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SESSION 1: OPERATIONAL REQUIREMENTS FOR CATHODE-RAY TUBES AND DISPLAYS IN RELATION TO ILLUMINATION PROBLEMS CHAIRMAN Brig. Gen. Victor A. Byrnes, USAF (MC) FACTORS AFFECTING THE DESIGN OF A LIGHTING SYSTEM FOR SAGE R. T. Mitchell, Lincoln Laboratory, Massachusetts Institute of Technology LIGHTING, BUILDING DESIGN, AND HUMAN FACTORS IN SYSTEMS ENGINEERING Samuel A. Francis, Francis Associates OPERATIONAL ASPECTS OF RADAR DISPLAYS USED FOR AIR TRAFFIC CONTROL Robert L. Sorenson and Fred S. McKnight, Technical Development Center, Civil Aeronautics Administration OPERATIONAL REQUIREMENTS FOR ILLUMINATION AND VISIBILITY OF RADAR DISPLAYS IN AIR FORCE RADAR APPROACH CONTROL CENTERS James C. McGuire, Hero Medical Laboratory, Wright Air Development Center OPERATIONAL REQUIREMENTS FOR ILLUMINATION IN COMBAT INFORMATION CENTERS Albert Van Acker, Bureau of Ships, Navy Department SONAR DISPLAYS Matthew Flato, U. S. Naval Research Laboratory -

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Factors Affecting the Design of a Lighting System for SAGE * R. T. MITCHELL, MIT Lincoln Laboratory Summary The visual displays in the semiautomatic ground en- vzronment (SAGE) system provide the basis for monitoring of computers and for making of decisions. The system was designed with objectives of optimum legibility of the displays, illumination sufficient for reading, and area lighting. The paper describes two means for achieving these objectives, one with blue lighting and the other with the use of a bright display and selective location of lamp fixtures and dark paint. The examples illustrate the major conclusion: radar lighting systems should be considered an in- tegral part of the display equipment and the operational system of which that equipment is a part. SAGE, an abbreviation for semiautomatic ground environment, is the name given to the system (now being installed) that will provide tactical control of air battles in defense of the United States. The basic functional unit of this system :_ _~11 _ ~_ _ _ . To ~ ~- ~ ~ ~ A ~ ~ ~ J v -~ ~ ~ ~ calleu a sector. By over-slmplltylng' we may describe the operation of a sector as follows: ( 1 ) Remote radar sites feed data by telephone line to a central location where the data are processed by a computer; and (2) the results of this processing, along with information from other sources, are displayed on cathode-ray tubes' to operators at the central location. The operators use the display nrincinallv to . ~ . r . ~ ~ - r ~ --J r ~ -r ----a - `~on~or brie actions of tne computer and intervene when necessary, and as the basis for decisions to be passed on to weapon sites' airbases, and airborne in- terceptors. The installation housing the computer and operators at the central location is known as a direction c.~?nter It is with the lighting of the r~n~r~ti~rl`: norms r`[ the direction center that we are concerned here. ~^ ~~-^~) ~^ ~ ~^ ~ EVE- AL ~-^~ Vat A few basic aims and methods of approach were agreed upon before the details of the lighting system began to take shape: (1) Knowing that many of the displays would not be easy to read even in an optimum environment, we were determined to avoid anything which would compromise the le~ibilitv of +~ ~:~1 ~ n ~ heir _ 1 ~ ~ v 1 to J LO Ulbpl~y5. Ad) Eve would trv lo net as much light as nos.sibl~ into the rnom.s c, I! _ _ . 1 . ~ ~ . . ~ . . _ ~ . ~ . wllnout con~llctlug With the requirement just stated. Our minimum goal was enough light for personnel to move about freely, and we hope to get enough lo permit reading printed material of inherently high legibility. (3) It was de- cided to attempt an over-all or area lighting approach rather than depend upon localized sources. We believed that the area approach would make it easier to minimize specular Pattern reflec.tion.~ on the? few of the Hicnl~v r~nc~l~c and ~ , ~ ~ ~ ~ ~ ~ ~ _ J ~ ~ ~ _ ~ ^ _ ~ ~ ~ ~ ~ ~ ~ 1_ _ ~ 1 1 1 1 . ~ ~ ~ ~ . ~ ~ ~ . ~ tnat local lighting would tend to result in a large, dark cavern with small, bright pools of light much like the effect in present manual aircraft-control and warning stations. *The research reported in this paper was supported jointly by the Army, Navy, and Air Force under contract with the Massachusetts Institute of Technology.

