Helios (spacecraft)

This article is about the solar orbiting spacecraft. For the NASA experimental aircraft, see Helios Prototype. For French military photo-reconnaissance satellites, see Helios 1B and Helios 2 (satellite).

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 West Germany's space agency DFVLR (70% share) and NASA (30%), the probes were launched from Cape Canaveral, Florida, on Dec. 10, 1974, and Jan. 15, 1976, respectively. Built by Messerschmitt-Bölkow-Blohm as the main contractor they were the first spaceprobes built outside the US or USSR.

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.

Mission background

Scientific instruments

Instrument Name	Description
Plasma Experiment Investigation	Measures the velocity and distribution of the solar wind plasma.
Flux-gate Magnetometer	Measures the field strength and direction of low frequency magnetic fields in the Sun’s environment.
Search Coil Magnetometer	Complements the Flux-Gate Magnetometer by measuring the magnetic fields between 0 and 3 kHz.
Plasma Wave Investigation	Measures and analyzes waves of free ions and electrons in the solar wind plasma, 10 Hz to 3 MHz region.
Cosmic Radiation Investigation	Measures protons, electrons and x-rays to determine the distribution of cosmic rays.
Low-Energy Electron and Ion Spectrometer	Investigates the higher energy portion of the crossover region between the solar wind particles and the cosmic rays.
Zodiacal Light Photometer	Measures the scattering of sunlight by interplanetary dust particles.
Micrometeoroid Analyser	Investigates the composition, charge, mass, velocity and direction of interplanetary dust particles.

Mission profile

Helios-A sitting atop the Titan IIIE / Centaur launch vehicle.

Launch and trajectory

Trajectory of the Helios space probes.

Timeline of travel

Date	Event
1974-12-10	Launch of Helios-A
1976-01-15	Launch of Helios-B
1976-04-17	Closest flyby of the Sun of any spacecraft, performed by Helios II.

Gallery

Launch configuration diagram.  A technician stands next to one of the twin Helios spacecraft.  Inspection of Helios-B.  A Helios probe being encapsulated for launch.

See also

• 1974 in spaceflight
• 1976 in spaceflight
• List of vehicle speed records
• Timeline of artificial satellites and space probes

External links

• Helios 1 - NSSDC Master Catalog
• Helios 2 - NSSDC Master Catalog
• Helios 1 Mission Profile by NASA's Solar System Exploration
• Helios 2 Mission Profile by NASA's Solar System Exploration
• Titan/Centaur D-1T TC-2, Helios A, Flight Data Report
• Titan/Centaur D-1T TC-5 Helios B, Flight Data Report
• Honeysuckle Creek Tracking Station
• Astronautix Helios page
• Helios-Project - Max-Planck-Institut für Sonnensystemforschung