The astrometric Gaia-FUN-SSO observation campaign of 99942 Apophis^⋆

¹ Institut de Mécanique Céleste et de Calcul des Éphémérides, Paris Observatory, UPMC, Lille 1 university, UMR 8028 du CNRS, PSL Research University, 77 avenue Denfert Rochereau, 75014 Paris, France
² Institute for Astrophysics (IfA), University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
³ Observatório do Valongo/UFRJ, Ladeira Pedro Antonio 43, CEP 20.080-090 Rio de Janeiro, RJ, Brazil
⁴ Observatório Nacional, Rua José Cristino 77, São Cristovão, CEP 20. 921-400 Rio de Janeiro, Brazil
⁵ Department of Astronomy and Geodesy, Kazan Federal University, Kremlevskaya Str., 18, 420008 Kazan, Russia
⁶ Academy of Sciences of Tatarstan, Bauman Str., 20, 420111 Kazan, Republic of Tatarstan, Russia
⁷ TÜBİTAK National Observatory, Akdeniz University Campus, 07058 Antalya, Turkey
⁸ Department of Computer Science, Jinan University, 510632 Guangzhou, PR China
⁹ Nikolaev Astronomical Observatory, 1 Observatorna, 54030 Mykolaiv, Ukraine
¹⁰ Université de Nice Sophia Antipolis, Observatoire de la Côte d’Azur, CNRS UMR 7293, Laboratoire Lagrange, Bd de l’Observatoire, BP 4229 06304 Nice Cedex 04, France
¹¹ Institute of Astronomy and NAO, Bulgarian Academy of Sciences, 72, Tsarigradsko Chaussee Blvd., 1784 Sofia, Bulgaria
¹² Institute of Astronomy of Kharkiv National University, Sumska Street 35, 61022 Kharkiv, Ukraine
¹³ Japan Spaceguard Association, 1-60-7 2F, Sasazuka, Shibuya-ku, Tokyo 151-0073, Japan
¹⁴ Bisei Spaceguard Center, Japan Spaceguard Association, 1716-3 Okura,bisei, Ibara,714-1411 Okayama, Japan
¹⁵ Astronomical Observatory of Kyiv University, Observatorna street 3, 04053 Kyiv, Ukraine
¹⁶ Isaac Newton Group of Telescopes, Apto. 321, 38700 Santa Cruz de la Palma, Canary Islands, Spain
¹⁷ Astronomical Observatory of the Autonomous Region of the Aosta Valley, Lignan 39, 11020 Nus (Aosta), Italy
¹⁸ Center of the Special Information Receiving and Processing and the Navigating Field Control, State Space Agency of Ukraine, Zalistsy, Dunayivtsy district, 32444 Khmelnytskyy region, Ukraine
¹⁹ ICAMER Observatory, National Academy of Sciences of Ukraine, 27 Acad. Zabolotnoho Str., 03680 Kiev, Ukraine
²⁰ Technical University Dresden, Institute of Planetary Geodesy, Lohrmann Observatory, 01062 Dresden, Germany
²¹ Pulkovo Observatory, Pulkovskoe Ch. 65, 196140 St.-Petersburg, Russia
²² Department of Imaging and Applied Physics, Bldg 301, Curtin University, Kent St, Bentley, WA 6102, Australia
²³ Yunnan Observatories, Chinese Academy of Sciences (CAS), PO Box 110, 650011 Kunming, PR China
²⁴ Observatoire Astronomique de l’Université de Genève, 51 chemin des Maillettes, 1290 Sauverny, Switzerland
²⁵ Kharadze Abastumani Astrophysical Observatory, Ilia State University, G. Tsereteli str. 3, 0162 Tbilisi, Georgia
²⁶ Ulugh Beg Astronomical Institute, Astronomicheskaya Street 33, 100052 Tashkent, Uzbekistan
²⁷ Keldysh Institute of Applied Mathematics, RAS, Miusskaya sq. 4, 125047 Moscow, Russia
²⁸ Faculty of Aerospace Engineering, Technion–Israel Institute of Technology, Technion City, 3200003 Haifa, Israel
²⁹ Universidad de La Laguna (ULL), 38205 La Laguna, Tenerife, Spain
³⁰ Department of Physics, Science Faculty, Akdeniz University, 07058 Antalya, Turkey

Received: 31 December 2014
Accepted: 24 July 2015

Abstract

Aims. Astrometric observations performed by the Gaia Follow-Up Network for Solar System Objects (Gaia-FUN-SSO) play a key role in ensuring that moving objects first detected by ESA’s Gaia mission remain recoverable after their discovery. An observation campaign on the potentially hazardous asteroid (99 942) Apophis was conducted during the asteroid’s latest period of visibility, from 12/21/2012 to 5/2/2013, to test the coordination and evaluate the overall performance of the Gaia-FUN-SSO .

Methods. The 2732 high quality astrometric observations acquired during the Gaia-FUN-SSO campaign were reduced with the Platform for Reduction of Astronomical Images Automatically (PRAIA), using the USNO CCD Astrograph Catalogue 4 (UCAC4) as a reference. The astrometric reduction process and the precision of the newly obtained measurements are discussed. We compare the residuals of astrometric observations that we obtained using this reduction process to data sets that were individually reduced by observers and accepted by the Minor Planet Center.

Results. We obtained 2103 previously unpublished astrometric positions and provide these to the scientific community. Using these data we show that our reduction of this astrometric campaign with a reliable stellar catalog substantially improves the quality of the astrometric results. We present evidence that the new data will help to reduce the orbit uncertainty of Apophis during its close approach in 2029. We show that uncertainties due to geolocations of observing stations, as well as rounding of astrometric data can introduce an unnecessary degradation in the quality of the resulting astrometric positions. Finally, we discuss the impact of our campaign reduction on the recovery process of newly discovered asteroids.