Improved Grace Science Results After Adjustment Of Geometric Biases In The Level-1b K-Band Ranging Data

ISI Document Delivery No.: 711QU Times Cited: 10 Cited Reference Count: 44 Cited References: Alley RB, 2007, ANN GLACIOL-SER, V46, P1, DOI 10.3189/172756407782871738 Arbinger C., 2003, 3 INT WORKSH SAT CON Bandikova T, 2010, GEOPH RES ABSTR, V12, pEGU2010 Bettadpur S, 2010, GEOPH RES ABSTR, V1, pEGU2010 Bettadpur S, 2007, 327720 GRACE U TEX C Bevis M, 2009, GEOCHEM GEOPHY GEOSY, V10, DOI 10.1029/2009GC002642 Boning C, 2008, GEOPHYS RES LETT, V35, DOI 10.1029/2008GL034974 Bruinsma S, 2010, ADV SPACE RES, V45, P587, DOI 10.1016/j.asr.2009.10.012 Case K, 2004, D22027 JPL CALTECH Chen JL, 2009, NAT GEOSCI, V2, P859, DOI 10.1038/ngeo694 CSR, 2009, REL NOT GRACE L 2 PR Davis E, 1999, IAF99B205 AM I AER A Flechtner F, 2005, GRACE SCI DATA SYSTE Flury J, 2008, ADV SPACE RES, V42, P1414, DOI 10.1016/j.asr.2008.05.004 Flury J, 2009, P GRACE SCI TEAM M N Frommknecht B, 2008, INTEGRATED SENSOR AN Han SC, 2008, J GEOPHYS RES-SOL EA, V113, DOI 10.1029/2007JB005218 Herman J., 2004, ESA Horwath M, 2009, P GRACE SCI TEAM M N Horwath M, 2009, GEOPHYS J INT, V177, P849, DOI 10.1111/j.1365-246X.2009.04139.x Horwath M, 2006, GEOPHYS RES LETT, V33, DOI 10.1029/2005GL025550 JPL, 2009, REL NOT GRACE L 2 CA Kanzow T, 2005, J GEOPHYS RES-OCEANS, V110, DOI 10.1029/2004JC002772 Kim JR, 2002, IAG SYMP, V123, P103 Kruizinga G, 2009, P GRACE SCI TEAM M D Lemoine JM, 2007, ADV SPACE RES, V39, P1620, DOI 10.1016/j.asr.2007.03.062 Macrander A, 2010, SYSTEM EARTH VIA GEO, DOI [10.1007/978-3-642-10228-8_34, DOI 10.1007/978-3-642-10228-8_34] Mayer-Gurr T, 2009, P GRACE SCI TEAM M D Morison J, 2007, GEOPHYS RES LETT, V34, DOI 10.1029/2006GL029016 Park JH, 2008, GEOPHYS RES LETT, V35, DOI 10.1029/2008GL034778 Priestley M.B., 1981, SPECTRAL ANAL TIME S Ramillien G, 2008, GLOBAL PLANET CHANGE, V60, P381, DOI 10.1016/j.gloplacha.2007.04.002 Ramillien G, 2006, GLOBAL PLANET CHANGE, V53, P198, DOI 10.1016/j.gloplacha.2006.06.003 Schmidt R, 2008, SURV GEOPHYS, V29, P319, DOI 10.1007/s10712-008-9033-3 Schrama EJO, 2007, J GEOPHYS RES-SOL EA, V112, DOI 10.1029/2006JB004882 Seeber G., 2003, SATELLITE GEODESY 2 Seo KW, 2008, GEOPHYS J INT, V172, P41, DOI 10.1111/j.1365-246X.2007.03611.x Tapley BD, 2004, GEOPHYS RES LETT, V31, DOI 10.1029/2004GL019920 Velicogna I, 2006, SCIENCE, V311, P1754, DOI 10.1126/science.1123785 Velicogna I, 2009, GEOPHYS RES LETT, V36, DOI 10.1029/2009GL040222 Wahr J, 2004, GEOPHYS RES LETT, V31, DOI 10.1029/2004GL019779 Wahr J, 2006, GEOPHYS RES LETT, V33, DOI 10.1029/2005GL025305 Wiehl M, 2005, EARTH OBSERVATION WITH CHAMP: RESULTS FROM THREE YEARS ORBIT, P121, DOI 10.1007/3-540-26800-6_19 WU SG, 2006, JPL PUBL Horwath, Martin Lemoine, Jean-Michel Biancale, Richard Bourgogne, Stephane Horwath, Martin/F-9239-2011 Horwath, Martin/0000-0001-5797-244X Deutsche Forschungsgemeinschaft (DFG) [Ho 4232/1-1] M. Horwath was supported by a research fellowship of the Deutsche Forschungsgemeinschaft (DFG), grant number Ho 4232/1-1. The authors thank the ISDC (Information System and Data Center) for the GRACE data distribution. P. Gegout (DTP, Toulouse) provided the grids used in the atmospheric background mass model. H. Bock (University of Bern) provided the GPS clock corrections. A. Macrander provided data from the AWI database on in situ OBP data. We thank him and the contributors to the data base, namely Agnieszka Beszczynska-Moller (AWI, Framstrait), Olaf Boebel (AWI, ACC), Johannes Karstensen (IFM-GEOMAR, MOVE), Uwe Send (SIO, MOVE), James Morison (North Pole, APL), and Randy Watts (URI, KESS). We thank the editor P. Ditmar and three anonymous reviewers for their insightful comments that lead to important improvements of the manuscript. 12 SPRINGER NEW YORK J GEODESYThe GRACE (Gravity Recovery and Climate Experiment) satellite mission relies on the inter-satellite K-band microwave ranging (KBR) observations. We investigate systematic errors that are present in the Level-1B KBR data, namely in the geometric correction. This correction converts the original ranging observation (between the two KBR antennas phase centers) into an observation between the two satellites' centers of mass. It is computed from data on the precise alignment between both satellites, that is, between the lines joining the center of mass and the antenna phase center of either satellite. The Level-1B data used to determine this alignment exhibit constant biases as large as 1-2 mrad in terms of pitch and yaw alignment angles. These biases induce non-constant errors in the Level-1B geometric correction. While the precise origin of the biases remains to be identified, we are able to estimate and reduce them in a re-calibration approach. This significantly improves time-variable gravity field solutions based on the CNES/GRGS processing strategy. Empirical assessments indicate that the systematic KBR data errors have previously induced gravity field errors on the level of 6-11 times the so-called GRACE baseline error level. The zonal coefficients (from degree 14) are particularly affected. The re-calibration reduces their rms errors by about 50%. As examples for geophysical inferences, the improvement enhances agreement between mass variations observed by GRACE and in-situ ocean bottom pressure observations. The improvement also importantly affects estimates of inter-annual mass variations of the Antarctic ice sheet