Galileo Nudged Back on Course : Space: Crippled craft’s speed is reduced to meet asteroid this month.

The crippled Galileo spacecraft was given a gentle tug Wednesday to put it on course for a historic encounter with an asteroid later this month.

Galileo’s speed of 36,000 m.p.h. was reduced by less than 1 m.p.h. to bring it on target for an Oct. 29 rendezvous with the asteroid Gaspra, according to the Jet Propulsion Laboratory, which is managed by Caltech for the National Aeronautics and Space Administration.

The three-ton spacecraft will give scientists their first close-up look at an asteroid when it passes within about 1,000 miles of Gaspra, but there is a problem. The 16-foot-wide high-gain antenna, which was supposed to open earlier this year like an umbrella, remains stuck in a claw-like position.

So the photographs and other scientific data collected during the encounter will be stored in the spacecraft’s tape recorder. Scientists will have to wait until November, 1992, to see the results. At that time, the spacecraft will be speeding toward Earth on its second Earth flyby, and it will be close enough for the data to be transmitted to the Pasadena lab by Galileo’s smaller antenna.

Engineers at the lab are continuing their efforts to free three of the main antenna’s 16 ribs, which apparently are stuck. The pictures could be sent back as soon as they succeed.

They will try to open the antenna again in December, and if that fails, they may fire the craft’s small thrusters in an effort to jar it loose, according to William J. O’Neil, manager of the $1.4-billion project. If the antenna cannot be fixed, nearly all of the priceless data that Galileo is to collect during a two-year tour of Jupiter and its moons in 1995 will be lost.

Galileo will snap a series of about 150 photos as it flies past Gaspra, and scientists at JPL hope to get at least one high-resolution black and white photo and one color picture. However, the 11-mile-long rock--which is believed to be fairly representative of the asteroids that orbit the sun between Mars and Jupiter--will not be in many of the pictures. As the spacecraft passes Gaspra, the camera will sweep a broad area, so the asteroid will be in the field of view only part of the time.

As asteroids go, Gaspra is not particularly distinctive. It is far smaller than the larger asteroids, which range up to more than 500 miles in diameter and are known as minor planets. But it will be important to scientists because asteroids are believed to have formed during the earliest stages of the solar system and thus are primitive bodies that could shed clues about the evolution of the sun and its orbiting planets.

Wednesday’s maneuver involved 162 firings of the spacecraft’s tiny rockets, called thrusters, over a 90-minute period. Without the firings, Galileo would have passed more than 1,200 miles from Gaspra.

An additional slight correction may be required later this month.

Galileo Update

A small course correction on Wednesday sent the Galileo spacecraft toward history’s first rendezvous with an asteriod. But the craft’s main antenna is still jammed, so scientists will probably have to wait more than a year for the photos from the encounter with Gaspra. First flyby, Dec. 8, 1990 Second flyby, Dec. 8, 1992 Venus flyby, Feb. 10, 1990 Launched October, 1989 Antenna Malfunction, April 11, 1991 Asteriod Gaspra flyby, Oct. 29, 1991 Arrival at Jupiter December, 1995 Source: Jet Propulsion Laboratory.