The Huygens Doppler Wind Experiment

Abstract

The Cassini/Huygens mission to Saturn, a joint venture of NASA and ESA, was launched on 15 October 1997 from Kennedy Space Center, Cape Canevaral, Florida (USA) and will reach its destination in July 2004. The Huygens Probe is dedicated to descent through the atmosphere of Saturn's largest moon Titan by parachute. The scientific data gathered during the descent will be broadcasted to the Cassini orbiter for temporary storage and later transmitted to Earth using Cassini's powerful High Gain Antenna. <br /> The Doppler Wind Experiment (DWE), one of the six experiments carried out during the Huygens descent through Titan's atmosphere, utilizes the Doppler effect on the radio link between Huygens and Cassini to measure the radial velocity of Huygens with respect to Cassini. Its primary goal is the determination of the altitude dependence of Titan's zonal (east-west) winds along the descent track, thereby providing in situ verification ("ground truth'') of remote Cassini observations. The most problematic DWE issue is an accurate extraction of all Doppler components other than that due to the zonal wind. <br /> This thesis shows the development of the algorithm necessary for retrieval of the zonal wind speed from the frequency measurement and gives an estimation of the accuracy to which this can be performed.