scholarly journals Photometry and shape modeling of Mars crosser asteroid (1011) Laodamia

2014 ◽  
pp. 79-85 ◽  
Author(s):  
G. Apostolovska ◽  
Z. Donchev ◽  
A. Kostov ◽  
V. Ivanova ◽  
G. Borisov ◽  
...  
Keyword(s):  
Sparse Data ◽  
Astronomical Observatory ◽  
Shape Modeling ◽  
Inversion Method ◽  
Shape Parameters ◽  
Spin Vector ◽  
Shape Model ◽  
Photometric Observations ◽  
Vector Sense

An analysis of photometric observations of Mars crosser asteroid 1011 Laodamia conducted at Bulgarian National Astronomical Observatory Rozhen over a twelve year interval (2002, 2003, 2004, 2006, 2007, 2008, 2011, 2012 and 2013) is made. Based on the obtained lightcurves the spin vector, sense of rotation, and preliminary shape model of (1011) Laodamia have been determined using the lightcurve inversion method. The aim of this investigation is to increase the set of asteroids with known spin and shape parameters and to contribute in improving the model in combination with other techniques and sparse data produced by photometric asteroid surveys such as Pan-STARRS or GAIA.

Shape and spin of asteroid 967 Helionape

2017 ◽  
Vol 12 (S330) ◽  
pp. 393-394
Author(s):  
G. Apostolovska ◽  
A. Kostov ◽  
Z. Donchev ◽  
E. Vchkova Bebekovska ◽  
O. Kuzmanovska
Keyword(s):  
Family Member ◽  
Planetary System ◽  
Sparse Data ◽  
Astronomical Observatory ◽  
Inversion Method ◽  
Shape Parameters ◽  
Spin Vector ◽  
Main Belt ◽  
Shape Model ◽  
Geometric Conditions

AbstractKnowledge of the spin and shape parameters of the asteroids is very important for understanding of the conditions during the creation of our planetary system and formation of asteroid populations. The main belt asteroid and Flora family member 967 Helionape was observed during five apparitions. The observations were made at the Bulgarian National Astronomical Observatory (BNAO) Rozhen, since March 2006 to March 2016. Lihtcurve inversion method (Kaasalainen et al. (2001)), applied on 12 relative lightcurves obtained at various geometric conditions of the asteroid, reveals the spin vector, the sense of rotation and the preliminary shape model of the asteroid. Our aim is to contribute in increasing the set of asteroids with known spin and shape parameters. This could be done with dense lightcurves, obtained during small number of apparitions, in combination with sparse data produced by photometric asteroid surveys such as the Gaia satellite (Hanush (2011)).

Asteroid collisions as origin of debris disks: Asteroid shape reconstruction from BNAO Rozhen photometry

2019 ◽  
Vol 15 (S350) ◽  
pp. 451-453
Author(s):  
G. Apostolovska ◽  
E. Vchkova Bebekovska ◽  
A. Kostov ◽  
Z. Donchev
Keyword(s):  
Laboratory Experiments ◽  
Extrasolar Planets ◽  
Shape Reconstruction ◽  
Inversion Method ◽  
Debris Disks ◽  
Shape Parameters ◽  
Zodiacal Cloud ◽  
Photometric Observations ◽  
Different Shapes ◽  
Asteroid Surface

AbstractAs a result of collisions during their lifetimes, asteroids have a large variety of different shapes. It is believed that high velocity collisions or rotational spin-up of asteroids continuously replenish the Sun’s zodiacal cloud and debris disks around extrasolar planets (Jewitt (2010)). Knowledge of the spin and shape parameters of the asteroids is very important for understanding collision asteroid processes. Lately photometric observations of asteroids showed that variations in brightness are not accompanied by variations in colour index which indicate that the shape of the lightcurve is caused by varying illuminations of the asteroid surface rather than albedo variations over the surface. This conclusion became possible when photometric investigations were combined with laboratory experiments (Dunlap (1971)). In this article using the convex lightcurve inversion method we obtained the sense of rotation, pole solutions and preliminary shape of 901 Brunsia.

