Helios-A and Helios-B (also known as Helios 1 and Helios 2), are a pair of probes launched into heliocentric orbit for the purpose of studying solar processes. A joint venture of the Federal Republic of Germany (West Germany) and NASA, the probes were launched from the John F. Kennedy Space Center at Cape Canaveral, Florida, on Dec. 10, 1974, and Jan. 15, 1976, respectively.
The probes are notable for having set a maximum speed record among spacecraft at 252,792 km/h (157,078 mi/h or 43.63 mi/s or 70.22 km/s or 0.000234c). Helios 2 flew three million kilometers closer to the Sun than Helios 1, achieving perihelion on 17 April 1976 at a record distance of 0.29 AU (or 43.432 million kilometers), slightly inside the orbit of Mercury. Helios 2 was sent into orbit 13 months after the launch of Helios 1. The Helios space probes completed their primary missions by the early 1980s, but they continued to send data up to 1985. The probes are no longer functional but still remain in their elliptical orbit around the Sun.