If all goes well, the Hubble Space Telescope should once again peer deep into the universe this weekend.
That's the word from the National Aeronautics and Space Administration. For three weeks, the agency has been struggling to reactivate the orbiting observatory's main science instruments. In late September, an on-board computer balked. It was responsible for making sure the instruments are properly set up to perform observations, and also relays the data to other systems that store and transmit the data back to earth. Then, two weeks ago, as engineers shifted to an on-board backup, unexpected additional glitches brought the restart process to a halt. They appeared unrelated to the original computer problem, NASA officials say.
On Thursday, NASA officials decided it was safe to resume reactivating the back-up computer system that governs the main instruments.
"There does not appear to have been any permanent damage" to the system running the main science packages, and the orbiting observatory's main housekeeping systems were untouched by the problem, says Art Whipple, who heads the Hubble Management Office at NASA's Goddard Space Flight Center in Greenbelt, Md.
The backup science management system is now "up and running," he says. If it continues to work well, he adds, science operations with an instrument called the Wide Field Planetary Camera 2 should resume on Saturday. Two other sophisticated cameras should be back online soon as well, he adds.
That's good news for astronomers, who have used the venerable space telescope as a portal on the early universe, a window on new solar systems in the Milky Way, and as a tool for reducing the uncertainty in the age of the universe. Indeed, through its stunning images of planets, galaxies, gas clouds, and other celestial features, Hubble has become one of the US space program's most powerful public relations tools.
Officials are still working through the implications of the outage for a shuttle mission aimed at installing one last set of upgrades and making some additional repairs to the telescope. That mission was originally scheduled for launch Oct. 10. It's now tentatively set for next February.
Yet even during these past three weeks of nail-biting, the observatory has continued to perform like a champ for some astronomers.
For instance, Douglas Gies, an astronomer at Georgia State University in Atlanta, runs a project aimed at helping figure out how very massive stars in the galaxy – stars some 30 to 60 times more massive than the sun – form. His team uses the observatory's fine-guidance system, essentially three small optical sensors that lock on to distant stars as a way to keep the telescope properly aimed at its primary target.
The team's aim is to use the guidance system to identify as many binary star systems as it can, particularly those where one star is a cosmic behemoth. Hubble's guidance sensors can spot two-star systems that are too faint for ground-based telescopes to pick out, or too distant for them to tell if an object is one star or two tightly spaced ones. The hope is that such binary systems will yield clues about how the largest stars form – and how they get ejected from the clusters of siblings within which they formed.
Typically, Mr. Gies explains, he gets some of Hubble's down time for his observations, taken as the observatory is shifting between larger observing programs or is waiting for its next major target to come into view. For his group, the past three weeks has been a boon, since the fine-guidance system was unaffected by the problems.
"When these electronics problems occurred, the directors very graciously asked us if indeed we might have some more objects to fill in the program," Gies says. "We're getting some superb results coming in, so we're really looking forward to delving into this data."