Astronomers foresee long future for Hubble
SEATTLE — Despite a recent problem with one of its instruments, managers of NASA’s Hubble Space Telescope are confident that the mission can continue to operate well into the next decade.
NASA announced Jan. 8 that the Wide Field Camera 3 (WFC3) instrument on Hubble suffered a hardware problem that forced it to suspend operations. Hubble observations using other instruments will continue, the agency said, while engineers diagnose the problem.
The instrument remains offline, but astronomers and others involved with Hubble at the 233rd Meeting of the American Astronomical Society here said they’re optimistic that the instrument can resume operations in the near future. Potential solutions to the problem range from a simple reset of the instrument to switching to a redundant set of electronics.
“Have no fear, that will be up again soon,” said Tom Brown, Hubble mission manager at the Space Telescope Science Institute, during a session about the future of the telescope at the conference Jan. 10. “Some of the most recent discussions I’ve been having seem to point to not needing to go to those redundant electronics” to fix WFC3.
The rest of the telescope is in good condition. Engineering analyses Brown presented at the conference showed that the instruments and major subsystems have a high probability — in excess of 80 percent — of remaining operational through 2025. “We expect Hubble to be scientifically productive far into the next decade,” he said.
Those subsystems include gyros, the failure of one of which triggered a safe mode in October that kept the telescope offline for three weeks. Hubble currently has three working gyros, and has software developed to shift to one-gyro mode when one the remaining three fails.
Brown said there’s little difference in telescope performance when using one gyro versus two, and shifting to one-gyro mode, using one and then the other, will maximize the life of the telescope. “If we use the last two remaining gyros consecutively,” he said, “their projected lifetimes are all the way through the end of the next decade.”
One-gyro operations do impose some limitations on Hubble operations, including limitations on the ability to track fast-moving solar system objects. “It will scientifically give very similar performance to what we get today” in terms of pointing stability, he said.
Hubble, launched in 1990 and last serviced in 2009, remains in high demand by astronomers. The oversubscription rate, the ratio of time requested on Hubble versus the time available for observations, has been greater than five in recent years, Brown said. Currently about one published astronomy research paper in six is based on either recent Hubble observations or archival data.
“The demand for HST is not slowing down,” said Julianne Dalcanton, a professor of astronomy at the University of Washington, during the conference session. “The oversubscription rate is still high.”
How astronomers use Hubble may change over time, though. Dalcanton said she expected astronomers currently using the telescope for infrared observations to shift to the James Webb Space Telescope and Wide Field Infrared Survey Telescope, both optimized for infrared observations, when they are launched in the 2020s. That will free up Hubble for more ultraviolet and visible light observations ill-suited for the newer telescopes.
At the same time, new large groundbased telescopes, with mirrors up to 40 meters in diameter, that will begin operations in the 2020s will provide capabilities at visible wavelengths exceeding that of Hubble in some respects, such as detecting faint objects. Hubble, she suggested, could shift to doing more survey work while continuing to support smaller research programs.
“In that landscape, HST’s role for optical imaging is not going to be depth,” she said. “I think where it’s really going to play a role, and what Hubble will continue to offer uniquely from space, is its resolution, its precision and its stability.”