Trust, but verify as a signature phrase by Reagan, who subsequently used it frequently when discussing U.S. relations with the Soviet Union. Using proverbs that the Russians could relate to may have helped relations between the two leaders. After Reagan used the phrase to emphasize "the extensive verification procedures that would enable both sides to monitor compliance with the treaty", at the signing of the INF Treaty, on 8 December 1987, his counterpart General Secretary Mikhail Gorbachev responded, "You repeat that at every meeting," to which Reagan answered, "I like it." While Reagan quoted Russian proverbs, Mr. Gorbachev quoted Ralph Waldo Emerson, who
US signals intelligence in the Cold War units in border areas." In the fifties, only aircraft platforms could obtain SIGINT over the USSR. A Soviet source pointed out that aircraft were of limited usefulness, due to being vulnerable to fighters and antiaircraft weapons. (Translator's estimate: in the period 1950-1969, about 15 US and NATO reconnaissance aircraft were shot down over the USSR, China, the GDR and Cuba). The US, therefore, undertook the WS-117L reconnaissance satellite project, approved by President Dwight D. Eisenhower in 1954, within which was a signal intercept subsystem under Project PIONEER FERRET. By 1959, WS-117L had split into three programs: The first experimental ELINT