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There is a widespread impression that there is cone and only one "Lincoln Blue" lighting system for SAGE. Actually, there are three different lighting schemes in use in SAGE operations rooms, and one of them isn't even blue. I am going to describe briefly some of the system requirements which resulted in the two schemes that differ most widely, in order to illustrate the point I want to make here today: namely, radar lighting systems should properly be considered an integral part of the display equipment and the operational system of which that equipment is a part. The optimum lighting system and its components will vary as other display equipment and operational requirements vary. As this dictum is neither original nor very profound, it is a little hard to understand why it is frequently ignored in a field like human engineering where everyone pays homage to "system integration." It is ignored by those who seek to solve their lighting problem by adopting a ready-made lighting system, and it is ignored by those whose enthusiastic praise for their own lighting system begins to make it sound like a universal solution for all radar and sonar displays. Roughly 80 per cent of the display consoles in a direction center are housed in two large rooms. Features to note in these rooms are the large number of consoles, oriented in several different directions. The principal source of data for an operator is the face of a 19-in. cathode- ray tube. This is a rather special tube called a Charactror~. The Charactron dis- plays in two modes. In the first, straight lines are drawn with a focussed beam by standard deflection techniques. In the second, symbols are displayed by directing a defocussed beam at the selected symbol on a small metal stencil in the neck of the tube. The stencil shapes the beam which is deflected to the appro- priate place on the face of the tube. These tubes employ either PI or P14 phos- ~hors which emit a bright. blue light during intensification followed by a rela 1 , ~ , _ _ lively long, yellow afterglow. when 1 salct trial me alSplay~ ala ma ~ ~ ^~ under thel best of conditions, I did not mean to throw rocks at the designers of the Charactron. In many ways it is a remarkable achievement. The resolution, speed of writing, and flexibility are excellent. However, much of the energy available at theicathode is lost by the method of shaping the symbols, and opera- i~onal requirements for large amounts of information result in very brief writing times with a relatively long time interval between reintensifications. The net result is a display whose average brightness is considerably less than one would desire. This dim display is quite sensitive to degradation from two sources: ( 1 ) Light falling on the tube face is reflected by the light-colored phosphor, thus lowering contrast. The scheme we adopted to permit a modest amount of light in these rooms while at the same time shielding the scope from the ambient light was the use of blue filters over daylight fluorescent lamps and a sharp-cut-off yellow filter over the face of the scope. Although we used somewhat different filters, the method is identical in principle with the blue-light~ng system described by Kraft and Fitts.i (2) A serious source of degradation arises from specular re Draft, C. L., and Fitts, P. M. A broad-band-blue lighting system for radar air traffic control centers. Wright Air Development Center, 1954, Technical Report 53-416. 6-

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flections from the surfaces of the cathode-ray tube and its implosion screen. These were minimized by suspending a false ceiling composed of small hexagonal cells below the indirect fluorescent fixtures. These cells transmit light downward into the room, yet, if the cells are small and of low reflectance' their reflection on the scope face appears as a uniform dark surface. I want to emphasize that the selection, placement and installation of these components is not a hit-or-miss affair. The depth of the ceiling cells must be matched to the angle of the tube face. Ceiling and luminaires must be arranged so as to avoid alternating light and dark stripes on the ceiling. The wall paint should match the brightness of the ceiling. The selection of the filters for the lamps and scopes may be a difficult compromise among several factors, and often no single figure-of-merit such as contrast ratio, even if misnamed signal-to-noise ratio, is an adequate criterion for selection. Fig. 1 illustrates the effect of trading signal luminance for increase in contrast by varying the yellow filter on a SAGE Charactron. With a particular blue illuminant, we studied the effect of six yellow filters with varying cut-offs on display legibility. The abscissa refers to the wave- length at which the filters reach 50 per cent transmittance. The points shown as circles show the relative decrease in signal luminance as a function of filter cut-off. The squares show the increase in contrast as the filter transmittance changes to longer wavelengths. The crosses and dotted curve show the change in display legibility. Clearly, signal luminance is of overwhelming importance here as compared with contrast. Over the first five points, luminance has dropped by only 25 per cent while contrast has increased by a factor of 50, yet legibility has declined. So much for blue lighting. 1 1 1 ~ I 1 1 1 1 x- - - LEGI Bl LITY 4.4 C] 04.0 an 9 - J .8 an .7 _ .6 480 . 500 520 540 560 WAVELENGTH (Mp) AT 50% FILTER TRANSMITTANCE o SIGNAL LU M I NANCE ~ ~CONTRAST .~ of, to 1.2 ~ ~_ J 4.0 z c,, 0. 9 - co J 0.8 'A 0.7 l o -4.0 z o by ED -2.5 ~ z -2.0 ~ o Fig. 1. Effect of trading signal luminance for contrast on the legibility of a SAGE Charactron display. In the mapper room, which is another SAGE operations room, quantized radar data from certain remote sites are displayed on tubes which use a PI phos- phor. A head on the arm above the face of the tube contains a photocell which 7 '!

