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Low-Energy Proton, Alpha Particle Measurement

NSSDCA ID: 1967-073A-08

Mission Name: OGO 4
Principal Investigator:Dr. John A. Simpson


Two solid-state particle telescopes were used to study low-energy cosmic-ray protons and alpha particles. One of these was a three-element range telescope ("vertical" telescope) that was capable of identifying protons and alpha particles (1.22 to 39.2 MeV/nucleon) and electrons (E>400 keV). The other detector was a one-element telescope ("horizontal" telescope) sensitive to protons and alpha particles in the energy range E>720 keV/nucleon. The vertical telescope axis of symmetry was parallel to the spacecraft Z axis which later became the spin axis. The horizontal telescope symmetry axis was nearly parallel to the spacecraft Y axis (perpendicular to the Z axis). Pulse-height information was sent back from the vertical telescope allowing pulse-height analyses of protons, alpha particles, and electrons (E>400 keV) using a 256-channel pulse-height analyzer. Count rate information was sent back from both telescopes. The time resolution ranged from about one measurement per 0.02 s to about one measurement per 0.3 s depending on the counting mode and the telemetry bit rate. The spin period of the spacecraft on January 23, 1969, was about 3 min. The experiment performed normally from launch until the satellite was put in an operational off mode on October 23, 1969. However, the spinning of the spacecraft made it difficult to interpret data after mid-January 1969.

Alternate Names

  • OGO4/Low-EnergyProton,AlphaParticleMeasurement

Funding Agency

  • NASA-Office of Space Science (United States)


  • Space Physics: Magnetospheric Studies
  • Space Physics: Heliospheric Studies

Additional Information

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



NameRoleOriginal AffiliationE-mail
Dr. Charles Y. FanOther InvestigatorUniversity of Arizona
Prof. Edward C. Stone, Jr.Other InvestigatorCalifornia Institute of
Dr. John A. SimpsonPrincipal InvestigatorUniversity of Chicago
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