fm 44-100 us army air and missile defense operations

FM 44-100
C-2
C-6. One type orbit that is particularly useful for wide area-continuous
observation has a period of 24 hours and an inclination of 0 degrees. In this
orbit, which is referred to as geosynchronous, a satellite orbits the earth
around the equator at the same rate that the earth rotates below the
satellite. While the satellite orbits at very high speed at an altitude of 22,500
miles, it appears to remain stationary over the same point on the earth's
surface. Satellites in geosynchronous orbit provide continuous observation of
most of a global hemisphere.
SPACE SYSTEM LIMITATIONS
C-7. While satellites can provide the Army many valuable capabilities,
planners and users must understand some of their general limitations.
Though not all-inclusive, the following limitations represent areas that must
be considered when planning and requesting space support.
Access
Vulnerability
Utility
C-8. Satellites, and the launch operations which support them, are extremely
expensive and manpower intensive. For these reasons, military satellites are
national resources, supporting the NCA, CINCs, other services and
government agencies, and other tactical users. As a result, requirements can
frequently exceed capacity and the system's capabilities. A validation process
to determine what requirements will be satisfied is based upon priority and
system availability. The NCA, through the JCS, allocates satellite resources
to the joint force commander who allocates those resources to users within
the theater according to the JFC's priorities.
C-9. Satellite systems are vulnerable to environmental conditions in space
such as temperature extremes, radiation, meteoroids, and space debris.
Atmospheric disturbances and solar activity such as solar flares also can
affect satellite systems. Clouds, fog, and smoke affect the ability of imaging
systems to see, and rain may degrade some radio signal frequencies. Solar
flare and glare can blank out areas of the earth's surface from infrared
observation for hours each day during the vernal and autumnal equinox
period. Since blanked out areas differ for satellites in different orbits,
redundant coverage of crisis areas by two or more satellites mitigates the
effects of solar flare and glare and ensures continuous coverage of the entire
theater.
C-10. Operationally, the Army is dependent upon systems currently on orbit,
although these systems may or may not be suited to a particular Army
mission. Satellites do not provide continual coverage; for example, LANDSAT
sensors revisit a point on the earth approximately every 16 to 18 days.
Moving a satellite to a more advantageous orbit or position takes time and is
limited to the amount of fuel on board since satellites cannot be refueled. As
satellites age, components become degraded or fail, decreasing the satellite's
utility and reliability. Satellites in geosynchronous orbit have poor viewing
geometry towards the edge of their coverage along the limb of the earth.