NASA engineers have developed a new strategy to conserve power aboard Voyager 2, allowing the ageing spacecraft to continue operating three science instruments in interstellar space for longer than previously expected.
The spacecraft, which launched in 1977, is powered by radioisotope thermoelectric generators (RTG) that convert heat from the decay of plutonium into electricity. However, the ageing power system is steadily producing less energy, with Voyager 2 losing approximately four watts of available power each year.
With power margins now extremely tight, NASA’s Jet Propulsion Laboratory team has been progressively switching off non-essential systems and science instruments to keep the spacecraft operating.
The latest intervention, nicknamed the “Big Bang”, involved simultaneously switching off selected powered devices and replacing them with lower-power alternatives.
The challenge was to reduce electricity consumption without allowing the spacecraft to become too cold for its systems to operate reliably.
The resulting power savings are expected to provide sufficient energy to keep Voyager 2’s three remaining science instruments operating for at least another year.
The breakthrough highlights the extraordinary engineering required to maintain spacecraft designed almost half a century ago in an environment millions of kilometres beyond the outer planets.
Voyager 2 is currently in interstellar space, having crossed the heliosphere – the vast region dominated by the sun’s solar wind – in November 2018. It remains the only spacecraft to have visited both Uranus and Neptune.
The spacecraft’s diminishing power supply has become the central constraint on its continuing scientific mission.
As the plutonium in its RTGs decays, NASA engineers must continually balance the electricity required to operate scientific instruments against the energy needed to maintain essential spacecraft systems, including communications and thermal control.
Rather than simply accepting the loss of another instrument, the latest power-saving exercise has allowed mission controllers to preserve additional scientific capability.
Voyager 2’s continued operation provides scientists with a rare opportunity to study the interstellar environment directly from a spacecraft that has travelled beyond the influence of the sun’s solar wind.
The mission’s longevity also offers an extraordinary demonstration of spacecraft engineering, with systems designed in the 1970s continuing to transmit scientific data from interstellar space almost five decades after launch.
NASA’s latest intervention demonstrates how increasingly sophisticated power-management techniques and careful engineering can extract additional years of scientific return from one of the most enduring missions in spaceflight history.
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