Observations Of Solar System Bodies Research Articles

Developing Data-driven Artificial Neural Network for a High Throughput Retrieval of Aerosol Optical Depth and Surface Temperature of Mars

In this work, we aim to develop artificial neural network (ANN) techniques to reproduce the retrieval results of physical quantities from spacecraft observations of solar system bodies using radiative transfer methods. The particular application here is the retrieval of dust optical depth, water ice optical depth, and surface temperature on Mars using daytime observations obtained by the Thermal Emission Spectrometer on board the Mars Global Surveyor. Compared against the results obtained from traditional radiative transfer retrieval techniques, our ANN successfully recovered the three quantities using daytime observations. The principal advantage of these machine-learning algorithms is their complete automation and high throughput. Therefore, the algorithms presented here would be useful for very large data sets and would make practical the sampling of many different approximations or boundary conditions related to a given observation data set and retrieval problem.

Astrometric baseline observations of solar system bodies

The use of ground-based and space baseline observations of Solar System bodies is considered. Baseline observations allow one to determine the distance to observed objects and (in some cases) the parameters of their orbital motion. Certain results of baseline observations of near-Earth asteroids and the results of model analysis of spacecraft observations are presented.

Wavelength dependence of linear polarization in the visible and near infrared domain for large levitating grains (PROGRA2 instruments)

Remote sensing measurements of light scattered by dust in solar system objects can provide clues on their physical properties. Databases obtained in the laboratory with numerous samples are necessary to interpret these measurements. We present here first studies of the wavelength dependence of the linear polarization between 545nm and 1.5μm, using the imaging polarimeters PROGRA2 for large levitating compact grains (PROGRA2-VIS in the visible domain, and the new instrument PROGRA2-IR in the near infrared). The measurements are conducted in microgravity conditions during parabolic flights for glass beads, quartz, sands, silicon carbides, anthracite, and lunar and Martian simulants. Comparison between measurements on glass beads and Mie calculations with glass spheres provides an assessment of the quality of the instruments. The dependence of the polarization on the wavelength is related to the complex refractive index of the particles, i.e. to their composition and to the size of the grains. More laboratory measurements will be necessary, in particular with smaller grains in aggregates, to better reproduce the remote sensing observations of solar system bodies.

Experimental studies of ice grain ejection by massive gas flow from ice and implications to Comets, Triton and Mars

This is an experimental study of ice grain ejection when trapped gases are released from water ice. When ice is formed by adherence of water molecules at low temperatures, it forms an amorphous structure with many pores, where gas molecules can reside. When further ice layers are formed, the gases are trapped in the ice. Upon its warming-up, the ice structure changes, releasing fractions of the trapped gas. If they do not encounter obstacles, they are released quiescently by dynamic percolation. In a non-dense ice a huge flux of ice grains emanates from the ice, propelled by gas jets and covering its entire surface. When the overlying ice is denser, due to back-migration of water vapor during its sublimation, gas trying to escape from below cannot penetrate the dense ice and breaks it, producing non-circular craters and a chaotic terrain, as observed experimentally and in close encounters with Comets Wild 2, Tempel 1 and Hartley 2. These experimental findings explain several observations of Solar System bodies: ice grain ejection from Comets Temple 1 and Hartley 2. Also explained are the dark jets observed on Triton, where their ejection speed suggests a deep source. On Mars, dark streaks are observed in the southern pole in spring, most likely by plumes carrying dark dust, carried by winds and falling on the surface. As found by us experimentally, only frozen CO2 covered by water ice or mixed with it will work to form jets, whereas pure frozen CO2 will sublimate quiescently.

