Problems with one of the Hubble Space Telescope’s three remaining gyroscopes, essential for aiming and locking on targets, have prompted mission managers to switch to a backup control mode that will limit some observations, while still allowing the observatory iconic to operate into the 2030s, officials said. Tuesday.
“We still believe that there is a very high reliability and a very high probability that we can operate Hubble very successfully, doing groundbreaking science, for the remainder of the 20s and into the 2030s,” said Hubble project manager Patrick Crouse speaks to reporters during an afternoon conference call.
NASA
Meanwhile, Mark Clampin, director of astrophysics at NASA Headquarters, said the agency has ruled out, at least for now, a proposed commercial mission. to propel 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 at a higher altitude, the subtle effects of “drag” in the extreme outer atmosphere, which act to slowly but surely bring a spacecraft back to Earth, could be reduced. Isaacman, a billionaire who chartered the first fully commercial flight into 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 participate . an open hatch and float, if not walk, in space.
But project officials said Tuesday that Hubble is unlikely to fall back to Earth anytime soon. Latest calculations show that the observatory will remain in orbit until at least 2035, allowing time to consider possible options, if warranted, in the future.
“Having explored current business capabilities, we will not pursue a relaunch at this time,” Clampin said. “We greatly appreciate the in-depth analysis conducted by NASA and the SpaceX-Isaacman program, as well as our other potential partners, and it has certainly given us greater insight into the considerations for developing a future commercial reboost mission.
“But our assessment also raised a number of considerations, including potential risks such as premature loss of science and some technological challenges. So while recovery is an option for the future, we believe we must “conduct additional work to determine whether the long-term short-term scientific return will exceed the short-term scientific risk.”
Hubble’s Decades of Service in Space
The Hubble Space Telescope was launched aboard the shuttle Discovery on April 24, 1990, with a notoriously defective mirror, the first chapter in an improbable story in which spacewalking repair crews transformed a national embarrassment into an icon international science.
Hubble was initially hampered by an error in manufacturing the 94.5-inch primary mirror, which resulted in an optical defect known as spherical aberration, preventing the telescope from focusing starlight.
But engineers quickly found a way to correct Hubble’s blurry vision. They designed a new camera equipped with relay mirrors adapted to prescriptions that would exactly neutralize the aberration of the main mirror. Another device, known as COSTAR, was designed to direct the corrected light to Hubble’s other instruments.
During a pivotal 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 then launch four more servicing missions, installing new cutting-edge instruments and replacing aging components such as fine guidance sensors and critical gyroscopes, which move the telescope from target to target and then lock on 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 last maintenance mission in 2009, all six were replaced. Three of the new units included components susceptible to some form of corrosion, while the other three featured an improved design that significantly reduced or eliminated this risk.
Regardless, by the time of Hubble’s 30th anniversary in 2020, all three of the older models’ six gyroscopes had failed.
One of the three remaining units, gyroscope No. 3, began acting erratically earlier and its performance gradually deteriorated. On May 24, the gyroscope was taken offline, putting the observatory in protective “safe mode,” halting science operations while engineers discussed their options.
Knowing that gyroscope failures were inevitable, engineers developed software that would allow Hubble to operate with just two gyroscopes, or even just one. The downside was that the telescope could only hit targets in about half the sky at any given time, instead of 85% or more with all three gyroscopes.
Even though the telescope could operate more efficiently with two gyroscopes, engineers concluded that it would make more sense to put one of the two remaining healthy units into sleep mode and operate Hubble with just one gyroscope, keeping the other in reserve for its use. as required.
“Our team first developed a plan for operations with a single gyroscope more than 20 years ago, and it is the best way to extend the life of Hubble,” Crouse said. “There are certain limits. It will take us more time to (move) from one target attitude to another and to be able to lock in on this scientific objective.
“This will result in a decrease in planning efficiency for science observations. We currently plan about 85 orbits per week and expect to be able to plan for about 74 hours per week, a reduction of about 12% in planning efficiency .”
Additionally, because telescope movement in single gyroscope mode is less precise and error-prone, “we won’t have as much flexibility in where we can observe in the sky at any given time.” year, we will have the whole sky at our disposal.”
Another limitation: The telescope will not be able to lock on and track targets closer than Mars’ orbit, although such observations will be rare even in three-gyroscope mode.
In the meantime, engineers plan to implement the one-gyroscope control mode in the coming days and return Hubble to science operations around the middle of the month.
“We’ve updated the gyroscope reliability assessments…and we still come to the conclusion that (we have) a greater than 70 percent probability of operating at least one gyroscope through 2035,” Crouse said.
The infrared-sensitive James Webb Space Telescope builds on Hubble’s legacy, reaching deeper into space and time and producing a steady stream of discoveries as it moves deeper at the forefront of space astronomy. But Hubble continues to make world-class observations, and astronomers want to keep it running for as long as possible.