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(-39 

EyE 

cy 

TWONDER Mathematical 

Description 

12 September 1968 

Prepared under 

Contract No. 

Submitted to 

Space and Missile Systems Organization 

SAFSL-7B 

Air Force Systems Command 

In addition to the security requirements which 

apply to this document and must be met, it may 

be further distributed by the holder only with 

the specific prior approval of SAFSL-7B. 

OCT 28 1968 

HANDLE VIA BYEMAN 

CONTROL SYSTEM ONLY 
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lEORETI D 

ACKNOWLEDGEMENT 

The TWONDER program, described in this document, was developed 

through the combined effort of the following individuals: 

Members of the Technical Staff 

L. E. Adkins 

S. Birnbaum 

S. Blum 

D. D. Dingwall 

A. K. Fitzsimmons 

E. M. Friedman 

R. E. George 

A. W. Luetje 

T. R. Markham 

D. D. Morrison 

B. A. Robinson 

J. A. Trageser 

Technical Support 

F. Nielson 

Secretarial Support 

C. Roberts 
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CONTENTS 

1. INTRODUCTION 

2. TWONDER CAPABILITIES 

2.1 General Discussion 

2.2 TWONDER Subfunctions 

7 2.3 TWONDER Capabilities and Restrictions 

3. TWONDER SUBFUNCTIONS 

Page 

1 

3 

3 

16 

28 

35 

3.1 TWONDER2 35 

3.2 TWOPIN 47 

3.3 TWPATW 51 

3.4 TDMERGE 103 

3.5 TWACQPR 111 

3.6 TWOPS 121 

3.7 TWEEDOFF 157 

3.8 TWMOSP 173 

3.9 TWMOSP2 211 

3.10 TWASCON 215 

3.11 TWASSP2 257 

3.12 TWOUT 321 

3.13 TWPLOT1 347 

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1. INTRODUCTION 

This TWONDER Mathematical Description documents the features, capabilities, and computational methods of the TWONDER study program. The information contained in this document is intended to supplement the TWONDER User's 

Manual (Reference 1) by providing an understanding of the computational 

methods employed by the program. In this sense, the document can be used 

as an aid in conducting studies related to: 

• Determining the capabilities of the MOL/DORIAN system 

• Design of the operational Mission Planning Software (MPS) 

Section 2 of this document describes the features and capabilities of 

TWONDER. Section 3 gives a detailed description of the program including 

computational methods and flow charts. Operating instructions and usage 

instructions may be obtained from Reference 1. 

The version of the TWONDER program currently being used and for which 

the documentation is applicable is found on the SOFT 11-05N flight support 

tape. This is SAMSO tape 755 and contains the following programs: 

1. DIRCTY DIRECTORY 

2. DUMPL B65CA 

3. LTAB P41AA 

4. SIPHON R69AA 

5. STTOMT G8ORB aft 

6. TANGVEL P16DA 

7. TBCD Q33WH 

8. TCOIN SO3EC 

9. TDETAIL Q34AL 

10. TDISPLAY A76AN 

11. TDMERGE PO8EG 

12. TEPHSPAN PO6EA 

13. TIRCOS P12DA 

14. TITANIC Q30ER 

15. TNTERP P10EA 

16. TOVER P11DA 

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17. TSIGMA P17D0 

18. TSTACOR P15DA 

19. TSTAVEC P14DA 

20. TWACQPR UlOAQ 

21. TWASCON U08BL 

22. TWASSP1 U32AD 

23. TWASSP2 U32AR 

24. TWEEDOFF U04AP 

25. TWLIST U09AC 

26. TWMOSP U11BN 

27. TWMOSP2 U12AS 

28. TWONDER U16AA 

29. TWONDER2 U09AI 

30. TWOPIN U01AH 

31. TWOPS UO2A0 

32. TWOUT U13AY 

33. TWPATW UO3AI 

34. TWPLOT1 U3OAS 

Numbers 1 through 5 are SDC programs. TBCD and TDETAIL are not applicable 

to TWONDER and are on the tape in order that TDISPLAY will be operative. 

TWASSP1 is a table generating program that was used in TWONDER checkout, 

and TWLIST is a table listing routine. All other programs have specific 

TWONDER functions. 

The TWONDER program is compatible with the BESST 11 series of system 

support tapes and requires certain octal correctors found in the SOFT 11-05N 

convenience deck. It is planned to build a new flight support tape incorporating all of the convenience deck octals. This documentation will also 

be applicable to the new flight support tape. 
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2. TWONDER CAPABILITIES 

2.1 GENERAL DISCUSSION 

The purpose of the MOL/DORIAN Mission Planning Software (MPS) is the 

generation of an optimum target acquisition strategy for the main optics 

and the two acquisition telescopes. The TWONDER study program has been 

developed to provide a means of evaluating the capabilities of the MOL/ 

DORIAN photographic reconnaissance system during the development phase of 

the system. In addition, the program TWONDER provides a tool that will be 

used to facilitate development of the target selection algorithms for the 

operational Mission Planning Software. 

An important feature in the overall design of the TWONDER target 

selection procedures is the progressive reduction in size and improvement 

in organization of the initial target list on the basis of preliminary 

information and using fast computational methods. This reformatting, compression, and reordering of the original target list is begun by the subfunctions TWPATW and TDMERGE and continued by the subfunctions TWOPS, 

TWEEDOFF, and TWASCON. It is only when the target list has been significantly reduced that the highly accurate analytic procedures and precise 

selection logic within TWONDER are exercised. 

The targeting problem can be viewed in terms of three fundamental 

processing requirements which are (1) the organization and compression of 

the master target list into the time ordered set of visible targets, (2) 

the generation of optical system pointing information which defines the 

opportunities for main optics photography and ATS viewing, and (3) the 

selection of an optimum strategy for the main optics and ATS. 

Because it is not necessary to perform the above step (1) with extreme 

accuracy so long as no visible targets are erroneously rejected, the compression and time ordering function is performed using tailored approximate 

trajectory equations, which greatly reduce computational times while 

sacrificing very little accuracy. Step (2), the generation of optical 

system pointing parameters, is the only step of the three that would be 

absolutely essential provided the input list of targets was limited to a 

relatively few widely spaced targets. These computations relate individual 

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SECRET/D 

point targets to the orbiting photographic system to produce the parameters 

that describe how and when each target can be observed. Step (3), the 

selection of an optimum strategy, introduces the concept of conflict between 

the competing targets. Conflicts are identified by considering the vehicle's 

maneuvering capability and the pointing requirements of the various target 

acquisitions. Optimal sequences for the main optics and acquisition telescopes are generated by applying optimization algorithms to the set of 

possible acquisitions. 

An introductory discussion of these three fundamental requirements is 

provided in the following sections. Section 2.1.1 provides a discussion of 

the swath sorting and time ordering performed by TWPATW and TDMERGE. These 

subfunctions are described in detail in Sections 3.3 and 3.4. The basic 

optical system pointing parameters determined by the subfunction TWOPS are 

described in Section 2.1.2. A detailed description of TWOPS is provided 

in Section 3.6. Section 2.1.3 provides a brief mathematical introduction 

to the optimization techniques employed by TWMOSP and TWASSP2. The subfunctions are described in detail in Sections 3.8 and 3.11. 

2.1.1 Orbital Considerations Related to the Swath Sorting of Targets 

Two obviously important properties of a reconnaissance orbit are (1) 

the pattern with which it acquires point targets and (2) the photographic 

conditions that will apply at the time a particular target is viewed. If 

for the moment the earth is assumed not to rotate about its poles, the set 

of visible targets will be confined to a narrow visibility belt underneath 

the orbit, as illustrated by the shaded area of Figure 2-1. 

Assuming that the sun was positioned directly out from the page (in 

the same relative position to the figure as the reader), then it will always 

be daytime for those points on the near side of the earth and nighttime for 

those points on the back side. Moreover, it will be noontime at point B, 

and earlier or later than noon for points between A and C only so much as 

the plane of the orbit carries the vehicle to the west or east of the sun/ 

earth line. If the orbiting vehicle moves in the direction ABC, then the 

opportunities for daylight photography will occur when the vehicle is moving 

in the north to south direction. 
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N 

EQUATOR 

Figure 2-1. Photographic Reconnaissance Orbit Schematic 

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These depicted relationships will be established by a southwesterly 

launch from VTS resulting in an orbit having retrograde motion, if liftoff 

occurs near 12 noon (i.e., the time at which VTS coincides with point B). 

