The $4.7 billion telescope halted on 13 June, with a degrading memory module appearing to be the fault. The main computer stopped receiving the “keep-alive” signal, which is a standard ‘handshake’ (a way of establishing a connection) between the payload and the spacecraft’s main computers.
The main computer automatically put all instruments on the space telescope in safe mode. Nasa restarted the payload computer the following day in an attempt to resume normal operation, but the problem persisted.
Nasa was preparing to switch Hubble to one of its backup modules on 16 June, leaving the computer to run for approximately one day to ensure the problem had been solved, before restarting all instruments and returning to normal operation.
The payload computer on the satellite, a NASA Standard Spacecraft Computer-1 (NSSC-1) system, was built in the 1980s as a part of the Science Instrument Command and Data Handling module – last replaced during a servicing mission in 2009.
The module has various levels of redundancy, which can be activated and deactivated to support the primary system when it needs to.
The Hubble Space Telescope, which has been operating in a low-Earth orbit of 340 miles at 17,000 miles per hour, is set to be soon replaced by the James Webb Space Telescope. Nasa will be sending the new craft into orbit on 31 October aboard an Ariane 5 rocket, giving scientists the opportunity to look back 150 million to 1 billion years after time began – something that has been previously inaccessible to them with Hubble.
Last month, Nasa engineers fully opened the iconic 6.5m wide solar mirror of the James Webb Space Telescope for final tests before its launch, using the same commands and mechanisms on Earth that will control it as it explores the origins of our existence.