fm 44-100 us army air and missile defense operations

FM 44-100
POSITION AND NAVIGATION
C-27. The Global Positioning System (GPS) is a satellite-based system
developed by DOD to provide continuous, all weather, global position,
navigation, velocity, and precision time information. GPS consists of 24
operational satellites in 20,260 kilometers (10,950 nautical miles) altitude,
semi-synchronous, circular orbits, evenly spaced in 6 orbital planes. A
minimum of 5 satellites is always within view of any ground user, thus
providing continuous three-dimensional capability. Satellite life expectancy is
6 to 7 years each. Replacement satellites will be launched to maintain the
constellation of 24 GPS satellites.
C-28. Satellite control is performed by the US Air Force Space Command
assisted by Army personnel assigned to US Army Space Command. All US
military services along with some allied military services, and certain other
designated users have access to Precise Positioning Service (PPS), if equipped
with terminals capable of loading a COMSEC code. GPS receivers provide a
degree of accuracy for position determination, navigation, velocity, and time
synchronization never before possible. GPS receivers are passive, therefore,
they cannot be detected by electronic means and there can be an unlimited
number of users. Signals from three GPS satellites are required for twodimensional
position determination (user provides altitude). Signals from 4
satellites are required for three-dimensional position determination (no user
input required). PPS provides three-dimensional positioning accuracy of 16
meters spherical error probable (SEP) and two-dimensional position accuracy
of 10 meters circular error probable (CEP). Depending on the type of receiver
used, the time accuracy can be as good as 48 nanoseconds. Velocity accuracy
is 0.2 meters per second.
MISSILE WARNING
C-29. The Defense Support Program (DSP) was initiated as a space-based
strategic surveillance system to detect the launch of ICBM and SLBM. Its
utility has expanded to support theater missile defense operations. DSP
satellites are located in geosynchronous orbits to provide continuous coverage
over the eastern and western hemispheres. DSP satellites can detect the
launch of ICBM, SLBM, SRBM, satellite booster rockets, and certain other
rockets. USSPACECOM exercises authority over DSP through the Air Force
Space Command that operates and controls the satellites. Data is centrally
processed and transmitted to users. The principal users are the National
Command Authority, United States Space Command, Strategic Command,
North American Aerospace Defense Command (NORAD), and unified and
specified CINCs.
C-30. The Tactical Event Reporting System (TERS) is a worldwide
distribution system currently made up of the Tactical Receive Equipment and
Related Applications (TRAP) system, the Tactical Information Broadcast
System (TIBS), and the Joint Operation Tactical System (JOTS). Within two
to four minutes of launch, the theater commander is provided tactical missile
launch warning data, including the place of launch, time of launch, type
missile, and a course azimuth. This warning information can be used to alert
friendly forces (defensive weapon systems such as air and missile defense
systems) and attack systems.
C-7