The 28-year-old Hubble space telescope has temporarily suspended operations because of a gyroscope failure.
NASA said Hubble went into "safe mode" after one of the three gyroscopes actively being used to point and steady it failed.
"Safe mode puts the telescope into a stable configuration until ground control can correct the issue and return the mission to normal operation," NASA said.
"Hubble's instruments still are fully operational and are expected to produce excellent science for years to come."
Hubble is equipped with six gyroscopes to orient the telescope. All six were replaced in 2009 but since then three of them have become unusable.
Now one of the remaining three is not working as expected, leaving Hubble with just two working gyros and it needs at least three for optimal operations.
On Friday, the Hubble Space Telescope went into safe mode due to a failed gyro – used to keep the telescope precisely pointed for long periods. Mission experts are taking steps to return Hubble to great science. More updates will follow.
— Hubble (@NASAHubble) October 8, 2018
Dr Rachel Osten, the deputy head of the Hubble mission, said the first step "is to try to bring back the last gyro, which had been off, and is being problematic".
NASA said staff at the Goddard Space Flight Center and the Space Telescope Science Institute were conducting tests and analysis to get the gyro working again.
NASA said if they are unable to recover the malfunctioning gyro Hubble will resume science operations using just one device.
"While reduced-gyro mode offers less sky coverage at any particular time, there is relatively limited impact on the overall scientific capabilities," NASA said.
Hubble has made numerous outstanding observations of the cosmos since it was deployed in 1990.
The James Webb Space Telescope, the successor to Hubble, is scheduled to be launched in March 2021.
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