Explorer-1 Prime

Explorer-1 [Prime], also known as E1P and Electra, was a CubeSat-class picosatellite built by the Space Science and Engineering Laboratory (SSEL) at Montana State University. It was launched aboard a Taurus-XL rocket from Vandenberg Air Force Base, California on 4 March 2011, but failed to achieve orbit after the rocket malfunctioned.

As part of NASA's ELaNA program, E1P was to be launched along with NASA's Glory satellite,Kentucky Space's KySat-1 and the University of Colorado-Boulder's Hermes CubeSats.

E1P was a reflight mission of Explorer 1, the first American satellite, using modern technology including a geiger tube donated by James Van Allen. The name of the satellite was also adopted from Van Allen, who referred to the satellite as Explorer-1 Prime prior to his death in 2006.

It was originally intended to be launched in 2008 to commemorate the 50th anniversary of the launch of Explorer 1. If it had been successful, E1P would have been Montana's first successful launch of a satellite after the loss of SSEL's MEROPE in 2006.

Explorer 1

Explorer 1 was the first satellite of the United States, launched as part of its participation in the International Geophysical Year. The mission followed the first two satellites the previous year; the Soviet Union's Sputnik 1 and 2, beginning the Cold War Space Race between the two nations.

Explorer 1 was launched on January 31, 1958 at 22:48 Eastern Time (equal to February 1, 03:48 UTC) atop the first Juno booster from LC-26 at the Cape Canaveral Missile Annex, Florida. It was the first spacecraft to detect the Van Allen radiation belt, returning data until its batteries were exhausted after nearly four months. It remained in orbit until 1970, and has been followed by more than 90 scientific spacecraft in the Explorer series.

Explorer 1 was given Satellite Catalog Number 4, and the Harvard designation 1958 Alpha 1, the forerunner to the modern International Designator.

Background

The U.S. Earth satellite program began in 1954 as a joint U.S. Army and U.S. Navy proposal, called Project Orbiter, to put a scientific satellite into orbit during the International Geophysical Year. The proposal, using a military Redstone missile, was rejected in 1955 by the Eisenhower administration in favor of the Navy's Project Vanguard, using a booster produced for civilian space launches. Following the launch of the Soviet satellite Sputnik 1 on October 4, 1957, the initial Project Orbiter program was revived as the Explorer program to catch up with the Soviet Union.