36 Proceedings | Vol. 83, No. 1 Positively Influencing Boaters Importance of Maritime Mobile Service Identities with Electronic Signaling Equipment by Joe heRSey Electronics Engineer JOECEL Engineering & Consulting LLC bRian m. mooRe Recreational Boating Safety Specialist Boating Safety Division U.S. Coast Guard D uring the evening of June 1, 2016, Coast Guard Sector Maryland-National Capital Region watch standers in Baltimore, Maryland, received a VHF digital selective calling (DSC) distress alert on their Rescue 211 radio console. A search of the service’s Marine Information for Safety and Law Enforcement (MISLE) database showed the Maritime Mobile Service Identity (MMSI), was associated with the Karen N. The alert from the Chesapeake Bay Foundation’s 40-foot alu- minum shallow-draft, water jet-powered vessel put it in the Chesapeake Bay off Maryland’s Bloodsworth Island. The alert was followed by a distress call on VHF channel 16, “Mayday, mayday, mayday. This is the motor vessel Karen N. We have sunk off Bloodsworth Island.” Then, silence. The Coast Guard issued an urgent marine information broadcast, notified the Maryland State Police, and launched their own rescue boat. Jeremy Shockley, the owner of the boat Ka-Ree heard the alert while docked on the Bay. Knowing the waters well, he took a small crew to the location and rescued 23 people—including 14 children—from the water,2 all of which were wearing life preservers, greatly enhanc- ing their chances of survival. Mr. Shockley received a Governor’s Citation for his efforts. The captain and passengers on the Karen N. were well- prepared for an emergency, but that’s not always the case. In 2021, the Coast Guard reported to the International Maritime Organization (IMO) that, in 2019, only 24% of the 152 search and rescue (SAR) cases originating via VHF DSC alert yielded enough information to provide a location allowing for the dispatch of SAR resources. Only 39.9% of registered identities from these alerts were sufficient to identify the vessel or person sending it. Taken together, 45.6% of these distress alerts had neither position nor identity information and, unless there was some sort of follow-on voice communications, the only action the Coast Guard could take was to acknowledge it! Acknowledging a DSC alert terminates the very loud, irritating alarm sounding on nearby vessels’ radios. The 152 DSC-initiated SAR cases in 2019 represented just 12% of all Coast Guard-documented SAR cases received by all radio communications documented by the Coast Guard.3 The Origins of DSC, the 911 of the Maritime Mobile Radio Service When the IMO and International Telecommunications Union (ITU) began planning for the replacement of Morse telegraphy radio systems aboard ships 50 years ago, all maritime radio safety technology came under review. The launch of the first maritime mobile satellite by Commercial Satellite Corporation, later transferred to a newly created, IMO-recognized intergovernmen- tal organization called Inmarsat, drove this review. All shipboard maritime radio systems existing at that time, including Morse telegraphy, radiotelephony, radio direction finders, and emergency position-indicating radio beacons were affected. These new and redesigned maritime radio systems were designated as the Global Maritime Distress and Safety System (GMDSS) and man- dated for shipping under amendments to the Safety of Life at Sea Convention that came into force from 1993 to 1999. These changes affected shore-based radio systems as well, including worldwide areas of responsibility for navigational and meteorological warnings and radiote- lephony coast stations which later included the Coast Guard’s own Rescue 21 system. During the development of the radiotelephony por- tions of the GMDSS, the ITU adopted a 50-year-old, 10-bit symbol, error-detecting digital selective calling technol- ogy specified for aeronautical use but never adopted. These DSC symbols contained data like the type and call priority, the radio channel being called, and the identity of the radios making and receiving the call. Obtaining automated radio checks or testing the proper operation of other DSC-equipped radios is accomplished by DSC test call and position report request function. It included
