Abstract
In the framework of the European Gravity Service for Improved Emergency Management (EGSIEM) project, consistent sets of state-of-the-art reprocessed Global Navigation Satellite System (GNSS) orbits and satellite clock corrections have been generated. The reprocessing campaign includes data starting in 1994 and follows the Center for Orbit Determination in Europe (CODE) processing strategy, in particular exploiting the extended version of the empirical CODE Orbit Model (ECOM). Satellite orbits are provided for Global Positioning System (GPS) satellites since 1994 and for Globalnaya Navigatsionnaya Sputnikovaya Sistema (GLONASS) since 2002. In addition, a consistent set of GPS satellite clock corrections with 30 s sampling has been generated from 2000 and with 5 s sampling from 2003 onwards. For the first time in a reprocessing scheme, GLONASS satellite clock corrections with 30 s sampling from 2008 and 5 s from 2010 onwards were also generated. The benefit with respect to earlier reprocessing series is demonstrated in terms of polar motion coordinates. GNSS satellite clock corrections are validated in terms of completeness, Allan deviation, and precise point positioning (PPP) using terrestrial stations. In addition, the products herein were validated with Gravity Recovery and Climate Experiment (GRACE) precise orbit determination (POD) and Satellite Laser Ranging (SLR). The dataset is publicly available.
Highlights
Within the framework of the European Gravity Service for Improved Emergency Management (EGSIEM) [1] project, different monthly gravity field solutions derived from the Gravity Recovery and Climate Experiment (GRACE) [2] mission were compared and combined [3,4]
A consistent use of reference frame products (Earth rotation parameters (ERP), Global Positioning System (GPS) satellite orbits and clock corrections) at all EGSIEM processing centers was a prerequisite for comparability of the precise GRACE orbits, and the gravity fields derived thereof
A rigorously combined processing scheme using GPS and Globalnaya Navigatsionnaya Sputnikovaya Sistema (GLONASS) measurements was used, according to the processing standards applied for the International GNSS Service (IGS) activities at Center for Orbit Determination in Europe (CODE) [6]
Summary
Within the framework of the European Gravity Service for Improved Emergency Management (EGSIEM) [1] project, different monthly gravity field solutions derived from the Gravity Recovery and Climate Experiment (GRACE) [2] mission were compared and combined [3,4]. The main objective of the project was to demonstrate that the observations of the redistributions of water and ice mass, as derived from GRACE inter-satellite ranging, provide critical and complementary information to more traditional Earth observation data, e.g., optical or radar measurements. A consistent use of reference frame products (Earth rotation parameters (ERP), Global Positioning System (GPS) satellite orbits and clock corrections) at all EGSIEM processing centers was a prerequisite for comparability of the precise GRACE orbits, and the gravity fields derived thereof. The reference frame products provide the link between the geometrical (station coordinates) and physical (gravity field) shape of the Earth. For kinematic precise orbit determination (POD) of Low Earth Orbiting (LEO) satellites such as GRACE, precise point positioning (PPP) [5] is a well-established technique. The procedure requires precise and more importantly, consistent GPS orbits and satellite clock corrections. The Center for Orbit Determination in Europe (CODE) [6] started to generate GPS clock corrections with a 30 s sampling rate as early as 1999 [7] and with a 5 s sampling rate in 2008 [8]
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