Popular Hubble camera has quit
The newest and most heavily used camera on the Hubble Space Telescope shut down over the weekend and appears to be permanently damaged, NASA said Monday.
Though other cameras on Hubble remain operative, the Advanced Camera for Surveys, which is used to peer back to the earliest and most remote galaxies in the universe, appears to be irreparable and will have to be replaced on the next Hubble servicing mission in September 2008.
The camera, installed in 2002, had a five-year designed lifetime, “but it is disappointing that it didn’t last longer,” said Matt Mountain, director of the Space Telescope Science Institute, which operates the telescope. “I guess our warranty ran out on us.”
The camera suffered a breakdown in June and engineers activated its backup electronic circuitry. Apparently, a fuse in the backup short-circuited on Saturday, disabling the device.
The camera was by far the most popular instrument on Hubble, which was launched in 1990. An estimated two-thirds of all proposals for Hubble studies involved its use. Its wide field of view made it useful in the search for very distant supernovas, known as Type 1a, which help to explain how the expansion of the universe has been proceeding, said UCLA astronomer Mark R. Morris.
“That is the workhorse camera of the Hubble,” he said.
The recent, highly publicized mapping of dark matter in the universe also was accomplished using the advanced camera.
“This is really a huge problem,” said Caltech astronomer Nick Scoville, who was involved in those mapping studies. “There is a huge amount of stuff that people wanted to do” but that will now be much harder.
Until the new camera is installed, astronomers will improvise.
“We have another camera, called the Wide Field Camera 2, that is slightly older, and not quite as good,” Mountain said. “We’ll be asking researchers, ‘Can you do science with that one if we give you more time?’ ”
Morris has already submitted backup proposals that would use that camera, he said, “but it is not as sensitive and it has degraded a bit with time. That’s an aging camera.”
The damaged camera’s chief advantage was that it had a very wide field of view, allowing it to observe a much greater area of space than other Hubble cameras.
Another Hubble camera, the Near Infrared Camera and Multi-Object Spectrometer, has a field of view that covers about one arcsecond, the apparent size of a dime from about 2.3 miles. The advanced camera covered nearly 20 times that area, Scoville said.
NASA’s new camera, the Wide Field Camera 3, was to have been installed on Hubble in 2005. That service mission was delayed, however, by the 2003 explosion of the shuttle Columbia.
Former NASA Administrator Sean O’Keefe ultimately canceled the servicing mission, citing safety concerns.
In October, however, NASA Administrator Michael D. Griffin reinstated the mission, scheduling it for next year. In addition to installing Wide Field Camera 3, astronauts on that mission also will put in gyroscopes to improve steering, batteries and thermal blankets to insulate sensitive components.
Those repairs will require five full days of space walks -- so much time, said Preston M. Burch, NASA’s Hubble program manager, that there will not be enough time to carry out the extensive repairs required to fix the advanced camera.
“The new camera will be capable of doing a lot of science,” Scoville said, but it can survey only about 60% of the area covered by the advanced camera in a single exposure.
But it will have one advantage: It will provide more power in the infrared regions of the spectrum, Mountain said. “As we are looking deeper and deeper, further back into time, objects are becoming red-shifted into the infrared. We really need to move to infrared to get to the earliest objects in our universe.”