Trouble with one of the Hubble telescope’s three remaining gyroscopes, critical for aiming and locking onto targets, has prompted mission managers to switch to a backup control mode that will limit some observations but keep the iconic observatory running until the 2030s, officials said. Tuesday.
“We still believe there is a very high probability and probability that we can operate Hubble very successfully, doing ground-breaking science, through the rest of the 20s and into the 2030s,” Patrick Crouse, the manager, told reporters. of the Hubble project, 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 raise 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 life.
Inciting telescope at a higher altitude, the subtle effects of “drag” in the extreme outer atmosphere, which act to slowly but surely pull a spacecraft back to Earth, can be reduced. Isaacman, a billionaire who has taken 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 the first private citizen to stand in an open hatch and float, if not walk, in space.
But project managers said Tuesday that Hubble is in no danger of falling back to Earth anytime soon. Recent calculations indicate that the observatory will remain in orbit until at least 2035, allowing time to consider possible options, if warranted, down the road.
“After exploring the current trading capabilities, we will not pursue a re-strengthening now,” Clampin said. “We greatly appreciate the in-depth analysis conducted by NASA and the (SpaceX-Isaacman) program, and our other potential partners, and it certainly gives us better insight into the considerations for developing a future commercial recovery 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 reconstruction is an option for the future, we believe we need to do some additional work to determine whether “The long-term return of science will outweigh the risk of short-term science.”
Decades of Hubble’s Service in Space
The Hubble Space Telescope launched aboard Discovery on April 24, 1990, with a famously flawed mirror, the opening chapter of an unlikely tale in which spacewalk repair crews turned a national embarrassment into a international icon of science.
Hubble was initially hampered by an error during the fabrication 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 found a way to correct Hubble’s blurry vision. They designed a new camera equipped with relay mirrors based on recommendations that would exactly counteract the deflection of the primary mirror. Another instrument, known as COSTAR, was designed to direct the 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 spacewalk astronauts. They also replaced Hubble’s solar panels and other critical components.
NASA would go on to launch four more servicing missions, installing new, more advanced instruments and replacing aging components such as critical guidance sensors and gyroscopes, which move the telescope from target to target and then jam. solid durability for detailed observations.
Gyroscopes are critical 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 service mission in 2009, all six were replaced. Three of the new units included components susceptible to some form of corrosion, while the other three had an improved design that greatly reduced or eliminated that risk.
In any case, by the time Hubble’s 30th anniversary rolled around in 2020, three of the older model’s six gyroscopes had failed.
One of the three remaining units, gyro no. 3, started acting erratically earlier and its performance gradually deteriorated. On May 24, the gyroscope was taken offline, putting the observatory into protective “safe mode,” halting science operations while engineers discussed their options.
Knowing that gyroscope failures were inevitable, engineers first 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 half the sky at any 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 on standby and operate Hubble with only one gyroscope, keeping the other in reserve for use. as it should be.
“Our team first developed a plan for single-pass operations more than 20 years ago, and it’s the best way forward to extend Hubble’s life,” Crouse said. “There are some limitations. It’s going to take us longer to (move) from one objective stance to another and to be able to lock in on that scientific objective.
“This will lead to lower efficiency for planning science observations. We currently plan about 85 orbits per week and expect (to be) able to plan about 74 hours per week, so about a 12% reduction in planning efficiency. “
Additionally, because moving 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 full sky at our disposal”.
Another limitation: the telescope will not be able to lock on and track targets closer than the orbit of Mars, although such observations were rare even in triple-gyro mode.
Meanwhile, engineers plan to implement control mode with a gyroscope in the coming days and return Hubble to science operations around the middle of the month.
“We updated the reliability estimates for the orbiter … and we still conclude that (we have a) greater than 70 percent probability of operating at least one orbiter by 2035,” Crouse said.
The infrared-sensitive James Webb Space Telescope is building 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-based astronomy. But Hubble is still making world-class observations, and astronomers want to keep it running as long as possible.