Behind the scenes of NASA's Hubble Recovery

The first image captured by Hubble after returning to science on October 27, 2018 shows a field of galaxies in the constellation Pegasus. The observations were taken with the wide-field camera 3 to study galaxies far away in the field. Credit: NASA, ESA and A. Shapley (UCLA)

In the early morning of October 27, the Hubble Space Telescope was targeting a field of galaxies not far from the Great Place of the constellation Pegasus. In the field were galaxies in star formation distant 11 billion light years away. Hubble's wide-field camera 3 recorded an image with the target in view. It was the first image captured by the telescope since he closed his eyes to the universe three weeks ago. It was the result of a team of engineers and experts working tirelessly to make the telescope explore the cosmos again.

"This is an incredible saga, built on the heroic efforts of the Hubble team," said Jennifer Wiseman, Hubble Project Scientist, at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "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."

On the evening of Friday, October 5, the observatory in orbit was put into "safe mode" after the failure of one of its gyroscopes (or "gyros"). Hubble stopped taking scientific observations, directed its solar panels towards the Sun and waited for new instructions from the ground.

It was the beginning of a three-day holiday weekend when members of the spacecraft operations team started receiving text messages on their phone, alerting them that something was wrong with Hubble. In less than an hour, more than a dozen team members had gathered in Goddard 's control room to assess the situation. After unsuccessfully restarting the failed gyroscope, they activated a spare gyroscope on the spacecraft. However, the gyroscope quickly began to show incredibly high rotation rates – about 450 degrees per hour, while Hubble actually ran at less than one degree per hour.

"It's something we've never seen before on other gyroscopes, this rate is so high," said Dave Haskins, Mission Operations Manager at Hubble at Goddard.

Hubble has six gyroscopes on board, and he usually uses three gyroscopes at a time to gather as much scientific data as possible. However, two of his six gyroscopes had already failed. This was the last Hubble backup gyroscope. The operations team had to either find a way to make it work, or turn to a previously developed and tested "gyroscope mode," which would prove effective, but would limit Hubble's effectiveness and quantity. of sky that the telescope could observe. a given period of the year, which the operations team and astronomers want to avoid as long as there is no other choice.

When they decided on the aftermath of things, the team members stayed in the control center to continuously monitor the health and safety of the spacecraft. As the Hubble Control Center became automated in 2011, there was no one left to monitor Hubble 24 hours a day.

"The team is mobilized around the clock, which we have not done in years," Haskins said. The team members stepped in to take shift work – several Hubble systems engineers, others who help perform tests and checks of Hubble 's ground systems and some who had been on the ground. used to manage the Hubble control room but had not done it for a long time. "It's been years since the console did not do this kind of shift work, for me it was transparent, which shows the versatility of the team."

During the holiday weekend, Pat Crouse, Project Manager at Hubble, was recruiting a team of experts from Goddard and the country to analyze the unusual behavior of the auxiliary gyroscope and determine if it could to be corrected. This anomaly review committee met for the first time this Tuesday, Oct. 9, and provided valuable information throughout Hubble's recovery.

It took weeks of creative thinking, continuous testing and slight setbacks to solve the gyro problem that was behaving badly. The members of the operations and review team suspected that the gyroscope could be obstructed in some way by reading. Attempting to dislodge such a blockage, the team tried several times to change the gyroscope from one mode of operation to another and to rotate the spaceship in very large quantities. In response, the extremely high rotation rates of the gyroscope gradually decreased until they were close to normal.

Encouraged but cautious, the team set up new software backups on Hubble to protect the telescope in case the gyro would display excessively high data rates, then sent telescopes maneuvers to simulate real observations. scientists. They watched closely to make sure everything on the spacecraft was working properly. It made.

"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 gyro rates.

In the background, other members of the Goddard team and the Space Telescope Science Institute had begun to prepare in case Hubble should use a single gyroscope, the other working gyroscope being reserved for the reserve. Fortunately, the results of their efforts were not necessary this time, but their work was not for nothing. "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 had always said that once we had three gyroscopes, we would do as much upstream work as possible for the science of a gyroscope." That day has come. "

For the moment, however, Hubble has returned to exploring the universe with three functional gyroscopes, thanks to the hard work of a multitude of people on the ground.

"Many team members have made personal sacrifices to work long hours and provide rest periods to ensure the health and safety of the observatory, while identifying a safe and effective pathway." said Crouse about efforts to return to science. "The recovery of the gyroscope is not only vital for the life expectancy of the observatory, but Hubble is particularly productive in three gyroscope mode, and the extension of this historical period of productivity is a primary goal Hubble will continue discoveries when operating in gyro mode, but due to the tremendous effort and dedication of the mission team, this is not the time. "

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