Shuttle Launch Delayed Until Next Week : Space: Repair of a telescope sensor will keep Columbia on the ground until at least Tuesday. Replacing the unit pushes the liftoff to Friday.

Disappointed NASA officials said Friday that the space shuttle Columbia, carrying the star-crossed Astro observatory, will not be able to launch until Tuesday evening at the earliest and possibly not until Friday evening.

On Thursday, engineers lost communications with one of the four telescopes in the observatory and were forced to reopen Columbia’s payload bay doors to gain access to the telescope, a process that took nearly a full day. They hope to know by today whether they will have to repair or replace the electronic communications package.

The package connects one of the telescopes to a telephone line while the shuttle is on the ground so that engineers can monitor the temperature and pressure of the liquid argon used to cool the telescope’s detector, which is used to image stars. Without the package, they cannot be sure that the telescope is safe.

Engineers hope to use a specially prepared cable to re-connect external phone lines to the communications package. If that is not successful, a new package will have to be installed. Both the cable and the new package are being flown in from Goddard Space Flight Center near Washington, D.C., and are expected to arrive this morning.

Both repair and replacement take about the same amount of time, but if the entire package has to be replaced, three extra days of checkout will be required, necessitating the Friday evening launching. On either of the planned launch days, the Columbia is scheduled for a 10:17 p.m. PDT liftoff that is expected to be visible over much of the southeastern United States.

NASA Associate Administrator William Lenoir admitted to some tension but said that the repairs will not be rushed. “Anytime we get close and don’t go, like a kid going to a carnival, yeah, we’re frustrated and we’re anxious to get going . . . (but) we’re calmly taking our time, and when it’s ready, we’ll go fly,” he said.

The $150-million Astro observatory is designed to study the universe at a variety of ultraviolet and X-ray wavelengths that are invisible to ground-based observatories because they are absorbed by Earth’s atmosphere. The seven-man astronaut team will operate the observatory around the clock for either nine or 10 days before returning the observatory to Earth.

Astro was originally scheduled for launching in early 1986, but the Challenger explosion in January of that year forced a four-year postponement. The mission got to within six hours of launching in May before engineers discovered a large leak of potentially explosive hydrogen in the engine compartment during fueling.

The leak proved to be in a 17-inch valve connecting the external fuel tank to the shuttle, and NASA was forced to return Columbia to the massive Vehicle Assembly Building here for replacement of the valve.

Another--albeit smaller--hydrogen leak in the shuttle Atlantis, discovered during preflight fueling for a Department of Defense launching in July, led NASA to ground the shuttle fleet for the rest of the summer. The five-month gap since the last launching in April is the second-longest period without a shuttle flight since the program began, exceeded only by the three-year gap following the Challenger explosion.

The Atlantis leak was thought to have a different source than that on Columbia, but, within the last two weeks, engineers at Rockwell International in Downey have found that the two leaks were virtually identical.

In both cases, the leaks were caused by microscopic glass beads that contaminated the seals on the valve, allowing hydrogen to leak out. No one has yet been able to identify the source of the beads, but Lenoir on Friday ruled out sabotage and predicted that the space agency would find the source within a few days.

Meanwhile, both Columbia and the shuttle Discovery, which is slated for an Oct. 5 launching of the high-priority Ulysses probe, which will go into polar orbit around the sun, have been fitted with 17-inch valves from a different manufacturing batch. The valve with the least leakage in manufacturing tests (some leakage is allowable) is in Discovery, and the second-best valve is in Columbia.

Discovery has the highest priority for launching because the Ulysses probe must perform a slingshot maneuver around Jupiter to attain its correct orbit around the sun. If it is not launched during its 18-day window in October, the next favorable alignment of planets will not occur for 13 months.

The valve on Columbia has not been tested under realistic conditions and will not be until actual preflight fueling begins. Lenoir said he was not worried, however. “We’re confident we’re not going to have any leaks, but if it does, we will not fly.”