This is a flight backup to the Explorer 40 satellite mounted atop the Scout D launch vehicle on display at NASM. The nose cone cover of the rocket has been replaced by a clear Plexiglas version to display the satellite, also known as Injun V. The University of Iowa was the prime contractor for this spacecraft. It was transferred to NASM by NASA's Langley Research Center in 1975. On display since receipt, it has not been inspected by curatorial or conservation staff.

Explorer 40 formed part of a coordinated dual-satellite experiment to measure particle flux and energy as well as very low frequency emissions in the ionosphere and atmospheric density. The spacecraft package in the Scout D display also includes the inflatable radar tracking beacon that was used by Explorer 39. Measurements were to be performed simultaneously with the two satellites during an active part of the solar cycle to give information on the effect of solar activity on atmospheric density. Explorer 40 contained an extensive set of particle sensors and analyzers arranged in four major sets of experiments. One of its tasks was to evaluate the continuing decay of the Starfish artificial radiation belt created earlier in the decade. Explorer 40 was launched into a polar orbit from Vandenberg Air Force on August 8, 1968, and was operated periodically until June 1971.

Transferred from NASA's Langley Research Center to the Museum in 1977.