Oct 5 2000
From The Space Library
European Space Agency (ESA) engineers announced the discovery of a flaw in the European receiver on NASA's Cassini spacecraft]], prompting an inquiry into why engineers had not identified the problem before NASA had launched the craft, and how the issue could be resolved before the craft reached its destination. Cassini's probe data relay subsystem (PDRS) lacked sufficient bandwidth to navigate the Doppler shift with the Huygens Probe as the probe parachuted toward the surface of Saturn's moon Titan. Therefore, the system would be unable to recover all of the data that Huygens's six instruments would generate. Cassini and Huygens launched on 15 October 1997, with Huygens scheduled to separate from Cassini on 6 November 2004, break through Titan's atmosphere on 27 November 2004, and descend to the moon's surface using a parachute system. The mission plan called for Huygens to measure the composition and winds of Titan's atmosphere and to collect images. The probe would send the data via the S-band PDRS to Cassini, which would then transmit the data to Earth. However, the ESA stated that the inadequate bandwidth of the PDRS meant that link margins would degrade, because the Doppler shift on the data subcarrier would be outside the bandwidth of the receiver-phase lock loop, leading to a potential loss in the link of I OdB over what engineers had assumed for the mission. 1004
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