Irregular interplanetary dust particles may acquire a considerable spin rate due to two non-statistical dynamical mechanisms induced by solar radiation. These arise from variations in surface albedo as discussed by Radzievskii (1954) and from irregularities in surface geometry as discussed by Paddack (1969). We report on an experiment which will lead to an evaluation in space of the effectiveness of these two spin mechanisms. We utilize the technique of optical levitation in an argon laser beam to provide a stable trap for particles (10-60 microns in diameter). The spin rate and direction of the spin axis are measured in a straightforward manner. The objective is to design an optical trap for dielectric particles in vacuum which can be used to study these rotation mechanisms in the gravity-free environment of a Spacelab experiment.

Experiments designed for the investigation of the near-Earth micrometeoroid flux on the Space Shuttle Long Duration Exposure Facility (LDEF) are described. The paper examines, in particular, how two of the experiments deploy a series of multiple layer foil arrays to investigate the physical properties of incident meteoroids and lead to partial recovery of the micrometeoroids for laboratory analysis. Several thousand penetrations are expected to be returned after 12 months' exposure in Space.

Observations of the Rings of Saturn from the Pioneer spacecraft, discovery of the Ring of Jupiter, ground based polarimetry of the Rings of Saturn and some theoretical studies may be combined to markedly advance our understanding of the Rings of Jupiter, Saturn and Uranus. In particular, narrow rings can be self-gravitatingly stable inside Roche's limit and outside another closer limit. They can be created from a satellite which evolves across its Roche limit either by inward tidal drift or by growth of the planet by accretion.

These considerations suggest that Neptune may well be surrounded by one or more narrow rings like those of Uranus.

In this paper we discuss the motion of charged dust in outer planetary magnetospheres, particularly that of Jupiter. An increase of almost two orders of magnitude in the dust flux was observed as Pioneer 10 approached within about 30 RJ of Jupiter (Humes et al., 1975). Mendis (1978) suggested that this was a result of electrostatic disruption of interplanetary dust entering the Jovian magnetosphere and the subsequent magnetogravitational trapping of the disruption products. Subsequently, we (Hill and Mendis, 1979) have discussed in detail the physical and dynamical processes associated with the entry of interplanetary dust (assumed to be largely fragile aggregates of the Brownlee type) into the Jovian magnetosphere.

Flux measurements of picogram dust particles near the lunar surface and in selenocentric and cis-lunar space made by Lunar Explorer 35, HEOS, and ALSOP dust experiments all indicate, to varying degrees, ejecta from lunar impacts of interplanetary dust particles. The orbits of these submicron particles in the earth-moon system are significantly altered by radiation pressure. Recent orbit calculations show that, in favorable lunar phases, as many as 80% of the ejecta may enter the magnetosphere and 20% may enter the earth's atmosphere. The results of this analysis are presented, and their implications are discussed.

A significant flux of ejecta from lunar impacts of interplanetary dust particles leaves selenocentric space and enters the magnetosphere of the earth. During favorable lunar phases, 80% of the ejecta enter the magnetosphere where their orbits are determined by electrodynamic as well as gravitational forces. Initial study of the orbital characteristics and perturbations of these magnetosphere ejecta is presented and its implications are discussed.