ESA plans probe for U.S. Titan mission.

ESA plans probe for U.S. Titan mission

A proposed NASA mission that would orbit Saturn and send a probe to the surface of its big, possibly ocean-covered moon Titan got a boost from the European Space Agency (ESA) last week. Called Cassini, the mission has yet to win White House or congressional approval, but ESA nonetheless chose development of the Titan probe as its next major scientific project.

Scheduled for launch in April 1996, Cassini would go into orbit around Saturn in October of 2002, releasing the probe about three months later to descend through Titan's largely nitrogen atmosphere, possibly 60 percent more dense at the surface than Earth's own. A joint NASA/ESA working group has proposed a suite of nine scientific instruments for the probe, including a "surface science package" that could find itself studying what may be a sea or lake of liquid ethane containing absorbed methane gas. Earth's waters are so far the only liquid yet confirmed on any planetary surface in the solar system.

NASA hopes Cassini will win approval next year from the Office of Management and Budget, and Congress, as part of a joint project with another mission called the Comet Rendezvous Asteroid Flyby (CRAF). CRAF would be launched earlier, in 1995, but NASA would build the two missions on similar versions of a spacecraft called Mariner Mark II, being developed for a variety of outer-planet forays.

The agency would like CRAF and Cassini to begin together in NASA's fiscal 1990 budget, assuming there is money to initiate both of them as well as pay for other projects such as the space station. As a joint project, according to NASA spokesman Charles Redmond, they would cost from $850 million to $950 million (in 1988 dollars), whereas initiating them separately would total $1.1 billion to $1.3 billion. The probe for Cassini, ESA officials estimate, would cost another $260 million.

NASA and ESA had previously planned to collaborate on a project called the International Solar Polar Mission, with each agency sending a spacecraft to fly close over the poles of the sun. NASA canceled plans for its craft in October of 1981, however, triggering ESA's wrath and leaving the European agency to conduct the mission on its own. Now called Ulysses, the European spacecraft is scheduled for launch next April by the U.S. space shuttle.

If U.S. plans for Cassini flounder, ESA will select one of several alternative projects over which the probe won approval. If ESA's probe plans go awry, NASA will seek additional funding to handle the job itself.