Nimbus 3 was launched on April 14, 1969, by a Thor-Agena rocket from Vandenberg Air Force Base, Lompoc, CA.

The polar-orbiting spacecraft consisted of three major elements: (1) a sensory ring, (2) solar paddles, and (3) the control system housing.

The solar paddles and the control system housing were connected to the sensory ring by a truss structure, giving the satellite the appearance of an ocean buoy.

An H-frame structure mounted within the center of the torus provided support for the larger experiments and tape recorders.

Primary experiments consisted of: (1) a satellite infrared spectrometer (SIRS), for determining the vertical temperature profiles of the atmosphere; (2) an infrared interferometer spectrometer (IRIS), for measuring the emission spectra of the Earth-atmosphere system; (3) both high- and medium-resolution infrared radiometers (HRIR/MRIR), for yielding information on the distribution and intensity of infrared radiation emitted and reflected by the Earth and its atmosphere; (4) a monitor of ultraviolet solar energy (MUSE), for detecting solar UV radiation; (5) an image dissector camera system (IDCS), for providing daytime cloud-cover pictures in both real-time mode, using the real time transmission system (RTTS), and tape recorder mode, using the high data rate storage system; (6) a radioisotope thermoelectric generator (RTG), SNAP-19, to assess the operational capability of radioisotope power for space applications; and (7) an interrogation, recording and location system (IRLS) experiment, designed to locate, interrogate, record, and retransmit meteorological and geophysical data from remote collection stations.