ABSTRACT
Series of six UK-led scientific satellites launched 1962–79. The first four studied the ionosphere, while the last two were x-ray astronomy satellites. Ariel 3 was the first all-British satellite. The UK–US Ariel 5, launched in October 1974, operated for more than five years and discovered dozens of new x-ray sources, including a number of transient sources such as Cygnus X-1
