New Effort Fails to Free Jammed Antenna on Galileo Jupiter Probe

As expected, the latest attempt to free a stuck antenna on the spacecraft Galileo failed Wednesday, but scientists say they believe another technique to be tried in January will stand a better chance of unjamming the important piece of equipment.

“We thought the antenna would remain unchanged and it did,” said William J. O’Neil, Galileo project manager. He is based in Pasadena at the Jet Propulsion Laboratory, which is operating the craft for the National Aeronautics and Space Administration.

Since last week, the Galileo craft has been alternately turned toward the sun and away from it in an attempt to unfurl the main antenna, which facilitates communications with Earth. Galileo is slated to reach Jupiter in 1995 for a two-year study of the giant planet and its four brightest moons.

The $3.7-million antenna was supposed to open like an inverted umbrella, but only 15 of its 18 ribs unfurled. The antenna cannot work that way.

In January, Galileo is expected to be about the same distance as Earth from the sun, at one of the warmest parts in its journey, as it uses this planet’s gravity to boost it out into space toward Jupiter.

At that time, O’Neil said, the motors driving the antenna should be at their most efficient. They will be turned on and off more than 1,000 times in an attempt to force the jammed “umbrella” open. “We see more promise in this,” he said.

Scientists plan to use the reserve antenna, 10,000 times weaker, if the main antenna is still jammed after the last-chance effort early next year. They would lose about 30% of the information they had hoped for and be forced to wait months rather than minutes to receive it.