The Space Congress® Proceedings 1976 (13th) Technology For The New Horizon

Apr 1st, 8:00 AM

Marisat -A New Commercial Application Of Communications Satellite Technolgy

Edward J. Martin Assistant Vice President, Mobile Systems, COMSAT General Corporation,Washington, D.C.

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Scholarly Commons Citation Martin, Edward J., "Marisat -A New Commercial Application Of Communications Satellite Technolgy" (1976). The Space Congress® Proceedings. 3. https://commons.erau.edu/space-congress-proceedings/proceedings-1976-13th/session-8/3

This Event is brought to you for free and open access by the Conferences at Scholarly Commons. It has been accepted for inclusion in The Space Congress® Proceedings by an authorized administrator of Scholarly Commons. For more information, please contact [email protected]. MARISAT -- A NEW COMMERCIAL APPLICATION OF COMMUNICATIONS SATELLITE TECHNOLOGY

Edward J. Martin Assistant Vice President - Mobile Systems COMSAT General Corporation Washington, D.C.

ABSTRACT THE MARISAT SYSTEM A new type of commercial satellite communi­ The MARISAT System configuration is shown cations system called MARISAT is in its in Figure 1. Three satellites have been final stages of deployment for operational procured, one each for emplacement over the service beginning this year. This system Atlantic and Pacific Ocean areas and a third will provide two different communications as an on-the-ground spare. Each satellite services by using two different types of contains three communications repeaters. communications repeaters on a single One of these operates in the UHF bands and satellite. One service is dedicated to U.S. contains one wideband and two narrowband Navy requirements; the second service is channels exclusively for use by the U.S. the first commercial offering of maritime Navy. Each of these channels may be mobile satellite communications. Through activated or deactivated by ground command. this latter service the quality and In this manner, satellite prime power reliability of commercial satellite released from the UHF service is made communications will be extended to ships available to the other communications operating on the high seas. This will be repeaters. The Navy has contracted for use the first step in the evolution of an of all channels in both satellites for the international global maritime satellite first year with firm options to lease all communications system. channels on a yearly basis continuously throughout a three-year period. This paper summarizes the composition and design of the MARISAT System and gives a Two other repeaters are included for shore- progress report on the status of its to-ship and ship-to-shore civil maritime development and deployment. communications, respectively. The shore-to- ship repeater translates C-band transmissions received from the earth station at frequen­ INTRODUCTION cies near 6 GHz to L-band frequencies near 1.5 GHz for relay to commercial ship stations, For over a decade, now, we have seen the The L-band output power level can be success of commercial applications of controlled by ground command consistent with satellite technology to communications. the level of activation of the Navy's UHF In the 1960's we had the early development repeater. of an international point-to-point commercial satellite communications system The ship-to-shore repeater performs the (INTELSAT) followed more recently by the reverse process by translating transmissions deployment of the first domestic point-to- received near 1.6 GHz from the ship station point satellite communications systems. back to frequencies near 4 GHz for relay to Now, in 1976, we are standing at the thres­ the earth stations. The 6 and 4 GHz bands hold of a new commercial use of this are also used for tracking, telemetry and technology, namely, communications with command functions. small earth stations placed aboard mobile vehicles. The first step will be taken in The earth stations provide a link to COMSAT the form of the MARISAT satellite communi­ General's Control Center in Washington,D.C. cations system which is inaugurating as well as the interface for interconnection service this year. A common satellite will of the system with the terrestrial tele­ provide service to the United States Navy communications networks. General spacecraft while at the same time providing the first maintenance and telemetry monitoring will commercial offering of maritime mobile be performed and command instructions will satellite services to the commercial be issued from the COMSAT General Control shipping community. This system represents Center. a major step forward in that it brings to practical commercial reality the use of communications satellites by a large number of small, inexpensive earth stations.

