Determination of the reference frames deflections from optical observations of GNSS satellites

Optical observations of navigation satellites were carried out at Terskol observatory during 2007-2010 with the aim to determine the deffection angles between GPS and GLONASS dynamical reference frames. There were three different observations strategies: celestial equator crossing, intersection of visible satellite paths, occultation of astrometric stars with the satellite. We present methodology of observation, data processing and the first results

Analysis of the Accuracy of Prediction of the Celestial Pole Motion

VLBI observations carried out by global networks provide the most accurate values of the precession-nutation angles determining the position of the celestial pole; as a rule, these results become available two to four weeks after the observations. Therefore, numerous applications, such as satellite navigation systems, operational determination of Universal Time, and space navigation, use predictions of the coordinates of the celestial pole. In connection with this, the accuracy of predictions of the precession- nutation angles based on observational data obtained over the last three years is analyzed for the first time, using three empiric nutation models---namely, those developed at the US Naval Observatory, the Paris Observatory, and the Pulkovo Observatory. This analysis shows that the last model has the best of accuracy in predicting the coordinates of the celestial pole. The rms error for a one-month prediction proposed by this model is below 100 microarcsecond.Comment: 13 p