If, in addition, perigee is established in the vicinity of point B, it will 

be possible to photograph the great majority of targets (visible as they 

shift through the doubly shaded region) at relatively low altitudes 85 

miles) while maintaining apogee altitudes (one-half rev removed from point 

B) consistent with operationally suitable orbit periods and lifetimes. 

The effect of the earth's rotation is to shift new targets into the 

shaded visibility band between consecutive revolutions of the vehicle. 

Near earth orbits have periods of approximately ninety minutes from which 

it follows that the earth makes a complete revolution approximately every 

16 revolutions. By suitable choice of orbital period, the coverage pattern 

can be tailored to give repeated coverage of specified areas or to provide 

uniform coverage on the basis of this daily cycle. Complete coverage, 

except in the region near the equator, can be achieved after 5 days of 

operation. During the same 5-day period, areas nearer the top of the orbit 

will be covered redundantly on consecutive days and in some cases on consecutive revs. These observations follow from consideration of the visibility swath width 140 miles near perigee) and the decrease in rotational 

effects as a function of increasing latitude. 

The described set of first order orbital characteristics can be 

exploited to compress and organize the master target list. This function 

is carried out by the TWONDER subfunctions TWPATW and TDMERGE, which first 

select the set of visible targets over a specified rev span (eliminating 

approximately four-fifths of the total set of targets for a 1-day run) and 

then time order these targets according to their computed acquisition times. 

The visibility criteria can be calibrated and qualifying targets subjected 

to additional constraints according to certain File 7 input parameters 

(SEVXXX). SEV003 specifies the absolute value of obliquity that is to apply 

to target acquisitions. This value must take into account anticipated 

errors in crosstrack distance over the prediction interval. The obliquity 

pad over and above the actual obliquity limits of the system can be made 

comfortably large since the associated penalty, which is the qualification 

of some additional targets, is negligible. SEV004 specifies the minimum 

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sun elevation angle that must apply at a target for qualification. This 

parameter is also related to the visibility requirement. SEV007 and SEV008 

specify the maximum slant range to the target and maximum vehicle altitude, 

respectively. These latter parameters can be used to establish a minimum 

resolution criterion for individual target acquisitions. 

2.1.2 Pointing Parameters 

The opportunities for main optics photography and ATS viewing are 

determined by the subfunction TWOPS. Both systems are capable of continuously tracking individual point targets, and it is therefore required that 

the target/vehicle orientation be defined over the duration of target visibility. The target orientation at any time is defined by stereo angle (E) 

and obliquity (c) as illustrated in Figure 2-2. 

The acquisition time and acquisition obliquity are determined for each 

target at three stereo angles defined by the File 7 input parameters SEV063, 

SEV064, and SEV065. These parameters are the main optics maximum forward 

stereo angle, vertical acquisition stereo angle, and maximum aft stereo 

angle. 

To a first approximation, both stereo angle and obliquity can be considered to be linear functions of time. This approximation is employed by 

the target selection algorithms to define the pointing parameters E and Si 

over the interval of target visibility. In terms of the time at which a 

given stereo angle is achieved, the maximum error contributed by this 

approximation is about 1 second. This linear assumption has led to the 

derivation of the conflict parameter (Q), which is discussed in Section 3.8. 

2.1.3 Analytical Basis of the Target Selection Algorithms 

2.1.3.1 Purpose of this Discussion 

The purpose of this discussion is to present, in a simplified form, a 

mathematical discussion of the target selection problem. This discussion 

is limited to the consideration of a discrete time-ordered problem in which 

a single strategy is determined. The main optics algorithm, TWMOSP, is an 

extension of the basic algorithm that considers continuous variable and 

nontime ordering. The detailed description of this algorithm is provided 
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C- R E D 

TARGET 

Figure 2-2. Target/Vehicle Orientation 
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in Section 3.8. The ATS algorithm, TWASSP2, requires the simultaneous 

optimization of the strategies for the two acquisition telescopes. This 

algorithm is described in Section 3.11. 

2.1.3.2 Statement of the Problem 

The target selection problem is to determine, out of all possible 

sequences, which sequence of nonconflicting targets maximizes the total 

target score over some prespecified vehicle orbit span. 

To facilitate a clearer presentation of the basic mathematical ideas 

underlying the selection algorithm, certain simplifying assumptions will 

now be introduced. It is assumed that: 

a. The vehicle is capable of only a single (e.g. vertical) 

stereo direction sighting. 

b. Obliquity slewing rate is constant. 

c. A single prespecified or precomputed value is available 

for the worth of each target acquisition. 

Conflicting targets must, of course, exist or the problem is trivial. 

2.1.3.3 Solution of the Problem — Analytic Aspects 

Figure 2-3 depicts a particular target distribution. Targets T1,T2,...

, 

T

6 could be photographed by the vehicle (disregarding conflicts) when the 

vehicle is, respectively, at positions P1, P2, ..., P6 along its orbit if 

the mirror were slewed to, respectively, obliquities R1, R2, ..., R6. In 

fact, however, slewing the mirror requires time. Assuming a constant slewing rate, there may be associated with each target "limit" lines (dashed 

lines in the figure) which define the region in the vehicle visibility 

swath that could not be photographed assuming the target in question is 

also photographed. 

In the figure, both T5 and T6 are in conflict with T2, T3, and T4. 

There are no other conflicts. For brevity, it might be written 

T

5 c T2, T3, T

4 

T

6 c T2, T3, T

4 

T

1 4 T2, T3, T4, T5, 

T

6 

R /D 

r. 
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A, o 

Figure 2-3. Example Six Target Distribution with Conflicts 

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letting the symbol c represent conflict and the symbol 4 represent no 

conflict. 

Refer to an arbitrary sequence of nonconflicting targets as an admissible policy, and the total score associated with that policy will be 

referred to as the return from following that policy. A policy which maximizes the return will be called an optimal policy. In general, an optimal 

policy will not be unique, but the maximum return or maximum score produced 

by following an optimal policy must, by definition, be unique. 

Inasmuch as a policy, by the above definition, contains no conflicting 

targets, first mathematically characterize the state of conflict/no conflict 

among the various targets. This may be done quite succinctly with the use 

of a target conflict matrix. \\ 

Thus envision a (square) conflict matrix, C, with elements c.. such 

that 

C . . = 

1J 

0, if Ti T. 

1, if T. c T. 1 

By definition, ckk = 1, that is to say, any target is in conflict with 

itself. The motivation for this will become apparent later. 

ItisclenrdlatifT.1 cT.,then T. c Ti, i.e., C is symmetric. It 

may be concluded that the elements to the right of the main diagonal along 

with the diagonal itself contain all the essential information in the 

conflict matrix. 

The conflict matrix associated with the target distribution indicated 

in Figure 2-3 is shown in Figure 2-4. 

Assume that the targets have been chronologically ordered so that Tl 

is the first target to be encountered and possibly photographed, T2 is the 

second, and so on to TN, which is the last target to be encountered in a 

particular span. 

Instead of attempting to directly determine the optimal policy starting before the first target is encountered through to the last target, 

the optimal policy starting before the first target through to some 

general target will be determined. Clearly, when this problem has been 

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j i T1 T

2 T3 T

4 T

5 T6 

T1 1 0 0 0 0 0 

T

2 1 0 0 1 1 

T

3 1 0 1 1 

T

4 1 1 1 

T

5 1 0 

T

6 1 

S. 

J 

1 2 3 4 2 3 

i. 

J 

0 1 2 3 1 5 

s

maxj 1 2 3 4 4 4 

Figure 2-4. Example Six Target Conflict Matrix with Scoring 

• 

U 

4-4 

0 

OD 

0 

U 
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solved for all targets, one will have the solution to the particular problem 

of starting before the first target and ending after the last target. 

For analysis purposes, define the following function. 

