The Explorer series, which made history in January 1958 when Explorer 1 became the first U.S. space satellite, consisted of more than fifty satellites launched over a period of about 15 years. The 'Satellite Explorer' app provides real time tracking of satellites and space stations displayed in real time graphically on a tracking map. Launched late on 31 January 1958 (10:48 p.m. EST, or 03:48 UTC on 01 February) on an Juno-1 rocket (adapted Jupiter-C), Explorer 1 carried instrumentation for the study of cosmic rays, micrometeorites, and for monitoring of the satellite's temperature.. A real time Bing Map view of what would be seen from the satellite looking down toward the center of the earth as it speeds across the world at speeds often over 10,000 MPH (16,000 KPH) is included. The Juno-1 launch vehicle consisted of four propulsive stages. It was the last of the original series of Explorers built, designed, and operated by the Jet Propulsion Laboratory.. The satellite remained aloft for more than a decade before re-entering Earth's atmosphere on March 31, 1970. Explorer 1 was the first successfully launched U. S. spacecraft. Explorer 5 was a United States satellite with a mass of 17.24 kg. It launched atop a Juno I rocket on August 24, 1958 from Launch Complex 5, but failed when the rocket's first stage collided with its second stage after separation, causing the upper stage firing angle to be off. Explorer 1 was the first satellite launched by the United States when it was sent into space on January 31, 1958. Explorer Series of Spacecraft Over the comparatively short but eventful history of the U.S. space program, a large number of spacecraft -- including the very first American satellite launched by the Army Ballistic Missile Agency on January 31, 1958 -- have borne the name, "Explorer." Explorer 1 sent data back to Earth for four months, ceasing communications on May 23, 1958. Explorer 3 was the third satellite of the Explorer mission series and the first successful follow-on to Explorer 1, which made history when in January 1958 it became the United States' first space satellite.