Modeling asteroid shapes using BNAO Rozhen photometric data in combination with sparse data

2021 ◽  
Author(s):  
Gordana Apostolovska ◽  
Elena Vchkova Bebekovska ◽  
Galin Borisov ◽  
Andon Kostov ◽  
Zahary Donchev
Keyword(s):  
Weather Conditions ◽  
Sparse Data ◽  
Space Mission ◽  
Physical Characteristics ◽  
Photometric Data ◽  
Inversion Method ◽  
Physical Parameters ◽  
Minor Planets ◽  
Photometric Observations ◽  
Dense Data

<p>Our work aims to demonstrate how the use of our dense lightcurves in combination with sparse data from diverse sources will affect the results for obtaining the sidereal period, shape models, and ecliptic pole solution for a chosen asteroid.</p> <p>Photometric observations of minor planets are traditional at the Bulgarian National Astronomical observatory (BNAO) Rozhen. They started with photoelectric observations in 1991, and later have been continued as CCD photometric observations on all three telescopes: 2m Ritchey-Chretién-Coudé, 50cm/70cm, and 60cm Cassegrain. We hope that the new 1.5 m robotic telescope planned to be operational next year will be also partly devoted to the study of minor planets.</p> <p>Our target, 339 Dorothea, is a main-belt asteroid, a large member of the Eos dynamical family. For the last 8 years, between 2013 and 2021, the asteroid 339 Dorothea was observed at BNAO Rozhen during six apparitions and several dense lightcurve were obtained. We used these dense photometric data in lightcurve inversion method and reconstruct the model of the asteroid, determining its sidereal period, shape, and pole orientation. Afterward, using sparse data from the AstDys database with an accuracy of 0.01 mag in combination with the obtained dense data, new trials for calculating and improving the physical characteristics of the asteroid 339 Dorothea were made.</p> <p>Unlike very low photometric accuracy in ground-based sparse photometry, space missions have provided astronomers with sparse photometry with extremely high accuracy, for example, the ESA GAIA mission. The NEOWISE mission has observations only for a limited number of asteroids. Fortunately, we were able to find some sparse data for our target and use this accurate photometry in combination with our dense lightcurves for the reconstruction of the asteroid spin state and shape model.</p> <p>Due to bad weather conditions and limited allocation of observing time at the BNAO Rozhen dedicated to our project, we have at our disposal full and partial dense lightcurves obtained for several more asteroids in few different apparitions. Combining these dense data with ground-based or space mission sparse data will contribute to enlarging the database of asteroids with known physical characteristics. Enriching the number of asteroids with known physical parameters would provide more data for future statistical analysis and could help in answering the questions for the evolution of our Solar System. </p>

scholarly journals The physical and dynamical characteristics of the asteroid 4940 Polenov

2021 ◽  
pp. 39-49
Author(s):  
E. Vchkova-Bebekovska ◽  
N. Todorovic ◽  
A. Kostov ◽  
Z. Donchev ◽  
G. Borisov ◽  
...  
Keyword(s):  
Outer Part ◽  
Astronomical Observatory ◽  
Inversion Method ◽  
Main Belt ◽  
Dynamical Characteristics ◽  
Photometric Observations ◽  
Synodic Period ◽  
Solar System Object ◽  
Stability Time ◽  
Astronomical Station

The asteroid (1986 QY4) 4940 Polenov is the first Solar system object whose 3D shape is determined using the observations from the newly built Astronomical Station Vidojevica (ASV). Here we present the results of photometric observations for Polenov, gathered from the ASV, and from the Bulgarian National Astronomical Observatory (BNAO) Rozhen, during 2014, 2019 and 2020 apparitions. Polenov is a 17.8km object located in the outer part of the main belt and belongs to the asteroid family Themis. We have determined the lightcurves, the synodic period of 4.161?0.001 h, as well as the solution for the shape and spin axis. Using the lightcurve inversion method, the combination of our lightcurves and the sparse data from ATLAS{HKO and ATLAS-MLO, we also found the sidereal period, indicating a retrograde rotation of the asteroid, with two possible mirrored pole solutions. The ratio of the largest to smallest reecting surface is about 1.4. In addition, we studied the dynamical properties of the asteroid and obtained a long stability time that exceeds 0.4 Gyrs.

