The Uncertain Future of an Eye in the Sky

NY Times ^ | DENNIS OVERBYE

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BALTIMORE - The Johns Hopkins campus here was in bloom in early May when 120 astronomers gathered at the Space Telescope Science Institute. But although spring was around the scientists, winter was on their minds. They were assembled to discuss the uncertain future of the Hubble Space Telescope.

Many could remember the planning meetings for the telescope 20 years ago. Now some are gray, with potbellies, making jokes about their blood pressure and carrying pictures of grandchildren. Meanwhile, the end may be near for the telescope that has defined their era.

"This is a particularly poignant time in Hubble's history," Dr. Steven Beckwith, the telescope institute's director, told the astronomers. Launched into orbit in 1990, Hubble has dominated astronomy, beaming back crystalline images of the cosmos unsullied by atmospheric haze or turbulence. Astronomers say it is still at the peak of its powers.

But in January NASA's administrator, Sean O'Keefe, citing safety concerns, canceled a mission scheduled for next year that would have sent astronauts on the shuttle to install two new instruments on the telescope and change its gyroscopes and batteries. Without maintenance visits like this, the telescope will probably die within three years.

Mr. O'Keefe's decision provoked outcries from scientists, the public and Capitol Hill. Last month the National Research Council appointed a committee of scientists and engineers, led by Dr. Louis J. Lanzerotti of Bell Laboratories, to assess the relative risks and rewards of further Hubble servicing missions.

Meanwhile, NASA officials said recently that they were considering sending robots to service the telescope. The agency has announced that it will request proposals for a Hubble telescope "robotic servicing/deorbit module" next month.

NASA is already committed to sending a robotic rocket to dock with the telescope at the end of the decade and then drop it out of orbit safely into the ocean. At the meeting here, Dr. John M. Grunsfeld, NASA's chief scientist, described the agency's engineers as "supercharged" at the prospect of developing a robot to service the telescope.

He said recent experiments with the Hubble mock-ups used to train astronauts indicated that robots would be able to supply electricity and gyroscopic stability, and even to replace scientific instruments.

"I hope that's happy news," said Dr. Grunsfeld, an astronomer and astronaut who has been to Hubble twice. But some astronomers were skeptical that robots could do everything the astronauts were planning to do on the telescope.

The new instruments for the Hubble, which are already built, are a wide-field camera and an ultraviolet spectrograph, the Cosmic Origins Spectrograph. While the camera is designed to slide in and out of the telescope like a piano-sized drawer, the spectrograph must be installed inside doors, which house other instruments and have been balky in the past.

During the meeting, Dr. Rodger I. Thompson, an astronomer from the University of Arizona, asked a speaker, Dr. John L. Tonry from the University of Hawaii, if he would let a robot open Hubble's doors, "with the risk that they won't be able to be closed again."

Dr. Tonry responded that a robot would have more time to work than an astronaut would have, and that operators on the ground would be in control of the robots anyway.

Dr. David S. Leckrone, the Hubble project scientist at the Goddard Space Flight Center, said, "We won't open the doors unless we are confident we can close them."

Much of the three-day meeting was a recital of Hubble's recent accomplishments, in fields from planetary science to the evolution of the universe, as a way of advertising its unique capabilities.

For example, with its clear vision, Hubble has picked out the glint of the exploding stars known as supernovas, billions of light-years out in space and time. This year, using these cosmic disasters as distance indicators, a team of Hubble astronomers confirmed the strange discovery six years ago that some "dark energy" was accelerating the expansion of the universe.

"We're not interested anymore in asking 'Is the universe accelerating?' " said Dr. Tonry of Hawaii, discussing this finding. "We want to know why it is accelerating. What is this stuff?"

The race is on, he said, to pin down the properties of dark energy by finding more supernovas out in the void before Hubble dies.

Another of Hubble's superpowers is its ultraviolet vision, which lets the telescope detect electromagnetic radiation with wavelengths shorter than visible light, an ability important in figuring out what the universe is up to.

For example, most of the atoms in the modern-day universe appear to be missing; stars and galaxies account for only about a third of what cosmologists calculate must exist. The rest of the atoms are thought to be drifting in space and detectable only by the way they absorb ultraviolet light from distant stars. Tracing this invisible "cosmic web" of material was to be the job of the Cosmic Origins Spectrograph.

"It's 13 billion years after the Big Bang and we don't know where our baryons are," said Dr. John S. Gallagher 3rd, of the University of Wisconsin in Madison, using the technical term for stuff made of protons and neutrons.

Ultraviolet rays are blocked by the atmosphere and so when Hubble goes, they could be out of sight for a long time.

The prospect of Hubble's demise weighed on the participants. In a rambling discussion that began with a panel session one afternoon and continued through the meeting, some astronomers urged the institute to give priority to ultraviolet observations in the telescope's remaining years.

But others suggested that the procedures for allocating time on the telescope be altered to allow for riskier projects, or a greater diversity of observations. For example, Dr. Eva K. Grebel, from the University of Basel, argued for more smaller projects.

Dr. Robert P. Kirshner, from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., said, "We have to be fairly ruthless; we won't be able to do all the good things."

Dr. Beckwith responded that no field should have an automatic claim on telescope time, and that it was a "misconception" to regard any one of Hubble's capabilities as more important than any other. He defended the present system of allocating telescope time, saying it had "a history of providing good science."

Dr. John Huchra of the Harvard-Smithsonian Center, the departing chairman of the Associated Universities for Research in Astronomy, which runs the institute for NASA, urged borrowing a page from the past. In the 1980's, astronomers, anticipating Hubble's launching, held meetings to identify critical projects for the telescope.

"Always assume this is your last clear night on the telescope," Dr. Huchra advised. "Set aside time for things you'd be embarrassed not to have done."

Dr. Kirshner of Harvard was one of many at the meeting who remembered the early planning for the telescope.

"Maybe it's my age, but I'm really beginning to think I know what it feels like to be the Hubble telescope," he said. "One faces a finite future."

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A star cluster as seen by Hubble last year.

The Hubble Space Telescope in 1997.

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PING

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