## 6 Conclusions, Discussions, and Potential Applications
Note that the first official release (provisional release) of the COSMIC-2 data product covered the period before February 2020. Validated COSMIC-2 data became available on a real-time operational basis to international NWP centers via the Global Telecommunication System (GTS) on 16 March 2020. Because the phase delay of COSMIC-2 data can be traced to the SI time unit, the quality of COSMIC-2 neutral atmospheric profiles does not change before or after the data became validated. The initial and operational observations are processed and validated equally. Despite using \"provisional\" data in this study, this study's findings shall also apply to all data. NOAA's National Weather Service (NWS) began parallel testing of the Global Forecast System (GFS) model with and without COSMIC-2 bending angle profiles assimilated shortly after the validated COSMIC-2 data became available, using code and settings adapted from the preliminary non-real-time GFS data forecast impact assessments. In this case, NWS assimilated more limited pre-validated COSMIC-2 observations by its partners in the Joint Center for Satellite Data Assimilation (JCSDA), including NCEP itself, NESDIS/STAR, NOAA/OAR (Oceanic and Atmospheric Research), UCAR, and the U.S. Air Force and U.S. Navy. Following some adjustments to the data assimilation procedure, the COSMIC-2 data demonstrated improved forecast impact when added to the operational GFS. We started to assimilate COSMIC-2 data operationally on 26 May 2020. While beneficial, the initial implementation is not yet optimized to exploit the advanced capabilities of COSMIC-2 over other RO sensors and missions. Currently, COSMIC-2 data are still used in the same manner as had been tailored for COSMIC-1. Additional development and testing will be conducted to take advantage of the information that COSMIC-2 provided in the moist lower troposphere to improve forecasts further. Efforts also are being made to develop improved forward operators that will increase the impact of all GNSS RO data, including COSMIC-2. The NESDIS Center for Satellite Applications and Research (STAR) has become the NOAA GNSS RO operation, data monitoring, and science center ([[https://ncc.nesdis.noaa.gov/GNSSRO/ICVS/index.php](https://ncc.nesdis.noaa.gov/GNSSRO/ICVS/index.php)]([https://ncc.nesdis.noaa.gov/GNSSRO/ICVS/index.php](https://ncc.nesdis.noaa.gov/GNSSRO/ICVS/index.php))). STAR also develops RO data processing package to convert COSMIC-2 L0 data to excess phase [19] and using a Full Spectrum Inversion (FSI) package to convert excess phase to bending angle and refractivity profiles [18]. STAR also developed its independent 1D-var package to covert COSMIC-2 refractivity to temperature and moisture profiles [20]. We will compare the independently derived STAR COSMIC-2 retrievals to those from the UCAR to quantify the implementation-related uncertainties. That will be for future studies. Conceptualization and methodology, S.-p.H. ; software, data curation, formal analysis, validation and investigation, X.Z., X.S., B.Z., L.A., S.K., Y.H., and E.L.; writing--original draft preparation, S.-p.H. ; writing--review and editing, S.-p.H., J.G.Y., and W.X.-S.; resources and supervision, S.-p.H. ; project administration and funding acquisition, S.-p.H., J.G.Y., and W.X.-S. All authors have read and agreed to the published version of the manuscript. This study was funded by NOAA NESDIS Office of Projects, Planning, and Analysis. The scientific results and conclusions, as well as any views or opinions expressed herein, are those of the author(s) and do not necessarily reflect those of NOAA or the Department of Commerce. The authors declare no conflict of interest.