Liftoff of the Astro-1 space shuttle mission has unofficially been postponed until at least Dec. 1 because of persistent fuel leaks on Columbia, raising fears among mission scientists that the astronomy project may be further postponed into next year or even canceled.
Disappointed Astro-1 scientists -- including teams from the Johns Hopkins University and Goddard Space Flight Center -- were told yesterday that NASA had reshuffled the mission to third in line, behind the launch of the Ulysses solar probe aboard Discovery and a military mission on Atlantis.
Several expressed a concern that hasn't surfaced since the uncertain days following the Challenger explosion in January 1986: that the four-telescope observatory might never embark on its mission to probe the invisible universe of X-rays and ultraviolet light sources.
"As long as we're on the pad, we're safe, and as long as we're in the cargo bay, we're OK," said Peter J. Serlemitsos, lead scientist for Astro's X-ray telescope. "But if we're removed from the bay for repairs to Columbia, I'm going to be worried."
The $150 million observatory was originally set for liftoff in 1986, and it has suffered through four aborted launch attempts beginning May 29 -- three times because of fuel leaks and once because of a faulty communications line to the Goddard-built X-ray telescope.
The latest delay on Sept. 17 followed more than three months of intense efforts by NASA engineers to locate and fix the multiple leaks, which appear only when the supercold liquid hydrogen is being loaded into Columbia's huge external fuel tank just hours before launch.
"What we're really worried about is that Columbia may need major work. If that happens, we could find ourselves back in the hangar and waiting," said Arthur F. Davidsen, the Hopkins astronomer who heads the Hopkins Ultraviolet Telescope project on Astro-1.
One "frightening thought" is that the mission might have to wait until after a planned overhaul of Columbia, NASA's oldest shuttle, next spring, or squeeze into line for a launch aboard the already-booked Discovery or Atlantis, Dr. Davidsen said.
Discovery must be launched with Ulysses between Oct. 5 and 23 or wait 13 months in order for the probe to be looped into the proper trajectory around Jupiter and back toward the sun, and Atlantis is tentatively scheduled for launch Nov. 1.
"I think the general sense is that we've got two good orbiters and a high probability of success for those missions," said NASA spokesman Mark Hess, who added that an official launch manifest would be released today. "We've got some work to do on Columbia."
The National Aeronautics and Space Administration plans to conduct a rare and expensive test-fueling of Columbia as early as this weekend, with television cameras placed in the area of the shuttle's main engines to visually detect escaping hydrogen gas.
If that test pinpoints the fuel leak and technicians can fix it on the pad, Astro-1 may fly as early as Dec. 1. If Columbia must be rolled back to the hangar for repairs, as it was in June, Astro's future becomes lessclear.
Stephen P. Maran, a Goddard senior staff scientist and a member of the Ultraviolet Imaging Telescope science team, said Astro might appear vulnerable because "it doesn't provide an ongoing presence in space like Hubble and it has a relatively small user community, half of whom are federal employees."
But, Dr. Maran quickly added, "I don't think NASA wants to give up, it would really send the wrong message at a critical time, and Astro still promises some great science."
Project officials at NASA agree. "There's been too much human life and sweat involved to walk away from it," said Edward J.
Weiler, program scientist for both the Astro project and the Hubble Space Telescope.
"I can't envision any scenario that might cancel Astro, although I know some of my friends outside don't feel that way," he said. "This is first-rate science, never done before, and NASA values that."
The Johns Hopkins scientist most affected by the delays of Astro-1 is Samuel T. Durrance, an astrophysicist who began training as an astronaut in 1984 to operate the telescopes in orbit.
"The most likely scenario is they'll find out what the latest leak is and fix it on the pad," said Dr. Durrance yesterday from the Johnson Space Center in Houston. "But, after all the problems, I recognize that any thing's possible."
Dr. Durrance, who marked his 47th birthday Monday, the day of the latest launch scrub, plans to relocate his family back to Lutherville next week from Houston, then return in a month to a rented apartment near the space center.
His son, Benjamin, 8, has been living with friends in Lutherville the last two weeks so he could begin third grade, and his wife, Rebecca, "is ready to come home. It's been a long haul."
But Dr. Durrance described himself as "in pretty good spirits. And I'll be ready when they finally light the solids [solid rocket motors] and get this thing up there."