Re-Entry Radiation from an IRBM

The radiation emitted when a high-speed body reenters the atmosphere is an important source of information concerning the physical processes taking place. Missile firings may be utilized to obtain some of this information. For about two years the Army Ballistic Missile Agency has conducted a measurement program known as Project Gaslight which has utilized Jupiter firings and, to a limited extent, both Thor and Polaris firings also. An account is given of the instrumentation employed and of some of the results that have been obtained. These include radiometric data in several wavelength bands from the ultraviolet to the infrared, and spectra in the visible. Motion pictures provide a record of the spatial relationships of the re-entry bodies, and these results are interpreted in terms of the impulse causing the initial separation. In the case of the Jupiter missile, there are two separations resulting in three bodies, the thrust unit, the nose cone, and an intermediate section or instrument compartment. Selected frames of the motion picture records show these bodies and give a qualitative understanding of the relative radiation from each source, of the disintegration and burning up of the thrust unit and the instrument compartment, and of the markedly lower drag-to-weight ratio of the nose cone. Forward scattering, presumably by high cirrus clouds, is shown to increase considerably the size of the very bright images. Most of the measurements have been made from ships, although some instrumentation has been airborne and photographs have been made from a distant island.