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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 We obtained 2103 previously unpublished astrometric positions and provide these to the scientific community.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.
Ключові слова: ПЗЗ-спостереження, астероїднокометна небезпека, АЗЗ (астероїди, що зближуються з Землею), ПОА (потенційно-небезпечні астероїди) ефемериди руху малих тіл Сонячної системи.
The paper describes observations of fast-moving near-Earth asteroids (NEAs) made with the small ground-based telescopes of National Time Service Center of Chinese Academy of Science (NTSC of CAS) and Research Institute “Mykolaiv Astronomical Observatory” (RI MAO) by the rotating-drift-scan CCD (RDS CCD) technique. This technique is used to obtain the point images of both the studied objects and reference stars. The results of ongoing follow-up observations of NEAs are discussed. The residual differences (O – C) between the observed and calculated positions from JPL ephemeris were generally small for these asteroids. The standard deviations of these differences were typically ±(0.2″ – 0.3″) in both coordinates for objects with apparent velocity which substantially exceed FWHM for the given exposure time. The results of comparative statistics for such observations from the MPC database show that this is a good level of precision for NEAs. Moreover, the telescopes with the RDS CCD technique implemented can observe the NEAs that closely approach the Earth and with enough observations can improve the precision of determining their orbital elements and impact predictions.
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