STEREO/STE


Updates

Last modification on 07/08/2008

Instrumentation

The Suprathermal Electron (STE) instrument - part of the IMPACT (In-situ Measurements of Particles And CME Transients) investigation- is designed primarily to measure electrons from ~2 to ~100 keV (Lin et al., 2008). STE utilizes arrays of small, passively cooled, thin window silicon semiconductor detectors (SSDs), coupled to state-of-the-art pulse-reset front-end electronics, to detect electrons down to ~2 keV (well below the typical SSD thresholds of >~20-30 keV) with about 2 orders of magnitude increase in sensitivity over previous sensors at energies below ~20-30 keV. STE will also detect ions and neutrals that penetrate the window and deposit >~2 keV in the SSD active volume (>~4 keV for incident protons/hydrogen). STE provides intrinsic energy resolution of <~1 keV FWHM, with the particles counts binned into energy channels of ΔE/E ~10-25%. STE-U detects particles coming from the Sun, with a total FOV of 70° x 70° centered on the nominal Parker spiral field direction. STE-D has four detectors (D3, D0, D1, D2) observing particles coming toward the Sun, each having a field of view (FOV) from 40° S to 40° N ecliptic latitude by 20° longitude, for a total STE-D FOV of 80° x 80° centered on the nominal Parker spiral field direction.

STE detectors Door and aperture

Caveats and notes regarding STE data

The files contain electron intensities at 2-100 keV. STE science data officially started in January 2007 for STEREO A and in November 2007 for B. The in-orbit calibration is intermittently operated when the door that has radioactive source inside is closed.


Flux-time profiles

  • Units: counts. The conversion code is provided to convert count into flux (#/(cm2 s1 sr1 eV1)) and distribution fuction (#/(m6 s-3)) and to calculate the central energy for each bin.
  • Time resolution: 10 s.
  • 32 energy bins (#0-31). The energy is in eV after unit conversion. The original unit in CDF files is keV.
  • FOV doesn't cover all angles. The converstion code for pitch angle distributions can be provided on request.
  • The lowest energy bin/bins and the highest energy bin may be dominated by noise when the actual electron fluxes are low. In Detector D2, the lowest energy bins are often dominated by noise.
  • Electronics issues cause large, unreal counts at ~50-60 keV (~30-40 keV) in detector D0 for STEREO A(B).
  • Energy bins above ~20 keV may have some background due to the leakage of onboard X-ray calibration source, if the actual electron fluxes are low.
  • When the Earth and/or Moon are within the detector's FOV, photons can cause a leakage current to reduce counts at low energies. This often happens during the early orbit when the spacecraft is close to the Earth.

    flux energy spectrum flux energy spectrum

    Questions about the STE instrument and data should be directed to Robert P. Lin (rlin@.ssl.berkeley.edu) and Linghua Wang (windsound@ssl.berkeley.edu)

    The page is maintained by: Linghua Wang (windsound@ssl.berkeley.edu)