The Muon Space GNSS-R Surface Soil Moisture Product

Muon Space is building a constellation of small satellites, many of which will carry global navigation satellite system (GNSS) reflectometry (GNSS-R) receivers. In preparation for the launch of this constellation, we have developed a generalized deep learning retrieval pipeline, which now produces operational GNSS-R soil moisture (SM) retrievals using data from NASA’s Cyclone GNSS (CYGNSS) mission. This record includes the complete set of these retrievals from August 1, 2018 until September 26, 2024 in the form of individual "tracks" aggregated into daily, per receiver, files (Level 2 data), along with hourly and daily gridded files (Level 3 data) from the entire constellation. The Muon Space CYGNSS SM product achieves improvements in spatial resolution over SMAP with comparable performance in many regions. An ubRMSE of 0.032 cm3 cm-3 for in situ SM observations from SMAP core validation sites has been demonstrated, though performance is lower than SMAP in forests and/or mountainous terrain. The Muon Space product outperforms the official v1.0 CYGNSS SM product in many measures. This initial release serves as the foundation of the Muon Space operational SM product, which soon will additionally include data from Muon Space satellites. A manuscript describing both the processes involved in generating these SM retrievals, as well as the product files in detail, is available here. A code repository demonstrating simple visualization of these data files is available here. Access to an operational version of the SM datasets will be available from this landing page in Q1 of 2025.