The venerable Hubble Space Telescope is running out of gyroscopes, and if there are none left, the instrument will cease to perform meaningful science.
To preserve the telescope, which has been in space for nearly three and a half decades, NASA announced Tuesday that it will reduce Hubble’s operations so that it will operate on just a single gyroscope. This will limit some science operations, and it will take longer to point the telescope at and lock on new objects.
But in a conference call with space reporters, Hubble officials emphasized that the beloved scientific instrument isn’t going anywhere anytime soon.
“I personally don’t see this as a major 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 on NASA’s Space Shuttle in 1990, and since then the space agency has conducted five maintenance missions to repair and upgrade the complex instrument. To this day, it offers humanity the best view of the universe in the visible light range of the spectrum.
The last of these maintenance missions, flown on a space shuttle Atlantis made numerous upgrades in 2009, including the replacement of all six gyroscopes that help orient and aim the telescope. However, in the fifteen years since, three of the six gyroscopes have failed. Over the past six months, another, “gyro 3,” has increasingly returned erroneous data. This has caused Hubble to enter safe mode several times, halting scientific activities.
As a result, the space agency has only two fully functional gyroscopes. One of them, gyro 4, has run a total of 142,000 hours. Another, gyro 6, has 90,000 hours on the odometer. NASA’s plan is to now run the telescope on a single gyroscope and keep the second as a backup option.
NASA said operating on a single gyroscope is feasible, with relatively modest implications for observing capabilities. It will be less efficient and take more time to point. This will result in a loss of approximately 12 percent of the observation time. The telescope will also not be able to observe objects closer than Mars, including Venus and the moon.
By taking this step now, however, 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 will be able to continue science operations using a single gyroscope until 2035.
“We don’t see Hubble on its last legs,” he said Tuesday.
From a scientific point of view, it is important that Hubble continues to function. Now that the powerful James Webb Space Telescope is operational, the two instruments make a great duo. Because Hubble observes in visible light and Webb in infrared, astronomers can gain valuable new insights into the nature of the universe.
Another service mission? no thanks
In addition to aging scientific instruments and a declining number of gyroscopes, NASA also faces a number of other challenges related to instrument life. The telescope has typically operated at altitudes between 615 km and 530 km above the Earth’s surface. However, the telescope will probably get below 500 km sometime this year. At lower altitudes, some of the telescope’s observations are influenced by other satellites in low Earth orbit.
Clampin said Tuesday that telescope operators do not predict Hubble will reenter Earth’s atmosphere before the mid-2030s. That, combined with the gyroscope limit, seems to set a firm limit on Hubble’s maximum remaining lifespan.
However, in 2022, Jared Isaacman, a billionaire who flew the first fully commercial human mission aboard Crew Dragon, approached NASA about conducting a maintenance mission on the Hubble Space Telescope. He proposed funding most of the mission, which would have at least expanded the size of 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, it could safely boost the telescope, but there were also options like attaching star trackers and external gyroscopes to compensate for the telescope’s ailing pointing system.
But NASA decided not to pursue this option.
“Our position at this time is that, having explored current commercial opportunities, we will not immediately pursue a new impetus,” 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 we may face,” he said. “There were options such as the ability to make improvements by adding gyroscopes to the outside of the telescope, but they were really just imaginary concepts.”
NASA has apparently decided that it is safer to let Hubble age alone than to risk private hands touching the sacred telescope. We’ll see how that goes.