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In our previous article, we covered Helios-B (aka Helios 2). Today we will be discussing the important experiments and instruments onboard Helios-A and Helios-B.

Helios Probes

Experiments and various instruments involved

1. Plasma Experiment

It made use of four independent instruments designed to investigate the solar wind plasma. The bulk velocity, density, and temperatures of the different particles were measured. By measuring the velocity distribution functions of the different kinds of particles, the all-important hydrodynamic parameters of the solar wind plasma can be derived.

2. Micrometeoroid Analyser

Until Helios the characteristics of micrometeoroids had not been investigated to any great extent. Helios investigated the composition, charge, mass, velocity and direction of interplanetary dust particles. Comets have known to be the source of interplanetary dust.

3. Zodiacal Light Photometer

It counts the number of electrons and energy. The weak glow in the sky, called the Zodiacal Light, has been known for a long time. It is the result of the scattering of sunlight by interplanetary dust particles. The density and distribution of these particles cannot be measured from Earth, so Helios measured the intensity of the light at various angles.  The observation of the zodiacal light has established some of the properties of interplanetary dust present between 0.1 AU and 1 AU from the Sun, such as their spatial distribution, color and polarization.

End of operations

The primary mission of each probe spanned 18 months, but they operated much longer. On March 3, 1980, four years after its launch, the radio transceiver on Helios-B failed. On January 7, 1981, a stop command was sent to prevent possible radio interference during future missions.

Both probes collected important data about the processes that cause the solar wind and the acceleration of the particles that make up the interplanetary medium and cosmic rays. These observations were made over a ten-year period from solar minimum in 1976 to a solar maximum in the early 1980s.

In our next article we will discuss about the next mission to explore our sun.


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