The paper describes a thermal viewer being built at M.R.L. using a line array of 100 InSb, 77°K, 250μ square detector elements. Object plane scanning is used in the horizontal direction only at 20 frames per second, each element scanning one line in the scene. The field of view is 260 mrad. (15°) horizontally and 100 mrad. (6°) vertically. The cell outputs are pre-amplified and multiplexed at 1-5 MHz sampling rate to feed a C.R.T. display. An angular resolution of 1 mrad. and a temperature resolution of 0.3°C are aimed at. © 1968.