The cancellation of a planned shuttle servicing mission to the Hubble
Space Telescope, in the wake of the Columbia shuttle tragedy, generated
much outcry from scientists, the public, and some lawmakers, and caused
NASA to revisit the issue. Yet at a February 2 House Science Committee
hearing, committee members and witnesses struggled with questions of
whether saving the Hubble would be worth the costs, and what exactly
those costs would be. By the committee's estimates, the costs for a
shuttle servicing mission, a robotic servicing mission, or a new spacecraft
to "re-host" some new or upgraded Hubble instruments, each
would be in the range of $1-2 billion. The hearing took place the week
before President Bush released his FY 2006 budget request, which does
not include any funding for a Hubble life-extension mission (see http://www.aip.org/fyi/2005/019.html.)
The hearing, Chairman Sherwood Boehlert (R-NY) explained, was intended
to address three fundamental questions: "Is it worth saving the
Hubble even if that means taking money away from other NASA programs
such as exploration? Second, and more narrowly, we need to ask: Is it
worth saving the Hubble even if that means taking money away from other
NASA science programs? And finally, if the answer to either of those
questions is yes, then we need to ask: What's the best way to save the
Hubble - or at least its science - in terms of cost and risk."
Boehlert declared himself "an agnostic" on the issue.
As chair of the National Research Council panel that evaluated options
for Hubble, Louis Lanzerotti, of the New Jersey Institute of Technology,
expressed his panel's view that NASA should commit to a shuttle servicing
mission (see http://www.aip.org/fyi/2004/158.html).
He added, however, that if such a mission was not possible, the astronomy
community should review the trade-offs involved in other options, such
as "re-hosting" Hubble instruments on a new spacecraft. Nobel
Laureate Joseph Taylor of Princeton University, co-chair of the most
recent National Academy of Sciences "decadal survey" recommending
ten-year priorities for astronomy and astrophysics, testified that the
survey committee had assumed a shuttle servicing mission to Hubble would
take place. It would be difficult, he said, to estimate how the premature
loss of the Hubble might alter the committee's priority list.
Paul Cooper of MD Robotics, the company contracted to build the arm
for robotic servicing of the Hubble, argued that a robotic servicing
mission was "the right thing to do." Colin Norman of the Johns
Hopkins University, lead scientist on a proposal to re-host Hubble instruments
on a "Hubble Origins Probe" (HOP), called for continuing "the
Hubble adventure" with the HOP. Space Telescope Science Institute
Director Steve Beckwith stated that it was "essential to complete
the Hubble mission," noting that the proposed James Webb telescope
(planned for a 2011 launch) was intended for several years of observing
overlap with Hubble. "It would be best to have both," Taylor
agreed.
However, the witnesses were less sanguine when Boehlert challenged
them by asking their opinions if a Hubble servicing mission deprived
other NASA science programs of $1 billion or more. Taylor pointed out
that many of the important scientific questions waiting to be addressed
were outside the Hubble's capabilities, and stated that neither a servicing
mission nor rehosting Hubble instruments on a new platform should be
given higher priority than new science missions. Lanzerotti said he
would "have serious questions" if the $1 billion was taken
from other science programs such as Earth science or solar-terrestrial
programs.
Beckwith questioned the $1 billion figure, remarking that in the past,
NASA charged only several hundred million dollars to the science budget
to fly shuttle servicing missions to Hubble. If NASA was now charging
$1 billion to science, he said, "I'm not sure how I'd come down.
That's never been the case in the past." Taylor and Beckwith agreed
that if the costs were in the $300-400 million range, a Hubble servicing
would be "well worth the cost," but if it would cost $1-2
billion, the astronomy community should review the issue. Lanzerotti
asked why NASA would charge $1 billion for a shuttle mission to the
Hubble but not for shuttle missions to the International Space Station.
"There's a serious accounting issue here that doesn't compute properly,"
he commented. The committee's Ranking Minority Member, Bart Gordon (D-TN),
noted that the Government Accountability Office examined NASA's cost
estimate for a shuttle servicing mission and found the space agency
could not provide complete documentation for that figure. Gordon also
stated that, at a February 27, 2002 hearing, the NASA Administrator,
Sean O'Keefe, stated that the cost of a Hubble shuttle servicing mission
had been "grandfathered in" to the five-year budget plan for
the Office of Space Flight. "Where did the money go?" he asked.
But Boehlert pointed out that the statement from O'Keefe came at a time
when NASA was beginning a process of changing its accounting structure
to "full cost" accounting.
Regarding the option of re-flying some upgraded Hubble instruments
on an HOP, Taylor, Lanzerotti, and Norman all concurred that the possibility
should be reviewed and prioritized by the astronomy community. Lanzerotti
expressed concern about the "very large, significant" science
gap between the time Hubble failed and the HOP was operational. Norman
argued that with its greater capabilities, HOP could complete the science
that Hubble would have performed during that gap period in a few months.
But Taylor noted that while it would do some things faster and better,
the HOP "doesn't do a lot of things as well as the current Hubble."
The great value of Hubble, Beckwith added, was as a general-purpose
observatory, with the capability to "respond to discoveries we
can't foresee." Taylor also raised the concern that if the science
gap extended to five years, it could mean "the loss of people in
the community." Asked about the lifetime of HOP, Norman replied
that it was not intended to be robotically serviceable but would have
a minimum lifetime of five years.
Cooper contended that there would be value to a robotic Hubble servicing
mission beyond simply saving the telescope, as a learning experience
for future spacecraft servicing needs. "I buy that argument,"
said Rep. Dana Rohrabacher (R-CA); "I believe in pushing the envelope."
But Lanzerotti worried about "using Hubble as a target vehicle"
to practice servicing maneuvers, and argued that future spacecraft would
probably be designed differently, making experience with the Hubble
"probably not directly applicable."
While the President's FY 2006 budget request contains no money for
a servicing mission, the appropriations process now moves to Congress,
where the Hubble has many supporters. In fact, on the day the budget
request was released, key Senate appropriator Barbara Mikulski (D-MD)
issued a statement that said, in part, "...I am so disappointed
that President Bush has failed to include funding in this year's budget
for a servicing mission that would extend the life of the Hubble. I
led the charge last year to add $300 million to NASA's budget for a
Hubble servicing mission, and I plan to do it again. I will fight in
the United States Senate this year to fund a servicing mission to Hubble
by 2008."
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