"Because the fundamental RO observation is a measurement of time, RO is a promising technique for climate monitoring. Atomic clocks can measure time with unequaled accuracy and stability. During an occultation, the GPS receiver measures the change in the flight time of the signal transmitted by the occulted GPS satellite. The clocks aboard the GPS obtained within 200 km and 1.5 h of each other in September and October 2006, but within 60° - 60°N. Although the data sample is not large, the results show that the mean temperature difference in the height range from 5 to 40 km is not significantly different from zero (as indicated by the standard error of the mean difference). These results support the claim of mission independence of RO temperature soundings in the 5 - 40km height range.
The COSMIC constellation, after full deployment into six orbital planes separated by 30°, continuously samples all local times. This is especially important for establishing a climate record, because it largely eliminates aliasing of the diurnal cycle and removes diurnal cycle biases" (*).
Ionospheric Research and Space Weather
"The GPS receivers on board the COSMIC satellites also generate a massive amount of ionospheric data including total electron content (TEC) and S4 scintillation indices along GPS-COSMIC radio links and vertical electron density profiles.. These data are valuable for evaluation of ionospheric models and use in space weather data assimilation systems. Many research groups running space weather models have begun to assimilate the TEC data and are seeing positive impact on ionospheric specification" (*).