NASA
The Hubble Space Telescope resumed science observations on Friday after ground teams spent most of the past three weeks evaluating the finicky gyroscope’s performance, according to NASA.
The finicky gyroscope is a key part of the observatory’s pointing system. Hubble’s gyro measures the spacecraft’s rotational speed and helps the telescope point its aperture toward distant cosmic wonders.
Nearly 34 years after its launch aboard NASA’s Space Shuttle Discovery in 1990, Hubble is still providing valuable scientific data to astronomers. In addition, his five shuttle maintenance missions repaired Hubble, upgraded its scientific instruments, and replaced hardware that had deteriorated from prolonged use in space. Among other tasks, the astronaut who participated in the last shuttle repair flight in 2009 installed his six new gyroscopes on Hubble.
Moving parts sometimes break
The gyro has long been one of Hubble’s most high-maintenance components. According to NASA, the wheels inside each gyro rotate at a constant speed of 19,200 revolutions per minute, and the wheels are sealed inside a cylinder suspended in a thick liquid. Electronics inside each gyro detect very small movements of the wheel’s axis and provide information to Hubble’s central computer about the spacecraft’s rotational speed. Hair-thin wires carry the signals from the gyroscope, and these wires can degrade over time.
Three of the six gyros installed on Hubble in 2009 failed, but the remaining three are still operational. His three gyros that are still functional are based on new designs for longer life, but one of his has shown signs of wear in recent months. The gyroscope, called Gyro 3, has consistently exhibited “consistently noisy behavior,” said Pat Close, Hubble project manager at NASA Goddard Space Flight Center.
Because Hubble typically requires three gyros to operate properly, ground controllers had Gyro 3 turned off for about seven years until Hubble needed Gyro 3 in 2018. Another gyroscope failed, leaving only three devices still working.
“There were problems going back to August,” Kraus told Ars this week. “It was like sporadically outputting velocity information that didn’t match the observed spacecraft body velocity, but it was short-lived and we were wondering what that performance was and to what extent we would tolerate it.” I was characterizing what I could do.”
In November, the gyro’s performance deteriorated after it fed incorrect data to Hubble’s control system. The gyroscope sensed that the spacecraft was changing its direction, even though it wasn’t actually moving. “That led to an incorrect posture and a little bit of a misalignment,” Kraus said.
Hubble’s automated software detected errors and put the spacecraft into “safe mode” twice last month. Hubble quickly resumed scientific observations each time, but on November 23, it went into safe mode again. Hubble administrators spent extra time collecting data on Gyro’s health. Engineers ordered Hubble to move back and forth, but the suspect’s gyro seemed to work consistently well.