## 6 Conclusions  
This paper presents the processing, data products and applications of a type of low level GNSS-R data set, i.e., the raw IF data, collected by different spaceborne GNSS-R missions. The unprocessed nature of these raw IF data provides an unique opportunity to explore the potential of GNSS-R technique for advanced GNSS-R applications and future spaceborne missions. Limited by the amount of available raw IF data collection, it is not possible to demonstrate any operational applications with these raw IF data sets. However, the post-processing of the raw IF data can make complements to the available higher level GNSS-R data (e.g., Level 1 power DDM data). To facilitate such explorations, a dedicated GNSS-R software receiver was developed by the Institute of Space Sciences (IEEC, CSIC), and corresponding data products have been generated from the raw IF datasets collected by different missions. The main data product of the raw IF data processing, i.e., the complex waveform data, is publicly available for the TDS-1 and CYGNSS missions through ICE-CSIC/IEEC's public open-data server. The format and variables of the data products are introduced in detail. To facilitate the users accessing and processing of the data products, a software tool is also provided and introduced. With the available complex waveform products and the corresponding processing tools, different aspects of the GNSS-R concept can be investigated. One of the main features of the products is that it provides GNSS-R waveforms from multi-GNSS and at multi-frequency, which can help the community to optimize the processing algorithms and analyse the link budgets of the other GNSS signals than only GPS L1 C/A signal. In addition, the complex data products provide both the amplitude and the phase information of the reflected signal at high sampling resolution (i.e., 1000 Hz), which can provide extra information to characterize the surface coherence properties or even to make high precision surface height measurements. A few examples of possible applications, such as inland water detection and surface altimetry, have been demonstrated in this paper. By making these complex waveform data products publicly available, new geophysical applications of the GNSS-R technique can be further explored by the community. Such explorations are of relevance at the moments, as the next ESA GNSS-R mission, HydroGNSS, will include for the first time ever, operational and continuous generation of these complex observations. The data products will keep updating with the availability of new spaceborne GNSS-R raw IF data sets. For example, the ESA Scout-2 HydroGNSS mission (expected to be launched in H2 2024) is capable of collecting raw IF data at different frequencies and polarizations. Being selected as the official Level 0 raw IF data processor, ICE-CSIC/IEEC's software receiver will provide the complex waveform products with more advanced features. Moreover, new data products will be also developed by reprocessing the raw IF data with different algorithms or strategies, e.g., the complex or power DDM product with higher delay/Doppler resolution, the GNSS-R observation with stare or focused processing strategies [34], which will be also provided in the same data server. Conceptualization, W.L. ; methodology, W.L. ; software, W.L., A.R., S.R. and E.C. ; validation, W.L. and E.C. ; data curation, S.R. and S.O. ; writing--original draft preparation, W.L. ; writing--review and editing, E.C., S.R. and A.R. ; visualization, W.L. and A.R. ; project administration, E.C. and S.R. ; funding acquisition, E.C. and W.L. All authors have read and agreed to the published version of the manuscript. This work of [PERSON] was supported by the Spanish Ministry of Science, Innovation and Universities through the Ramon y Cajal Program (No. RYC2019-027000-I). This research was partially funded by Spanish National Research Council (20215 AT007) and the Spanish Ministry of Science, Innovation and Universities grant number RTI2018-099008-B-C22/AEI/10.13039/501100011033/FEDER, EU.