was asymmetrical once its booms were extended, OV3-2 maintained its attitude in orbit with a precession damper. The spacecraft was spin stabilized at 8 revolutions per minute (rpm) A sun sensor, as well as an onboard tri-axial magnetnometer, gave information on the satellite's aspect (facing), its spin rate, and rate of precession. Design life-span was one year. Operations The OV3 program ultimately comprised 6 missions, five of them successful. The last (OV3-6) flew on 4 December 1967. The OV3 program was terminated following OV3-6 in favor of the cheaper OV1 program. Significant Results OV3-1 had a near polar orbit and returned useful data on the energy and distribution of electrons in the auroral regions. Data returned by OV3-4 helped prove and refine theoretical models of radiation dosage an astronaut would receive at orbital altitudes. OV3-3 VLF receiver data determined the location of the plasmapause (the outer boundary of the Earth's inner magnetosphere). OV3-2 observed ambient charged particle variations before, during, and after the 12 November 1966 South American solar eclipse. OV3-2 also conducted ionospheric and aurora research in orbit in conjunction with AFCRL KC-135 aircraft flying underneath, conducting simultaneous measurements. The National Research Council of Canada also conducted coordinated, simultaneous ionospheric observations. OV3-6 measured much larger latitude variations than current atmospheric models had expected. A bulge in the neutral density in the summer hemisphere was also discovered. The data obtained was used to construct more accurate atmospheric models, and to correlate physical chemistry reactions to disturbances originating from the sun. OV3 Missions OV4 Background The OV4 series was designed to utilize space aboard the Manned Orbiting Laboratory (MOL) test flights. In September 1964, Raytheon was awarded a $220,000 contract to build a one-off pair of satellites, designed by the U.S.A.F. Avionics Laboratory. These two satellites would investigate long range radio propagation in the charged atmosphere of the ionosphere analogous to the whispering gallery transmission of sounds under a physical dome. In this way, the OV4-1 pair would evaluate the ionosphere's F layer as method of facilitating HF and VHF transmissions between satellites not in line of sight of each other. Spacecraft The OV4-1 satellite pair consisted of a transmitting spacecraft and a receiving spacecraft. OV4-1T's transmitter broadcast on three frequencies in the 20-50 MHz range. OV4-1R included receiving equipment and telemetry broadcast equipment. Launched into slightly different orbits, the satellites would test whispering gallery communications over a range of distances;