WAAS PRN 135 Satellite Ceases Broadcast

WAAS PRN 135 Satellite Ceases Broadcast

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December 17, 2010

The Federal Aviation Administration announced that the Wide Area
Augmentation System (WAAS) Intelsat CRW geostationary (GEO) satellite
PRN 135 has ceased broadcasting the WAAS signal as of December 16, 2010.
The deterioration of the satellite’s ability to remain stable over the
past few days caused intermittent data link disruptions that rendered
the satellite unreliable for further data transmissions. The FAA’s
mitigation plan to activate another satellite in November 2010 was
successful and the new GEO satellite, Inmarsat AMR (PRN 133), has been
transmitting the WAAS signal in addition to the Telesat CRE GEO.

According to the announcement, sixteen airports north of a line from
70N150W and 64N164W in northwest Alaska are affected by the failure.
Only one of the 16 airports located in the affected area has published
LPV approaches, and that airport is NOTAMed out for any WAAS procedures.
Users of these 16 airports will continue to fly the existing lateral
navigation (LNAV) procedures and are required to confirm that GPS
receiver autonomous integrity monitoring (RAIM) will be available for
all flights during planning. Please refer to Anchorage Center NOTAMS for
specific guidance.

The WAAS broadcast over a large portion of the rest of Alaska will now
be provided by a single GEO. WAAS users in this area may experience
temporary service outages due to lack of redundant GEO signals. These
outages will occur during a switch between the primary and backup GEO
Uplink System (GUS) stations. These switchovers will occur approximately
4 – 5 times a month and it may take up to 5 minutes to fully restore LPV
service after an occurrence.