Stokes resolved differential temperature: an important metric of polarimetric precision in the long-wave infrared

Abstract

In remote sensing, radiometric measurements taken in the mid-wave infrared and beyond (λ > 3μm) are commonly reported in units of Kelvin by utilizing Planck's radiation law to relate measured radiance and target brightness temperature (Tb). Thus, it is desirable to match this formalism in thermal polarimetry and report the unnormalized Stokes parameters in units of K instead of radiance (Wm-2sr-1). This approach also allows common performance metrics in long-wave infrared (LWIR) imaging such as Noise Equivalent Differential Temperature (NEDT) to be modified and extended to metrics of polarimetric accuracy and precision. However, since the relationship between measured radiance and Tb are non-linear, the conversion of I, Q, and U in units of radiance to Tb, Tb,Q, and Tb,U in K is ambiguous. As a solution a metric of performance for thermal linear Stokes polarimetry, the Stokes resolved differential temperature (SRDT), is introduced. © 2021 SPIE.