An on-line catalog of intervals for which DE EICS data in SATF and SDF formats exists are available at the Laboratory for Atmospheric and Space Physics (LASP) server site . The catalog has Data Quality Flags for each telemetry interval. This page describes how the data sets cover the spaces listed below.

• Temporal Coverage
  • EICS Data were acquired from September 15, 1981 ( 81258 ) to February 18, 1991 ( 91049 ).
  • Temporal coverage of the DE -1 satellite started at ~80% and degraded to ~10% over the life of the mission.
  • Due to limitations of the NASA ground data processing system, it was possible to capture only ~50% of the intervals during which the DE/EICS instrument was operated in SATF data set .
  • Special efforts were made to schedule operations and capture DE/EICS data in SATF format during periods when DE -1 was in near magnetic conjunction with various satellites and ground stations. See pointers to lists of magnetic conjunction intervals below.
  • A list of All intervals during which DE -1 telemetry was acquired is available, on request, from W.K. Peterson. However, it is not practical to produce EICS SATF files for intervals which do not exist in the SATF data catalog
  • SDF files were produced for intervals during which:
    • A file in SATF format was available.
    • DE -1 was above ~8,000 km altitude.
    • EICS was operating in one of two standard modes.
  • EICS data in SDF format exist for a large fraction of the intervals in the data catalog. EICS/SDF data from intervals marked with the N Data Quality Flag should be used with caution.
• Return to a description of the SDF or SATF data sets.
• Spatial Coverage
  • Geographic and Geomagnetic position information ( documented in the skeleton table) are included in the format and accessible as noted. The position information available in the SDF and SATF formats come from a variety of sources of different accuracy. Information about the position of DE -1 in a variety of geographic and geomagnetic coordinate systems is also available from the NASA Satellite Situation Center .
  • Limited position information is included in the SATF format but is not accessible using the SATF reading software distributed by the NSSDC.
  • DE -1 had apogee of ~22,500 km altitude or r/Re ~ 4.65
  • DE -1 had a nominal perigee of ~500 km which varied somewhat over the 10 year life of the mission.
  • Operations of the DE/EICS instrument were focused on altitudes above ~8,000 km. Limited data, in SATF format only, exists for altitudes below ~8,000 km.
  • The orbital inclination was 90 degrees, identical to DE -2.
  • The line of apsides precessed at a rate of ~ 1/3 degree per day. As noted in Yau et al. "Long Term (solar cycle) and seasonal variations of upflow ionospheric ion events at DE -1 altitudes" [J.G.R. 90, 6395, 1985], The three year period for apogee to precess 360 degrees combined with the 6 month period for the orbital plane to cover all local times produces non-uniform sampling of altitude/local time combinations.
  • Special efforts were made to schedule operations and capture DE/EICS data in SATF format during periods when DE -1 was in near magnetic conjunction with various satellites and ground stations. See pointers to lists of magnetic conjunction intervals below.
• Return to a description of the SDF or SATF data sets.
• Mass Coverage
  • 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+.
• Return to a description of the SDF or SATF data sets.
• Energy Coverage
  • 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.

  Return to a description of the SDF or SATF data sets.

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  Prepared by W.K. Peterson
  Last updated 09/13/2005 by Daryl Carr
  

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