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detects the initial blue flash of the signal and sends it on to the computer for processing. The operator acts as a complex filter to intercept certain unwanted signals, including returns from ~ ~ the ground and from storms. He does this by painting over them with a transparent orange fluid which blocks the blue flash from the phototube. The display is bright and can tolerate a relatively high level of illumination, and the operator uses both the blue and yellow color components of his display to aid in determining which areas he has mapped out. Therefore, no colored filter is used over the scope. The scope face, tipped back at an angle of 70 from vertical, points at the ceiling and would reflect any louvered sub- ceiling. The solution was dark paint on the ceiling and upper walls and fluorescent lamps mounted about 5 It from the floor in reflectors, directed down toward the walls and away from the consoles. The phototube pickup is sensitive to the AC modulation of short-wavelength light produced by white fluorescent lamps. To avoid interference from the room light, standard commercial yellow fluores cent lamps are used. Both the rooms which have been described fall into the broad category of "radar operations rooms," but differing equipment characteristics and operational requirements led to radically different systems of room lighting. Many operations rooms will not differ as greatly in requirements as do these two, but differences will exist. If the unwary customer succumbs to enthusiastic praise for a lighting system developed for one set of conditions, he may be badly disappointed when he applies that system in his own installation. I know of one such instance, and the disappointed customer is now equally enthusiastic in his condemnation of a system which is a perfectly good one under the right conditions. The moral is obvious: we must analyze our requirements carefully and let them guide the design of the lighting system rather than run the risk of divorce later on the grounds of incompatibility. In conclusion, I would like to mention four people who shared in the design of the SAGE lighting system. These are Dr. Bert F. Green of Lincoln Laboratory, William Ayer, formerly of Lincoln, Sam Francis of Francis Associates, and Commander Dean Farnsworth, USNR.

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Lighting, Building Design, and Human Factors in Systems Engineering SAMUEL A. FRANCIS, Francis Associates Summary Considerable effort has been expended on the deveZ- opment of cathode-ray tubes and other visual displays. Optimal operation of visual displays also requires their integration with each other in a complex system and with the design of the lighting and building. Among the examples cited for critical need of co- herent design are the following: need for the architect and en- gineer to familiarize themselves with lighting and layout as af- fected by specialized visual displays; measurements of luminance for blue light; tilt of scope face and the dependent thickness of honeycomb in ceiling; design of a command post with its asso- ciated projection system. Conflicting requirements for illumina- tion place a premium on the skill of the systems engineer in resolving conflicts with minimum compromise. At one time or another, most of us have espoused terms such as systems engineering, weapons systems concept, and many others. To each of us these terms have slightly different meanings. I like to think of them simply as ex- pressions of a desire to view a problem in its entirety and to achieve a complex of machines and men in which each will perform its task in an optimum environ- ment compatible with all components of the system. . . Perhaps the most fascinating area of systems engineering involves the so- callecI "man-machine" relationship. While we all recognize its importance to date, I think it is safe to say that none of us can claim a large weapons system in which this relationship has even approached an optimum. There are as many types of inputs to the human operator as there are senses, and one of the most useful is the visual channel. Substantial effort has been expended on the development of cathode-ray tubes and other displays to provide a modulated light carrier to the operator. It is most unfortunate that virtually all these devices were conceived with little reference to each other. We are now faced with a myriad of display possibilities, few of which are really compatible with the others and none of them completely adequate to supply to the operator either the form or the quantity of information that he is capable . O accepting. So what do we do? Vile take a basic display device, perhaps a cathode-ray tube. It certainly works best in a darkened room. On this we generate symbols of one form or another and tell the operator that this is all he needs to perform the task. But then the "electroniker" comes along and adds an assortment of knobs and dials. These must be identified by visual markings, so he adds a little panel light over them. If his budget isn't too tight, he may even use edge light- ing; it make the unit look more "professional." Not being able to agree with his boss on how bright it should be, he then adds a dimmer control which, in turn, 9

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has to be illuminated. The power-supply people seem to have a mania for gigantic green and red bulls-eyes, although it would seem that some more subtle signal could remind the operator that he hasn't yet turned on the switch. Then there are the plotting boards, the DR tables, and that worst offender of all, the clock. Somehow, the fellow who picks the clock always seems to have lost sight of the real problem so that, with his solution glaring you in the face, you lose sight of several choice targets! Meanwhile, under the direction of a member of the lower echelon in the power group, the building is to be designed. After all, it requires little conceptual thinking. Besides, it is the responsibility of the Corps of Engineers or the Bureau of Yards and Docks. They have both the specialized knowledge and the necessary regulations to deal adequately with the building. Since Congress, by law, must vote public works money building by building and square foot by square foot' the first step is to determine how much floor area is required. With this information in hand' the appropriate service agency obtains what is usually referred to as an A&E, or architect and engineer. Since this is usually done by taking the next name from an appropriate list. the closest to a radar direction center that a selected A & E may have been is his own living room, where he watched the first televised installment of Air Power. Usually, at about this time the equipment is being released for productions so the project office can be fairly sure that the physical dimensions of the equip- ment won't change. Therefore, an 8~/2 x 11-in. sketch is prepared of the desired placement of equipment and forwarded to the unwary A & E. Using the meager information available to him' and augmented by the consuming imagination for which he is famous, the A & E paints the walls and ceiling black, puts theatre lights on the stairs and theatrical pinhole lamps in the ceiling. Some reference to work done at Wright Field and MIT results in a lengthly specification for dipping the lamp bulbs in a special blue paint before use. Long after the A & E has been paid for his plans and specifications, long after the equipment has been delivered to a warehouse to await completion of the buildings, someone decides to rearrange the floor plan. It seems that the senior director won't be able to see the plotting board because a telephone switch- board was binder than anticipated. A cardboard model of the center is made, ~ ~ . . . ~ . ~ 1 ~ 1 1 r . 1 and, to the dismay of all, it Is discovered that only one-na~r tne operators cu see the plotting board. The building contracts have been let so the worl: pro- gresses without any changes. Finally, everything is in place and, after some months of debugging, the system is turned on. Then the real problems begin. The senior director has several administrative duties which require the use of additional light. For this, he brings in a gooseneck lamp from the BOQ. This reflects on one of the scopes and bothers the noncom who is worldling surveillance. The noncom is ordered to make a shield using cardboard and scotch tape. The clock shines in everyone's eyes so it is agreed to turn it off it was so small that no one could read it anyway. And so it goes. 10-

