Timekeeping - a bit of an owie for the Russians

We have our GPS system. The Russians have their Glonass system -- similar technologies, similar frequencies. Seems like they had a bit of a PEBKAC error yesterday - from GPS World:

GLONASS Gone . . . Then Back
In an unprecedented total disruption of a fully operational GNSS constellation, all satellites in the Russian GLONASS broadcast corrupt information for 11 hours, from just past midnight until noon Russian time (UTC+4), on April 2 (or 5 p.m. on April 1 to 4 a.m. April 2, U.S. Eastern time). This rendered the system completely unusable to all worldwide GLONASS receivers. Full and correct service has now been restored.

�Bad ephemerides were uploaded to satellites. Those bad ephemerides became active at 1:00 am Moscow time,� reported one knowledgeable source. For every GNSS in orbit, the navigation messages include ephemeris data, used to calculate the position of each satellite in orbit, and information about the time and status of the entire satellite constellation (almanac); this data is processed by user receivers on the ground to compute their precise position.

According to another source, a GLONASS fix could not take effect until each satellite in turn passed back over control stations in the Northern Hemisphere to be reset, thus taking nearly 12 hours.

These satellites are in relatively low earth orbit and the physics of their task changes with the changes in gravitational pull, atmospheric tides, gravitational pull from the moon and another five or six factors. The correction data is calculated and uploaded to each satellite as it passes over a control station. Classic case of GIGO - Garbage In / Garbage Out. Happens to the best...