Payload
The UHF payload provided one 500 kHz wide-band channel and two 25 kHz narrow-band channels.
The UHF payload on Marisat was designed as a "gapfiller" to support the U.S. Navy. The U.S. Navy experienced a complete failure of TACSAT-1 over the Pacific Ocean in December 1972. UHF channels on Lincoln Labs Experimental Satellite LES-6 were also being used over the Atlantic Ocean, but this satellite was expected to have an end-of-life (EOL) of September 1973. This left the U.S. Navy with a potential "gap" in UHF coverage for several years until the first FLTSATCOM satellite would be available in December 1978. The U.S. Navy contracted with COMSAT in 1973 for UHF capability over the Atlantic and Pacific ocean regions (AOR and POR), and later extended the contract for coverage of the Indian Ocean region (IOR).