The Hubble Space Telescope is a hero of the world of astronomy. And when he had a faulty gyro on October 5th, it took a heroic effort on the part of the Hubble team to restart it. We now have the first Hubble photo after it goes back into service.
The first image of Hubble after his troubles will not be the last, thanks to all his gyroscopes and all the dedicated people who manage the space telescope. Hubble has, or had, six gyroscopes. The telescope is designed to work with three gyroscopes, the other three serving as backup. It was an avant-garde thought, because gyroscopes all fail.
Two had already failed – one in March 2014 and the other in April 2018 – leaving four. But in the night of 5, the failure left only 3 operational gyroscopes, without backup. When this gyroscope failed, Hubble went into safe mode. He stopped doing science and directed his solar panels to the sun and waited for instructions.
"This is an incredible saga, built on the heroic efforts of the Hubble team," said Jennifer Wiseman, Hubble Project Scientist, NASA Goddard.
The gyroscope failed at the start of a three day weekend and text messages were sent to Hubble team members to tell them what had happened. Since 2011, the Hubble Control Center has been automated. So when the team members came together, it was like in the good 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 without success. They then activated a backup gyroscope, but it reported extremely high rotation rates of 450 degrees per hour. This with Hubble turning only less than one degree per hour.
Dave Haskins is the Director of Hubble Mission Operations at Goddard, and he says that has never happened before. "It's something we've never seen before on other gyroscopes – this rate is so high," Haskins said.
This failure was the final backup for Hubble. Hubble can work with a single gyroscope, but its capabilities are greatly reduced. This "gyro" mode had already been designed and tested, but the Hubble team did not want to use it as long as it was their only final option. A gyroscope mode would work, but it would limit the effectiveness of Hubble and the amount of sky the telescope could see at any given time of the year. If that happened, all members of the astronomical community would know that the end was near for the venerable Hubble.
The team members wondered what to do next. For the first time in years, people were constantly monitoring Hubble's health in the control room.
"It shows the versatility of the team." – Dave Haskins, Hubble Mission Operations Manager.
"The team rallied around the clock, which we have not done in years," said Haskins. Team members intervened to take shifts: several Hubble systems engineers, others who help perform tests and audits of Hubble ground systems, and some who previously occupied the control room of Hubble. Hubble, but had not done it long. "It's been years since the console did not work that way," Haskins said. "For me, it was seamless. This shows the versatility of the team.
Hubble Manager Pat Crouse was busy this weekend recruiting a team of experts to analyze the unusual behavior of the overspeed gyro and see what could be done. This group met for the first time on Tuesday, October 9, and presented their ideas on Hubble's turnaround. After weeks of thinking about the problem and testing solutions, Crouse's group and Hubble's team suspected that something physical might be interfering with the gyroscope. But whatever the problem, they will have to solve it in the field. There would be more missions to fix the Hubble.
"At first we did not know if we would be able to solve this problem or not." Mike Myslinski, Deputy Director of Hubble Operations.
The team decided to try to clear the obstruction, if there was one. They repeatedly rocked the gyroscopes in different operational modes. They turned the telescope itself in large quantities. Finally, the high turnover rates of the offending gyro began to drop to a near normal level.
The team was encouraged by this result, but it remained cautious. If one of the gyroscopes had extremely high rotation rates, Hubble would go back into safe mode again, disrupting science. The team downloaded new software on Hubble to prevent this from happening again. They also subjected the space telescope to practical maneuvers to simulate real scientific observations. The Hubble performed well and the team breathed a sigh of relief.
"At first we did not know if we would be able to solve this problem or not," Hubble Assistant Operations Manager Mike Myslinski said of high gyroscope rates.
Another team was working in the background and was preparing for a contingency so far avoided. They were preparing for Hubble to operate on one gyroscope, while another was kept in reserve as a reserve. This situation was avoided this time, but it will eventually happen. "We know we will have to use a gyroscope one day and we want to be as prepared as possible for that," Myslinski said. "We always said that once we had three gyroscopes, we would do as much work as possible early on for science on a gyroscope. This day has come.
For now, however, Hubble is sailing as if nothing has happened. His first scientific picture since this whole affair is that of a galaxy field in the constellation Pegasus. The image contains galaxies forming stars up to 11 billion light-years away. No problem for Hubble.
"This is an incredible saga, built on the heroic efforts of the Hubble team," said Jennifer Wiseman, Hubble Project Scientist, NASA Goddard. "Thanks to this work, the Hubble Space Telescope has recovered all of its scientific capabilities that will benefit the astronomical community and the public for years to come.
In its many years of operation, Hubble has become a member of the family of scientists and the rest of the population. We know that one day his mission will end and that will be it. It will be a sad day. But for now, Hubble continues to do science and capture some of the most amazing images of the universe in which we live.
Enjoy it while we have it!