The Ability of the GPS to Monitor Earth Rotation Variation

Based on optical observations earth rotation variations have been monitored since the beginning of the century. Their part has been taken over within the past 25 years by space geodetic techniques like SLR, LLR and VLBI, which took a center stage in the determination of oscillations in the earth orientation parameters on different time scales. Moreover, in the early nineties the microwave techniques, in particular the GPS, turned out to be an excellent sensor for earth rotation variations, comparable to VLBI both in accuracy and resolution. The given article deals with principles related to the processing of GPS data, touches on the problems of satellite orbit determination and focuses on the estimation of subdaily polar motion and UT1. Finally, contributions of the GPS to the determination of an improved nutation model are presented.