Measurement of the radiation produced by a hypersonic body during re-entry into the earth's atmosphere is' receiving attention under several experimental programs. Imaging radiometers are applicable to this requirement. This type of instrument provides spacial resolution as necessary for individual measurement of closely spaced multiple point sources and for measurement of line source intensity, gradients. Evaluation of S-10 and S-20 image orthicon tubes, in the radiometric application, has been performed. Quantitative results of test's defining radiometric response, resolution, and calibration stability are described, along with a comparison of S-10 and S-20 capabilities.