some of the various earth terminals and how they
interface. The end use or purpose determines the
systems complexity and how the system is used.
ROLE OF SATELLITE
SATCOM links, one of several kinds of long-
distance communications links, interconnect com-
munications centers located strategically throughout
the world. These SATCOM links are part of the
Defense Satellite Communications System (DSCS)
and Fleet Satellite Communications.
Satellite communications systems are very
important to the worldwide military com-
munications network for two primary reasons. First,
they continue to operate under conditions that cause
problems for other methods of communication.
Second, they provide reliable and secure com-
munications to previously inaccessible areas. In
many cases, these communications requirements
can o n ly be satisfied by sophisticated satellite
communications systems. By satisfying such needs,
SATCOM makes a significant contribution to the
improved reliability of naval communications.
ADVANTAGES OF SATELLITE
Some of the unique advantages SATCOM has over
conventional long-distance communications are as
SATCOM links are unaffected by the
propagation problems associated with hf radio
SATCOM links are free from the high-
attenuation problems of facilities that use wire
or cable for routing communications.
SATCOM links span long distances.
The numerous repeater stations required for
line-of-sight and troposcatter systems are not
As you can see, satellite links provide the required
flexibility and reliability needed to support military
operations. In the following paragraphs, we will look
at SATCOM capacity, reliability, vulnerability,
flexibility, and limitations.
Currently, military SATCOM systems can provide
communications between backpack, shore, airborne,
and shipboard terminals. These SATCOM systems can
handle thousands of communications channels at the
SATCOM frequencies are only slightly affected
by atmospheric phenomena and do not depend on
reflection or refraction. Reliability is based on the skill
of operators and maintenance personnel and the
condition of the satellite communications equipment.
Communications satellites are relatively safe from
threats of harm. Because these satellites are in such
high orbits, any attempt to disable or destroy them
from the Earth would be difficult and expensive.
However, Earth terminals are a different story. They
offer a more attractive target for destruction by
conventional methods. But these terminals can be
protected by the same methods taken to protect other
vital installations. So overall, the satellite system is
nearly free from harm by an enemy.
Operationally, highly directional earth terminal
antennas provide a high degree of freedom from
jamming. The wideband system can use antijamming
techniques, which also reduces vulnerability.
Mobile military satellite earth terminals with
trained crews can be deployed and put into operation
anywhere in the world within hours.
The technical characteristics of the satellite and its
orbital parameters are the main limitations to a satellite
communications system. Two additional limiting
factors for active satellites are transmitter power and
receiver sensitivity. Energy for electricity is limited to
whatever can be produced by the solar cells, which
limits the satellites output power. This problem is
made worse by users who increase their output power
to the satellite, causing the satellite to try to retransmit
at the new power level, at the expense of reducing
signals to other users.