IMP-A satellite


Display Status:

This object is on display in the Space Science exhibition at the Steven F. Udvar-Hazy Center in Chantilly, VA.

Collection Item Summary:

This is the engineering model for the Interplanetary Monitoring Platform A (IMP-A or Explorer 18). It is the first of a series of seven satellites designed to be launched before and during Apollo flights. IMP-A carried instruments designed to measure cosmic rays, the solar wind, and interplanetary magnetic fields beyond the earth's magnetic field. The sphere on top of the boom contained a sensitive magnetometer. Four windmill-like solar panels provided operating power. The satellite was launched on November 26, 1963 aboard a Delta vehicle resulting in a highly elliptical orbit that ranged from 110 to 122,800 miles. Data from the mission led to the discovery of a new layer of radiation beyond the Van Allen belt and confirmed the existence of a standing shock wave in the solar wind around the earth's magnetic field. This object was transferred to NASM by NASA in May 1976.

Collection Item Long Description:

Data Source

National Air and Space Museum

Restrictions & Rights

Do not reproduce without permission from the Smithsonian Institution, National Air and Space Museum

Credit Line

Transferred from the National Aeronautics and Space Administration


Mixed metals, solar cells, electronics


Overall: 4 ft. 5 in. tall x 2 ft. 5 in. wide x 1 ft. 1 in. diameter, 75 lb. (134.62 x 73.66 x 33.02cm, 34kg)

Country of Origin

United States of America



Inventory Number