In the morning on October 27, the Hubble Space Telescope focused on the galaxy field near the Great Square in the constellation Pegasus. Stargazing galaxies of up to 11 billion light-years were occupied in the field. With a lens in his intent, a deep Hubble 3 camera shot a picture. It was the first shot to be captured by the telescope because it closed his eyes three weeks ago before the universe, and it was the result of the whole team of engineers and experts who worked tirelessly to get the telescope to explore the universe again.
"It was an incredible saga based on Hubble's heroic effort," said Hubblet senior scientist Jennifer Wiseman of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "Thanks to this work, the Hubble Space Telescope is back to full scientific capability that will benefit the astronomical community and the public for years to come."
In the evening on Friday, Oct. 5, the orbiting observatory got into a "safe mode" after one of his gyroscopes (or "gyros") failed. Hubble stopped accepting scientific observation, orientated his solar panels toward the Sun, and waited for further instructions from the earth.
It was the beginning of a three-day weekend, when the spacecraft operating team began to receive text messages on their phone and warned them that something was going on with Hubble. In less than an hour, more than a dozen team members gathered in the control room at Goddard to assess the situation. After an unsuccessful recovery of an unsuccessful gyro, they activated the backup gyro on the spacecraft. However, the gyro soon began to report incredibly high rotation rates of about 450 degrees per hour when Hubble was actually turning less than an hour-by-hour.
"It's something we've never seen before on any other gyroscope so high," said Dave Haskins, Hubble's Mission Manager at Goddard.
Hubble has six gyroscopes aboard and usually uses three to get as much science as possible. However, two of his six gyros had failed earlier. This was Hubble's last backup gyro. The operating team had to figure out how to work or turn to a previously developed and tested one gyro mode that is proven to work but will limit the effectiveness of Hubble and how many skys can the telescope observe at a given time of the year – the operating team and astronomers want to avoid it until there is another option.
As they decided what to do next, the team members remained in the control center to continuously monitor the health and safety of the spacecraft. Since the Hubble Control Center switched to automated operations in 2011, people were no longer able to monitor Hubble 24 hours a day.
"The team has teamed together continuously, something we have not done for years," Haskins said. Team members have moved in – some Hubble engineers, others who have helped test the treasures of the Hubble ground systems and some of them who used the Hubble Control Room but did not last long. "It's been a couple of years since I worked on the console for a shift job, it was a problem for me, it shows the team's versatility."
During the weekend, Hubble Project Manager Pat Crouse was busy with a team of experts from Goddard and the entire country to analyze the unusual behavior of the backed gyroscope and see if it could be repaired. This revision of the anomaly first met on Tuesday, October 9, and provided valuable insight into the Hubble Recovery.
It took several weeks of creative thinking, continuous tests and minor obstacles to solve the problem of a poor gyro. The members of the operating team and the review committee suspected that the gyro might be an obstacle to its reading. When attempting to remove such blocking, the team repeatedly attempted to switch the gyroscope between different operating modes and the rotating spacecraft in large quantities. In response to the fact that extremely high speeds from the gyroscope gradually decreased until they were close to normal.
Encouraged but cautious, the team outlined the new Hubble Software Guarantees to protect the telescope in case the gyro repeatedly reports disproportionately high rates and then sent the telescope with several practical maneuvers to simulate real scientific observations. They stood far to make sure everything on the spacecraft was working properly. Oh yes.
"At first we did not have any idea whether we could solve this problem or not," said Hubble's deputy, Mike Myslinski, director of operational missions, about high rates for gyroscopy.
In the background, the other Goddard team members and the Space Telescope Science Institute began preparing for a case where Hubble had to switch to a single gyro and the second working gyro held in reserve as a backup. Fortunately, the results of this effort were not needed this time, but their work was not boring. "We know that one day we will have to go into one gyroscope and we want to be as ready as possible," Myslinski said. "We have always said that as soon as we get to three gyros, we would do as much work as possible on one gyro science."
So far, however, Hubble has returned to exploring the universe with three work gyros, due to the hard work of many people on earth.
"Many team members have made personal sacrifices to work long shifts and shifts to ensure the health and safety of the Observatory, while identifying the way forward that was safe and effective," Crouse said of her efforts to return to science. "Recovery of gyroscopy is not only important to the expected life of the Observatory, but Hubble is the most productive in the three-gyrographic regime, and the extension of this historic period of productivity is the main mission goal." Hubble will continue to make amazing discoveries when it is time to work in one gyro regime, efforts and team commitment, there is no time now. "
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Hubble is approaching normal scientific operations
For more information about NASA Hubble, visit: www.nasa.gov/hubble