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The arrival of Michael Griffin as new NASA administrator — along with his promise to reconsider the decision to cancel the space shuttle servicing mission to the Hubble Space Telescope once the shuttle starts flying again — makes the immediate future of space astronomy look suddenly much brighter.
Space astronomy’s long term, however, remains problematic. Even if a shuttle servicing mission upgrades Hubble successfully sometime around 2007, the most that mission can accomplish is to extend the orbiting observatory’s lifespan until about 2012. By then — if nothing else is done — the new gyroscopes will begin to fail and the world’s only optical space telescope will again approach the end of its life.
Worse, if the National Aeronautics and Space Administration launches and docks its planned de-orbiting module to Hubble following the shuttle repair mission, the module’s presence will make it impossible for any future servicing missions to dock with the spacecraft.
In other words, the de-orbiting mission — though guaranteeing a safe demise of Hubble — places a fixed and irrevocable death sentence on the iconic telescope.
Hubble’s limited life expectancy is even more significant because, due to decisions of the astronomy community in the late 1990s, no one is developing a comparable replacement instrument operating in the optical or ultraviolet wavelengths of light. For that matter, no such instrument has even been proposed.
“Astronomy and Astrophysics in the New Millennium,” a report published in 2001 and sometimes called the decadal survey — and written by some of the most important astronomers in the world — outlined the priorities of the community for the period 2011-2020. Those recommendations bluntly rejected any plans to launch an optical or ultraviolet instrument to replace Hubble.
“The committee has not recommended any new moderate or major missions for space-based … optical astronomy for (the 2010s),” the report said.
The committee, which was convened by the National Academy of Sciences, also put aside any plans to build a replacement ultraviolet space telescope, a wavelength which, according to the report, “is impossible to observe … from the ground.”
Instead, the committee — as well as several other astronomical panels at the time — recommended Hubble’s replacement be an infrared telescope.
“The committee recommends a large infrared-optimized observatory as the highest priority post-(Hubble)-class mission for NASA,” the report said.
Optical astronomy, in turn, would be left to new and large ground-based telescopes using adaptive optics — a technology designed to compensate for the constant fluctuations of the atmosphere.
Thus, even though NASA officials and astronomers often claim the James Webb Space Telescope — once called the Next Generation Space Telescope — is meant to replace Hubble, such statements are not true. The Webb is not an optical instrument. It will not match Hubble’s resolution and it is being designed to operate almost entirely in infrared wavelengths, as recommended by those earlier panels.
Nor can ground-based observatories replace Hubble, as suggested by the decadal survey. Some astronomers like to tout the ability of adaptive optics to compensate for the atmosphere’s fuzziness, but such technology works only in the near-infrared range and can cover only a small percentage of the sky.
As noted in the final report of the 2004 national academies panel on Hubble’s status, “Ground-based adaptive optics systems will not achieve the Hubble’s high degree of image stability or angular resolution at visible wavelengths for the foreseeable future.”
In a May 2004 interview, Steven Beckwith, director of the Space Telescope Science Institute in Baltimore — which operates Hubble — explained the background behind the decision to abandon optical space astronomy in the post-Hubble period.
“You have to prioritize. (Hubble) was up there, it was going to be supported for at least another decade,” Beckwith said. “What (the decadal survey) wanted to do was to push (Webb, making it) the key number one priority.”
The result of these decisions is once Hubble is de-orbited, around 2013, the human race no longer will enjoy a clear view of the heavens. Humanity would become like a near-sighted person who has lost his glasses.
Faced with this impending deadline, the astronomy community faces several options — assuming Griffin buys five more years for the Hubble by approving a shuttle servicing mission.
One is NASA could delay the robot de-orbiting mission and instead commission an additional shuttle mission to Hubble near the end of 2010, just prior to the shuttle’s retirement. A committee of scientists actually proposed such an idea shortly after the shuttle Columbia accident on Feb. 1, 2003.
Headed by astrophysicist John Bahcall of Princeton University’s Institute for Advanced Study, the committee recommended in August 2003 that in addition to the already planned shuttle mission, NASA should consider an additional flight to extend Hubble’s life past 2011.
“The committee prefers a shuttle mission for this purpose, because the same mission will also improve the performance of (Hubble) before it is brought down to Earth.”
Unfortunately, former NASA administrator Sean O’Keefe rejected the proposal and shortly thereafter decided to cancel all shuttle missions to Hubble.
So even if the committee’s recommendation is resuscitated, it remains a temporary solution, because a second shuttle mission could realistically extend Hubble’s life by perhaps five years — the average life expectancy of Hubble’s gyroscopes — or until around 2016.
That date assumes nothing else will go wrong in the interim, a risky possibility, considering Hubble already has completed its original 15-year mission. By 2016, it will have been in orbit for a more than a quarter-century.
The only real long-term solution for maintaining humanity’s ability to observe the heavens with comparable clarity is to begin the challenging work of replacing Hubble.
A replacement orbiting telescope need not be another costly NASA project, as Hubble was, however. Many universities today run small programs to design and launch student-built Earth-observation mini-satellites. Such programs, teaming amateur and professional astronomers, and involving the private sector, could produce a plethora of low-cost space telescopes able to perform significant research.
Or, the American public could decide the need for a Hubble-quality instrument is so great that Congress must fund a successor. If so, the federal government must begin work almost immediately, because such projects usually take between 10 and 20 years from conception to launch, and Hubble is unlikely to last that long, no matter what NASA does.
In either case, the outcry in the past year to keep Hubble flying has illuminated a reality that too many seem unwilling to face: Before Hubble, the human race was blind to the heavens; after Hubble, few would want to return to that state.
The time perhaps has come to confront that reality.
Robert Zimmerman is an independent space historian and the author of “Genesis: the Story of Apollo 8. His most recent book, “Leaving Earth: Space Stations, Rival Superpowers, and the Quest for Interplanetary Travel,” was awarded the Eugene M. Emme Award by the American Astronautical Society for the best popular space history in 2003.