S. the score obtained from the sequence of targets 

whichendsTainTi,takingTiJ , and otherwise 

following an optimal (score maximizing) photographic policy 

Further, let w. be the worth of a photograph of T.. Finally, define 

the set of targets I, with elements i, such that 

a.i < j, i.e., 1 isencountered previous to T. 

b. c.. = 0, i.e., Ti is not in conflict with T. 

It is clear that the set I is, in general, a function of j, the particular target in question. In particular, the number of elements of I is a 

monotone nondecreasing function of j. Roughly speaking, the number of 

elements of I will be somewhat smaller than the numerical value of j because 

SOME earlier T. are in conflict with T.. 1 

Now develop a simple equation which the function S. must satisfy. It 

will be a recursive equation to evaluate, sequentially, S. for all j. 

BreakupSintotwoparts:thatscoreorreturn from taking T., and 

the previously accrued score or return just before reaching T.. The worth 

ofT.ispreciselyw..Immediately preceding the taking of T., some other 

admissible predecessor target, Ti, was taken. Disregarding for the 

moment just how this can be ensured, it should be clear that if Ti were 

taken, then it should have done so via a maximum return policy from 

the start up to and including Ti. Now by definition, the maximum score 

obtainable from the start up to and including Ti with Ti taken is Si. 

Inasmuch as w, is independent of the predecessor target, it remains simply 

3 

to choose that particular predecessor target, Ti, out of the admissible 

predecessor set I, which maximizes Si. Mathematically, 

S. = w. + max Si 

i c I 
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As with any optimization problem, two items or quantities are of 

interest. First, there is the thing which is extremized — in this case, 

maximized. It has been denoted as S

j 

 . Secondly, there is the thing (independent variable) which, if set to the right value, causes the return to be 

extremized. The variable in this problem is the optimal predecessor target 

associated with each target. We might call this i . 

2.1.3.4 Solution to the Problem - Computational Aspects 

The above simple equation can be used in the following manner. 

The computation is initialized at T1 and is precisely S1 = wl. There 

is no predecessor associated with the first target. Next T2 is considered. 

If T1 c T2, then this is so reflected in the conflict matrix by c12 = 1. 

In this case, I would be an empty set and S2 = w2. If T1 4 T2, then c12 = 

0, and S2 = w2 + S1. 

The situation becomes interesting, but by no means complicated in 

general from the third target on. Thus for T3, S

3 equals w3 plus the 

maximum of Si, where i < 3 and ci3 = 0. In similar fashion, one evaluates 

S sequentially until j = N, the last target to be considered. This procedure is easily followed, especially on a digital computer, because the 

procedure involves a strictly repetitious operation, and, for any particular 

j, all S,, i < j will have been already evaluated. 

As the procedure is followed for each target T., it is necessary to 

* J 

recordonlySandi..To determine the optimal policy through the target 

distribution, one then starts at the end of the list and examines the S. 

until the largest is found. This largest value may not necessarily occur 

at j = N, the physically last target, but it will be near the end. The 

largest S. will be the maximum possible return or score and T. will be 

the last target to be photographed in the optimal sequence. Also, that 

target has its particular ij which is the index of the immediate predecessor 

to T. in the optimal sequence. In this fashion, one reconstructs the 

optimal sequence of targets to be photographed, albeit in a reversed time 

ordering. 

The computational procedure will be illustrated with the six-target 

example of Figures 2-3 and 2-4. It becomes convenient, in performing hand 

calculations, to append three additional rows to the conflict matrix which 

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* 

contain, for each target, the vectors S., ij, and Smax j, the latter being 

J 

equal to max Sic The purpose of the last row will be indicated later. 

It is observed at present that S

m

ax j S

j for all j. 

For simplicity, assume that w. = 1 for all j. Evaluate S4, the maximum score obtainable from the start up to and taking T4. From the conflict 

matrix it can be seen that for j = 4, T1, T2, and T3 E I. Therefore, from 

the equation, 

which is to say, 

that is, 

S

4 = 1 + max (1, 2, 3), 

S

4 = 1 + 3, 

S

4 = 4. 

Further, it has been found that 

i = 3 

that is, in any optimal sequence, which includes T4, the predecessor to T4 

should be T3. 

In practice, one need not generate and store in a computer memory the 

whole of the conflict matrix before starting to perform the target selection. If memory space is limited, it may just as well determine whether or 

not a conflict exists between two targets T. and T., i.e., determine the 

value of cij, when considering selecting Ti as the predecessor to T.. 

The purpose of the row headed Smax j will now be indicated. According 

to the recursive equation, when evaluating any S., consider, as a predecessor 

target Ti, all i E I, i.e., all i such that i < j and cij = 0. For large 

numerical values of j, I will become a sizable set to be tested. This is 

clearly an undesirable situation. Further, it is clear that testing over 

alliinIisunnecessarysincetheoptimalpredecessori-will in general 

be relatively near j. The function of Smax j is to allow the search back 

on i to be terminated as soon as possible. 

Thus,inpractice,inevaluatinganyS.,only those i c I need to be 

considered which further belong to the subset of I, say I', which starts 

with the closest admissible i to j and ranges to that i such that 

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S.=Smax i 

for the first time working backward with decreasing i. It can 

1 

be shown that the subset I' will always include the optimal predecessor, 

i., for any T.. 

In the example defined by Figures 2-3 and 2-4, the actual amount of 

search back on i for any j is shown in Table 2-1. 

Table 2-1. Actual Search on i for any j 

Set I Includes Set I' Includes 

1 empty empty 

2 i = 1 i = 1 

3 2, 1 2 

4 3, 2, 1 3 

5 1 1 

6 5, 1 5, 1 

While the above table indicates some savings in the amount of searching to be done, it should be clear that the savings increases greatly with 

a large target list. Roughly speaking, the number of elements in the set 

I increases linearly with j, while the number of elements in the set I' 

remains essentially constant and will include only a relatively small 

number of possible nonconflicting predecessor targets immediately preceding 

T.. 

3 

2.2 TWONDER SUBFUNCTIONS 

The program TWONDER is composed of a series of subfunctions that are 

called sequentially to perform the required computations. The interrelationship between these subfunctions is illustrated in the functional flow chart 

provided in Figure 2-5. A brief description of each of the successor 

functions called by TWONDER is given below. 

2.2.1 TWOPIN 

The function TWOPIN initializes all input data for TWONDER. It reads 

Files 1, 2, 7, and 8 of the reset tape and generates a table of constants 

and reference parameters. The reset parameters are stored in the tables 

THINGS and ALSO. These tables provide the primary means of communication 

between the TWONDER subfunctions. TWOPIN also reads all controlling 

ET/D 
1 

TWONDER2 

Control the calling of 

all successor functions 

Call TWOPIN 

Read function cards, data 

cards, and reset tape. 

Check ephemeris 

1 

Call TWPATW 

Determine rev assignment 

and acquisition time. Delete 

targets based on input limits 

TDMERGE 

Time order target acquisitions and generate ACQ tape 

TWONDER 

Call driver TWONDER2 

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TWONDER TWONDER 

( ENTER ) 

Figure 2-5. TWONDER Functional Flow Chart 
ACQ tape desired? 

lir Yes 

TWACQPR 

Print the ACQ tape 

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-MET/0 

TWONDER TWONDER 

Is a print of the No 

K

Is ACQ plot output 

desired? 

Yes 

V 

TWPLOT1 

Make a time-obliquity 

plot of the targets 

on the ACQ tape 

Call TWOPS 

Compute pointing data 

and basic worth of all 

target acquisitions 

Is a print of 

the COTPRIME 

tape desired? 

No 

Yes 

TWACQPR 

Print the COTPRIME tape 

Figure 2-5. TWONDER Functional Flow Chart (Continued) 

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TWONDER TWONDER 

Call TWEEDOFF 

Condense pointing data 

and prepare input for 

TWMOSP 

Call TWMOSP 

Select optimum set of 

nonconflicting target 

mode combinations for 

main optics viewing 

Call TWMOSP2 

Reconstruct the optimal 

sequence of main optics 

targets 

4, 

) 

Is acquisition scope No 

selection required? 

