Gnss radio occultation (RO) data are a major contributor for climate modeling, weather forecasting, and ionospheric monitoring. An important observable in gnss RO measurement is the signal carrier…

This $252,092 grant from the National Aeronautics and Space Administration (NASA) to the Regents of the University of Colorado, Boulder (doing business as the University of Colorado) will fund research to detect and mitigate carrier phase cycle slips in global navigation satellite system (GNSS) radio occultation (RO) data. The research aims to improve the accuracy of tropospheric and ionospheric profiles derived from the GNSS RO measurements collected by Spire Global's CubeSat constellation. The results will be analyzed in conjunction with data from the COSMIC-2 program to evaluate the quality of the Spire measurements and the feasibility of using low-cost small satellite systems for global remote sensing of the troposphere and ionosphere. This grant-funded research project does not have a set-aside designation.

Gnss radio occultation (RO) data are a major contributor for climate modeling, weather forecasting, and ionospheric monitoring. An important observable in gnss RO measurement is the signal carrier phase. However, carrier phase tracking is the weak link in gnss receiver signal processing, especially for RO signals propagating through lower tropospheric structures and ionospheric plasma irregularities. Open loop (OL) tracking has been adopted by most RO constellations, including spire global cubesats, to improve the robustness of the carrier phase estimation process. A major pitfall of the OL tracking is the high noise level and carrier cycle slips which lead to bias and errors in retrieved tropospheric and ionospheric profiles. This proposed effort will apply the latest techniques developed by the proposal team to detect and mitigate the carrier phase estimation noise and cycle slips to the gnss RO data obtained by spire global cubesats. The results will be used to establish patterns of cycle slip behavior and the atmospheric or ionospheric conditions under which cycle slip occurs. Improvements in tropospheric and ionospheric profiles retrieved from the spire cubesat data after application of the cycle slip mitigation methods will be quantified. Finally, the processing results will be analyzed in conjunction with cosmic 2 data collected in the vicinity of spire data at similar times to evaluate the quality of the spire measurements. The results will offer a comprehensive assessment of the feasibility of low-cost small satellite constellations as a source for global troposphere and ionosphere remote sensing and for enabling high accuracy earth and space sciences applications.