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."
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