'We deliver'

The rescue of the $100 million Tracking and Data Relay Satellite (TDRS) adds new luster to the shuttle astronauts' ebullient slogan ''We deliver.'' The slogan had seemed slightly tarnished when a booster rocket put the TDRS into a wrong orbit after its deployment from the space shuttle Challenger April 4. But painstaking use of attitude control thrusters, which burned for a total of 44 hours and 5 minutes, has put the satellite where it belongs - 22,367 miles above the equator over Brazil.

NASA engineers and their colleagues working for the spacecraft builder and operator are to be congratulated on their ingenuity and persistence. For NASA, this has been perhaps the trickiest rescue operation yet undertaken.

But NASA can take only momentary satisfaction in its success. The entire incident has shown how close to the margin the space shuttle system is running when it comes to providing service on schedule.

The TDRS communications system is to include two satellites positioned 130 degrees apart above the equator. They are to keep track of, and provide communications for, a number of satellites including the Landsat 4 Earth resources vehicle and the shuttle itself. By acting as relays, TDRS satellites can maintain almost constant communication between ground stations and satellites even when the latter are out of range of ground antennas. They can also handle massive data flows such as those expected from the European Spacelab - an orbiting laboratory in which scientists will work - to be carried on the ninth shuttle mission in September.

Some missions, such as Spacelab, depend critically on this new communications system. Happily, now, one satellite should be available. Nevertheless, some Spacelab experiments will have to be curtailed owing to lack of the second relay.

Timing of the satellite launch was upset by delays in the sixth shuttle mission which deployed it. This removed some of the safety margin allowed should malfunctions develop, as they did. It was the booster rocket supplied by the Air Force which failed. This unit had not been adequately tested. Now deployment of the second TDRS is awaiting correction of the booster problem. No other rocket system of sufficient power is available to carry a 5,000-pound communications satellite from the low orbit where it is placed by the shuttle to the 22,300 -mile height where it will operate.

NASA officials have repeatedly noted that tight budgets have forced them to cut corners. There is inadequate backup to compensate for such setbacks as shuttle launch delays or the booster failure. Indeed, the rescue of the first TDRS was possible only because this particular satellite carried extra fuel to support a planned commercial radio relay which had been canceled before launch. This fuel excess allowed the thrusters to boost the satellite to the right orbit and still leave enough fuel for the satellite's 10-year mission.

Congress should remember this in considering NASA requests for adequate shuttle funding. There is no real saving in restricting shuttle funds to the point where the enormous investment in the shuttle system cannot be used to best advantage.

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