Page 52 - Satellite Communications, Fourth Edition
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32 Chapter Two
From Kepler’s third law:
14 1/3
a c 3.986005 10 d
5 2
(7.272 10 )
42,241 km
Since the orbit is circular the semimajor axis is also the radius.
2.5 Definitions of Terms for Earth-Orbiting
Satellites
As mentioned previously, Kepler’s laws apply in general to satellite
motion around a primary body. For the particular case of earth-orbiting
satellites, certain terms are used to describe the position of the orbit
with respect to the earth.
Subsatellite path. This is the path traced out on the earth’s surface
directly below the satellite.
Apogee. The point farthest from earth. Apogee height is shown as h a
in Fig. 2.3.
Perigee. The point of closest approach to earth. The perigee height
is shown as h in Fig. 2.3.
p
Figure 2.3 Apogee height h a ,
perigee height h p , and inclination i.
l a is the line of apsides.
