During a spacewalk in the cargo bay, two of the four astronauts on next month's flight of the space shuttle Columbia plan to simulate an electronic repair job to see if a later shuttle crew can salvage a $70 million satellite whose electronic pointing system broke down in orbit more than two years ago.

"It's a good idea to try this out," astronaut Joseph P. Allen said yesterday at a news conference at Houston's Johnson Space Center. "Whatever we can do on this flight to help out the guys on a later flight is a good idea."

Allen and fellow civilian William B. Lenoir will attempt to remove an electronics box identical to one that broke down. They will be wearing the cumbersome spacesuits required in an airless and weightless environment.

The attempt will involve grounding a dozen small cables, cutting plastic seals that hold them together, removing 18 screws that hold the cables to a panel and prying from the panel the entire set of cables.

At stake in the simulated repair job is the health of the Solar Maximum Mission satellite, a 5,000-pound satellite orbited in February, 1980, to study the sun during maximum sunspot activity.

Less than six months after the satellite attained orbit, the electronic devices that point its seven instruments at the sun broke down, and the satellite has been almost useless.

Congress has approved the $18 million needed to navigate the space shuttle alongside the damaged satellite in an orbit 308 miles above Earth, where flight planners expect it to be for the repair attempt in April, 1984.

A major expense in fixing the satellite involves training the astronaut crew in handling the satellite and in using whatever tools may be needed as shuttle and satellite whiz along in orbit together at 17,500 miles an hour in daylight and darkness.

While Allen observes and photographs the scene with a television camera atop his helmet, Lenoir is to simulate the repair work with three special wrenches and a pry bar modified for the weightlessness of space.

Civilian pilot Vance Brand and Marine Col. Robert Overmeyer, the copilot, are to watch the work on television in the shuttle cockpit. Columbia's first operational mission is scheduled to begin Nov. 11.