Papers by Alexandre Andrei
EPJ Web of Conferences, 2013
ABSTRACT
Observatory Operations: Strategies, Processes, and Systems V, 2014
ABSTRACT Gaia, the 1 billion star, high precision, astrometric satellite will revolutionise our u... more ABSTRACT Gaia, the 1 billion star, high precision, astrometric satellite will revolutionise our understanding in many areas of astronomy ranging from bodies in our Solar System to the formation and structure of our Galaxy. To fully achieve the ambitious goals of the mission, and to completely eliminate effects such as aberration, we must know the position and velocity vectors of the spacecraft as it orbits the Lagrange point to an accuracy greater than can be obtained by traditional radar techniques, leading to the decision to conduct astrometric observations of the Gaia satellite itself from the ground. Therefore the Ground Based Optical Tracking (GBOT) project was formed and a small worldwide network using 1-2 m telescopes established in order to obtain one measurement per day of a precision/accuracy of 20 mas. We will discuss all aspects of GBOT, setup, feasibility considerations, preliminary tests of observing methods, partner observatories, the pipeline/database (see also contribution by Bouquillon et al.1).
Proceedings of the International Astronomical Union, 2013
The Gaia catalogue will contain 500 000 QSOs with very accurate optical coordinates, at level of ... more The Gaia catalogue will contain 500 000 QSOs with very accurate optical coordinates, at level of some tens to some hundreds of micro - arcsecond. From these targets a core sample will be chosen, formed by those with the most precise positions, to define the Gaia Fundamental Reference Frame. It will be at the basis of an optical reference frame ( provisionally, the GCRF) more accurate than the current version of the (radio) ICRF. At the same time due care must be taken when choosing the core picks because quasars do are also known by their flux variability, on time scales that may span from hours u p to years. We will review some of the potential astrophysical processes that could induce these variations in the corresponding emission regions and we will present light curves that were obtained by small robotic telescopes during more than 1.5 years. We will also present high resolution images obtained at ground based optical telescopes together with the morphological analysis of the ta...
A Division 1 Working Group on "Nomenclature for Fundamental Astronomy" (NFA) was formed... more A Division 1 Working Group on "Nomenclature for Fundamental Astronomy" (NFA) was formed at the 25th IAU GA in 2003 in order to provide proposals for new nomencla- ture associated with the implementation of the IAU 2000 Resolutions. This WG is also intended to make related educational efforts for addressing the issue to the large community of scien- tists. Five
Proceedings of the International Astronomical Union, 2007
Proceedings of the International Astronomical Union, 2005
Proceedings of the International Astronomical Union, 2011
Proceedings of the International Astronomical Union, 2010
The business meeting was opened by the President, Irina Kumkova. She presented the agenda, which ... more The business meeting was opened by the President, Irina Kumkova. She presented the agenda, which was approved. This session was attended by 42 participants. The meeting approved Dafydd Evans as secretary of minutes.
Proceedings of the International Astronomical Union, 2009
Abstract. The Observatório Nacional at Rio de Janeiro has developed a new heliometer to per-form ... more Abstract. The Observatório Nacional at Rio de Janeiro has developed a new heliometer to per-form accurate measurements of the solar diameter. The equipment makes use of split parabolic mirrors, rather than split achromatic lenses as objective. In its first campaign this reflector ...
A Division 1 Working Group on "Nomenclature for Fundamental Astronomy" (NFA) was formed... more A Division 1 Working Group on "Nomenclature for Fundamental Astronomy" (NFA) was formed at the 25th IAU GA in 2003 in order to provide proposals for new nomenclature associated with the implementation of the IAU 2000 Resolutions. This WG is also intended to make related educational efforts for addressing the issue to the large community of scientists. Five Newsletters were issued from October 2003 to July 2004 and posted on the NFA webpage (http://syrte.obspm.fr/iauWGnfa/). One important step has been the preparation of a questionnaire including a part on 'terminology choices' and a part for the Almanac Offices and related organizations. The summary of the responses and comments to this questionnaire and further questions have led to draft WG recommendations and guidelines on terminology together with a Resolution proposal to the IAU 2006 GA which are supported by explanatory documents. This paper reports on the WG activities, draft recommendations and future actions.
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Papers by Alexandre Andrei