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

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.Corresponding author: Dmitry Vorobiev 2 Vorobiev et al.

Restoration of the K and F Components of the Solar Corona from LASCO-C2 Images over 24 Years [1996 – 2019]

“…The above remarks tend to favor the polarimetric method provided it can be performed at a high spatial resolution and at a high cadence, an improvement that would also benefit to the three-dimensional reconstruction of CMEs based on their polarization. In that respect, advanced techniques as implemented at recent solar eclipses, such as micro-polarizer arrays affixed to the sensor (Burkepile et al,2017;Vorobiev et al 2017) should be considered for future space coronagraphs. This should lead to more photometrically accurate maps of the K-corona as well as of the polarized radiance pB.…”

Thomson Scattering above Solar Active Regions and an Ad Hoc Polarization Correction Method for the Emissive Corona

“…It has radially decreasing intensities, peaking at a few millionths of the disk intensity, and it is linearly polarized with amplitudes of 10%-70%, increasing radially. Eclipse observations by Vorobiev et al (2020) show that K-corona polarization on large spatial scales is oriented tangential to the solar limb, within measurement uncertainties. This is as expected for Thomson scattering of an unpolarized photospheric radiation field that is cylindrically symmetric relative to the radial direction, whereas the presence of symmetrybreaking features like sunspots can induce deviations in the polarization direction, as discussed in this work and by Saint-Hilaire et al (2021).…”

Application of NASA core Flight System to Telescope Control Software for 2017 Total Solar Eclipse Observation

“…Our results therefore demonstrated that DICE is highly effective for the observation of coronal structures such as coronal morphology and polarization degree. Vorobiev et al (2020) observed the 2017 total solar eclipse in Madras, Oregon, using a polarization imaging camera equipped with Bessel B and R filters. They found that the maximum dP was 0.47 near the height of 1.5 solar radius in the eastern streamer.…”