4

, Yes 

Call TWASCON 

Condense payload data 

and prepare input for 

TWASSP2 

Figure 2-5. TWONDER Functional Flow Chart (Continued) 

-MEN 
• 

TWOUT 

Generate Tape 8 and/or 

online output 

/ 

Is selection plot 

output desired? 

Yes 

plot of the targets 

on the ACQ tape 

with superimposed 

Main Optics and ATS 

selection 

Has last rev of 

rev span been 

processed? 

Yes 

TWASSP2 

Select optimum set of 

nonconflicting targets 

for viewing with 

acquisition scopes 

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TWONDER TWONDER 

Figure 2-5. TWONDER Functional Flow Chart (Continued) 
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parameters on the TWONDER function card and reads all data cards. The 

following types of data cards can be input: LAT, TIM, LIM, target add (A), 

target change (C), target delete (D). It also checks the rev span on the 

input DDI ephemeris tape to ensure that sufficient ephemeris coverage exists 

over the requested rev span. 

2.2.2 TWPATW 

TWPATW accepts data from the target tape and stored ephemeris data produced by the DDI general purpose tracking program and computes approximate 

target acquisition times. To increase computing speed, approximate analytic 

expressions are used for these computations. All targets that are impossible 

to photograph are eliminated. However, a conservative approach to target 

elimination is used, which ensures that targets that may become available 

for photography, through possible subsequent minor orbit variations, are 

retained. 

Initially, the average sun vector is computed, and the vehicle analytic 

ephemeris is constructed (from the input ephemeris) for the rev span of 

interest. Also computed initially are the limiting latitudes for target 

acquisition. The latitude limits are based on sun angle and orbit inclination constraints. 

Subsequently, the target entries are read from the target tape into the 

target buffers. The target card entries are decoded one at a time and 

operated upon serially until the entire target record has been decoded and 

processed, and the acquired target data stored in the acquisition buffers. 

In the serial mode of processing employed by TWPATW, each target has 

its acquisition opportunities evaluated for the entire rev span during its 

processing turn. Target acquisition processing is initiated by checking the 

target latitude against the limits computed initially and making an initial 

estimate of earliest time of target acquisition. The initial estimate of 

acquisition time is refined in an iteration that determines the vertical 

acquisition time for each acquisition opportunity on the rev span. 

For all targets acquired, computations are made for sun elevation 

angle, obliquity angle, slant range, and vehicle altitude. These parameters 

are checked against the input limits for each parameter, and for each target 

that is not deleted, the target latitude and acquisition time are checked 

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against any existing latitude and/or time band deletions. For all valid 

target acquisitions, the data for the acquired targets are stored in the 

buffer area for output and subsequently on the intermediate acquisition 

tape preliminary to time sorting. 

Options are provided that allow TWPATW to perform its operations in 

four different modes. These options are summarized as follows: 

a. Construct. A target tape and DDI ephemeris data are 

used to generate an acquisition tape. This is the 

basic operating mode for TWPATW. 

b. Construct with ALTER Cards. A target tape is used 

together with alter cards (add and/or change and/or 

delete) to produce an acquisition tape. 

c. Ephemeris Update. Existing acquisition tape data 

are updated to provide new acquisition times and 

acquisition parameters as a function of new or 

modified ephemeris base data. 

d. Ephemeris Update with ALTER Cards. Existing acquisition tape target data are revised to reflect 

possible ephemeris change as well as revisions 

specified by entries on ALTER target cards. 

2.2.3 TDMERGE 

After TWPATW has processed the target list and the target and acquisition data for all acquired targets has been written on intermediate tapes, 

TDMERGE sorts the targets and writes the final acquisition tape. TDMERGE 

reads the entries from the intermediate acquisition tapes into core storage buffer space. The targets are time ordered in core and a single target 

acquisition tape is written. The target data contained on the acquisition 

tape includes the full set of target card parameters. Also entered in the 

data block are the target acquisition parameters which are computed by 

TWPATW: 

a. Time of acquisition 

b. The difference between earliest acquisition time 

and vertical acquisition time 

c. Parameters at vertical acquisition 

▪ 

Obliquity angle 

e Altitude 

a 

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A 

• Slant range 

• Sun elevation angle 

2.2.4 TWACQPR 

The subfunction TWACQPR reads either target acquisition records from 

the acquisition tape or COTPRIME records from the COTPRIME tape, depending 

upon the options requested and the calling sequence. The data are interpreted and reformatted for the listable output. The output is ordered by 

rev number and by vertical acquisition time within each rev. A detailed 

description of the acquisition table is provided in Section 3.5 

2.2.5 TWPLOT1 

The subfunction TWPLOT1 provides a display of the target data available 

on the acquisition tape in the form of a swath plot. On option, both the 

main optics and ATS selection strategies are indicated on the swath plot. 

The following information is available on the swath plot for each of 

the targets on the acquisition tape. 

• Target I.D. 

• First significant digit of target inactive priority 

• Earliest acquisition time 

• Vertical acquisition time 

• Obliquity 

In addition, the selection strategy option provides the following: 

• Scheduled scope dwell time 

• ATS path number 

• Flag at I.D. scheduled for ATS viewing 

• Group decision time 

• Group number 

• Scheduled main optics tracking time 

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• Time during which photography actually 

takes place 

• Flag at• I.D. scheduled for photography 

A detailed description of this output is provided in Section 3.13. 

2.2.6 TWOPS 

The function TWOPS reads the acquisition tape, computes precise pointing data and the basic weights (active and inactive) for each target, and 

generates the COTPRIME tape, which then provides the basic source of target 

information for the successor functions of TWONDER. The pointing information is calculated by an iterative procedure. The acquisition times available on the acquisition tape were determined by approximate methods in 

TWPATW using an analytic ephemeris. These times are used as a first approximation, and the precise acquisition times are then determined for each 

target based on the input DDI ephemeris. The pointing information available 

for each target consists of acquisition time and acquisition obliquity for 

each of three input stereo angles. These stereo angles correspond to main 

optics maximum forward stereo angle, vertical acquisition (stereo angle = 0), 

and main optics maximum aft stereo angle. The active and inactive weight 

of each target is determined as a function of priority and an obliquity 

deweighting factor of the form cosh (obliquity), where n is a File 8 input. 

Apart from the various geometrical constraints, the subfunction TWOPS 

provides the first of a series of target density filters, which selectively 

eliminate from further consideration and computation targets of such low 

worth as would not affect the ultimate main optics and ATS strategies. 

Two File 8 parameters control the sensitivity of this filter. 

2.2.7 TWEEDOFF 

The function TWEEDOFF acts as a preprocessor for the main optics 

algorithm (TWMOSP). The basic functions performed by TWEEDOFF are: 

• Abstraction of the information required by 

the main optics algorithm (TWMOSP) from the 

COTPRIME. This information is tabulated in 

the MOCOT. 

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• Provision of a means of limiting the number of 

targets that must be considered by TWMOSP. This 

is accomplished through the use of either a priority filter or a priority/target density filter. 

These filters can be used to study the tradeoff 

between program running time and total score. 

• Determination of the number of targets that are in 

partial conflict with each of the targets to be 

considered by TWMOSP. Only those targets that are 

in close time proximity require a detailed conflict 

analysis. Targets that are further removed in time 

are either in complete conflict or have no possible 

conflict. The earliest and latest targets that 

must be considered for partial conflict are determined by TWEEDOFF for each of the targets in the 

MOCOT. This information is utilized by TWMOSP to 

reduce the number of conflict calculations. 

• Computation of the basic weight of each target to 

be considered by TWMOSP as either its inactive or 

its expected worth, depending upon a File 8 input 

parameter. 

2.2.8 TWMOSP 

The main optics algorithm TWMOSP selects the best score set of nonconflicting photographic sequences. The effective worth of an individual 

photographic sequence is based on active target priority, inactive target 

priority, probability of activity, photographic mode, an obliquity deweighting function, and a pitch deweighting function. 

In TWMOSP, the best score set of predecessors is determined for each 

of the targets available in the MOCOT. This information is tabulated in 

the ALMOST table, and the job of reconstructing the optimal path is delegated to the successor function TWMOSP2. 

