Improvement of accuracy of planetary ephemerides by the example of EPM
Abstract
Fundamental ephemeris of planets and the Moon (EPM) have been created at IAA RAS since the 70-th of the last century. Some of their major versions EPM2004, EPM2008, EPM2011/m are available at ftp://quasar.ipa.nw.ru/incoming/EPM/. EPM2014 version has been created with the updated and refined software package ERA-8. The accuracy of the planetary ephemerides depends on several factors: the adequacy of dynamic model of planet motion to their real motion, the quantity and quality of observational data, as well as the reduction of the observations. Reductions of the observations are well known, however more precise data need more accurate calculation. For example, processing the Cassini spacecraft data required to improve the calculation of proper time.Dynamic models of planetary motion from EPM2004 to EPM2014 have been refined and complicated: perturbations from small asteroids modeled at first by perturbation of a one-dimensional, and then the two-dimensional rings, as well as the inclusion of the 30 largest Trans-Neptunian Objects (TNO) into integration and the perturbations from other TNO modeled by a ring of smaller TNO.The number of observations has increased by an order since EPM2000 and amounts for more than 800,000 data of different types, most of the new observations are precision radio measurements, mainly ranging from different spacecraft. VLBI spacecraft data around planets in the background quasars enable orientation of the planetary ephemeris in the international system ICRF with an accuracy of fractions of mas.Improvement of all these factors helped to increase the accuracy of planetary ephemerides, which was manifested in a decrease of the formal standard deviations of orbital elements of planets by several times, and for planets provided by high-precision data from spacecraft (Venus, Mars, Saturn) - by one order.
- Publication:
-
IAU General Assembly
- Pub Date:
- August 2015
- Bibcode:
- 2015IAUGA..2256614V