Mid-wave and long-wave infrared polarimetric phenomenology sensors

This paper describes two sensors built on existing Nichols polarimetric sensor designs that provide Stokes four-vector polarimetric data on static targets. The midwave infrared (MWIR) sensor uses a Raytheon-Amber AE-173 indium antimonide (InSb) 256×256 focal plane array to provide data in the 3-5 micron waveband. The long-wave infrared (LWIR) sensor uses a Raytheon-Amber AE-173 mercury cadmium telluride (MCT) 256×256 focal plane array to provide data in the 8-10 micron waveband. To the extent possible, these sensors have been designed to use the same mechanical, optical, and electronics hardware. Each sensor uses a custom closed-cycle dewar, which contains the focal plane and an optics package, maintained at a constant temperature. The optics package contains a motorized eight-position filter wheel, a linear polarizer, and a motorized rotating 1/4 λ waveplate. A warm 100 mm F#2 refractive telescope is external to the dewar. A customized set of electronics is used to control the sensor and acquire and process the polarimetric image data in near real-time