1. NADIR workshop - October 25-26, 2011page 1 / 16 Density and Winds Inferred from GOCE Accelerometer (thrusters) Data Sean Bruinsma CNES, Toulouse Eelco Doornbos Delft University of Technology

2. NADIR workshop - October 25-26, 2011page 2 / 16 ESA contract No. 4000102847/11/NL/EL with TU Delft Consortium:TU Delft- Management and production CNES- Product evaluation HTG - Non-gravitational force modeling Project information http://thermosphere.tudelft.nl/goceplustheme3/ (nb: register first)

3. NADIR workshop - October 25-26, 2011page 3 / 16 Launch: 17 march 2009 (Plesetsk) Mission objectives: Determine geoid with an accuracy of 2 cm and gravity anomalies with an accuracy of 1-2 mGal (1-2 10 -5 m/s 2 ) at a resolution of 100 km (degree 200) Mission orbit: Sun-synchronous (i=96.5°), dawn/dusk, 255 km altitude Payload: Gradiometer (accelerometers), GPS receiver, laser retroreflector Drag control: Ion thrusters commanded in closed-loop GOCE: ESA’s first Earth Explorer

4. NADIR workshop - October 25-26, 2011page 4 / 16 GOCE: ESA’s first Earth Explorer

5. NADIR workshop - October 25-26, 2011page 5 / 16 GOCE mission in perspective

6. NADIR workshop - October 25-26, 2011page 6 / 16 GOCE mission in perspective

7. NADIR workshop - October 25-26, 2011page 7 / 16 GOCE mission in perspective

8. NADIR workshop - October 25-26, 2011page 8 / 16 GOCE: drag and solar radiation

9. NADIR workshop - October 25-26, 2011page 9 / 16 GOCE: drag and solar radiation

10. NADIR workshop - October 25-26, 2011page 10 / 16 GOCE natural decay & drag-free Natural decay (about 3 months, not shown) followed by drag-free flight starting 13 September 2009 at the mission altitude of 254.9 km (NB: the figure shows mean spherical altitude) Density inferred from accelerometer data Density inferred from thrusters+accelerometer data

11. NADIR workshop - October 25-26, 2011page 11 / 16 GOCE thrusters data

12. NADIR workshop - October 25-26, 2011page 12 / 16 GOCE thrusters data Thrust < 3mN: noise (red line=3-point average Thruster data sampling: 8 s

13. NADIR workshop - October 25-26, 2011page 13 / 16 Preliminary GOCE densities

14. NADIR workshop - October 25-26, 2011page 14 / 16 Preliminary GOCE densities

15. NADIR workshop - October 25-26, 2011page 15 / 16 Preliminary GOCE densities

16. NADIR workshop - October 25-26, 2011page 16 / 16 GOCE densities To do: Implement satellite model Combine thrusters and accelerometer data Compute densities and winds Validate products Poster in session SA10 at the AGU Fall Meeting