AGTR

Technical research ships were used by the United States Navy during the 1960s to gather intelligence by monitoring, recording and analyzing wireless electronic communications of nations in various parts of the world. At the time these ships were active, the mission of the ships was covert and discussion of the true mission was prohibited ("classified information"). The mission of the ships was publicly given as conducting research into atmospheric and communications phenomena. However, the true mission was more or less an open secret and the ships were commonly referred to as "spy ships".

These ships carried a crew of U.S. Navy personnel whose specialty was intercepting wireless electronic communications and gathering intelligence from those communications (signals intelligence, communications intelligence, and electronic signals intelligence (SIGINT)). In the 1960s those personnel had a U.S. Navy rating of Communications Technician (later changed to Cryptologic Technician), or CT.

In order to transmit intelligence information that had been gathered back to United States for further processing and analysis, these ships had a special system named Technical Research Ship Special Communications, or TRSSCOM (pronounced tress-com). This Earth-Moon-Earth (EME) communications system used a special gyroscope-stabilized 16-foot parabolic antenna, which can be seen aft of the main superstructure in the accompanying photographs of the Belmont and Liberty. Radio signals were transmitted toward the moon, where they would bounce back toward the Earth and be received by a large 84-foot parabolic antenna at a Naval Communications Station in Cheltenham, Maryland (near Washington, D.C.) or Wahiawa, Hawaii. Communications could occur only when the moon was visible simultaneously at the ship's location and in Cheltenham or Wahiawa. The gyro stabilization of the antenna kept the antenna pointed at the moon while the ship rolled and pitched on the surface of the ocean.

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Wikipedia