ABSTRACT
The light scattering properties of twenty-eight particles, spanning four sizes (near the resonance region) and seven related shapes (a 4:1 cylinder, 4:1 and 2:1 prolate spheroids, a sphere, 2:1 and 4:1 oblate spheroids, and a 4:1 disk), are presented for a common index of refraction, m = 1.61-i0.004, representing silicates. Microwave analog and theoretical methods were used to derive the scattered intensity and degree of polarization as a function of the scattering angle along with the extinction. All results refer to an ensemble or a cloud of identical particles because averages have been taken over random particle orientations. The degree of polarization, backscatter, and the radiation-pressure cross section are most sensitive to particle shape, implying that the use of Mie theory may be inappropriate for many applications.
ABSTRACT
Microwave analog measurements of the forward scattering produced by two spheres yield the extinction as a function of sphere separation for the case of one sphere's being shadowed by the other. The effects of dependent scattering are obvious up to a separation distance of about ten sphere diameters. Side-scattering measurements show a resonance when the axis of the two-sphere system is in the scattering plane and bisects the scattering angle. The magnitude of at least one measured resonance is a factor of 44 larger than the scattering that is due to a single sphere.
ABSTRACT
A photographic coronagraph, built to monitor Skylab's extravehicular contamination, is described. This versatile instrument was used to observe the earth's vertical aerosol distribution and Comet Kohoutek (1973f) near perihelion. Although originally designed for deployment from the solar airlock, the instrument was modified for EVA operation when the airlock was rendered unusable. The results of the observations made in four EVA's were almost completely ruined by the failure of a Skylab operational camera used with the coronagraph. Nevertheless, an aerosol layer at 48 km was discovered in the southern hemisphere from the few useful photographs.
ABSTRACT
Photographs taken with the High Altitude Observatory's White Light Coronagraph (Skylab experiment SO52) are shown to contain information on the sizes and velocities of contaminant particulates around Skylab. Sizes as small as 5 microm (radius) are derived for particles as far away as 200 m from the spacecraft. The random error in the size derivation is about 30%, and no particle larger than 120 microm was observed. Transverse velocities are determined to within 0.08 m sec(-1) and radial velocities to within 9 m sec(-1). The S052 data bank contains about 3500 contaminated frames from which the nature of the Skylab environment can be inferred.
