Orbiting Vehicle 1-2 (also known as OV1-2), launched 5 October 1965, was the third, and first successful, satellite in the OV1 series of the United States Air Force's Orbiting Vehicle program. A radiation-measuring satellite designed to conduct research for the planned Manned Orbital Laboratory project, OV1-2 was the first American spacecraft to be placed into orbit on a western (retrograde to Earth's rotation) trajectory. The satellite stopped functioning in April 1967 after a series of technical problems starting two months after launch.