Conceptual design and prototyping of a three-color polarimetric imaging instrument for auroral observations

Measurements of the polarization of the aurora remain challenging but would enable the inference of the magnetic field's dynamics and the energetics of the impacting charged particles during geomagnetic storms. Here we present a novel three-color imaging instrument for measuring the polarization of the aurora. The instrument concept is based on a commercial micro-patterned linear polarization camera with Red-Green-Blue color filters. This detector type enables a very compact instrument concept where both the spectral selectivity and the polarization measurement is performed in a snapshot fashion by the imaging chip. We implement additional spectral filters to specifically select the wavelengths of the auroral lines and add a rotating half-wave plate to enhance the polarimetric performance. We have developed a first prototype, called PANIC, to proof the measurement principle. The first observations during a field campaign in Skibotn (Norway) exhibit a sub-percent polarimetric sensitivity and accuracy, rendering the instrument concept viable for routine observations. We discuss future upgrades to improve the instrument stability and its capability to discern auroral signals from other light sources.