Accelerometers for GNSS Orbit Determination

Transcription

1 Accelerometers for GNSS Orbit Determination Urs Hugentobler, Anja Schlicht Technische Universität München 5th International Colloquium on Scientific and Fundamental Aspects of the Galileo Programme October 28, 2015, PTB, Braunschweig, Germany 1

2 Accelerometers Accelerometers measure non-gravitational accelerations Several scientific satellite missions were and are equipped with high-grade accelerometers: CHAMP, GOCE, GRACE, Swarm Radiation pressure is the largest error source for precise orbit determination of GNSS satellites Would accelerometers onboard of GNSS satellites help to improve modelling of non-gravitational perturbations? STAR accelerometer on CHAMP Sino-German Symposium, Sept. 16,

3 Experiments 1 Covariance Analysis How much does the estimation of accelerometer offset and drift parameters affect the formal orbit precision? 2 Orbit Determination Including Simulated Accelerometer Measurements What is the required quality of accelerometers to support precise orbit determination? Sino-German Symposium, Sept. 16,

4 Simulations Walker 24/3/1 Galileo constellation Galileo box-wing satellite model Sino-German Symposium, Sept. 16,

5 Simulations FOC 16 station tracking network Sino-German Symposium, Sept. 16,

6 Simulations 1 day arcs 30sec sampling code and phase observations 1mm phase noise, 10 cm code noise estimated parameters: orbit initial conditions rpr parameters or accelerometer parameters (offset/offset+drift) satellite clock parameters station troposphere parameters (2h resolution) phase ambiguities (float) station coordinates and clocks fixed error propagation to satellite positions Bernese GNSS Software V5.0 (modif) Sino-German Symposium, Sept. 16,

7 Formal Alongtrack Orbit Errors 7

8 Formal Alongtrack Orbit Errors 8

9 Formal Alongtrack Orbit Errors 9

10 Formal Alongtrack Orbit Errors 10

11 Estimation of Accelerometer Scaling Params 11

12 Accelerometer Offsets 12

13 Accelerometer Offsets + Drifts 13

14 POD with Accelerometer Measurements Inclusion of simulated accelerometer measurements into force model Caution with using noisy measurements in orbit integrator, filtering required Procedure simulation of observations for FOC network precise orbit determination based on accelerometers of different quality Comparison of orbits with true orbits 14

15 Accelerometers Three grades of accelerometers GOCE-type accelerometer with three high-accuracy axes (similar to GOCE x and z axes) GOCE-type accelerometer with three low-accuracy axes (similar to GOCE y axis) Swarm-type accelerometer Systematic errors: n-times-per revolution variations of low amplitude depending on Sun beta angle (temperature effect) 15

16 Accelerometers 16

17 Accelerometers, GOCE-x 17

18 Accelerometers, GOCE-y 18

19 Accelerometers, Swarm 19

20 Radiation Pressure Acceleration Plane A 20

21 Radiation Pressure Acceleration Plane B 21

22 Radiation Pressure Acceleration Plane C 22

23 Radiation Pressure Acceleration 23

24 Radiation Pressure Acceleration GOCE-x 24

25 Radiation Pressure Acceleration GOCE-y 25

26 Radiation Pressure Acceleration Swarm 26

27 Accelerometer Measurements GOCE-x 27

28 Accelerometer Measurements GOCE-y 28

29 Accelerometer Measurements Swarm 29

30 Orbit Error 30

31 Orbit Error 31

32 Orbit Error 32

33 Orbit Error 33

34 Conclusions Formal orbit errors similar to CODE 5p model when estimating accelerometer offsets High orbit prediction instability if offsets and drifts are estimated High-grade accelerometers are required to measure radiation pressure perturbations with sufficient precision Issue: orbit prediction when using accelerometer measurements Alternative method is the calibration of orbit-periodic perturbation model using accelerometer measurements Accelerometers may support rapid recovery after maneuver Best alternative: Availability of reliable radiation pressure models 34