IGS Analysis Center Workshop - IGS - NASA

SUMMARY OF SESSION 5In the last session, three additional presentations were given.In the first presentation, Dr. Martine Feissel highlighted the IERS studies of the IGS pole solutionswith particular emphases on the long term stability. It was noted that some GPS polar motion seriesexhibited drifts of several mas/year demonstrating the importance of VLBI. Also summarized werenew developments and improvements in precession and nutation models supported by VLBIobservations.In the second presentation given by Dr. Feissel on behalf of Boucher and Altamimi, the latest ITRFsolutions and coordinate sets were reviewed. The significance of the IERS/ITRF effort, whichprovides a common reference frame and connection to other space technique such as VLBI/SLRhas been greatly appreciated and acknowledged by all participants. The plans to make the ITRFand EOP mutually consistent at the sub-mas level for the 1993 Annual Report were alsohighlighted. This will mean a small re-alignment of the ITRF reference frame to maintain thecontinuity of EOP.In the last presentation, an interesting application of GPS with emphasis on the post-glacial upliftin Fennoscandia was presented. GPS data from the IGS core network, supplemented by anextensive regional network are being processed using a state of the art software (GIPSY II). Thisyielded a repeatability of a few ppb in distance for baselines of a few thousand km. Practically thesame results were obtained with the best IGS orbits held fixed or with orbits determined from bothregional and global (IGS) networks. Dr. Johansson expressed interest in using the future combinedIGS orbits and also to become an IGS Associated Analysis Center...98