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6.4-min, Energy-Mass Spectra Data


Availability: Archived at NSSDC, accessible from elsewhere

Time span: 1984-08-16 to 1988-07-17


These 6.4-min averages of data from the Hot Plasma Composition Experiment (HPCE) are written on magnetic tape in SFDU format. Each physical block has a fixed length of 28672 bytes, written in English/ASCII and VAX binary representation. The volume header provides an outline of the content and structure of the entries. It is followed by an ephemeris file of many blocks, which includes the spacecraft's position and velocity components in the GSE system; geographic latitude, longitude, and LT; SM latitude and MLT; and the GSE components of a model (not measured) magnetic field; each at 5-min intervals. Written next is an attitude file that includes the right ascension and declination of the direction of the spin axis, once every orbit. It is followed by an "events" file that provides information on maneuvers, data gaps, anomalous conditions, etc. The final sequence of files provides the HPCE data written as one file per day of data. Each logical "energy average mode" record of 9424 bytes provides the 6.4-min averages of the following parameters: (a) H+, He+, He++, O+, O++ fluxes from each of the 18 energy channels covering 0.0014 to 17.11 keV/q, at each of the 9 pitch angle sectors; (b) fluxes of all ions, without mass discrimination, from each of those energy channels and sectors; (c) electron fluxes from each of the 8 energy channels covering 0.067 to 20.1 keV, at each of the 9 pitch angle sectors; (d) a number of computed asymmetry factors for the fluxes; and (e) spacecraft location, geographic and geomagnetic local times, and the measured magnetic field vector in the s/c coordinate system. The fluxes are in units of 1/(cm**2 s sr keV/q). About three days per month, the instrument was operated in the "mass average mode", providing mass-independent fluxes from 15 energy channels and 9 pitch angle bins for the ions, and electron fluxes from 8 energy channels and 9 pitch angle bins. Besides these 6.4-min averages, the data set in this mode contains 32-min accumulated c/s from each of 64 mass/q bins and 15 energy channels. The ion detector failed in April 1985, but electron data continued to be available.

Data are available online at

Alternate Names

  • 6.4-min, Energy-Mass Spectra


  • Space Physics: Magnetospheric Studies


  • 84-088A-01B

Additional Information



Questions and comments about this data collection can be directed to: Coordinated Request and User Support Office



NameRoleOriginal AffiliationE-mail
Mr. Stuart R. NylundData ProviderApplied Physics
Mr. Robert M. CandeyGeneral ContactNASA Goddard Space Flight
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