E2 Flux-gate Magnetometer

Helios 1 and 2 were equipped with two different magnetometer experiments: the Fluxgate Magnetometer for Field Fluctuations experiment (E2) and the Fluxgate Magnetometer for Average Fields experiment (E3). Experiment E2 used a boom mounted magnetometer that consisted an orthogonal, triaxial fluxgate sensor: two sensors in the spin-plane and one parallel to the spin-axis.

Principal Investigators

Prof. Fritz M. Neubauer || Technische Universitat Braunschweig
Dr. Guenter Musmann || Technische Universitat Braunschweig

Original Data Description

  • The presentation Magnetometer Experiment E2 (Fluxgate) onboard Helios 1 and 2 (from the Cologne Workshop), records previously unavailable information about experiment E2 directly from the original PI, F. M. Neubauer. Some of the information is solely from Neubauer's memory. The contents of this presentation include:
    • Sensor parameters (axis, sensitivities, etc)
    • Helios spacecraft data collection (sampling rates, shock mode, etc)
      • "Event data or shock data consisted of high time-resolution E2 data,E4 waveform and spectral data and selected E5 electric field data. This data is not available any more because of limited archiving!" - Neubauer
    • Onboard analogue to digital data conversion
    • A mechanical flipper rotated the sensors 90° to help with calibration, but had limited use due to thermal design failures[2]
    • This flipping problem affects the dataset in the early phase of the mission[2]
  • A triad of orthogonal sensors were mounted 2.75-meters from the spacecraft spin axis
    • A mechanical flipper rotated the sensors 90° to help with calibration, but had limited use due to thermal design failures[2]
    • Helios 1 and 2 had opposite spin directions[4] (details can be found in Wennmacher’s Cologne Presentation)

Data Availability and Reanalysis

  • All available data has been processed (original tapes were thrown away):
  • Wennmacher’s Cologne presentation, E2 data history, format, and availability, documents the timeline of E2 data transfers and conversions
    • The original tapes were thrown away
    • All ADR-data (Analysis Data Records) was converted to IGM data format
  • There's been a thorough analysis of the E2 data in conjunction with the E3 data, and discussed in detail at the Cologne Workshop. This information is compiled in an Action Item List.
  • Steinhagen’s Cologne presentation, Revisiting HELIOS: The Magnetic Field Data, documents the errors, inconsistencies, and gaps in E2 data
    • The available E1, E2, and E3 data was used in reanalyzing E2 data
  • See also, Salem's Presentation at Imperial College London discussing the various inconsistencies with the E2 data
  • Oddities and Issues:
    • Erroneous zero-points: 4Hz data shows a 2Hz peak in the RT plane (radial-tangential) but not in the normal plane[1]
    • E2 Bz component shows a nonconstant nonzero offset, so be careful when using it
    • 4Hz 50nT cut on all three components Bx By and Bz and even more so the modulus
    • 4Hz data also shows gaps well below the 50nT limit (25nT?) when E2 40.5 sec data shows no gaps[1]
    • 40.5 sec averages (archived at NSSDC) were calculated with different, possibly a more complete, E2 4Hz dataset[1],[3] that does not seem to exist anymore. Indeed these 40.5 sec NSSDC averages seem to be okay and do not display 50nT cuts.
    • The 40.5 sec E2 mag data averages contained in the E1 plasma data files (in the header of the file, above distribution function data) are more problematic:
      • These averages are a factor 10 (on average) higher than the NSSDC ones or the 4Hz data
      • They show gaps when NSSDC averages do not.