ASSESSMENT OF INSAR COHERENCE DATA FOR APPLICATION TO STUDY THE BONNEVILLE SALT FLATS, UTAH: HARNESSING ALASKA SATELLITE FACILITY CLOUD-BASED INSAR DATA PROCESSING

Renowned worldwide, the extensive salt crust of the Bonneville Salt Flats in northwestern Utah is important for regional air quality, hydrology, and resources. Prior research has demonstrated that the salt crust is undergoing rapid change, including decreasing salt crust extent and volume since the mid-1900’s. As the landscape rapidly evolves, it is necessary to carry out regular assessments of crustal properties and extent to inform land managers, future research, and the public. While optical remote sensing techniques have proven useful for assessing the mineralogy and extent of the Bonneville Salt Flats salt crust, the use of Interferometric Synthetic Aperture Radar (InSAR) has been notably rare within the context of the salt crust, likely due to the complexity of processing and need for more established methods. To investigate the potential of InSAR for studying and monitoring the Bonneville Salt Flats, we analyze coherence imagery from over 20 Sentinel-1 (European Space Agency) C-band InSAR pairs from the summers of 2020-2023, processed to 80 m resolution using the Alaska Satellite Facility VERTEX service. We evaluate coherence imagery to ascertain the suitability for surface offset and phase closure analyses, effects of temporal and spatial baselines on coherence, differences between ascending/descending pairs (evening/morning acquisitions), and detectable environmental or anthropogenic processes. Initial results indicate that the spatially averaged coherence is high (>0.9) for all pairs and there are small (~0.01) but consistent differences in coherence when comparing ascending and descending InSAR pair datasets. In addition, the preliminary results show that spatial baseline (distance between InSAR pairs) has no noticeable effect on coherence while temporal baseline has a significant effect. Environmental changes such as diurnal changes in surface moisture appear to be observable given consistent coherence differences between ascending and descending observations. Likewise, anthropogenic surface wetting and surface compaction (racetrack preparation and use) are observable as spatial zones with lower relative coherence. These assessments of spatial patterns from InSAR coherence images will advance the understanding of drivers of landscape change at the Bonneville Salt Flats.