NASA Powers Down Systems on Voyager 1 as Spacecraft Continues Interstellar Journey

On April 17, 2026, engineers at NASA's Jet Propulsion Laboratory in Pasadena, California, sent a command into the void. Traveling at the speed of light, it took more than 23 hours to reach its target: Voyager 1, now over 15 billion miles from Earth [1]. The command instructed the spacecraft to shut down its Low-energy Charged Particles experiment, an instrument that had been measuring ions, electrons, and cosmic rays almost without interruption since the probe launched on September 5, 1977 [1].

The shutdown was not a surprise. It was the latest in a series of calculated sacrifices designed to keep the most distant human-made object functioning for as long as possible. But it marks a threshold. Voyager 1 now operates with just two science instruments — a plasma wave detector and a magnetometer [1]. The spacecraft that once carried ten instrument suites past Jupiter and Saturn, that first detected the boundary where our sun's influence ends and interstellar space begins, is running on fumes.

"While shutting down a science instrument is not anybody's preference, it is the best option available," said Kareem Badaruddin, Voyager mission manager at JPL [2].

The Power Problem: 4 Watts Per Year, Every Year

Voyager 1 carries no solar panels and no rechargeable batteries. Its sole power source is a set of three radioisotope thermoelectric generators (RTGs) — devices that convert heat from the natural decay of plutonium-238 into electricity [3]. At launch in 1977, the RTGs produced approximately 470 watts of electrical power [4]. Nearly five decades later, that output has dropped to roughly 206 watts [4].

Source: NASA JPL / Wikipedia

Data as of Apr 17, 2026CSV

The decline is driven by two factors: the 87.7-year half-life of plutonium-238 and the gradual degradation of the silicon-germanium thermocouples that convert heat to electricity [4]. Together, these mechanisms drain about 4 watts from the power budget each year [1]. The thermocouple degradation is the harder variable to predict — the radioactive decay follows a clean exponential curve, but the thermocouples age in less predictable ways after decades of exposure to radiation and thermal stress [4].

The practical consequence is stark. Each watt lost is a watt that can no longer power a heater, a science instrument, or the 23-watt radio transmitter that sends data back to Earth at 160 bits per second — roughly the speed of a dial-up modem from the early 1990s [5]. Engineers recently reported that power margins had become "razor thin," with the spacecraft approaching automatic shutdown thresholds during a routine maneuver in February 2026 [2].

At the current rate of decline, NASA projects the RTGs will produce enough power to return at least engineering data until approximately 2036, with at least one science instrument potentially operational into the early 2030s [4][6].

A History of Letting Go

The April 2026 LECP shutdown is only the most recent in a long sequence of instrument deactivations stretching back decades. Each one represented a deliberate triage — a decision about which measurements mattered most, made jointly by the Voyager science and engineering teams [5].

Source: NASA JPL

Data as of Apr 17, 2026CSV

Voyager 1 launched with ten science instrument suites. The cameras were among the first to go, switched off after the planetary encounters ended, since there was nothing nearby to photograph [5]. Heaters for various subsystems followed. The Plasma Science Instrument, which had stopped working correctly during the Saturn encounter in 1980, was formally powered down in 2007 [7].

The pace of shutdowns has accelerated recently as power margins tightened:

• February 25, 2025: NASA shut down Voyager 1's Cosmic Ray Subsystem, a suite of three telescopes that measured cosmic rays, protons, and their energy flux [6].
• March 24, 2025: Voyager 2's Low-Energy Charged Particle Instrument was deactivated [6].
• October 2024: Voyager 2's Plasma Science experiment was turned off [7].
• April 17, 2026: Voyager 1's LECP was powered down [1].

One detail of the LECP shutdown is notable: a small motor that spins the sensor to scan in all directions, drawing only 0.5 watts, was left running [1]. The reasoning is pragmatic — keeping the motor operational preserves the possibility of reactivating the instrument if engineers find additional power through a planned initiative they call "the Big Bang," a simultaneous shutdown and replacement of multiple powered systems with lower-power alternatives. The plan is being tested on Voyager 2 first, in May–June 2026, with potential implementation on Voyager 1 no sooner than July 2026 [1].

