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Hardware issues earlier this month with the Hubble Space Telescope, which is now approaching the 31st anniversary of its launch, are the latest signs the observatory is showing its age.
Hubble went into safe mode on March 7 due to a software error, and ground crews restored the observatory to full capacity six days later. But efforts to recover the telescope revealed two other problems.
One issue was with the opening door at the front end of the telescope, which was supposed to close when Hubble entered Safe Mode to ensure sunlight didn’t damage sensitive internal optics. Next, engineers discovered a voltage alarm on Hubble’s most widely used scientific instrument, called the Wide Field Camera 3.
Paul Hertz, head of NASA’s astrophysics division, said on March 15 that the two issues were likely related to aging hardware on Hubble.
“We had a software error, and then in two places we found issues with aging spacecraft,” Hertz said in a presentation to NASA’s Astrophysics Advisory Committee.
The software bug that triggered Safe Mode on March 7 came from the spacecraft’s main computer. Ground crews downloaded new software to the computer earlier this year to help compensate for fluctuations in one of Hubble’s gyroscopes, which measure the direction and speed of the spacecraft’s movement as it moves. spins to point to distant galaxies, stars and planets to collect scientific data and imagery.
Hertz said the new software was designed to allow Hubble to turn or pivot from one science target to another more efficiently as it orbits 340 miles (550 kilometers) above Earth. The software was also supposed to alleviate a noise issue in one of the Hubble’s three working gyroscopes.
Hubble’s gyroscopes degrade after Space Shuttle Atlantis astronauts replaced all six gyroscopes during the observatory’s last maintenance mission in 2009. Three of the gyroscopes are still in use, and Hubble needs all three for operations regular.
Engineers devised ways to track some of the telescope’s observations with a single gyroscope, but that would cause limitations as Hubble could point to make astronomical observations.
Ground crews returned Hubble to science operations on March 11 after removing suspicious software code from the computer. NASA said engineers will update the software enhancement to upload it back to the spacecraft in the future.
As the gyroscopes themselves age, the Safe Mode event earlier this month also revealed other signs that Hubble is in the twilight of its lifespan.
The opening door at the top of the telescope failed to close automatically when Hubble entered Safe Mode.
“It turns out that the main side door motor has failed – just an age thing – since 2009,” Hertz said. “So we tipped the door on the redundant motor, which we confirmed to be working perfectly.”
Hertz said the door motors are original parts of Hubble’s construction in the 1980s and were never serviced during the five Space Shuttle maintenance and upgrade missions that NASA sent. at the observatory.
The only time ground crews would have discovered the door motor failure was when the opening door was supposed to close. The last time the door opened and closed was before and after the shuttle’s last maintenance flight in 2009.
“The motor that dies does not stop running, and if the redundant motor dies with the door open, that’s fine,” Hertz said. “This is the preferred mode of failure.”
During efforts to reactivate Hubble’s most widely used science camera, called the Wide Field Camera 3, engineers detected a low voltage reading inside the instrument.
Hertz said the reading was slightly below a preset low-voltage limit, forcing teams to temporarily halt camera reactivation while continuing to resume scientific observations using Hubble’s other science instruments.
Like the gyroscopes and the gate motor, Hertz said NASA determined that the voltage problem inside the wide-field camera 3 was also associated with its age. Astronauts installed the camera in Hubble during the 2009 Shuttle Service Mission.
“One of the voltages dropped slightly, so we lowered that voltage limit to accommodate the aging of the instrument,” Hertz said.
Engineers returned the camera to service on March 13, allowing Hubble to resume operations.
The famous Hubble Space Telescope was developed by NASA with contributions from the European Space Agency. With the withdrawal of the space shuttles, NASA is preparing for the end of Operations Hubble in the years to come.
NASA’s next advanced space observatory – the James Webb Space Telescope – is set to launch in October to expand Hubble’s vision with a larger mirror and a suite of more sophisticated science instruments.
Last year, during virtual celebrations marking the 30th anniversary of Hubble’s launch, mission officials said they expected to get at least five more years of interesting astronomical observations from the long-lived observatory. .
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Follow Stephen Clark on Twitter: @ StephenClark1.
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