This is a refurbished full-scale replica of the Explorer 17 aeronomy satellite. Explorer 17 was one of the first launched by NASA to study the Earth's upper atmosphere. The pressurized stainless steel sphere carried instruments to measure density, pressure, and temperature. It also contained a neutral mass spectrometer to study the composition of the gases in the upper atmosphere. The satellite was placed in a 158- to 570-mile orbit on April 3, 1963 by a Thor Delta launch vehicle. Data from the mass spectrometer showed the presence of molecular oxygen, atomic and molecular nitrogen and argon in the upper atmosphere; it also led to the discovery of a belt of neutral helium about the Earth. Constructed of original parts, it was refurbished by technicians at the Goddard Space Flight Center prior to its transfer to NASM from NASA in March 1975.
Transferred from the National Aeronautics and Space Administration