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Values of some astronomical parameters (au, GMS,MS), their possible variations from modern observations, and interrelations between them

E. V. Pitjeva

Proceedings of the Journées 2011 "Systèmes de Référence Spatio-Temporels", H. Schuh, S. Böhm, T. Nilsson and N. Capitaine (eds), Vienna University of Technology, 17-20 (2012)

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Recent years of high-precision data of spacecraft have given the possibility to estimate the values of the astronomical unit and the heliocentric gravitational constant with great precision. Both estimations have been obtained from more than 635 000 positional observations (1913–2010) of planets and spacecraft. The analysis of the observations was performed on the basis of the numerical Ephemerides of Planets and the Moon (EPM2010) of IAA RAS. The estimation of the change of the GM⊙ heliocentric gravitation constant has also been obtained: GMdot⊙/GM⊙ = (−5.0 ± 4.1) · 10−14 per year. The obtained decrease of GM⊙ should correspond to the secular decrease of au. However, it has been shown that the present accuracy level of observations does not permit to evaluate the au change. The possibility of finding the GM⊙ change from high-accuracy observations points that fixing the value of au is desirable, as it is highly inconvenient to have the value of the astronomical unit variable.