The motion of major planets from observations 1769–1988 and some astronomical constantsAbout the paper Full text
Modern planetary theories may be considered as a realisation of a four-dimensional dynamical reference frame. The existence of secular trends between the dynamical system and the adopted system of the Fundamental Catalogue (as well as between time scales involved) has been studied by discussing planetary observations of different types and by comparison with a numerical theory constructed for the time span 1769–1988. Parameters of the theory were fitted to radar ranging data for 1961–1988 for inner planets and to meridian observations of 18th–20th centuries for outer planets. Then a set of the inner planet optical observations, which includes USNO meridian observations, transits through the solar disk and occultations of fundamental stars are discussed. The main results are the following: 1. Radar data were used to estimate the time derivativeĠ of the gravitational constant G (in another interpretation, the secular trend between the atomic and dynamic time scales): Gdot/G=(0.37±0.45)×10^−11/y. This estimation, being statistically insignificant, gives some physically meaningful restriction to Gdot. 2. From the same data a new estimation of relativistic effects in the motion of Mercury was obtained, which has confirmed the Einstein value of the perihelion advance with the error 0″.06/cy. So in the frame of Einstein's theory the value of solar dynamic oblateness cannot be larger than 2×10−6. 3.The analysis of time behavior of residuals in the inner planet longitudes shows secular trends. It is demonstrated that these trends may be explained by combined action of a linear trenddT of Brouwer's time scale (which is adopted as a standard for reduction of observations before 1959) and the error in Newcomb's value of the constant of precession. From USNO meridian observations fordT the following estimate was obtained: dT=−14.5±2.1 sec/cy with the corresponding correction,dp, to Newcomb's precession dp=0″.46±0″.13/cy. The estimate of dT is in good agreement with the value of dT determined from transits of Mercury and Venus through the solar disk dT=−12.9±1.3 sec/cy which does not depend on any precession error. 4. As a by-product, new accurate ephemerides of the outer planets are obtained over the time interval 1769–1988, the average residuals being presented.