Two May Go on Space Walk in Satellite Rescue

The space agency decided Sunday to move the shuttle Discovery in for a close look at a disabled satellite, but put off until today a decision on whether to send two astronauts on a dangerous, unrehearsed space walk to try to resurrect the satellite and rocket it on its way.

The satellite, which had been rolled out of the shuttle’s cargo bay on Saturday, did not automatically blast into its proper orbit and is rolling lifelessly about 50 miles from the shuttle.

The National Aeronautics and Space Administration scheduled a rendezvous with the satellite for Tuesday, and extended the shuttle’s flight through Thursday or Friday. Foul weather in Florida had already precluded the scheduled landing on Wednesday.

Maneuver Ruled Out

NASA ruled out one possible maneuver, in which an astronaut standing on the tip of the shuttle’s robotic arm would be lifted out to the satellite to release a stuck lever that is thought to be the problem. That plan is believed to be too dangerous because it would place the astronaut too close to the seven-ton satellite, which is rotating twice every minute and is loaded with rocket fuel.

One plan under consideration, however, is to equip the astronaut with some sort of extended grappling device so that he could ride the arm close enough to reach the lever but still maintain a safe distance from the satellite.

The most likely option, however, would be to attach some sort of device to the end of the arm itself and try to hook the lever with that.

None of the astronauts aboard the Discovery have been trained specifically for any of those operations, and they would have to attempt the feat with makeshift tools. If it is attempted, it will be the first time that crewmen have been asked to venture outside a shuttle on an unscheduled space walk.

Lever Crucial

A final decision on whether to send the astronauts out may not be made until after the Discovery gets a closer look at the satellite Tuesday. A space walk is possible only if the crew can see that the four-inch lever on the side of the spinning satellite is stuck. Otherwise, the satellite’s problems are beyond the capability of the Discovery crew to solve.

The decision to proceed with a rendezvous was issued to the astronauts during an evening radio call to Discovery. Earlier, crew members made it clear that they wanted to try to save the crippled satellite, built and owned by Hughes Communications Services Inc.

“If there is any opportunity of saving this guy, we would sure like to give it our best try,” pilot Donald E. Williams, 42, told Mission Control in Houston.

The Discovery’s cabin pressure was to be lowered today, a standard procedure before a space walk to reduce the threat of the astronauts’ suffering the bends.

If a space walk does occur, the Discovery will have to be positioned alongside the satellite and two astronauts probably will venture outside. Timing will be especially critical, both in approaching the satellite and in pulling away from it.

Should Be 20 Miles Away

Once the lever is pulled, the satellite is supposed to spring to life, sending out an antenna within 80 seconds, firing positioning jets within six minutes and then igniting its big rocket motor in 45 minutes. The shuttle would have to back away quickly with both astronauts still in the open cargo bay. The shuttle should be at least 20 miles away before the satellite fires its big rocket, a NASA spokesman said.

The astronauts would have to time their operation for the 10-minute “window” that occurs in each orbit when the satellite can move up to its proper station 22,300 miles above the Equator.

All of the plans “presuppose that the lever is the problem,” John Cox, a flight controller at Houston, said Sunday.

“If it’s not this, we’re not prepared to do anything else, that’s for sure,” he said.

If it turns out that the problem is something else, the Discovery will have no choice but to back away and leave the satellite behind.

Not Designed for Retrieval

The satellite was not designed to be retrieved, and there is no way the shuttle can latch on to it to bring it back, as a shuttle mission did last year with two errant satellites. Even if that were possible, it would be unlikely for NASA to attempt to return a fully fueled satellite to earth.

The satellite, known as Leasat-3, was launched to become part of the Defense Department’s worldwide communications system. The department has contracted to pay $83.75 million for Leasat’s services over the next five years. The satellite is insured for about $80 million.

NASA officials said repeatedly that no decision has been made on whether to send crewmen outside the craft to attempt the rescue. It was clear Sunday that the agency was apprehensive about such an operation.

At the Johnson Space Center in Houston, astronauts Woody Spring and Jerry Ross carried out operations in a “wet tank,” simulating conditions in a weightless environment, similar to those proposed for Discovery crewmen Jeffrey A. Hoffman, 40, and Navy Capt. S. David Griggs, 45. Hoffman is an astrophysicist and Griggs is a former Navy fighter pilot.

The operation would call for a number of innovative procedures. When activities like this are planned in advance, the shuttle’s robotic arm is fitted with a foot restraint so that the astronaut can lock his feet in place on the end of the arm. But since no space walk was planned for this flight, the foot restraint is not in place. If an astronaut rides the arm, the space walkers will have to tie a restraint on the end of the arm.

The satellite is 15 feet in diameter, and the lever is on the side. Although the satellite is only rotating twice per minute, the lever will pass the astronaut at a fairly good clip. Cox, the flight controller, said he had stood in front of a mock-up of the satellite in Houston and it felt “like standing up to a wall” that is moving past.

Of more concern, however, is what happens after the lever is pulled.

“I’m sure you are aware of the timing that would occur after that,” Brewster Shaw, an astronaut in Houston who is trying to simulate the conditions aboard the shuttle, told the Discovery commander, Air Force Col. Karol J. Bobko, 47.

NASA has not said who will operate the robotic arm, which can be maneuvered like a Space Age cherry picker, but M. Rhea Seddon, 37, has been trained for that kind of operation.

No role has been assigned to the two payload specialists aboard the Discovery, Charles D. Walker, 36, and Sen. Jake Garn (R-Utah), 52.