The venerable Hubble Space Telescope is running out of gyroscopes, and when there are none left, the instrument will cease to perform meaningful science.
To preserve the telescope, which has operated in space for nearly three and a half decades, NASA announced Tuesday that it will scale back Hubble’s operations to run on a single gyroscope. This will limit some science operations and it will take more time to point the telescope at new objects and lock onto them.
But in a conference call with space reporters, Hubble officials emphasized that the beloved science instrument isn’t going anywhere anytime soon.
“I personally don’t see this as a major limitation in his 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 NASA’s space shuttle in 1990, and since then, the space agency has flown five servicing missions to repair and upgrade the complex instrument. To date, it provides humanity with the best view of the Universe in the visible light range of the spectrum.
The last of these service missions, flown by spacecraft Atlantis in 2009, it underwent numerous upgrades, including replacing all six gyroscopes that help orient and steer the telescope. However, in the 15 years since then, three of the six gyroscopes have failed. In the past six months, another, gyro 3, has been returning more and more erroneous data. This has caused Hubble to go into safe mode several times, halting science operations.
As a result, the space agency has only two fully operational gyroscopes. One of them, lap 4, has run a total of 142,000 hours. Another, lap 6, has accumulated 90,000 hours. NASA’s plan is to now operate the telescope on a single gyroscope, keeping the second as a “backup” option.
NASA said that operation on a single gyroscope is feasible, with relatively modest implications for observational capabilities. It will be less efficient, requiring 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 for another decade. The telescope’s project manager, Patrick Crouse, said there is a 70 percent chance that Hubble will be able to sustain science operations using a single gyroscope until 2035.
“We don’t see Hubble as on its last legs,” 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, the two instruments make a stunning duo. With Hubble observing in visible light and Webb in infrared, astronomers can glean valuable new insights into the nature of the Universe.
Another service mission? No thanks
In addition to aging science instruments and a declining number of gyroscopes, NASA also faces several other challenges related to instrument longevity. The telescope has typically operated at an altitude between 615 km and 530 km above the Earth’s surface. However, the telescope is likely to drop below 500 km sometime this year. At lower altitudes, some of the telescope’s observations are being 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. That, combined with the gyroscope’s limit, appears to put a steady limit on the maximum remaining lifetime of the spacecraft. Hubble.
However, in 2022, Jared Isaacman, a billionaire who flew the first fully commercial human mission to orbit aboard Crew Dragon, approached NASA about performing a servicing mission on the Hubble Space Telescope. He proposed funding most of the mission, which would, at the very least, have boosted the Hubble Space Telescope by at least 50 km.
After NASA and SpaceX conducted a feasibility study later that year, it was recommended that the space agency continue to investigate the possibility of a commercial mission. At a minimum, it could safely repower the telescope, but it also had options that included attaching star trackers and external gyroscopes to compensate for the telescope’s failing pointing system.
But NASA decided not to pursue the option.
“Our position now is that, after exploring the current trading capabilities, we will not pursue a re-strengthening immediately,” Clampin said on Tuesday.
Asked about the study, which NASA has declined to release for proprietary reasons, Clampin said: “It was a feasibility study to help us understand some of the issues and challenges that we might have to face,” he said. . “There were options such as being able to make improvements by adding gyros to the outside of the telescope, but those were really just imaginary concepts.”
NASA has apparently decided it’s safer to let Hubble age on its own than to take a chance on private hands touching the hallowed telescope. We’re ready to see how it goes.