IGS Analysis Center Workshop - IGS - NASA

need to be developed. It would be natural for RAC’S and NAC’S to be, in official IGSterms, “Associate Analysis Centers.”(ii) GAC’S produce and distribute, in addition to orbit and EOP solutions, “daily” fiducialfreenetwork solutions, station and satellite clock solutions and tropospheric calibrations.(iii) IGS encourage research into network combination, especially by the NAC’S whichperform the routine work.(iv) IGS develop and decide upon formats for the additional products described in thisdocument.(v) The type of activities sketched in this document begin as soon as possible, since theglobal network is very rapidly becoming unmanageable.(vi) RAC’S and NAC’S send summary reports via IGSREPORTS e-mail, and send theirproducts to the data centers.(vii) IGS Central Bureau prepare itself for assessing contributions from GAC’S, RAC’Sand NAC’S, providing routine feedback, and providing general oversight to see that thenew system evolves in a rational way. IGS Central Bureau (in consultation with IERS) isalso responsible for overseeing the production of the standard frame.(viii) IGS Central Bureau prepare itself for serving regional users (e.g., providing clearinstructions, recommendations, help, etc.).Y(ix) Data centers prepare themselves for the additional burden of making available the newproducts described in this document.ACKNOWLEDGMENTS. We thank Bob King for reviewing this paper and forproviding useful comments, and Jie Zhang, Eric Calais, S.S,0. Puntodewo, Jeff Genrichand Jim Zumberge for contributing research material and figures. The research describedin this paper was carried out in part by the Jet Propulsion Laboratory, California Institute ofTechnology under a contract with the National Aeronautics and Space Administration.Research at S10 is supported by the National Aeronautics and Space Administration(NAGS- 1917), the National Science Foundation (EAR 92 08447), the Southern CaliforniaEarthquake Center USGS cooperative agreement (14-08 -00001 -A0899) and the U.S.Geological Survey (1434-92-G2196).REFERENCESArgus, D.F. and R.G. Gordon, No-Net-Rotation model of current plate velocitiesincorporating plate rotation model NUVEL- 1, Geophys. Res. fitt., 18, 2039-2042,1991 0Beutler, G. and E. Brockman, eds., Proceedings of the 1993 IGS Workshop, Inte~ationalAssociation of Geodesy, Druckerei der Universitat Bern, 1993.Bierman, G.J., Factorization methods for discrete sequential estimation, Academic Press,San Diego, Ca.lif., 1977.Blewitt, G., Carrier phase ambiguity resolution for the Global Positioning System appliedto geodetic baselines up to 2000 km, J. Geophys. Res., 94, 10,187-10,283, 1989.Blewitt, G., M.B. Heflin, K,J. Hurst, D.C. Jefferson, F.H. Webb and J.F. Zumberge,Absolute far-field displacements from the June 28, 1992, Landers earthquakesequence, Nature, 361, 340-342, 1993.89