The TriG digital beam steered sounder

Passive microwave sounding of global navigation system signals (GNSS) aka, GNSS radio occultation (GRO) produces measurements in the stratosphere and troposphere that contribute to two major societal benefits: monitoring climate and climate variability; and improving operational weather prediction. The high accuracy, precision and stability of GRO soundings make them ideal climate benchmark observations, suitable for monitoring long-term trends in the atmosphere. For weather applications, RO observations improve the accuracy of weather forecasts by providing temperature and moisture profiles of sub-km vertical resolution, over land and ocean and in the presence of clouds. Here we describe a cost effective approach to produce a flight-capable GRO instrument, the Tri-GNSS (GPS + Galileo+GLONASS) or TriG, receiver. The objective is to join digital beam forming technology from NASA´s Instrument Incubator Program (IIP) to the GNSS technology developed over the previous five years for upcoming NOAA and NASA GRO missions. The TriG receiver will employ the latest algorithms for GRO and precise orbit determination (POD) within a space hardened electronics package. This paper will describe testing of the digital beam forming method to be employed by TriG with the on-board processing of GRO limb-sounding profiles.