Beginning in the 1960s, the United States Navy began developing a communications and navigation satellite program to meet the needs of ships at sea and submarines. One result of this program was the Transit satellite series, designed and built to Navy specifications by the Johns Hopkins University Applied Physics Laboratory in Maryland.
Submarines received radio signals from a Transit satellite, whose orbit was known to great accuracy, as it passed overhead. The change in frequency of the signal due to the Doppler effect told the submarine that the satellite was directly overhead. The submarine commander could establish a position without having to surface and take reading on stars--the traditional method of navigation, but a risky one for a submarine.
The Transit V-A satellite is an operational backup to the Transit series and was donated to NASM by the JHU Applied Physics Lab in late 1984.