GNSS Instrument System for Multi-static and Occultation Sensing

The Purdue GPS multistatic and occultation instrument for atmospheric, land, and ocean remote sensing (GISMOS) is an instrument to measure the water vapor distribution in the troposphere by inversion of the bending angle profile produced during occultation of a GPS satellite by the limb of the Earth. The instrument also uses GPS signals reflected from land or ocean to determine properties of those surfaces (soil moisture and surface roughness, respectively). Occultation samples represent distances of ca. 300 km and so are complementary to the single-point measurements obtained by conventional soundings. The instrument is a passive remote-sensing system that records the full bandwidth (intermediate frequency) of the GPS signals and stores the measurements on hard disks for subsequent analyses.