Helios

German-American spacecraft orbiting the sun

Helios 1 and Helios 2 were a pair of deep space probes developed by the Federal Republic of Germany (FRG) in a cooperative program with NASA. Experiments were provided by scientists from both FRG and the U.S. NASA supplied the Titan/Centaur launch vehicle. Each spacecraft was equipped with two booms and a 32 m electric dipole. The payload consisted of a fluxgate magnetometer; electric and magnetic wave experiments, which covered various bands in the frequency range 6 Hz to 3 MHz; charged-particle experiments, which covered various energy ranges starting with solar wind thermal energies and extending to 1 GeV; a zodiacal-light experiment; and a micrometeoroid experiment. The purpose of the mission was to make pioneering measurements of the interplanetary medium from the vicinity of the earth's orbit to 0.3 AU. The spin axis was normal to the ecliptic, and the nominal spin rate was 1 rps. Instrument descriptions written by the experimenters were published in Raumfahrtforschung 19/5 (1975).

	Data Examples
	Data availability
	E1 Plasma Experiment
	E2 Flux-gate Magnetometer
	E5a Plasma Wave Experiment
	E6 Cosmic Ray Experiment
	E8 Low-Energy Electron and Ion Spectrometer
	HELIOS publications by MPS members

Data Examples

Selected 3-D proton velocity distribution functions from Helios 2.
E1 instrument 1A, plots by H. F. Astudillo: local original
Example of a shock, magnetic cloud and bidirectional electrons seen by Helios 1 on March 1-3, 1978.
E1 and E2 instruments, plot by K. Ivory. ( PostScript)

Data availability

The largest data base of Helios data available on the World Wide Web is provided by the National Space Science Data Center ( NSSDC). Hourly Helios 1 & 2 plasma and magnetic field data are contained within the COHOWeb interface. The value of COHOWeb, besides its data subsetting and graphical display functionalities, is that each of many deep space spacecraft (Ulysses, Voyagers 1&2, Pioneers 10&11, etc.) have common data records (IMF vectors in a common coordinate system, s/c position vectors in a common coordinate system, etc.). This is an excellent starting point for multipoint studies of interplanetary phenomena (spatial structures and evolutions of interplanetary shocks, CME's, etc.).

Plots of the Helios mission heliocentric trajectories.

E1 Plasma Experiment

Principal investigator: H. Rosenbauer

The plasma experiment aboard the Helios solar probes consists of four independent instruments designed to investigate the solar wind plasma. By measuring the velocity distribution functions of the different kinds of particles, all important hydrodynamic parameters of the solar wind plasma can be derived. Three instruments (I1a, I1b, and I3) analyze the positive components (protons and heavier ions with energy-per-charge values from 0.155 to 15.32 kV) of the solar wind. Two of them allow for an angular resolution in both directions of incidence. One instrument (I2) measures electrons in the energy range from 0.5 the 1660 eV with one-dimensional angular resolution.

E2 Flux-gate Magnetometer

Principal investigator: F. B. Neubauer

The flux-gate magnetometer experiments use triaxial, orthogonal flux-gate sensors of the Forster type mounted on a boom of about 2 m from the spacecraft. The bandwidth is 4 Hz. Two measuring ranges are used with automatic switching. The sensitivity range extends from -100 nT to +100 nT.

Helios E1 and E2 data on magneto-optical discs (MOD) at MPS

The complete merged data set for the plasma experiment E1 and magnetometer experiment E2 for both Helios 1 and Helios 2 is available for local use at MPS on 19 MODs. The E2 data is averaged to match the time resolution of the E1 data. (Highest time resolution: 40.5 s/spectrum.)

Catalog of magneto-optical discs.
Structure description of Helios data.
Fortran include file with structures for Helios data ( raw text version).

Helios E1 and E2 data on compact disc (CD-ROM) at MPS

Selected parameters of the complete data set (19 MODs) have been compressed to fit on one CD. Documentation

Credits
Directory structure
File structure of table files
File structure of binary files
Appendix: ISO 9660 Filesystem

E5a Plasma Wave Experiment

Principal investigator: D. A. Gurnett

The University of Iowa plasma wave experiment (E5a) utilized the 32 m tip-to-tip dipole antenna to detect the electric component of plasma waves.

E6 Cosmic Ray Experiment

Principal investigator: H. Kunow

The cosmic ray particle experiment E6 (University of Kiel) consists of a detector telescope containing five semiconductor detectors of increasing thickness, a sapphire Cerenkov deteector surrounded by an anticoincidence scintillation detector, and an on-board handling system. The instrument is capable of measuring protons and heavier nuclei from 1.7 to more than 400 MeV/n and MeV electrons.

E8 Low-Energy Electron and Ion Spectrometer

Principal investigator: E. Keppler

The spectrometer utilizes an inhomogenous magnetic field for separation of charged particles. Protons (and heavier particles) traverse the magnetic field almost unaffected and are detected in a telescope arrangement consisting of two semiconductor detectors. Electrons are focused and detected by four semiconductor detectors. Positrons (if present) are deflected in the opposite direction and detected in another detector.

Kevin Ivory
22-02-1999