Explorer 1 Overview | NASA www.nasa.gov

10 Things to Know About... solarsystem.nasa.gov

Explorer 1 - Wikipedia en.wikipedia.org

Explorer | National Air and... airandspace.si.edu

Spacecraft Spotlight:... spacecenter.org

Explorer 1 anniversary... astronomy.com

Our SpaceFlight Heritage:... www.spaceflightinsider.com

Explorer 1 in orbit - Stock... www.sciencephoto.com

Explorer 1: How America's... www.youtube.com

Jan. 31, 1958: Explorer I... www.wired.com

Explorer 1 anniversary... astronomy.com

Explorer 1 | Home Page explorer1.jpl.nasa.gov

Explorer 1: The Beginning... www.vaticanobservatory.org

A U.S.-Made Moon: 60 Years... www.americaspace.com

Relive Launch of Explorer... www.space.com

Explorer 1, 2, 3, 4, 5 -... space.skyrocket.de

File:Explorer1.jpg -... commons.wikimedia.org

Scale Model News: EXPLORER... www.scalemodelnews.com

Story of Explorer 1 | NASA www.nasa.gov

NASA — 10 Things to Know... nasa.tumblr.com