Hubble's main camera stops working
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: January 29, 2007
A state-of-the-art camera aboard the Hubble Space Telescope has been knocked out of action by an electrical glitch, curtailing the flow of high-resolution imagery from the aging observatory until new instruments can be installed during a final shuttle servicing mission in 2008.
During that flight, a new camera and spectrograph will be installed, along with six new batteries and a suite of stabilizing gyroscopes that should extend Hubble's scientific life until at least 2013 and possibly longer.
But with the apparent demise of the Advanced Camera for Surveys, installed during the most recent shuttle visit in March 2002, the telescope's most spectacular visible-light images of deep space splendors will be on hold, a disappointment to astronomers around the world.
The camera was engineered to last at lest five years and "we always hope we will meet not only the design lifetime but we'll also get a bonus and that these instruments will live beyond that," Preston Burch, Hubble program manager at NASA's Goddard Space Flight Center in Greenbelt, Md., told reporters today. "So obviously we're disappointed."
Given the complexity of the five-spacewalk servicing mission planned for 2008, NASA is unlikely to add any additional repair work to the astronauts' flight plan.
"If you look at Servicing Mission 4 right now, it's very heavily subscribed," Burch said. "So something would need to come off the repair list (to address the ACS problem) and our preliminary discussions with knowledgeable scientists ... have indicated that's probably not a desirable thing to want to do.
"I wouldn't want to say it's totally impossible if we wanted to put this on a crash basis, but it would require considerable additional effort, time and money to do that. ... At first blush, this doesn't look very attractive."
But Burch said installation of the new Wide Field Camera 3 and the planned repair of a spectrographic instrument already aboard the space telescope will replace and extend the lost capability of the Advanced Camera for Surveys.
In the meantime, engineers are conducting a detailed technical review to make sure the electrical problems that hobbled ACS will not affect the Wide Field Camera 3 or the new Cosmic Origins Spectrograph scheduled for installation in 2008.
For redundancy, the ACS was built with dual power and data systems. On June 30, 2006, an electrical glitch knocked one electrical system, known as Side A, out of action.
The B channel failed Jan. 27, apparently because of an unrelated electrical issue. Pressure sensors detected a presumed puff of smoke when the electrical malfunction occurred and while engineers do not believe the telescope's optical system was contaminated, they do not know exactly what went wrong.
"It's sort of like 'CSI: Greenbelt,'" Burch said in a telephone interview. "We may never know."
Engineers may re-power the A side electronics to permit limited operations with one ACS sensor but this so-called "solar blind" channel is used primarily for low-resolution ultraviolet imaging. Barring a complex orbital repair job, high-resolution visible light pictures will no longer be possible with ACS.
Burch said the B-Side glitch is similar to an electrical problem that earlier affected the Space Telescope Imaging Spectrograph, an instrument shuttle astronauts hope to repair during the 2008 servicing mission.
The similarity in failure modes "is also giving us reason to want to bore into the circuit design and part selection and stuff like that to doubly insure we don't have some kind of latent defect waiting in the wings for COS and WFC-3."
During an earlier review, "we uncovered a lot of workmanship issues ... in the past year and those things have been addressed," Burch said. "It's entirely possible that what just occurred on ACS could very well be a workmanship kind of issue. We don't really know. ... We'll be boring into that very heavily to try to make sure the best we can that the COS and Wide Field 3 are the very best we can make them."
Engineers are hopeful no such problems will be found. With launch now less than two years away, Burch said, "if something like that surfaces, that would be a setback and put a lot of pressure on the program."
Hubble Servicing Mission No. 4 - SM-4 - will be flown aboard the shuttle Atlantis in September 2008. It is the only non-space station mission left on the shuttle manifest, a reflection of the high scientific priority attached to keeping the venerable observatory in operation.
Five back-to-back spacewalks will be required to install six new batteries, six new gyroscopes, the Wide Field Camera 3, the Cosmic Origins Spectrograph and a replacement fine guidance sensor to help the observatory find and track its targets.
The astronauts also will attempt to fix the broken Space Telescope Imaging Spectrograph, a complex task that will require the removal of 111 non-captive screws and the replacement of a power supply circuit board. It is considered the most challenging Hubble repair job since two spacewalking astronauts helped replace a power control unit in 2002.
In addition, Atlantis' crew will install a cooling system to lower the spectrometer's operating temperature, repair degraded thermal insulation and install a fixture that will permit the eventual attachment of a small rocket module to drop it safely out of orbit when it is no longer operational.
The Wide Field Camera 3, installed in place of the current Wide Field Planetary Camera 2, will provide high-resolution optical coverage from the near-infrared region of the spectrum to the ultraviolet.
The Cosmic Origins Spectrograph, sensitive to ultraviolet wavelengths, will take the place of a no-longer-used instrument known as COSTAR that once was used to correct for the spherical aberration of Hubble's primary mirror. All current Hubble instruments are equipped with their own corrective optics
If SM-4 is successful, engineers believe Hubble will remain scientifically productive at least through 2013, an additional five years beyond what could be expected based on the current health of its aging batteries and gyroscopes. With any luck at all, the telescope will still be operating when its replacement, the huge infrared-sensitive James Webb Space Telescope, is launched around 2013.
In the meantime, Hubble's two new science instruments will help the observatory address some of the most fundamental questions in astrophysics and cosmology, including the nature of the so-called dark energy believed to be accelerating the expansion of the universe, and the evolution of galaxies in the wake of the big bang.