NASA has announced some bad news about the Hubble Space
Telescope. The
spacecraft has been orbiting Earth and collecting
information about space since 1990. Now, Hubble''s sharpest camera has died, and there''s no way to bring it back to its full power. Until it broke down, the Advanced Camera for Surveys (ACS) was the most popular instrument on board, accounting for two-thirds of the observations made by the orbiting
telescope. It also captured the deepest picture ever taken of the universe, which reveals disks of gas and dust turning into planets around other stars. The ACS was installed in March 2002.
Trouble struck on Jan. 27, when Hubble suddenly went into "safe mode." This means that it shut off detectors that it didn''t need, including several in the ACS. An investigation showed a glitch in the electrical system that powered the camera. As a result, two sensors on the ACS that detect visible light failed. Since last June, those detectors had been running off backup power after another problem with the
spacecraft''s main power supply. "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. Near the end of February, engineers plan to switch the Hubble camera back to the original power system. They hope the changeover will revive a detector that collects ultraviolet light.
Sometime in early February, three more instruments should come back online—including a less sensitive camera that uses visible light, a camera that detects near-infrared light, and fine-guidance sensors, which track the motions of stars. By collecting light in longer exposures, the Hubble''s wide-field camera might be able to fill in for the ACS in some cases. And NASA points out that it has plenty of projects to keep Hubble''s remaining instruments busy. Astronauts will return to the spacecraft in September 2008 to service and repair the telescope. They''ll install a new infrared camera and a sensitive ultraviolet spectrograph, which measures wavelengths of light. They will also try to fix a spectrograph that has stopped working. Repairs to the ACS itself would be too risky and take too much effort to be worthwhile. As originally planned, Hubble was scheduled to operate until 2010. This date is approaching rapidly, Hillenbrand says. More hardware failures like this one are increasingly likely in the coming years.