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You have just heard Dr. Mitchell describe to you two of the systems being used in SAGE. Major development work on lighting ceased at Lincoln early in 1955 when it became necessary to release the design for production. However, Francis Associates carried on a somewhat similar approach, first in an existing direction center for the Air Force Cambridge Research Center and then for the Martin Company in the Army Missilemaster System. We had hoped that you might be able to visit the first missilemaster installation, which is in operation in the Washington area, but security restrictions have made this impractical. This lighting system bears a strong outward resemblance to the SAGE blue lighting system described by Dr. Mitchell; however the efficiency of the system is much better, giving us about 4 or 5 blue ft-c. Let me explain the blue footcandle. As you knows the standard luminosity curve adopted by the ICI in 1924 is in error at the blue end. Our basic psycho- physical units of light are therefore quite meaningless under the saturated blue light found in these systems. The situation is so bad that Mr. Kraft's designations of~light level bear no relation whatsoever to Dr. Mitchell' s. This has already caused the airways map service people considerable consternation, since they are called upon to provide maps and other displays to light-level specifications by both groups. rat . ~ ~ We hare, for the time being, accepted a purely arbitrary measure of lumi- nance, which we call a blue-foot-lambert. All our measurements have used a Spectra or~gntness meter for which a correction factor has been determined for each particular illuminant used. This correction factor is the result of a luminance match made by a skilled observer using a Macbeth Illuminometer. Actually, two such matches were made, a cascade match by Dr. Mitchell of MIT and a whole series of direct heterochromatic matches by Dr. Hake at John Hopkins University. Surprisingly good agreement was obtained between the two, although the large scattering in Dr. Hake's data clearly indicates the problems involved in such a measurement. It is quite clear that subjective photometric measurements by any but the most highly skilled scientists are worthless. It might be interesting to note that, compared to SAGE, a factor of fifteen improvement in light level and a significant reduction in cost were made possible In the lVl~ss~lemaster by only two ~actors: (1) The most critical display in the system is a PPI search and tracking console with flicker-free tracking symbols generated during the retrace cycle. For a raw radar display, this one is quite good. This led to the possibility of having somewhat higher levels of light in the room. (2) Of even greater significance, however, was a change in the angle of the scope face from 60 to 70 above the horizontal. SAGE-type lighting systems are extremely critical with respect to display console geometry. If the angle of the scope is increased, the effective path length through the scope filter of the vertically collimated light fluxing down on the console is increased. The longer the path, the lower is the transmittance and the better the contrast. -1 1

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In addition, tile thickness of the honeycomb selected for the ceiling is a function of the angle of reflection from the uppermost portion of the scope face to the operator's eyes. An increase in scope angle allows thinner honeycomb, which passes more light and costs less. Thinner honeycomb also allows a shallower space above it for lights, at a significant saving in building cost, and makes unnecessary the indirect fixtures required for SAGE. Each of these im- provements is cumulative and, like compound interest, the results are quite astounding. It is safe to say that an 800 per cent increase in light and a 45 per cent reduction in cost are directly attributable to the change from 60 to 70 scope-angle. Another area in which a lack of coherent design is frequently seen is in command posts and other rooms where large and conflicting displays are found. In layout of the command post for SAGE, for instance, we were faced with several formidable problems. This is the room where the General and his staff make their command decisions. Essentially, they are concerned with deploy- ment of forces, battle strategy, and so forth. Surveillance, weapons assignment, and intercept direction are all handled at a lower echelon. To perform their task, the commander and his staff have access to detailed information on their scopes but principally use a large display generated by the computer. This pro- jected information is quite fine-grained and can only be seen at a close distance. The criteria established for the display are shown in Table 1. Table 1. Requirements for a Projected Display in a Command Post. Screen width Screen to projector Screen to personnel Maximum plane angle of personnel to farthest corner of screen Maximum vertical angle of personnel to farthest corner of screen Angle between projector line and line perpendicular to screen, horizontal or vertical Number of staff Number of liaison personnel Number of observers Maximum dimensions including across aisles d 2.5-d minimum 3- to 4-d best 1- to 2.25-d range 1.3-d best 60 acceptable 45 desirable 45 acceptable 30 desirable 30 acceptable 20 desirable 0 best 10 6 12 50 x 50 ft The maximum dimensions and number of people were specified, together with requirements for maximum viewing angles. If all the 28 people were midg- ets' the design would have been much simpler. As it was, with all the equipment and with the requirements that everyone be able to see the screen and that each member of the staff be able to see all the others, the assigned room was barely large enough. It was necessary with each design to check and make sure exactly 12

