Journal of Geodesy

, 85:791 | Cite as

GOCE gravitational gradients along the orbit

  • Johannes Bouman
  • Sophie Fiorot
  • Martin Fuchs
  • Thomas Gruber
  • Ernst Schrama
  • Christian Tscherning
  • Martin Veicherts
  • Pieter Visser
Original Article

Abstract

GOCE is ESA’s gravity field mission and the first satellite ever that measures gravitational gradients in space, that is, the second spatial derivatives of the Earth’s gravitational potential. The goal is to determine the Earth’s mean gravitational field with unprecedented accuracy at spatial resolutions down to 100 km. GOCE carries a gravity gradiometer that allows deriving the gravitational gradients with very high precision to achieve this goal. There are two types of GOCE Level 2 gravitational gradients (GGs) along the orbit: the gravitational gradients in the gradiometer reference frame (GRF) and the gravitational gradients in the local north oriented frame (LNOF) derived from the GGs in the GRF by point-wise rotation. Because the VXX, VYY, VZZ and VXZ are much more accurate than VXY and VYZ, and because the error of the accurate GGs increases for low frequencies, the rotation requires that part of the measured GG signal is replaced by model signal. However, the actual quality of the gradients in GRF and LNOF needs to be assessed. We analysed the outliers in the GGs, validated the GGs in the GRF using independent gravity field information and compared their assessed error with the requirements. In addition, we compared the GGs in the LNOF with state-of-the-art global gravity field models and determined the model contribution to the rotated GGs. We found that the percentage of detected outliers is below 0.1% for all GGs, and external gravity data confirm that the GG scale factors do not differ from one down to the 10−3 level. Furthermore, we found that the error of VXX and VYY is approximately at the level of the requirement on the gravitational gradient trace, whereas the VZZ error is a factor of 2–3 above the requirement for higher frequencies. We show that the model contribution in the rotated GGs is 2–35% dependent on the gravitational gradient. Finally, we found that GOCE gravitational gradients and gradients derived from EIGEN-5C and EGM2008 are consistent over the oceans, but that over the continents the consistency may be less, especially in areas with poor terrestrial gravity data. All in all, our analyses show that the quality of the GOCE gravitational gradients is good and that with this type of data valuable new gravity field information is obtained.

Keywords

GOCE Gravitational gradients External calibration Tensor rotation 

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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • Johannes Bouman
    • 1
  • Sophie Fiorot
    • 2
  • Martin Fuchs
    • 1
  • Thomas Gruber
    • 3
  • Ernst Schrama
    • 4
  • Christian Tscherning
    • 5
  • Martin Veicherts
    • 5
  • Pieter Visser
    • 4
  1. 1.Deutsches Geodätisches Forschungsinstitut (DGFI)MunichGermany
  2. 2.SRON Netherlands Institute for Space ResearchUtrechtThe Netherlands
  3. 3.Institut für Astronomische und Physikalische Geodäsie (IAPG), TU MünchenMunichGermany
  4. 4.Delft Institute of Earth Observation and Space Systems (DEOS), TU DelftDelftThe Netherlands
  5. 5.Niels Bohr InstituteUniversity of CopenhagenCopenhagenDenmark

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