Problems with one of the Hubble Space Telescope’s three remaining gyroscopes, critical for targeting and targeting, have prompted mission managers to switch to a backup control mode that will limit some observations but keep the iconic observatory operating until the 2030s, officials said . Tuesday.
“We still believe there is a very high confidence and probability that we can operate the Hubble very successfully, doing groundbreaking science, for the rest of the 2020s into the 2030s,” Patrick Crouse, the Hubble project manager, told reporters during an afternoon teleconference.
NASA
At the same time, Mark Clampin, director of astrophysics at NASA headquarters, said the agency had ruled out, at least for now, a proposed commercial mission. to increase the HST to a higher height using the SpaceX Crew Dragon spacecraft. The flight was proposed by SpaceX and Crew Dragon veteran Jared Isaacman as a way to extend the life of the Hubble.
By amplifying telescope to a higher altitude, the subtle effects of “thrust” in the extreme outer atmosphere that slowly but surely pull the 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 pilot three more SpaceX “Polaris” missions, including a flight this summer in which he plans to become the first private citizen, who stands there. 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 they are justified.
“Having explored current commercial options, we will not immediately seek to re-strengthen,” Clampin said. “We very much appreciate the in-depth analysis that NASA and the (SpaceX-Isaacman) program and our other potential partners have done, and it certainly gave us more insight into the development considerations for a future commercial reboost mission.
“However, our assessment also raised a number of considerations, including potential risks such as the premature loss of science and some technological challenges. So while resurgence is a possibility for the future, we believe we need to do some more work to determine whether the long-term return on science outweigh the short-term scientific risk.”
Decades of Hubble Service in Space
The Hubble Space Telescope was launched aboard the space shuttle Discovery on April 24, 1990 with a famously faulty mirror, the opening chapter of an unlikely story in which spacecraft repair crews turned a national embarrassment into an international icon of science.
Hubble was initially caught off guard by a manufacturing error in the 94.5-inch primary mirror that resulted in an optical defect known as spherical aberration that prevented the telescope from bringing starlight into sharp focus.
But engineers quickly came up with a way to fix Hubble’s blurry vision. They designed a new camera equipped with regulation-grounded relay mirrors that would precisely counteract the aberration of the primary mirror. Another device, known as COSTAR, was designed to direct the corrected light to other HST instruments.
During a shuttle service mission in December 1993, the new Wide Field Planetary Camera 2 and COSTAR were installed by astronauts. They also replaced Hubble’s solar panels and other important components.
NASA will launch four more servicing missions, installing new, state-of-the-art instruments and replacing aging components such as the critical fine guidance sensors and gyroscopes that move the telescope from target to target and then focus on the rocks. solid stability for detailed observation.
Gyroscopes are critical to HST’s longevity. The telescope was launched with six ultra-stable gyroscopes, but only three are needed at a time for normal operation. During the final servicing mission in 2009, all six were replaced. Three of the new units contained components susceptible to some form of corrosion, while the other three featured improved designs that greatly reduced or eliminated this risk.
In any case, as the 30th anniversary of the Hubble approached in 2020, all three of the six older gyro models had failed.
One of the remaining three units, Gyro No. 3, began operating erratically earlier and its performance gradually deteriorated. On May 24, the gyroscope was disconnected, putting the observatory into a protective “safe mode”, halting science operations while engineers debated their options.
Knowing that gyroscope failure was inevitable, engineers had previously developed software that would allow Hubble to operate as few as two gyroscopes, or even one. The downside was that the telescope could only reach targets on half the sky at a given time instead of 85% or more with all 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 into standby mode and operate the HST with only one gyroscope, with the other in reserve for use. as required.
“Our team first developed a plan for single-gyro operations more than 20 years ago, and it’s the best way to extend Hubble’s life,” Crouse said. “There are some limitations. It will take us more time to move from one target position to the next and to be able to focus on that science target.”
“This will lead to less efficiency in planning science observations. We currently plan about 85 flybys per week and expect (to be) able to plan about 74 hours per week, so about a 12% reduction in planning efficiency.”
Additionally, because the telescope’s motion in single-gyro mode is less precise and subject to error, “we won’t have as much flexibility in terms of where in the sky we can observe at any given time. But over the course of the year, we’ll have the whole sky at our disposal.”
One other limitation: the telescope will not be able to focus and track targets closer than the orbit of Mars, although such observations have been rare even in three-gyro mode.
Meanwhile, engineers plan to implement a single-gyro control mode in the coming days and return HST to science operations around mid-month.
“We’ve updated the reliability assessment for the gyroscopes … and we still conclude that (we have) a greater than 70 percent probability of having at least one gyro operational by 2035,” Crouse said.
Building on Hubble’s legacy, the infrared-sensitive James Webb Space Telescope is moving deeper into space and time, creating a steady stream of discoveries as it moves to the forefront of space astronomy. But Hubble is still making world-class observations, and astronomers want it to work as long as possible.