scholarly journals Optical observations of NEA 3200 Phaethon (1983 TB) during the 2017 apparition

2018 ◽  
Vol 619 ◽  
pp. A123 ◽  
Author(s):  
M.-J. Kim ◽  
H.-J. Lee ◽  
S.-M. Lee ◽  
D.-H. Kim ◽  
F. Yoshida ◽  
...  
Keyword(s):  
Optical Observations ◽  
Inversion Method ◽  
Observation Data ◽  
Convex Model ◽  
Convex Shape ◽  
Axis Ratio ◽  
Shape Model ◽  
Spin Properties ◽  
Pole Orientation ◽  
Ecliptic Longitude

Context. The near-Earth asteroid 3200 Phaethon (1983 TB) is an attractive object not only from a scientific viewpoint but also because of JAXA’s DESTINY+ target. The rotational lightcurve and spin properties were investigated based on the data obtained in the ground-based observation campaign of Phaethon. Aims. We aim to refine the lightcurves and shape model of Phaethon using all available lightcurve datasets obtained via optical observation, as well as our time-series observation data from the 2017 apparition. Methods. Using eight 12-m telescopes and an optical imager, we acquired the optical lightcurves and derived the spin parameters of Phaethon. We applied the lightcurve inversion method and SAGE algorithm to deduce the convex and non-convex shape model and pole orientations. Results. We analysed the optical lightcurve of Phaethon and derived a synodic and a sidereal rotational periods of 3.6039 h, with an axis ratio of a∕b = 1.07. The ecliptic longitude (λp) and latitude (βp) of the pole orientation were determined as (308°, −52°) and (322°, −40°) via two independent methods. A non-convex model from the SAGE method, which exhibits a concavity feature, is also presented.

scholarly journals Spins, shapes, and orbits for near-Earth objects by Nordic NEON

2006 ◽  
Vol 2 (S236) ◽  
pp. 309-320
Author(s):  
Karri Muinonen ◽  
Johanna Torppa ◽  
Jenni Virtanen ◽  
Jyri Näränen ◽  
Jarkko Niemel ◽  
...  
Keyword(s):  
Variation Method ◽  
Inversion Method ◽  
Shape Error ◽  
The Novel ◽  
Optical Telescope ◽  
Shape Model ◽  
Novel Approach ◽  
Large Numbers ◽  
Near Earth Objects ◽  
Triaxial Shape

AbstractThe observing program of the Nordic Near-Earth-Object Network (NEON) accrues knowledge about the physical and dynamical properties of near-Earth objects (NEOs) using state-of-the-art inverse methods. Photometric and astrometric observations are being carried out at the Nordic Optical Telescope. Here, the NEON observations from June 2004–September 2006 are reviewed. Statistical orbital inversion is illustrated by the so-called Volume-of-Variation method. Statistical inversion for spins and shapes is carried using a simple triaxial shape model yielding analytical disk-integrated brightnesses for both Lommel-Seeliger and Lambert scattering laws. The novel approach allows spin-shape error analyses with the help of large numbers of sample solutions. Currently, such spin-shape solutions have been derived for 2002 FF12, 2003 MS2, 2003 RX7, and 2004 HW. For (1862) Apollo, an unambiguous spin-shape solution has been obtained using the conventional, convex inversion method and, for (1685) Toro and (1981) Midas, the conventional method has been applied repeatedly to map the regime of possible solutions.

