The first of these satellites was launched in 1976. The most recent satellite was launched in 1994. The energetic particle detectors measure electrons and positive ions with energies greater than 10s of keV. Two generations of energetic particle instruments have been flown.
Satellites carrying both generations of instruments continue to operate and provide data.
The sections below provide more information on the data themselves. Data Format Data are stored in compressed binary format but are provided in tab-delimited text format. Each data file contains data from one satellite for one day. Text files include satellite ephemeris and a header which gives the energy range for each column. Data can also be provided as plots.