Satellite (LEASAT) (figure 2-4). These satellites are in
geosynchronous orbit over the continental United
States and the Atlantic, Pacific, and Indian oceans.
Each satellite is described in the following paragraphs.
GAPFILLER
In 1976, three satellites, called MARISAT, were
placed into orbit over the Atlantic, Pacific, and Indian
oceans. Each satellite had three UHF channels for
military use, one wideband 500-kHz channel, and two
narrowband 25-kHz channels.
The Navy leased the UHF section of each satellite
for communications purposes. To distinguish the
special management and control functions for
communications on these UHF channels, the Navy gave
the name GAPFILLER to the leased satellite assets.
GAPFILLER was intended to fill the need for a
continuing satellite communications capability in
support of naval tactical operations until the Navy
achieved a fully operable Fleet Satellite
Communications (FLTSATCOM) system.
The GAPFILLER satellite over the Indian Ocean is
the only one still being used by the U.S. Navy. The other
two GAPFILLER satellites were replaced by LEASAT.
The active GAPFILLER satellite will also be replaced
by LEASAT as it reaches the end of its operational life.
Within the 500-kHz band, transponders provide 20
individual 25-kHz low- and high-data-rate
communications channels for 75 baud ship-shore
Figure 2-4.—GAPFILLER, FLTSATCOM, and LEASAT satellites.
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