Engineering topics
Publications and source records attributed to Dollfus, A..
Fifty-four new names introduced for features on Venus. Parga Chasmata (term in plural) name is used for the broad zone of canyons. Prominent features within it obtained individual names. Web Gazetteer provides now name search along 9 parameters. Additional information is contained in the original extended abstract.
12 names assigned on Venus in 2000. The current list includes 1821 names of 21 feature types. 95% of names present 11 types of features. The main named types are craters - 872, and coronae - 267. These two types possess 62% of the names. Additional information is contained in the original extended abstract.
Sixty-five features of 13 different types were named on Venus in 1999. Eleven of the names are in the Northern hemisphere, and 54 are in Southern hemisphere to support the NASA program of Venus geologic mapping at 1:5,000,000 scale after the Magellan Synthetic Aperture Radar (SAR) image data.
The survey of Ma'adim Vallis and crater Gusev area by the new topographic Aeolis southeast map allows to document the hydrodynamics processes which occurred in the valley. The inner Ma'adim Vallis hypsometric and volume deposits analyses point out that Gusev impact was subsequent to the first incision of Ma'adim Vallis in the craterized upland. The study of the deposit distributions as revealed by the topography leads to reconstruct the chronology of three major events in the Aeolis Region : Ma'adim incision, Gusev impact, and Apollinaris Patera/flow interactions.
Telescopic optical polarimetry over the planet Mars enables us to detect and localize scatterers in the Martian atmosphere. Polarization discriminates between crystal clouds and dust particles. For dust grains, sizes can be derived. There is an increase in size from very small grains forming the permanent dust haze to sub-micrometer size grains for the local dust veils and the several micrometer size pieces found in the dust storm clouds. From all these polarimetric results, an overview emerges about the behavior of dust particles in the Martian atmosphere.
The microtexture of the near-surface Martian soil was sensed with three diagnostic parameters: (1) the albedo A at normal incidence and phase angle 5 degrees, which relates to the composition of the top surface exposed layer; (2) the polarization parameter b characterizes the texture of the top surface layer in terms of grain size; and (3) the thermal inertia parameter I which refers to the soil compaction through the first few decimeters below the top surface sensed by polarimetry, in terms of size for the pieces making a granular regolith. Parameter b was derived from instrument VPM on board the Soviet spacecraft MARS-5, inertial I is from IRTM on the American Viking, and albedo A from both. The polarimetric scans racked strips covering two contrasted regions, the dark hued Mare Erythraeum, and the adjacent bright orange Thaumasia. Erythraem is characterized everywhere by a same type of terrain, despite the large geomorphological diversity of the surface. There is an ubiquitous coating or mantling with small dark grains, of both albedo 12.7 percent and particle size 10 to 20 microns, above a subsurface dislocation in pieces around 300 to 600 microns. A simple model is with sand-size particles completely coated with 15 micron dark grains.
The Solar Birefringent Filter (Filter Polarisiant Solaire Selectif FPSS) of Meudon Observatory is presently located at the focus of a solar refractor with a 28 cm lens directly pointed at the Sun. It produces a diffraction limited image without instrumental polarization and with a spectral resolution of 46,000 in a field of 6 arc min. diameter. The instrument is calibrated for absolute Doppler velocity measurements and is presently used for quantitative imagery of the radial velocity motions in the photosphere. The short period oscillations are recorded. Work of adapting the instrument for the imagery of the solar surface in the Stokes parameters is discussed. The first polarizer of the birefringent filter, with a reference position angle 0 deg, is associated with a fixed quarter wave plate at +45 deg. A rotating quarter wave plate is set at 0 deg and can be turned by incremented steps of exactly +45 deg. Another quarter wave plate also initially set at 0 deg is simultaneously incremented by -45 deg but only on each even step of the first plate. A complete cycle of increments produces images for each of the 6 parameters I + or - Q, I + or - U and I + or - V. These images are then subtracted by pairs to produce a full image in the three Stokes parameters Q, U and V. With proper retardation tolerance and positioning accuracy of the quarter wave plates, the cross talk between the Stokes parameters was calculated and checked to be minimal.
