Chapcer ll OPTICAL 2AD LATION AND PSOTOCRAPHIC COVEREE U.1 OBJECTIVES Photographic cowerage on the ground for the Teak aid Orange events was designed to record the time history of wisible radiation. types of coverage vere attempted: Basically, three (1) high-speed framing cameras to record absolute surface brightness in three narrow spectral bands, (2) lensless streak cameras to record irradiance om the ground in three narrow spectral bands, and (3) a spectrographic streak camera to record bomb spectrum versus time. In addition to these, conventional framing cameras using color fila were e=plosed to provide documestary comersge and scpplementary messuremest of the warious fireball dimensions and phenomena at Late tine. Objectives of the photographic coverage were seweral. As indicated t above, the primary purpose was to gather data whica are descriptive of the thermal pulse in quantitative detail. The bearing of this gforuation on the problem of detection of high-altitude bursts is clear. In addition, the information is of interest from the standpoint of weapon effects, e.g., the flash blindness probles. It was furthermore intermled that coverage of optical phenowena should contribute substantially to the general fund of dats pertipent to an understanding of the pbysics of e high-altitude fireball plasaus. Quantitative measurements were needed for this purpose; qualitative information about unexpected phenomena was also sought. 11.2 THEORY The following discussion of fireball phenomenology at high altitude sua- maxrizes, in part, the thinking of others .122 3,445 wv, For brevity, details of calculation are omitted here and only salient resclts are considered. hos at sea level, sofc oy absorbed - within a few meters of the boob, giving rise to a very hot isothermal sphere. o ~ The tesperature is so high that energy radiated is largely in the spectral » 332 SY