Despite gyroscope failure, NASA says Hubble Space Telescope still delivers world-class science – Spaceflight Now

Problems with one of the Hubble Space Telescope’s three remaining gyroscopes, critical for aiming and locking on targets, have led mission managers to switch to a backup control mode that will limit some observations but keep the iconic observatory running well into the 2030s. officials said Tuesday. .

“We still believe that there is a very high reliability and probability that we can operate Hubble very successfully, doing innovative science, for the rest of the 1920s and until 2030,” Patrick Crouse, Hubble project manager, told journalists during an afternoon conference call.

At the same time, Mark Clampin, director of astrophysics at NASA Headquarters, said the agency has ruled out, at least for now, a commercial mission proposal to boost Hubble to a higher altitude using a SpaceX Crew Dragon spacecraft. The flight was suggested by SpaceX and Crew Dragon veteran Jared Isaacman as a way to extend Hubble’s lifespan.

By boosting the telescope to a higher altitude, the subtle “drag” effects in the extreme outer atmosphere, which act to slowly but surely pull the spacecraft back to Earth, could be reduced. Isaacman, a billionaire who chartered the first fully commercial flight to low-Earth orbit in 2021, is in training to lead three more SpaceX “Polaris” missions, including a flight this summer in which he plans to become the first private citizen to fly. occupy the position. an open hatch and float, if not walk, in space.

But project managers said Tuesday that Hubble is not in danger of returning to Earth anytime soon. The latest calculations show that the observatory will remain in orbit until at least 2035, giving time to consider possible options, if necessary, in the future.

“After exploring current commercial capabilities, we will not pursue a reset at this time,” Clampin said. “We greatly appreciated the in-depth analysis conducted by NASA and the (SpaceX-Isaacman) program and our other potential partners, and it certainly gave us better insight into considerations for developing a future commercial restart mission.

The Hubble Space Telescope was launched aboard the Discovery shuttle on April 24, 1990, with a notoriously faulty mirror, the opening chapter in an unlikely story in which spacewalk repair teams transformed a national embarrassment into an international science icon.

Hubble was initially hampered by an error during manufacturing of the 94.5-inch primary mirror that resulted in an optical defect known as spherical aberration, preventing the telescope from bringing starlight into sharp focus.

But engineers quickly discovered a way to correct Hubble’s blurry vision. They designed a new camera equipped with relay mirrors based on prescriptions that would exactly neutralize the aberration of the primary mirror. Another device, known as COSTAR, is designed to direct corrected light to Hubble’s other instruments.

During a pivotal space shuttle servicing mission in December 1993, the new Wide Field Planetary Camera 2 and COSTAR were installed by spacewalking astronauts. They also replaced Hubble’s solar panels and other critical components.

NASA would launch four more maintenance missions, installing new state-of-the-art instruments and replacing old components such as thin guidance sensors and gyroscopes, which move the telescope from target to target and then lock with rocks. solid stability for detailed observations.

Gyroscopes are essential to Hubble’s longevity. The telescope was launched with six ultra-stable gyroscopes, but only three at a time are needed for normal operation. During the final maintenance mission in 2009, all six were replaced. Three of the new units included very thin “flexible cable” power and data lines that are susceptible to a form of corrosion, while the other three featured an improved design that greatly reduced or eliminated this risk.

In any case, by the time Hubble’s 30th anniversary arrived in 2020, all three of the older models’ six gyroscopes had failed.

One of the remaining three units, gyroscope #3, began functioning erratically early and its performance progressively worsened. On May 24, the gyroscope shut down, putting the observatory into protective “safe mode,” halting scientific operations while engineers discussed their options.

Knowing that gyroscope failures were inevitable, engineers previously developed software that would allow Hubble to operate with just two gyroscopes or even one. The downside was that the telescope could only hit targets in about half the sky at any given time, rather than 85% or so with the three gyroscopes.

Although the telescope could be operated more efficiently with two gyroscopes, engineers concluded that it would make more sense to put one of the two remaining healthy units on standby and operate Hubble with just one gyroscope, keeping the other in reserve for use. . as necessary.

“Our team first developed a plan for gyroscope operations more than 20 years ago, and it is the best way to extend Hubble’s life,” Crouse said. “There are some limitations. It will take us longer to (move) from one target attitude to the next and to be able to stick to that scientific target.

“This will lead to lower efficiency in scheduling scientific observations. We currently schedule about 85 orbits per week and expect to be able to schedule about 74 hours per week, which represents about a 12% reduction in scheduling efficiency.”

Additionally, because the telescope’s movement in single gyroscope mode is less precise and prone to error, “we won’t have as much flexibility as to where we can observe in the sky at any given time. But over the course of a year, we will have the whole sky at our disposal.”

One other limitation: the telescope will not be able to lock onto and track targets closer than Mars’ orbit, although such observations would be rare even in three-gyroscope mode.

Meanwhile, engineers plan to implement a gyroscope control mode in the coming days and return Hubble to scientific operations in the middle of the month.

“We updated the gyroscope reliability assessments… and still came to the conclusion that (we have) a greater than 70 percent probability of operating at least one gyroscope by 2035,” Crouse said.

The infrared-sensitive James Webb Space Telescope is building on Hubble’s legacy, advancing deeper into space and time and producing a steady stream of discoveries as it moves to the forefront of space-based astronomy. But Hubble is still making world-class observations, and astronomers want to keep it running for as long as possible.