Galileo's antenna: pinning the problem.

In mid-August, NASA scientists failed in their third attempt to use temperature changes to unfurl the main antenna aboard the Galileo spacecraft, now heading toward a 1995 rendezvous with Jupiter. If two to four graphite "ribs" of the umbrella-like antenna stay stuck after further thermal tries to loosen them in December and next year, the $ 1.3 billion mission may prove largely fruitless, since Galileo could transmit only a fraction of the data it would collect during its Jovian visit (SN:8/3/91, p.79).

In the meantime, says Neal Ausman Jr., mission director for Galileo at the Jet Propulsion Laboratory (JPL) in Pasadena, Calif., researchers have identified a key factor that contributed to the antenna malfunction. Scientists had already suggested that alignment pins, which keep the ribs properly positioned around the antenna's mast when the antenna is closed, somehow jammed. The new information: Some of the lubricant added in 1982 to the pins' receptacles to reduce friction apparently rubbed off during four or more cross-country trips between JPL and the Kennedy Space Flight Center in Florida, Ausman says. The trips were due to delays in the shuttle program following the Challenger accident, he adds.

The pins likely to have lost the most lubricant during transport are the same ones that now appear stuck, Ausman observes. "It's a shame that we weren't a bit better and able to find this [before], but it's not the kind of thing that stares you in the face," says engineer Thomas Williams of the NASA Goddard Space Flight Center in Greenbelt, Md. Ausman told SCIENCE NEWS that pins on similar antennae aboard NASA communications satellites are replaced just before launch and new lubricant added.