Voyager 2's situation roughly mirrors its twin's. After its own recent shutdowns, it retains three active science instruments: a magnetometer, a plasma wave instrument, and the Cosmic Ray Subsystem, which is expected to be deactivated sometime in 2026 [6].

What Voyager 1 Alone Can Tell Us

On August 25, 2012, Voyager 1 crossed the heliopause — the boundary where the solar wind, a stream of charged particles flowing outward from the sun, gives way to the interstellar medium, the thin gas and dust that fills the space between stars [8]. It was the first human-made object to enter interstellar space, and it remains one of only two, alongside Voyager 2, which crossed in November 2018 [8].

The data from this region is singular. When Voyager 1 crossed the heliopause, its instruments detected a sharp jump in cosmic ray abundance — particles originating from supernova explosions far beyond our solar system increased by a factor of three [8]. The plasma wave instrument detected electron oscillations at a frequency of about 2.6 kilohertz, corresponding to an electron density of approximately 0.08 particles per cubic centimeter — close to theoretical predictions for the interstellar medium but never before measured directly [9].

Perhaps most unexpectedly, Voyager 1 discovered time-varying anisotropies in galactic cosmic rays — directional patterns in particle flow that change over time, characterized by intensity reductions in particles moving perpendicular to the local magnetic field [10]. These observations challenge existing models of how cosmic rays propagate through the galaxy and how the heliosphere interacts with its surrounding environment.

The two remaining instruments — the magnetometer and the plasma wave detector — continue to provide measurements of the interstellar magnetic field and plasma density. These are the instruments the science team judged most valuable to keep running [6]. The magnetometer tracks the strength and direction of magnetic fields in interstellar space, while the plasma wave subsystem detects electron density oscillations that serve as a proxy for the density of the surrounding medium.

Source: OpenAlex

Data as of Jan 1, 2026CSV

Academic research tied to Voyager's interstellar measurements has produced over 1,187 published papers, with a peak of 185 in 2023 [11]. The science output remains active, with 50 papers published so far in 2026.

Once Voyager 1 goes silent, a specific set of measurements will become unavailable. No other spacecraft is positioned to measure the properties of the very local interstellar medium — the magnetic field strength, the cosmic ray flux at low energies filtered out by the heliosphere, or the plasma density outside the sun's sphere of influence. These are measurements that ground-based and near-Earth telescopes cannot replicate, because the heliosphere itself blocks or distorts the signals [8].

The Successor Gap

The Johns Hopkins Applied Physics Laboratory has developed a concept for an Interstellar Probe — a spacecraft designed to travel beyond the heliosphere at roughly 7 astronomical units per year, significantly faster than Voyager's current speed [12]. The baseline launch window is 2036–2041, using a Space Launch System rocket with additional boosters and a Jupiter gravity assist [12]. The mission would have a planned duration of at least 50 years, potentially exceeding 100 years — the longest planned duration of any NASA mission [12].

But the Interstellar Probe remains a concept study, not a funded program. NASA's heliophysics division has provided $6.5 million across three years to develop the science and engineering details [12]. Even if approved and launched on schedule in 2036, the probe would not reach the heliopause for roughly 15 years, meaning interstellar in-situ measurements would not resume until the 2050s at the earliest.

That creates a measurement gap of at least two decades — and likely longer — during which no spacecraft will be sampling the interstellar medium. The scientific questions that Voyager has opened but not resolved, including the structure of the heliopause boundary, the nature of cosmic ray transport in the local interstellar medium, and the properties of the interstellar magnetic field at scales smaller than what remote sensing can detect, will remain unanswered during that interval [8][12].

The $5 Million Question: Is It Worth It?

The Voyager program's annual operating cost is approximately $5 million per year for both spacecraft — a figure that has held roughly steady since the Voyager Interstellar Mission began after the Neptune encounter in 1989 [5][3]. The original primary mission cost less than $1 billion in 1970s dollars, equivalent to over $4 billion adjusted for inflation [3]. By any measure, the extended mission has been extraordinarily cost-efficient: $5 million per year for data that no other instrument, ground-based or orbital, can provide.

