ARLA/CLUSTER: Problemas com o sistema de posicionamente global russo GLONASS

[João Costa > CT1FBF]

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.

During the outage, one U.S.-based GNSS high-precision manufacturer reported
“We are currently experiencing calls from customers all over the world who
are experiencing GLONASS “outages� and we have advised customers to switch
GLONASS tracking off on our receivers. We don’t have any better information
on when normal service is likely to resume from GLONASS satellites. If you
do, let me know!�

Such a — possibly human, possibly computer-generated — error could
conceivably occur with GPS, Galileo, or BeiDou. “Another reason to have
backups,� mused Richard Langley of the University of New Brunswick. “And
not just other GNSS.�

Full story at:
http://gpsworld.com/glonass-gone-then-back/

Our thanks to *Stephen, G7VFY* for spotting this item
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