GPS World, January 2017

REMOTE SENSING NASAs Mini GNSS Satellites to Predict Weather S urrey Satellite Technologys Space GNSS Receiver Remote Sensing Instrument SGR ReSI is the primary payload onboard NASAs CYGNSS constellation launched Dec 15 from Cape Canaveral Air Force Station in Florida The Cyclone Global Navigation Satellite System CYGNSS mission is part of the NASA Earth System Science Pathfinder Program that aims to improve extreme weather prediction by studying how tropical cyclones form GNSS R The CYGNSS space segment consists of a constellation of eight micro satel lites each carrying the Surrey SGR ReSI as the observatory payload in the form of a delay Doppler mapping inst rument The inst rument collects ocean surface roughness data using a technique called GNSS reflectometry GNSS R providing CYGNSS with a new method for looking inside hurricanes Wind speed will be estimated from the data Earth Science Constellation CYGNSS is NASAs first Earth science small satellite constellation designed to help improve forecasts of hurricane intensity hurricane tracks and storm surges CYGNSS will measure previously unknown details crucial to accurately understanding the formation and intensity of tropical cyclones and hurricanes At 510 km above the Earths surface the eight CYGNSS microsatellite observatories are deployed in pairs Image credit University of Michigan As a constel lation of eight spacecraft CYGNSS will do what a single craft cant in terms of measuring surface wind speeds inside hurricanes and tropical cyclones at high time resolution to improve our ability to understand and predict how these deadly storms develop said Thomas Zurbuchen associate administrator for NASAs Science Mission Directorate The CYGNSS mission is expected to lead to more accurate weather forecasts of wind speeds and storm surges Its constellation of eight microsatellite observatories will measure surface roughness of the worlds oceans with data collected used to calculate surface wind speeds and provide a better picture of a storms strength and intensity Inner Core The intense rain in eyewalls blocks the view of the inner core by conventional satellites CYGNSS can penetrate the eyewall to gather data about a storms intense inner core The inner core engine of the storm extracts energy from the warm surface water via 70 GPS WORLD WWW GPSWORLD COM JANUARY 2017 evaporation into the atmosphere The latent heat in the water vapor is then released into the atmosphere by condensation and precipitation The CYGNSS observatories will continuously monitor surface winds across Earths tropical hurricane belt Each satellite is capable of capturing four wind measurements per second adding as many as 32 wind measurements per second for the entire constellation Break away of a CYGNSS micro satellite Image Southwest Research Institute collecting data Each CYGNSS microsatellite receives direct GPS signals to locate the observatory as well as signals reflected off the ocean surface to determine wind speed The specular point is where the scattering originates if the surface is perfectly smooth With a roughened surface the scattering originates from a diffuse region called the glistening zone centered on the specular point Image University of Michigan