For the first time in 5 months, the Voyager 1 probe has returned to transmit sensible data to Earth. The result was obtained after the discovery by the team of NASA technicians of the origin of the fault that affected one of the on-board computers of the venerable space probe, the Flight Data Subsystem or FDS. The loss of communications, which dates back to last November, occurred following the failure of a memory chip containing part of the FDS code. Having identified the source of the fault, NASA technicians proceeded to rewrite the code in order to instruct the computer to skip the block of memory that is no longer usable.
The problem that the technicians had to face is that no other on-board computer memory chip is large enough to store the entire FDS code, a system that deals, among other things, with collecting data from scientific instruments and transmitting them to Earth. The technicians therefore had to proceed with breaking the code into several blocks and re-adapting it so that it can work in this new mode. It is also necessary to remove from the entire probe software code the reference to the portion of memory that is no longer usable.
As a first attempt, technicians restored the part of the code responsible for transmitting telemetry data and the health status of the Voyager 1 probe’s equipment. The changes were transmitted to the probe on April 18th. Due to the enormous distance of the probe, which is now in interstellar space, It takes 22.5 hours to receive a transmission from one side to the other and we had to wait until April 20th before being able to verify the results of the delicate operation, which it was a success: Voyager 1 has finally sent information relating to the state of the probe in a readable way, for the first time since the failure occurred.
Having validated the approach, the NASA team will continue in the coming weeks with the reallocation of the other blocks of software code, including the part that will allow the reception of precious scientific data to be restored. Voyager 1 and Voyager 2 are the only active human-made objects to have crossed the heliopause and entered interstellar space. Hence the extreme importance from a scientific point of view of the two probes, which have now been on the move for 46 years.
