Long-baseline Comparisons of the Brazilian National Time Scale to Utc (nist) Using near Real-time and Postprocessed Solutions

We present the results of C/A code common-view Global Positioning System (GPS) comparisons between the UTC (NIST) time scale, located at the National Institute of Standards and Technology (NIST) in Boulder, Colorado, and the Brazilian national time scale, UTC(ONRJ), located at the National Observatory (ONRJ) in Rio de Janeiro, Brazil. The two time scales are separated by a long baseline of ~8600 km. The comparisons were made with measurement systems developed for the Sistema Interamericano de Metrologia (SIM) comparison network, a network designed to intercompare the national standards of time and frequency in North, Central, and South America. Data from four different types of measurements are presented, two of which involve near real-time processing and two that involve postprocessing. The near real-time comparisons apply the ionospheric corrections broadcast by the GPS satellites to the measurements recorded at both sites. The data are then reduced both as “classic” common-view, where only the satellites simultaneously in view at both sites are used in the solution, and as all-in-view, where all of the satellites received at both sites are used in the solution. The postprocessed comparisons apply measured ionospheric delay corrections to the measurements recorded at both sites before proceeding with the common-view and all-in-view data reduction. The results obtained from each of the measurements are compared and summarized.