New hope for the troubled Hubble
But servicing the space-based telescope is affecting other high-priority initiatives as NASA funding gets tighter.
In a space saga worthy of the "Perils of Pauline," the on-again, off-again Hubble Space Telescope appeared to be headed for an untimely end. Victimized by the Columbia shuttle disaster, not to mention budget pressures, one of the most highest-profile ambassadors of the National Aeronautic and Space Administration appeared doomed.
Now, Hubble's prospects are brightening. What was to be a $175 million effort to "deorbit" Hubble has become a $291 million program to keep alive the option of servicing and upgrading the telescope so it can continue functioning at least until 2010. A final decision will depend on how well the shuttles perform when they return to flight, now scheduled for mid-July.
"All of us are very happy, excited, and gratified," says Preston Burch, program manager for the telescope at NASA's Goddard Space Flight Center in Greenbelt, Md. "But we're also aware of the caveats. It's no slam-dunk."
The latest effort, however, may also illustrate the old warning: Be careful what you wish for, you may get it.
Much of the current space-science program in the United States was planned at the end of the 1990s in a fiscal universe far more flush with cash than today. No one foresaw 9/11, the wars in Afghanistan and Iraq, and the space shuttle Columbia disaster and its subsequent demands for improvements to the remaining shuttles. In addition, this year's NASA budget contains some $426 million in congressional "earmarks" - spending neither the agency nor the administration sought.
Thus, helping Hubble affects several other projects identified as high priorities in the space community's "Decadal Survey," published in 2000. NASA administrator Michael Griffin has deferred work on next- generation space telescopes such as the Space Interferometer Mission and the Terrestrial Planet Finder to keep the Hubble service mission alive.
Some astronomers who support a servicing mission aren't happy about the deferments. But "there will be plenty more chapters to this story," says Robert Kirshner, president of the American Astronomical Society.
Given the demands of the shuttle's return to flight, President Bush's vision for manned space exploration, and Congress's own fondness for certain projects, the addition of a Hubble servicing mission makes NASA's budget choices increasingly stark.
As if to underscore the point, the administration's budget request for NASA at the beginning of this year set no money aside to service Hubble. NASA's former administrator had balked at mounting a previously scheduled servicing mission after the Columbia disaster, concluding that the mission was too risky. Instead, the agency was expected to figure out how to deorbit the telescope safely in 2007.
Nevertheless, Hubble had legions of supporters. The American Astronomical Society, for example, threw its support behind a servicing mission. In a March statement, it urged NASA to "include the space-science communities in an assessment of the relative scientific merits of all impacted missions" if the mission produced "adverse budget consequences."
What would astronomers get from a servicing mission? Two new cameras with an ambitious research agenda, according to Steven Beckwith, director of the Space Telescope Science Institute in Baltimore.
A new wide-field camera would push astronomers' views of the universe close to its observable edge. In terms of age, the telescope would serve as a "way-back" machine, allowing researchers to view the universe when it was less than 10 percent of its current age - nearly 14 billion years. Observing the earliest stars and galaxies would fill in a significant gap in understanding the evolution of the universe.
In addition, Dr. Beckwith says, astronomers would continue to search for ever earlier supernovae - exploding stars whose light serves as "standard candles" for determining distances and the universe's expansion rate. Such studies resulted in the discovery six years ago that the universe is expanding faster than conventional explanations could account for. This prompted astronomers to invoke "dark energy," which opposes gravity. Astronomers will be comparing the characteristics of recent supernovae with those of earlier ones they detect.
The camera also is expected to play a role in discovering and studying planets around other stars - currently the domain of ground-based telescopes.
In addition, astronomers plan to install a new, more sensitive and efficient spectrograph. Its main goal is to locate a significant fraction of "normal" matter that is still missing from observational efforts to account for the densities of mass and energy in the universe. One likely candidate for this missing matter: relatively cool gas threading its way through space between galaxies and clusters of galaxies.
"We'll be tracing this cosmic web," Beckwith says. It should appear as "filaments, balls, and stringy things" arcing along paths similar to those that galaxies and galaxy clusters themselves trace in a universe whose large-scale structure vaguely resembles the voids and walls of an enormous sponge.
For longevity's sake, mission planners also will switch out batteries, replace some of Hubble's guidance and pointing controls, and fit the telescope with a motor to control its final reentry and destruction in Earth's atmosphere.
Much of the hardware already is in hand, Mr. Burch notes. The batteries are in a freezer. The spectrograph is in an atmosphere-controlled holding unit. Work on the wide-field camera continues, only because its contract was put out to bid about a year later than the spectrograph's.
The one element still under consideration is the rocket motor the team would use to deorbit the telescope. The team at Goddard developed a preliminary design a couple of years ago, he says. Now it needs to be refined. Everything could be ready for a mission in 2007, assuming all goes well with the rest of the shuttle program.
For all of the concern about budget conflicts between a servicing mission and other space-science priorities, Dr. Beckwith notes that NASA always has committed itself to a controlled, safe reentry for Hubble. In the end, it will have to do something to ensure pieces don't land in highly populated areas.
After the Columbia tragedy, engineers looked at several options. A robotic mission could cost as much as $1.5 billion. An expendable-rocket rendezvous brought the price tag down to about $750 million. While no formal cost estimate has been submitted yet for using the shuttle, Beckwith suggests that the complete servicing mission 8could run about $600 million. In exchange, he says, astronomers would get a telescope more powerful, more efficient than today's Hubble lasting into the next decade and at a price that undercuts the nearest competitors for a deorbit-motor-only mission.
"That's good for astronomers and good for the taxpayers," he adds.