NASA has announced that it has switched off another scientific instrument on board the Voyager 2 probe to save energy and thus prolong the mission, one of the longest ever: the Plasma Science Instrument (PSI), the device that for 47 years has measured the flow of plasma (formed by electrically charged atoms), even managing to reveal in 2018 the moment when the probe left the Sun's sphere of influence to enter interstellar space.
The command to switch off the instrument was given by NASA's Deep Space Network engineers on 26 September: the signal took a full 19 hours to reach Voyager 2 (which is now about 20.5 billion kilometres away) and the return signal took another 19 hours to reach Earth.
The engineers confirm that, in any case, the shutdown command was executed without any problems and that the probe is functioning normally.
In recent years, the instrument had collected a very limited amount of data due to its orientation relative to the direction in which plasma flows in interstellar space. This was another reason why NASA decided to sacrifice it, in order to save energy, considering that the probe, powered by plutonium decay, loses about four watts of power per year.
Launched in 1977, Voyager 2 still has four out of ten instruments active: the goal is to continue collecting data until the next decade with at least one instrument active.
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