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what could be seen by each occupant of the command post. The central position was given to the ten staff members who are arranged so they can see each other as well as their displays. We were interested in problems of visual communica- tion, not only between a device and the operator, but also between the staff mem- bers themselves. The designer is, of course, faced with mechanical, structural, electronic, and acoustic criteria also, and makes modifications and changes to incorporate and integrate these phases into his design. For instance, he may investigate a 14-in. false floor for electronic wiring and note that the staff's vision to bottom edge of screen becomes critical. He goes on to check the sight lines of each operator. The conclusion of this design work was marked by the construction of a Plexi- glas model of the entire command post. This model was taken to the Pentagon for discussion, and nearly every officer concerned was seen to look through the transparent display screens and note with satisfaction that his namesake in the model could readily see all necessary displays. It took less than two hours to approve the design. A little reflection will show that for the tasks required of the radar operator there may be contradictory illumination requirements. In SAGE, for instance, a dim display puts a premium on maximum transparency of the implosion screen. Any filters applied to the scope are critical. Although not as well defined, there is also a requirement for visibility in the operations center. These requirements are in outright conflict. The success of any solution to such a problem is directly related to the skill of the systems engineer in resolving this conflict with the minimum compromise. Lighting and building design, like equipment design and training, reflects in the ultimate system performance. It requires compre- hension of the problems and imagination and ingenuity in the solutions. 13

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Operational Aspects of Radar Displays Used for Air Traffic Control ROBERT L. SORENSEN and FRED S. McKNIGHT, CAA Technical Development Center Summary Some of the operational problems in using available radar displays are discussed with particular reference to the lighting environment of contemporary air-traffic-control facil- ities. The Technical Development Center of the Civil Aeronautics Administration is interested in methods for improving lighting and display systems' e.g., by a panoramic display<, projection stor- age tubes, rapid film processing & projection systems, and scan- conversion. The paper concludes with a summary of desirable characteristics of radar displays for interim and future use. This paper discusses the use of radar for air traffic control by the Civil Aeronautics Administration (CAA) and some of the operational problems of using available radar displays in the lighting environments of various types of traffic control facilities. It includes a discussion of some of the programs carried on at the CAA Technical Development Center (TDC) to obtain improved radar displays and a brief discussion of interim and longer-range display requirements. Illumination environment for present-day air-traffic-control displays The first use of radar for air traffic control by the CAA was in towers at high-density terminals. Initially, standard PPI-type indicators for surveillance radars were installed in the tower cabs. During the daytime, due to the very high ambient light conditions it was necessary to use a tent over the radar positions. At night, this tent was usually lifted to the ceiling and the sides rolled up so that the radar controllers could communicate more easily with other controllers in the tower cab. The glasshouse construction of tower cabs to permit viewing of the com- plete airport and the surrounding airspace results in very high ambient light conditions. Sunlight may fall directly on equipment in the tower, or it may be reflected from clouds, glass windows, or other bright objects outside or inside the tower itself. Operation of radar indicators within a tent structure in the tower cab is undesirable from many aspects. Space is limited, the tent interferes with the viewing of the surrounding area by other controllers, and heat generated by the equipment requires special air conditioning. Most of the approach control radar positions have been moved downstairs to instrument-flight-rules rooms. Here, standard radar indicators are used in darkened rooms. A small bay of flight progress strips alongside the radar indicator is illuminated by individual small lighting fixtures to provide a low level of illumination for reading these strips or referring to written operating instructions, charts etc. Some experi- mentation has been conducted with monochromatic light sources for general room illumination and with polarizing lights and filters. -14-

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At the top of Fig. 1 may be seen the in-line arrangement of the radar con- troller positions. From right to left are the departure, pickup and identification,, feeder, and two final (PAR) controller positions. The CPN-18 search radar in- dicators and the FPN-16 precision approach radar indicators employ a PI phos- phor. A direction finder (CRD-N UHF/DF) is located on top of the communi- cation console of the pickup and identification controller. Inbound flight strips received from the flight data position are processed to the left from pickup and identification to feeder, to final controller. Outbound flight strips are passed from the flight data position to the departure controller for processing, and are re- turned to the flight data positions for time-stamping and filing when control of the departing aircraft is relinquished by the departure controller. Controllers may desire to keep track of flights by marking on the plastic CRT covers with grease pencil. All controllers will have need to manipulate controls such as focus. intensity, beacon, and range marks on the radar indicator. Such controls must be readily identifiable under the lighting system employed. On the wall behind the row of indicators is a large-scale map showing the control area and various navigational aids. I FSA-4 I FPNd6 FSA-4 FPN-16 CPN 18 FSA-4 CPN 18 FSA-4 CPN 18 FSA-4 ~ Z - L A Z -L P Pl PP I P P I CONE. C - M. COME, Coo 6 C - ~ CONSOLE ~CONSOLE ~O CONSOLE O _ 4_ O CONSOLE o o o o PA R o o o o PA R FEE D E R o o o o PI CK- UP o o o o DER o o o o CONTROLLER CONTROLLER CONTROLLER ASS: C - T - LLERASSET CONTCONT A POSITION CONTROLLER B POSITION ASS T. CONTROLLER Il TRAINING POS'T'ON L I 3 CONTROLLER USA- 4 FL 18 HT OATA CONSO LE L FSA- 4 FLIGHT DATA CONSOLE F SA 4 FL I HT OATA CONSOLE TELE AUTOGRAPH fOR WEATHER IN FORMATS Fig. 1. Diagram of phase I RAPCON showing arrangement of personnel and equipment. The phase 11 RAPCON Now let us look at the more advanced center, the phase II RAPCON (AN/FSQ-20~) which is expected to be operational by 1960. Figure 2 shows the proposed operations room. The arrangement of equipment is different from that of the phase I center, but functionally it is still an in-line system. Because the RAPCON will serve several airfields and utilizes a longer-range search radar than the phase I center, a pattern controller has been added to the system. The direction finder is now a large scale (15-in.) plotting type (AN/USA-3) with a 22

