The CYGNSS Mission: On-Going Science Team Investigations

Abstract

In 2012, the National Aeronautics and Space Administration (NASA) selected the CYclone Global Navigation Satellite System (CYGNSS) mission coordinated by the University of Michigan (UM) as a low-cost and high-science Earth Venture Mission. The CYGNSS mission was originally proposed for ocean surface wind speed estimation over Tropical Cyclones (TCs) using Earth-reflected Global Positioning System (GPS) signals, as signals of opportunity. The orbital configuration of each CYGNSS satellite is a circular Low Earth Orbit (LEO) with an altitude ~520 km and an inclination angle of ~35°. Each single Delay Doppler Mapping Instrument (DDMI) aboard the eight CYGNSS microsatellites collects forward scattered signals along four specular directions (incidence angle of the incident wave equals incidence angle of the reflected wave) corresponding to four different transmitting GPS spacecrafts, simultaneously. As such, CYGNSS allows one to sample the Earth’s surface along 32 tracks simultaneously, within a wide range of the satellites’ elevation angles over tropical latitudes. Following the Earth Science Division 2020 Senior Review, NASA announced recently it is extending the CYGNSS mission through 30 September 2023. The extended CYGNSS mission phase is focused on both ocean and land surface scientific investigations. In addition to ocean surface wind speed estimation, CYGNSS has also shown a significant ability to retrieve several geophysical parameters over land surfaces, such as Soil Moisture Content (SMC), Above Ground Biomass (AGB), and surface water extent. The on-going science team investigations are presented in this article.

Using CYGNSS Data to Map Flood Inundation during the 2021 Extreme Precipitation in Henan Province, China

“…The short revisit time also demonstrates that CYGNSS is suitable for highly dynamic flood monitoring. With the launch of more GNSS-R satellites focusing on terrestrial applications in the future [56], there will be more high-quality and high-temporal-resolution space-borne GNSS-R data, which will undoubtedly further promote the development of GNSS-R land-surface and coastal-monitoring remote sensing.…”

Assessment of CYGNSS Wind Speed Retrievals in Tropical Cyclones

“…Table 1 summarizes the various CYGNSS wind datasets utilized in the analyses described here. Notice that we did not consider the older version SDR V2.1, and instead focus on the newer SDR V3.0 as a GPS calibration monitoring was implemented to reduce biases [10,19].…”

“…Our work focuses on validating all CYGNSS wind products that are currently available to the public in order to document the differences among them, illustrate advantages and shortcomings of each data product, and guide users in the optimal choice for their application/investigation. Most of these datasets have been independently validated by the team of investigators who developed them [13,[16][17][18][19], with analyses at the global scale, in collective statistics, at regional scales, and for sample tracks in storms. The main objective of this paper is to focus on wind observations within tropical cyclones.…”

Mapping Freezing and Thawing Surface State Periods With the CYGNSS Based F/T Seasonal Threshold Algorithm

“…At present, there is a lack of operational space-borne measurements of active layer thickness and extension. In this study, the CYGNSS mission GNSS-R data [4][5][6][7][8][9][10][11][12][13] are used to characterize F/T surface state changes due to water-ice phase conversion. These changes are an indirect measurement that can be used to characterize the active layer.…”