A Taylor Expansion Approach for Computing Structural Performance Variation From Population-Based Shape Data

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Xilu Wang ◽  
Xiaoping Qian
Keyword(s):  
Taylor Expansion ◽  
Population Based ◽  
Shape Modeling ◽  
Structural Performance ◽  
Shape Parameters ◽  
Explicit Function ◽  
Performance Variation ◽  
Statistical Shape ◽  
Function Relationship ◽  
Shape Data

Rapid advancement of sensor technologies and computing power has led to wide availability of massive population-based shape data. In this paper, we present a Taylor expansion-based method for computing structural performance variation over its shape population. The proposed method consists of four steps: (1) learning the shape parameters and their probabilistic distributions through the statistical shape modeling (SSM), (2) deriving analytical sensitivity of structural performance over shape parameter, (3) approximating the explicit function relationship between the finite element (FE) solution and the shape parameters through Taylor expansion, and (4) computing the performance variation by the explicit function relationship. To overcome the potential inaccuracy of Taylor expansion for highly nonlinear problems, a multipoint Taylor expansion technique is proposed, where the parameter space is partitioned into different regions and multiple Taylor expansions are locally conducted. It works especially well when combined with the dimensional reduction of the principal component analysis (PCA) in the statistical shape modeling. Numerical studies illustrate the accuracy and efficiency of this method.

scholarly journals Observations of comets and minor planets at Kiev comets station (585)

2009 ◽  
Vol 5 (S263) ◽  
pp. 298-302
Author(s):  
Alexander R. Baransky ◽  
Klim I. Churuymov ◽  
Vasyl A. Ponomarenko
Keyword(s):  
Astronomical Observatory ◽  
Minor Planets ◽  
Photometric Observations ◽  
National University

AbstractWe present the results of astrometric and photometric observations of comets and minor planets obtained at the Kiev comet station (Code MPC 585) of the Astronomical Observatory of Kyiv Shevchenko National University in 2006-2009. The 2318 position observations of 176 comets, 302 observations of 57 numbered minor planets, and 220 observations of 30 unnumbered minor planets were obtained. The accuracy of the astrometric observations of the comets is analyzed.

scholarly journals Shape Modeling Based on Convolutional Restricted Boltzmann Machines

2018 ◽  
Vol 173 ◽  
pp. 01022
Author(s):  
Xi-Li Wang ◽  
Fen Chen
Keyword(s):  
Euclidean Distance ◽  
Shape Modeling ◽  
Test Time ◽  
Construction Process ◽  
Restricted Boltzmann Machines ◽  
Shape Model ◽  
Training Time ◽  
Boltzmann Machines ◽  
The Difference ◽  
And Training

This paper proposes a kind of shape model based on convolutional restricted Boltzmann machines(CRBM), which can be used to assist the task of image target detection and classification. The CRBM is a generative model that can model shapes through the generative capabilities of the model. This paper presents the visual representation, construction process and training method of the model construction. This paper does experiments on the Weizmann Horse dataset. The results show that, compared with RBM, although the training time of this model is slightly longer, the test time of the model is similar, and it can better shape modeling, modeling of the details of the shape can be well expressed. The samples generated from CRBM look more realistic. The difference between the shape and the original shape generated by Euclidean distance measurement shows that the model has a strong ability to model shapes.

Statistical Shape Modeling and Population Analysis of the Aortic Root of TAVI Patients

2013 ◽  
Vol 7 (4) ◽  
Author(s):  
Bart Bosmans ◽  
Toon Huysmans ◽  
Roel Wirix-Speetjens ◽  
Peter Verschueren ◽  
Jan Sijbers ◽  
...  
Keyword(s):  
Aortic Root ◽  
Population Analysis ◽  
Statistical Shape Model ◽  
Shape Modeling ◽  
Aortic Valves ◽  
Shape Model ◽  
Statistical Shape ◽  
Statistical Shape Modeling

The new transcatheter technique to implant synthetic aortic valves offers a treatment to patients previously considered untreatable. However, the majority of patients suffer from leakage alongside the implant. Using a statistical shape model of the anatomy, a correlation was discovered between leakage and the shape of the sinuses of Valsalva.

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