An automatic polarimeter for space applications

Under a NASA contract, a compact automatic polarimeter was developed as a pilot model for lunar and planetary missions by spacecraft. The polarimeter simultaneously analyzes linearly polarized light into four intensities from which the Stokes parameters I, Q, and U can be determined. The measurements are made automatically by an electronic observation sequencer and an automatic gain selector. Five wavelength bands between 1900 A and 6000A can be used, and each measurement is calibrated automatically. The successful operation during three high altitude balloon flights indicates that the design is sound, and that with modifications for rocket vibration it can be used in space missions. The feature of making simultaneous measurements makes it particularly useful on planetary scans with fly-by probes. Preliminary results on the wavelength dependence of the polarization of the whole lunar disk, obtained ground-based, between 2850 A and 5100 A are presented.