Undaunted by last year's setbacks and buoyed by its successes, the National Aeronautics and Space Administration (NASA) has planned an ambitious set of space shuttle missions for this year. There are 12 in all, roughly one a month. If NASA can stick to that schedule, it will have gone a long way toward demonstrating the shuttle system as a reliable earth-to-orbit trucking service.
It fell short of doing this last year in spite of its spectacular success with on-orbit satellite rescue and repair. Astronauts retrieved and repaired the Solar Maximum Mission satellite, which, once again, is a hard-working sun-watcher. An astronaut team also retrieved two communications satellites that earlier had entered useless orbits when their booster rockets failed.
But launch-pad delays and the discovery of hundreds of loose tiles on the shuttle Challenger, among other things, forced NASA to cancel or postpone five of the 10 shuttle flights originally planned for 1984. Indeed, the launch of the first Department of Defense (DOD) shuttle flight was moved from December to Jan. 23 because of Challenger's tile problem.
Now NASA anticipates a more successful launch year. One reason is the DOD's agreement to yet another delay in the military shuttle flight schedule.
Postponement of the first shuttle mission from Vandenberg Air Force Base in California has relieved pressure on the overall shuttle manifest. Originally due to launch Oct. 15, the shuttle Discoverer now won't leave the pad at Vandenberg before Jan. 29, 1986. This means that NASA doesn't have to deliver Discoverer to the West Coast until September, instead of early in May. Thus Discoverer can take on two additional flights in mid-1985, a capability that helps avoid delays due to Challenger's problems.
Air Force and NASA officials say that the Vandenberg launch was postponed to smooth the shuttle schedule rather than because of any slippage in Vandenberg preparations. The Shuttle Activation Task Force commander, Col. Walter Yager, has said that preparations at his end are only two to three weeks behind schedule. The three-month launch postponement is unlikely to delay the second Vandenberg shuttle mission, now scheduled for September 1986.
On the other hand, NASA would have been hard pressed to meet its 1985 commitments if Discoverer had to go to Vandenberg in May. The original 1985 manifest lists a dozen nonmilitary flights, with all four shuttles participating. Discoverer and Challenger were to be joined by the new Altantis and a refitted Columbia. But, in order to restick hundreds of loose tiles on Challenger and make the spacecraft ready for a scheduled February mission, technicians were diverted from Columbia. NASA said it was uncertain when Columbia would be available. Now Discoverer can pick up the load.
At this writing, NASA mission planners were still revising their 1985 schedule. But NASA public information officer Debra J. Rahn said there seems little doubt that 1985 will be a 12-mission year. Besides routine satellite launches, the manifest includes several critical elements.
The two remaining Tracking and Data Relay Satellites -- TDRS-B AND TDRS-C -- are to be orbited. These serve shuttles and some unmanned satellites, such as the Landsat earth-resources survey craft. Perched in geosynchronous orbit, they are to provide virtually continuous radio contact with ground stations. Shuttle crews, for example, would not have extensive periods when they lose contact with Houston controllers because they are out of sight of a ground tracking station.
The first TDRS went into a useless orbit after shuttle deployment April 4, 1983, when its Air Force-supplied booster rocket -- called an Inertial Upper Stage (IUS) -- misfired. Ground controllers used the satellite's on-board maneuvering rockets to edge it into its proper orbit some 22,300 miles above the equator.
At this writing, Challenger was to take TDRS-B into space Feb. 20. Schedule planners were still looking for a slot for TDRS-C, which had been due for launch by Atlantis Nov. 27.
At least two TDRS are needed for the most efficient use of the European-built Spacelab -- the shuttle-carried laboratory in which astronauts can work in a ``shirt-sleeve'' environment. Three Spacelab missions are scheduled this year. These missions are critical for NASA. Its European space partners, displeased with past delays, have said they consider NASA's good faith to be on the line in maintaining its Spacelab flight commitments.