# On-Board Wind Scatterometry
###### Abstract  
Real-time (RT) ocean surface wind can make key improvements to disaster alarmingand safety of maritime navigation to avoid loss in property and human lives. Wind scatterometry is a well-acquainted way of obtaining good quality ocean surface winds, and it has been in application for decades. Existing wind-obtaining chains employ ground stations for receiving observations and can, at best, provide products in around 30 minutes for limited regions. In recent years, a satellite information-obtaining and transmission network is the new trend of Earth observation. In this research, on-board wind retrieval environment and procedures, which are different from traditional wind-obtaining chains, are proposed. First, the establishment of the on-board environment is instructed. Structures of each module are provided. The ground simulation system is been established based on this. After that, existing observing and processing routines of wind scatterometry are described, and then an on-board processing chain proposed and described. Modifications to existing satellite-ground chains are highlighted. The proposed method is validated in Level 0 data from the Chinese-French Oceanic SATellite (CFOSAT). Experiments indicate that the proposed on-board processing procedure can provide comparable results to ground-processed wind products. The root-mean-square error (RMSE) of wind speed for a track of data used in the experiment was about 0.26 m/s, and it was about 0.8\({}^{\circ}\) for wind direction. By decreasing wind field result quality, calculation time can be lessened in the on-board environment. However, it is found that in the whole chain of on-board wind generation, the most time-consuming procedure is observation-obtaining. The proposed on-board processing method can achieve good wind accuracy while meeting RT applications with good processing time. This provides a good complement to existing on-board-observing-ground-processing chains for RT applications. on-board processing; wind scatterometry; real-time 2020  
Scatterometers at work in space today include Advanced Scatterometer (ASCAT) -A, B, and C onboard Meteorological Operational satellite program (MetOp) series [12], the scatterometer onboard the Chinese-French Oceanic SATellite (CFOSAT), i.e. CFOSCAT [13], the scatterometers onboard Hai Yang-2 (HY-2)-A and B Satellites, i.e. HSCAT -A and B [14], and Oceansat-2 Scatterometer (OSCAT-2) onboard Scatterometer Satellite (ScatSAT) [15]. A dual-frequency scatterometer onboard the Feng Yun-3 (FY-3) Satellite is scheduled by the end of this year; it will be a good recruit to the scatterometer family [16]. Operational data processing procedures and systems for these spaceborne scatterometers have been well-established, being important parts in the applications listed above [17; 18; 19]. The traditional spaceborne scatterometer application chain starts from observations conducted by sensors, follows by signal detection, simple on-board signal processing, and relevant information generation. If necessary, all of those data are then compressed and downlinked with auxiliary data. Auxiliary data include satellite orientation and positioning information. These data form level 0 (L0) data when collected by ground stations. Higher levels of processing procedures that give products of wind fields are generally carried out after L0 data are distributed to processing agencies. Application institutes obtain higher levels of products via ground networks from them. State-of-the-art processing, transforming routines, and application modes have been developed to take advantage of well-located ground stations and networks. They are fast and stable. Advanced Retransmission Service (EARS) conducted by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) is a good example of networks of advanced high resolution picture transmission (AHRPT) reception stations. The wind products from EARS can be provided to end-users within 30 min (min) after observation [20].