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:~\/, >hi>< Fig. 2. Drawing of the proposed phase 11 RAPCON opera [ions room. P4 phosphor. A display for air defense coordination has been added, but details of the display are not yet available. It will be noted that the final controllers have a search radar display (on short range) to aid them in coordination with the feeder controller, and airport surface detection equipment (ASDE) for checking the status of traffic on the runway es). The ASDE employs a P2 phosphor; the other radar indicators will use the PI phosphor. In Fig. 3 details of the proposed phase II control console are shown. Notice that the console contains two positions and two displays. The assistant controller sits at the right-hand portion of the display, handles primary flight progress data, and monitors the radio contacts of the controller at this station. The design of the console serves to focus attention on some of the major differences between the phase I and the phase II RAPCONS. These differences result primarily from the use of a magnetic drum storage unit to store flight plans and weather infor- mation, use of a new electronic character generation and display unit (similar to the Digitron), and use of tracking gates which permit the association of alpha- numerical symbols with radar-derived target position information. The control- ler's display provides information necessary for decision-making: target position (PPI), identity, and altitude are shown for all aircraft under control. All rave radar targets in the area are also shown. Multiple video mapping equipment permits the presentation on the controller's display of any of a number of maps, obviating the need for large wall displays of this type. At the assistant controller's position, a "mast;" converts the display into the format of the flight progress strip. In Fig. 3, twenty such strips are shown 23

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CONTROLLER Ion T DATA ~ fig. 3. Drawing of the proposed phase 11 RAPCON radar controller's console. On the left half of the screen, and twenty on the right half. The group on the left is for aircraft under control; that on the right is for aircraft pending control. A space is also provided for aircraft pending handover or transfer to the next control position, and for aircraft pending acceptance by this position. At the top of the controller's display is a space for the standard weather sequence. By pressing a button, the assistant controller may obtain weather information from any of the airfields which are served by this RAPCON. In case of radar failure, controllers will use the electronic display of flight data and will operate under ANC (timed) procedures. If the electronic display fails7 flight data may be obtained from the magnetic drum storage unit by means of Flexowriter. A requirement will still exist for a large-scale display shovving the status of facilities, which will be visible to all controllers in the RAPCON. Moreover, maintenance and movement of personnel in the center must also take place. It is apparent that, although illumination requirements are modified to some de- gree in the phase II RAPCON by reason of improved methods for handling flight progress information and some auxiliary information, in general, the same de- mands exist as for the phase I center. An approach to the illumination problem Since 1953, the broad-band-blue lighting system developed by Kraft and Fitts has been in use in the operational Wright-Patterson RAPCON. An improved version has recently been installed in the experimental phase I RAPCON in the same building. Most of the conditions imposed by the operation of the RAPCON are met by the lighting system. Because Mr. Kraft will discuss the system in detail later this afternoon, no further mention will be made of it at this time. 24

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Operational Requirements for Illumination in Combat Information Centers ALBERT VAN ACKER, Navy Department, Bureau of Ships Summary The basic functions of the shipboard combat informa- tion center are the collection, display, evaluation, and dissemina- tion of operational information. Stations to accomplish these functions are described. Lighting requirements vary for detection and tracking positions, supervisory positions, and chart reading and plotting positions. In addition, there are general requirements of the lighting system for casualty repairs and maintenance. The basic purpose of shipboard combat information spaces is the collection, display, evaluation, and dissemination of operational information. Important functions not covered by this definition are action-taking functions, such as control of aircraft and control of missile systems. Most collection of information is done with the aid of radio or cathode-ray tube devices such as radar' sonar, and electronic countermeasures equipment. Most dissemination of Information in the past has been by radio, intercom, or telephone. Automatic data handling systems and closed-loop television are soon to play an important part in this function. Most display of information is by use of grease pencil markings on ecige-lighted clear-plastic status boards and polar plots. Shipboard CICs can be functionally subdivided into the following stations: (1) detection and tracking station containing radar set controls, remote radar displays, and edge-lighted status boards; (2) electronic countermeasures station containing the controls and displays for countermeasures equipment; (3) surface operations area equipped with a dead-reckonin~ tracer radar-set controls CRT displays, edge-lighted display boards, chart tables, and maneuvering boards; (4) display-decision area equipped primarily with a large number of edge-lighted display boards, communications facilities, and some monitoring CRT displays; (5) carrier-controlled-approach area equipped primarily with CRT displays, communications facilities, and some edge-lighted status boards; (6) air opera- tions station, which is primarily a lighted space with display boards and extensive interior and exterior communication. fnc.iliti~.~ (71 air w;arf~r~ Arch ~,inn'?d ~, , 7 \- J ~u--rr-- . ~ ~ ~ .. . . . WltH ~K] displays, edge-l~ghted display boards, communications facilities, and computer panels; (8) weapons control station equipped with CRT and television displays, edge-lighted display boards, and instrument indicator panels; (9) anti- submarine control room equipped with CRT displays and instrument control panels. Aircraft carriers will be equipped with all of these spaces except the last listed, and smaller ships will have those consistent with their assigned missions. In larger ships, these areas are usually separated by bulkheads, some areas often being quite remotely located. In small ships, they will all be found in a single, cramped compartment. Total area involved in older destroyer types is about _25-

