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GOCE Gravity Gradients in Instrument and Terrestrial Frames

GOCE Gravity Gradients in Instrument and Terrestrial Frames. J. Bouman , Th. Gruber, S . Rispens , E. Schrama , C.C. Tscherning , M.Veicherts , P. Visser. This presentation. Analysis of GOCE gravity gradients Instrument and Earth related frames

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GOCE Gravity Gradients in Instrument and Terrestrial Frames

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  1. GOCE Gravity Gradients in Instrument and Terrestrial Frames J. Bouman, Th. Gruber, S. Rispens, E. Schrama, C.C. Tscherning, M.Veicherts, P. Visser

  2. 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. Frame trafo EGG_TRF_2 Temporal corrections EGG_NOM_2 Outliers, data gaps External calibration Gravity Gradient Preprocessing

  4. EGG_NOM_2 & EGG_TRF_2 • EGG_NOM_2: • Given in instrument frame (GRF) • Accurate: VXX, VYY, VZZ, VXZ; less accurate: VXY, VYZ • Error increase at long wavelengths • Used in gravity field recovery • EGG_TRF_2: • Given in Local North-Oriented Frame • GGs VXY, VYZ: GOCE gravity model • Long wavelength GG signal: GOCE gravity model • GG error expected to be more homogeneous

  5. EGG_NOM_2 & EGG_TRF_2 • EGG_NOM_2: • Given in instrument frame (GRF) • Accurate: VXX, VYY, VZZ, VXZ; less accurate: VXY, VYZ • Error increase at long wavelengths • EGG_TRF_2: • Given in Local North-Oriented Frame • GGs VXY, VYZ: GOCE gravity model • Long wavelength GG signal: GOCE gravity model • GG error expected to be more homogeneous

  6. EGG_NOM_2:3 revolutions November 1, 2009

  7. Temporal gravity field variations VZZtime series, 1 day SD VZZ, 1 day  SDs VZZtemporal corrections, 1 day 

  8. External calibration • Three methods for GG calibration: • Global gravity field models • GOCE GPS data • 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. Estimated GG error SDsVXX, VYY, VZZ • GOCE QL gravity model: • GGs and GPS tracking • Data from November and December 2009 • SH degree 200 • Error assessment usingGG residuals Measurement Band (MB) (Pail & Mayrhofer 2010) • VXX and VYY same noise level in MB, VZZ 2x larger • Noise reduction in upper MB is “work in progress” (see Fehringeret al, Floberghagen, this morning)

  10. EGG_NOM_2 & EGG_TRF_2 • EGG_NOM_2: • Given in instrument frame (GRF) • Accurate: VXX, VYY, VZZ, VXZ; less accurate: VXY, VYZ • Error increase at long wavelengths • EGG_TRF_2: • Given in Local North-Oriented Frame • GGs VXY, VYZ: GOCE QL gravity field model • Long wavelength GG signal: GOCE gravity model • GG error expected to be more homogeneous

  11. EGG_NOM_2 & EGG_TRF_2:3 revolutions November 1, 2009 EGG_NOM_2 EGG_TRF_2

  12. EGG_TRF_2: VXX GOCE - EIGEN5C (N=360) Binned averages31 October 2009 - 11 January 2010 Color scale: -15 mE to +15 mE GOCE - EGM2008 (N=360)Binned averages 31 October 2009 - 11 January 2010

  13. EGG_TRF_2: VYY GOCE - EIGEN5C (N=360) Binned averages31 October 2009 - 11 January 2010 Color scale: -15 mE to +15 mE GOCE - EGM2008 (N=360)Binned averages 31 October 2009 - 11 January 2010

  14. EGG_TRF_2: VZZ GOCE - EIGEN5C (N=360) Binned averages31 October 2009 - 11 January 2010 Color scale: -15 mE to +15 mE GOCE - EGM2008 (N=360)Binned averages 31 October 2009 - 11 January 2010

  15. 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 VZZ about 2x that of VXX, VYY in MB Spurious tracks VYY 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 Summary

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