1. Bouman et al, GOCE Gravity Gradients, ESA Living Planet Symposium 2010 GOCE Gravity Gradients in Instrument and Terrestrial Frames J. Bouman, Th. Gruber, S. Rispens, E. Schrama, C.C. Tscherning, M.Veicherts, P. Visser

2. Bouman et al, GOCE Gravity Gradients, ESA Living Planet Symposium 2010 This presentation Analysis of GOCE gravity gradients Instrument and Earth related frames Data: 31 October 2009 – 11 January 2010 First GOCE gravity field solutions use same data period (next three presentations)

3. Bouman et al, GOCE Gravity Gradients, ESA Living Planet Symposium 2010 Gravity Gradient Preprocessing Temporal corrections Outliers, data gaps External calibration EGG_NOM_2 Frame trafo EGG_TRF_2

4. Bouman et al, GOCE Gravity Gradients, ESA Living Planet Symposium 2010 EGG_NOM_2 & EGG_TRF_2 EGG_NOM_2: – Given in instrument frame (GRF) – Accurate: V XX, V YY, V ZZ, V XZ ; less accurate: V XY, V YZ – Error increase at long wavelengths – Used in gravity field recovery EGG_TRF_2: – Given in Local North-Oriented Frame – GGs V XY, V YZ : GOCE gravity model – Long wavelength GG signal: GOCE gravity model – GG error expected to be more homogeneous

5. Bouman et al, GOCE Gravity Gradients, ESA Living Planet Symposium 2010 EGG_NOM_2 & EGG_TRF_2 EGG_NOM_2: – Given in instrument frame (GRF) – Accurate: V XX, V YY, V ZZ, V XZ ; less accurate: V XY, V YZ – Error increase at long wavelengths EGG_TRF_2: – Given in Local North-Oriented Frame – GGs V XY, V YZ : GOCE gravity model – Long wavelength GG signal: GOCE gravity model – GG error expected to be more homogeneous

6. Bouman et al, GOCE Gravity Gradients, ESA Living Planet Symposium 2010 EGG_NOM_2: 3 revolutions November 1, 2009

7. Bouman et al, GOCE Gravity Gradients, ESA Living Planet Symposium 2010 V ZZ time series, 1 day SD V ZZ, 1 day  SDs V ZZ temporal corrections, 1 day  Temporal gravity field variations

8. Bouman et al, GOCE Gravity Gradients, ESA Living Planet Symposium 2010 External calibration Three methods for GG calibration: 1.Global gravity field models 2.GOCE GPS data 3.Terrestrial gravity data GG scale factors 10 -2 – 10 -3 See Poster 014-D3:External Calibration of the GOCE Gravity Gradients at the High- Level Processing Facility (Wednesday)

9. Bouman et al, GOCE Gravity Gradients, ESA Living Planet Symposium 2010 Estimated GG error SDs V XX, V YY, V ZZ Measurement Band (MB) GOCE QL gravity model: GGs and GPS tracking Data from November and December 2009 SH degree 200 Error assessment using GG residuals V XX and V YY same noise level in MB, V ZZ 2x larger Noise reduction in upper MB is “work in progress” (see Fehringer et al, Floberghagen, this morning) (Pail & Mayrhofer 2010)

10. Bouman et al, GOCE Gravity Gradients, ESA Living Planet Symposium 2010 EGG_NOM_2 & EGG_TRF_2 EGG_NOM_2: – Given in instrument frame (GRF) – Accurate: V XX, V YY, V ZZ, V XZ ; less accurate: V XY, V YZ – Error increase at long wavelengths EGG_TRF_2: – Given in Local North-Oriented Frame – GGs V XY, V YZ : GOCE QL gravity field model – Long wavelength GG signal: GOCE gravity model – GG error expected to be more homogeneous

11. Bouman et al, GOCE Gravity Gradients, ESA Living Planet Symposium 2010 EGG_NOM_2 & EGG_TRF_2: 3 revolutions November 1, 2009 EGG_NOM_2EGG_TRF_2

12. Bouman et al, GOCE Gravity Gradients, ESA Living Planet Symposium 2010 EGG_TRF_2: V XX GOCE - EIGEN5C (N=360) Binned averages 31 October 2009 - 11 January 2010 GOCE - EGM2008 (N=360) Binned averages 31 October 2009 - 11 January 2010 Color scale: -15 mE to +15 mE

13. Bouman et al, GOCE Gravity Gradients, ESA Living Planet Symposium 2010 EGG_TRF_2: V YY GOCE - EIGEN5C (N=360) Binned averages 31 October 2009 - 11 January 2010 GOCE - EGM2008 (N=360) Binned averages 31 October 2009 - 11 January 2010 Color scale: -15 mE to +15 mE

14. Bouman et al, GOCE Gravity Gradients, ESA Living Planet Symposium 2010 EGG_TRF_2: V ZZ GOCE - EIGEN5C (N=360) Binned averages 31 October 2009 - 11 January 2010 GOCE - EGM2008 (N=360) Binned averages 31 October 2009 - 11 January 2010 Color scale: -15 mE to +15 mE

15. Bouman et al, GOCE Gravity Gradients, ESA Living Planet Symposium 2010 Summary GOCE gravity gradients in GRF and LNOF (EGG_NOM_2 & EGG_TRF_2) November 2009 – January 2010 timeframe Differences with EIGEN5C & EGM2008 (Africa, Himalaya, …) Error level V ZZ about 2x that of V XX, V YY in MB Spurious tracks V YY close to magnetic poles: – Not well understood – Very likely related to interaction between attitude control and magnetic field – Seems to diminish after in-flight calibration 11/12 January 2010 Overall, GG data look very good