8-9 The MARISAT System is jointly owned by four satellites. MARISAT employs conventional communications companies in an organization spin stabilization with a despun antenna which has come into force earlier this year farm coupled to three spinning repeaters called the MARISAT Joint Venture. The through a non-contacting coaxial rotary ownership interest of the four companies is joint. The apogee motor, the FW-5, is the as shown in Figure 2. In addition to its same motor used in the TELESAT and WESTAR majority ownership interest, COMSAT General series of spacecraft. This motor is serves as the MARISAT System Manager for undersized, however, for the increased the Joint Venture. The elements of the spacecraft weight permissible with the jointly owned system include the satellites Thor-Delta 2914 and must be augmented by and certain of the land based control on the spacecraft hydrazine propulsion system communications equipment and facilities. during transfer orbit in order to achieve COMSAT General is furnishing, in addition, synchronous orbit injection. other facilities for MARISAT use which will be shared with other COMSAT General programs, The spinning portion of the satellite is most notably the COMSTAR domestic satellite approximately 85 inches in diameter by system. 63 inches in length, with an overall length of about 148 inches including the The ship terminals required to complete the antenna farm (see Figure 6) . The space­ communications connection between shore craft dry weight is expected to be about stations and ship are furnished separately 30 pounds below the allowable dry weight by each co-owner of the MARISAT System or of approximately 700 pounds. This will acquired independently by ship owners and permit the use of additional hydrazine fuel operators. beyond the minimum mission requirement. North-south stationkeeping is not planned. Communications service will be provided to Rather, the initial orbit will be biased the two coverage regions depicted in such that the inclination of the orbit Figure 3. These service coverage regions, plane will be maintained within 2.5° of the which encompass more than 2/3 of the world's equatorial plane over a five-year service major sea lanes, are achieved by selecting life. satellite positions of 15°W and 176.5 E longitude. Two shore stations in the Electrical power will be derived from United States provide the initial service fixed solar panels mounted on the with the satellites. One of these is at cylindrical portion of the spacecraft. Southbury, Connecticut for service through The panels are somewhat larger (63 inches the Atlantic satellite and the other at by 85 inches) than the TELESAT panels to Santa Paula, California for service through take full advantage of the eight-foot the Pacific satellite. Figure 4 shows the Delta shroud. Spacecraft power has also COMSAT General earth staion and System been enhanced somewhat through the use Control Center arrangement for operation of of 6.2 cm x 2.2 cm solar cells. Approxi­ both the MARISAT and COMSTAR systems. Each mately 300 watts of DC prime power will be of the two earth stations has three antenna available at the end of a five-year life­ systems. One limited-motion 34' antenna time. The design includes nickel-cadmium is dedicated to COMSTAR. One 42 f antenna batteries v;ith sufficient capacity to power is assigned exclusively to the MARISAT all satellite subsystems through eclipse. System. A second 42 f antenna, while normally assigned to serve the COMSTAR domestic The telemetry and command system employs system, has been designed also to serve two cross-strapped telemetry encoders and MARISAT so that a full back-up capability beacons which generate separate C-band is available at each earth station for carriers. Redundant command receivers MARISAT use. and digital decoders can decode 160 commands. The rangina function is performed by Three operating modes are possible depending demodulating the range tone transmissions upon U.S. Government use of the satellite. received from the earth station in the These are portrayed in Figure 5. The system command receiver, and routing the demodulated design permits a commercial communications tones to the telemetry beacon oscillator capacity in the low power mode (the initial which is phased modulated by the tone set mode of operation) of 1 duplex voice and before retransmission to the earth station. 44 Telex channels. Operation in the medium Figure 7 shows the complete spacecraft. and high power modes will be possible when the Navy decreases its use of the UHF repeater. EARTH STATIONS Two almost identical earth stations have THE MARISAT SATELLITE been constructed each having three antenna systems. Figure 8 shows the antenna complex The design of the MARISAT spacecraft (see and control building at Santa Paula, Figure 6) borrows heavily from flight-proven California. The basic earth stations, technology of earlier communications including buildings, utilities, antenna

