The Hubble Space Telescope is a hero in the world of astronomy. And when it suffered a flawed turnaround on October 5, it took a heroic effort on the part of the Hubble team to make it work again. Now we have the first Hubble image after its return to service.
The first image of Hubble after its problems will not be the last, thanks to all its gyroscopes and all the dedicated people who manage the space telescope. Hubble has, or had, six gyros. The telescope is designed to work with three gyroscopes, while the other three serve as backup. This was a vision of the future, because all the gyroscopes finally fail.
Two had previously failed, one in March 2014 and the other in April 2018, leaving him with four. But on the night of 5, the failure left him with only 3 operational gyroscopes, and no backup. When the turn failed, the Hubble went into safe mode. He stopped doing science and pointed his solar panels at the Sun, and waited for instructions.
"This has been an incredible saga, based on the heroic efforts of the Hubble team," – Jennifer Wiseman, senior scientist at the Hubble project at NASA Goddard.
The gyroscope failed at the beginning of a three-day weekend, and the text messages were sent to Hubble team members telling them what had happened. Since 2011, the Hubble control center has been automated, so when the team members met there, it was like in the old days.
More than a dozen members gathered in the control room of the Goddard Space Flight Center. They tried to revive the failed gyroscope, but they were not successful. Then they activated a backup gyroscope, but that reported super high rotation rates of 450 degrees per hour. This with the Hubble only rotating less than one degree per hour.
Dave Haskins is the operations manager of the Hubble mission at Goddard, and according to him this had never happened before. "This is something we have never seen before in any other turn: it qualifies at this high level," Haskins said.
This failure was the final backup for Hubble. Hubble can operate with a single turn, but its abilities are greatly reduced. This "one-gyro" mode was previously designed and tested, but the Hubble team did not want to use it until that was their only final option. The single-turn mode would work, but it would limit Hubble's efficiency and the amount of sky the telescope could observe at a given time of the year. If that happened, then everyone in the astronomical community would know that the end was near the venerable Hubble.
The team members wondered what to do next, and for the first time in several years, there were people in the control room who continuously monitored Hubble's health.
"It shows the versatility of the team." – Dave Haskins, Operations Manager of the Hubble Mission.
"The team joined the staff 24 hours a day, something we have not done in years," shared Haskins. Team members stepped in to take turns: several of Hubble's system engineers, others who help run tests and tests on Hubble's ground systems, and some who used to occupy the Hubble checkpoint but had not done so in a while. "It's been years since they've been on the console doing that kind of shift work," Haskins said. "For me it was without problems, it shows the versatility of the team."
Hubble manager Pat Crouse busied himself that weekend recruiting a team of experts to analyze the unusual behavior of the overspeed gyroscope and see what could be done. That group met for the first time on Tuesday, October 9 and contributed its knowledge about the Hubble recovery. After weeks of analyzing the problem and the test solutions, Crouse's group and the Hubble team suspected that something physical could be blocking the turn. But whatever the problem was, they would have to solve it from the ground. There would be no more missions to fix the Hubble.
"At first we had no idea if we could solve that problem or not." Mike Myslinski, deputy director of operations for the Hubble mission.
The team decided that they would try to dislodge the obstruction, if there was one. They repeatedly changed the gyroscopes through different operating modes. They turned the telescope itself for large quantities. Over time, the high turnover rates of the offender's turn began to fall, and eventually they were almost normal again.
The result was encouraging for the team, but they were still cautious. If any of the gyroscopes reported extremely high turning rates, Hubble would reenter secure mode, interrupting whatever science it was doing. The team loaded a new software into Hubble to protect itself from this happening again. They also put the space telescope through some practice maneuvers to simulate real scientific observations. Hubble performed well, and the team breathed a sigh of relief.
"At first we did not know if we could solve that problem or not," said Mike Myslinski, deputy chief of operations for the Hubble mission, about the high turnaround rates.
Another team was working hard in the background, preparing for an event that has been avoided so far. They were preparing for Hubble to operate in a single turn, with another in reserve as a reserve. That situation was avoided this time, but eventually it will happen. "We know we will have to resort to a gyroscope some day, and we want to be as prepared as possible for that," explained Myslinski. "We always said that once we got down to three gyros, we would do all the work ahead of time for the science of a single turn. That day has come."
For now, however, Hubble is navigating as if nothing had happened. Its first scientific image since the whole thing is from a field of galaxies in the constellation of Pegasus. The image contains star-forming galaxies at a distance of up to 11 billion light years. No problem for Hubble.
"This has been an incredible saga, based on the heroic efforts of the Hubble team," said Hubble project scientist Jennifer Wiseman at NASA Goddard. "Thanks to this work, the Hubble Space Telescope has returned to the full scientific capacity that will benefit the astronomical community and the public in the coming years."
Throughout its many years of operation, Hubble has become a member of the family for scientists and for the rest of us. We know that one day, your mission will end, and that will be it. It will be a sad day. But for now, Hubble is still doing science and capturing some of the most amazing images of the Universe in which we live.
Enjoy it while we have it!