Discoverer 38 was an earth-orbiting satellite designed to improve satellite control, to test various space vehicle components, to continue evaluation of the Agena vehicle and recovery system, to conduct experiments in radio propagation, radiation effect, and instrumentation for nuclear explosion detection, and to eject and recover a reentry capsule. In addition to the usual Discoverer series instrumentation and telemetry, the payload included a horizon scanner, radiation measuring instruments, cosmic-ray monitors, magnetometers, an impedance probe, and a radio propagation probe operating on 20.005 and 40 MHz. The 136 kg reentry capsule carried (1) a device to measure the time history of radiation, (2) a radiation shielding experiment, (3) a biological package containing human and animal tissues, spores, molds, and aglae, (4) a nuclear track plate, (5) dosimeters, (6) lead radiation experiments, and (7) samples of silicon, iron, bismuth, gold, magnesium, nickel, and titanium to determine the effects of their exposure to the space environment. Also included were two total-energy detectors having thresholds of 4.5 and 33 KeV for electrons. The reentry capsule successfully separated from the Agena B after 65 orbits, decelerated, reentered the atmosphere, and was recovered in mid-air. The Agena B remainded in orbit and continued to transmit data until it reentered the atmosphere and burned up on March 21, 1962.