A 4-Megapixel cooled CCD division of focal plane polarimeter for celestial imaging

The field of astronomy relies on spectral and polarization imagery recorded across a wide range of spectra to make inferences about imaged objects from nearby and distant galaxies. One of the challenges in recording celestial polarization information is recording multiple images filtered with various polarization optics, such as linear polarization filters or retarders, and with low-noise, low-dark-current sensors. In this paper, we present a division of focal plane polarimeter that can operate at room temperature down to -20 °C. When the imaging sensor operates at -20 °C, the dark currents is reduced by two orders of magnitude, which improves the polarization extinction ratio by 5-fold. Comprehensive optoelectronic tests are presented with data recorded with the polarimeter.