NASA has estimated the total Cassini budget at $3.27 billion, including a European participation of $600 million including Huygens and the Italian Space Agencys contribution, a $160 million high-gain antenna for Cassini.
European scientists and ESA officials said that when salaries of European Cassini and Huygens teams are included, Europes contribution to the mission rises to nearly 25 percent of the total.
This has been a great investment for Europe in terms of the scientific involvement we have been guaranteed, said Daniel Gautier, emeritus director of research at Frances CNRS. Europeans are the principal investigators on two of the 12 Cassini instruments, and four of the six Huygens instruments.
Some 150 researchers in Europe are taking part in the mission as co-investigators on one or more of the observing instruments.
The Huygens probe is expected to be released by Cassini Dec. 24 or Dec. 25, and descend three weeks later into the opaque atmosphere of Saturns largest moon, Titan. Its nominal mission begins and ends with this descent, expected to total no more than two and one-half hours Jan. 15, 2005.
The 320-kilogram, 2.7-meter-diameter Huygens might survive a landing, but mission success will depend on the data sent to Cassini during the atmospheric descent. Any further returns from Huygens will be icing on the cake. During descent its instruments will attempt to collect and transmit data on the composition of Titans atmosphere.
Huygens is not designed to land, it is designed to traverse the atmosphere of Titan, said Marcello Coradini, solar system exploration manager at ESA. The relative position of Cassini and Huygens will permit direct contact between the two for about four and one-half hours, including two hours on the surface just in case Huygens continues transmitting after it lands, said Jean-Pierre Lebreton, Huygens project manager at ESA, during a June 3 press briefing with NASA. The probe has enough battery power to send data for up to three hours, Lebreton said.
The parachute-slowed descent will slow Huygens atmospheric entry from an atmospheric-entry speed of 20,000 kilometers per hour to no more than 6 meters per second by the time it reaches Titans surface.
We have to go from Mach 20 to Mach 1.5 in about three minutes, Gautier said.
EADS Spaces French division, formerly Aerospatiale, built the Huygens probe.
A shield similar to the one that will protect Huygens on descent was also used for ESAs Atmospheric Re-entry Demonstrator, which circled the Earth once before landing in October 1998 following launch on an Ariane 5 rocket.
Titan interests scientists for its size -- it is bigger than several planets in the solar system -- and its thick, methane-laden atmosphere, which is 50 percent thicker than Earths atmosphere. It is the only moon in the solar system with a thick atmosphere.
With an atmospheric temperature estimated at minus 179 degrees Celsius, Titan may contain some of the chemical components that were present on Earth before life began.
Several scientists working on the mission made a point of highlighting how long it has taken to prepare for collecting scientific results from Cassini-Huygens. The Huygens probe was selected for ESA funding in 1988.
Gautier said Huygens represents the kind of mission Europe cannot do on its own, in part because it has not developed satellite nuclear power. ESAs Rosetta satellite, on its way to rendezvous with a comet 675 million kilometers from the sun, features 34-meter-long solar arrays that will soak up what little solar power is obtainable so far from the sun.
ESA currently has no active program to develop nuclear power for satellites.
Saturn, at about 1.4 billion kilometers from the sun, could not be visited with current satellite solar arrays. I am one of those pushing for nuclear-power development here in Europe, Gautier said, saying the Rosetta mission is about as far as satellites can travel without alternative forms of power.
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