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300 sq ft. with a general quarters manning level of about 15 men. In the latest aircraft carriers, the area will go up to about; 3600 sq ft. with a general quarters manning level of about 70 men. So much for the general environment found in a shipboard CIC. Now let us take a look at the different lighting requirerr~ents encountered in these spaces: (1) For detection and tracking posistions. This type of position predominates in the detection and tracking station, air warfare area, CCA area, ECM area, and the weapons control area. In these positions, we must not reduce the de- tectability of weak targets in any way. The lighting system used must not wash out the actual picture on the face of the CRT, must not cause glare or reflections of light sources from the surface of the CRT, must maintain the operator's eye in a state of adaptation which is optimum for detection of weak stimuli, must limit distraction of the operator by nearby activities. In addition the necessary displays and plots must be readily visible. (2) For supervisory positions. This type of position predominates in the display-decision area, is common in the air-operations area and the surface-operations area. In addition, each of the other areas will have one or two such positions. The lighting system used must assist in the exchange of information with other personnel in the area' in the speedy assimilation of displayed information, and in taking the resulting action. The lighting system used must provide illumination of a sufficiently high level to allow normal conversation with adjacent positions, to observe the movements of other personnel, and to allow safe, accurate movement in the space. At the same time the light level must be low enough to make status-board and plotting- board readability good and to permit effective monitoring of CRT type displays. A certain degree of color discrimination is also needed. (3) For chart-reading and plotting positions.- This type of position is found in the air-operations area, the surface-operations area and, to a more limited extent, in the display-decision area and near the ECM area. The lighting system used at these positions must provide a high enough level of illumination to read all markings on a chart easily, and the color composition of the illumination provided must allow all colors to be read and identified. In addition, there are some general requirements. For casualty repairs and for general maintenance, the lighting system must provide a high enough light level to perform the detailed, accurate work required in modern electronic equip- ment, and light of such color composition that the color coding on circuit elements is accurately readable. On small ships as a secondary requirement, it is neces- sary that the light level be low enough and the color composition such as to have the least possible effect on the dark adaptation of personnel entering. As you see, we have complicated and sometimes conflicting requirements for shipboard combat-information-center lighting. Many schemes have been and are being evaluated and used. Some have been scientifically conceived and some just grew from the needs and ingenuity of operating personnel. Some have been mostly good, some have been mostly poor. None has been completely good. As a line officer I have the advantage of posing the problems, pointing out flaws, and looking to men like you for solutions. 26

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Sonar Displays MATTHEW PLATO, U. S. Naval Research Laboratory Summary A comparison of the major features of sonar and radar indicates the importance of the difference between the velocity of sound in water and that of electromagnetic waves in air. This difference results in a much slower information rate for sonar than radar. Usable signals in sonar are a function of parameters such as noise, reverberation gradients, and range. Major transducers for converting an electrical signal into an acoustical one, and vice versa, are the following: searchlight, split-beam, and multi-hydrophore cylindrical array. With the increasing number of components in a system, simplicity of design becomes critical for its reliability. It is well known that sonar was used in World War II to detect enemy sub- marines and to pinpoint them for attack. Sonar continues to be one of our greatest assets in the detection of submarines. The principles of radar are more widely known because of the various applications of radar to aircraft detection' marine and aerial navigation, and even to speed-checks on motorists. It may be informa- tive to compare the features of radar and sonar; Table 1 shows the main quan- titative features of both. Table 1. Comparison of Radar and Sonar (approximate figures only) Item Radar Sonar Frequency up to 10,000 me up to 200 kc Wavelength 3 to 300 cm 0.75 to 15 cm Velocity 186,000 mi/sec 5000 ft/sec Pulse lengths Microseconds Milliseconds to seconds Radar utilizes electromagnetic waves in air, while underwater echo-ranging systems use pressure or acoustic waves. Electromagnetic waves cannot be prop- agated any appreciable distance in water; in contrast, acoustic waves suffer relatively little loss. Frequencies and time scales in both cases are very different. Most underwater acoustic systems operate from audio frequencies up to 200 kc, as compared with frequencies up to 10,000 me in radar. The velocity of sound in water is about one mi per see, whereas the velocity of electromagnetic waves in air is 186,000 mi per sec. It is this velocity difference which accounts for the fact that the information rate of sonar is much slower than that of radar. Sonar pulse durations are of the order of milliseconds, as compared with the microsecond durations in radar. The wavelengths of sonar and radar are rather similar in their respective mediums, so their radiating and reception devices are com- parable in physical size. The term echo ranging is used to describe the process of sending out energy pulses at a rate which allows the pulse to traverse the distance to the target and return. Energy reflected from the target and returned to the source is considered - 27

