Discoverer 1 was a test of the performance capabilities of the propulsion and guidance system of the booster and satellite. Launch took place from Vandenberg Air Force Base on a Thor-Agena A. After first stage burnout at 28529 km/hr the rocket coasted to orbital altitude where the second stage guidance system oriented the spacecraft by means of pneumatic nitrogen jets. The second stage engine ignited when the correct attitude was achieved, putting the spacecraft into a polar orbit where it remained until re-entry on 17 March 1959. Discoverer 1 became the first man-made object ever put into a polar orbit. Difficulty was encountered receiving signals after launch, but the satellite broadcast intermittently later in the flight. Discoverer 1 was a 5.73 m long, 1.52 m diameter cylindrical Agena A upper stage capped by a conical nosecone. The satellite casing was made of magnesium. Most of the 18 kg payload, consisting of communication and telemetry equipment, was housed in the nosecone. It included a high-frequency low-power beacon transmitter for tracking and a radar beacon transmitter with a transponder to receive command signals and allow long-range radar tracking. Fifteen telemetry channels (10 continuous and 5 commuted) were used to relay roughly 100 aspects of spacecraft performance. Unlike future Discoverer flights, this one did not carry a camera or film capsule. The Discoverer program was managed by the Advanced Research Projects Agency of the Department of Defense and the U.S. Air Force. The primary goal of the program was to develop a film-return photographic surveillance satellite to assess how rapidly the Soviet Union was producing long-range bombers and ballistic missiles and where they were being deployed, and to take photos over the Sino-Soviet bloc to replace the the U2 spyplanes. It was part of the secret Corona program which was also used to produce maps and charts for the Department of Defense and other US government mapping programs. The goal of the program was not revealed to the public at the time, it was presented as a program to orbit large satellites to test satellite subsystems and investigate the communication and environmental aspects of placing humans in space, including carrying biological packages for return to Earth from orbit. In all, 38 Discoverer satellites were launched by February 1962, although the satellite reconnaissance program continued until 1972 as the Corona project. The program documents were declassified in 1995.