This appendix gives a summary of space support to air and missile defense operations. It is not intended as a comprehensive guide. FM 100-18 establishes doctrine for the Army's use of space, describes current space system capabilities, and provides guidance for the use and application of space-based assets in support of Army operations.
C-3. The time it takes to complete one complete revolution of the earth is known as the orbital period. The period relates directly to the orbit's average distance from earth and is a function of the satellite's velocity. The greater the velocity imparted to the satellite during orbital insertion, the greater the orbital period and average distance from earth. Orbital periods range from 90 minutes for the lowest orbits to 24 hours or more for deep space orbits.
C-4. Another element of a satellite's orbit is its inclination, which is the angle at which the satellite's orbital plane crosses the equator. A higher inclination generally means that more of the earth's surface is covered. A polar orbit, with an inclination of 90 degrees, crosses all latitudes, while lesser or greater inclinations only provide coverage for increasingly higher latitudes, particularly for satellites in low earth orbits.
C-5. The length of time between satellite coverage of a particular earth location, that is, the satellite's revisit time, depends upon a number of factors. For any given satellite, revisit time depends upon both orbital period and inclination. For earth coverage by like systems, revisit time also depends upon the number of satellites in the constellation, the capabilities of the satellites' payloads, and the footprints of the various onboard sensors.
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.
C-15. Each DSCS III satellite has six transponders providing six channels through earth coverage antennas, narrow beam antennas, and multi-beam antennas. The DSCS satellites provide worldwide coverage from 70 degrees north to 70 degrees south latitude. Additional DSCS III satellites are available for launch.
C-16. Operational command of DSCS is provided by the US Space Command. Management of user traffic and network configuration is a function of the Defense Information Systems Command. Payload control on DSCS III satellites is accomplished through DSCS operation centers (DSCSOC). The Army Space Command operates all five of the DSCSOC. Platform control of DSCS III satellites and both payload and platform control of DSCS II satellites is provided by the Air Force Space Command. Users include the Defense Information Systems Agency that supports many government agencies, US Air Force, US Navy, US Marine Corps, and US Army. DSCS supports the Worldwide Military Command and Control System, the Defense Data Network, and the Defense Switched Network. Channel capacity is allocated to the unified and specified CINCs by the JCS through coordination with regional space support centers. The CINCs further allocate their channels within their command.
C-17. DSCS supports tactical communications through the Ground Mobile Forces Satellite Communications (GMFSC) program. The GMFSC program provides critical communications support for critical command, control, communications, computer, and intelligence requirements. The Army has about 200 GMFSC terminals. These terminals connect other Army communications systems, such as mobile subscriber equipment, to provide connectivity between the dispersed units and to deployment and support bases in CONUS and other theaters.
C-19. The Army tactical exploitation of national capabilities program (TENCAP) provides Army commands with equipment that can receive and process data provided by the national space systems. Initially, ground terminals were developed for use at corps and higher headquarters. The evolution of the TENCAP systems has made it feasible to deploy certain systems to echelons below corps also. The request and dissemination process, system capabilities, and specific applications can be found in the Joint Tactical Exploitation of National Capabilities (J-TENS) manual.
C-24. Multispectral imagery (MSI) from space has proven invaluable for mapping, geology, agriculture, earth resources, oceanography, and environmental monitoring. The information available through multispectral imagery can be obtained by a satellite in about 25 seconds or through a ground survey taking months, many people, at great expense, and often without the same amount of detail. Many areas cannot be easily surveyed from the ground or by aircraft because they are too heavily congested, too remote, or access is restricted for military or political reasons. There are seven satellite systems collecting MSI. Each provides data with a unique combination of bands, resolution, and times of coverage.
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 two-dimensional 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.
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-31. TERS will transition into the Tactical Event System (TES) in the near future. TES will use the same communications architecture currently used by TERS, but will provide more timely and more reliable missile launch warning. TES warning messages will originate at different ground segments which each contribute different but complementary detection and processing capabilities. The components of TES are the Attack and Launch Early Reporting to Theater (ALERT) system, the Tactical Detection and Reporting (TACDAR) system, and the Joint Tactical Ground Station (JTAGS).
C-32. JTAGS is a satellite receiver that allows direct downlinks of missile and other warning data into the theater. Data is processed and disseminated in theater via the TRAP and TIBS networks. JTAGS will also disseminate voice warning to forces in the theater. Within 2 minutes of missile launch, tactical parameters, to include estimated impact area, are available to support tactical missile defense operations. USSPACECOM executes its control of JTAGS through the Army Space Command (ARSPACE).
C-34. As NASA and the newly created United States Air Force assumed greater responsibility for civilian and military space operations, the Army's role in space declined proportionately. The Army's space interests were limited to development of air and strategic ballistic missile defense capabilities, and to exploitation of national space capabilities for support of tactical operations.
C-35. In 1973, the Army Space Program Office (ASPO) was established to improve support by national capabilities to tactical commanders. The Joint Tactical Exploitation of National Capabilities Program has fielded a number of systems for use by Army commanders. The Strategic Defense Command (SDC) has led Army efforts to develop defenses against both strategic and tactical ballistic missiles.
C-36. In 1985, DOD established the United States Space Command (USSPACECOM) to exercise combatant command over the service's space operations. The Commander in Chief, USSPACECOM, provides space support to other theater commanders as a supporting CINC. The Army's Space and Strategic Defense Command (SSDC) consists of ARSPACE and SDC and is the Army component of USSPACECOM. ARSPACE is the Army operational component of USSPACECOM, and SDC continues as the lead agency for missile defense systems development.
C-37. The development of the Army's Air-Land Battle Doctrine in the 1980s focused on a battlefield that was expanding in time, depth, and lethality. Space offers the Army unique and enhanced capabilities to achieve land dominance. Space systems provide communications, positioning and navigation data, early warning, weather, environmental, and ISR capabilities that are essential for the successful prosecution of land warfare. FM 100-5 incorporates space support to Army operations. Under this evolving doctrine, space systems are fully exploited to enhance execution of the Army's mission during all phases of force-projection operations.
C-38. In the past, space assets were used for support of echelons above corps only. Today, as a result of programs initiated by USSPACECOM, SSDC, and the ASPO, every soldier on the battlefield exploits space capabilities. Units involved in counterair operations benefit from the entire suite of national space systems. In addition to intelligence, weather, and terrain support, Army ADA units use space-based communications and early warning of missile attack to significantly enhance air and missile defense operations.