Altus Positioning Systems Pinpoints Cause for GLONASS Default

April 4, 2014 - By Alan Cameron

Image: GPS World

Regarding the April 1–2 11-hour downtime for the full GLONASS constellation, president and CEO Neil Vancans of Altus Positioning Systems provides this additional information:

“From the reports on GLONASS problems, we have an explanation that may be used in our technical support replies:

“Our analysis reveals the GLONASS integration algorithms skipped an interval of around 1.5 minutes at the control centre software.

“At 21:00 UTC April 1, all GLONASS satellites received an orbit state (ephemeris) which was clearly several minutes ahead of the current orbit shape without actually changing the applicable reference time stamp. In other words, future orbit-position, velocity and accelerations were assigned to a current reference timestamp.

“This led to incorrect orbit positions for all GLONASS satellites and subsequent problems with receiver using GLONASS measurements.

“In our receivers, RAIM rejected the solutions because of the large GLONASS errors, and could only work with GPS only and the recently revised RAIM settings for a Base (SRL,ON,-6,-4,-4).

“The issue is now rectified, and the GLONASS constellation is back to normal.”