Doctrine NTP 2 NAVAL TELECOMMUNICATIONS PROCEDURES
NAVY SUPER HIGH FREQUENCY SATELLITE COMMUNICATIONS




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CHAPTER 2
SYSTEM DESCRIPTION

201. GENERAL The Navy SHF SATCOM systems operating in the X-band provide communications links, via SHF satellites, between designated mobile units and DSCS shore sites. These links provide worldwide coverage with a high-capacity, full-duplex communications capability. The systems necessary to support Navy SHF SATCOM can be described in terms of space, terminal, and control segments. The space and terminal segments are described in this chapter. The control segment is described in chapter 3. For convenience, this chapter addresses system description in three parts:

Part 1 -Space Segment (paragraphs 202 through 204)
Part 2 -Earth Segment (paragraphs 205 through 209)
Part 3 -Baseband Systems (paragraphs 210 through 211)

PART 1 SPACE SEGMENT

202. BACKGROUND The space segment of the Navy SHF SATCOM system consists of the DOD DSCS satellite constellation and may use assets of the North Atlantic Treaty Organization (NATO) and allied satellite constellations. The DOD SHF SATCOM system was implemented in phases and is an ongoing program which is operated, maintained, and controlled as a subsystem of the Defense Communications System. DSCS I satellites (Phase I) and DSCS II satellites (Phase II), which are no longer in use, provided SATCOM capability from 1967 to 1993. DSCS III satellites (Phase III), which are now used exclusively, were first placed in operation in 1983; nine are currently active (five primary and four reserve), and five are in inventory. Future DSCS III launches are tentatively scheduled for 1997 (B-13), 1999 (B-8), 2000 (B-11), 2002 (B-6), and 2003 (A-3). DSCS III satellites, designed to provide SHF SATCOM capability through the year 2000 and beyond, are being placed in geosynchronous orbital positions 22,300 miles above the equator to provide coverage between 75 o north latitude and 75 o south latitude. The DSCS constellation provides communications services in each of the following five satellite areas: East Pacific (EPAC), West Atlantic (WLANT), East Atlantic (ELANT), Indian Ocean (IO), and West Pacific (WPAC). Figure 2-1 illustrates the DSCS III satellite footprint.

203. DSCS PHASE III A. Description. There are two series of DSCS III satellites: A-series and B-series. The A-series are the first-generation DSCS III satellites. The B-series are newer and have received upgrades to various support subsystems and the communications subsystem (Note: Model A-3 awaiting launch will be upgraded and have the same capabilities as a B-series model). The essential difference between 19



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Figure 2-1
DSCS III Footprint

the A-series and B-series DCSC III satellites is in the single channel transponder (SCT) package. The A-series DSCS/ SCT has only the UHF downlink capability while the B-series DSCS/ SCT has both UHF and SHF downlink capability. Thus, when the Navy is operating over DSCS III B-series channel one, the regular communications channel will have to share the channel one traveling wave tube (TWT) power amplifier with the SCT community; however there is no power sharing required with the SCT community over the DSCS III A-series satellites. A thorough description of the communications subsystem appears below. Table 2-1 lists the specific operational satellite model supporting each geographical area. The DSCS III satellites are designed for an operational life span of 10 years. Figure 2-2 illustrates the components of an on-orbit DSCS III satellite.

B. DSCS III Satellite Capability. The DSCS III satellites provide substantial capability to support high-capacity links between all terminals and to permit AJ communications and control of the satellites during crisis and contingency situations. DSCS III satellites operate in the X-band region, providing uplink services in the 7900-8400 MHz band and downlink services in the 7250-7750 MHz band. The frequency spectrum is divided into six bands by the use of six limited-bandwidth transponders which are switchable between antennas by DSCS ground control. Communications performance is optimized by allowing these independent transponders to be connected to various types of antennas. This permits selection of Earth coverage (EC), area coverage (AC), spot coverage, grouping of channels with similar modulation, and antenna gain-to-noise temperature (G/ T) ratios to meet user needs. Any type of modulation or multiple access may be used since the transponders do not 20



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SATELLITE
OCEAN AREA
DSCS III
SATELLITE
MODEL
LONGITUDE
(Degrees)
East Pacific Primary B-14 135W
East Pacific Reserve A-1 130W
West Atlantic Primary B-7 52.5W
West Atlantic Reserve B-4 42.5W
East Atlantic Primary B-12 12W
Indian Ocean Primary B-10 60E
Indian Ocean Reserve A-2 57E
West Pacific Primary B-9 175E
West Pacific Reserve B-5 180E

Current DSCS Satellite Constellation
Table 2-1

Figure 2-2
DSCS III On-Orbit Satellite

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process or modulate the signals. The DSCS III satellites are three-axis stabilized (geostationary) vehicles that have a dry weight of 1,950 pounds and a maximum weight of 2,550 pounds with propellant. The dimensions of the satellite body are approximately 80 inches (6.5 feet) on each side and 460 inches (38 feet) in length, with solar arrays (SA) deployed. Communications antennas include a receive 61-beam multibeam antenna (MBA) and two transmit 19-beam MBAs, two receive and two transmit Earth coverage horns (ECH), and a transmit-only gimballed dish antenna (GDA). In addition, there is one transmit and one receive SCT UHF antenna. The DSCS III satellite's general characteristics are listed in table 2-2.

SATELLITE CHARACTERISTICS DSCS III DSCS III SLEP
Effective Isotropic Radiated Power (EIRP) EC Beacon, 27 dBW
NC Beacon, 40 dBW
EC Beacon, (TBD)
NC Beacon, (TBD)
Power Output 40-watt RF, Channels 1 and 2
10-watt RF, Channels 3 through 6
50-watt RF, Channels 1 through 6
EC Beacon 1 Frequency 7600 MHz 7600.000000 MHz
EC Beacon 2 Frequency 7604 MHz 7604.705882 MHz
Beacon EIRP 13 dBW TBD
Satellite Weight 1,950 pounds
(2,550 pounds with propellant)
TBD
Size Main structure:
Length: 9.2 feet with panels
Width: 6.3 feet
Depth: 6.4 feet (no antenna tips)

Solar array:
With Yoke: 15.9 feet

Fully Extended: 38.1 feet
Main structure:
Length: 9.2 feet with panels
Width: 6.3 feet
Depth: 6.4 feet (no antenna tips)

