This paper discusses the design of a Staring Radiometer to operate principally in the infrared waveband. The basic concepts are that it should incorporate a reflecting optical system of large area and high quality and use the latest digital techniques for both processing and control. Different customer specifications may be easily incorporated due to the modular design. An analysis of instruments made in the past few decades indicates that little redesign or updating has occurred, although PC computers have been added for data reduction purposes. This implies modernisation, making the old hardware look impressive. However, it is the hardware that limits the performance, so this was the area to which we addressed considerable design effort. In the 1960's the Barnes 4" radiometer was developed to quite a high level of sophistication. Discreet filter and circular variable filter wheels were incorporated for spectral analysis and the electronics progressed through the transistor stage into the microcircuit era. However, the optics design is poor, has gross aberrations and by modern standards poor temperature stability. Several other manufacturers have made radiometers but the designs have still not progressed significantly. Customer specification is now outstripping instrument capability.