MEASUREMENTS  OF IMPORTANT  VARIABLES   OF  THE NIGHT SKY

Three important variables of the night sky were measured.

(1). An automatic night sky radiometer designed and constructed at SRDE was used to measure the illumination levels in the wavebands 0.8-1.0 and 1.0-1.3 micron bands using a photomultiplier and a lead sulphide cell as the detectors.

(2). Photographs were taken of the appearance of a scene at visible and infrared wavelengths. A closed circuit TV system with an infrared-sensitive vidicon showed the appearance of the scene outside beween 0.75 and 0.9 microns.

(3). A transmissometer designed at SRDE was used to automatically measure the atmospheric transmisson at 0.9 microns over a path length of 100metres. A contrast radiometer was designed to automatically measure the forward scattering or luminance of the atmosphere enabling the brightness of up to six targets of known reflectivity to be measured at ranges out to 1,000 metres. The measurements of transmission and brightness showed the atmospheric limitations of night vision devices.