The accuracy of observations of the Galilean satellites of Jupiter taken at the Abastumani Astrophysical Observatory of the Academy of Sciences of Georgia

The sets of photographic observations of the Galilean satellites of Jupiter taken at the Abastumani Astrophysical Observatory of the Academy of Sciences of Georgia are analyzed here. Positional observations of the system of Jupiter were made in the period from 1985 to 1994 with the use of the double Zeiss astrograph in order to determine the exact coordinates of Jupiter and its satellites. The accurate positions of the satellites and Jupiter itself, as well as their stellar (equatorial) coordinates relative to the stars of the currently available catalogs and the relative “satellite — satellite” coordinates were obtained from the observations. From the comparison of the observation results with the modern theories of motion of satellites, the accuracy in determining the positions of the satellites and Jupiter was analyzed. The results of observations are presented in the Pulkovo database of observations of Solar System bodies that is accessible to users at http://www.puldb.ru.

Astrometric and photometric observations of solar system bodies with Pulkovo Observatory’s automatic mirror astrograph ZA-320M

A brief description of the process of astrometric and photometric observations and their processing by an automatic complex, based on Pulkovo Observatory’s ZA-320M telescope, is presented. The basic results of astrometric and photometric observations of Solar System bodies obtained during 1997–2007 are given. They include, in particular, the results of astrometric observations of dangerous objects ( Near Earth Objects — NEOs), as well as the results of astrometric observations of the Pluto-Charon system. In addition, the paper presents the results of photometric observations of planetary satellites, the mutual phenomena in the system of Jupiter’s satellites, and the 2559 star occultation by the (111) Ate asteroid from the HIPPARCOS catalogue.

Photometric observations of solar system bodies with ZA-320M automatic mirror astrograph in Pulkovo observatory

A short description of the Pulkovo ZA-320M automatic mirror astrograph and program package developed for this instrument is given in this paper. The results of the photometric observations of mutual phenomena of the Galilean satellites in 1997 (three phenomena) and 2002–2003 (24 phenomena) with the instrument are shown. The method of interpretation of the observations is described. The results of the photometric observations of occultation of the star (HIP 2559) by the asteroid (111) Ate are also shown. Our estimation of its chord taken part in the occultation is 125.6 ± 7.2 km .

The observations of Near Earth Objects by the automatic mirror astrograph ZA–320M at Pulkovo observatory

AbstractAt Pulkovo Observatory, we conduct observations of various Solar System bodies: major planets, their satellites, comets, and asteroids, including Near Earth Objects. For these purposes, a robotic telescope was constructed on the base of the ZA–320 Mirror Astrograph (D=320 mm, F=3200 mm). It can perform CCD observations of Solar System bodies with the limiting magnitude of up to 19.0.Independent ephemeris support is provided by the EPOS software package developed at Pulkovo Observatory; it includes tracing of catalogues of comets and asteroids, regular ephemeris calculations, and control of observations. CCD frame processing is done by the Apex automatic data reduction package developed at Pulkovo Observatory.In 2001-2006, more than 12000 observations of minor Solar System bodies were collected, including more than 6000 positions of 656 NEAs, about 1200 observations of 27 comets, and about 2000 observations of major planets satellites. The mean accuracy of obtained positions is 0″.09−0″.40. Results of observations are regularly submitted to the Minor Planet Center.Currently, ZA–320M is the 16-th of more than 680 telescopes in the worldwide rating of those that observe NEAs (by the number of observations).In the near future, our group is planning to start observations with another two robotic telescopes: MTM–500 (D=500 mm, F=4000 mm Maksutov) and 1-meter telescope (D=1000 mm, F=1200 mm) of the Pulkovo mountain station at Northern Caucasus (Kislovodsk, 2100 m above sea level). These two instruments will allow to increase the number of observations, their accuracy, and limiting magnitude (up to 20.5 mag).

Photographic observations of solar system bodies at the Engelhardt astronomical observatory

We describe a large database of photographic observations of Solar System bodies obtained at the Engelhadt Astronomical Observatory (EnAO). We give a brief description of the methods of observations and the accuracy of their reduction with the PPM and Tycho-2 catalogues. The photographic positions of the major planets, except Jupiter, are in the system of the Tycho-2 catalogue and their comparison with DE200 ephemeris coordinates are given.

