Neither Voyager uses solar panels — sunlight is far too weak in the outer solar system. Each carries radioisotope thermoelectric generators (RTGs), which convert the heat released by decaying plutonium into electricity. Because the fuel decays at a fixed rate, the power supply shrinks predictably: roughly 4 watts less every year, on every spacecraft, regardless of what the mission team does. Nearly half a century after launch, that leaves the flight team with a single lever — decide what to switch off, and when. Non-essential instruments went first, then cameras, then, from 2024, science instruments themselves. The August 2026 manoeuvre is a different kind of move: instead of sacrificing another instrument, engineers freed up power from the housekeeping side of the spacecraft, buying at least a year of extra science.

The Voyagers are the only working instruments humanity has beyond the heliopause — the boundary where the Sun's outward flow of charged particles gives way to the interstellar medium. Every extra year of data is a year of direct measurement of a region no other spacecraft has reached and none will reach for decades. The engineering challenge is also instructive: the team cannot touch the spacecraft, cannot send a spare part, and must wait most of a day for a command to arrive and another day for the reply. Extending a mission under those constraints is done entirely through software, sequencing and a very precise understanding of the vehicle's thermal behaviour.