Radio Polarimeter

in radio astronomy, a device for studying the polarization of radiation received by a radio telescope; it measures the intensity of the radiation and the degree and nature of the polarization.

Radiation from cosmic sources is usually weakly polarized (several percent or fractions of a percent). Using antennas equipped with a fixed-dipole feeder or horn feeder, radio telescopes receive that fraction of the radiation that is polarized in the plane determined by the orientation of the feeder; in this case, approximately half of the total radiation intensity of the source is actually measured. A radio telescope can be transformed into a radio polarimeter by rotating the feeder (polarization analyzer) about an axis coinciding with the direction of the antenna’s beam axis. Thus, not only is the intensity of the radiation measured, but also the linear-polarization parameters, that is, the degree and plane of the polarization. However, polarization analysis is more often conducted by measuring the correlation properties of the radiation received by two orthogonally polarized antenna feeders, using a correlation receiver or special modulators in a circular waveguide.