Wednesday, April 21, 2021

Rescue 21 – Taking the ‘Search’ Out of Search and Rescue


A graphic representation of Rescue 21 locations. Submitted

A graphic representation of Rescue 21 locations. Submitted

Your offshore fishing trip has turned into a life and death situation. Your fishing buddy is experiencing chest pains and you need medical help. You quickly use your VHF-FM marine radio to call the Coast Guard on channel 16. What you may not realize is that the moment you initiate that mayday call, the Coast Guard’s Rescue 21 system is locking in on your signal. Even if you don’t know exactly where you are, the Rescue 21 hardware will find you. Rescue 21’s design only requires the system to receive a one-second transmission of a one-watt transmission from a two-meter height at 20 nautical miles (nm). Basically, this would be you on your boat with a handheld portable radio.



The system immediately records and digitizes your message. Their 300 foot plus radio towers contain direction-finding capabilities and calculate the origin of your radio signal. This creates a “line of bearing” (LOB). Automatically, your audio message and LOB are forwarded to the nearest Ground Center. There, appropriate resources are deployed immediately to your location. This can be planes, boats, or helicopters. Rescue can be started while you are still making your call.

The LOB is just that, a line pointing in the direction of your boat. But where on that line are you exactly? The good news is that in many instances, a second Rescue 21 tower has picked up your signal, and between the two they can pinpoint your location.

Photo by Public Affairs Specialist Third Class Luke Pinneo

Photo by Public Affairs Specialist Third Class Luke Pinneo

How well does this work? Well, General

Dynamics, the company that designed the system, reported that as of January 15, 2016, 85,167 search and rescue (SAR) cases had been conducted. This equates an average of 1,074 SAR cases per month. Considering that Rescue 21’s first rescue was in November of 2005 and Rescue 21 reached Initial Operating Capability (IOC) in December 2005, I would say it is working very well. During the ensuing years, Rescue 21 installations were continually being added, and now it covers 41,871 miles of coastline along the entire Atlantic, Pacific and Gulf coasts of the continental United States as well as along the shores of the Great Lakes, Hawaii, Puerto Rico, the U.S. Virgin Islands,

Guam and the Northern Marianas Islands. When completed the system will cover more than 95,000 miles of coastline, navigable rivers and waterways. Conditional acceptance and operation on the Mississippi and Ohio Rivers was completed this past June. Installations are in progress now in Alaska, with full implementation planned for the end of this year.

Can you improve this system? Absolutely. Since 1999, any newly designed marine VHF radios are required to include Digital Selective Calling (DSC). DSC is used to transmit and receive distress signals and to relay emergency and safety calls and automatic alerts. DSC enabled radios allow you to send a mayday message by pressing a single button. VHF radios equipped with DSC must have a Maritime Mobile Service Identity (MMSI) number to function. You must register your radio’s MMSI. You can easily register your MMSI with BoatUS or SeaTow. The MMSI nine-digit number can be thought of as the phone number for your boat. With the MMSI registered, activation of the DSC button transmits all the information about you and your boat. That allows you to spend more time helping your friend.

Can you make it even better? You sure can. If you have a GPS onboard your boat, connecting the GPS to the VHF radio will send the latitude and longitude along with all the information in the MMSI database. Pushing a single button gives the Coast Guard your information and your location and that takes the search out of search and rescue. Many new VHF radios come equipped with an internal GPS that eliminates the need to connect your chart plotter to the radio.

One additional benefit of the Rescue 21 system is that it can pinpoint mayday call hoaxes and save deployment of resources.

Improvements and enhancements to the Rescue 21 system are being planned. The Coast Guard has developed mobile, deployable towers and electronics packages that can help restore communications after natural disasters. Rescue 21 installations demonstrated “particular robustness during Hurricane Sandy,” Deputy Project Manager Eugene Lockhart said, helping the Coast Guard coordinate the interagency command, control and communications essential to disaster recovery.

The planners are looking at ways to consolidate infrastructure to reduce costs through extensive use of new technology, perhaps coordinating calls from central locations, thus reducing redundant regional command centers.

For more information about registering your DSC-equipped VHF radio’s MMSI, visit BoatUS’s website, mmsi, or SeaTow’s website,

For more information about safe boating courses, contact Joe Riccio at 239-384-7416 or email To schedule a free Vessel Safety Check contact John Moyer at 239-248-7078 or or call the Coast Guard Auxiliary Station – Flotilla 95 at 239-394-5911. Interested in joining Flotilla 95, USCG Auxiliary? Call Bob Shmihluk at 215-694-3305.

Keith Wohltman retired to Marco Island from New Jersey, where he spent decades on the water. He joined the U.S. Coast Guard Auxiliary to help make boating safer around Marco and the 10,000 Islands. He has served as the Flotilla Commander and a Coxswain and is currently the Public Affairs Staff Officer for Marco Island’s Flotilla 95.

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