Differential GPS - Understanding GPS: Principles and Applications - page 443

INMARSAT 3
POR
178°E

INMARSAT 3
AOR/W
54°W

Figure 8.33 Current WAAS space segment and primary service area.

PanAmSat
133°W

Telesat
107°W

Figure 8.34 Location of additional WAAS GEOs.

The current EGNOS space segment is composed of three GEO navigation tran-
sponders payload hosts, Inmarsat-3 AORE and IOR, and the ESA ARTEMIS navi-
gation satellite, as shown in Figure 8.35. EGNOS will likely use one or more of the
Inmarsat 4 GEOs that will be launched into orbit around 2005. The Inmarsat 4s
will host a navigation payload capable of transmitting SBAS information on both
the GPS L1 and L5 frequencies [56]. A functional schematic of the Inmarsat-4 satel-
lite is shown in Figure 8.36.
As mentioned earlier in this section, the first GEO planned for MSAS,
MTSAT-1, was destroyed following a launch failure in 1999. A replacement,
MTSAT-1R, was launched in February 2005 and is located at 140ºE. A second