Ocean Altimetry and Wind Applications of a GNSS Nanosatellite Constellation

Recent developments in electronics and nanosatellite technologies combined with modeling techniques developed over the past 20 years have enabled a new class of altimetry and wind remote sensing capabilities that offer markedly improved performance over existing observatories while opening avenues to new applications. Most existing spaceborne ocean altimetry and wind observatories are in polar low Earth orbits that maximize global coverage but result in either large gaps at the tropics or long time intervals between geolocation measurement revisits. This, combined with their use of radar systems operating in the C and Ku-bands, obscures key information about the ocean and the global climate. Using GNSS-based bi-static scatterometry performed by a constellation of nanosatellites in a non-polar low Earth orbit could provide ocean altimetry and wind data with unprecedented temporal resolution and spatial coverage across the full dynamic range of ocean wind speeds in all precipitating conditions – all with a system cost substantially less than existing and planned systems. This paper contrasts the performance of a GNSS nanosatellite constellation with the existing monolithic remote sensing observatories while identifying synergies of the systems that can be exploited to achieve a more complete understanding of both ocean current and wind phenomena. Two specific applications are reviewed; ocean winds and ocean wave altimetry. The recently awarded Cyclone Global Navigation Satellite System (CYGNSS) mission will be used for the ocean wind comparison while a notional GNSS constellation will be used for comparison of the ocean wave altimetry application. Design requirements, applications, and system implementation are presented for the GNSS nanosatellite constellation.