For context, the New Horizons mission to Pluto and the Kuiper Belt cost approximately $780 million through its primary mission [3]. A single year of operating the James Webb Space Telescope costs roughly $170 million [3]. The proposed Interstellar Probe, if built, would likely cost several billion dollars over its lifetime.

The case for continued Voyager funding rests on a straightforward asymmetry. As the SpaceDaily analysis described it, mission leaders annually justify continuation by making "the cost of cancellation — losing the only instruments in interstellar space — obviously greater than the cost of continuation" [5].

Still, Voyager does consume resources beyond its dollar budget. The Deep Space Network (DSN), the global array of radio antennas that communicates with all deep-space missions, is significantly oversubscribed. A 2023 Physics Today analysis found the DSN was up to 40% oversubscribed, with excess demand projected to reach 50% by the 2030s [13]. Over recent years, missions including Voyager 2 and New Horizons each received between 8,500 and 15,000 fewer tracking hours than requested [13]. The DSN Aperture Enhancement Project, meant to expand capacity, is nearly five years behind schedule, with costs rising from $419 million to $706 million [13].

Legacy missions like Voyager require some of the network's largest antennas to capture their faint signals [13]. Every hour of DSN time allocated to Voyager is an hour unavailable to Mars rovers, the James Webb Space Telescope, or crewed Artemis missions — which, for safety reasons, take network precedence [13]. Whether Voyager's marginal science return justifies that antenna time is a question without a clean answer. No planetary scientist has publicly called for Voyager's cancellation, but the structural pressure on DSN resources is real and growing.

The Team That Keeps the Lights On

The JPL team managing Voyager has undergone complete personnel turnover — twice — since the mission launched [5]. The current team spans from NASA retirees in their 80s, who consult on subsystems they helped design, to engineers so young that their parents were not born when the probes launched [5]. The mission has persisted across nine presidential administrations and countless NASA budget cycles [5].

Institutional knowledge is a persistent concern. The spacecraft's onboard computers use architecture from the early 1970s. There are no replacement parts, no simulators that perfectly replicate the flight hardware, and no way to physically access the spacecraft for repairs. When a fault occurs — as it did in 2024 when Voyager 1 began sending garbled data due to a corrupted memory chip — the fix must be devised from the ground and uploaded bit by bit across billions of miles [5][14].

The team has developed systems to capture the knowledge of retiring engineers before it is lost [5]. But the challenge is inherent to operating hardware that predates the personal computer. The programming language, the command protocols, and the electrical engineering are artifacts of an era that most working engineers have never encountered. As the mission approaches its final years, the question is not only whether the spacecraft can keep running, but whether anyone will remain who knows how to talk to it.

The Timeline Ahead

The remaining operational life of Voyager 1 can be sketched in approximate terms:

• 2026: Two science instruments remain active (magnetometer, plasma wave subsystem). The "Big Bang" power conservation initiative may buy additional months. Voyager 1 will reach one light-day from Earth — 16.1 billion miles — around November 2026 [15].
• 2027–2029: Additional instrument shutdowns are likely as power continues to decline at approximately 4 watts per year. Engineers will prioritize the magnetometer and plasma wave subsystem for as long as possible [6].
• Early 2030s: The last science instrument is expected to shut down. Engineering data — spacecraft health, position — may continue [4][6].
• ~2036: RTG output may fall below the threshold needed to power even basic engineering telemetry [4].

Once power drops below the level needed to operate the 23-watt transmitter, Voyager 1 will go permanently silent. The spacecraft will not be detectable from Earth after that point — without active transmission, there is no signal to receive. There is no passive beacon, no reflective surface large enough to track by radar at a distance of more than 15 billion miles [1].

Voyager 1 will then continue on its trajectory through interstellar space, carrying the Golden Record — a 12-inch gold-plated phonograph record containing sounds and images of Earth — toward the constellation Ophiuchus. It will pass within 1.6 light-years of the star Gliese 445 in roughly 40,000 years [4]. By then, the plutonium will have long since decayed, the thermocouples will have degraded beyond any function, and the spacecraft will drift in silence through a galaxy that has no idea it is there.

But that is 40,000 years away. Right now, two instruments are still listening. The data is still coming in at 160 bits per second, 23 hours per transmission. And at JPL, a small team is still finding ways to keep a 49-year-old machine alive — one watt at a time.