Imaging Polarimetry of the 2017 Solar Eclipse with the RIT Polarization Imaging Camera

TL;DR

This paper evaluates the performance of micropolarizer-based imaging polarimeters, specifically the RIT Polarization Imaging Camera, for astronomical observations, demonstrating their capability to detect low polarization signals during the 2017 solar eclipse.

Contribution

It introduces the RIT Polarization Imaging Camera for astronomical use, characterizes its performance, and demonstrates its application in solar eclipse polarimetry.

Findings

Capable of detecting polarization signals as small as <0.3%

Measured maximum polarization of ~46% during eclipse

Calibration remains stable and the system is highly portable

Abstract

In the last decade, imaging polarimeters based on micropolarizer arrays have been developed for use in terrestrial remote sensing and metrology applications. Micropolarizer-based sensors are dramatically smaller and more mechanically robust than other polarimeters with similar spectral response and snapshot capability. To determine the suitability of these new polarimeters for astronomical applications, we developed the RIT Polarization Imaging Camera to investigate the performance of these devices, with a special attention to the low signal-to-noise regime. We characterized the device performance in the lab, by determining the relative throughput, efficiency, and orientation of every pixel, as a function of wavelength. Using the resulting pixel response model, we developed demodulation procedures for aperture photometry and imaging polarimetry observing modes. We found that, using the current calibration, RITPIC is capable of detecting polarization signals as small as <0.3%. To demonstrate the stability of RITPIC's calibration and its extreme portability, we performed imaging polarimetry of the Solar corona in Madras, Oregon during the total Solar eclipse of 2017. The maximum polarization we measured was ~46%, which agrees well with the maximum value predicted for a Thomson scattering corona. Similarly, we found no strong deviations in the angle of linear polarization from the tangential direction. The relative ease of data collection, calibration, and analysis provided by these sensors suggest than they may become an important tool for a number of astronomical targets.