Solar array:
With Yoke: 15.9 feet

Fully Extended: 38.1 feet

Lifetime 10 Years 10 Years

DSCS III Satellite Characteristics Table 2-2

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C. DSCS III Supporting Subsystems. The principal supporting subsystems of the DSCS III satellites are listed in table 2-3. A brief description of each of the major support subsystems, including the SCT Subsystem, is provided in the following paragraphs.
SUBSYSTEM KEY FEATURES
Attitude Control Autonomous initial sun acquisition and operation
Earth and sun sensors for attitude sensing
Four skewed reaction wheels
Time-shared central digital processor for all control modes
0.08 o roll, 0.08 o pitch, 0.8 o yaw control accuracy
Propulsion Hydrazine propulsion system with redundant thrusters and tanks
600 pound capacity beginning of life (BOL)
1.0 pound thruster
Telemetry, Tracking and Command (TT& C) Command and telemetry interface with Satellite Control Facility, DSCS terminals, and the shuttle
Rapid MBA reconfiguration
Incorporation of SHF communications security (COMSEC) equipment
Electrical Power and Distribution Regulated Bus -28V dc 1%
126 square feet of solar array
96 Ah NiCd battery capacity
1188 watt output from solar array at BOL
Fully redundant
Rapid response to load changes
Load fault isolation/ transient protection
Thermal Control Passive during normal operation
North/ South radiator panels use optical solar reflectors
Survive failure modes include attitude loss and total battery failure
Structures and Mechanism Provides accessibility and modularity
North/ South array through drive shaft
Independent propulsion module
Vibration damped equipment panels
Lightweight, stiff, and dimensionally stable Growth and option flexibility
Single Channel Transponder (SCT) Separate dedicated UHF transmit and receive antennas
Integral UHF/ SHF transponder assembly
Supports UHF/ SHF uplink, single UHF downlink channel
SHF downlink available on B-series satellites (requires utilization of percentage of channel 1 traveling wave tube amplifier [TWTA])
DSCS III Subsystems Table 2-3 23



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1. Attitude Control Subsystem (ACS). The ACS is a three-axis, zero momentum stabilization system using on-board electronic processing to provide attitude control. The ACS orients and stabilizes the satellite after launch vehicle separation, maintains pointing during on-orbit and payload operations, and controls the satellite attitude during orbit adjustment operations.

2. Propulsion Subsystem (PS). The PS consists of four propellant tanks, two thruster banks (eight thrusters each bank), and six propellant fill and drain valves. Individual thruster banks are capable of performing all mission functions.

3. Telemetry, Tracking and Command (TT& C) Subsystem. The TT& C subsystem provides the capability to command the satellite and transmit TT& C data over redundant control links. The TT& C is a secure (encrypted) telemetry link used primarily for command and control of communications payload operations and on-orbit testing. (Chapter 3 of this NTP provides additional information on DSCS control.)

4. Electrical Power and Distribution Subsystem (EPDS). The EPDS provides for the conversion of solar energy to electrical power and the regulation and distribution of power to the other satellite subsystems. EPDS also provides storage of electrical energy for subsequent use by other subsystems throughout satellite mission life.

5. Thermal Control Subsystem (TCS). The TCS utilizes passive and active temperature control techniques. Passive control techniques include a multilayer insulation blanket (with selective sized cutouts to regulate heat retention) completely enclosing the satellite, thermal coatings, insulation spacers, RF transparent thermal shrouds, thermostats, and flight temperature sensors. During normal operation, only passive TCS techniques are required; however, automatically powered survival heaters actively maintain the minimum survival temperature required.

6. Structures and Mechanisms Subsystem. The major fixed structural assemblies of the DSCS III satellites include a central bay structure, north and south panels, antenna supports, solar array substrates, and a launch vehicle adapter. The main body structure provides hard point mounts for the propulsion system and the communication antennas. The center bay is constructed of aluminum honeycomb panels for mounting components.

7. SCT Subsystem. The SCT subsystem consists of a UHF receive antenna, a UHF transmit antenna, and an integral UHF/ SHF transponder assembly. The SCT subsystem's primary function is to provide secure and reliable dissemination of emergency action messages (EAM) and Single Integrated Operations Plan (SIOP) communications between command post ground stations, aircraft, and theater force elements.

D. DSCS III Communications Subsystem. The major DSCS III Communication Subsystem features are listed in table 2-4. The DSCS III Communications Subsystem includes six independent RF channels, jammer location electronics (JLE), one receive 61-beam MBA, two receive ECHs (E1R and E2R), two transmit 19-beam EC/ narrow coverage (NC) MBAs (M1X and M2X), one transmit GDA, and two transmit ECHs (E1X and E2X). Channels 1 and 2 are designated as high 24



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ITEM KEY FEATURES
DSCS Receive Antennas One 61-beam waveguide lens, MBA
Full 61-beam control of amplitude and phase
Broadband, selective nulling
Accurate, rapid control of selective coverage pattern
Two EC horn antennas
DSCS SHF Transponders Six, one for each channel
High gain for enhanced small terminal operation
Channel 1 bandwidth: 60 MHz (freq. plan I), 50 MHz (freq. plan II)
Channel 2 bandwidth: 60 MHz (freq. plan I), 75 MHz (freq. plan II)
Channel 3 bandwidth: 85 MHz (freq. plan I), 85 MHz (freq. plan II)
Channel 4 bandwidth: 60 MHz (freq. plan I), 85 MHz (freq. plan II)
Channel 5 bandwidth: 60 MHz (freq. plan I), 60 MHz (freq. plan II)
Channel 6 bandwidth: 50 MHz (freq. plan I), 50 MHz (freq. plan II)
Low noise figure (4.0 dB)
Passive thermal design for maximum reliability
Fully hardened components
Low-loss, lightweight filters
Low-phase distortion
DSCS Transmit Antennas Two 19-beam waveguide lens MBAs
Full 19-beam amplitude control
Accurate, rapid selective coverage
Two EC horn antennas
High-gain mechanically steerable parabolic dish antenna connectable to channels 1, 2, or 4; 1 and 4; or 2 and 4

DSCS III Communications Subsystem Key Features
Table 2-4

power channels and each operates with a 40-watt TWTA. Channels 3 to 6, the low power channels, operate with a combination of 10-watt TWTAs/ high efficiency solid-state amplifiers (HESSA), and linear solid-state amplifiers (LSSA) (see paragraph [3] below). The last four DSCS III satellites scheduled for launch (B-8, B-11, B-6, and A-3) will receive performance upgrades through the DSCS SLEP. Responding to the Services' need for more capacity, the original DSCS III SLEP has been revised. The revised SLEP provides improved satellite capability for the next four DSCS satellites to be launched with the first scheduled in July 1999 and the fourth in fiscal year (FY) 2003 (a fifth satellite is currently unfunded). Major revised SLEP upgrades to the DSCS III satellite include increased transponder bandwidth and 50-watt TWTA in all six channels. The 50-watt TWTA and bandwidth addition is predicted to provide a 700 percent increase in tactical communications capacity. 25



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Furthermore, upgrades to the low noise amplifiers (LNA) is estimated to provide an approximately 30 percent increase in data rates for smaller terminals. The increased power capability in all channels on SLEP DSCS III satellites will allow shifting of nontactical users on channels 2 through 4 to channels 5 and 6 by using bandwidth-efficient modulation techniques. This compression technique provides greater bandwidth utilization but, in the past, was not feasible due to the increased power-per-bit requirement. SLEP will increase the mean mission duration (MMD) from 7.5 to 10 years per satellite. The effective isotropic radiated power (EIRP) for various combinations of SHF downlink antennas and transponders for non-SLEP DSCS III satellites is shown in table 2-5. The downlink EIRP for SLEP-modified DSCS III satellites is to be determined. Table 2-6 is being used as a place holder and will be updated at a future date as the data becomes available.

