## Processing Setup and Description  
### Data and Tools  
The processing setup presented in this study depends on various data sources (see also Figure 1): The GNSS transmitter satellite orbits are acquired from analysis centers (ACs) of the well-established International GNSS Service IGS, whereas data for the GPS-based POD of the receiver satellites in LEO are provided by the respective mission operators and scientific RO groups. SLR data are obtained from the International Laser Ranging Service (ILRS, [[https://ilrs.cddis.eosdis.nasa.gov/data_and_products/data_centers](https://ilrs.cddis.eosdis.nasa.gov/data_and_products/data_centers)]([https://ilrs.cddis.eosdis.nasa.gov/data_and_products/data_centers](https://ilrs.cddis.eosdis.nasa.gov/data_and_products/data_centers))) [57; 58], as a service of the International Association of Geodesy. The GNSS orbit, clock, and Earth orientation parameter (EOP) are taken from the CODE reprocessing product series 2015 (repro2015, [[https://dx.doi.org/10.7892/boris.75876.3](https://dx.doi.org/10.7892/boris.75876.3)]([https://dx.doi.org/10.7892/boris.75876.3](https://dx.doi.org/10.7892/boris.75876.3))) [59] and for mutual cross-check of the derived LEO orbits from the IGS second reprocessing (repro2, [[http://acc.igs.org/reprocess2.html](http://acc.igs.org/reprocess2.html)]([http://acc.igs.org/reprocess2.html](http://acc.igs.org/reprocess2.html))) [60]. The IGS multi-AC product combines weighted solutions from 9 contributing ACs, one of which is CODE. Although the combined IGS solutions comply with an orbit accuracy of 2.5 cm in satellite position and 75 ps in satellite clock ([[http://www.igs.org/products](http://www.igs.org/products)]([http://www.igs.org/products](http://www.igs.org/products))) [61; 62], their implementation for RO-oriented POD is limited through the lack of provision of clock products at 30 s sampling within repro2 [63]. The CODE reprocessing series repro2015, on the contrary, offers clock estimates with a sampling of 5 s starting January 1, 2003, in addition to 30 s clocks [64]. Another substantial difference to previous versions of the CODE reprocessing is the first use of the extended Empirical CODE Orbit Model (ECOM2) within repro2015 [65]. The present 5 min clock sampling of the combined IGS solution induces a deterioration of the clock interpolation to high rate occultation data at 50 Hz sampling rate and thus also in the subsequent RO processing. Therefore the JPL solution (another highly weighted orbit product within IGS repro2 besides CODE) is currently selected, for cross-check, as a second GNSS orbit input dataset. This will be revised with the availability of the upcoming third reprocessing of the IGS ([[http://acc.igs.org/repro3/repro3.html](http://acc.igs.org/repro3/repro3.html)]([http://acc.igs.org/repro3/repro3.html](http://acc.igs.org/repro3/repro3.html))). Both data centers provide long-term stable data products until February 2015 with consistent alignment to ITRF2008. With regard to the impending POD reprocessing effort of the continuous RO era at WEGC starting from 2001 up to recently, both data sets are prolonged with final products from CODE and IGS, which are aligned to ITRF2014. GPS receivers onboard of RO satellites record navigation tracking data from the zenith antenna for orbit processing and occultation tracking data from the limb-looking atmospheric sounding antenna(s) (Section 2). For POD with Bernese and NAPEOS the binary data from the receiver are either already provided in, or need to be converted to Receiver Independent Exchange Format (RINEX) [66]. Additionally, information in form of either measured or simulated Euler angles or quaternions provides knowledge on the satellite's attitude.