Helios (German solar probes)

Helios 2

Garnet. Credit: Mineral Information Institute.

Helios were two West German space probes launched by NASA and designed to study the Sun and interplanetary medium from within the orbit of Mercury, as close as 45 million kilometers (0.3 astronomical unit) to the Sun. They operated successfully for over 10 years. Both were launched from Cape Canaveral by Titan IIIE rockets. Helios 1 and 2 hold the record for the fastest spacecraft ever launched, having reached speeds of up to 250,000 kilometers per hour (150,000 mph) in their orbits around the Sun.


spacecraft launch date solar orbit mass (kg)
Helios 1 Dec 10, 1974 0.31 × 0.99 AU × 0° 370
Helios 2 Jan 15, 1976 0.39 × 1.00 AU × 0° 376