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Cassini–Huygens Probe

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Author Topic: Cassini–Huygens Probe  (Read 266 times)
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« on: June 21, 2007, 01:57:57 am »

"Channel A" data lost

Huygens was programmed to transmit telemetry and scientific data to the Cassini orbiter for relay to Earth using two redundant S-band radio systems, referred to as Channel A and B, or Chain A and B. Channel A was the sole path for an experiment to measure wind speeds by studying tiny frequency changes caused by Huygens' motion. In one other deliberate departure from full redundancy, pictures from the descent imager were split up, with each channel carrying 350 pictures.

As it turned out, Cassini never listened to channel A because of an operational commanding error. The receiver on the orbiter was never commanded to turn on, according to officials with the European Space Agency. ESA announced that the program error was a mistake on their part, the missing command was part of a software program developed by ESA for the Huygens mission and that it was executed by Cassini as delivered.

The loss of Channel A means only 350 pictures were received instead of the 700 planned. Also all Doppler radio measurements between Cassini and Huygens were lost. Doppler radio measurements of Huygens from Earth were made, though not as accurate as expected measurement that Cassini would have made; when added to accelerometer sensors on Huygens and VLBI tracking of the position of the Huygens probe from Earth, reasonably accurate wind speed and direction measurements can still be derived.

Amateur contributions

The Huygens mission benefited significantly from amateur contributions. This was enabled by the decision of the imaging science Principal Investigator Marty Tomasko to make the image raw data of the DISR instrument available to the public. The many small and low contrast images had to be assembled into mosaics and panoramas of the landing region in a time consuming process, and space science enthusiasts all around the world began to deal with this challenge. Only some hours later the first mosaics of the Huygens landing region were published,[8] created by Daniel Crotty, Jakub Friedl, Ricardo Nunes and Anthony Liekens. Christian Waldvogel published an improved and colorized Panorama. Another amateur, René Pascal, intensively engaged in the Huygens image processing, developed a method to remove camera artifacts from the images and created a comprehensive mosaic of the region now called Adiri.
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