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."