EntityQ370053· pop 19· linked from 160 articlesExplorer 4Sign in to saveAmerican research satellite launched in 1958ConnectionsNOTS-EV-1 PilotEntityExplorers ProgramEntitySputnik 3EntityEarthConceptnuclear weaponEntityEarth scienceEntitypublic domainEntityGreenwich Mean TimeEntityorbital periodEntityapsisEntitymagnetosphereEntityGeiger counterEntityVan Allen radiation beltEntityorbital inclinationEntityUnited States Department of DefenseConceptJet Propulsion LaboratoryEntityExplorer 1EntityCape Canaveral Space Force StationEntityDefense Advanced Research Projects AgencyEntityJames A. Van AllenEntityCategories1958 in the United StatesExplorers ProgramGeomagnetic satellitesSource attributionSpacecraft launched in 1958Spacecraft which reentered in 1959