Editing Explorer 4 (section)

== Instrument ==
=== Charged Particle Detector ===
The purpose of this experiment was to extend the first measurements of the trapped radiation belt discovered with [[Explorer 1]] and [[Explorer 3]] and to provide measurements of artificially injected electrons from the three high-altitude Argus nuclear detonations. Four separate radiation detectors were used in the experiment: a shielded directional plastic scintillation counter sensitive to electrons (E>700 keV) and protons (E>10 MeV), a shielded directional [[caesium iodide]] scintillation counter sensitive to electrons (E>20 keV) and protons (E>400 keV), an omnidirectional Anton type 302 [[Geiger counter|Geiger–Müller]] (GM) counter sensitive to electrons (E>3 MeV) and protons (E>30 MeV), and a shielded omnidirectional Anton type 302 [[Geiger-Müller tube]] sensitive to electrons (E>5 MeV) and protons (E>40 MeV). The plastic scintillation counter and the [[caesium iodide]] (CsI) scintillation counter were each viewed by a separate [[Photomultiplier tube]]. These detectors were mounted orthogonally to the longitudinal axis of the satellite with apertures facing in opposite directions. The two GM counters were located side by side along the satellite longitudinal axis.<ref name="Instrument1">{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1958-005A-01|title=Experiment: Charged Particle Detector|publisher=NASA|date=28 October 2021|access-date=1 November 2021}} {{PD-notice}}</ref>