In 1961 the UKSpace Research Group accepted proposals for experiments to be carried on the third satellite of the Ariel programme. The British National Committee for Space Research selected experiments from those proposals and submitted them to NASA in 1962. The scientific objectives for the mission were selected in January 1963, and full work on the satellite began in early 1964 due to organisational and financial difficulties. A total of 5 craft were constructed. One prototype, two engineering models, the final satellite and a flight spare. The flight spare was later used as the basis of Ariel 4.
Operation
Power could be drawn from the batteries or the solar panels. The batteries were considered the least reliable component in the system so this method was devised to mitigate the issue. The spacecraft weighed.
Sensors
Ariel 3 carried five experiments. The experiments measured properties of the thermosphere as well as detected "terrestrial radio noise" from thunderstorms and measured large-scale galactic radio frequency noise. Ariel 3 was also fitted with a series of mirrors to observe the spin of the satellite. High-speed data was transmitted continuously to the Satellite Tracking and Data Acquisition Network. Low-speed data was recorded on tape recorders and was transmitted to ground stations in the high-speed mode when commanded. Three experiments expanded on data from the previous two missions. Two experiments collected data on naturally occurring radio noise.
Mission
Launch
The launch was originally planned for Wallops; Ariel 1 and Ariel 2 had both launched on the East coast. In 1964 experimenters requested a change to the proposed orbit, from an inclination of 50–70° to 78–80° to maximize coverage at the geomagnetic latitude. This change precipitated the launch site moving to the West coast. It was launched from Vandenberg Air Force Base on 5 May 1967 aboard a Scout rocket. This made it the first artificial satellite designed and constructed in the United Kingdom.
Operations
Ariel 3 had an orbital period of approximately 95 minutes, with an apogee of 608 km and a perigee of 497 km. It initially spun at 31 rpm for stability, though by the time the Ariel 3 deorbited, it had slowed to a rate of about 1 rpm. On 24 October 1967 the tape recorder aboard Ariel 3 began to malfunction. This restricted observation to real-time operation only. Ariel 3 suffered from a significant power failure in December 1968, restricting the satellite's operation to daylight hours only. The satellite was completely shut down in September 1969. Its orbit decayed steadily until on 14 December 1970 when Ariel 3 re-entered Earth's atmosphere.
