  More than 635 000 positional observations (mostly radiotechnical) of planets
and spacecraft (1961-2010), have been used for estimating possible changes of
the gravitation constant, the solar mass, and semi-major axes of planets, as
well as the value of the astronomical unit, related to them. The analysis of
the observations has been performed on the basis of the EPM2010 ephemerides of
IAA RAS in post-newtonian approximation. The obtained results indicate on
decrease in the heliocentric gravitation constant per year at the level $ \dot
{GM_{Sun}}/GM_{Sun} = (-5.0 \pm 4.1) 10^{-14} (3\sigma).$ The positive secular
changes of semi-major axes $ \dot a_i/a_i$ have been obtained simultaneously
for the planets Mercury, Venus, Mars, Jupiter, Saturn, as expected if the
geliocentric gravitation constant is decreasing in century wise. The change of
the mass of the Sun $M_{Sun}$ due to the solar radiation and the solar wind and
the matter dropping on the Sun (comets, meteors, asteroids and dust) was
estimated. Taking into account the maximal limits of the possible $M_{Sun}$
change, the value $\dot G/G$ falls within the interval $ -4.2\cdot10^{-14} <
\dot G/G < +7.5\cdot10^{-14}$ in year with the 95% probability. The
astronomical unit (au) is only connected with the geliocentric gravitation
constant by its definition. In the future, the connection between $GM_{Sun}$
and au should be fixed at the certain time moment, as it is inconvenient highly
to have the changing value of the astronomical unit.

Solar and Stellar Astrophysics;Earth and Planetary Astrophysics