FON DUSHANBE CATALOGUE. RESULTS OF PROCESSING IN THE TYCHO-2 SYSTEM

In the Tycho-2 catalogue system the processing of 1529 photographic plates of the FON Dushanbe project from the collection of the Institute of Astrophysics of the National Academy of Sciences of Tajikistan was completed. The photographic plates with the size of 8º×8º (30x30 cm) were exposed in the zones from -8º to + 84º in the period of 1985-1992 years. In years 2017 – 2020 the plates were digitized using a Microtek ScanMaker 1000XL Plus scanner with the resolution of 1200 dpi, so the size of the digitized images is near 13000x13000 px. Based on the results of the processing of digitized images a catalogue of equatorial coordinates α, δ and B-magnitudes of stars for the northern hemisphere of the sky was created. The catalog contains about 30 million stars and galaxies for the epoch 1988.74. The average internal accuracy of the catalogue for all objects is σαδ = ±0.32" and σB = ± 0.11 m (for stars in the range of B = 8 m -14 m the errors are σαδ = ±0.19" and σB =±0.07 m ) for equatorial coordinates and B-magnitudes respectively. The convergence between calculated and reference positions from the Tycho-2 catalogue is σαδ = ±0.07" and the convergence with photoelectric B-magnitudes is σB = ±0.16 m . Five astronomical institutions took part in the processing of the photographic plates and in the creating of the FON-Dushanbe catalogue: Institute of Astrophysics of NAS of Tajikistan; Walter Hohmann Observatory, Essen, Germany; Ulugh Beg Astronomical Institute UAS, Uzbekistan; Research Institute “Mykolaiv Astronomical Observatory”, Ukraine and Main Astronomical Observatory NASU, Ukraine.

Seven years of monthly low-degree gravity field models from Swarm GPS data

<p>The Swarm satellite constellation provides GPS data with sufficient accuracy to observe the large-scale mass transport processes occurring at the Earth’s surface since 2013. We illustrate the signal content of the time series of monthly gravity field models. The models are published on quarterly basis and are the result of a combination of the individual models produced by different gravity field estimation approaches, by the Astronomical Institute of the University of Bern, the Astronomical Institute of the Czech Academy of Sciences, the Institute of Geodesy of the Graz University of Technology and the School of Earth Sciences of the Ohio State University. We combine the models at the solution level, using weights derived from a Variance Component Estimation, under the framework of the International Combination Service for Time-variable Gravity Fields (COST-G).</p><p> </p><p>We estimate the monthly quality of the models by comparing with GRACE and GRACE-FO products and illustrate the improvement of the combined model as compared to the individual models. We present the high signal-to-noise ratio of this uninterrupted time series of models, smoothed to 750km radius, over large hydrological basins. Finally, we compare the behavior of degree 2 and 3 coefficients with GRACE/GRACE-FO and SLR.</p>

Alexander Nikolaevich Deutsch on the occasion of his 120th anniversary

The year 2019 is the year of the 120th anniversary of Alexander Nikolaevich Deutsch (1899-1986), the Pulkovo astronomer, doctor of physical and mathematical Sciences, Professor, who for many years was the head of the Department of photographic astrometry and stellar astronomy of the Main Astronomical Observatory, Russian Academy of Sciences (GAO RAS), the supervisor and teacher of several generations of Pulkovo astronomers and employees of other observatories. This article presents the scientific and social activities of A.N. Deutsch. Archived data is provided that evidence his participation, along with other Pulkovo employees, in the salvation of the property and scientific Fund of the Pulkovo Observatory during the great Patriotic war, as well as in the work to restore the Observatory. The article is based on the presentation given to and approved by the conference "Astrometry: yesterday, today, tomorrow" (Sternberg Astronomical Institute, Moscow State University, October 14-16, 2019).

Creation of a new global geomorphological catalog of Mercury’s craters based on the latest MESSENGER data

<p>Catalogs of impact craters – not only a layers of objects in GIS but complete databases containing the morphometric and geomorphological characteristics – can help to solve such fundamental problems as the estimation of parameters of populations of impactors that collided with the surface of the planet throughout its history, as well as to clarify the processes of crater formation in the Solar System.</p><p>Currently, there are few global catalogues of Mercury that includes big craters only. For example: 1) global digital GIS-catalogue of Mercury’s craters created by the Braun University, USA. It is based on modern data gathered by MESSENGER and, along with approximately 9000 objects; it includes coordinates and diameters of large craters (> 20 km), exclusively. At the same time, it doesn’t contain any geomorphological information; 2) the other source is a geomorphological catalogue that was composed by Sternberg Astronomical Institute (SAI), which, while containing geomorphological information, was created in accordance to data of Mariner 10 and was presented as a text in a table. The SAI’s catalogue includes craters with a size of 10 km and larger. </p><p>Creation of a new global catalog of Mercury’s craters based on the latest MESSENGER data is a comprehensive work. The catalog will consist of two subdirectories: 1) the geomorphological catalog of craters with a size of 10 km and larger; 2) the morphometric catalog of craters with a size less than 10 km. We use MESSENGER MDIS global mosaic of Mercury with resolution ~166 m/pixel and several MESSENGER DEMs – the first global Mercury DEM with resolution 665 m/pixel and four DEMs on Mercury quadrants with resolution ~222 m/pixel (which will be used for formation of a database of craters with diameters less than 10 km).</p><p>In addition to the required elements of any catalog (coordinates of craters and their diameters), we will be able to add full geomorphological description of craters, reduced to code designations (to simplify the implementation of the catalog in the GIS) and morphometric characteristics. For instance: 1) the diameter of the interior feature (flat floor, central peak, or inner ring); 2) depth and relative depth of each crater; 3) max and min slopes; 4) the average level of inclination of the external; 5) internal slopes of crater; 6) the ratio of volume of the crater rim to the volume of the bowl. The most of listed parameters can be calculated both for craters and for the surrounding surface.</p><p>By using this catalog, we will be able to quickly get statistics and create thematic maps, for example, maps of crater density on regions of interest.</p><p>This research was supported by Russian Foundation for Basic Research (RFBR), project No 20-35-70019.</p>