CHANNEL EC HORN GDA MBA (EC) MBA (NC)
1
2
3
4
5
6
-
-
27
27
27
26
46
45.5
-
41
-
-
31
31
25
25
-
-
42
42
36
36
-
-

DSCS III Downlink EIRP (dBW)
Table 2-5

CHANNEL EC HORN GDA MBA (EC) MBA (NC)
1
2
3
4
5
6
-
-
TBD
TBD
TBD
TBD
TBD
TBD
-
TBD
TBD
-
TBD
TBD
TBD
TBD
-
-
TBD
TBD
TBD
TBD
-
-
Downlink EIRP (dBW) of DSCS IIIs with SLEP Upgrade
(Models A-3, B-6, B-8, and B-11)
Table 2-6

The six independent RF channels operate in the SHF band to relay telephone, data, wideband imagery, and secure digital signals. Figure 2-3 shows a typical DSCS III communications subsystem functional block diagram for an individual channel composed of the receive antenna, transponder, frequency standard, frequency generator, and transmit antenna. Figure 2-4 shows the functional relationship of each of the major components that make up the communications subsystem. The communications subsystem operates in the X-band region. The uplink and downlink frequency plan used in the DSCS III satellite Models A-1, A-2, B-4, B-5, and B-7 is illustrated in figure 2-5. Four of the six RF channels have 60-MHz bandwidth. Channel 3 has an 85-MHz 26



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Figure 2-3 DSCS III Communications Channel Block Diagram

Figure 2-4
DSCS III Satellite Block Diagram

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Figure 2-5
Frequency Plan of DSCS III Satellite Models A-1, A-2, B-4, B-5, and B-7

bandwidth, and channel 6 has a 50-MHz bandwidth. The total usable bandwidth is 375 MHz. These six RF channels are arranged with uniform 25-MHz guard bands between them. Each uplink channel frequency is translated down by 725 MHz on the downlink with the exception of channel 6, which is translated by 200 MHz. The newer DSCS III satellites including B-9, B-10, B-12, and B-14 (and Models A-3, B-6, B-8, B-11 and B-13 awaiting launch) provide an improved satellite channelization with a total usable bandwidth of 405 MHz, as depicted in figure 2-6. Under this new frequency plan, the bandwidth of channels 2 and 4 is increased through a reduction in the size of the guard bands and a decrease in the bandwidth of channel 1. Channel 1 has a 50-MHz bandwidth; channel 2 has a 75-MHz bandwidth; and channel 4 has an 85-MHz bandwidth. There is a 15-MHz guard band between channels 1, 2, 3, and 4; and a 25-MHz guard band between channels 4, 5, and 6. Table 2-7 summarizes which DSCS III satellites have implemented the improved channelization scheme.

The communications subsystem partially supports the TT& C subsystem, as well as the SCT subsystem. Communications operations can be conducted simultaneously with TT& C and SCT operations without mutual interference. TT& C commands are received by the satellite through the communications subsystem's receive MBA or receive EC antenna. Two telemetry uplinks are received 28



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Figure 2-6 Frequency Plan of DSCS III Satellite Models B-9, B-10, B-12, and B-14
(including Models A-3, B-6, B-8, B-11and B-13 awaiting launch)

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FREQUENCY PLAN IN USE DSCS III SATELLITE Old Frequency Plan (see figure 2-5) New Frequency Plan (see figure 2-6)

DSCS III Frequency Plans Table 2-7

at separate frequencies, one in the communications subsystem channel 1 and the other in channel 5. Each input signal is fed through the communications transponder front-end which provides preamplification and filtering. The output signal is then downconverted in two steps to the intermediate frequency (IF) input required by the TT& C COMSEC equipment (redundant KI-24s for decrypting and encrypting). The plain text output of the KI-24 is fed to the command and telemetry unit (CTU) for decoding and distribution to the intended subsystem for execution. The telemetry link is used primarily for normal command and control of the satellite support subsystems and also during vehicle anomalies. It supports Space Ground Link Subsystem compatible pseudorandom noise turnaround ranging, coherent Doppler tracking, noncoherent telemetry, secure encrypted or plain text telemetry transmission and command reception. The telemetry link uses crossed-dipole antennas mounted on opposite sides of the satellite to provide near spherical coverage. Redundant receivers provide carrier lock, and demodulate ranging and command signals. Command data cipher text is fed to the CTU which routes it to a preselected KIR-23 decoder for distribution to the intended subsystem for execution.

DSCS III satellites currently in use are equipped with two high power 40-watt TWTAs, channels 1 and 2, and four low power 10-watt TWTAs/ HESSAs for channels 3-6. A steady growth in user 30



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requirements has necessitated additional design improvements, including the modification and replacement of the 10-watt HESSAs with 16-watt LSSAs for use in channels 5-6. The last four DSCS III satellites scheduled for launch (B-8, B-11, B-6, and A-3) will receive SLEP modifications which include the replacement of all high power amplifiers (HPA) with 50-watt TWTAs, providing significantly greater linear output power than is available from either the 10-watt HESSAs or 16-watt LSSAs. Table 2-8 below shows the HPA configuration for each of the DSCS III satellites.

DSCS III HPA Configurations Table 2-8

Two low power channels (channels 5 and 6) are dedicated to EC reception and transmission using EC horns. These horns are designated E1R and E2R for reception and E1X and E2X for transmission. Channels 1 and 2 (high power) and 3 and 4 (low power) can be commanded from the ground to connect to the EC horn receive antennas or to the 61-beam receive MBA. For transmission, channels 1 and 2 are connected to the two 19-beam MBAs (E1X and E2X) or to the GDA. Channels 3 and 4 have the option of connecting to EC horns or sharing a 19-beam transmit MBA with a high power channel. In addition, channel 4 may also be switched to the GDA. 31



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The communications subsystem may simultaneously employ full Earth coverage, area coverage, and narrow coverage modes for transmission and reception. Using the MBAs, the capability exists to provide narrow coverage, area coverage, or selectively shaped area coverage by combining multiple, simultaneous narrow coverage patterns. A high gain, narrow transmit coverage capability is provided by the GDA.

