Page 32 - Satellite Communications, Fourth Edition

12 Chapter One

Figure 1.5 Components of a direct broadcasting satellite system. (From Government of
Canada, 1983, with permission.)

Table 1.5 shows the orbital assignments for domestic fixed satellites
for the United States (FCC, 1996). These satellites are in geostationary
orbit, which is discussed further in Chap. 3. Table 1.6 shows the U.S.
Ka-band assignments. Broadband services, such as Internet (see Chap.
15), can operate at Ka-band frequencies. In 1983, the U.S. FCC adopted
a policy objective, setting 2° as the minimum orbital spacing for satel-
lites operating in the 6/4-GHz band and 1.5° for those operating in the
14/12-GHz band (FCC, 1983). It is clear that interference between satel-
lite circuits is likely to increase as satellites are positioned closer
together. These spacings represent the minimum presently achievable
in each band at acceptable interference levels. In fact, it seems likely that
in some cases home satellite receivers in the 6/4-GHz band may be sub-
ject to excessive interference where 2° spacing is employed.

1.5 Polar Orbiting Satellites
Polar orbiting satellites orbit the earth in such a way as to cover the
north and south polar regions. (Note that the term polar orbiting does
not mean that the satellite orbits around one or the other of the poles).