Geometric considerations for the remote monitoring of volcanoes: studies of lava domes using ATSR and the implications for MODIS
Data from the Moderate Resolution Imaging Spectrometer (MODIS) may be used for the thermal monitoring of volcanoes from the NASA Earth Observing System. MODIS uses a wide scan angle to provide a high temporal frequency but this geometry means that zenith angle and pixel size vary greatly across the swath. Similar variations are inherent in radiometric data obtained from the forward- and nadir-views of the Along Track Scanning Radiometer (ATSR) and here we use dual-view ATSR data of volcanic lava domes to investigate how these geometric effects influence the retrieved thermal anomalies. The effect of increasing pixel size with zenith angle is shown to be counteracted by increasing pixel overlap, thus providing comparable thermal anomalies from the two ATSR views in cases where off-nadir obscuration by crater walls is not significant. In such instances data from the majority of the MODIS swath could be combined in a single time-series in order to maximise temporal coverage for volcano monitoring purposes.