First results from the GPS atmosphere sounding experiment TOR aboard the TerraSAR-X satellite

Abstract

GPS radio occultation events observed between 24 July and 17 November 2008 bythe IGOR occultation receiver aboard the TerraSAR-X satellite are processed and ana-lyzed. The comparison of 16 262 refractivity profiles with collocated ECMWF data yielda mean bias of−0.60% to+0.02% at altitudes between 5 and 30 km. Standard deviations decrease from about 0.8% to 1.8% at 5 km to about 0.5% to 0.8% at about 10kmaltitude. At low latitudes mean biases and standard deviations are larger, in particular inthe lower troposphere. The results are consistent with 15 159 refractivity observationscollected during the same time period by the BlackJack receiver aboard GRACE-Aand processed by GFZ’s operational processing system. The main difference between the two occultation instruments is the implementation of open-loop signal tracking inthe IGOR (TerraSAR-X) receiver which improves the tropospheric penetration depthin terms of ray height by about 2km compared to the conventional closed-loop dataacquired by BlackJack (GRACE-A).