The receive MBA capability includes the ability to eliminate or reduce the effect of jammers by putting them in a null between sidelobes of an NC beam or by forming nulls in a broad area (up to full Earth coverage) antenna pattern. The receive and transmit MBAs have the ability to simultaneously cover multiple areas, thereby maximizing link gain between terminals in the illuminated areas and reducing the effect of off beam jamming signals. This capability is not normally used during naval operations, but may be employed as directed for contingencies.

Each transponder channel is capable of relaying, with minimal performance degradation, time-division multiplexer (TDM)/ FDMA, CDMA, and time-division multiple access (TDMA) signals. When relaying FDMA signals, the transponder HPA must operate in an essentially linear mode. CDMA and TDMA signals permit operation in a near-saturated mode. The gain of the transponder is controlled prior to the TWTA/ HESSA to ensure the desired degree of TWT saturation for varying input levels. Input variations depend on the number of uplink signals and the EIRP of the Earth terminals.

204. NATO/ ALLIED SATELLITE SYSTEMS A. NATO Satellite System. The NATO Satellite System consists of an active communications satellite, 27 satellite ground terminals (SGT), 2 control centers, and the NATO school segment at Latina, Italy (see table 2-9). To communicate with NATO SGTs, Navy ships serving NATO support roles must shift to the NATO satellite and join the NATO spread spectrum network. NATO SGTs may provide naval support upon request. However, Navy circuits must be extended to NCTAMS Europe/ Central (EURCENT) or Atlantic (LANT), or NCTAMS EURCENT Detachment London for baseband support.

B. NATO IV-A Satellite Description. The NATO IV-A satellite became operational in 1991. It is a three-axis stabilized vehicle with a total weight (at lift off) of 1,452 pounds (660 kilograms). Two solar array panels generating 1200 watts of electricity provide power for the spacecraft and its payload. NiCd batteries provide power during solar eclipse. The TT& C subsystem operates in the 8-GHz band and employs spread spectrum protection with encryption. The altitude and orbit control subsystem uses infrared Earth sensors to maintain position. The design life of the satellite is 7 years.

The NATO IV-A satellite provides communications in the SHF and UHF bands. The SHF transponder provides four channels. The UHF transponder provides two channels. The frequencies, antennas, EIRP, and channel bandwidths are reflected in table 2-10. Spacecraft control is maintained by the Royal Air Force (RAF) with assets at Oakhanger, UK. Operation control is maintained by the 32



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DESIGNATION LOCATION DESIGNATION LOCATION
F1 Kester, Belgium Main Control Center F13 Izmir, Turkey
F2 Euskirchen, Germany F14 Verona, Italy
F3 Northwest, Virginia F15 Keflavik, Iceland
F4 Oakhanger, UK F16 Bjerkvik, Norway
F5 Eggemoen, Norway F17 Balado Bridge, UK
F6 Ankara, Turkey F18 Folly Lake, Canada
F7 Civitavecchia, Italy F19 Gibraltar
F9 Schoonhoven, Netherlands F20 Bad Bergzabern (Landau), Germany
F10 Lundebakke, Denmark F25 T1 (Transportable)
F11 Atalanti, Greece F29 Saxa Vord, UK
F12 Lisbon, Portugal Not yet designated T2-T7 (Transportable)
Note: SGTs at Carp, Canada (F8) and Catania, Italy (F21) have been closed.
NATO Satellite Ground Terminals
Table 2-9

NATO IV-A Characteristics
Table 2-10
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Main Control Center (MCC) at Kester, Belgium, or the Alternate Control Center (ACC) at Oakhanger, UK.

The NATO IV-A SHF footprint includes Eastern Canada, the Atlantic, parts of North Africa, Europe, and Southeastern Greenland (approximately 80 o west to 60 o east, 25 o south to 75 o north). The UHF footprint covers the Eastern United States, the Atlantic, South America, Africa, and most of Greenland (approximately 90 o west to 60 o east, 75 o south to 75 o north).

C. SKYNET 4 Satellite. The SKYNET 4 satellite was launched by the United Kingdom in 1991. SKYNET 4 is a British version of the NATO IV satellite. NATO IV and SKYNET 4 satellites are essentially identical for operational purposes.

PART 2 EARTH SEGMENT

205. BACKGROUND The Earth segment of the DSCS SHF SATCOM system consists of those satellite terminals assigned to the Army, Navy, Marine Corps, and Air Force for operation and maintenance. The SHF SATCOM terminals in DSCS are categorized as standard, heavy, medium, light, and others including: fixed shore, GMF, jam-resistant secure communications, airborne, shipboard, and Diplomatic Telecommunication System (DTS) terminals. The Earth segment serves the following basic functions:

Receives transmitted IF signals from one or more modulators, upconverts the IF signals to satellite carrier frequencies, amplifies the carriers to an appropriate level, and transmits these carriers through the directional antenna to the satellite.

Receives the satellite downlink signals at the directional antenna, amplifies the signals in an LNA, downconverts the amplified signals to an IF, and passes the IF to one or more demodulators. 206. SHF SHORE TERMINALS Subsequent paragraphs describe the various SHF Earth terminals used within the DSCS. Figure 2-7 illustrates a simplified SHF system block diagram showing the major components of a shore terminal.

A. AN/ GSC-39( V). The AN/ GSC-39( V) 1 is the standard DSCS medium terminal (MT) for fixed sites. The AN/ GSC-39( V) 2 is designed for transportable requirements. With the exception of the interface hardware, all major components are fully interchangeable between the (V) 1 and (V) 2 versions. Table 2-11 lists the technical characteristics of the AN/ GSC-39( V). Designed to operate within the SHF X-band spectrum, the AN/ GSC-39( V) is a multiple carrier, 34



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Figure 2-7
Shore SHF SATCOM System Block Diagram

TECHNICAL CHARACTERISTIC VALUE
Antenna Type 38-foot Cassegrain
Feed Five horn pseudomonopulse
Pedestal Type Elevation over azimuth (EL/ AZ) kingpost
Polarization: (a) Transmit Right-hand circular
(b) Receive Left-hand circular
Frequency: (a) Transmit 7.9 to 8.4 GHz
(b) Receive 7.25 to 7.75 GHz G/ T 34 dB/ K minimum
IF Bandwidths: (a) 70 MHz - 40 MHz
(b) 700 MHz - 125 MHz
EIRP: (a) Normal Mode +119 dBm
(b) Combined Mode +122 dBm
Simultaneous RF Carriers:(a) Transmit Up to 9
(b) Receive Up to 15
Tunability 500 MHz in 1 kHz increments
Tracking Accuracy 0.03 o peak
Mean Time Between Failures (MTBF) 1,000 hours maximum
Mean Time To Repair (MTTR) 1 hour maximum

