TIME AND GEOLOCATION UNCERTAINTIES AS COMPONENTS OF THE ACCURACY OF NEAS’ GROUND-BASED OBSERVATIONS

Abstract

The one of main tasks for solving the as teroid-cometary hazard problem is cataloging all objects that might come extremely close to Earth and pose a poten tial threat of collision. The reliability of their orbits significantly depends on the quality and the statistical treatment of astrometric observations, which are obtained by different observers and different techniques. Statistical analysis of the IAU MPC observational array of the small Solar system bodies and the development of a scheme for assigning weights to individual observation sets are im portant for performing asteroid orbit determination and refinement. Errors in the positions of asteroids associated with errors in the reference catalogs, observation epoch, observed brightness and rate of motion are considered in sufficient detail in investigations of Chesley et al. (2010), Farnocchia (2015), Vereš et al. (2017). Timing and geolo cation uncertainties of the observer are less discussed in the literature. But in the case of observations of NEAs, espe cially at the moments of the close approaches to the Earth, timing errors and errors in the observatory's geolocation can significantly affect the accuracy of the obtained positions. Residual differences (O - C) in the equatorial coordinate system are usually used to search and identify functional errors dependencies. To detect errors caused by timing uncertainties, instead of residual differences (О - С) in equatorial coordinates, it is more convenient to use their along-track and cross-track representation. The cross-track differences are independent of timing errors and indicate only astrometric errors. On the other hand, timing errors are fully contained in the along-track component. Here we present the simulation results of such errors and analysis using an array of observations from three observatories for the period 2017 - 2022. The array con tains more than 18,000 positions of about 900 objects. Most of the objects belong to the group of NEAs, which include PHAs during close approaches to the Earth.