A problem with one of the Hubble Space Telescope’s three remaining gyroscopes, critical for targeting and locking onto targets, has prompted mission managers to switch to a backup control system that will limit some observations but keep the iconic observatory running well into the 2030s, officials said. tuesday
“We still believe that we can do new science in the late 20s and 2030s and run Hubble very successfully,” Hubble project manager Patrick Kruse told reporters in an afternoon teleconference.
NASA
Meanwhile, Mark Clampin, director of astrophysics at NASA headquarters, said the agency has rejected a proposed commercial mission, at least for now. To raise Hubble to higher altitudes SpaceX uses the Crew Dragon spacecraft. SpaceX and Crew Dragon veteran Jared Isaacman suggested the flight as a way to extend Hubble’s life.
By increasing Telescope For higher altitudes, the subtle effects of “drag” on the extreme outer atmosphere, which slowly-but-surely acts to drag a spacecraft back to Earth, can be reduced. Isaacman, a billionaire who chartered the first fully commercial flight to low-Earth orbit in 2021, is training to lead three more SpaceX “Polaris” missions, including one this summer in which he plans to become the first private citizen to stand in an open hatch and float, if not walk, in space.
But project managers say Mars Hubble is in no danger of returning to Earth anytime soon. Recent calculations show it will remain in orbit until at least 2035, allowing time to consider possible options, if necessary, down the road.
“After examining the current business capabilities, we are not going to re-incentivize 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 great insight into the considerations for building a future commercial reboost mission.
“But our assessment raised a number of considerations, including potential risks such as premature loss of science and some technical challenges. So while restarting is an option for the future, we believe some additional work is needed to determine whether the long-term scientific returns outweigh the short-term scientific risk.” .”
Hubble’s decades of service in space
The Hubble Space Telescope launched aboard the spacecraft Discovery on April 24, 1990 with a famously flawed mirror, the opening chapter of an unlikely story in which a spacewalking repair crew turned a national embarrassment into an international icon of science.
Hubble initially suffered from an error during the fabrication of the 94.5-inch primary mirror, which resulted in an optical defect called spherical aberration, which prevented the telescope from focusing starlight sharply.
But engineers quickly found a way to correct Hubble’s blurry vision. They designed a new camera equipped with relay mirrors for prescriptions that precisely counteract the aberration of the primary mirror. Another instrument, called COSTAR, was designed to inject corrected light into Hubble’s other instruments.
During a December 1993 shuttle servicing mission, the new Wide Field Planetary Camera 2 and COSTAR were installed by the spaceflight astronauts. They replaced Hubble’s solar panels and other key components.
NASA will begin four more servicing missions, installing new, modern instruments and replacing aging components such as critical micro-guidance sensors and gyroscopes that move the telescope from target to target and then rock-on-rock for detailed observations.
Gyroscopes are critical to Hubble’s longevity. The telescope launched with six ultra-stable gyroscopes, but only three are needed for normal operation at a time. During the final servicing in 2009, all six were replaced. Three of the new units included components that were prone to 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 rolls around in 2020, three of the six older-model gyroscopes have failed.
One of the remaining three units is the gyroscope no. 3, started acting erratically earlier, and its performance gradually deteriorated. On May 24, the gyroscope was taken offline and the observatory was placed in “safe mode,” halting science operations while engineers discussed their options.
Knowing that gyroscope failures are inevitable, engineers previously developed software that would allow Hubble to operate with two gyroscopes or just one. The downside is that the telescope can only hit targets on half the sky at any given time without all three gyroscopes hitting 85% or more of the target.
Although the telescope could be operated more efficiently with two gyroscopes, engineers decided it would make more sense to keep one of the two remaining healthy units in stand-by mode and power Hubble with just one gyroscope, keeping the other in reserve for use. required amount.
“Our team first developed a plan for a gyro operation 20 years ago, and this is the best mode going forward to extend Hubble’s life,” Kruse said. “There are some limitations. It takes us a long time to move from one target attitude to the next and reach that scientific target.
“That would lead to less efficiency in scheduling science observations. We currently schedule about 85 orbits per week and expect to be able to schedule 74 hours per week, so the scheduling efficiency drops by 12%.”
Additionally, because the telescope’s motion in single-gyroscope mode is less precise and subject to error, “we don’t have much flexibility in where we can look in the sky at any given time. But once a year, we have the whole sky.”
Another limitation: the telescope cannot lock-on and track targets closer than the orbit of Mars, although such observations are rare even in three-gyroscope mode.
Meanwhile, engineers plan to activate the one-gyroscope control mode in the coming days and return Hubble to science operations by the middle of the month.
“We updated the reliability estimates for the gyros … and concluded that (we have) a greater than 70 percent probability of operating at least one gyro by 2035,” Kruse said.
The infrared-sensitive James Webb Space Telescope builds on Hubble’s legacy, pushing deeper into space and time and creating a steady stream of discoveries as space-based astronomy moves to the forefront. But Hubble is still making world-class observations, and astronomers want to keep it working as long as possible.
