Imaging Polarimetry of Geostationary Satellite Express-AM5

This paper reports on the optical imaging polarimetry of geostationary satellite Express-AM5.Precise optical polarimetry was carried out using the Nayuta 2-m telescope at Nishi-Harima Astronomical Observatory and a polarimeter. V-band images were continuously taken in 312 minutes. The degree of polarization decreased with time until the minimum phase angle was reached at midnight, and then, it increased until morning. This change in the degree of polarization is well explained by the reflection of sunlight from monocrystalline solar panels of the satellite and possibly from other satellite components such as the antenna dishes and/or bus.