Page 65 - Communications Satellites Global Change Agents

2. EVOLUTION OF SATELLITE TECHNOLOGY 41

The launch of these experimental spacecraft was accomplished in two stages.
The first stage positioned the satellite into a highly elliptical cigar-shaped orbit
with the apogee (or high point of the orbit) some 22,230 miles (35,870 kilometers)
into space and the perigee (or lowest point of the orbit) only a few hundred miles
above the earth's surface. Second, after this highly elliptical transfer orbit was es-
tablished, an apogee kick motor was fired near the apogee of the elliptical orbit at
exactly the right moment, and this served to transfer the satellite into its circular
GEO orbit. This GEO orbit represents a perfect circle 22,230 miles distant from
earth—almost a tenth of the way to the moon. This is some 40 times farther away
from the earth than so-called low earth orbit satellites (LEOs), which are posi-
tioned below the Van Allen radiation belts and some four times farther away from
the earth than so-called medium earth orbit (MEOs), which are positioned above
the Van Allen belts. The relative positioning of GEO, MEO, and LEO satellites
are represented (but not to full scale) in Figs. 2.2 and 2.3.
The Syncom 2 and Syncom 3 satellites were the first practical demonstrations
of how to launch and operate GEO satellites. They also demonstrated that a rather

FIG. 2.2. Graphics showing the relative positioning of LEO and GEO satellite or-
bits above the earth.

FIG. 2.3. Relative orbital positions of LEO, MEO, and GEO satellites (not to
scale).