Layer Of Dust Particles Research Articles

Dust mitigation technology for lunar exploration utilizing an electron beam

Dust mobilized on the lunar surface due to natural processes and/or human activities can readily stick to spacesuits, optical devices, and mechanical components, for example. This may lead to dust hazards that have been considered as one of the technical challenges for future lunar exploration. Several dust mitigation technologies have been investigated over the past years. Here we present a new method utilizing an electron beam to shed dust off of surfaces. Recent studies on electrostatic dust lofting have shown that the emission and absorption of secondary electrons or photoelectrons inside microcavities forming between dust particles can cause the buildup of substantial negative charges on the surrounding particles. The subsequent repulsive forces between these particles can cause their release from the surface. Fine-sized lunar simulant particles (JSC-1A, <25 μm in diameter) are used in our experiments. The cleaning performance is tested against the electron beam energy and current density, the surface material, as well as thickness of the initial dust layer. It is shown that the overall cleanliness can reach 75–85% on the timescale of ~100 s with the optimized electron beam parameters (~230 eV and minimum current density between 1.5 and 3 μA/cm2), depending on the thickness of the initial dust layer. The maximum cleanliness is found to be similar between a spacesuit sample and a glass surface. Future work will be focused on removal of the last layer of dust particles and an alternative method using ultraviolet (UV) light.

Determining the Threshold of Detection of a Minimal Specific Weight of Particles in the Study of Shock-Wave Dusting of Surfaces of Materials

Particles are discharged from surfaces of materials under a shock-wave load. Experimental results on determining the minimal values of a specific weight of particles with which their velocity can be detected using a heterodyne interferometer [photon Doppler velocimetry (PDV) method] are presented. An effect of multiple frequency shift of a Doppler signal in the case of laser radiation being reflected from surfaces of materials and a semitransparent layer of dust particles is described.

Laboratory light scattering from regolith surface and simulation of data by Hapke model

The small atmosphereless objects of our solar system, such as asteroids and the moon, are covered by layer of dust particles known as regolith, formed by meteoritic impact. The light scattering studies of such dust layer by laboratory experiment and numerical simulation are two important tools to investigate their physical properties. In the present work, the light scattered from a layer of dust particles, containing 0.3μm Al2O3 at wavelength 632.8nm, is analysed. This work has been performed by using a light scattering instrument ‘ellipsometer’, at the Department of Physics, Assam University, Silchar, India. Through this experiment, we generated in laboratory the photometric and polarimetric phase curves of light scattered from such a layer. In order to numerically simulate this data, we used Hapke׳s model combined with Mie׳s single particle scattering properties. The perpendicular and parallel components of single particle albedo and the phase function were derived from Mie theory. By using Hapke׳s model combined with Mie theory, the physical properties of the dust grain such as grain size, optical constant (n,k) and wavelength can be studied through this scheme. In the literature, till today no theoretical model to represent polarisation caused due to scattering from rough surface is available, which can successfully explain the scattering process. So the main objective of this work is to develop a model which can theoretically estimate polarisation as caused due to scattering from rough surface and also to validate our model with the laboratory data generated in the present work.

Nonlinear acoustic-gravity waves and dust particle redistribution in earth's atmosphere

A continuously stratified model of nonadiabatic terrestrial atmosphere with taking into account the temperature profile is developed to study a possibility of instability development of acoustic-gravity (AG-) waves. It is shown that the existence of the regions in the atmosphere where the instability conditions are satisfied is due to the cooperation of thermal flow of solar radiation, infrared emission of the atmosphere, water vapor condensation, as well as thermal conductivity. Large-amplitude vortices in Earth's troposphere and ionosphere and their possible structure as well as redistribution of dust particles in the ionosphere as a result of vortical motions are discussed. The following possibilities for the dust particle redistribution are studied: capture and evolution of dust particles in AG-vortices, formation of dust vortices as a result of involving a great number of dust particles into vortex motions, and formation of vertical and horizontal dust flows (streamers and zonal flows). It is shown that excitation of AG-vortices at the ionospheric altitudes as a result of development of AG-wave instability leads to a substantial transportation of dust particles and their mixing. Layers of dust particles with a thickness of about a kilometer, forming at the altitudes less than 120km, distribute within the region of the existence of AG-vortical structures. As a result, at altitudes of 110–120km, dust vortices can appear, and transportation of particles up to altitudes of 130km becomes possible. One of the ways of transportation of dust particles in the ionosphere is dust flows, which are generated by dust vortices as a result of development of parametric instability.

Effects of layers of different dust particles on propagation characteristics of millimeter wave

In the present paper theoretical investigation has been carried out to evaluate the effect of layers of different shapes of dust particles (ellipsoidal and spheroidal) on the propagation of millimeter wave. For this purpose a length of communication link has been considered, which contains layers of dust particles blown to the height of the link due to dust storms. Further, each layer of dust particles has been assumed as a section of transmission line and entire link as number of transmission line sections in a cascade. Hence using the concept of transmission line the reflection coefficient, transmission coefficient and absorption loss have been calculated. It is found that propagation parameters depend on frequency and visibility. Brewster’s phenomenon is clearly observed by the system which is at around 75° of angle of incidence.

Vortex motions and transportation of fine disperse dust particles in the ionosphere

Redistribution of dust particles in the ionosphere as a result of vortical motions is discussed. The following possibilities are studied: capture and evolution of dust particles in acoustic-gravitational (AG) vortices, formation of dust vortices as a result of involving a great number of dust particles into vortex motions, and formation of vertical dust flows (streamers). It is shown that excitation of AG-vortices at altitudes of 110–130 km as a result of development of AG-wave instability, associated with non-zero balance of heat fluxes, owing to solar radiation, water vapors condensation, infrared emission of the atmosphere, and thermal conductivity, leads to a substantial transportation of dust particles and their mixing at altitudes of 110–120 km. Layers of dust particles in the ionosphere with a thickness of about a kilometer, forming at altitudes less than 120 km, distribute within the region of existence of AG-vortical structures. As a result, at altitudes of 110–120 km, dust vortices can appear, and transportation of particles up to altitudes of 130 km becomes possible. One of the ways of transportation of dust particles in the ionosphere is vertical flows (streamers), which are generated by dust vortices as a result of development of parametric instability.