In the vast expanse of space, a forgotten satellite, Transit 5B-5, continues its silent vigil, a testament to the ingenuity of its creators and the enduring nature of technology. Launched in 1964 by the US Navy, this small yet remarkable satellite has outlived its intended lifespan by decades, still transmitting and being used by amateur radio operators worldwide. This is a story of resilience, innovation, and the unexpected ways in which technology can persist and inspire.
What makes Transit 5B-5 truly remarkable is its power source. Instead of relying on chemical batteries or solar panels, which degrade quickly, the satellite is equipped with a SNAP-3 radioisotope thermoelectric generator, a small nuclear power source that converts the heat from decaying plutonium-238 into electricity. Plutonium-238 has a half-life of about 88 years, meaning that the SNAP-3 RTG launched in 1964 should still be producing around 65% of its original power output today. This is a testament to the foresight and engineering prowess of the early space program.
The radio transmitter on board doesn't need much power to keep broadcasting a signal at around 136.65 MHz. This low-frequency telemetry beacon has never stopped, against all reasonable expectations. There are no moving parts to wear out, no fuel to run dry, and no on-board computer to crash. The satellite is essentially a power source connected to a transmitter, drifting along in an orbit that doesn't require maintenance. It just works, and it has worked for sixty-one years.
If you tune the right radio receiver to the right frequency at the right time, you can hear it pass overhead. Amateur radio operators describe the signal as a faint, rhythmic warble, telemetry data encoded as audio tones. With the right software, those tones can be decoded into actual numbers: information about the satellite's onboard systems, its temperature, and the state of its hardware. This is a living museum of engineering, phoning home from the edge of space.
The amateur SDR (software-defined radio) community treats these old satellites as a kind of living museum. Receiving Transit 5B-5's signal requires no special permission, no military access, and no expensive equipment — just a basic SDR dongle costing about thirty dollars, an antenna, and patience. The Navy is no longer involved in any of this, and the institutional memory of how Transit worked has been preserved largely by hobbyists.
A Canadian amateur radio operator named Scott Tilley has become something of a folk legend in this niche. In 2018, he discovered IMAGE, a NASA satellite that had been declared lost in 2005, and in 2020, during pandemic lockdown, he tracked down LES-5, a US military satellite launched in 1967 that everyone had assumed was dead. Tilley calls these 'zombie satellites' — spacecraft that were supposed to be silent decades ago but are still, somehow, broadcasting. When NPR asked him in 2020 which was the oldest he'd ever heard, he didn't hesitate. 'The oldest one I've seen is Transit 5B-5,' he said. 'A nuclear-powered U.S. Navy navigation satellite that still circles the Earth in a polar orbit, long forgotten by all but a few amateurs interested in hearing it sing as it passes overhead.'
What makes this story particularly fascinating is the contrast between the intentions of the engineers who designed Transit 5B-5 and the unexpected ways in which technology can outlive its original purpose. The engineers who designed Transit 5B-5 in the early 1960s could not possibly have imagined that ordinary people would, in 2026, be listening to it from their backyards with a thirty-dollar device. They couldn't have imagined the device, they couldn't have imagined the people. This is the opposite of how we usually think about technology. We expect our devices to fail before they're obsolete. We replace phones every two years. The cycle of planned obsolescence has trained us to think of hardware as something that wears out predictably.
Transit 5B-5 was built by people who were not thinking that way. They were thinking: the cost of putting this thing in space is enormous; build it to last. They overengineered it. They gave it a power source that would outlive its operators. They built it for ten years and got sixty. This is a powerful reminder of the importance of long-term thinking and the value of building things to last.
Somewhere overhead, right now, a small metal object the size of a microwave oven is moving at 17,500 miles per hour, listening to a heater fed by slowly decaying plutonium, and broadcasting a signal that nobody officially needs but that several people, in several countries, are still patiently catching. The Navy walked away from it nearly thirty years ago, and it hasn't noticed. This is a quiet, beautiful, and enduring testament to the power of human ingenuity and the unexpected ways in which technology can persist and inspire.