2.2.9 TWMOSP2 

The function TWMOSP2 abstracts the optimal sequence from the ALMOST 

table and outputs the Main Optics Strategy Table (MOST), which contains 

the selected main optics photographic sequence. The ALMOST table contains 

the set of all optimal sequences down to and including every target under 

consideration. The sequence that attains the maximum score is then the 

overall optimum. TWMOSP2 scans the ALMOST table to find the target that 

completes the largest score sequence. The predecessor information is then 

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utilized to trace this sequence and to determine which targets are contained 

on the optimal sequence. The acquisition time and photographic mode are 

also determined for each of these targets. The target identifier, acquisition time, and photographic mode are then tabulated in the MOST. 

2.2.10 TWASCON 

The function TWASCON is utilized as a preprocessor for the acquisition 

scope algorithm (TWASSP2). The basic inputs to TWASCON are the COTPRIME 

tape and the MOST. TWASCON contains a series of filters of three general 

types. These are: 

a. Target type filters 

b. Geometry filter 

c. Group density filter 

The type filters can be used to selectively delete from consideration 

targets of the following type by the ATS algorithm: 

• Visual intelligence targets 

• Main optics selected targets 

• Indicator targets 

• Nonindicator targets 

• Low worth targets 

The geometry filter is utilized to reduce the set of candidate ATS 

targets. Based on acquisition scope viewing time requirements and prior 

main optics commitments, a set of geometric constraints is determined. 

Each target is then tested against the constraints and is deleted from 

further consideration if it is found that there is insufficient time to 

view the target through the acquisition scope, slew the main optics, and 

then photograph the target while satisfying the TWONDER ground rule that an 

alternate target must be compatible with the preceding and following primary. 

The group density filter operates on all the candidate ATS targets 

surviving the previous two filters. The group filter eliminates from further consideration all but the N highest worth targets in any group, where 

N is a File 8 input parameter. 
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For those targets that remain after the above filters are applied, 

entries are made in the ASCOT table, which provide the target specific 

information required by the ATS algorithm, TWASSP2. 

2.2.11 TWASSP2 

TWASSP2 is employed to determine the optimal acquisition scope strategy 

when either one or two scopes are to be utilized. A single path is determined when NUMSCOP = 1 and two paths are determined when NUMSCOP = 2 where 

NUMSCOP is a File 8 input parameter. The worth of an individual target 

is based on active priority, inactive priority, probability of activity, 

probability of visibility, probability of falsely reporting a target to 

be active or inactive, and obliquity deweighting. The targets to be 

considered are obtained from the ASCOT, and the best score sequence down 

to and including each target is determined. 

In addition, the optimal decision time is determined for each target 

group. A target group consists of a single primary (or main optics) target 

plus a number of alternate targets. Both the primary and the selected 

alternates are to be viewed through the acquisition scopes, and the status 

of each target (active, inactive, cloudy, or mandatory override) reported 

to the onboard computer prior to decision time. A voting logic is then 

employed to determine which target should be photographed by the main 

optics. In order to ensure that any of the selected alternates can be 

photographed, a decision time must be selected that is compatible with 

the entire group. This group decision time is optimized by the algorithm 

through the use of an imbedding technique, in which multiple entries are 

made,•when necessary, to allow for the possibility of variations in 

decision time. 

As is the case in the main optics algorithm, a list is generated that 

contains the optimal sequences down to and including each of the targets 

being considered. The best score path is determined by first scanning the 

list to find the target that completes the maximum score sequence and then 

using the predecessor information to determine which targets are contained 

in the sequence. The output of TWASSP2 is the Acquisition Scope Strategy 

Table (ASST), which provides the optimal acquisition scope target sequence. 
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2.2.12 TWOUT 

The subfunction TWOUT is the basic output routine for TWONDER. The 

inputs to this routine are the COTPRIME, the MOST, and the ASST. The 

following basic types of output are available for listing: 

• Main Optics Strategy 

• Acquisition and Tracking Scope Strategy 

• Results of expected score calculations by group 

• Rev summaries of the above three items 

The output format is described in Section 3.12. 

2.3 TWONDER CAPABILITIES AND RESTRICTIONS 

The TWONDER program provides a wide range of capability through the 

use of program inputs as described in the TWONDER User's Manual (Reference 

1). The program can optionally be run in several different modes depending 

on the particular study requirements. The purpose of this section is to 

provide an insight into the tradeoffs in running time and optimality associated with these modes of operation. In addition, there are certain 

restrictions to program usage that are inherent in the design of the program. These basic restrictions are also discussed in this section. 

The TWONDER subfunctions TWMOSP and TWASSP2 are used to determine the 

optimal selection of targets for the main optics and for the ATS. The 

running time required by these subfunctions is strongly effected by the 

number of targets considered. The following plots (Figure 2-6) show 

running time and number of targets as a function of the density filter 

setting controlled by EGT936 and EGT937. 
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TWMOSP Run

ningTime, Minutes 

30- 

20- 

10- 

0 

0 1 3 

Target Density, targets/sec 

30- 

0 

26 

• n ma

E--4 

w 

25 - 

o 4-) 

• a) 

w 

w 

• 

CIn 

z 

20 

0 1 2 3 

Target Density, targets/sec 

Figure 2-6. TWMOSP Running Time and Number of Targets Selected 

as a Function of Target Density 
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20 

10- 

0 s 1 ■ 

0 1 2 3 

Target Density, targets/sec 

110- 

130- 

70- 

90- 

50 s ( 

0 1 2 3 

Target Density, targets/sec 

Figure 2-6. TWASSP2 Running Time and Number of Targets Selected 

as a Function of Target Density (Continued) 
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These figures show a significant decrease in running time with target 

density. However, the number of targets selected remains relatively constant. More importantly, the score obtained was found to vary by less than 

1 part in 100. The data shown in the above plots are taken from a particular run in which 940 candidate targets were available after swath sorting 

by TWPATW. The number of targets available for selection varied from 110 

targets, with the density filter set to pass 1/4 target/second, to 487 targets, with the density filter set at 3 targets/second. Because of the problems of long running time and because high target densities can cause a degradation in selection, the recommended maximum target density is 2 targets/ 

second. This density can be obtained with EGT936 = 8 and EGT937 = 4.0. 

TWONDER capabilities and restrictions related to swath sorting 

(TWPATW and TDMERGE), main optics selection (TWMOSP), and ATS selection 

(TWASSP2) are provided in the following three sections. A summary of program restrictions is given in Section 2.2.4. 

2.3.1 TWPATW and TDMERGE 

The swath sorting routines are limited to 11,200 acquisitions on a 

single run. With a target deck containing 15,000 targets, approximately 

one-fifth or 3000 will be acquired during a period of 1 day. Therefore, a 

rev span covering approximately 3-1/2 days would be the longest duration 

that could be considered in a single run using this target deck. 

As described in the User's Manual (Reference 1), a stack option is 

provided so that an acquisition tape containing longer rev spans can be 

produced. 

2.3.2 TWMOSP 

Three optimization options are available for computing the main optics 

selection in TWMOSP. These are interleaving, interleaving inhibit, and 

time order. These options are discussed in Section 3.8. Both the interleaving and interleaving inhibit options utilize nontime-ordered algorithms. 

The interleaving option allows interleaving of the ABA type to occur while 

the inhibit option does not. The time-ordered algorithm does not allow any 

interleaving, but of course pays the penalty of yielding a less optimal 

selection than a nontime-ordered algorithm. The degree to which the selection is degraded is a function of target distribution and the types of 

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weighting functions employed. A comparison of the running times of these 

three options indicates that the time-order option is the fastest. The 

interleave option takes approximately three times as long, and the inhibit 

option has a running time of about six times as long. It has also been 

found that these factors tend to increase with target density. 

It has also been observed that TWMOSP running time is approximately 

inversely proportional to photo sequence time. 

