ARIEL 5 was one of the earliest X- ray astronomy satellites and involved British- American collaboration. It was launched into a low inclination (2.8 degrees) orbit from the San Marco launch platform in the Indian Ocean on 15th October, 1974. The lifetime of this satellite was six years. The satellite energy ranges from 0.3 – 40 keV. It carried six experiments (five for U.K and one for U.S) for cosmic X- ray studies that measured the spectra, polarization, and pulsar features of X- ray sources. The four experiments was utilized for position measurements of X- ray stars and to measure their energy spectra, while the other two for scanning the sky perpendicular to the spin axis. The satellite was approximately in cylindrical in shape, 38 in. in diameter by 34- in. high. It was launched in a quasi- circular orbit at a height of 400 to 500 km. During operation, it spun at a rate of 10 revolutions per minute. The satellite was designed to operate over a restricted range of solar aspects with the sun within 45 deg of normal to the spin axis. The satellite re- entered the Earth’s atmosphere on 14 March, 1980.