Mission History
A brief introduction to the 1970's Helios project
The Helios mission consisted of two spacecrafts that were used to make observations of the inner heliosphere. Helios 1 (A) was launched on December 10, 1974, and Helios 2 (B) was launched on January 15, 1976. Operations ceased for Helios 2 on March of 1980 due to failure of its radio transceiver. Helios 1 continued to transmit data for over a decade, sending its final transmission in February of 1986.
The joint Helios project took its first steps towards realization in September of 1966, when an agreement was made between the German Federal Ministry of Scientific Research and NASA. In April of 1969 the Helios Mission Definition Working Group published the Helios Program Mission Definition Group Report that defined the parameters of the mission. And so, the project was under way.
A good read on the history and the significance of this mission is 10 Jahre Helios/10 Years Helios: publication celebrating the 10 year anniversary of the launch of Helios on December 10th 1974 (text in German and in English).
Experiments
The original instrument papers for each of the experiments listed below can be found on our instrumentation page. A short description of the instrumentation involved can be found on the NSSDC website through the experiment-title links below.
| Experiment | Instrument/Investigation | Measurement Descriptions | Principal Investigator | Institution |
|---|---|---|---|---|
| E1 | Plasma Detectors | Velocity distribution functions of solar wind protons, alpha-particles, and electrons. | (1) Dr. Helmut R Rosenbauer (2) Dr. Rainer Schwenn | (1)(2) Max-Planck-Institut fur Aeronomie |
| E2 | Fluxgate Magnetometer for Field Fluctuations | Magnetic field strength and direction of low-frequency magnetic fields in the inner heliosphere. | (1) Prof. Fritz M. Neubauer (2) Dr. Guenter Musmann | (1)(2) Technische Universitat Braunschweig |
| E3 | Fluxgate Magnetometer for Average Fields | Magnetic field strength and direction of low-frequency magnetic fields in the inner heliosphere. | (1) Dr. Norman F. Ness (2) Prof. Franco Mariani | (1) NASA Goddard Space Flight Center (2) Universita degli Studi di Roma |
| E4 | Search Coil Magnetometer | Complement of the Flux-gate Magnetometer by measuring the magnetic field fluctuations up to 3kHz. | (1) Prof. Fritz M. Neubauer (2) Dr. G. Dehmel | (1)(2) Technische Universitat Braunschweig |
| E5A | Solar Wind Plasma Wave | Electric field of plasma waves in the solar wind from 10Hz to 3Mhz. | (1) Prof. Donald A. Gurnett (2) Dr. Paul J. Kellogg | (1) University of Iowa (2) University of Minnesota |
| E5B | Fine Frequency, Coarse Time Spectrum Analysis | Electric field of plasma waves in the solar wind from 10Hz to 3Mhz. | (1) Prof. Donald A. Gurnett (2) Dr. Paul J. Kellogg | (1) University of Iowa (2) University of Minnesota |
| E5C | Solar Wind Plasma and Radio Wave | Electric field of plasma waves in the solar wind from 10Hz to 3Mhz. | (1) Prof. Donald A. Gurnett (2) Dr. Paul J. Kellogg | (1) University of Iowa (2) University of Minnesota |
| E6 | Cosmic-Ray Particles | Energetic protons, electrons, and x-rays to determine the distribution of cosmic rays | Dr. Horst W. Kunow | Universitat Kiel |
| E7 | Galactic and Solar Cosmic Rays | Energetic protons, electrons, and x-rays to determine the distribution of cosmic rays | Dr. James H. Trainor | NASA Goddard Space Flight Center |
| E8 | Energetic Electron and Proton Detector | Higher energy portion of the crossover region between solar wind particles and cosmic rays. | Dr. Ehrhard Keppler | Max-Planck-Institut fur Aeronomie |
| E9 | Zodiacal Light Photometer | Scattering of sunlight by interplanetary dust particles. | Dr. Christoph Leinert | Max-Planck-Institut fur Aeronomie |
| E10 | Micrometeoroid Detector and Analyzer | Composition, charge, mass, velocity, and direction of interplanetary dust particles. | (1) Dr. Hugo Fechtig (2) Dr. Eberhard Grun | (1)(2) Max-Planck-Institut fur Kernphysik |
Orbits
The orbits of the Helios 1 and 2 spacecrafts have periods of 190 and 187 days, aphelia of 0.99 and 0.98 AU, and perihelia of 0.31 and 0.29 AU, respectively. Thanks to their unique trajectories, Helios 2 was able to clench two records: the closest flying spacecraft to the sun (beaten 4 DECADES later, August 12, 2018) and the fastest human made object.