Discoverer 15 was an earth-orbiting satellite designed to test spacecraft engineering techniques and to attempt deceleration, reentry through the atmosphere, and recovery from the sea of an instrument package. Instrumentation was identical to that of Discoverer 13, with the addition of external lights (approximately a sixth to seventh magnitude star) for optical tracking from ground camera stations. The cylindrical Agena A stage carried a telemetry system, a tape recorder, receivers for command signals from the ground, a horizon scanner, and a 120-lb recovery capsule that contained biological specimens. The capsule was a bowl-shaped configuration 33 in. in diameter and 27 in. deep. A conical afterbody increased the total length to about 40 in. A Thiokol retrorocket was mounted at the end of the afterbody to decelerate the capsule out of orbit. A 40-lb monitoring system was included in the capsule to report on selected events, such as firing of the retrorocket and jettisioning of the heat shield. The recovery capsule was ejected, but retrieval was not possible due to inclement weather conditions. The Agena stage reentered the atmosphere and burned up on October 17, 1960.