C Body Rate with SA Rotation ( <0.02deg/s) S/C Body Rate with SA Rotation Stop (<0.0006deg/s) 13

14 On-Orbit Performance of Science Fine Submode Attitude Between LVLH and Body Frame Using Star Tracker #2 Quaternion 0.05 Roll[deg] Pitch[deg] Yaw[deg] x x x 10 5 Pointing Knowledge of Science Fine Submode(<0.008deg) Body Rate with Solar Array Rotation(<0.02deg/s) 14

15 On-Orbit Performance of Science Fine Submode Body Rate with Solar Array Rotation Stop(<0.0025deg/s) 25 deg Roll Maneuver Case 15

16 On-Orbit Performance of Science Fine Submode -2.0~-2.5deg/hr -1.0~-1.1deg/hr 0.4~0.9deg/hr Estimated Gyro Bias Profile 16

17 Conclusion Remarks - The AOCS Control Logic of has been successfully developed and implemented to meet the 1 meter high resolution imaging mission requirements. - The pointing knowledge of Science Fine Submode is < 0.008deg(3sig) according to On-Orbit data - On-Orbit Data shows that the flexibility and stepping effects of solar array increase rate amplitude up to 0.02deg/sec. - While, the rate amplitude is decreased by ~10 times to deg/sec when solar array stopped. - According to on-orbit pointing knowledge error data, constant error in pitch axis is observed, which comes from OBT desynchronization problem. - Unexpectedly large rate bias in gyro set is observed: ~2-2.5deg/hr probably, due to gyro misalignment wrt star tracker. 17

18 Thanks for your attention!!!! 18