With a robotic mission to extend the life of the Hubble Space Telescope a good bet for late 2007 or 2008, NASA is also quietly considering launching one of the replacement instruments on a free-flying telescope that will incorporate advanced optics and spy-satellite technologies.
The robotic rescue likely could replace Hubble's dying batteries and gyroscope and perhaps install a new wide-field camera. Also on the initial list of upgrades was the Cosmic Origins Spectrograph (COS), but it may be beyond the reach of robotic systems. The $65 million instrument, which would gather data on early galactic evolution, requires complicated wiring best connected by human hands. So when NASA announced in January that it would not send humans to service Hubble again, the future of COS looked grim.
But NASA chief scientist John Grunsfeld says one option is to launch COS aboard a spacecraft that makes use of the latest advances in mirror technology, perhaps as early as 2009. Adaptive optics, now used on ground-based mirrors to counter thermal, gravitational, and atmospheric variations, could be used to lower both the cost and weight of a new space-based mirror and forge the way for future missions.
One official involved in the discussion envisions a 2-meter mirror nearly as capable as Hubble's but weighing only 200 kilograms, a fraction of the weight of Hubble's mirror. The spacecraft would weigh 2.5 tons, or one-fifth the weight of Hubble. The cost would be $200 million to $300 million, plus up to $100 million to launch the telescope into a high orbit aboard a Delta 2 expendable rocket. Overall, the capabilities of such a telescope would be much less than those of Hubble. "It's Hubble Lite," the official says, adding that defense officials are eager to test advanced optics for use in their spy satellites.
"It's potentially doable, and it would be nice to take steps in that direction," says J. Roger P. Angel, an astronomer at the University of Arizona in Tucson who has worked for decades on adaptive optics. But he warns that new technology usually takes more time and money than expected and that the nearly 1-ton size of COS poses a challenge.
For now, however, Grunsfeld says NASA's focus must be on the robotic mission to Hubble. Before it even hears from a National Academy of Sciences panel examining Hubble's future, NASA plans to ask industry next month to propose ways to conduct the effort and award a contract by September. "It is clear to us that if we don't get moving, it's not going to happen," says Grunsfeld.