Transition of Research to Operations in GPS Radio Occultation: From COSMIC to COSMIC-II

The atmospheric limb sounding technique making use of radio signals transmitted by the Global Position System (GPS) satellites has emerged as a powerful and relatively inexpensive approach for sounding the global atmosphere in all weather. The proof-of-concept GPS Meteorology (GPS/MET) mission (1995-1997) first demonstrated the potential of GPS radio occultation (RO) technique in atmospheric remote sensing. More recently, CHAMP and SAC-C missions (both launched in 2000) provided further evidence that the GPS radio occultation (RO) sounding data are of high precision, accuracy and vertical resolution. The launch of the joint U.S.-Taiwan COSMIC/FORMOSAT-3 (hereafter COSMIC) mission, a constellation of six microsatellites, marked the beginning of a new era of GPS atmospheric remote sensing. Since its launch in April 2006 COSMIC has been providing large number GPS RO soundings to support the research and operational communities. As of September 2010, COSMIC has taken 2.5 million neutral atmospheric RO soundings, and 2.6 million of ionospheric RO soundings, serving a total of 1400 users from 54 countries. On average, COSMIC provides 1,500 ~2,500 GPS RO soundings per day, uniformly distributed around the globe.

COSMIC is a demonstration project, with 90% of the data available within 3 hr of observations. Several global operational centers, including ECMWF, NCEP, UKMO, Meteo France, and MSC, are assimilating COSMIC data for global weather prediction, and have all demonstrated significant positive impacts. The fundamental observables of GPS RO soundings are phase and amplitude of radio waves. They are not subject to instrument drifts or satellite-to-satellite biases. Therefore, they are one of the most stable measurements for climate monitoring. Recent analysis of COSMIC data processed by four different processing centers has provided further support on the stability of GPS RO data for climate monitoring. COSMIC satellites are expected to have a five-year mission life. Starting in 2011, we can anticipate gradual degradation of the constellation. Through collaboration between U.S. and Taiwan, NOAA and NSPO have started the process to develop a follow-on mission, known as COSMIC-II. The design of COSMIC-II calls for a 12-satellite constellation, each equipped with an advanced Tri-G receiver, capable of tracking radio signals from GPS, GALILEO, and GLONASS navigation systems. The first launch is expected in late 2014 to early 2015. COSMIC-II will be an operational mission, supporting weather, climate and space weather needs. In this presentation, we will highlight the key results from COSMIC, and discuss the design of COSMIC-II. We will also discuss issues related to transition from research to operations.