The legendary Voyager 1 probe has not had an easy time of late; NASA almost lost it several times. It was only thanks to the talent and dedication of a caring team of engineers that she was able to emerge from an almost hopeless situation this summer – a true small “miracle”. Unfortunately, his sister is not in an enviable situation either; very recently, the American agency was forced to deactivate one of Voyager 2’s scientific instruments, whose energy reserves are visibly diminishing.
At the time of writing, the probe is moving a little more than 20 billion kilometers from Earth. And even if it cannot be proud of the records or the historic photo album of Voyager 1, to which we owe in particular the first ” family photos » of the solar system or the legendary « pale blue dot », she continues to bring data to NASA by tirelessly probing the depths of the cosmos.
Unique data threatened by lack of energy
This data is incredibly valuable. In November 2018, Voyager 2 became the second craft to leave the zone of influence of the solar winds and venture into interstellar space — a feat that only its twin had previously accomplished and which has never been replicated since. It therefore provides virtually unique information that pushes engineers to keep it alive as long as possible. Unfortunately, it is becoming increasingly difficult to maintain this diet. Because after almost 50 years of work, the material is slowly but surely reaching the end of its life.
The nuclear reactors of the two devices, in particular, are beginning to show signs of weakness. Each year, their energy production decreases by approximately 4 watts, and they are no longer capable of producing enough energy to power all of the subsystems. NASA therefore deactivated all unnecessary hardware, such as certain radiators, in order to extend the autonomy as much as possible. But even with these savings, the situation becomes critical, confronting operators with difficult choices.
The Plasma Science Instrument takes his last breath
In the case of Voyager 2, NASA engineers have now been forced to deactivate one of its four onboard instruments to preserve the others. Their choice fell on the Plasma Science Instrumentwhich measures the intensity and direction of plasma flows traveling through space.
It was once one of the most important elements of the probe; it was thanks to him in particular that engineers were able to confirm that Voyager 2 had officially entered interstellar space, when the density of plasma originating from the Sun dropped particularly suddenly.
Since this transition phase, the instrument has not been very productive. It only reports useful data every three months. Therefore, NASA has determined that this was the weak link, and decided to deactivate it so that the other instruments can continue to do their job.
The fateful order was sent on September 26. It took about 19 hours to reach the probe via the Deep Space Network. After another 19 hours, NASA received confirmation that Voyager 2 had received this signal: the detector is officially out of service.
The good news is that Voyager 2 has not completely lost its ability to analyze interstellar plasma. Another instrument, the Plasma Wave Subsystem, is also capable of estimating its density. The bad news is that it does so indirectly, and therefore does not benefit from the same level of precision as the PSI. Consequently, this is not a negligible loss, especially since the twin probe has also been deprived of this instrument for a long time; THE Plasma Science Instrument of Voyager 1 ceased functioning as early as the 1980s. Overall, the Voyager mission therefore lost a substantial part of its capacity to produce data.
The end is near, but the adventure continues
At least this concession will allow the probe to continue operating for a few more years… but other sacrifices will still have to be made to maximize its lifespan. Currently, NASA estimates that Voyager 2 will be able to continue to operate until the start of the next decadebut with a single operational instrument. Two additional data sources will therefore be deactivated in the coming years.
And to achieve this goal, you will also have to count on a little help from destiny. The misadventures of Voyager 1, which still had to be saved at the last minute at the beginning of Septemberclearly shows that the mission is hanging by a thread after almost half a century of good and loyal service.
We will therefore have to cross our fingers that the two machines hold up as they approach their 50th anniversary, in 2027. Until then, it will be appropriate to properly savor the latest adventures of this legendary couple who marked the the history of science, but also the collective imagination with a hot iron. Hearts up, Travel!
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