Scientists who want a robotic repairman to fly to the rescue of the Hubble Space Telescope shrugged off news yesterday that a confidential study done for NASA last summer called a robot mission one of the most difficult and risky options for saving the observatory.
The director of the Space Telescope Science Institute in Baltimore said NASA knew about the study Aug. 9, when NASA Administrator Sean O'Keefe told cheering scientists and engineers at the Goddard Space Flight Center to push ahead with the design of a robotic repair mission.
"O'Keefe has said, 'Of course this is ambitious and difficult, and looks impossible at the outset. But our folks have done the impossible before,'" said Steven V.W. Beckwith, the telescope institute's chief.
$300 million review
Since O'Keefe's August directive, NASA scientists and engineers have engaged in an accelerated $300 million design review to determine by March the nature, preparation time and cost of a robotic mission. By September, they will complete another review, leading to a "go" or "no-go" decision.
National Public Radio aired a segment yesterday describing the confidential report to NASA assessing alternatives for Hubble's future. NASA commissioned California-based Aerospace Corp. to produce the report at the end of May, and the company delivered an executive summary to the space agency Aug. 3.
Aerospace Corp. spokesman George Torres said yesterday that the final report will be delivered to NASA within a week.
The space agency had to scrub a long-planned space shuttle mission to repair and upgrade Hubble after the explosion of Columbia, which killed seven astronauts Feb. 1, 2003, and forced NASA to ground the fleet.
Hubble was launched in 1990, and since its first major repair in 1993 has been a steady source of groundbreaking observations that have rewritten the history of the universe. NASA's original plan to let it die in orbit drew spirited and ultimately successful protests from the telescope's scientific and political backers.
Aerospace Corp. study
The Aerospace Corp. study considered at least 20 engineering alternatives for Hubble. They included allowing the observatory to go dark and fall from orbit, robotic repairs and scientific upgrades, and a complete servicing mission by shuttle astronauts.
O'Keefe has all but rejected a manned repair mission to Hubble because of safety criteria established in the aftermath of the Columbia accident.
The report by Aerospace Corp. concluded that robotic missions would cost at least $1.3 billion and take five years to fly -- too late to save Hubble, which is expected to fail by 2008. The report said the mission would offer only "limited" value, with a 50 percent risk of failure.
Far less risky, the study found, would be a project to design, build and fly a new telescope to carry two new Hubble instruments that were to have been installed on the canceled upgrade mission. The Cosmic Origins Spectrograph and Wide Field Camera 3 were built at a cost of $167 million.
The Aerospace study estimated the cost of this "rehosting" mission at $1.9 billion to $2.3 billion, with a likelihood of success approaching 80 percent.
David Leckrone, chief project scientist for Hubble at Goddard Space Flight Center in Greenbelt, where much of the engineering is under way, said yesterday he remains confident that a robotic repair and upgrade for Hubble is feasible.
"This is a project being implemented by the same people who gave you the first [Hubble] servicing mission in 1993," he said. They analyzed mirror flaws that had nearly crippled the $2 billion telescope, designed corrective optics and had astronauts install them.
It was all done on a three-year schedule, Leckrone said, "and it worked great."
Aerospace Corp. "did a great job, given the short amount of time they had to do this study," he said. "But I don't think they gave enough credit for the advanced state of robotic technology."
The Aerospace study apparently assumed that the robotics would have to be designed and built from scratch, he said. But NASA is already testing a Canadian-built robotic arm built for installation on the International Space Station. NASA is using it to practice the work it would have to do on Hubble.
Leckrone said Aerospace also gave insufficient weight to the difficulty of designing a new telescope to work with the two stranded Hubble instruments.
Such a telescope could be built, he said, but "it would be costly, and I think it would take quite a lot of time to do it, and you would end up with nothing better than what we have in orbit [Hubble]. It's the weakest part of their study."
At Aerospace Corp., Torres declined to comment or answer specific questions about the study because NASA had not seen the full report.
Leckrone said a robotic mission has the added benefit of advancing robotic science. That is crucial to President Bush's space exploration initiative, which would demand unmanned rendezvous, docking and repair technologies that don't yet exist.
'Too early to conclude'
Beckwith, at the Space Telescope Science Institute, said NASA has put its best people on the design work and given them the support they need.
"Now it will be up to the team to show what they can do," he said. But "it's too early to conclude it can't be done on the basis of these reports."
Meanwhile, another study of Hubble rescue options, this one ordered by Congress, is scheduled for release tomorrow. A preliminary version of the report by the National Academies, leaked in July, said NASA should pursue a robotic solution while keeping all options open, including a manned shuttle mission.