AN/ GSC-39( V) Technical Characteristics Table 2-11

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500-MHz instantaneous bandwidth terminal. The heart of the communications equipment features wideband access at 70 and 700 MHz IF to accommodate both analog and digital interfaces. The antenna subsystem consists of a 38-foot, high-efficiency reflector and a pedestal housing the drive mechanisms. It is a Cassegrain feed system with a five horn pseudomonopulse antenna that can be dismantled and stored in reusable containers for rapid deployment. Receive LNAs installed in a redundant configuration are physically mounted at the base of the feed horn on the rear of the antenna and have a maximum noise temperature of 30 degrees Kelvin (K). The LNA provides a signal gain of 53 dBm and has 15 down-converters. The transmit side has nine up-converters and two TWTAs with an output of five kilowatts (kW) each. A switch combining network permits the power amplifiers to operate in a redundant or parallel configuration. The parallel configuration combines the power output of the transmitters at 10 kW.

B. AN/ GSC-52( V). The AN/ GSC-52( V) is a fixed or mobile, medium-size SHF SGT designed for use with the DSCS space segment. It is a high-capacity, high-altitude electromagnetic pulse (HEMP) protected terminal that uses pseudo-monopulse scanning for operator-selectable manual tracking, memory tracking, or acquisition/ auto tracking of the satellite. The terminal consists of an antenna subsystem, a receive subsystem, a transmitter subsystem, and tracking/ servo subsystem. Figure 2-8 illustrates the AN/ GSC-52( V) antenna. The antenna subsystem has a Cassegrain feed, 38-foot parabolic-reflector antenna, an elevation over azimuth pedestal, and a servodrive mechanism. Modems provide a 70 or 700-MHz IF to the up-converters whose RF outputs are combined into a single RF signal in the 7.9 to 8.4 GHz range

Figure 2-8 AN/ GSC-52( V) 36



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with a bandwidth as wide as 500 MHz. The composite signal is amplified by the TWTA and fed, via waveguides, to the antenna subsystem. On the receive side, the antenna receives an RF signal at 7.25 to 7.75 GHz, amplifies the signal using LNAs and the interfacility amplifiers, and passes the signal to down-converters which provide a 70 or 700-MHz IF output to the modem. The AN/ GSC-52( V) uses 12 up-and down-converters. The AN/ GSC-52( V) ground terminal is capable of manned or unmanned operations through a centralized control, monitor, and alarm subsystem that provides computer-aided configuration for control, status and performance monitoring, equipment calibration, fault isolation, and automatic switching of redundant equipment to replace a faulty unit. The AN/ GC-52 modernization program will also increase the total number of uplink and downlink converters. Table 2-12 lists the technical characteristics of the AN/ GSC-52( V) terminal.

AN/ GSC-52( V) Technical Characteristics Table 2-12
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C. AN/ FSC-78( V). The AN/ FSC-78( V) is a fixed SHF SATCOM heavy SGT operating in the X-band frequency range. The terminal is composed of six subsystems, including antenna tracking, transmitter, receiver, frequency reference, control, and monitoring. The antenna is a 60- foot diameter, high-efficiency, parabolic reflector providing an antenna gain-to-noise temperature ratio (G/ T) of 39 dB/ K. The reflector is mounted on an elevation-over-azimuth-configured pedestal. Figure 2-9 illustrates the AN/ FSC-78( V) antenna. Cryogenically cooled, parametric amplifiers provide 30 dB of gain and an antenna G/ T ratio of 39 dB/ K. The antenna terminal equipment has a tracking converter, 15 down-converters, and 9 up-converters. Only 10 of the down-converters are normally active at one time; the remaining 5 are in hot standby. The output signals from the up-converters are fed to a 5-kW TWTA, providing a radiated antenna signal of 500-MHz bandwidth at an EIRP of 124 dB referenced to one watt (dBW). A redundant 5 kW power amplifier can be operated in parallel with the primary power amplifier to provide an output equivalent to 10 kW at an EIRP of 127 dBW. The down-converters translate the receive signal of 7.25 to 7.75 GHz to 70-MHz IF (40-MHz bandwidth) or a 700-MHz IF (125-MHz bandwidth). The up-converters translate the 70 or 700-MHz IF input signal, with bandwidths of 40 or 125 MHz, to the transmit frequency of 7.9 to 8.4 GHz. The Army Heavy Terminal/ Medium Terminal (HT/ MT) modernization of the AN/ FSC-78/ 79 and AN/ GSC-39 Earth terminal will increase the total number of the uplink and downlink converters. Table 2-13 lists the technical characteristics of the AN/ FSC-78( V).

Figure 2-9
AN/ FSC-78( V) Antenna
38



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AN/ FSC-78( V) Technical Characteristics
Table 2-13

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D. Non-DSCS SHF 1. AN/ FSC-79 Fleet Broadcast Terminal. The AN/ FSC-79 is a fixed SHF SATCOM terminal capable of one transmit channel and one receive beacon channel, designed specifically to support the Navy Fleet Satellite Broadcast. It is housed in a permanent facility and uses a 60-foot diameter, high-efficiency parabolic reflector antenna mounted on an elevation over azimuth configured pedestal. The terminal operates on a single channel, tunable in 1-kHz increments over a transmitting frequency range of 7.9 to 8.4 GHz, at a maximum output of 10,000 watts.

2. OM-51A/ FR Modem. The OM-51A/ FR modem is an integral part of the Fleet Broadcast subsystem. This spread spectrum modem, when used in combination with the AN/ FSC-79 SATCOM terminal, provides an RF transmission capability in a high-level jamming environment. The basic function of this modem is to provide RF analog and digital conditioning on circuits and frequency synthesizing for dual redundant transmission and reception. The unit interfaces with the AN/ FSC-79 terminal and the amplifier-converter of the AN/ SSR-1A receiver system. When uplinking the broadcast to Fleet Satellite channel 1, only one modem is used. The OM-51A/ FR installation consists of a standard cabinet containing seven slide-mounted drawer assemblies. These assemblies include a summary control panel, frequency synthesizer, receiver-synchronizer, coder-modulator, demodulator, and two power supplies.

