The main camera aboard NASA's orbiting Hubble Space Telescope has conked out, and its loss could delay or cancel much of the work currently proposed for the aging scope. Hubble will continue to peer into the heavens with its three other instruments, however.
On 27 January, Hubble's Advanced Camera for Surveys (ACS) switched itself into a protective "safe mode" after a short in its electronics. NASA engineers believe the fault has killed the camera's ability to see deep and wide. "It's really a blow to Hubble science; there's no way around that fact," says Holland Ford, an astronomer at Johns Hopkins University in Baltimore, Maryland, and principal investigator for ACS. He adds that of the roughly 800 current proposals for using Hubble, two-thirds involved the ACS.
Installed in 2002, the ACS provided the widest field of view and highest sensitivity at optical wavelengths of any of Hubble's instruments. It had been the workhorse for broad surveys that traced the evolution of the galaxies, probed the structure of the cosmos, and hunted for supernovae to measure the accelerating expansion of the universe. NASA engineers had already switched the instrument to its back-up electronics after the primary circuits failed last June. The camera was designed to last 5 years and had already achieved its original objectives, Ford says.
Engineers will try to determine if the camera can be repaired when the Space Shuttle rendezvous with Hubble in 2008. But that's a long shot, says David Leckrone, senior project scientist for Hubble at NASA's Goddard Space Flight Center in Greenbelt, Maryland. A fix would likely require opening up ACS and even dismantling other equipment, Leckrone says, and that's "just not going to happen."
During that visit, astronauts will also install a new camera that can see in infrared and ultraviolet wavelengths and will be able to perform some of ACS's work. Until then, some projects will stop, says Adam Riess, an astronomer at Johns Hopkins and the nearby Space Telescope Science Institute (STSci) who uses supernovae to study the expansion of the universe. "I don't think we'll make a lot of progress until the servicing mission," Riess says. "It will be frustrating to wait."
Hubble won't stand idle, however. After the ACS's primary electronics failed last year, officials at STSci issued a call for proposals for surveys that rely on Hubble's other instruments. In December, they picked 6 of 34 submissions to form a back-up schedule, Leckrone says. Officials have also given researchers an extra two weeks to modify their latest proposals, which were due last week. So from now until its new camera arrives, Hubble will be switching to plan B.
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