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ESA releases the fifth generation of GOCE gravity field solutions

18 July 2014

The fifth generation GOCE gravity field solutions based on the so-called Time-wise (TIM) and Direct (DIR) methodologies, have been processed and verified by the GOCE HPF team, and are now made available to the public by ESA.

This is a major mission milestone, after the release of the previous fourth generation gravity solutions on 20 March 2013.

While the fourth generation spanned 27 months-worth of effective data volume, the fifth generation solutions span the complete mission lifetime, including the low orbit data up to the re-entry of the satellite in November 2013.

The time span covered is thus November 2009 up to November 2013, raising the effective data volume from 27 months up to approx. 42 months.

The coefficients for both TIM and DIR models can be downloaded directly from the links below, together with the associated data sheets discussing the model characteristics and more specific features of the resulting gravity fields.

The full EGM_GOC_2 product will shortly be made available on the GOCE Virtual Online Archive.

Further information on the released data sets:

Data Period:

  • TIM: 01/11/2009 - 20/10/2013 | Effective data volume: approx. 42 months
  • DIR: 01/11/2009 - 20/10/2013 | Effective data volume: ~ 19380 orbital revolutions ~ 1259 days

 

Key Characteristics:

1. TIM

  • GOCE-only solution in a rigorous sense. No external gravity field information is used, neither as reference model, nor for constraining the solution.
  • SGG processing strategy unchanged for all 5 releases of time-wise models
  • Related variance-covariance information represents very well the true errors of the coefficients
  • Solution can be used for independent comparison and combination on normal equation level with other satellite-only models (e.g. GRACE), terrestrial gravity data, and altimetry.
  • Since in the low degrees the solution is based solely on GOCE orbits, it is not competitive with a GRACE model in this spectral region.
  • Maximum degree and order 280

2. DIR:

  • The model is a satellite-only model based on a full combination of GOCE-SGG with GRACE and LAGEOS, leading to an excellent performance of the long as well as of the short wavelengths.
  • More processing details are given in Pail et al. 2011 and Bruinsma et al. 2013.
  • Maximum degree and order is 300

 

GOCE Input Data for the two solutions:

1. TIM:

  • Orbit data:
    • SST_PKI: Kinematic GOCE orbits
    • SST_PCV: Covariance Information related to kinematic orbits
    • SST_RNX: Original GOCE orbit data
  • Gradiometer data:
    • EGG_NOM: Level 2 gravity gradients in Gradiometer Reference Frame (GRF); rotations between inertial and gradiometer frame
    • EGG_CCD: common mode accelerations in GRF

2. DIR:

  • Orbit data:
    • SST_PKI: Kinematic GOCE orbits as positions for the gradiometry observation equations
    • SST_PRM: Rotations between inertial and Earth-fixed reference frames
  • Gradiometer data:
    • EGG_NOM: Level 2 gravity gradients in GRF
    • EGG_IAQ: Rotations between inertial and gradiometer reference frames
  • Other satellite data:
    • LAGEOS-1/2 SLR data (measurement period 1985 - 2010)
    • GRACE GPS-SST & K-band range-rate data (measurement period of ten years 2003 - 2012)

 

Download the fifth generation Time-wise solution and Data Sheet.

Download the fifth generation Direct solution and Data Sheet.