Cassini Spacecraft Hardware Trouble May Harm Titan Mission

By Andrew Bridges Pasadena Bureau Chief posted: 03:11 pm ET 05 October 2000

PASADENA, Calif. -- A newly discovered hardware problem aboard the Cassini spacecraft may leave it unable to receive much of the science data the Huygens probe will collect when it parachutes down onto Saturns moon Titan in 2004.

Recent tests conducted by the European Space Agency (ESA) -- which contributed Huygens to NASAs Cassini mission -- revealed that the existing link between the probe and orbiter cannot support the full recovery of the data generated during the 2.5 hour plunge through Titans atmosphere.

"The problem is in the receiver: the bandwidth within it is not as wide as the design called for," said Bob Mitchell, the Cassini program manager at NASAs Jet Propulsion Laboratory.

In practical terms, that could mean much of the science data relayed from the Huygens probe to Cassinis finely tuned ear could be beyond what the receiver is capable of hearing.

However, with four years and a month remaining before Cassinis scheduled jettisoning of Huygens, Mitchell said engineers aim to get a fix in place so no data is lost.

"We hope to recover all of it. Thats not a promise to you we will, but that s certainly our objective," Mitchell said. "I am optimistic we will get this fixed."

The European Space Agency hopes to have a recovery plan in place by next summer, according to a press release issued on Thursday. ESA has also begun an investigation into why the glitch did not turn up in prior analyses and tests.

Although there is no way to work around the hardware aboard Cassini itself -- the spacecraft now is approaching Jupiter -- engineers hope to perhaps increase the spacecrafts flyby distance from Titan. That maneuver would lead to an increased signal level with a reduced Doppler shift, enabling the data signal to remain within the existing bandwidth.

"It would get it back to an operating range that is closer to the as-built range," Mitchell said.

The Cassini spacecraft, with the Huygens probe aboard, was launched in October 1997.

The mammoth vehicle -- among the largest ever launched -- will enter orbit around Saturn on July 1, 2004.

Cassini's mission is to study Saturn, its moons and rings, along with its magnetic and radiation environment during its four-year tour. It will deploy the Huygens probe on November 30, 2004.

The probe will study Titans nitrogen-rich atmosphere in the estimated 2.5 hours it takes to land. Once on the surface, it will survive anywhere from three to 30 minutes. Scientists believe Titan's surface may have lakes of ethane or methane.

http://www.space.com/missionlaunches/missions/huygens_probe_endangered_001005.html

-- Doris (reaper@pacifier.com), October 06, 2000