Problems with one of the Hubble Space Telescope’s three remaining gyroscopes, crucial for pointing and locking onto targets, have prompted mission managers to switch to a backup control mode that will limit some observations but keep the iconic observatory well into the years will keep it operational by 2030, officials said. Tuesday .
“We still believe that there is very high reliability and that there is a good chance that we can operate Hubble very successfully and do ground-breaking science for the remainder of the 2020s and into the 2030s,” Patrick Crouse said. , the Hubble project manager, told reporters during an afternoon conference call.
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 take Hubble to a greater height using a SpaceX Crew Dragon spacecraft. The flight was proposed by SpaceX and Crew Dragon veteran Jared Isaacman as a way to extend Hubble’s lifespan.
By stimulating the telescope to a higher altitude, the subtle effects of ‘drag’ in the extreme outer atmosphere, which cause a spacecraft to be slowly but surely pulled back towards 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 civilian that will stand in space. an open hatch and float, if not walk, in space.
But project managers said Tuesday that Hubble is not in danger of falling back to Earth anytime soon. The latest calculations show that the observatory will remain in orbit at least until 2035, leaving time to consider possible options in the future, if warranted.
“After exploring the current commercial opportunities, we are not looking for a new impetus now,” Clampin said. “We greatly appreciate the in-depth analysis conducted by the NASA and SpaceX Isaacman program and our other potential partners, and it has certainly given us a better understanding of 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 revival is an option for the future, we believe we need to do some additional work to determine whether the long-term short-term scientific return will outweigh the short-term scientific risk.”
Hubble’s decades of service in space
The Hubble Space Telescope launched aboard the shuttle Discovery on April 24, 1990, with a famously defective mirror, the first chapter of an unlikely story in which spacewalking repair crews turned a national shame into an international icon of science.
Hubble was initially hampered by an error during the manufacturing of the 94.5-inch primary mirror that resulted in an optical defect known as spherical aberration, which prevented the telescope from sharply focusing starlight.
But engineers soon discovered a way to correct Hubble’s blurry vision. They designed a new camera equipped with relay mirrors that were ground according to regulations that would precisely counteract the aberration of the primary mirror. Another device, known as COSTAR, was designed to send corrected light to Hubble’s other instruments.
During a 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 servicing missions, installing new, state-of-the-art instruments and replacing outdated components such as crucial guidance sensors and gyroscopes, which move the telescope from target to target and then secure it with rocks. solid stability for detailed observations.
The gyroscopes are critical to Hubble’s longevity. The telescope was launched with six ultra-stable gyroscopes, but for normal use only three are needed at a time. All six were replaced during the last maintenance in 2009. Three of the new units contained components susceptible to some form of corrosion, while the other three had an improved design that significantly reduced or eliminated that risk.
Regardless, by the time Hubble’s 30th anniversary arrived in 2020, all three of its six older models of gyroscopes had failed.
One of the remaining three units, gyroscope No. 3, started behaving erratically earlier and its performance gradually deteriorated. On May 24, the gyroscope was taken offline, putting the observatory into a protective ‘safe mode’, halting science activities while engineers discussed their options.
Knowing that gyroscope failures were inevitable, engineers previously developed software that allowed Hubble to operate with just two or even one gyroscope. The disadvantage was that the telescope could only reach targets in about half of the sky at any time, rather than 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 Hubble with just one gyroscope, while the other was held in reserve for use. If necessary.
“Our team first developed a plan for single-gyro operations over two decades ago, and it is the best way forward to extend Hubble’s life,” Crouse said. “There are some limitations. It will take us more time to move from one target posture to the next and be able to focus on that scientific target.
“That will lead to lower efficiency in scheduling scientific observations. We are currently scheduling about 85 jobs per week and we expect to be able to schedule approximately 74 hours per week, so a reduction of approximately 12% in scheduling efficiency.”
Furthermore, because the movement of the telescope in single gyroscope mode is less precise and subject 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 entire sky at our disposal.”
Another limitation: the telescope will not be able to track and track targets closer than the orbit of Mars, although such observations were rare even in three-gyroscope mode.
In the meantime, engineers plan to implement the single-gyroscope control mode in the coming days and return Hubble to science operations around the middle of the month.
“We have updated the reliability ratings for the gyros … and we still find that (we) have a better than 70 percent chance of deploying at least one gyro by 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 to the forefront of space astronomy. But Hubble is still making world-class observations, and astronomers want to keep it operational for as long as possible.
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