The venerable Hubble Space Telescope is running out of gyroscopes, and when there are none left, the instrument will stop doing meaningful science.
To preserve the telescope, which has been in space for nearly three and a half decades, NASA announced Tuesday that it will scale back Hubble’s operations to a single gyroscope. This will limit some science operations and it will take more time to point the telescope at new objects and fix them.
But in a conference call with space reporters, Hubble officials stressed that the beloved science instrument isn’t going anywhere anytime soon.
«I personally don’t see this as a huge limitation on the ability to do science,» said Mark Clampin, director of the astrophysics division at NASA headquarters in Washington, DC.
From six to one
The Hubble Telescope was launched aboard a NASA spacecraft in 1990, and since then the space agency has flown five servicing missions to repair and upgrade the complex instrument. To this day, it offers humanity the best view of the universe in the visible light spectrum.
The last of these servicing missions, operated by the space shuttle Atlantis In 2009, made numerous upgrades, including replacing all six gyroscopes that help orient and point the telescope. However, in the 15 years since then, three of the six gyroscopes have failed. In the last six months, another one, «gyro 3», is increasingly returning incorrect data. Because of this, Hubble repeatedly went into safe mode, halting scientific operations.
As a result, the space agency only has two fully functional gyroscopes. One of them, gyro 4, worked a total of 142,000 hours. The second, gyro 6, has accumulated 90,000 hours. NASA’s plan now is to operate the telescope on one gyroscope and keep the other as a «backup» option.
NASA has said that single-gyro operation is feasible, with relatively modest implications for observing capabilities. It will be less effective, it will require more time to show. This will result in a loss of about 12 percent of observation time. The telescope will also not be able to observe objects closer than Mars, including Venus and the Moon.
However, by taking this step now, the space agency believes it can extend Hubble’s operational life by another decade. The telescope’s project manager, Patrick Crouse, said there is a 70 percent chance that Hubble can maintain science operations using a single gyro until 2035.
«We don’t see Hubble running out,» he said Tuesday.
From a scientific point of view, it is important that Hubble continues to operate. Now that the powerful James Webb Space Telescope is operational, these two instruments are a formidable duo. With Hubble observing in visible light and Webb in infrared, astronomers can glean valuable new insights into the nature of the universe.
Another servicing mission? No Thanks
In addition to outdated scientific instruments and a dwindling number of gyroscopes, NASA also faces some other challenges related to the lifetime of the instrument. The telescope usually operated at an altitude between 615 km and 530 km above the Earth’s surface. However, the telescope is likely to fall below 500 km this year. At lower altitudes, some of the telescope’s observations are affected by other satellites in low Earth orbit.
Clampin said Tuesday that telescope operators do not anticipate Hubble re-entering Earth’s atmosphere before the mid-2030s. This, combined with the gyroscope limitation, would seem to set a hard limit on Hubble’s maximum remaining lifetime.
However, in 2022, Jared Isaacman, the billionaire who flew the first fully commercial human mission to orbit aboard Crew Dragon, approached NASA about performing a servicing mission for the Hubble Space Telescope. He proposed funding a major part of the mission that would, at least, re-size the Hubble Space Telescope by at least 50 km.
After NASA and SpaceX conducted a feasibility study late that year, it was recommended that the space agency continue to explore the possibility of a commercial mission. At the very least, he could safely repower the telescope, but there were also options that included attaching star trackers and external gyroscopes to compensate for the telescope’s weak pointing system.
But NASA decided not to pursue that option.
«Our position at this time is that, after exploring the current commercial options, we will not immediately proceed with another increase,» Clampin said on Tuesday.
Asked about the study, which NASA declined to release for proprietary reasons, Clampin said, «It was a feasibility study that helped us understand some of the issues and challenges we might face,» he said. «There were options like being able to improve it by adding a gyroscope to the outside of the telescope, but those were really just imaginary concepts.»
NASA apparently decided it was safer to let Hubble age on its own than to risk private hands touching the hallowed telescope. We’ll see how it goes.