Can the Hubble Telescope Be Saved?
NASA's decision to stop servicing the Hubble Space Telescope has agitated astronomers and the general public
In the latest repercussion from the disintegration of the space shuttle Columbia over Texas last year, a huge question mark now hangs over the future of one of astronomy's most valuable assets, the Hubble Space Telescope. On 16 January, NASA administrator Sean O'Keefe announced the cancellation of a long-planned servicing mission to the orbiting telescope by a shuttle. O'Keefe, who took personal responsibility for the decision, says it was based on the difficulty of servicing the telescope within the shuttle safety limits established by the report of the Columbia Accident Investigation Board, released last August [see "How to Fix the NASA Disaster," IEEE Spectrum, October 2003, pp. 10-12].
The report demanded that any shuttle not going to and from the safe haven of the International Space Station (ISS) be fully capable, on its own, of inspecting and repairing any damage to its thermal protection system. As the only non-ISS mission on the books, the Hubble mission would require the development of a slew of safety-related technologies. And because the shuttle fleet will be decommissioned after the construction of the ISS is completed, these technologies would likely never be used again.
O'Keefe's declared rationale for the cancellation was that the combination of the increased development cost and risk did not justify another servicing mission to the aging Hubble. NASA and the astronomical community, he argues, would be better served by focusing on the James Webb Space Telescope, planned for launch in 2011.
The cancellation means not only that two completed instruments intended to dramatically upgrade Hubble's scientific abilities will remain on the ground for the foreseeable future, though US $200 million has already been spent to build them, but that vital maintenance on Hubble gyroscopes and batteries also will go undone. Estimates vary from three to five years on how long Hubble can continue to produce its sensational images without repairs [see photo, " Galactic Nebula"].
Cancellation of the Hubble servicing provoked a howl of protest from astronomers around the world, which spilled over into editorials and online petitions to keep the telescope alive. The decision, which came days after U.S. President George W. Bush announced he was directing NASA to embark on an ambitious strategy for human exploration of the Moon and Mars, left an impression that NASA was going to bleed its space-science programs dry in an effort to fund its new mandate.
"People are worried about the future and the signals sent about space science," says Steven Beckwith, director of the Space Telescope Science Institute in Baltimore, Md., which is responsible for Hubble's scientific mission. While Beckwith acknowledges he's not an expert on the safety challenges involved, he told Spectrum that it's "somewhat remarkable that NASA can set out on a bold new adventure and yet not do something it's done [successfully] four times before" [see photo, " Too Dangerous?"].
The decision had nothing to do with any attempt to raid the space-science budget, says Anne Kinney, director of NASA's astronomy and physics division. She stresses that it was driven purely by the accident board's safety recommendations. While Kinney admits to feeling, as a practicing astronomer herself, "torn" by the decision, she stresses that NASA is not simply abandoning the Hubble; work has begun on finding ways to stretch the operating lifetime of the telescope, including making observations with only two operational gyroscopes. (It's now down to three, the minimum number it was designed to use; it originally had six gyroscopes to orient itself in space.) She says that it's "not unlikely we'll see Hubble operate through 2007-2008."
It has been suggested that Hubble could be upgraded and serviced by an all-robotic mission, but Kinney dismisses that as unfeasible. "You'd need to develop something lickety-split" that's currently beyond the state of the art, she told Spectrum , pointing out that today's robots are incapable of "fixing your washing machine," let alone making delicate repairs on a telescope the size of a school bus.
James Benson, CEO of SpaceDev, in Poway, Calif., agrees. His company is working with the U.S. Air Force to develop a space tug of the sort that will ultimately be used to de-orbit Hubble once it can no longer serve its purpose. Benson says robotic servicing is "so complicated and would require so much brand-new engineering it would border on science fiction."
As for another idea for extending Hubble's life--bringing it to the ISS for repairs--Benson says this would require an enormous amount of energy because the two are in completely different orbits. "You'd need a massive rocket motor that's beyond reality," he says.
Still, all hope for a longer-lived Hubble is not lost. The influential U.S. Senator Barbara Mikulski, a Democrat from Maryland, not coincidentally the home of the Space Telescope Science Institute, has intervened on behalf of the telescope. In a response to her letter, O'Keefe stated on 28 January that he had asked Admiral Harold W. Gehman, the chairman of the shuttle accident board, to review the Hubble servicing mission. If Gehman feels that the Hubble can be serviced without compromising astronaut safety, it may yet continue to be the darling of astronomers well into the next decade.