ARIEL

one of the five major satellites of Uranus. It was discovered in 1851 by William Lassell, an English astronomer, but was probably seen four years earlier by the Russian-born astronomer Otto Struve. Ariel orbits at a distance of 191,020 km (118,432 miles) from the centre of the planet. It has a period of 2.52 days. Ariel's estimated diameter is 1,330 km (825 miles), and its mass is thought to be about 1.8 10-5 that of Uranus. The satellite is thought to consist primarily of water ice, perhaps intermixed with small amounts of frozen methane and rock. Photographs taken by the U.S. Voyager 2 probe in 1986 showed that Ariel's surface is crisscrossed with scarps and long valley-like formations. Some of these are partially filled with materials that may have been produced by tectonic processes. In a few cases, ice appears to have spread out from the valleys across broad plains, much like glacier flows on the Earth. the first international cooperative Earth satellite, launched April 26, 1962, as a joint project of agencies of the United States and the United Kingdom. Design, construction, telemetry, and launching of the 14.5-kilogram (32-lb) satellite was handled in the United States by the National Aeronautics and Space Administration. The United Kingdom was responsible for designing the equipment and the experiments to measure electron density and temperature and composition of positive ions, intensity of solar radiation in ultraviolet Lyman-alpha line, and cosmic rays. the airy spirit who does Prospero's bidding in The Tempest by Shakespeare. Having been imprisoned by the witch Sycorax in a pine tree, Ariel is magically released by the exiled duke Prospero, who engages his services in thwarting Prospero's enemies, cultivating romance for his daughter, Miranda, and regaining his dukedom. After completing these tasks, Ariel is set free.