Helios (spacecraft)

Helios-A and Helios-B (after launch renamed Helios 1 and Helios 2) are a pair of probes that were launched into heliocentric orbit to study solar processes. As a joint venture between German Aerospace Center (DLR) and NASA, the probes were launched from Cape Canaveral Air Force Station, Florida, on December 10, 1974, and January 15, 1976, respectively. The Helios project set a maximum speed record for spacecraft of . Helios-B performed the closest flyby of the Sun of any spacecraft until that time. The probes are no longer functional, but as of 2023 remain in elliptical orbits around the Sun. The Helios project was a joint venture of West Germany's space agency DLR (70 percent share) and NASA (30 percent share). As built by the main contractor, Messerschmitt-Bölkow-Blohm, they were the first space probes built outside the United States and the Soviet Union to leave Earth orbit. The two Helios probes look similar. Helios-A has a mass of , and Helios-B has a mass of . Their scientific payloads have a mass of on Helios-A and on Helios-B. The central bodies are sixteen-sided prisms in diameter and high. Most of the equipment and instrumentation is mounted in this central body. The exceptions are the masts and antennae used during experiments and small telescopes that measure the zodiacal light and emerge from the central body. Two conical solar panels extend above and below the central body, giving the assembly the appearance of a diabolo or spool of thread. At launch, each probe was tall with a maximum diameter of . Once in orbit, the telecommunications antennae unfolded on top of the probes and increased the heights to . Also deployed were two rigid booms carrying sensors and magnetometers, attached on both sides of the central bodies, and two flexible antennae used for the detection of radio waves, which extended perpendicular to the axes of the spacecraft for a design length of each. The spacecraft spin around their axes, which are perpendicular to the ecliptic, at 60 rpm. Electrical power is provided by solar cells attached to the two truncated cones.