ABSTRACT Forty especially developed atmospheric -sounding projectiles (ASP) were fired through the clouds resulting from Shots Cherokee, Zuni, Navajo, and Tewa to proof test a system for measuring gammaintensities within the clouds and to explore the spatial distribution of gamma activity within the stem and cloud resulting from the detonation of a nuclear device having a yield in the megaton range. Radiation intensity information was successfully telemeiered out of the radioactive clouds by the ASP rockets and recorded on magnetic tape. Radiation intensities as high as 3 by 10‘ r/hr were encountered within the cloud; intensities at the one measured point in the stem were negligible compared to the peak activity within the cloud. Contamination of rocket surfaces by radioactivity from the cloud did not appear to be of consequence. Total activities in the clouds computed from rocket data agreed in order of magnitude with activities derived from theoretical considerations.