In order to measure the daytime sky radiation characteristics from 20,000 ft. to 200,000 ft., a spectrophotometer was developed to be operated in two high altitude vehicles. This paper describes the spectrophotometer, the technique of calibration, and reviews the results of the sky measurements from the first Research Vehicle. Data measured included hemispherical sky spectral radiance, luminance, polarization, albedo, and integrated near-infrared from 20,000 ft. to 70,000 ft. Measurements of spectral radiance included from 0.36 through 0.75 microns with a bandwidth of better than 15 nanometers. Data from the second Research Vehicle, the X-15, obtained from 53,000 to 190,000 ft. is presented. Correlation is made with the measurements from the first Research Vehicle as well as with corresponding data available in the literature and with corresponding theoretical sky characteristics.