3. ON-163A/ FR Interconnecting Indicator Group. The ON-163A/ FR is a companion installation to the OM-51A/ FR modem. The interconnecting indicator group provides a secondary modulation mode to the Fleet Satellite Broadcast shore terminal. The equipment contains an OM-43A/ USC modem, a power supply, a UHF and IF patch panel, a data patch panel, and three units of test equipment. The IF section of the patch panel provides the capability for patching the output of either the OM-51A/ FR or the OM-43A/ USC as the uplink signal to the AN/ FSC-79 transmitter. The UHF section has the capability to patch a UHF test signal to an online AM-6534/ SSR-1 down-converter. The data patch panel enables patching the 1.2 kbps data stream to the input of the OM-51A/ FR or the OM-43A/ USC. The three units of test equipment are a frequency counter, a spectrum analyzer, and a UHF signal generator.

207. SHIPBOARD TERMINALS The functional block diagram in figure 2-10 illustrates the relationships of the major components of shipboard SHF SATCOM terminal equipment.

A. AN/ WSC-6( V). The AN/ WSC-6( V) shipboard terminal is designed for use on surface ships to satisfy the Navy SHF ship-to-shore communications requirements while remaining within the cost, weight, and size constraints of the shipboard environment. The AN/ WSC-6( V) consists of the radio group and the antenna group as illustrated in figure 2-11. The antenna group is configured in a single or dual configuration to give 360 degrees of antenna coverage. The technical characteristics of the WSC-6( V) are illustrated in table 2-14. 40



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Figure 2-10
Shipboard AN/ WSC-6 Terminal Block Diagram

B. AN/ WSC-6( V) Variants 1. AN/ WSC-6( V) 1. The AN/ WSC-6( V) 1 SHF terminal is installed aboard SURTASS vessels. The terminal is interfaced with the MD-1030A( V) binary phase-shift keying (BPSK) narrowband modem and has a 4-foot antenna.

2. AN/ WSC-6( V) 2. The AN/ WSC-6( V) 2 is installed aboard numbered fleet flagships and uses the OM-55( V)/ USC spread-spectrum AJ modem and the ComQuest CQM-248A phase-shift keying (PSK) narrowband modem and has one or two 7-foot antennas. The (V) 2 terminal uses an 8-kW transmitter with either the spread-spectrum modem or the narrowband modem or both if an IF patch is used. The (V) 2 can also use a 350-watt TWTA with the narrowband modem in conjunction with the 8-kW Klystron power amplifier with the spread-spectrum modem if the diplexer is used. 41



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Figure 2-11
AN/ WSC-6 Shipboard Terminal
42



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AN/ WSC-6( V) Technical Characteristics Table 2-14 43



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3. AN/ WSC-6( V) 4. The newer generation AN/ WSC-6( V) 4 SHF terminal is installed aboard CV/ CVN, LHA, and LHD class ships. These terminals use the CQM-248A narrowband modems, the (V) 2 up-and down-converters, 350-watt TWTAs and 7-foot antenna( s).

4. AN/ WSC-6( V) 5. The AN/ WSC-6( V) 5 is the shipboard SHF terminal that will replace the (V) 2 and (V) 4 terminals on "big deck" platforms. It will use Versa Module Eurocard (VME) 32-bit bus technology employing circuit card assemblies to replace the antenna and servo-controllers; the up-, down-, and tracking converters; the local operation control center; and the radio frequency selector. It will provide dual termination capability at the converter to allow connectivity to GMF, and use one or two 7-foot antennas. In addition it will have redundant (back-up) TWTAs (2kW and 350W). These terminals will use two narrowband modems; one will be the CQM-248A, the second is to be determined.

5. AN/ WSC-6( V) X. The planned AN/ WSC-6( V) X will provide SHF capability to CG 47, DDG 51, and TOMAHAWK-capable SPRUANCE-class "shooters" as well as well as Combat Logistics Force (CLF) and LPD 17 class ships. The terminal will consist of a single rack of equipment, FDMA modems, and either single or dual 7-foot parabolic antennas.

208. INTEGRATED TERMINAL PROGRAM The Integrated Terminal Program (ITP) will provide flexible, responsive, wideband connectivity via military satellite communications systems by leveraging commercial technology and applying common electronics and components. The emphasis of this initiative is to use proven commercial off-the-shelf (COTS) components and low observable antenna (LOA) systems to provide a foundation for a modular evolution to multiband terminals. The LOA system will be achieved by integrating the antennae designs with the new ship topside reduced signature design being developed for the LPD 17 and SC 21. This design provides integrated directive antennae for topside space, weight, and signature reduction. Figure 2-12 illustrates the components of the ITP.

209. GROUND MOBILE FORCE TERMINALS GMF SHF SATCOM terminals operate as a special-user subnetwork through the DSCS. The GMF SHF SATCOM media extends the range of terrestrial communications with improved reliability, speed, and deployment setup time to ground users. It supports the need to exchange communications traffic during all phases of actual conflicts and training exercises. GMF terminals can be deployed in subnetworks ranging in complexity from a small independent cluster up to an elaborate network capable of supporting joint and combined operations. These subnetworks are built on the basis of interconnected clusters or stars using nodal or hub terminals to support spoke and link terminals. Figure 2-13 illustrates a simplified concept for a typical tri-Service GMF deployment. Figure 2-14 illustrates the AN/ TSC-93B GMF SATCOM terminal. Table 2-15 lists the technical characteristics of GMF terminals. GMF configurations normally operate on either channel 1or 2 of the DSCS. 44



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Figure 2-12
Integrated Terminal Program Components

Figure 2-13
GMF Tri-Service Deployment
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Figure 2-14
GMF Satellite Communications Terminal AN/ TSC-93B

GMF Terminals Technical Characteristics
Table 2-15

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PART 3 BASEBAND SYSTEMS

210. BACKGROUND Baseband systems comprise the equipment necessary to process, format, and interface the user data channels between user equipment and the IF input/ output (I/ O) of satellite terminals. The equipment at the DSCS gateway includes the tactical baseband equipment necessary to interface with the DSCS. The DSCS is an all digital transmission system and the gateways are designated as single or dual terminal, depending on whether the gateway can access one or two satellite transponders simultaneously. The baseband equipment configuration depends on the type of interconnect facility used to transmit signals between the technical control facility (TCF) and the Earth terminals. Table 2-16 lists the GMF gateways to DSCS and their configurations. The following subparagraphs describe the most common system gateways.

