New WAAS satellite launched

5 Flight VA253 was launched from the Guiana Space Centre, Kourou, at 2204 UTC on 15 August. The heaviest ever Ariane launcher carried 3 satellites: BSAT-4a for direct-to-home television broadcasting over Japan; MEV-2, a satellite servicing vehicle designed to dock with satellites in orbit; and Intelsat’s Galaxy 30 UHD video distribution/broadcast and broadband satellite, including WAAS, to cover North America.

The 3-satellite payload was placed in a geostationary transfer orbit (GTO) and ultimately the 2 comms satellites will be positioned in geosynchronous equatorial orbits (GEO). Galaxy 30, carrying the WAAS equipment, will be placed at 125ºW longitude – supplementing 2 other GEOs.

The WAAS satellite-based augmentation system (SBAS) is compatible with the European Geostationary Navigation Overlay Service (EGNOS), Indian GPS Aided Geo Augmented Navigation (GAGAN) and the Japanese Multi-functional Satellite Augmentation System (MSAS). All use a network of ground-based reference stations to determine real-time GPS errors, which are sent to master stations which relay correction messages via the SBAS satellites. The corrections are transmitted to receivers via GPS frequency and format.

The FAA WAAS accuracy requirements (95%) for an aircraft instrument runway approach down to 200 ft – Localizer Performance with Vertical guidance (LPV-200) – is 16m horizontal and 4 m vertical; actual performance has been 0.7m horizontal and 1.2m vertical.

https://www.faa.gov