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After a brief radio silence, the Voyager 1 space probe reestablished communication with Earth using a backup system that had been inactive since 1981. It automatically initiated this procedure after a fault protection system turned off its radio transmitter main, in order to save energy. Engineers are currently working to identify the cause of the outage and hope to restore the main communications system soon.
Launched in 1977, Voyager 1 was the first human-made object to approach the edge of the solar system and cross the heliosphere – the zone of influence of the solar wind. It reached interstellar space in 2012 and is currently 24 billion kilometers from Earth, while its twin, Voyager 2, reached there in 2018. Despite its advanced age and the distance traveled, the probe continues to transmit data to Earth. However, these long years spent in space have had detrimental consequences on its instruments. “ Their advanced age has led to an increase in the frequency and complexity of technical problems and new challenges for the mission engineering team », Explains NASA in a blog post.
In order to best preserve its performance and compensate for the weakening of its power supply, NASA has for example been forced to turn off 6 of its 10 instruments since 2020. Towards the end of last year, the probe also encountered a problem major technical problem linked to its on-board computer and preventing it from transmitting coherent data. After several months of investigation, the problem was finally resolved in April this year.
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On October 18, NASA teams identified a new communication problem. After receiving an instruction on October 16 to activate one of its heaters, the probe temporarily suspended communication and activated its automatic fault protection system, in order to save energy. “ While Voyager 1 should have had sufficient power to operate the heater, the command engaged the fault protection system », Explains NASA.
Illustration showing the current position of Voyager 1. © NASA
An emergency radio transmitter not used since 1981
To send instructions to Voyager 1, NASA uses the Deep Space Network (DSN) radio antenna array. For each instruction sent, the probe must normally respond by transmitting technical data, confirming to teams on Earth that the command has been received. This round trip takes about two days, as it takes nearly 23 hours for commands to reach the probe and another 23 hours for its response to reach Earth.
According to NASA, the interruption in communication appears to have been caused by the probe's failure protection system. This system notably saves energy by deactivating non-essential instruments if the power supply is overloaded. The anti-failure system reduced the transmission speed of the probe's main (X-band) radio transmitter for this purpose. “ This mode requires less power from the spacecraft, but it also changes the X-band signal that the Deep Space Network must listen for », Explain the researchers. Following this procedure, the team was able to detect a signal later in the day on October 18 and communication temporarily stabilized.
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However, during the day of October 19, communication was completely suspended when the X-band transmitter was turned off. The probe then switched to a second S-band radio transmitter – a first since 1981 – because it consumes much less energy. According to engineers, this could be because the fault protection system was used twice as much as expected. And although these signals are significantly weaker than those in X-band, they were still able to be detected by the DSN sensors.
However, although the probe has finally re-established communication with Earth using its second transmitter, the team does not yet want to take the risk of trying to send X-band instructions, as this could activate new fault protection system. An S-band instruction was then sent on October 22 to confirm that the transmitter was working correctly and the probe sent its response two days later.
As a next step, NASA engineers plan to investigate what may have activated the fault protection system so that X-band radio communication can be restored. The team is now working to gather information that will help them understand what happened and return Voyager 1 to normal operations », Indicates the agency. It will likely take several days or even weeks before technical operators can identify the source of the problem.