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to be the signal. Many parameters, such as noise, reverberation gradients, and range, have to be accounted for in order to obtain useful signal levels. These will be discussed briefly. In echo ranging, background noise limits only the longer ranges. In general, the echo must be detected against a background of reverberation. As a masking background, reverberations differ from noise in several ways. Reverberation concentrates around a definite frequency, whereas the spectrum of noise com- prises a very wide range of frequencies. The level of reverberation depends on the power output of the projector and decreases very rapidly with range. Echoes are usually tones of a definite pitch that are not likely to be confused with noise, except where very short ping lengths are used. The occasional strong bursts of reverberation, however, may be easily mistaken for echoes. . The surface layers of the ocean are subjected to heating, cooling, and mix- ~ng; moreover, they may flow at a speed different from that of the underlying water. The four processes are closely related, but each has its own characteristic effect on the temperature gradients that are revealed by bathythermograms. The immediate effect of each is to alter the dynamic state of the surface layers. The bathythermograph measures the temperature of the sea as a function of depth. Although temperature gradients affect propagation the most, velocity of sound is altered also by pressure due to depth and salinity. The Doppler effect is very important in sonar echo ranging since it aids in distinguishing a weak echo in a reverberation background. By listening closely, an observer may determine the motion of the target. The change of frequency due to target motion in the direction of the acoustic beam is about 0.65 cycles per knot per kc. Range is an important factor in obtaining a usable signal level. Sound waves would spread spherically if the ocean were uniform and infinite in all directions. Since the ocean is not infinite, but is bounded by the bottom and surface, spherical spreading applies for a distance of about 1,000 yds. The sound waves tend to be channeled after 1,000 yds, and the spreading loss is reduced in half. This is called cylindrical spreading. There is an additional loss in range due to absorption. This loss is expressed in db per kilo-yd of range. The absorption loss is greatest at high frequencies, and decreases as the frequency decreases. Some targets return better echoes than others. Reflections are dependent on the size, shape, surface, and density of the target. A large, metallic target with an irregular shape usually reflects a large amount of signal. It might be well to discuss the directivity of transducers, since the displays of sonar are visual presentations of what is in the ensonified area of the trans- ducer. The transducer for converting the electrical signal into an acoustical one, and vice versa, may be regarded as a loudspeaker and microphone, respectively. It generally relies on either the magnetostrictive or the piezoelectric effect for . . its operation. 28

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E~_~ if= E, ~ S E ~ R C H L I G H T LAG A N E SPLIT- BEA M tr ' LU x ~[}0 c} {} 0/ {} OCR for page 4
direction perpendicular to that of the stylus traversal. When returns are receiver from a target on a number of successive traces, the line produced on the paper by target signals becomes more and more detectable as successive returns grow in length. Range rate can be determined by measuring the opening or closing angle of the traces. TARGET T R A N S D U C E R S ~ / 1 ~! \,\ Fig. 2. Bearing deviation indicator. With the split-beam transducer, a display called the bearing deviation in- dicator was devised. This was the first display to give some indication of target location in the sound field. Rotation or steering can be performed either by physically rotating the transducer or by the use of delay lines. HYDROPHONES / / \ / ~150 REV/SEC 1 ~O~ 1 \O O/ Fig. 3. Plan position indicator. 30 ~) /

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An example of beam forming and scanning equipment follows. Multi- hydrophones are constructed on the periphery of the cylindrical transducer. All the signals from 48 preamplifiers for each hydrophore of the transducer are amplified by individual preamplifiers and delivered to both the video and audio scanning switches. The scanning switch is a device whereby several consecutive transducer signals may be selected and combined to form an acoustic beam. The video scanning switch, rotating continuously at 3,000 rpm, produces signal pulses whenever its acoustic beam sweeps past an echo signal and delivers this voltage to the video channel of the receiver, a conventional superheterodyne circuit whose rectified output supplies brightening signals to the grids of the cathode-ray tube. The beam deflection is synchronized with the video scanning switch so that this brightening will occur at the correct bearing. Approximate range is displayed by causing the deflection to increase at an appropriate rate with respect to time, thus producing a slowly expanding sweep. The audio scanning switch, which can be positioned by the training control, receives echoes along a particular bearing and delivers these signals to the audio channel of the receiver, a conventional superheterodyne circuit with a beat- frequency oscillator for producing audio notes from echo signals. The output of this channel operates a loudspeaker and a range recorder for accurate determina . ~ lion ot target range. To track many enemy submarines over millions of square miles of ocean requires super sonars which are indeed a far cry from those with which our ships were equipped in World War II. The need still exists for sonar displays which can cover large ocean areas and store previously received information. We may conclude with a word of caution in regard to sophisticated displays. As the number of parts in a system increases, the probability of failure of the system also increases. Simplicity of design should be stressed. New techniques discussed at this meeting may be used in the development of future displays and in the improvement of present displays. 31

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