1. Star tracker derived rotations and accelerometer analysis Peter Schack, Anja Schlicht, Nadja Peterseim, Roland Pail, Thomas Gruber Institut für Astronomische und Physikalische Geodäsie (IAPG), TU München Forschungseinrichtung Satellitengeodäsie (FESG), TU München Centre of Geodetic Earth System Research (CGE) SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014

2. Level 1A Version 3 products: SW_OPER_STRASCI_1A_yyyymmddT235500_yyyymmddT000459_0301 SW_RPRO_STRASCI_1A_yyyymmddT235500_yyyymmddT000459_0301  Attitude of CHUs data record: MDR_STR_SCI  STR processed data record: MDR_STR_PRC Abbreviations: ICRF: Inertial Reference Frame CRF: Common Reference Frame MRF: Measurement Reference Frame SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 2 1 Star tracker data

3. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 3 2 Star tracker derived rotations

4. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 4 2 Star tracker derived rotations

5. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 5 2 Star tracker derived rotations -STR processed data record: MDR_STR_PRC

6. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 6 2 Star tracker derived rotations

7. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 7 2 Star tracker derived rotations

8. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 8 2 Star tracker derived rotations

9. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 9 2 Star tracker derived rotations

10. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 10 3 Accelerometer analysis Figure 2 ‑ 23: Radial acceleration of Swarm A. Left: S/C is in full sun. Right: S/C passes through the eclipse (indicated by grey background). (Swarm Accelerometer Anomaly Report)

11. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 11 3 Accelerometer analysis

12. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 12 3 Accelerometer analysis

13. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 13 3 Accelerometer analysis

14. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 14 3 Accelerometer analysis

15. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 15 3 Accelerometer analysis Courtesy to Eelco Doornbos

16. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 16 3 Accelerometer analysis

17. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 17 3 Accelerometer analysis

18. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 18 3 Accelerometer analysis

19. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 19 3 Accelerometer analysis

20. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 20 3 Accelerometer analysis

21. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 21 3 Accelerometer analysis

22. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 22 3 Accelerometer analysis a = amplitude  = width  = center (time) ζ = asymmetry factor a 2 = amplitude, depends on a s = scaling of damping d 1, d 2 = damping factors ω = ang. frequency b i = polynomial coefficents

23. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 23 3 Accelerometer analysis heater torquer twangs

24. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 24 3 Accelerometer analysis

25. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 25 3 Accelerometer analysis Charging and discharging of satellite surfaces

26. STR: -STR processed data record: MDR_STR_PRC ICRF  CRF quaternions in overlapping time periods at beginning and end of a file do not contain identical values -Attitude of CHUs data record: MDR_STR_SCI Time tags are not ‘equidistant’ (sometimes 2 values in 1 second) -Star tracker derived angular accelerations are dominated by noise. Comparison to temperature reduced angular accelerations from VZLU on the basis of angular rates can be considered (after compensating STR temperature dependence) ACC: -High amplitude peaks seem to be comparable to GRACE twangs -With support from TU Delft it would be possible to correlate these peaks with solar impact on different satellite surfaces SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 26 4 Summary

27. SWARM Data Quality Workshop – Potsdam / Germany 02. – 05. December 2014 27 Thank you for your attention