Analysis of High-resolution GOCE Densities
Bruinsma, Sean1; Doornbos, Eelco2; Bowman, Bruce3
1CNES, FRANCE; 2TU Delft, NETHERLANDS; 3Air Force Space Command, UNITED STATES
In the framework of the ESA GOCE+ project, thermosphere densities and crosswind speeds are retrieved from GOCE observations. The resulting data on the thermosphere will complement and extend existing thermosphere datasets, such as those derived from CHAMP and GRACE data. The data processing and the resulting data set are unique in several ways: GOCE uses an ion thruster to compensate for atmospheric drag, in order to maintain its orbit at a very low mean altitude of 270 km. This means that the most important acceleration data source for density retrieval is the thruster activation data. The nearly sun-synchronous dawn-dusk orientation of the orbit is also unique for high-resolution acceleration-derived thermosphere measurements. The added value of this unique density data set will be shown in this presentation through analysis of the results of comparisons of GOCE densities to models. In particular, the models DTM2012, developed within the EU 7th framework project 'ATMOP', and the High Accuracy Satellite Drag Model (HASDM) of the United States Air Force, are used. HASDM includes the Dynamic Calibration Atmosphere algorithm that solves for the phases and amplitudes of the diurnal and semidiurnal variations of thermospheric density in near real-time, from the observed drag effects on a set of Low Earth Orbit calibration satellites. Therefore, it serves as an independent validation for the GOCE-derived density measurements. Secondly, small-scale variability of the upper atmosphere at the GOCE altitude is derived through filtering and compared to similar results observed with higher orbiting spacecraft, CHAMP and GRACE.