Models and GOCE Measurements of Thermosphere Density and Wind Below 250 km

The last year of the science mission and the deorbit phase of GOCE offer a unique opportunity to assess the results of models of the density and wind in the middle and lower thermosphere. After depletion of GOCE's xenon fuel on the morning of October 21, 2013, when the satellite's mean geodetic altitude was 239 km, it took 3 weeks before the satellite disintegrated during re-entry, shortly after UTC midnight on November 11. A continuous record of instrument and housekeeping data was received until about 7 hours before re-entry, at which point the satellite's minimum geodetic altitude was just 138 km. Although the along-track axes of the accelerometers on GOCE were saturated two days before the re-entry, accurate acceleration data could still be derived from the continuous GPS tracking up to the final day. The result is that a unique set of partially redundant, but largely complementary data on the aerodynamic interaction of the atmosphere with the spacecraft is available for this sparsely sampled altitude range. Density and wind data derived for the GOCE deorbit phase, as well as the science data from the period of October 2012 to October 2013, have been compared with both empirical models (NRLMSISE-00, JB-2008, DTM-2013, HASDM, HWM07, HWM14) and general circulation models (WACCM-X, TIE-GCM, GITM, UAM-P), exposing the relative strengths and weaknesses of these models.