Kaput: Hubble's main camera stops working.

The sharpest, most sensitive camera on the aging Hubble Space Telescope has stopped working, and its most impressive capability can't be revived, NASA announced this week

The problem began on Jan. 27, when the orbiting observatory abruptly went into "safe mode," turning off its nonessential detectors, including several in the telescope's showcase instrument, the Advanced Camera for Surveys (ACS). An investigation revealed a short in circuitry powering the camera.

The glitch doomed the ACS' two exquisitely sensitive visible-light detectors, which since last June had been powered by a backup electronics system after a power-supply malfunction (SN: 7/8/06, p. 19). That original problem didn't affect the camera's most limited detector, which studies only ultraviolet emissions from bright objects such as hot stars. Although the new problem shut down that detector, engineers hope that by switching back to the primary power supply toward the end of February, they'll reactivate the instrument.

Hubble's three other instruments--a less sensitive visible-light camera, a near-infrared camera, and the telescope's fine-guidance sensors, which call be used to track the motion of stars--are expected to resume operation by early February, according to Preston Burch, Hubble's associate director and program manager at NASA's Goddard Space Flight Center in Greenbelt, Md. He detailed the observatory's status during a telephone briefing on Jan. 29.

Observation using the ACS has accounted for two-thirds of studies with the observatory, notes Burch. Installed by astronauts in March 2002, the camera has taken the deepest portrait ever of the universe and revealed planet-spawning disks of gas and dust around nearby stars.

"The seemingly permanent loss of the ACS is a blow to the astronomical community," says astronomer Lynne Hillenbrand of the California Institute of Technology in Pasadena, Calif. "It should be recognized, however, that [Hubble] is an aging facility very close to its nominal mission lifetime, which expires in 2010, and we might expect continued hardware failures."

Some planned ACS observations could be carried out instead by longer exposures with the wide-field camera, Burch notes. The agency says that it has plenty of studies to keep Hubble's three remaining instruments busy until shuttle astronauts arrive for along-delayed servicing mission, now scheduled for September 2008 (SN: 11/4/06, p. 294).

Then, the crew will install a sensitive ultraviolet spectrograph and a new infrared camera and attempt to repair a spectrograph that has stopped working. Repairs to the ACS would be too risky and labor intensive, says Burch.