P-BAND SIGNAL OF OPPORTUNITY FOR SNOW WATER EQUIVALENCE RETRIEVAL: FROM GROUND EXPERIMENT TO SPACE MISSION DESIGN

This study aims to provide an in-depth analysis of several space configurations for a future snow mission that utilizes P-band receivers in low earth orbit. The technique combines reflectometry with a sparse array of receivers in the forward direction to achieve higher resolution using the synthetic aperture radar (SAR) processing. The signal of opportunity (SoOP SAR) processing has a unique sampling pattern that is discontinuous, resulting in repeat retrievals with gaps in spatial coverage. The spatial resolution is ranging from about 100 meters on the edge of the swath to about 1-2km in the middle of the swath. The spatial coverage and temporal resolution are closely linked, with the goal of capturing snow accumulation between snow storms within a 12-day period and covering as much area as possible within the budget limit. To achieve this, simulations were conducted for 6-, 9-, and 12-day repeat orbits for 2, 3, and 4 receivers. Two ground track spacings (50m and 100m) were included in the analysis. The results show different spatial pattern but similar spatial coverage which provide flexibility in the orbit design and control. The swath width can reach above 200km. The in-swath coverage and resolution are illustrated for different configurations. The average swath gap for 2 receivers is about 6km and reduced to 2.8km when 4 receivers were simulated. In the end, we extended the analysis to four mountainous areas: highmountain Asia, Western United States, the Andes, and the Alps. The highest spatial coverage is about 90% by using 4 receivers with 12 days repeat configuration and will reduce to only about 25% for 2 receivers with 6 days repeat.