The Cyclone Global Navigation Satellite System (CYGNSS) is a constellation of eight microsatellites that will use existing Global Positioning System (GPS) satellites to obtain estimates of surface winds near the core of hurricanes, including regions beneath the eyewall and intense inner-rain bands, that could not previously be measured from space. This information will allow NASA scientists and hurricane forecasters to provide improved advanced warning of hurricane intensification, movement and storm surge location / magnitude, thus aiding in the protection of human life and coastal community preparedness. Storm surge is an abnormal rise of water, over and above the expected water levels that would result from astronomical tides. In many cases, a significant fraction of a hurricane’s impact on a coastal community is related to the destructive nature of the storm surge associated with hurricanes.
Each CYGNSS microsatellite will receive both direct and reﬂected signals from Global Positioning System (GPS) satellites. The direct signals from the GPS (received with the zenith antenna) will pinpoint observatory positions, while the reﬂected signals (received by the nadir antenna) respond to ocean surface roughness, from which the wind speed will be retrieved. Each microsatellite will be capable of measuring four simultaneous reﬂections, resulting in 32 wind measurements per second across the globe. The constellation of eight CYGNSS microsatellites will be deployed in Low Earth Orbit (LEO) at approximately 510 km above the surface and at an inclination of approximately 35° from the equator. The complete constellation will provide nearly gap-free Earth coverage with a revisit time of 3 hours (median) and 6 hours (mean) over the full +/- 35° latitude region.
The surface wind data collected by the CYGNSS constellation of microsatellites will lead to improved spatial and temporal resolution of the surface wind ﬁeld within the precipitating core of tropical cyclones, an enhanced understanding of the momentum and energy ﬂuxes at the air-sea interface within the core of tropical cyclones and the role of these ﬂuxes in the maintenance and intensification of these storms, and refined forecasting capabilities of tropical storm intensification.
Combined, these accomplishments will allow NASA scientists and hurricane forecasters to provide improved advanced warning of hurricane intensification, movement and storm surge location and magnitude, thus aiding in the protection of human life and coastal community preparedness.