Interpretations of astronomical polarization data for more than 100 minor planets are summarized with reference to laboratory data for lunar, meteoritic, and terrestrial samples. All observed asteroids, including objects only a few kilometers in diameter, have microscopically intricate surfaces. Detailed comparisons between laboratory measurements of basaltic achondrites and telescopic results for Vesta show that its surface is particulate with a broad range of particle sizes, including a component of fine (1-5 micron) dust. The surface soils have not, however, undergone marked optical alterations as is the case for the lunar fines. For albedos greater than about 0.06, the albedo and hence the diameter can be determined with some reliability from the slope of the ascending branch of the polarization-phase curve. Many minor planets have surfaces that are remarkably uniform in albedo and texture on a hemispheric scale. A notable exception is 4 Vesta, which shows about ten percent albedo variegation between hemispheres.
The International Astronomical Union has endorsed a nomenclature for the albedo features on Mercury. Designations are based upon the mythological names related to the god Hermes; they are expressed in Latin form. The dark-hued albedo features are associated with the generic term Solitudo. The light-hued areas are designated by a single name without generic term. The 32 names adopted are allocated on the Mercury map.
Laboratory reflection polarimetry is presented for crushed rocks, lunar soils, and 24 meteoritic samples. The polarization-phase curves found for the meteorites closely resemble telescopic results for minor planets, but only if the samples are crushed finely enough to coat the larger particles with dust. The results generally confirm the identifications previously made from reflection spectroscopy for the meteoritic analogues of various types of asteroids; the more metal-rich ordinary chondrites, for example, match telescopic observations of the S-type minor planets well enough, as do the basaltic achondrites for Vesta. No meteorite measured, however, has a geometric albedo less than 0.05 as required for many of the C asteroids. A calibration of the polarimetric slope-albedo law, now determined strictly for meteoritic samples, confirms the asteroid albedo and diameter scale derived by the independent method of thermal radiometry.
A new nomenclature for Martian regions and topographic features uncovered by Mariner 9, as officially adopted by the International Astronomical Union, is described. About 180 craters generally of diameters greater than 100 km have been named, as well as 13 classes of topographic features designated catena, chasma, dorsum, fossa, labyrinthus, mensa, mons, patera, planitia, planum, tholus, vallis, and vastitas. In addition seven craters and the Kepler Dorsum are named on Phobos, and two craters on Deimos. Coordinates and maps of each named feature are displayed.
Polarimetric properties were determined for the L-16-19-1-116 samples, weighing 0.087 g. The measurements were made for five wavelengths between 3540 and 5850 AU. In addition, the normal albedo was determined for each of these wavelengths. The albedo for the measured sample was slightly lower than for the typical material of the dark lunar maria and in addition, there was a well developed branch of negative polarization, which resembles the branch obtained for carbonaceous chondrites crushed into powder, and the branch obtained for the powders of several terrestrial basaltic and ultrabasic rocks.
Polarization measurements with a telescope for the degree of polarization of light reflected by planetary surfaces, and comparative measurement of terrestrial minerals, meteorites, and returned lunar samples are reported. The polarization curve plots of the dependence of the degree of polarization on the phase angle V are plotted and compared with each other to determine the optical characteristics of the planetary surfaces.
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Far side lunar craters nomenclature, listing names with identifying biographical data
Apollo 11 lunar fines, rocks and breccias luminescence, electron paramagnetic resonance and optical properties, discussing reflection spectra, heating effects and dipole resonance
Water content of Venus atmosphere, aerosols, and pressure in upper cloud layer, and deviations in direction of polarized light
Water content and diffusion in Martian atmosphere and properties of light and dark sides of Martian soil