SITE CONFIGURATION SATELLITE ACCESS
Eskan, SA Dual EASTLANT
Croughton, UK Dual EASTLANT / IO
Landstuhl, Germany Triple WESTLANT / IO / EASTLANT
Lago Di Patria, Italy Dual EASTLANT / IO
Wahiawa, HI Dual WESTPAC / EASTPAC
Finegayan, Guam Single WESTPAC
Camp Zama, Japan Single WESTPAC
Ft. Buckner, Okinawa, Japan Dual IO / WESTPAC
Camp Roberts, CA Dual EASTPAC / WESTPAC
Ft. Detrick, MD Triple EASTPAC / WESTLANT / EASTLANT
Ft. Meade, MD Quad EASTPAC/ WESTLANT / EASTLANT
Northwest, VA Triple EASTLANT / WESTLANT
Fort Belvoir, VA Triple EASTPAC / EASTLANT / WESTLANT

DSCS GMF Gateways
Table 2-16

A. Digital Communications Subsystem (DCSS). The DCSS includes the modulation, multiplexing coding, and processing equipment necessary for the assembly of various types of user data into a digital form suitable for transmission over a satellite link in the protected or unprotected modes. In the unprotected mode, the DCSS will utilize BPSK modulation. Transmission through the satellite will be accomplished in FDMA. Quadrature phase-shift keying (QPSK) modulation has been introduced into the system to provide greater spectrum 47



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conservation. At this time, both BPSK and QPSK types of modulation can be used for the unprotected mode. The protected mode will employ QPSK modulation. Transmission through the satellite will be accomplished by means of CDMA. The DCSS interfaces to the user at baseband data rates and with the satellite Earth terminal at the 70-or 700-MHz IF.

A DCSS will be installed at each Earth terminal and will be compatible with all terminals associated with the DSCS. At locations where the TCF is removed from the Earth terminal, portions of the DCSS will be located at both the TCF and Earth terminal, interconnected by a radio relay or cable.

B. Multiplex Equipment 1. AN/ FCC-98( V) 1. The AN/ FCC-98( V) 1 TDM/ demultiplexer is a full-duplex, 24-channel, telecommunications device with full transmit and receive capabilities. Each multiplexer is configured to specific communications systems requirements by the installation of selected combinations of voice, data, and data-timing plug-in modules. Once installed and operational in a communications system, the multiplexer/ demultiplexer generally requires only scheduled maintenance. Troubleshooting and corrective maintenance are completed to the module level by station forces with the unit in place. The output pulse-coded modulation (PCM) mission bit stream (MBS) can extend to 1.544 megabits per second (Mbps), dependent on the module configuration.

2. AN/ FCC-99( V). The AN/ FCC-99( V) multiplexer/ demultiplexer provides redundant, full-duplex second-level time division multiplexing and demultiplexing of I/ O data between first-level and third-level communications equipment primarily associated with shore installations. It accepts up to eight non-return-to-zero (NRZ) or bipolar data inputs, each operating at a nominal rate of 1.544 Mbps. Operational configuration provides additional NRZ data rate options of 3.088 Mbps per port and 6.176 Mbps per port. The multiplexer set operates in both synchronous and asynchronous modes with any combination of port data rates whose combined rate does not exceed 12.352 Mbps. Synchronous data is multiplexed into the MBS using a fixed-rate conversion. Asynchronous data is multiplexed using positive bit stuffing.

3. AN/ FCC-100( V) 1/ 2. The AN/ FCC-100( V) 1/ 2 low speed time-division multiplexer (LSTDM) operates with full-duplex capabilities at speeds up to and including 256 kilobits per second (kbps) providing a 16-port configuration capable of synchronous, asynchronous, isochronous (transitional encoded), and diphase data transmission. It is configured at the user's side of the communications system. A down-loading capability permits one operator to configure the local or the remote LSTDM from a single unit for system operation. Once configured, the LSTDM is capable of performing multiplexing, demultiplexing, timing, control, synchronization, framing, monitoring, and alarm reporting. Timing for the LSTDM is provided by a highly accurate, internal oscillator or by an external timing source. Local and remote data loopback capabilities allow for overall link testing and trouble isolation 48



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from a single LSTDM to the remote LSTDM. This multiplexer has been installed on selected flag-configured ships in the AN/ TSC-93B (modified) SHF QUICKSAT terminal.

4. AN/ FCC-100( V) 3. The AN/ FCC-100( V) 3 LSTDM operates with full-duplex capabilities at speeds from 1200 bps to 2.048 Mbps providing a 16-port configuration capable of synchronous, asynchronous, isochronous, and diphase data transmission. It is configured at the user's side of the communications systems. A down-loading capability permits one operator to configure the local or the remote LSTDM from a single unit for system operation. Once configured, the LSTDM is capable of performing multiplexing, demultiplexing, timing, control, synchronization, framing, monitoring, signaling information (i. e., request-to-send, clear-to-send), and alarm reporting. Timing for the LSTDM is provided by a highly accurate, internal oscillator or by an external timing source.

5. AN/ FCC-100( V) 4X. The AN/ FCC-100( V) 4X is an LSTDM with full-duplex capabilities. The AN/ FCC-100( V) 4X operates at speeds up to 256 kbps and provides 16 ports capable of handling any mix of synchronous, asynchronous, isochronous and diphase data transmission. The AN/ FCC-100( V) 4X is configured at the user's site to satisfy specific communications system requirements. The downline loading capability permits an operator to configure a remote AN/ FCC-100( V) 4X from a central unit, thereby eliminating the need for an operator at a remote site during reconfiguration. Once installed and configured, the AN/ FCC-100( V) 4X is capable of performing multiplexing, timing, control, synchronization, framing, monitoring, and alarm reporting. Timing for the AN/ FCC-100( V) 4X is provided by a highly accurate, internal oscillator or from an external timing source.

6. TD-1389( V). The TD-1389( V) is a microprocessor-controlled TDM. It is capable of accepting up to 12 channels of digital, analog, and frequency-shift keying (FSK) synchronous or asynchronous signals. The independent multiplexing/ demultiplexing operations can be configured so that user channel data of different and unrelated forms can be processed. The device can serve as a low rate multiplexer (LRM) or as a loop group multiplexer. The aggregate output can be up to 256 kbps. A remote option that duplicates all of the front panel functions (except power control) is available. This LRM is currently being installed in shore and SHF-configured platforms as a replacement for the TD-1251 multiplexer/ demultiplexer under the SATURN program.

7. TIMEPLEX LINK/ 2+. The LINK/ 2+ has become the primary full-or half-duplex, first-level multiplexer for Navy tactical SHF communications. The LINK/ 2+ is expandable to 54 module slots. It will replace or augment the AN/ FCC-100( V) in some applications. Navy SHF will use a basic 18-slot chassis, with the capability of an 18-slot-expansion chassis (two-nested) system. The LINK/ 2+ allows for greater I/ O (user) flexibility, advanced network management and versatility (i. e., automatic rerouting or self-healing) than the current first-level multiplexers (e. g., AN/ FCC-100( V) 1 through (V) 7). It is capable of processing digital data, voice (voice compression), and video by synchronous, asynchronous, isochronous, asymmetrical (different transmit and receive speeds on the same channel), and simplex signal processing. The LINK/ 2+ is capable of operating 12 trunks at aggregate data 49



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rates of 4.8 kbps to 2.048 Mbps each (not to exceed 7 T-1s, each at 1.544 Mbps). It also has the ability to interface with the Defense Information Systems Agency's DCSS Integrated Digital Network Exchange as a trunk and will allow for eventual worldwide connectivity (via the DCSS) for Navy SHF communications.

