• Over 10 satellites so far in an ongoing program sponsored by the Department of Energy
• Continuous data acquisition from 1976 to the present
• Typically we receive data from 3-4 satellites simultaneously
• Data is received in real time 24 hours/day
• The satellites operate at geosynchronous orbit
  • circular orbit at 6.6 Re at the geographic equator
  • 24-hour orbital period so the satellites are at fixed longitude
  • the magnetic latitude can be up to 11 degrees
• The spin period is about 10.24 seconds
• The spin axis is actively controlled to point toward the center of the Earth

Principal Investigator: Eric Dors
SOPA and CPA Instrument Designs

The CPA Instrument

• Flown on satellites launched from 1976 to 1987
• Last operation was in 1995
• Measures electrons from 30 keV to 2 MeV in 12 energy channels
• Measures protons from 75 keV to 200 MeV in 26 energy channels

The SOPA Instrument

• Flown on satellites launched beginning in 1989
• Measures electrons from 50 keV to 26 MeV in 16 energy channels
• Measures protons from 50 keV to >50 MeV in 15 energy channels
• Measures heavy ions in 10 channels, 7 mass groups, at energies >0.5 MeV

• Data are acquired in real time at Los Alamos
• Data are processed, formatted and put on-line every night
• Digital data and summary plots are typically available within 24 hours
• Digital data and summary plots are available from 1976 to the present