Sea Surface Wind Speed Retrieval using NanYue (NY) GNSS Reflectometry
Nanyue (NY) science satellite, launched on 27 July 2022, is one of China’s commercial small satellites. NY satellite has an 500km Solar synchronous orbit, and revisit time of 3 to 7 days. The GNSS reflectometry (GNSS-R) onboard NY satellite is an operational GNSS remote sensor whose six antennas can receive reflected signals from multiple GNSS systems. Two channels are used to process GPS signals and another two channels are used for BDS signals. The NY GNSS-R delay-Doppler map (DDM) output is with 150 (time delays) × 15 (Doppler frequencies). The resolution of Doppler is 500 Hz from −3500 to 3500 Hz, and the resolution of delay is 0.25 chip from −15 to 15 chips.
This paper introduces the GNSS-R aspect of NY satellite, including the instrument, power calibration and wind speed retrieval algorithm. Preliminary validation results for its almost six months of NY real measurements are also presented. After preliminary quality control using SNR (Signal-Noise Ratio), elevation and other parameters, DDM observable “DDMA” (Delay-Doppler Map Average), which is the characteristic value depending on wind speed as well as sea surface roughness, is to establish the GMF (Geophysical Model Function) model with ECMWF (European Centre for Medium-Range Weather Forecasts) reanalysis winds for wind speed inversion by 25km spatial resolution. NY will provide new GNSS-R dataset chance for studying sea surface wind speed retrieval.
