An engineering model of the UK-1 (Ariel 1) satellite at the Royal Society in London. UK-1, designed to observe the upper atmosphere and measure solar radiation and charged particles, was launched on 26 April 1962 by an American Thor-Delta and renamed Ariel 1 once in orbit. This is a 'real' satellite but was never intended to be a flight model, being used for ground-based engineering tests only. The body diameter is 0.56m and the boom span is 3m.