C. Modems and Subsystems 1. ComQuest CQM-248A. The CQM-248A satellite modem is used in SATCOM applications that require continuous transmission and reception. When a network of CQM-248A modems is employed, a fixed assignment system known as FDMA is used. FDMA works on the principle of dividing the total bandwidth of the communication channel into a number of discrete segments and allocating each segment exclusively to a user. Guard bands are used between each segment of the frequency band to prevent interference between users. The advantage of the FDMA system is its simplicity; once the channel capacity is divided among the users, each can operate independently of the others. There are several enhancements to the CQM-248A modem that maximize its performance and provide for more efficient use of satellite bandwidth when using FDMA. These enhancements include the following:

2. Stanford Telecommunications (STeL) 1105A. The STeL 1105A is a TDMA -DAMA modem that can be configured to support a variety of high and low speed circuits. It has five port interfaces which support multiple data rates up to a total aggregrate of 256 kbps. It can support a single DAMA network and is designed to operate in a "hub-spoke" configuration, with all communications relayed through a central shore site (hub) Network Control Terminal.

3. OM-83, Universal Modem System (UMS). The UMS (OM-83) consists of a family of modems suitable for use within SHF terminals to achieve communications networks via 50



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SHF transponder units. It is a multimode modem that can operate in both FDMA and AJ modes. The Navy configuration consists of one Basic Control Unit (BCU) for High Data Rate Mode, and three Communications Units for interoperability. It provides such functions as communications network management and execution, KEYMAT management, and positive control via an in-band orderwire. UMS is also designed to eliminate outages from periodic timing losses during handover of RF signals from one antenna to another by providing seamless signal transfer between antennas during ship movements. In addition, the UMS' electronic warfare support measures (ESM) mode is designed to enable full throughput while operating in moderately hostile information warfare (IW) environments. The modem will replace, as part of the STEP program, the current DSCS USC-28 and Navy OM-55 modems. UMS is scheduled to be fielded in FY 2000. Table 2-17 lists the UMS data rates used in various modes of operation.

MODEPURPOSE DATA RATE
(Aggregate channel data rates)
LDR MODE A Communications and control 18.75, 37.5 and 75 bps
LDR MODE B Communications and control 75, 150, 300, 600, 1200, 2400, 4800, 9600, 16000, and 19200 bps
LDR MODE B ESM 75, 150, 300, 600, 1200, and 2400 bps
LDR MODE B TDMA Communications 75, 110, 150, 300, 600, 1200, 2400, 4800, 9600, 16000, and 19200 bps (75, 150, 300, 600, 1200, 2400, 4800, 9600, and 19200 bps)
MDR OFHMA Communications 16, 32, 64, 72, 128 , 144, 192, 256, 288, 384, 512, 576, 768, 1024, 1152, 1536, 1544, and 2048 kbps
MDR FDMA Communications 16, 32, 64, 72, 128, 144, 192, 256, 288, 384, 512, 576, 768, 1024, 1152, 1536, 1544, 2048, 4096, and 8448 kbps
MDR ESM 4.8, 9.6, 16, 32, 64, and 128 kbps
MDR TDMA Communications 16, 32, 64, 128, and 256 kbps (256, 512, 1024, and 2048 kbps)

UMS Data Rates and Modes of Operation
Table 2-17

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4. MD-1030A( V). The MD-1030A( V) digital data modem was developed for the SURTASS program and was used in QUICKSAT installations to convert baseband digital signals. The modem is a full-duplex communications modem operating at baseband data rates from 75 bps to 50 kbps (coded) and 75 bps to 100 kbps (uncoded) on an agile 69-to 71-MHz IF, adjustable in 20-kHz increments. It has a built-in multiplexing/ demultiplexing capability for processing up to three separate baseband channels if required.

5. OM-55( V)/ USC. The OM-55( V)/ USC is an AJ, multiple-channel modem designed to interface SHF SATCOM terminals with digital data and voice baseband equipment. It is an SSMA modem, employing CDMA and TDMA techniques. The modem provides up to four full-duplex channels of voice and digital data in any combination and five 75-bps link orderwires (LOW). One of the five LOWs will be used as the net orderwire (NOW)/ return net orderwire (RNOW). This NOW/ RNOW is used to keep the control and net terminals in synchronization. The modem operates at 75 bps, 1.2, 2.4, 4, 4.8, 8, 9.6, 16, or 32 kbps synchronous or asynchronous. The OM-55( V)/ USC modem can control the time sharing of the SHF terminal in the DSCS electronic counter-countermeasures (ECCM) network if the terminal is the NCT. By direction, the operator can designate the modem as a control terminal, net operation terminal, net entry terminal, or multiple access mode terminal. The net operation terminal mode provides maximum AJ protection and a short entry time.

6. AN/ USC-28( V). The AN/ USC-28( V) SSMA AJ modem is capable of providing 15 receiver/ transmitter channels and will interface with the OM-55( V)/ USC shipboard modems. It operates critical control circuits and LOWs. The modem interfaces with the up-and down-converters and with the external KY-883 error-correcting coders at shore terminals. The AN/ USC-28( V) can accept data rates of 75 bps to 2.5 Mbps. These modems are used at NCTs to interface the GMF terminals into the DSCS network.

7. OM-73( V)/ G. The OM-73( V)/ G modem provides digital communications at high data rates (16 kbps to 20 Mbps), and includes up to 8 duplex or 16 simplex links under a single master controller. The OM-73( V)/ G is compatible with existing equipment for operation of DSCS III satellites. It is interoperable in the SHF mode with the MD-1002/ G (Viterbi, KY-801B coder/ decoder), the CQM-248A, and the MD-1030A( V) modems. The modem is capable of BPSK, QPSK, or offset QPSK (OQPSK) modulation.

8. KY-883 Burst Error Coder (BEC). The KY-883 BEC is primarily employed with the AN/ USC-28( V) and OM-55( V)/ USC modems. It is a digital forward error-correcting device that enhances Gaussian noise conditions, burst jamming detection, and data loss protection during antenna switchover. It is a full-duplex coder which can accept data rates of 75 bps to 100 kbps.

211. SHIPBOARD TERMINALS COMPARISON Table 2-18 reflects the composition of the current shipboard terminals. None of these terminals is interoperable except through an intermediate shore site. 52



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Current SHF Shipboard Terminals Comparison
Table 2-18

53