Resolving the Cassini/Huygens relay radio anomaly

Communication Challenges for Solar System Exploration Missions

“…Comprehensive testing of the radio link between Huygens and Cassini was not performed prior to the launch of the mission, and so in February 2000 an European Space Agency (ESA)-devised test was conducted through the deep space network (DSN) communication system in which signals simulating probe TM were transmitted to the Cassini spacecraft. The TM stream replicated the expected signal strength as the probe dropped through the atmosphere of Titan, and accounted for the Doppler shift of signals expected between the descending probe and orbiting Cassini spacecraft during the encounter [19]. The results of the test were startling; while data were received correctly when no Doppler effects were included, almost all of the transmitted TM packets were lost by the Cassini communications system once Doppler was applied to the signal being sent to the spacecraft.…”

“…Without a solution, only 10 per cent of the planned science data would have been returned from the probe, and none of the science goals would have been achieved [19]. A number of approaches to solve the problem were proposed, including changes to the probe's onboard software (unfeasible because of the inability to modify the design of the probe support avionics remotely), changes to the ground station TM decoders to improve their ability to recover corrupted data 'frames' from the spacecraft, and heating the probe's ultrastable oscillator (USO, which provides a frequency reference and generates the S-band signals -see section 5 for further information) to induce a small change in the frequency of the probe transmissions [19]. Ultimately, the Huygens mission was saved by altering the planned trajectory of Cassini so that the orbiter was further from Titan as the probe entered the atmosphere.…”

“…A number of lessons were learned from this incident [19,21]. Some elements of the communications system, including the S-band transponder were based on standard and inherited designs.…”

Exploring the Solar System

“…101 In his memoir, Tyson details the fallout from his decision, reporting that it "would disrupt my life for years to come." 102 He does not tell us if this disruption was welcome, but, indeed, throughout his recounting it is clear that he and many others had great fun gaining public notoriety responding to what, they all knew, or hoped, would ultimately be good press for astronomy, and for the American Museum of Natural History. Surely there were unpleasant or tense moments in the flood of mail and public derision, but when a noted and highly respected geophysicist and former NASA high official offered his mild critique, he classed Tyson's institution as "The Science Citadel of the Capital of the World."…”

“…During six months of hard work, the team performed extensive ground and flight testing, modeling, and simulation to understand the failure mechanism in the radio relay. 102 They elaborated models to predict the corruption of science data under several scenarios and discussed these predictions with the science teams to determine the overall performance in each scenario. Finally, the HRTF recommended a solution, which, they claimed, would return 100 percent of Huygens science data.…”