EntityQ550613· pop 20· linked from 166 articlesExplorer 3Sign in to saveAmerican military research satelliteConnectionsNOTS-EV-1 PilotEntityExplorers ProgramEntitySputnik 3EntityJuno IEntityYouTubeConceptInternational Standard Book NumberEntityEarth scienceEntitywattEntitypublic domainEntityInternational Standard Serial NumberEntityradiationEntityhertzEntitySputnik 1EntityantennaEntitycosmic radiationEntityGreenwich Mean TimeEntityorbital periodEntityOCLC, Inc.EntityapsisEntitySmithsonian InstitutionEntityCategories1958 in the United StatesExplorers ProgramSource attributionSpacecraft launched in 1958Spacecraft which reentered in 1958