Why will CYGNSS use eight microsatellites instead of just one?
The CYGNSS microsatellites will be placed into a Low Earth Orbit (LEO) that will keep the satellites approximately 500km above the surface of the Earth. This orbit is considerable lower than the 36,000km orbits used by the Geostationary Operational Environmental Satellites (GOES) that provide the cloud imagery that you can observe on your favorite weather website or local television weathercast.
Since the area of interest for the CYGNSS mission is the tropics (where hurricanes form and intensify), the CYGNSS orbit will be designed to cover only that portion of the Earth surface from 35°S latitude, across the equator, to 35°N latitude. Given these constraints, a single CYGNSS microsatellite will only pass over the same location on the Earth’s surface approximately once every 24 hours. Through the use of a constellation of eight microsatellites, CYGNSS will provide nearly gap-free coverage of the tropics with a revisit time of three hours (median) and six hours (average) over the full +/- 35° latitude region. This faster revisit time will allow CYGNSS to provide frequent observations of rapidly changing conditions within the eyewall of hurricanes, thus helping NASA scientists and hurricane forecasters to provide advanced warning of the potential impact of hurricanes on vulnerable coastal communities.
Is it true that CYGNSS will be able to determine the wind speed within the core of hurricanes using the same Global Positioning Satellites that are used for GPS navigation in cars?
Yes! 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) pinpoint microsatellite positions, while the reflected signals (received by the nadir antenna) respond to ocean surface roughness, from which the wind speed is retrieved. Each microsatellite is capable of measuring four simultaneous reflections, resulting in 32 wind measurements per second across the globe.
How will CYGNSS advance our understanding of hurricanes?
Although the accuracy of hurricane track forecasts has improved significantly over the past two decades, there has been very little improvement in hurricane intensity forecasts. With a constellation of eight microsatellite observatories, CYGNSS will improve hurricane forecasts by measuring ocean surface wind speeds in and near the inner core of hurricanes: a key indicator of hurricane intensity.
What will CYGNSS be able to do that other space-based instruments have not been able to do?
Previous space-based instruments have suffered from the fact that the signal used to measure ocean surface wind speed is degraded as it passes through the heavy tropical rainfall typically associated with hurricanes. In contrast, CYGNSS will be able to peer through the intense tropical rainfall associated with hurricane eyewalls and spiral rainbands, allowing scientists to probe the inner core of hurricanes for the first time. The resulting quality and quantity of ocean surface wind speed data to be provided by CYGNSS will allow hurricane forecasters to improve weather forecast models used to predict both the track and intensity of land-falling hurricanes.
Are any of the weather or hurricane forecasting communities engaged in the CYGNSS project? If so, how?
Yes! The CYGNSS project has engaged an extended science team that includes participants from the U.S. Federal Government, research laboratories, academia, the private sector and international partners that include members of the hurricane forecasting communities. While the CYGNSS science team will be responsible for processing of the raw data and ultimately generating gridded ocean roughness and wind speed data products, the extended partners will be using these products in ways that will ultimately help to transition the data usage from research to operations.