The iconic Hubble Space Telescope has been offline since July 13, when its payload computer stopped working. This computer is responsible for managing the scientific instruments and making sure that the data they produce is sent back to NASA on Earth. The glitch has made the space telescope perform any observations since then and has put the scientific instruments in safe mode.

On Wednesday, July 14, NASA indicated that it had narrowed down the source of what caused the glitch. On July 16, NASA announced it has switched the telescope's backup computing hardware and potentially ending the month-long uncertainty of the Hubble Space Telescope's future, ARS Technica reported.

 Hubble Space Telescope is Back On Once Again! What's Next?
(Photo: Wikimedia Commons)
The Hubble Space Telescope (HST) heads back toward its normal routine in orbit after a week of servicing and upgrading by the STS-109 astronaut crew on board the Space Shuttle Columbia in March 2002.

Hubble Space Telescope's Backup Computing Hardware

Hubble Space Telescope is equipped with backups for all its computing hardware and backups for the backup for its memory. However, the past attempts of NASA engineers to switch to one of the backups have resulted in similar errors.

These tests suggested that the problem is not in the space telescope's memory or processing hardware but in the hardware that supports the entire operation of the floating observatory. The Hubble team then decided to focus their attention on the power supply component of the space telescope.

According to NASA, the information they gathered from the unsuccessful multi-day tests of restarting reconfiguring the computer and the backup computer has led them to determine that the probable cause of the problem is its Power Control Unit (PCU).

The PCU controls that voltage supply to the hardware of the payload computer, making sure that it is getting enough. The PCU is comprised of a power regulator that provides constant five volts of electricity to the payload computer and its memory, while a secondary protection circuit senses the voltage leaving the power regulator.

It is the secondary circuit's responsibility to tell the payload computer to stop working when the voltage it receives falls below or exceeds the allowable levels.

Based on the analysis, the team of engineers fixing the Hubble Space Telescope suggests that either the voltage level from the regulator exceeded or fell below acceptable levels that activated the secondary protection circuit or the secondary protection circuit has degraded after many years of use and has left it to this inhibit state.

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What's Next for Hubble Space Telescope?

Now that the backup computing hardware of the Hubble has been switched on and successfully getting the space telescope back online, the team is keeping a close watch to make sure that everything is working accordingly. reported that the switch to the backup computing hardware included the backup PCU and the backup Command Unit/Science Data Formatter (CU/SDF). Other pieces of the hardware were also swapped to their backups so that the telescope can now function.

After the successful turning back on the Hubble, the team now turns their focus on its payload computer, loaded it with flight software, and returned the Hubble Space Telescope to its "normal operations mode."

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