The development of a very versatile, reliable, and sensitive radiometer has provided a tool for performing a variety of significant infrared measurements from ground-based and aircraft platforms in the .8 to 7 pm spectral region. The development techniques of the radiometer, the capabilities of the developed instrument, and some typical target and atmospheric emission measurements are presented in the paper. The instrument design incorporates various techniques to eliminate the need for cooling of the optics and structural parts which avoid the inconveniences and difficulties associated with the operation of cryogenically cooled instruments without significantly sacrificing sensitivity. The radiometer may be used in a selectable spectral wavelength and bandwidth mode, a limited spectral scanning mode, or a tuneable spectral wavelength mode. The various modes of operation are accomplished through the use of interference filters whose spectral characteristics are somewhat adjustable by properly controlling or setting their angular orientation. The simplicity of operation of the instrument has provided a means of measuring atmospheric airglow emissions and aurorally enhanced emissions in the .8 to 1.75 um region on a routine basis. Also, through the use of a reticle chopper and background suppression technique, the same radiometer has been adapted for measurements of low energy target emissions in the .8 to 7 um region.