Proposed Observations of Polarization and Interstellar Reddening from above the Ozone with High-Altitude Balloons.

Abstract

view Abstract Citations (4) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Proposed Observations of Polarization and Interstellar Reddening from above the Ozone with High-Altitude Balloons. Gehrels, Thomas Abstract The polarization of Venus, Mars, and the moon increases strongly towards the ultraviolet (Gehrels, Lowell Obs. Bull. 4, 300, 1960), probably due to scattering either by molecules or by very small particles. It is proposed to extend the intercomparison of Venus, Mars, and the moon, with polarization measures down to 2000 A. The earth as a planet, observed from a high-altitude balloon, would also be included in the intercomparison. The wavelength dependences of interstellar reddening (Whitford, Astron. J. 63, 201, 1958) and interstellar polarization (Gehrels, Astron. J. 65, 470, 1960) can be interpreted with the Mie theory, using calculations made by van de Hulst, and particles with diameters of about 0.3 ~ are inferred. However no firm distinction between metallic and dielectric particles has as yet been made. Also, there are conflicting theories that explain the observations in terms of scattering by ions or by particles much smaller than 0.3 ~. Measures at 2200 A, of stars at different galactic longitude, may be decisive because of the peculiar wavelength dependence predicted by the Mie theory. The absorption in the earth's atmosphere between 2000 and 3000 A is due to ozone which, however, is mostly below 110 000 ft altitude (Goldberg, The Earth as a Planet, edited by Kuiper, Chap. 9; Epstein and Adel, Ari~ona State College Rept. HA-9, 1956). The limiting magnitude of our photometer and integrators (Gehrels and Teska, PubIs. Astron. Soc. Pacific 72, 115, 1960) with a 36-inch telescope on the ground is near 14.0 mag. About a dozen fifth- magnitude stars, of early spectral type, would be easily observable with the proposed 8-inch telescope mounted in the gondola wall. Observations at 2200, 2850, and 3250 A are planned for a series of flights above 110 000 feet, using 10~ cu ft balloons. With support from the Office of Naval Research, an orientation flight was made in ~uly 1960, and the photometer is now being modified and tested at 2200 and 2850 A. Publication: The Astronomical Journal Pub Date: 1961 DOI: 10.1086/108489 Bibcode: 1961AJ.....66Q..44G full text sources ADS |