American astronauts are poised for the most ambitious job the space shuttle team has yet attempted - the rescue and repair of an ailing satellite. If successful, the feat will demonstrate a new phase of satellite operations in which costly equipment need not be abandoned just because it breaks down in orbit. It will also demonstrate the kind of cost savings involved with such ''service call'' maintenance. In this case, a replacement satellite would cost an estimated $240 million. Shuttle astronauts can repair it for about $50 million.
Space shuttle Challenger and its five-man crew were undergoing final preparations at this writing. They are scheduled to launch from the Kennedy Space Center at 8:58 a.m. Eastern standard time tomorrow and return to the center April 12 at 8:10 a.m. EST.
Once again, mission commander Robert L. Crippen will be heading for orbit - his third trip in the shuttle. He will be accompanied by Francis R. Scobee, pilot, and mission specialists Terry J. Hart, George D. Nelson, and James D. Adrianus von Hoften.
The seven-day mission is the 11th for the shuttle system, although it is called mission 41-C in the jargon of the National Aeronautics and Space Administration. It has a busy schedule.
Besides the satellite repair itself, there is a complex series of orbital maneuvers to undergo just to put Challenger in position for that task. These begin during the first mission day and continue, at various times, until the third day, when shuttle and satellite should be within a couple of hundred feet of each other.
Meanwhile, on the second mission day, the astronauts are to launch what is called a long-duration exposure facility (LDEF). This is a multipurpose satellite - a kind of space bus - with 57 experiments furnished by more than 200 investigators from nine nations, including the United States. The equipment generally is simple and, in some cases, completely passive.
The 21,400-pound LDEF will drift along its orbit for 10 1/2 months. Then a future shuttle mission will bring it back to the ground.
The LDEF has no means of attitude control. It measures 14 by 30 feet and is to be oriented so that its long axis is vertical with respect to Earth. In this position the slight variation of Earth's gravity with height should be sufficient to stabilize the satellite.
Placing the LDEF in this orientation, however, will tax the astronauts' skill. The shuttle's manipulator arm will hold the satellite for a short period to allow any arm-related motion to die out. Then it will gently release the LDEF as Challenger carefully backs away from it.
The main objective of this mission, however, is repair of the Solar Maximum Mission satellite. Its name derives from its mission. Solar Max was orbited in 1979 to enable solar physicists to study the sun during a period of maximum activity.
But after only 11 months on orbit, in December 1980, Solar Max lost attitude control. It has also suffered some instrument malfunctions.
On the third mission day, mission specialist Nelson is to ride one of the jet-propelled backpacks - manned maneuvering units - over to Solar Max. There he is to dock with the satellite and stop its rotation. The arm can then bring the satellite into the cargo bay, where it can be mounted on a special rack. The flight plan provides for the astronauts to repair Solar Max and return it to orbit. There it could function into the next decade. But if they cannot repair it, the satellite will be brought back to the Kennedy Space Center.
There is a great deal riding on this demanding assignment. Solar Max was designed for such on-orbit repair. If this is shown to be practical, it should boost confidence in this strategy for using satellites. But were the mission to fail, that budding confidence could be shaken.
While the human astronauts are concerned with such challenges, their nonhuman colleagues - some 3,300 honeybees - will face what may, for them, be an equally demanding task of building a honeycomb under weightless conditions.
This experiment by Dan Poskevich - a student at Tennessee Technological Institute - is designed to gain understanding of the role gravity plays in such activities.