Helios (spacecraft)

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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 / Helios B
Helios spacecraft.jpg
Prototype of the Helios spacecraft
Operator NASA / FRG
Major contractors MBB
Mission type Orbiters
Launch date Helios-A : 1974-12-10 07:11:01.5 UTC
(40 years, 11 months and 15 days ago)
Helios-B : 1976-01-15 05:34:00 UTC
(39 years, 10 months and 10 days ago)
Launch vehicle Titan IIIE / Centaur
Launch site Space Launch Complex 41
Cape Canaveral Air Force Station
Mission duration Helios-A :
January 16, 1975 to
February 18, 1985
Helios-B :
July 21, 1976 to
December 23, 1979
Satellite of Sun
COSPAR ID Helios-A : 1974-097A
Helios-B : 1976-003A
Homepage Helios-A : NASA Solarsystem Exploration page
Helios-B : NASA Solarsystem Exploration page
Mass 370 kg (820 lb)
Power (solar array)

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 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[1] (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),[2] 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.[not verified in body]

Mission background[edit]

Scientific instruments[edit]

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[edit]

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

Launch and trajectory[edit]

Trajectory of the Helios space probes.

Timeline of travel[edit]

Date Event
Launch of Helios-A
Launch of Helios-B
Closest flyby of the Sun of any spacecraft, performed by Helios II.


Launch configuration diagram
Launch configuration diagram. 
A technician stands next to one of the twin Helios spacecraft
A technician stands next to one of the twin Helios spacecraft. 
Inspection of Helios 2
Inspection of Helios-B
Helios probe being encapsulated for launch
A Helios probe being encapsulated for launch. 

See also[edit]


External links[edit]