The worth of a photograph of a particular target is a function of the 

mid-sequence stereo angle. Relative worth is provided as a function of 

stereo angle through the use of pitch weighting function as described in 

the User's Manual (Reference 1). The pitch angle weighting factor is 

determined from File 8 input curves. These curves are described as a function of the five parameters W, RS1, RS2, El, and E2 as indicated in 

Figure 2-7 where: 

W is an angle defining the area in which cp(T) = 1 

(measured in degrees) 

RS1 is the reciprocal slope of this line segment 

(measured in degrees) 

RS2 is the reciprocal slope of this line segment 

(measured in degrees) 

El is the height of this horizontal segment (nondimensional) 

E2 is the height of this horizontal segment (nondimensional) 

c is the desired central stereo angle (this is 

indicated on the target card) 

Various shapes for the pitch weighting function can be obtained. However, 

certain limitations have been observed during program operation. The 

allowable settings are: 

W > 0 

RS1 > 0 

RS2 < 0 

El 0 0 

E2 0 0 
[41.1? -14-1141 

RS2 

0 

-30 +40 

•■• 0111■••• dIMI■ MONO Mg= 

RS1 

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These restrictions are imposed to eliminate discontinuities and zero-worth 

targets. 

Discontinuities would be encountered if RS1 or RS2 were set equal to 

zero. This presents a dilemma in determining the score at the point of 

discontinuities. This problem is easily avoided by disallowing the discontinuity. 

By setting El or E2 to zero, regions could be defined in which photography is worth nothing. However, the selection algorithm searches for a 

best score set of targets and, as currently formulated, will consider the 

inclusion of zero-worth items so long as nothing better can be done during 

a particular time period. To eliminate the selection of targets during a 

time period when photography is "worthless," the parameters El and E2 should 

be made negative (-1.0). The algorithm then has a clear advantage in not 

taking a target in a "worthless" region. 

• 

Stereo Angle (deg) 

Figure 2-7. Pitch Weighting Function, 4 

2.3.3 TWASSP2 

Two filters are available to control the alternate target selection 

performed in TWASSP2. These are EGT908, the maximum number of targets/ 

group considered in the selection process, and EGT940, the maximum number 

of list entries that may be generated for a particular pair of targets with 

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a particular decision time. Both of these parameters control the size of 

the list generated by TWASSP2. This list contains the set of allowable 

predecessor pairs available at significant acquisition times and compatible 

with allowable group decision times. The core storage available to contain 

this list limits the number of predecessor possibilities that can be considered. The recommended maximum settings for the filter parameters are 

EGT908 = 8 targets/group and EGT940 = 15 list entries. Running time has 

been found to decrease significantly with the magnitude of these parameters. 

In addition, the target selection has been found to be relatively 

independent of EGT940. Further study is being performed to better define 

the running time and selection tradeoffs associated with these parameters. 

2.3.4 TWONDER Restrictions Summary 

The basic program restrictions are related to the number of targets 

that can be handled and to allowable target density. These limitations are 

• Maximum of 11,200 acquired targets per single run 

of the swath sorting programs 

• Maximum of 4,000 acquired targets per rev 

• Maximum target density of 2 targets/second considered 

in the selection process 

• Maximum of 8 targets per group considered by TWASSP2 

• Maximum of 15 list entries per target pair at a given 

decision time considered by TWASSP2 

In addition, the definition of the pitch weighting function should not allow 

discontinuities or zero-worth photographic sequences to occur. 

The above limitations have been discussed in previous sections with the 

exception of the 4000 target/rev restriction. This restriction is imposed 

by the subfunction TWEEDOFF. This subfunction employs a table containing 

the acquisition times of all targets on a rev. This table is limited to 

4000 entries. Since present target distributions yield a maximum of 

approximately 1000 targets/rev, this limitation is not serious. In addition, 

density filtering is performed prior to TWEEDOFF and could be used to control the number of targets considered by this subfunction. 
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3. TWONDER SUBFUNCTIONS 

3.1 TWONDER2 

3.1.1 Purpose 

TWONDER2 is a short generalized control program that loads and executes 

TWONDER subfunctions in the order necessary to accomplish a given TWONDER 

run. This function performs no computations and is entirely concerned with 

sequencing and controlling the modules that perform the TWONDER task. 

Figure 2-5 is a flow chart which illustrates the steps performed 

during a TWONDER run. Figure 3-1, the TWONDER2 flow chart, shows the 

method used to obtain this sequence. 

The functions to be executed and the order of execution are determined 

by the content of the data table CALLS described in Section 3.1.2. This 

table contains the names of the TWONDER subfunctions. The order of the subfunctions determines the order of execution. Subfunctions in the table are 

identified as belonging to one or more of the following categories: 

a. Initialization of input data 

b. Rev span processing 

c. Single rev processing 

d. Unrequired subfunction (for a particular run) 

3.1.2 Input 

The File 8 input parameters used by TWONDER2 and located in table 

THINGS are shown in Table 3-1. Where the input source is a Function Card 

parameter, the mnemonic defined in the TWONDER User's Manual (Reference 1) 

is given. The Function Card input parameters are depicted in Table 3-2. 
01 

REVLOOP 

NN = 0 

Initialize function table counter 

Load and excute current 

function entry 

RTJ CALL 

01 

ENDLOOP 

Advance counter 

NN = NN+1 

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TWONDER2 TWONDER2 

TWONDER2 

Set flag for initialization Pass 

FIRST = 1 

CALLOOP 

Skip current function entry if blank Yes 

If FUNAME (NN) EQ 8H ( ) 

(

Skip current function 

entry if not flagged for 

execution? 

If DOF (NN) NQ FIRST 

Yes 

No 

Clear core area from 

loading address to 600008 

(

Have all function entries 

in table been processed? 21D 

41. Yes 

C) C

Figure 3-1. TWONDER2 Flow Chart 

--STORELVD 
( 

 Are there more revs to 

process? 

IF REV (0) L Q 

REND (0) 

Yes 

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TWONDER2 TWONDER2 

INITIAL 

Was last pass through 

function table initialization Yes 

pass? 

IF FIRST EQ 1 

SPAN 

Was last pass through function 

table the span pass? Yes 

IF FIRST EQ 2 

Advance Rev. No. 

REV(0) = REV(0)+1 

V 

No 

( RETURN ) 

Figure 3-1. TWONDER2 Flow Chart (Continued) 

SECRET/D 
Turn off COTP table output 

request flag (for span pass 

only) 

BIT(36) (OUTFLG(0)) = 0 

If NUMSCOP(0) NQ 0 DOF(A) = 0 

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TWONDER2 TWONDER2 

Flag functions that are 

not required for run 

Is COTP table output 

requested? 

If BIT (36) 

(OUTFLG(0)) EQ 1 

Set TWACQPR rev pass 

entry flag for no loading 

or execution 

DOF(A) = 0 

Is ATS selection 

requested ? 

Set TWASCON and TWASSP2 

entry flags for no loading 

or execution 

Initialize for span pass 

Set pass flag for span pass 

FIRST = 2 

Figure 3-1. TWONDER2 Flow Chart (Continued) 
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TWONDER2 TWONDER2 

Initialize for first 

rev pass 

Set pass flag for rev 

pass 

FIRST = 3 

Turn off ACQ table print 

flag (for rev passes only) 

BIT(34) (OUTFLG(0)) = 0 

Figure 3-1. TWONDER2 Flow Chart (Continued) 
H 

tti to 

O 4-1 

$4 

0) 0 

4-) 

0 

0 

0 

.4"1 -1 H •r-I 

O .1-1 

1-) 4-i 

(1) 

O 

• 

0 

}. _0 

4-1 

CD V. 

O En H 

C/) 

4.1 

H 

0 

al CD 

O 0 

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0 

z 

0 0 cr5 

44 A 

C 

O 

(1.5 H 4-1 

9-1 CO 0 

Gr. C.) 

0 0 rl Definition 

Inte

rface Table Usage Reset FileDefinition 

Table 3-1. File 8 Parameters Used in TWONDER2 Located in Ta

ble THINGS 

BIF-4—B10009-68 __SEGRETiD -

Page 40 

0 0 

C 0 

CO CO 

-..1 -.1- 

H 

.1- 01 

cr) 

)-1 cr) .,-i c.1 

E-1 C..7 

0 

,-3 r.4 

E-1 

'73 

•-0 "C$ 0 

td C 0 0 

CCI CCI 

Cl) Cl) 

)4-I 0 0 r-I 

• 

H 

O 04 .0 

•H }-I 0 4i .4i C ai 

O 0 

0 a 0 El E

H 4.. 0 0 

o H td 0 

3-i a) ..—.4) 0 0 4.1 4.) .t..) -0 5 a) o co 0 cd 0 

O ...... 0 ,—i -,-1 H A A 

O QJ ,..0 4-) (11 4.) 

