On the possibility of detecting some terms of the diurnal polar motion by the study of satellite orbits

Abstract

The high precision of satellite laser ranging data obtained by the laser stations and the improvement of the models of forces acting on the satellite permit us to estimate the pole position with a few milliarsecond precision. In addition to the well-known precession and nutation in a space-fixed system the earth's rotation axis is affected by a diurnal motion which is superimposed to the polar motion in the terrestrial system. However, the way the pole position is usually estimated by determining a constant value and assuming a linear drift over a few days, the diurnal polar motion is averaged to zero. After some study of the geometry of the system and the relation between the diurnal polar motion and the satellite orbit, we have performed a series of simulations to see if this variation can be separated from variations in the orbit. The main result is that a specific quasi-diurnal term (corresponding to the fortnightly term in space) can be estimated with a milliarcsecond accuracy. Due to the effect of the tides at the same frequency, no significant value has been determined using real data.