The Hubble Space Telescope is suffering the kinds of aches and pains that can come with being old, and NASA officials say they’re shifting into a new way of pointing the telescope in order to work around a piece of hardware that’s become intolerably glitchy.
Officials also announced that, for now, they’ve decided not to pursue a plan put forward by a wealthy private astronaut who wanted to go to Hubble in a SpaceX capsule, in a mission aimed at extending the telescope’s lifespan by boosting it up into a higher orbit and perhaps even adding new technology to enhance its operations.
“Even without that reboost, we still expect to continue producing science through the rest of this decade and into the next,” Mark Clampin, director of the astrophysics division in NASA’s science mission directorate, told reporters in a teleconference on Tuesday.
Because of atmospheric drag, the bus-sized telescope is slowly drifting down towards Earth. If nothing is eventually done to raise it up, it will likely plunge down into the atmosphere and mostly burn up in the mid-2030’s.
That’s one reason why NASA was so interested when Jared Isaacman, who has previously gone to orbit in a SpaceX capsule, suggested mounting a mission to Hubble as part of a series of technology demonstration spaceflights he has planned.
NASA and SpaceX jointly worked on a feasibility study to see what might be possible for Hubble. The telescope has been in orbit since 1990 and was last repaired 15 years ago, by astronauts who went up in NASA’s space shuttles, which are now museum exhibits.
NASA’s Clampin told reporters that “after exploring the current commercial capabilities, we are not going to pursue a reboost right now.”
He said the assessment of Isaacman’s proposal raised a number of considerations, including potential risks such as “premature loss of science” if Hubble accidentally got damaged.
NASA officials stressed that Hubble’s instruments are healthy and the telescope remains incredibly productive.
“We do not see Hubble as being on its last legs,” said Patrick Crouse, project manager for the Hubble Space Telescope at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We do think it's a very capable observatory and poised to do exciting things.”
But it will have to do those exciting things with a new way of operating the system it uses for pointing at celestial objects.
That’s because officials have abandoned their efforts to use a glitchy gyroscope that has repeatedly forced the telescope to suspend science and go into “safe” mode in recent months.
Hubble’s pointing system is so precise, NASA says it is the equivalent of being able to keep a laser shining on a dime over 200 miles away for however long Hubble takes a picture – up to 24 hours. This system has long relied on using three gyroscopes at a time.
Now, though, to avoid having to use the sketchy gyro, NASA says Hubble will shift into a one-gyroscope mode of operation, a contingency plan that’s been around for years.
“After completing a series of tests and carefully considering our options, we have made the decision that we will transition Hubble to operate using only one of its three remaining gyros,” Clampin said. “Operationally, we believe this is our best approach to support Hubble science through this decade and into the next.”
Using only one healthy gyroscope, and keeping one in reserve as a backup, will let the telescope continue to return gorgeous images of the universe, with some limitations. Hubble will be less efficient, for example, and it won’t be able to track moving objects that are close to Earth, within the orbit of Mars.
But Clampin said that “most of the observations it takes will be completely unaffected by this change.”
Astronomers still clamor to use Hubble, with proposals for what to observe far exceeding the available telescope time.
The launch of the James Webb Space Telescope in 2021 did not render Hubble obsolete, as the two telescopes capture different kinds of light.
Eventually, NASA will have to decide what to do about Hubble, given that some of its large components would survive re-entering the Earth’s atmosphere. The space agency has long considered sending up some kind of mission that would control its descent and ensure that any Hubble rubble would safely fall into an ocean.
Adding such a propulsion unit would mean that NASA could also boost Hubble’s orbit, enabling it to live longer and take advantage of whatever instruments continued to work. But NASA’s Clampin suggested that there is time to consider options.
“Our latest prediction is that the earliest Hubble would re-enter the Earth's atmosphere is the mid-2030s,” he said. “So we are not going to be seeing it come down in the next couple of years.”
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