U -0 W 0 b0 c..1 P. C..1 0) C all 

0 C U C 0 Cli cd (1) Cd C.) 0 .1-) 4.) 

H 0 cli 4- H H E-4 HI -,-1 0 C 

H N-1 0 cl.) CO 

0 4-1 cs) 0 co 0 -0 1:5 

t-1 (-) '. 4-1 H 0 0 (1) (L5 

0-1 0 ..-. Li..4 1-5 4 CO 0 cL) 

ei 4..) c1:1 

W o) (L) (.0 54 0 X E--I 

b0 4-5 al) 4-1 0) (15 a) •ri Hi HI E-40 H 

O -0 H G 54 0 $4 0 4-5 P. 4-5 H cn cr) to C.,) to 

5.4 54 H 0 al ,--ICH OLTI 00cilH HMO 

O 0 P4 al H 0. H fa. I--1 H H 0 <4 1-1 1-1 <4 Z 

4-i cf) 

to 

cn (1) •• •• •• •• •• 

OD C) 0 H c\I -4- H cNI -.1- CO s.C) C.4 .-.1' CO ■.0 

co .0 cs4 Lil 

H 0 

H 

H cs1 

F.. C1') 

,t; 

0 

C`4 

1-1 

0 -Zr 

H cn 

H H 

H E-I 

0 0 

W 41 A 
BIF-4-B10009

-68 

Page 41 

Table 3-1. File 8 Parameters Used in TWONDER2 Located in Table THINGS (Continued) 

Interface Table Usage Reset File Definition 

H 

to H 

0 0 

0 

cs) c0 

H (NI u-1 0 0 r-i cs4 COTPRIME 

Output requests are 

H 

at 0 

• 4-) 

a) 0 

4.) 

H 

0 •r4 4-1 

H 4-1 

o •t-4 ■-) 14-1 

a) 

cd H 

• 0 

}-1 LI )g, 

• cO 

H 

ri 

0 a) 

0 0 

O ›, z 

O 0 

O 0 4-4 

0 

44 Pi 

0 

a) 

•,-4 4) 

00 cd 

r4 W 0 

a) 

0 a) a) 

U 

• 

0 0 

u) 

u) 

W 0 

. 

O II a) 

(..) 0. 

• H 

o 

44 ^ 

O 0 0 

)4 0 

a) 0 4-) 

0 II II 

Z 0 c's1 

0 

CV 

H 

0 

0 

cr% H 0 

fx) 

O 

Definition 

c0 o 

▪ k.0 

H ul 

P.4 

0 

En 

_SECRET/ D 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 D 

Page 42 

Table 3-2. Function Card Parameters Used in TWONDER2 

Function Card 

Parameter 

Symbol JOVIAL 

Declaration Definition 

REV'END 

REV'START 

REND 

RSTART 

I 48 U 242 0 

I 48 U 245 0 

Last rev to be processed 

First rev to be processed 

Table CALLS contains all information necessary for TWONDER2 to load 

and execute the TWONDER subfunctions in the proper order; it is a rigid 

table in parallel format containing 15 entries of 3 words each. The item 

definition for the CALLS table is provided in Table 3-3. 

Table 3-3. Table CALLS Item Definition 

Symbol JOVIAL 

Declaration Definition 

FUNAME H 8 0 0 Function name 

CALL'OPT* I 48 U 1 0 Q register parameter word required 

for successor call 

RETURN'TO** B 1 0 1 = return to calling program 

0 = return to system 

N3'GIVEN* B 1 3 1 = load at address N3 

0 = load at CLANK 

SAVECALL B 1 6 1 = save calling sequence 

0 = do not save calling sequence 

N3 I 15 U 2 33 Specified loading address for 

successor call 

DOF I 2 U 2 23 Pass Flag 

0 = never execute or load 

1 = initialization pass entry 

2 = span pass entry 

3 = rev pass entry 

All CALL'OPT entries are set to 0 except for bits 0, 3, and 6. 

** 

All RETURN'TO and N3'GIVEN entries are set to 1. 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 -MET/ D BIF-4-B10009-68 

Page 43 

The preset contents of the table are shown in Table 3-4. The order of the 

entries in table CALLS determines the order in which TWONDER2 loads and 

executes TWONDER subfunctions. The pass flag (DOF) determines on which of 

3 passes a particular function should be executed. Initialization functions 

(DOF = 1) are executed first, then rev span functions (DOF = 2), and, finally, 

single rev functions (DOF = 3). A function can be entered in table CALLS 

as many times as required for proper run execution. Both TWACQPR and 

TPLOT1 have two entries since these functions must be executed during both 

the span pass and the single rev pass. 

Table 3-4. Preset Values in Table CALLS 

Entry Number FUNAME SAVECALL N3(Octal) DOF 

0 TWOPIN 1 14000 1 

1 TWPATW 0 13000 2 

2 TDMERGE 0 13000 2 

3 TWACQPR 0 13000 2 

4 TWPLOT1 0 13000 2 

5 TWOPS 0 13000 3 

6 TWACQPR 0 13000 3 

7 TWEEDOFF 0 13000 3 

8 TWMOSP 0 13000 3 

9 TWMOSP2 0 13000 3 

10 TWASCON 0 13000 3 

1,4 

11 TWASSP2 0 13000 3 

12 TWOUT 0 13000 3 

13 TWPLOT1 0 13000 3 

14 (Blank) 0 13000 3 

3.1.3 Output 

No output is provided by TWONDER2. 

3.1.4 Method 

TWONDER2 remains in core during the operation of TWONDER. This 

function loads and executes all TWONDER programs. The process has three 

phases: initialization, rev span processing, and single rev processing. 

-Slaw D 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 44 

--SEDRET/ D 

The required subfunction names, loading addresses, pass flag settings, 

and loading control information are contained in table CALLS. 

a. Initialization Pass 

The program checks through the table CALLS and then 

loads and executes all functions flagged as initialization functions (pass flag = 1). The only entry 

so flagged is TWOPIN. 

b. Option Checks 

After the initialization pass is complete, the 

program checks the value of NUMSCOP (EGT900) to 

determine if Acquisition Telescope (ATS) processing 

has been requested. If NUMSCOP = 0 (no ATS requested) the program sets the pass flags for TWASCON 

(ATS target selection algorithm preprocessor) and 

TWASSP2 (ATS target selection algorithm) in table 

CALLS to zero. Setting of the pass flags suppresses 

loading and execution of these functions. 

c. Rev Span Pass 

The pass flag is initially set to 2 to indicate 

that a span pass is being performed. Bit 36 of 

OUTFLG is set to zero since COTPRIME output is not 

applicable during a span pass. All subfunctions in 

table CALLS that have a pass flag of 2 are loaded 

and executed in order. The subfunctions process 

the entire requested rev span. The applicable subfunctions are: 

1. TWPATW (generate target acquisitions) 

2. TDMERGE (sort target acquisitions) 

3. TWACQPR (display target acquisitions) 

4. TWPLOT1 (provide swath plot of target 

acquisitions) 

d. Single Rev Processing 

The pass flag is set to 3 to indicate rev by rev 

processing. Initially, the current rev (REV) is 

set equal to the first rev of the rev span (RSTART). 

All subfunctions in the table CALLS that have a 

pass flag of 3 are then loaded and executed in order. 

These subfunctions are: 
SECRET/0 NRO APPROVED FOR 

RELEASE 1 JULY 2015 BIF-4-B10009-68 

Page 45 

F. 

1. TWOPS (generate COTPRIME) 

2. TWACQPR (display COTPRIME) 

3. TWEEDOFF (main optics target selection 

algorithm preprocessor) 

4. TWMOSP (main optics target selection 

algorithm) 

5. TWMOSP2 (generate main optics selection) 

6. TWASCON (ATS target selection algorithm 

preprocessor) 

7. TWASSP2 (ATS target selection algorithm) 

8. TWOUT (display selection results) 

9. TWPLOT1 (plot selection results) 

If the current rev is equal to the last rev in the span being processed, 

TWONDER2 exits to the system. 

