Ariel VThe first and highly successful British X-ray astronomy satellite launched into a 550-km equatorial orbit in Oct. 1974 from the San Marco platform off the Kenyan coast. Its six experiments (five UK, one US) were designed to detect, accurately locate, and measure spectral and temporal features of cosmic X-ray sources. Ariel V was spin-stabilized with the spin axis and period controlled by gas jets. Technically it was the first small scientific satellite to be operated in near real-time. Tracking, command, and data reception were carried out from NASA ground stations at Quito and on Ascension Island. The UK control station at the Rutherford Appleton Laboratory had data links to the experiment groups at the universities of Birmingham, Leicester, and London. The satellite and all experiments remained fully operational until mid-1977 when the control gas was exhausted. Subsequent operation with magnetometer attitude control was extended up to reentry in Mar. 1980.
Ariel V's major scientific achievements were the production of a new atlas of X-ray sources (the 3A catalog), including a number of short-lived transients, the establishment of Seyfert galaxies as powerful X-ray emitters, and the discovery of slow X-ray pulsators (now identified with magnetized neutron stars spinning with periods of minutes) and of abundant multimillion degree plasma in supernova remnants and in clusters of galaxies.