Overview of the Delay Doppler Mapping Instrument (DDMI) for the cyclone global navigation satellite systems mission (CYGNSS)

The CYGNSS satellite constellation consists of eight satellites equipped with GNSS bi-static radar receivers which map the ocean surface scattered signal power in the vicinity of the specular reflection point using time domain and Doppler frequency filters. The satellites orbit in the same plane at an altitude of 500 km and at a orbit inclination of 35 degrees. CYGNSS will act as a GNSS bi-static scatterometer capable of sensing sea level winds in tropical cyclones, including in high precipitation conditions. An overview of the GNSS remote sensing concept is included in this paper. Subsequently, an overview of the Delay Doppler Mapping Instrument (DDMI) carried by all of the CYGNSS observatories will be presented. The DDMI uses GPS forward scattered signals of opportunity to produce delay Doppler maps (DDMs) of the scattered signal delay and frequency spreading over the surface. This paper will conclude with results from preliminary laboratory testing of the CYGNSS instrument engineering models.