1 GBOT’s asteroid survey

The GBOT group is in charge of the Ground Based Optical Tracking of the Gaia satellite. In concrete terms, since the launch of Gaia, our task is to take every night, using ground based medium-class telescopes, short sequences of ~10 images of the Gaia satellite close to its meridian transit. After an astrometric reduction of these images, the position of Gaia is measured in ICRF with an accuracy of 20 mas and provided to ESOC. For these activities, we mainly use VLT survey telescope (VST, 2.6m paranal, Chile) with the Omegacam camera which covers a field of view of one square degrees.

In these images, taken close to the sun opposition – since Gaia is in L2 – we also observe a lot of asteroids: between 30 and 100 asteroids every night up to the magnitude of 22 (more details available on the following web-page: http://gbot.obspm.fr/idex.php?page=presentation). For extracting all the information relevant to these objects and submitting it to the Minor Planet Center (MPC) on a daily basis, we have developed some methods, strategies and tools tailored explicitely for this task. In the three years of operation, this system has allowed us tosend to MPC the position and the photometry of more than 20,000 asteroids.

The purposes of this presentation is to expound all the aspects of the GBOT’s asteroid survey to share our experience with ADELA members involved in similar projects.

Dr. Sebastien Bouquillon
2 Synergy between Radio (VLBI) and Optical (Gaia) astrometric researches Synergy between Radio (VLBI) and Optical (Gaia) astrometric researches Dr. Nobuyuki Sakai
3 Dr. Altmann Martin Heidelberg/GAIAAlemania Gaia DR2, released on April 25, 2018 is the first full Gaia release with 1.3 billion stars having measured 5-parameter astrometry and 3-band photometry.
Therefore the impact of this dataset is revolutionary, following the already highly successful but limited first data release from 2016. In my presentation, I will give an overview of the data within Gaia DR2, its strengths and also some limitations of this data and astrometric data overall. Finally I will present some show cases using DR2 data  and look ahead to the next Gaia releases.
Dr. Altmann Martin Heidelberg/GAIAAlemania
4 Switching from URAT to DST, from bright stars to QSOs The USNO Robotic Astrometric Telescope (URAT) observing program concluded in June 2018.  Reductions to improve astrometry of very bright stars are in progress which will supplement the Gaia mission.  A new 1-meter Deep South Telescope (DST) will be delivered to the U.S. Naval Observatory later this year and put into the URAT dome at Cerro Tololo to support high cadence observations of extragalactic sources used to tie the ICRF to the Gaia reference frame. Dr. Norbert Zacharias
5 Escombros espaciales:  prevención de colisiones, métodos analíticos y 
población artificial
Desde el lanzamiento de Sputnik-1 hasta el presente, se han generado grandes cantidades de escombros espaciales; estos se ubican en órbitas cambiantes e incontroladas, lo que aumenta la probabilidad de colisión entre ellos o con otros orbitadores. Todo ello hace que sea esencial el estudio de la dinámica de dichos escombros espaciales. En esta charla se discuten diferentes herramientas, que se centran en el tratamiento de la dinámica de estos escombros espaciales. Primero, se presenta un método simple para determinar pares de objetos de un catálogo que están en
riesgo real de colisión. En segundo lugar, se explica brevemente una herramienta analítica para propagar los escombros espaciales en la región geoestacionaria. Finalmente, se introduce un procedimiento para generar una población sintética de escombros espaciales a partir de datos conocidos y mediante el uso de medios estadísticos.
Dr. Daniel Casanova Ortega
6 Challenges Related to Discovery, Follow-Up, and Characterization of Space Debris The proliferation of space debris and the increased probability of collisions and interference raise concerns about the long-term sustainability of space activities, particularly in the low-Earth orbit and geostationary orbit environments. During recent years governments, space agencies and civilian research organizations increased their efforts to build space object catalogues and to investigate the space debris population in different orbit regions. Understanding the nature and the sources of debris is a prerequisite to provide the scientific foundation for a sustainable use of near-Earth space.
This presentation will describe current space debris research activities to detect and characterize space debris at the Swiss Optical Ground Station and Geodynamics Observatory Zimmerwald. In particular, optical techniques to detect track and characterize space objects including small-size debris will be presented and illustrated with examples from
the long-standing observation programs of the Astronomical Institute of the University of Bern (AIUB).
Dr. Thomas Schildknecht University of Bern, Suiza
7 «Methods of using orbits obtained from the optical measurements 
processing for analyzing the orbital motion of objects in high 
geocentric orbits and fragmentations of orbital space objects»
Optical astrometric measurements represent the most important type of measurements widely used to reconstruct orbital motion of space debris objects in high geocentric orbits. Along with orbital parameters some other characteristics of space debris objects can be estimated using optical astrometric measurements. Accurate orbital information is important to properly assess possible close conjunctions between spacecraft and space debris objects. This information is also required to estimate long-term evolution of space debris population as well as
characterize on-orbit fragmentations. This presentation will provide description of basic techniques used for analysis of orbital motion of space debris objects and on-orbit fragmentations illustrated with examples from Astronomical Scientific Center activities.
Dr. Vladimir Agapov
Centro Científico de Astronomía Moscú, Rusia



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