The NASA Jet Propulsion Laboratory (JPL) team monitoring the Voyager 2 probe had to make a difficult but essential decision. On September 26, engineers sent a command to the probe to turn off one of its instruments. Objective: save energy to extend the mission as long as possible.
It took 38 hours for the signal sent by NASA’s Deep Space Network to reach Voyager 2 20.5 billion kilometers away and return to Earth.
An instrument that played a key role in 2018
The instrument that was just deactivated is a plasma spectrometer that measures the amount of plasma and the direction in which it flows. In 2018, it played a crucial role in detecting falling plasma particles from the sun, which helped confirm that Voyager 2 had left the heliosphere and entered interstellar space.
« Mission engineers took steps to avoid turning off a scientific instrument for as long as possible, because the scientific data collected by the twin Voyager probes is unique », Explains NASA. “ No other human-built spacecraft has operated in interstellar space, the region outside the heliosphere. »
Voyager 1 and 2 plutonium fuel
The choice to turn off the plasma spectrometer was dictated by its lesser role in the pursuit of the mission. “ It has collected little data in recent years due to its orientation relative to the direction in which plasma flows in interstellar space “, underlines JPL.
Voyager 1 and its twin Voyager 2 are powered by decaying plutonium and lose about 4 watts of energy per year, according to NASA. Voyager 2 took off on August 20, 1977. On board were 10 scientific instruments. Five were phased out between 1989 and 2008 after they completed their studies of the solar system’s giant planets.
The same strategy was applied to Voyager 1 which now only uses four of its instruments, the latest to have been cut is the ultraviolet spectrometer in 2016.
Voyager 2 can fly with at least one scientific instrument until the 2030s
JPL engineers also turned off all onboard systems that were not essential to the probes’ operation, including some heaters. An essential choice to save energy but which posed a serious problem recently when it was necessary to restart one of Voyager 1’s thrusters.
According to NASA, Voyager 2 has enough power to continue exploring the region in which it operates with at least one operational scientific instrument until the 2030s.