8-10 systems, RF equipment as well as the track­ console includes the antenna control unit ing, telemetry and command system, are (ACU) , all the communications electronics, ready for operational use. power supplies, telephone handset and tele­ printer. The MARISAT shore station communications equipment (SSCE) has been installed and A close-up view of the comparatively simple tested at the earth stations and commercial antenna control unit is shown in Figure 12. operations are ready to begin. These earth This control is used for initial acquisition stations are being connected to the public of the satellite by the antenna steering telecommunications networks on a world­ system. The antenna steering system wide basis. Therefore, the system permits establishes a horizontal platform by near instantaneous communications between sensincr the vertical direction and correct­ ships operating on the high seas and points ing for ships 1 pitch and roll. The almost anywhere in the world. The range operator, using tables of pointing angles, of communications services includes telex, enters initial azimuth and elevation angles telephone, data and facsimile. in the ACU, the antenna locks-on to an L- band signal radiated by the satellite and from then on the antenna operation is SHIP TERMINALS^ automatic. The ship's gyrocompass is used as a reference for changes in ship's head­ Technical requirements for ship terminals ing. A step track system supplements the to operate with the MARISAT System have antenna stabilization system by correcting been adopted by the system's co-owners and for the comparatively slow changes in the have been distributed widely throughout the position of the ship and the satellite. world to interested manufacturers and other entities. Procedures have been published Figure 13 shows the simple operating controls for manufacturers to have their terminal and displays in normal use. The ship designs type accepted by the MARISAT System terminal constantly monitors the control Manager for use in the system and the channel it receives from the shore station commissioning procedures for each ship and responds automatically to shore station station to be checked out with the system instructions to process incoming messages. prior to entering operation have been For ship-to-shore traffic the operator enters issued. Ship terminal performance require­ information on the type of messages, its ments include an equivalent isotropic priority and destination and pushes a radiated power (e.i.r.p.) of 37 dBw and request button. This information is trans­ a receive sensitivity of at least -4 dB/ mitted to the shore station in a fraction deg. K. This implies use of a steerable of a second and the shore station responds antenna of about 4 feet in diameter in within G3conds through the control channel combination with a transmitter having a to set-up the desired call. Equally power level on the order of 40 watts along prompt operating arrangements set up calls with a transistorized low noise receiver. in the shore-to-ship direction. A number of companies throughout the world are active in the planning and development of ship equipment for use with MARISAT. The first and largest of such activities The first commercial satellite system for was the placement of an order by COMSAT use in communications between small stations General for 200 ship terminals from aboard ships and shore based stations is Scientific-Atlanta, Inc. being established this year. This system called M.7\RISAT should revolutionize maritime The COMSAT General ship terminal is divided communications much as the Early Bird into two major sets of equipment. The set System dramatically altered the course of of equipment designed for installation inter-continental communications over a above decks consists principally of a 4 foot decade aao. steerable parabolic antenna, transistorized transmitter and low-noise receiver, all enclosed in a Fiberglas radome. This ILLUSTRATIONS equipment without radome is shown in Figure 1. System Configuration Figure 9. The first group of these terminals Figure 2.. MARISAT System Ownership have been installed on a wide variety of Figure 3. Coverage Regions types of ships around the world. Figure 10 Figure 4. Earth Station Complex shows a typical installation on a super­ Figure 5. MARISAT Operating Modes tanker. The antenna beam, which is approxi­ Figure 6. MARISAT Spacecraft Exploded View mately 10° in width, is steered automatical­ Figure 7. MARISAT F-l ly in the direction of the satellite. Figure 8. Santa Paula Earth Station Figure 9. Ship Antenna The rest of the equipment which is designed Figure 10. ESSO Installation for installation below decks is contained Figure 11. Ship Terminal Communications Equip. in the console shown in Figure 11. This Figure 12. Antenna Control Unit Figure 13. Ship Terminal Operator's Display 8-11 SYSTEM CONFIGURATION

U.S. NAVY SHORE FACILITIES \ K UHF

6 GHz SHORE-TO-SHIP 1.5 GHz / \

SHIP-TO-SHORE / 4 GHz "* 1.6 GHz \ COMSAT COMM. GENERAL TRACKING EARTH AND TELEMETRY STATION TT&C COMSAT GENERAL CONTROL CENTER

FIGURE 1

MARISAT SYSTEM OWNERSHIP 100%

86.3%

8.0% 3.4% 2.3%

COMSAT RCA WUI ITT GENERAL

FIGURE 2

8-12

3

FIGURE FIGURE

I 00 COMSAT GENERAL EARTH STATIONS

DOMESTIC SATELLITES

CALIFORNIA

WASHINGTON, D.C. FIGURE 4

MARISAT OPERATING MODES AND COMMUNICATIONS CAPACITY

OPERATING LOW MEDIUM HIGH MODE

U.S. GOVERNMENT USE

COMMERCIAL DUPLEX 1 VOICE 5 VOICE* 9 VOICE* CAPACITY 44 TELEX 66 TELEX* 110TELEX*

*OTHER COMBINATIONS ARE POSSIBLE

G-12379 FIGURE 5

8-14 MARISAT SPACECRAFT EXPLODED VIEW

ANTENNA . COMMAND ANTENNA SOLAR PANEL -TELEMETRY ANTENNA

COMMAND RECEIVER

UHF MULTIPLEXER 20 WATT UHF L BAND DIPLEXER POWER AMPLIFIER ^DIGITAL ELECTRONICS

FIGURE 6

8-15 FIGURE 7 FIGURE 9

FIGURE

8-16 • I

FIGURE 11

FIGURE 10

ENTER SIGNAL ELEVATION STRENGTH

ANTENNA CONTROL UNIT

FIGURE 13 FIGURE 12

8-17