CSIRO’s radio telescopes and others in Australia, China, Japan and the USA have revealed how the wind speeds on Saturn’s moon Titan vary with altitude—and have turned a disappointment into a triumph.
As the Huygens probe plummeted through Titan’s atmosphere on 14 January it transmitted a stream of data to its parent Cassini spacecraft. The ground-based radio telescopes ‘eavesdropped’ on the probe’s signal. As the probe was buffeted by Titan’s winds, its radio signal was shifted in frequency. These ‘Doppler shifts’ have been used to measure the wind speeds.
Another experiment to determine the Doppler shifts, the Cassini/Huygens Doppler Wind Experiment, was going to rely on data transmitted from the probe to Cassini. But the transmitted data was lost because because one of the receivers on Cassini was not properly configured. The data from the telescopes has plugged that gap.