# COSMIC-2 Mission Summary at Three Years in Orbit
## 3 Requirements, Products, and Performance
### Benefits to NWP and Space Weather Operations and Research  
Over the last three decades GNSS RO has become a critical component of the global observing system for the study of weather, space weather, and climate applications due to its global coverage, vertical resolution, accuracy, low latency, and relatively low cost. COSMIC-2, now in its final operational deployment, is providing unprecedented geographic and local time sampling of the Earth's atmosphere and ionosphere with the highest signal-to-noise ratio data ever recorded in orbit. The unprecedented sampling provided by COSMIC-2 has unearthed new details on the broad spectrum of large- and small-scale waves near the tropical tropopause region [35]. The high SNR data allow COSMIC-2 soundings to penetrate through the troposphere closer to Earth's surface than other previously flown missions and to detect critically sharp layers on top of the atmospheric boundary layer that induce radio wave ducting called super-refraction [1]. For ionospheric sensing, the RO receiver and four antennas were uniquely designed to provide a wealth of TEC and scintillation observations for every tracked GNSS satellite, especially at low elevation angles that profile the F-layer. This extremely high-quality, low latency, and well-curated dataset made openly available to the science community is currently having significant impact on weather and space weather operations and will continue to benefit research for years to come.  
COSMIC-2 has been providing high-quality and low latency bending angle profiles per day to the community for NWP applications since early in the mission in late 2019. The high SNR and high-density sampling coverage up to 40 deg latitude have led to significant improvements in forecasting skill at operational centers. The US Navy and ECMWF centers found improvements in the shortrange forecast departures for temperature, humidity, and zonal/meridional components of the wind, for in situ observations, e.g., radiosonde, and remotely-sensed observations, e.g., ATMS satellite radiances [5]. They also found improvements to the 24 h forecasts as assessed by computing the adjoint-based forecast sensitivity to observation impact metric, and to medium range forecasts by verifying against operational analyses. The positive impact of COSMIC-2 data on tropospheric humidity is a significant new result and represents a large step forward for NWP skill improvement.  
Large- and small-scale variations of ionospheric electron density are important to monitor and predict, because they affect radio wave propagation and can impair satellite communication, navigation and electric power grid operations. The COSMIC-2 GNSS RO instrument has for the first time counted the total number of electrons between the receiver and GNSS transmitter, i.e., absolute TEC, to a demonstrated accuracy of < 3 \(\times\) 10\({}^{16}\) electrons/m\({}^{2}\)[15]. These high quality and low latency COSMIC-2 TEC data are now being transferred in near real-time to NOAA SWPC and US Air Force 557 th Weather Wing systems where they are being operationally assimilated to produce space weather forecasts. The TEC data as a function of altitude are also used to compute profiles of electron density (electrons/cm\({}^{3}\)) as a function of altitude, which have been validated with ground truth ionosonde stations around the globe that show agreement to an impressive \(\sim\)6-7% for quiet  
Figure 6: CDAAC COSMIC-2 data download volume and files in 2022.  
ionospheric conditions [14], and have been assimilated with positive impact into space weather prediction research models [9]. The COSMIC-2 GNSS RO scintillation observations are also being used to geolocate ionospheric irregularities with small uncertainty for use in operations and space weather research [36].