Solar system observations with Spitzer Space Telescope: Preliminary results

The programs of observations of Solar System bodies conducted in the first year of the operation of the Spitzer Space Telescope as part of the Guaranteed Observing Time allocations are described. Initial results include the determination of the geometric albedos of a number of Kuiper Belt objects and Centaurs from observations of their flux densities at 24 and 70 μm, and the detection of emission bands in the spectra of several distant asteroids (Trojans) around 10 and 25 μm. The 10 Kuiper Belt objects observed to date have geometric albedos in the range 0.08–0.15, significantly higher than the earlier estimated 0.04. An additional KBO [(55565) 2002 AW 197] has a geometric albedo of 0.17 ± 0.03. The emission bands in the asteroid spectra are indicative of silicates, but specific minerals have not yet been identified. The Centaur/comet 29P/Schwassmann–Wachmann 1 has a nucleus surface geometric albedo of 0.025 ± 0.01 and its dust production rate was calculated from the properties of the coma. Several other investigations are in progress as the incoming data are processed and analyzed.

Solar system science with SKA

Radio wavelength observations of solar system bodies reveal unique information about them, as they probe to regions inaccessible by nearly all other remote sensing techniques and wavelengths. As such, the SKA will be an important telescope for planetary science studies. With its sensitivity, spatial resolution, and spectral flexibility and resolution, it will be used extensively in planetary studies. It will make significant advances possible in studies of the deep atmospheres, magnetospheres and rings of the giant planets, atmospheres, surfaces, and subsurfaces of the terrestrial planets, and properties of small bodies, including comets, asteroids, and KBOs. Further, it will allow unique studies of the Sun. Finally, it will allow for both indirect and direct observations of extrasolar giant planets.

Laboratory light scattering measurements on “natural” particles with the PROGRA 2 experiment: an overview

Polarimetric phase curves were obtained with the PROGRA 2 instrument for different particles: glass beads, polyhedral solids, rough particles, dense aggregates and aggregates with porosity higher than 90%. The main purpose of these measurements is to build a large database, which allows interpreting remote sensing observations of solar system bodies. For some samples numerical or experimental models (i.e. DDA, stochastically built particles, microwave analogue) and laboratory experiments are compared to better disentangle the involved physical properties. This paper gives some main results of the experiment, and their applications to Earth atmosphere, comets and asteroids.

ERA: Knowledge Base for Ephemeris and Dynamical Astronomy

AbstractA brief description of a problem-oriented language SLON for ephemeris and dynamical astronomy and a corresponding programming system ERA is given. In the frame of the system the user has easy access to an embedded universal program package to process high precision positional observations of Solar system bodies as well as of artificial Earth satellites.

Meridian observations of solar system bodies with the struveertel instruments of the Pulkovo Observatory

Two Struve-Ertel instruments were used for the daytime observations of the Sun, Mercury, Venus and Mars at Pulkovo from 1956 to 1976. The FK4 equinox and equator corrections were derived. Both the instruments were installed in 1983–1986 at the Kislovodsk Station of the Pulkovo Observatory. The atmospheric dispersion and lateral refraction have been estimated at the Station.

Comparison of Instruments and Methods of Positional Observations of the Sun and Major Planets

During the last decades, regular meridian observations of the Sun and major planets have been mainly carried out at Washington and Greenwich observatories. However, after 1960 position observations of Solar system bodies were initiated at many observatories throughout the world. The photographic and the equal altitude methods are widely used at this time, besides the meridian method. According to available information, during the time interval from 1960 to 1980,altogether 19 meridian instruments, 12 astrographs and 5 astrolabes took part in observations of the Sun and the major planets. More than 40.000 observations of single coordinates - right ascension and declinations have been obtained.