Space probe heads for Titan

2004-12-25 08:46

California - The international Cassini spacecraft launched a probe on a three-week free-fall toward Saturn's mysterious moon Titan, where it will plunge into the hazy atmosphere and descend by parachute while its science instruments and cameras make observations.

The European Space Agency's Huygens probe is equipped with instruments to sample the chemistry of the planet-size moon's thick atmosphere, and may reveal whether it actually has lakes or seas of liquid methane and ethane that have been theorised by scientists.

A signal confirming release of the probe was received at Nasa's Jet Propulsion Laboratory at (03:24 GMT on Saturday). The actual event occurred earlier, but it took more than an hour for radio signals to cross the hundreds of millions of miles between Saturn and earth.

Smiles broke out in the JPL control room where members of the mission staff wore red and white Santa hats.

The aim had to be good because Huygens has no maneuvering system to adjust its own course, and it was designed to remain dormant until just before hitting Titan's atmosphere on January 14.

Long way to go

"This was a big one partly because we had to do this right or no mission at all," said David Southwood, the ESA science programme director. "But there's still a lot to come. We've got a hell of a long way to go."

A detailed analysis of data from the release was under way, but there were no indications of any problems, said Earl Maize, the Cassini deputy programme manager at JPL.

"We are quite confident we had a very clean release," he said.

Cassini was equipped with springs to gently push the 320kg probe away at a rate of one foot per second and impart a stabilising spin of seven revolutions per minute. Next week Cassini will make a course change to avoid following Huygens into Titan's atmosphere.

Huygens was designed for only a brief mission. After entering the atmosphere it will deploy a huge parachute that will allow it to make a 2 1/2-hour descent while radioing findings back to Cassini.

After touching down at 24 kph, it may continue sending data for up to 30 minutes, when either its battery fails or Cassini vanishes over Titan's horizon.

Cassini will later turn its antenna toward earth and send the data back to Nasa's Deep Space Network and on to an ESA operations centre in Darmstadt, Germany.

Titan is a key target of Cassini's $3.3bn mission to study the Saturn system, which includes its spectacular rings and numerous moons. Scientists believe Titan may have organic - meaning carbon-based - compounds similar to those that existed on the early earth.

On the net:

saturn.jpl.nasa.gov

www.nasa.gov/cassini

- AP