Characterization of GLONASS Broadcast Clock and Ephemeris: Nominal Performance and Fault Trends for ARAIM

Validation of the Unfaulted Error Bounds for ARAIM

“…GLONASS has had more variability in its performance over time. In between 1998 and 2009 the constellation was well below full size . In 2015, just before the paper describing expected performance was presented to ICAO , the number of observed GLONASS faults was decreasing.…”

“…Unfortunately, there is no indication for the age of data in the GLONASS broadcast navigation data, so we are unable to perform a similar analysis as was done for GPS in Figure . However, previous research has observed worse accuracy in satellites that were farther from Russia, where the GLONASS upload stations are located . GLONASS is adding more observation and upload sites, so that behavior may not hold true after these sites are incorporated.…”

“…A noticeable difference from the GPS plot is the presence of faults as indicated by the red markers (circles for clock faults, squares for ephemeris faults, and asterisks for uncategorized faults). There were many faults observed during this period including a constellation wide fault on April 1, 2014, where all satellites experienced large ephemeris errors. As mentioned above, all errors greater than 70 m were removed from subsequent processing.…”

“…We have performed a similar analysis on the GLONASS constellation . As was done for GPS, we have analyzed all of 2013 through all of 2016.…”

“…In reviewing the data, we found relatively few GLONASS errors whose magnitudes were between 25 and 70 m . If the commitment were changed such that errors greater than 25 m were claimed to occur with a probability below 10 −4 per satellite, then a floor value for σ URA of just ~6.5 m could be applied.…”