The Hubble Space Telescope, launched in 1990, is still operating. But he begins to suffer from the ravages of old age. On May 24, Hubble automatically entered safe mode, suspending its science operations, due to a malfunction in one of its three gyroscopes.
The latter has already led to several consecutive pauses of the space telescope. The American space agency therefore decided on June 4: Hubble will continue its observations, but with one gyroscope instead of three.
A gyroscope that works above
Hubble’s gyroscopes measure the telescope’s rotation speed and are part of a system that precisely determines and controls its direction. During the telescope’s last maintenance mission, in 2009, astronauts in Earth orbit repaired two malfunctioning science instruments and installed two new ones.
To extend Hubble’s life, they replaced the batteries and all six gyroscopes.
Since then, the condition of the gyroscopes gradually deteriorated, and until today only three are functional. The one that had a series of malfunctions, and which Hubble put into safe mode at the end of May, was almost constantly saturated.
Thus, it turns out that the telescope’s rotation speed is the highest possible value, regardless of the actual rotation speed. Although the engineers managed to reset the gyroscope electronics to normal values several times, the results were only temporary and the problem reappeared, especially in late May.
A degraded way to continue scientific operations
In order for scientific operations to continue, NASA is switching the telescope to a new mode of operation: Hubble will operate with one gyroscope while leaving the other available for future use.
With this degraded mode, NASA expects some limitations. The telescope will take longer to rotate and aim at the target and will not have as much flexibility in where it can observe.
It also won’t be able to track moving objects closer than Mars, although these are rare targets for Hubble. Still: This switch from three to one gyroscope will allow continued observations with Hubble, which the space agency hopes will operate well into the next decade.