• The instrument is capable of resolving all major magnetospheric masses. (H+, He++, He+, O++, and O+).
• The M/Q range from less than H+ (1.0) to greater than Barium (138) in 64 non uniformly spaced mass steps.
• Because of the limited telemetry bandwidth available, the instrument was normally run in a mode when only 4 of the 64 possible mass steps were sampled.
• Software supplied with the SDF format includes data for only three masses. H+, O+, and He+.

• The EICS instrument covered the energy range from 0.000 keV/e above the spacecraft potential to ~ 20 keV/e in 32 logarithmically spaced steps.
• The instrument was normally operated using only 15 of the 32 possible energy steps. SDF format data were produced for intervals when the instrument was sampling only the standard 15 energy steps.
• The lowest energy channel has a nominal FWHM that covers the range from 0.000 keV above the spacecraft potential to ~0.135 keV/e.
• The instrument has a commandable retarding potential analyzer (RPA) in the input with 32 logarithmically spaced steps covering the range from 0.001 to ~0.100 keV/e to restrict entry of the dense core ion plasma. The input RPA voltage was usually set to ~ 0.010 keV/e at altitudes above ~ 8,000 km and ~0.100 keV/e below ~8,000 km.
• The value of the RPA setting is accessed and displayed by the software supplied by NSSDC with SATF format data. It is also included explicitly as the Low_energy_cut_off variable in the skeleton table.
• The center energies and FWHM of the 15 standard energies are included in the explictly given in the skeleton table. Additional documentation about energy coverage is contained in the text files supporting the SDF or SATF data sets.
• Angle Coverage
  • The DE/EICS instrument has an energy dependent field of view that is widest in the low energy channel.
  • The field of view at mid energies (~1 keV/e) is on the order of +/- 10 degrees out of the spin plane and +/- 5 degrees in the spin plane. See Shelley et al., Space Sci. Instrumentation, 5, 443, 1981 for more details.
  • The radial field of view of the instrument and cartwheel motion of the satellite in its polar orbit provided complete pitch angle coverage twice per satellite spin period (6 seconds) when the magnetic field direction was within a few degrees of the satellite spin plane.
  • Because of thermal control problems in the later years of the mission, it was not always orient the spacecraft so that the magnetic field direction was near the spin plane. At times the satellite was operated for extended periods when the angle between the spin plane and magnetic field was greater than 20 degrees.
  • Information about pitch angle coverage is available in the skeleton table) and using the software accompanying the SDF format was set (to 1) when a visual examination of a color spectrogram showed that complete pitch angle coverage was not available.
  • Information about the orientation of the observed fluxes with respect to the satellite velocity direction (i.e. the ram angle) is available ONLY in the SDF format and the A flag given in the on-line catalog of EICS data intervals indicates when ram angle information is available.
  • Some data in the lowest energy channel are contaminated by a spurious count rate caused by the photoionization of residual neutral gases in the preacceleration region of the instrument as described by Shelley et al. (Geophys. Res. Lett. 9, p942, 1982.). The C_flag variable in the C flag given in the on-line catalog of EICS data intervals were set on when a visual examination of color spectrograms indicated this type of spurious low energy signal.
• Return to a description of the SDF or SATF data sets.
• Magnetic Conjunctions
  • A considerable effort was made in the 10 years of DE -1 operation to acquire data at multiple locations along auroral magnetic field lines during periods of geophysical interest. Perhaps the best conjunction in the life of DE -1 occurred on January 28, 1990 When DE -1, Akebono and one of the CANOPUS magnetometer stations were located near a cusp field line that showed a strong perturbation in the magnetic field at ONLY high altitude. This was interpreted by Peterson et al. as most consistent with the passage of an Alfven wave down the magnetic field line.
  • Numerous reports on investigations of the analysis of plasmas observed by DE -1 and -2 on nearly conjugate magnetic field lines are included in the on-line list of publications.
  • DE -1/ -2 In 1994 W.K. Peterson surveyed the literature and identified 17 intervals when DE -1 and -2 sampled nearly conjugate magnetic field lines under a variety of geomagnetic conditions. Data for most DE -1 and and -2 instruments was acquired for these intervals from the Space Physics Data Facility.
  • DE-1/Akebono Conjunction studies were based on the list of possible conjunctions. The list has been edited to exclude times when DE -1 was not operating. It still includes times when the Akebono satellite was not operating.
  • A list of possible times when the AMPTE/CCE Satellite and DE -1 were in conjunction has been prepared.
  • A list of possible times when the CRRES satellite and DE -1 were in conjunction has been prepared.

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