The Wavelength Dependence of Polarization

Abstract

Preliminary results are described of a program of polarimetry and photometry. Astronomical telescopes and a differential polarimeter are used with calibration by a Lyot depolarizer. The wide-band filters have effective wavelengths between 3250 Å and 9900 Å. The problems of instrumental polarization and depolarization are discussed; most of the instrumental effects can be avoided by proper aluminization of the telescope mirrors. The multiple molecular scattering of the sunlit sky and of the poles of Jupiter is closely represented by the Rayleigh-Chandrasekhar theory; the optical depth at the Jovian poles is 0.4–0.8. The same particle sizes that explain the interstellar reddening, 0.05–0.3 μ, are found from the interstellar polarization. Strong polarization-wavelength dependence is found for Venus and for lunar regions, but the detailed explanations require extension of the wavelength range. The range of wavelengths will be extended by using high-altitude balloons and spacecraft.