Wayward Satellite Will Affect WAAS Coverage
April 22, 2010 — Intelsat is having trouble controlling its Galaxy XV satellite and has notified the FAA that it will stop broadcasting Wide Area Augmentation System (WAAS) signals in the next few weeks. The Intelsat Galaxy XV is one of the geostationary satellites (GEO) that broadcasts the WAAS signal in space. For WAAS users, there is no immediate impact to service; but over the next few weeks, the Intelsat GEO will drift out of its current orbit position, ultimately requiring the GEO broadcast to be discontinued.
After the Intelsat GEO service is discontinued, WAAS users outside the affected area of Northwstern Alaska may experience temporary service outages due to lack of redundant GEO signals, if a switch between the primary and backup GEO uplink stations (GUS) occurs. Although these switchovers are rare events, it may take up to five minutes to fully restore LPV service after an occurrence.
A replacement satellite is scheduled to launch into orbit later this year; however the FAA is looking for other options to limit the impact of the WAAS outage.
There are 16 airports affected by the failure in Northwest Alaska. None of the airports located in the affected area have published LPV approaches, so users will continue to fly the existing LNAV procedures. However, users are required to confirm that GPS receiver autonomous integrity monitoring (RAIM) with fault detection and exclusion (FDE) will be available for the flight during planning.
Operators using TSO-C145/C146 receivers for en route or terminal or approach IFR operations are required to confirm GPS RAIM availability. Due to reduced WAAS availability, any required alternate airport must have an approved instrument approach procedure other than GPS that is anticipated to be operational and available at the estimated time of arrival and which the aircraft is equipped to fly.
For more information, please see the "WAAS Intelsat GEO Outage Impacts" briefing.