Mission managers of the Hubble Space Telescope have implemented a backup control mode due to a problem with one of its gyroscopes, which are crucial for aiming and locking onto targets. This new mode will limit some observations, but will allow the observatory to continue operating until the 2030s. Despite the issue, officials remain confident in the reliability of the telescope and its ability to conduct groundbreaking scientific research. NASA has also decided against a proposed commercial mission to boost Hubble to a higher altitude using a SpaceX Crew Dragon spacecraft, at least for the time being. This suggestion was made by SpaceX and Crew Dragon veteran Jared Isaacman as a means to extend the lifespan of the Hubble.
By increasing the altitude of the telescope, the adverse effects of atmospheric “drag” in the outermost regions, which gradually pull a spacecraft back towards Earth, could be minimized. Isaacman, a billionaire who organized the first fully commercial journey to low-Earth orbit in 2021, is currently undergoing training to lead three more SpaceX “Polaris” missions. One of these missions, scheduled for this summer, aims to make Isaacman the first private individual to venture into space, potentially floating or even walking outside the spacecraft.
However, project managers assured on Tuesday that the Hubble telescope is not at risk of falling back to Earth in the near future. Recent calculations indicate that the observatory will remain in orbit until at least 2035, providing ample time to consider potential options, if necessary, further down the line.
Clampin stated that after evaluating the current commercial capabilities, they have decided not to pursue a re-boost at this time. He expressed gratitude for the thorough analysis conducted by NASA, the SpaceX-Isaacman program, and other potential partners, as it has provided valuable insights into the factors involved in developing a future commercial reboost mission.
However, their assessment has identified several considerations, including potential risks such as the premature loss of scientific data and technical challenges. While the option of re-boost remains for the future, they believe further investigation is necessary to determine whether the long-term scientific benefits outweigh the short-term risks.
Throughout its years of operation in space, the Hubble telescope has served diligently.
On April 24, 1990, the Hubble Space Telescope was launched on the shuttle Discovery, but it had a major flaw – its mirror. This flaw, known as spherical aberration, prevented the telescope from producing clear images.
However, a remarkable turnaround took place as spacewalking repair crews transformed this national embarrassment into a global symbol of scientific achievement. Engineers devised a solution by designing a new camera with relay mirrors that compensated for the primary mirror’s aberration. Additionally, a device called COSTAR was created to direct corrected light to Hubble’s other instruments.
This successful correction allowed the Hubble Space Telescope to overcome its initial setback and become an iconic tool for scientific exploration.
In December 1993, during a crucial shuttle servicing mission, spacewalking astronauts successfully installed the new Wide Field Planetary Camera 2 and COSTAR on the Hubble Space Telescope. Additionally, they replaced the telescope’s solar panels and other vital components.
Following this mission, NASA conducted four more servicing missions, during which they installed cutting-edge instruments and replaced aging components such as the critical fine guidance sensors and gyroscopes. These gyroscopes play a crucial role in maintaining the telescope’s functionality and longevity. Although the Hubble was initially equipped with six ultra-stable gyroscopes, only three are required for normal operation. In the final servicing mission of 2009, all six gyroscopes were replaced. Notably, three of the new units had components susceptible to a specific type of corrosion, while the other three featured an improved design that significantly reduced or eliminated this risk.
By the time Hubble reached its 30th anniversary in 2020, all three of the older-model gyroscopes had stopped functioning. Among the remaining three units, gyroscope No. 3 began exhibiting erratic behavior and its performance deteriorated over time. Consequently, on May 24, the gyroscope was deactivated, causing the observatory to enter a protective state known as “safe mode.” During this period, scientific operations were halted while engineers deliberated their options.
Anticipating gyroscope failures, engineers had previously developed software that would enable Hubble to function with just two or even one gyroscope. However, this came with a drawback; the telescope’s ability to observe targets was limited to only about half of the sky at any given time, compared to the 85% or more coverage achievable with all three gyroscopes.
After considering the options, engineers decided that operating the telescope with just one gyroscope and keeping the other as a backup would be more practical than using two gyroscopes. This decision was made even though the telescope could function more efficiently with two gyroscopes.
“Our team came up with a plan for operating with one gyroscope over two decades ago, and it remains the best approach for extending Hubble’s lifespan,” explained Crouse. “However, there are some limitations to this mode of operation. It will take us longer to transition from one target position to another, as well as to accurately lock onto scientific targets.
As a result, the efficiency of scheduling science observations will be reduced. Currently, we schedule around 85 orbits per week, but with the one-gyroscope operation, we expect to be able to schedule about 74 hours per week, leading to a decrease in scheduling efficiency of approximately 12%.”
Furthermore, the telescope’s movement in single-gyroscope mode is less precise and more prone to errors, resulting in limited flexibility in choosing observation locations in the sky. However, over the course of a year, the telescope will still have access to the entire sky.
Another constraint is that the telescope will be unable to track targets closer than the orbit of Mars. It is worth noting that such observations were infrequent even when the telescope operated with three gyroscopes.
In the near future, engineers plan to implement the one-gyroscope control mode and resume scientific operations around the middle of the month.
Crouse stated, “We have updated reliability assessments for the gyros… and we still have a greater than 70 percent probability of operating at least one gyro until 2035.”
The James Webb Space Telescope, which is capable of detecting infrared radiation, is taking advantage of Hubble’s accomplishments and surpassing them by exploring deeper into space and time. It continues to make remarkable discoveries and is becoming a prominent player in space-based astronomy. However, astronomers are keen on extending Hubble’s operational lifespan since it continues to deliver exceptional observations.