Details Emerge in Robotic Plan to Service Hubble
BALTIMORE - An astronomer-astronaut who has journeyed twice to work on the Hubble Space Telescope said Monday that NASA Administrator Sean O'Keefe is conceptually sold on the idea of a robotic servicing mission.
Former astronaut John Grunsfeld, now NASA's chief scientist, also provided new details for how the possible reprieve came about. He discussed the pros and cons of robotic versus astronaut servicing and ticked off a priority list for any robotic effort.
Hubble has just two or three years of observing left in its batteries and pointing gyroscopes. A decision on a possible mission is expected by early June.
While astronomers and the public have spent the past three months bemoaning O'Keefe's unilateral decision not to send a space shuttle back to repair and upgrade the orbiting observatory, Grunsfeld was contemplating alternatives. He has personally grappled with installation of new Hubble equipment during daring space walks.
O'Keefe told lawmakers on April 21 that the robotic mission looked promising based on 26 responses to a call for ideas.
A robot can definitely do the work, Grunsfeld said. But if the telescope is to be saved, a final commitment must be made soon to allow time to plan a mission unlike any ever undertaken.
Lobbying the chief
NASA announced Jan. 16 that a crewed mission to fix Hubble and add new and powerful instruments would be cancelled due to safety concerns presented in the wake of the Space Shuttle Columbia disaster.
"The decision hit me in the head like a two-by-four," Grunsfeld told astronomers gathered here at the Space Telescope Science Institute (STScI) to ponder how to make the best use of Hubble's final years. After a couple weeks of depression over O'Keefe's initial decision, Grunsfeld was commiserating with a NASA engineer and learned that robotic servicing might be practical.
So he took the idea straight to the top.
Grunsfeld and Ed Weiler, NASA associate administrator for space science, put the suggestion to O'Keefe. They argued that the technology needed to carry out space-based robotic repair fit neatly with the requirements of President Bush's new vision of developing robotics and other capabilities necessary for setting up a Moon base and sending astronauts to Mars. That means it would fit logically within the space agency's budget, which Bush wants restructured to support the new long-term goals.
"Mr. O'Keefe was totally sold," Grunsfeld said. "This took about five minutes."
Already, Grunsfeld said, equipment used by astronauts to train for past Hubble servicing missions has been shipped to NASA's Goddard Space Flight Center and two other locations where space-based robotics were under development for other purposes.
No decision has been made on how ambitious the mission might be, should O'Keefe approve it.
Meanwhile, astronomers had just been coming to grips with the expected loss of Hubble. Several of them reiterated at the meeting, a four-day discussion about which observing projects Hubble should undertake in an abbreviated life, why Hubble is so vital to investigating star and galaxy formation, exploring extrasolar planets and peeking at the earliest epochs of the cosmos.
No observatory seriously planned for launch anytime in the next 10 years can replace the optical and ultraviolet capabilities of Hubble, they said.
"The technology seems to be farther along than I had realized when the idea first came up" for a robotic fixit venture, said David Leckrone of Goddard.
Robots vs. astronauts
"I don't care how we service Hubble" as long as science continues to flow from it, said Grunsfeld, who is trained as an astrophysicist.
It has not yet been determined whether there is enough time to plan for having robots successfully install new instruments that are already built and were intended to make Hubble more sensitive and useful than ever, or if the mission would instead be limited to keeping Hubble functioning at its present ability.
But Grunsfeld said employees at various NASA field centers "are just supercharged" to try and make it all happen.
In an interview, Grunsfeld said there's a clear priority list. The first would be to attach a device of some sort that would ultimately be used to de-orbit Hubble into the ocean. That part of the mission would fulfill a requirement that had already been in place to safely bring Hubble down sometime in the next decade or so.
The second priority: "Don't break the Hubble," he said, on the assumption that it is still operating when the robot arrives.
Third would be to replace the batteries, which are likely to go before the gyroscopes, according to the latest analysis. Replacing the gyroscopes is a close forth on the list.
New batteries and gyroscopes would buy about six years of service from the installation date.
There is a mechanical issue that could work to the favor of astronomers: Gyroscopes might be attached to the outside of the observatory, but that would be less than ideal due to problems of stability. A more stable option would be to mount them inside one of the new instruments and install the whole setup, achieving longer life and much better science, Grunsfeld said.
There are pros and cons to using astronauts versus robots. From experience, Grunsfeld said equipment sometimes gets stuck while being swapped out. Astronauts can feel what's going on, stop, and make adjustments. On the other hand, "robots can do really pure motions." And a robot can remember the exact movements needed to remove a part, then duplicate the motion in reverse to install a replacement.
The process would not be automated. Instead, servicing Hubble would be a bit like an orbital video game.
Grunsfeld explained that the robot would be controlled from the ground, in real time, by someone familiar with the telescope -- perhaps a former Hubble-servicing astronaut like himself. He added that even if a robotic mission did not fully succeed, engineers would learn plenty to apply toward future efforts at remote operations on the Moon and Mars.
"So it's a win-win situation," he said.
Fresh optimism
Astronomers who have felt left out of the decision to cancel the manned servicing mission were delighted to hear the upbeat report on the possible stay of execution for Hubble.
"NASA clearly feels the need to do something," said Steven Beckwith, director of the STScI, which operates Hubble for NASA. Beckwith and his staff were shocked when NASA decided not to send astronauts back to Hubble. He has since been pleased with "an outpouring of public support" for the telescope that he called unprecedented in the world of science.
This week's meeting, the 18th such spring gathering at the STScI, was planned prior to O'Keefe's January announcement. Its title, Essential Science in Hubble's Final Years, turned out to be far more prescient than its planners expected.
Grunsfeld was not on the speaker's list handed out to conference attendees. The astronaut said O'Keefe had wanted to come, "to look all of you in the eyes" and explain the earlier decision not to return to Hubble. But the NASA chief was unavailable, having been called to speak before a Bush commission designed to set a course for meeting the new human spaceflight goals.
Astronomers have been concerned that O'Keefe's decision was not just about safety but was made to help shift the agency's course from science to human exploration. Not for the first time, Grunsfeld said that's not true.
"I got a very clear statement [from O'Keefe] that it was not about the budget," Grunsfeld said.
The decision did reflect the requirements of the CAIB commission that reviewed the Columbia disaster and set guidelines for NASA's return to flight. It also included an extra measure of safety, based partly on what Grunsfeld called O'Keefe's intuition that NASA should have a second shuttle ready to fly a rescue mission in the event the crew of the servicing mission found itself in a faulty shuttle.
Grunsfeld said time was of the essence in the original decision, too. Even if the first shuttle flight occurs next spring, as tentatively planned now, it would be unrealistic to expect that after a few test flights -- in which problems might be discovered causing further delays -- that Hubble could be serviced before its batteries or gyros fail. He said a human journey to Hubble would be at least fifth on the return-to-flight priority list, behind shakeout flights and at least one trip to the International Space Station.
Best bet?
Grunsfeld said a robotic mission is, after considering all the factors, the more likely to be pulled off in time. "If we need to do something, we need to do it fast," he said.
Beckwith, the STScI director, cautiously agreed that a robotic mission might turn out to be the best bet. But he said he press for more than just the installation of batteries and gyroscopes. One of the reasons Hubble is such a great observatory, he said, is that previous missions have added new capabilities. One of the two planned new instruments for Hubble would make it 10 times more capable at infrared observations, other researchers have said.
"We don't know yet what robotic servicing means," Beckwith told his staff. "We should be optimistic."
MORE FROM SPACE.com
Image Albums
Countdowns
Topics
Infographics
