When cell service disappears, a rescue beacon developed by NASA can summon help from space

Back in the early 1990s, when I was a reporter for The Recorder newspaper in Calvert County, Maryland, one of the more unusual parts of covering the cops, courts and county government beat was occasionally riding along on water rescue calls into the Chesapeake Bay. Most of those trips were aboard boats operated by local police or firefighters, although I sometimes went out with the Maryland Department of Natural Resources too. The town of North Beach also had a group of semi-official volunteers from the oyster boat community who would race out to help fellow boaters whenever someone got into trouble.

Cellphones existed at the time, but they were expensive, bulky and far from universal. Only some of the larger boats, including many commercial oyster boats, carried them, and signals could disappear once a vessel traveled far enough into the bay. Marine radios were much more reliable, assuming someone had enough time to use one when needed.

I remember covering one rescue involving a large fishing vessel that rolled over in rough seas and broke apart. I interviewed the captain afterward, following his successful rescue, and he told me he barely had time to radio a distress call before the vessel went under in less than a minute.

In some ways, he was lucky. He had enough time to make the call, and as a seasoned captain, he knew exactly what to do. Not everyone facing a sudden emergency on the water will have either advantage.

That memory came back to me while reading a recent NASA account of another maritime rescue, this one involving five friends participating in a fishing competition about 40 miles off the Mississippi Gulf Coast over Memorial Day weekend in 2024.

According to NASA, the group was checking its sonar in relatively calm water when their boat suddenly began sinking. About 30 seconds later, it was gone and all five men were in the water.

Easton Barrett had the group’s only mobile phone, but there was no cell service that far offshore. He recorded a brief farewell and planned to put the phone inside a cooler in the hope that someone might eventually recover it.

Fortunately, one member of the group had suggested bringing along a personal locator beacon, or PLB, at the last minute. The device ended up sitting on the console instead of being stored away, making it easy to grab as the boat disappeared beneath them.

The fuller account published by NASA’s Spinoff program makes what happened next sound even more harrowing. The group clung to coolers and treaded water, dumping about 200 pounds of bait to make one cooler more buoyant. NASA says they also had three close encounters with wildlife, likely sharks and eels. But while they were trying to stay afloat and fending off sharks, their PLB had already done something their cellphone could not. It had called for help.

When activated, the beacon transmitted a distress signal on the reserved 406 MHz band to satellites carrying Search and Rescue Satellite-Aided Tracking technology, better known as SARSAT. The system relayed location information to a ground station, where it could be passed through a mission control center to rescuers.

More than four hours after their boat sank, the U.S. Coast Guard found all five men alive.

The technology behind that rescue has a long government history. Congress initiated development of a satellite-based locator system following a 1972 plane crash in a remote area of Alaska that searchers struggled to locate using the technology available at the time. NASA subsequently helped develop technical specifications for the satellite and ground systems with U.S., Canadian and French partners.

U.S. SARSAT operations began in 1982. Three years later, the effort joined with a similar Soviet-developed system known as COSPAS, a Russian acronym meaning “Space System for the Search of Vessels in Distress,” to form the international Cospas-Sarsat program.

Today, the system includes 62 operational satellites and 45 participating nations, according to NASA. In the United States, NOAA operates the SARSAT system and its mission control center while the Coast Guard manages the program and handles maritime rescues. The Air Force coordinates inland search-and-rescue responses, often working with local authorities, while NASA continues to work on developing even better rescue technologies.

The mechanics of how everything works are relatively straightforward. Emergency beacons transmit distress signals. Satellites detect those signals and pass them to receiving stations on the ground. Mission control centers then route alerts to the appropriate rescue coordination centers.

Different emergencies use different types of 406 MHz beacons. Personal locator beacons are designed for individuals, emergency position-indicating radio beacons are commonly used aboard vessels and emergency locator transmitters are used by aircraft.

The technology has also improved considerably since the system first went operational. Modern beacons can transmit GPS location information, greatly narrowing the area rescuers need to search. NASA says satellite emergency notifications can update about every 52 seconds.

Some newer beacons also support what is known as return-link technology. Instead of the distress signal traveling only one way, the beacon can receive confirmation that the satellite system received it. For someone stranded far from help, that simple acknowledgment can provide something earlier generations of emergency beacons could not: confirmation that somebody, somewhere, knows they are in trouble.

The system continues to rack up rescues. As of Sept. 11, NOAA reported that SARSAT had helped rescue 197 people in the United States during 2026. That included 111 people in maritime emergencies, 28 involved in aviation incidents and 58 rescued following terrestrial personal locator beacon activations.

Since U.S. operations began in 1982, NOAA says the system has contributed to the rescue of 11,368 people in this country. Its current National Environmental Satellite, Data, and Information Service page credits the international system with more than 64,000 rescues worldwide.

NOAA also maintains an interactive map showing recent SARSAT rescue incidents around the country, with historical layers going back to 2016. The individual points offer a striking visual reminder that the system is not simply an old government technology still operating in the background. People continue to depend on it every year.

Barrett is now among those advocating for emergency beacons after surviving because someone thought to bring one aboard.

“Ever since, I have tried to teach others about safety on the water and in the outdoors by using a PLB,” Barrett told NASA. “If that will save one life, it’s worth the effort.”

Back when I was covering water rescues on the Chesapeake Bay, getting help could depend on a captain having enough time to reach a radio and transmit a distress call before the situation became catastrophic. That basic problem has not changed. Boats can still sink extraordinarily fast, communications can still fail and people in the water can still become almost impossible to see.

But what has changed is how far that call for help can travel. Today, even when a cellphone has no signal and a boat disappears in seconds, a small emergency beacon can send a distress call into space and start bringing rescuers toward people who might otherwise never be found.

John Breeden II is an award-winning journalist and reviewer with over 20 years of experience covering technology. He is the CEO of the Tech Writers Bureau, a group that creates technological thought leadership content for organizations of all sizes. Twitter: @LabGuys