Threat to Titan mission deepens.

The European Space Agency (ESA) announced last month that a communications problem could prevent the Huygens probe, set to parachute through the atmosphere of Saturn's moon Titan in 2004, from successfully relaying some of its data (SN: 10/21/00, p. 262).

Scientists initially estimated that if the problem remains uncorrected, some 20 percent of the information gathered during the 2.5-hour Titan mission could be lost. SCIENCE NEWS has learned that after further analysis, ESA now suspects that as much as two-thirds of the data relayed by Huygens might not be received by its mother craft, NASA's Cassini, which will transmit the information to Earth. The craft is now passing Jupiter.

To minimize the data loss, NASA and ESA had suggested slowing Cassini during Huygens' descent. However, the slowdown could hamper the rest of Cassini's mission, in which it will tour Saturn and its moons, says Huygens project scientist Jean-Pierre Lebreton of ESA in Noordwijk, the Netherlands. A more promising strategy could be to raise Cassini's altitude above Titan during the probe's passage. But if the altitude is raised too high, Cassini can't use Titan's gravity to steer it through the Saturn system.

"It's a complex tradeoff," Lebreton says.

Meanwhile, Cassini has begun taking images of Jupiter, whose gravity is kicking the spacecraft toward Saturn. In late December, when it passes within 10 million kilometers, Cassini will make observations in conjunction with the Galileo craft, which has toured the Jovian system since late 1995. That will mark the first time that two spacecraft have taken simultaneous images of the same planet.