HELIOS

HELIOS was the first US/German interplanetary mission. Launched in 1974 (HELIOS 1, 10 December 1974 - 15 March 1986) and 1976 (HELIOS 2, 15 January 1976 - 8 January 1981), the two German built (MBB) Helios probes approached the sun closer than the inner planet Mercury (0.3 AU) and closer than any spaceprobe ever. Both probes studied the interaction of the sun and the earth, including, among other things, such phenomena as the characteristics of solar winds with complementary measurements. The link with the spacecraft was maintained around the clock over a distance of up to 186 million miles. A 100 feet (30 m dish) DLR antenna in Weilheim and the NASA deep space ground stations served these missions. The two HELIOS probes were operated and controlled by GSOC over 11 years, providing measurements for longer than one eleven year solar cycle (the originally expected life-time was 18 months).