WAAS Broadcasting Satellite Having Problems

April 12, 2010 By: Eric Gakstatter

Intelsat S.A. announced they lost control of their Galaxy 15 (G-15) satellite. G-15 (PRN 135 to GPS users) is one of the two Wide Area Augmentation System (WAAS) broadcasting satellites (GEOs) that broadcast GPS corrections for aviation and ground users all over North America. Despite the Intelsat announcement, the WAAS payload on G-15 is still broadcasting corrections.

WAAS GEOs are a critical part of the WAAS infrastructure that provides GPS corrections to aviation and ground users all over North America. Although the system can operate with one WAAS GEO in service, the second provides dual coverage and increased visibility to the WAAS service area. After data is compiled and optimized from 38 GPS reference stations throughout North America, the two WAAS GEOs are used to broadcast the GPS corrections to all users in North America.

It's being speculated that the FAA might utilize another Inmarsat satellite in place of Galaxy 15, but no announcement has been made. Furthermore, the FAA has not issued any NOTAMs (Notice to Airmen) regarding a change in WAAS.

Aside from this event, the Federal Aviation Administration (FAA) has already begun testing a new WAAS geo satellite (Inmarsat 4-F3 at 98°W) scheduled to be brought into service late this year or early next.

According to the Intelsat announcement, there has been no immediate service interruption to customers, and based on current technical information, no service interruption is expected for the media customers on this satellite. All media traffic on this satellite is planned to be transitioned to Intelsat’s Galaxy 12 satellite, which is the designated in-orbit spare for the North American region. Galaxy 12 is currently relocating to the 133° W orbital location. Intelsat’s global fleet, the largest of any commercial satellite operator, includes 12 other satellites that serve the continental U.S. region. Galaxy 12 does not have the payload (L-band) necessary to broadcast WAAS corrections.

Intesat stated that G-15 was launched in 2005 and is an Orbital Star satellite. Intelsat and Orbital Sciences Corporation, the manufacturer of G-15, are conducting a technical investigation with respect to the anomaly, which has had no impact on the communications services delivered by the spacecraft. Galaxy 15 has 24 C-band transponders and was designed to be operational through 2022.

Intelsat's Galaxy 15 (PanAmSat) 133°W is experience communications problems

GPS World is hosting a webinar that will discuss this issue further as well as the status of GPS and GLONASS constellations. Sign up for the free webinar by clicking here.