The Hubble Space Telescope's automatic shutdown will indefinitely delay more than 100 observations, affecting the work of about 70 astronomers who had scheduled telescope time between now and mid-DecemberThe Hubble Space Telescope's automatic shutdown will indefinitely delay more than 100 observations, affecting the work of about 70 astronomers who had scheduled telescope time between now and mid-December.
The Space Telescope Science Institute (STSI), which conducts Hubble's science mission, schedules about 30 observations each week, said Ray Villard, an institute spokesman.
Although those astronomers will need to have their observing time rescheduled, Hubble should be as good as new after space shuttle astronauts service the telescope early next month, Villard said.
"Every effort will be made to fold these observations back in to the observing schedule once the shuttle astronauts make the repairs," Villard said.
The rescheduling is complicated by the fact that the postponed observations must be fit into an already-packed schedule, all should be done within a year, he said.
The telescope entered safe mode Saturday, when one of the spacecraft's three remaining gyroscopes stopped operating. Hubble needs three of the instruments to accurately aim at celestial targets. With only two, the telescope automatically goes into a safe mode. It quits its observing duties and orients its solar panels to maximize power production and keep its batteries fully charged.
Many astronomers who were slated to use the telescope in the coming weeks said they are disappointed about their loss of valuable time, but not heartbroken.
Melissa McGrath is an astronomer at the STSI who uses Hubble to study several of Jupiter's moons. Her team conducted observations earlier this year that resulted in the discovery of a glowing aurora around the jovian moon Ganymede. McGrath said she had hoped that follow-up observations this week would add to the information she had already collected.
"We're disappointed, but in fact these are follow-up observations, they weren't crucial," McGrath said.
This Hubble image shows Ganymede's auroral glow. The graph of the moon's globe has been superimposed to give perspective. Credit: NASA and Space Telescope Science Institute.
The failure is not totally unexpected. The telescope was scheduled for servicing, and astronomers have known that a breakdown like this could occur any time, McGrath said. "We're just happy that we didn't lose more observing time. As it is, we'll lose three weeks of data, which means we just get a rest for a while."
Despite the telescope's trouble, observing from Hubble is still much more reliable than doing observations from the ground, said Richard French, an astronomer at Wellesley College who has been using Hubble to study Saturn's rings and moons.
Cloud cover and equipment problems on the ground often interfere with astronomers using ground-based telescopes, French said.
"I do lots of time-critical observing from the ground and if I get data half of the time I go I'm happy," he said.
French leads a team that uses Hubble to conduct a long-term study on Saturn's rings as their tilt with respect to Earth changes. The project began when the rings could be seen from Earth edge on, and will continue until the plane of the rings opens most toward Earth, shortly before the Cassini spacecraft arrives at Saturn in 2004.
Saturn as seen with the Hubble Space Telescope. Credit: Richard French, NASA and Space Telescope Science Institute.
The team is also studying Prometheus and Pandora, two of Saturn's moons that cannot be seen with even the best ground-based telescopes. Although every observation adds important information about the rings and moons, French said his team gets three to four observations a year, so over the long term, the Hubble shutdown is not crippling.
"I just think that we have to be realistic about what it takes to run a complex observatory. Three weeks of downtime is regrettable, but considering the complexity of the thing, I think they're doing wonderful science," he said.
One scientist who is not guaranteed that his telescope time will be rescheduled is Patrick Seitzer, an astronomer at the University of Michigan who leads an effort to snap pictures of 75 distant galaxies that have never been resolved in telescope images.
This "snapshot survey" uses Hubble during orbits that would otherwise go to waste because no other project is using the telescope during that particular orbit.
Rescheduling several important projects into the docket during the coming year may mean there will be less unused time to offer Seitzer's snapshot survey. Still, in the few months since it began, Hubble has already imaged about 30 of the 75 target galaxies.
"It's going much quicker than we ever imagined," Seitzer said.
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