 ESA launched its first major scientific mission in 1975, Cos-B, a space probe monitoring gamma-ray emissions in the universe, which was first worked on by ESRO.ESA collaborated with NASA on the International Ultraviolet Explorer (IUE), the world's first high-orbit telescope, which was launched in 1978 and operated successfully for 18 years.A number of successful Earth-orbit projects followed, and in 1986 ESA began Giotto, its first deep-space mission, to study the comets Halley and Grigg–Skjellerup.