Hubble Pauses its Science Again

The Hubble Space Telescope has been shut down temporarily after one of its gyroscopes sent faulty telemetry readings back to Earth in late May. The venerable space-based observatory, which has been responsible for some of the most remarkable scientific advances of the last three decades, and stunning astrophotography that became a cultural mainstay, is in its thirty-fourth year of operation.

Hubble’s many and varied accomplishments have been achieved despite a plague of technical challenges over the years. Right out of the gate, it launched with blurry vision, due to an improperly polished lens. The problem was fixed with a space shuttle servicing mission in 1993, three years after launch. Four more servicing missions between 1997 and 2009 repaired and upgraded various parts of the spacecraft.

With the retirement of the space shuttle, the space telescope has now been operating for 15 years without servicing.

Pauses in science operations like the current one are common events for Hubble these days, occurring several times a year in recent times. Hubble’s gyroscopes are the usual culprit.

In fact, a faulty gyroscope previously caused a shutdown barely a month ago, in April 2024, and did the same back in November 2023. In every case, NASA was able to get the space telescope back up and running in short order.

That doesn’t mean there is no cause for concern. Gyroscopes help the telescope orient itself in space, keeping it stable to point at astronomical targets in the distant universe. The last servicing mission in 2009 left the telescope with six operational gyroscopes, but it has been running on three since 2018.

Hubble needs all three to operate at full capacity.

The end of a Hubble gyro reveals the hair-thin wires known as flex leads. They carry data and electricity inside the gyro, and their corrosion has caused gyroscope failures in the past. NASA

But having two wouldn’t necessarily be the end of the mission. It would reduce the area of the sky Hubble can observe, and slow down science operations.

Regardless of the outcome of the current troubles, NASA appears confident that this is not the end of the line, stating in a press release on May 31:

“NASA anticipates Hubble will continue making discoveries throughout this decade and possibly into the next, working with other observatories, such as the agency’s James Webb Space Telescope for the benefit of humanity.”

It doesn’t appear that that will be the last word on the subject, however. A press conference has been called for 4PM EDT on June 4, where NASA’s Director of the Astrophysics Division, Mark Clampin, and Hubble’s project Manager, Patrick Crouse, are expected to give an update on Hubble’s condition.

In the event that Hubble is reduced to two working gyroscopes, NASA recently indicated that it would likely put one of them into safe mode, relying on just one gyroscope and keeping the last in good working order for the future.

With just one gyroscope in operation, magnetometers, sun sensors, and star trackers will need to make up for the work that the other gyroscopes used to do. This takes more time, and would reduce Hubble’s working capacity by 20-25%. Hubble would no longer be able to look at objects closer to Earth than Mars, it would be less capable of catching transient events at a moment’s notice, and it would have to pause observations during parts of its orbit when the Moon and Earth get in the way of its star trackers.

But it would keep the mission alive longer, which is good news for astronomers and astronomy fans everywhere. There is even hope for a future Hubble repair mission, an idea proposed by Jared Isaacman, a private astronaut who will command the upcoming Polaris Dawn mission aboard SpaceX’s Dragon capsule. Currently, Dragon is incapable of docking with Hubble, leaving the idea firmly in the speculative stage for the moment.

As for more immediate plans, we’ll have to see what NASA has to say. Stay tuned for the press conference at 4PM June 4.