1969 (6th) Vol. 1 Space, Technology, and The Space Congress® Proceedings Society Apr 1st, 8:00 AM Satellite Communications to Mobile Terminals -A Forecast of Needs and Techniques Quintus C. Wilson Acton Laboratories, Inc. Follow this and additional works at: https://commons.erau.edu/space-congress-proceedings Scholarly Commons Citation Wilson, Quintus C., "Satellite Communications to Mobile Terminals -A Forecast of Needs and Techniques" (1969). The Space Congress® Proceedings. 4. https://commons.erau.edu/space-congress-proceedings/proceedings-1969-6th-v1/session-7/4 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]. SATELLITE COMMUNICATIONS TO MOBILE TERMINALS A FORECAST OF NEEDS AND TECHNIQUES By: Q. C. Wilson Acton Laboratories, Inc. Massachusetts ABSTRACT intersystem and interorganizational relation­ ships. Several substantial studies have shown a Economic pressures and technical devel­ specific utility of satellite communications for opments lead to an international satellite com­ navigation and mapping, administrative traffic munications and surveillance system satisfying to air carriers, Atlantic air traffic control, and the needs of many mobile users, especially world-wide weather data systems. The plan for aircraft. The dominant need is to provide satisfying all these needs is a jig-saw puzzle not three-dimensional surveillance of air space yet assembled. However, air terminal congestion around airports. The large number of carrier takes precedence as the greatest need. Air and general aircraft requires the satellite traffic controllers have demonstrated in a system and its ground control facility to carry dramatic and responsible way that they are the burden of providing adequate link margins overloaded. The FAA has attempted to find suit­ and position computation. able relief in automation and display without making progress against the tremendous in­ crease in traffic. Proliferation of airports and systems of the present kind will push the FAA budget alone above one billion dollars and push a larger burden onto local communities. A INTRODUCTION better system seems to be promised by further automation. Economic pressures and recent technical advances will lead to an international satellite Contemporary radar defies simple automa­ communications system satisfying the needs of tion. An air traffic control computer should many mobile users, especially aircraft. It is track every target. But radar was designed to timely to encourage designing complete and track single targets with the aid of an operator competitive systems in order to provide guid­ who can discriminate a real target from clutter, ance to the ITU World Administrative Radio atmospheric reflections, multipath, etc. The Conference for Space Communications which basic limitation of radar is that the returned will convene by early 1971 to make treaty signal decreases by the 4th power of the dis - regulations for frequency allocations. tance. Transponders on aircraft cause jam­ ming because of the poor geometry of ground- Competitive designs will also provide based radar. Satellite-based radar can over­ guidance to the Department of Transportation come these faults. for satisfying air traffic control needs and navigation needs of many users. The previous Fortunately, the technical base for a sys­ DOT administration has already requested the tem which provides a surveillance function for aid of industry to this end. Vigorous design many users has resulted from military and efforts are needed now to prevent a drifting space efforts. Inexorable economic pressures policy detrimental to efficient and safe use of of air transportation will forge an effective national air space. System design is a vehicle union of organizations to use these techniques. for conducting intelligent dialog within the By attempting to forecast .the economic pressure technical community and is a prerequisite to and the most likely technical solutions, the sound budgetary estimates. A complete state­ author hopes to stimulate extensive dialog. ment of system performance (including an im­ plementation plan) can be matched against the HISTORICAL BACKGROUND most critical needs as well as against existing (TECHNOLOGY SEARCHING FOR A NEED) systems that may eventually be retired and proposed systems of limited utility. Many studies have explored the feasibility of using satellites to satisfy specific needs. Designing a system to meet these needs Some studies propose system designs. Their will be an exceedingly complex political, general shortcoming is parochialism. Satellite economic, and technical problem with many communications shows promise at considerable 7-9 expense. By attempting to satisfy limited needs, NASA Has Best Systems Capability but Appears the studies leave doubt that the effort is worth­ to be Withdrawing while. Thus, the characteristic flavor of the recent past has been technology searching for a NASA has conducted experiments and need. studies of wide scope directed towards satellite air traffic control. The Joint Navigation Satel­ However, needs are not lacking. In fact, lite Committee provided comprehensive intra- the air traffic control problem is so big that it governmental guidance towards system design . appears to impede organization by intimidation. However, their limited budget has been directed At last year's annual meeting of the AIAA primarily to the race to the moon. Futhermore, several authorities suggested diverse political Mr. Harper, NASA deputy associate adminis­ organizations that should or can do the system trator for aeronautics has said that system design. New political unions are being explored design should be done by FAA, while NASA should in order to bring the effort to a workable ad­ concentrate on hardware.Recent research fund­ ministrative level. All of these activities are ing cuts on air traffic control research and indicative of the pressures to form union that ATS F and G satellites show that Congress is will implement a useful system. not sympathetic to allowing NASA to take a more active role in air space problems. Even Synoptic Weather Data System Requires rather modest efforts to experiment with the Little Capacity 1540-1660 mHz band have been stopped. Industry has noted that weak fiscal position and is seek­ Many studies have considered imple­ ing opportunities elsewhere. menting a weather data system using satellites. Comparisons with aircraft interrogation An example of the type of system design systems show an economic advantage to satel­ that NASA has sponsored is given in the TRW lite systems. HF radio interrogation suffers NAVSTAR report . It recommends a passive from diurnal variability and irregular perfor­ navigation system coupled with position report­ mance. Buoys designed for long life in the ing by the aircraft back to the controller. The ocean have been under development and testing aircraft provides position computation. Mari­ for over five years. Missing elements appear time users are not excluded. to be a data relay network, a position-fixing capability, and reliable mooring. History shows that NASA is endowed with the management capability to attempt to do new The benefits of long range weather pre­ and difficult things in full view of the nation. diction are really not known in fiscal terms. This contrasts with the philosophy of an operat­ The efforts of DOT to present a substantial ing organization such as FAA which has such case before Congressional committee have immediate difficult operational problems that met questioning indicating that need priority is changes must be evolutionary. The solution to assessed relatively low. Actually, data capacity the air traffic problem is going to require inno­ requirements are so low as to encourage vation. Although several organizations could do waiting to see what may develop in other satel­ the job, only NASA has recently demonstrated lite communications experiments or system this type of gut effort. proposals. RTCA, ARINC,and COMSAT Proposed a System Marine Navigation Users Show Interest of Limited Capability The Navy Navigation Satellite System The combination of the RTCA community, called "Transit" (NNSS) has proven itself ARINC, and COMSAT provides considerable useful for ships and research vehicles as well interest because it puts quantitative numbers as for Navy requirements. Commercial receiv­ on certain needs. These three groups hoped to ers are now available for about $50, 000. This solve the problem of air traffic control over the passive system depends on the doppler shift of oceans as well as to provide administrative a signal from a low altitude polar satellite. communications to aircraft. If FAA had joined Ephemeris data is broadcasted to users. The the union and accepted a limited capability of use of only four satellites at low altitude limits ocean air traffic control (positions reported position updating to every 108 minutes. The use back from the aircraft over the satellite circuit) of low UHF frequencies ultimately limits accu­ funding may have been under way by now. How­ racy to tenths of a mile. The measurement ever, the domestic airlines did not feel that the time is the time for the satellite to pass over capability of VHF satellite communications was the user. that great an improvement over present capa­ bility to warrant picking