HP-SSA-DWE-2-3-DESCENT

Data Set Overview On January 14, 2005, the Huygens Probe, part of the joint NASA/ESA CassiniHuygens mission to Saturn, entered the atmosphere of Titan, descended for 2.5 hours under a parachute and eventually landed softly on the surface of Titan LEBRETONETAL2005. Six experiments collected data during the descent and on ground. The data set, which this data set catalog belongs to, is the archive of the Huygens Doppler Wind Experiment (DWE), which was designed to measure Titans zonal winds by Doppler tracking Huygens from Cassini and from Earth BIRDETAL2005. In contrast to the other five experiments, DWE was not designed to collect data aboard Huygens. Instead, it was designed to measure the frequency of the Huygens carrier signal received aboard Cassini and on Earth. The radio link between Huygens and Cassini had two independent and partially redundant channels. One of them (channel A) was used for DWE Doppler tracking of Huygens. The accuracy desired by DWE required the use of special UltraStable Oscillators (USO) for the channel A transmitter aboard Huygens and for the channel A receiver aboard Cassini. For the reception on Earth, a USO was not required, as the accuracy of the Hmaser driven radio antennas is much higher than that of a USO. The data rate of the Huygens signal was 8 kHz. It was recorded, decoded and stored aboard Cassini in realtime for later transmission to Earth via the Cassini High Gain Antenna. The Huygens signal level was, however, to weak to be decoded on Earth. The minimum integration time for the detection of the Huygens signal on Earth was of the order of 1 sec. Due to an error in the sequence, which was executed by Cassini during the Huygens mission, the receiver USO was not switched on for the mission. Consequently, the channel A receiver aboard Cassini could not lock onto the channel A signal from Huygens and all data transmitted via this channel including the DWE fr truncated!, Please s [truncated!, Please see actual data for full text]