On April 17, 2026, a command traveled more than 15 billion miles from a control room at NASA’s Jet Propulsion Laboratory to the oldest functioning spacecraft ever built. When it arrived, roughly 22 hours later, Voyager 1’s Low-Energy Charged Particles experiment went silent. The shutdown left the 49-year-old probe with just two of its original 10 science instruments still running, the latest in a series of deliberate sacrifices to keep humanity’s most distant machine alive a little longer.
Why NASA pulled the plug on LECP
Voyager 1 draws electricity from three radioisotope thermoelectric generators, or RTGs, that convert heat from decaying plutonium-238 into power. As the isotope weakens, output gradually declines. NASA has noted that the spacecraft launched in 1977 with more than 470 watts available, and commonly cited estimates place the annual loss at roughly four watts per year, though the agency has not published a precise current figure. By early 2026, available power had fallen so low that mission controllers could no longer run every remaining system without risking a broader failure.
The decision to shut down LECP was not a surprise. NASA had already turned off the cosmic ray subsystem on February 25, 2025, and signaled at the time that LECP would likely be next. The April 17 command, confirmed in the Voyager team’s official blog, followed that plan almost to the letter. Each shutdown frees a small but critical margin of power for the systems that remain.
LECP had spent decades measuring low-energy ions and electrons, first during the grand tour of Jupiter and Saturn in the late 1970s and early 1980s, then across the long cruise through the outer solar system, and finally in interstellar space after Voyager 1 crossed the heliopause in August 2012. Its data helped scientists map the charged-particle environment at the boundary between the sun’s magnetic bubble and the galaxy beyond. Losing that stream removes a key diagnostic tool for understanding how the solar wind interacts with the interstellar medium.
What two instruments can still do
The survivors are the magnetometer, which tracks magnetic field strength and direction, and the plasma wave subsystem, or PWS, which detects electric and magnetic wave oscillations in the surrounding plasma. According to NASA’s mission instruments page, the original suite included 10 tools. Several were switched off decades ago after the planetary flybys ended, but the recent shutdowns are driven purely by dwindling power rather than scientific irrelevance.
Together, the magnetometer and PWS still provide a real-time window into conditions no other functioning spacecraft can observe. Decades of peer-reviewed work, cataloged in archives such as the University of Iowa plasma wave group’s Voyager publication list, show that magnetic field and plasma wave data can reveal shock fronts, density structures, and turbulence in interstellar space. However, much of that research relied on correlations with particle instruments like LECP and the cosmic ray subsystem. How much the two remaining sensors can accomplish on their own, without that complementary data, is an open question the mission team has not publicly addressed.
The clock no one can stop
No official timeline specifies when the magnetometer or PWS will face the same fate. NASA’s public mission pages acknowledge that power loads must continue to be shed as electrical output decreases, but the agency has not published exact current wattage figures or a dated schedule for the final two instruments. Estimates in the space-science community suggest the generators could drop below minimum operating thresholds within the next few years, though those projections are not confirmed in any primary NASA document.
Voyager 1 also carries the memory of a serious scare. In late 2023, a fault in the spacecraft’s flight data subsystem garbled its telemetry for months before engineers devised a workaround. Any new anomaly at this stage would carry higher stakes with fewer backup systems available and a round-trip communication delay of nearly 45 hours. NASA’s broader mission pages acknowledge the risk in general terms but do not describe specific contingency plans for a two-instrument configuration.
Operational longevity depends on more than hardware. Running a spacecraft over 20 light-hours away requires dedicated staff, ground-station time on the Deep Space Network, and careful scheduling alongside other missions. None of the reviewed public documents mention a formal decision point at which Voyager 1 would shift from active observatory to passive beacon. That choice may ultimately hinge on NASA’s budget priorities as much as on the health of the spacecraft.
Voyager 2 offers a comparison
Voyager 1’s twin, Voyager 2, faces the same power decline but entered its current phase with a slightly different instrument lineup. As of early 2026, Voyager 2 still operates more science instruments than its sibling, partly because its RTGs have degraded at a marginally different rate and partly because of different engineering choices made over the decades. Both spacecraft are in interstellar space, but Voyager 2 crossed the heliopause later, in November 2018, and follows a different trajectory. The parallel missions give scientists two data points in a region where even one was once unimaginable.
A pair of sensors in the dark
The confirmed facts are stark enough on their own without speculation about exact shutdown dates. Nearly five decades after launch, Voyager 1 is shedding instruments one by one to keep a shrinking core alive. What the April 17 command leaves behind is a pair of sensors listening to the faint hum of interstellar space, a radio link still bridging billions of miles, and a mission team weighing each watt against one more measurement from the dark. For now, the data keeps coming. Every additional day of science at that distance is borrowed time, and the Voyager team knows exactly how to spend it.
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*This article was researched with the help of AI, with human editors creating the final content.