If additional revs must be processed, the rev counter is incremented 

by 1 and the above subfunctions are again executed. 

(REVERSE OF THIS PAGE LEFT BLANK) 
4-EC-REVD NRO APPROVED FOR 

RELEASE 1 JULY 2015 BIF-4-B10009-68 

Page 47 

3.2 TWOPIN 

3.2.1 Purpose 

TWOPIN reads the reset tape, the control parameters from the TWONDER 

function card and the data cards. TWOPIN also checks the DDI ephemeris tape 

to ensure enough data is available to permit processing of the requested rev 

span. 

3.2.2 Input 

1. Reset tape, containing all File 7 and File 8 parameters as 

presented in the User's Manual for TWONDER (Reference 1). 

2. LAT cards, LIM cards, TIM cards and target add, change and 

delete cards. 

3. TWONDER function card 

3.2.3 Output 

TWOPIN stores various parameters in the THINGS and ALSO tables for use 

by subsequent subfunctions. TWOPIN outputs the target add tape, the target 

deletion tape, the target change tape and the LAT and TIM deletion tape. 

3.2.4 Method 

TWOPIN reads Files 1, 3, 7, and 8 of the reset tape and stores the 

appropriate parameters in the THINGS and ALSO tables. These values are the 

constants, reference parameters and flag settings that form the basis for 

the computation and logic flow of the particular run being executed. 

TWOPIN reads the control parameters on the TWONDER function card and 

determines the rev span and output requests. Also determined is the form 

of the input tape (an acquisition tape or a target tape). TWOPIN reads the 

data cards, i.e., LAT cards, LIM cards, TIM cards and target add, change and 

delete cards. The TWOPIN flow chart is shown in Figure 3-2. 

SECRET/D 
) 

Read FILE 7 

and FILE 8 

CONST 

Set up standard 

and RIPOOL constants 

RESET 

TWOPIN 

PATFUN 

Pick up function 

card values for 

TWPATW 

NRO APPROVED FOR 

RELEASE 1 JULY 2015 

81F-4-B10009-68 

Page 48 

-SECIE11 - D 

TWOPIN TWOPIN 

Figure 3-2. TWOPIN Flow Chart 

II 
--SENETID NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 49 

TWOPIN TWOPIN 

MOPIN2 

INTERNAL DRIVER) 

MOPIN27 

Transfer FILE 7 

data to individual 

cells 

MOPIN8 

Establish buffer sizes, 

make tape unit assignments, and transfer 

FILE 8 data to individual 

cells 

MOPIN27C 

Compute parameters 

from FILE 7 values 

V 

MOPINF2 

Read ephemeris, write new 

ephemeris record, write a 

zero record, and an end-offile 

Figure 3-2. TWOPIN Flow Chart (Continued) 

SECRET/D 

• L 

V 
) 

i 

V 

(

Are any 

cards input? 

Yes 

V 

MOPCARDS 

Read data cards, 

e.g. ALTER, LAT, 

LIM, etc. 

V 

ACDCARDS 

Read ADD, CHANGE, 

and DELETE cards, if 

any, and write tapes 

to represent these 

cards 

Make bit 

checks for 

on-line output 

TEPHSPAN 

Read ephemeris tape, 

check for correct rev 

span, set-up ephemeris 

data, and print messages 

SECRET/D 

TWOPIN 

i 

( RETURN ) 

Figure 3-2. TWOPIN Flow Chart (Continued) 

---S-EVEVD 

NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 50 

TWOPIN 
SECRET/D NRO APPROVED FOR 

RELEASE 1 JULY 2015 BIF-4-B10009-68 

Page 51 

tr. 

3.3 TWPATW 

3.3.1 Purpose 

Subfunction TWPATW controls all phases of target acquisition processing and the generation of acquisition information for the purpose of 

preparing the intermediate target acquisition tapes, which are processed 

by subfunction TDMERGE. 

3.3.2 Input 

The inputs required by TWPATW are as follows: 

a. Target tape or acquisition tape. 

b. Ephemeris data 

c. THINGS table. 

The acquisition tape is described as an output of TWPATW in Section 3.3.3. 

The target tape, ephemeris data and the THINGS table items required by 

TWPATW are described below. 

3.3.2.1 Target Tape 

The target tape is serial in structure. Each entry corresponds to a 

unique target. The parameters contained within each entry on the target 

tape are described in Table 3-5. 

3.3.2.2 Acquisitions Tape 

The acquisitions tape is described in Section 3.3.3. 

3.3.2.3 Ephemeris Data 

The data from table DEPHDA of the ephemeris tape that are required 

for each event time which begins an orbit interval are described in Table 

3-6. 

The data from table DEPHID of the ephemeris tape that are required 

are described in Table 3-7. 

Orbit adjust data from table DOADJ of the ephemeris tape which are 

required are described in Table 3-8. 
Definition 

r-I 

0 

Cn 

Table 3-5. Targ

et Tape Entry Data 

-1 

0 O 

0 

0 

id 

n3 

0 

ti U 

a) 

BIF-4-B10009-68 

Page 52 

Priority (inactiv

e) 

Numberof looks 

Diam

eter 

Altitude 

Signof altitude Shade factor 

Photo m

ode w

eighting function 

Targ

et alter ca

rd flag 

Signof desired stereo angle 

rn 

0 

0 

0 

0 

Direction of pass 

Cou

ntry c

ode 

Priority (activ

e) 

Desir

ed stereo angle 

Scan targ

et flag 

Bench mark flag 

0 CV 

r-I 

CV 

I-4 CV 

0 

1-1 

DC DC "C; T) b b no 7; 

4-1 4_1 0 o 

CV 0 (NJ r-I Cr) 

0 0 r-i CI 

CV Cr) 

00 b -c; 

nzi 0 0 0 

0 0 CV Cr) Co 

CNI Cr) Cr) 

CV v-4 

CO 0 

0 O c:3 

0.1 

H 

ca 

1-1 

Cr) 

0 0 

O 

U) 

Cn 

O 

H 

z x z x x 

11 

Ln 

M 

Ln co 

F4 H H 

Ga 

U 

0 

T/D 

CV 

CV 

H 

CV 

CV 

1-4 

H 

Co 
- 

last 2 characters 

- 

first 8 characters 

H 

Special category c

ode 

Resolution req

uirements 

Targ

et location v

alidity 

Targ

et latitude (North or South) 

Targ

et latitude 

Targ

et latitude 

SpecifiedATS view time 

Targ

et latitude 

4 

Pitc

H 

h weighting function 

TBD, mis

sion number 

Weather fa

ctor 

H

o 

H 

DC 

-0 -6 

a) 

cr) 0 q 4 o 0 

0 O O co O 

Cr) Cr) H ce) 

L In %.0 

(NI H CO 

U 

a) ck0 N-1

0 a) 

e E 

CO O 

H Cr) 

N N N. co 

C•4 H 

CV 

H 

00 

H 

CV 

N N 

H 

H 

H 0 

E-1 

H 

0 

I 

H 

Cr■ 

H

A 

Pr

obability of activity 

Mandatory ATS view flag Mandatory p

rimary flag 

Definition 

Table 3-5. Targ

et Tape Entry Data (Continu

ed) 

CV 

Declaration 

Cr) Cr) Cr) 

H 

O ti 

WE( D BIF-4-B10009-68 

Page 53 

4 0 

H 

t.0 

Cr) 

rH 

H 

o 

A 

H 

Cr) 

H 

iEGRE1TD 

c■I 

z 

z cc 

H H 
Definition 

Table 3-5. Targ

et Tape Entry Data (Continu

ed) 

Total latitude field 

Ca

rd type flag 

Targ

et longitude (East orWest) 

Visu

al intelligence flag 

Total longitude field 

Targ

et longitude 

Targ

et longitude 

Targ

et longititude 

BIF-4-B10009--68 

Page 54 

_SECREVD 

•-t an E c.) .7; 7:) v-Cc 

0 

a) 

-0 0 >~ G 0 

00 cs.1 0 c■I CO CNI CI CO 

1-1 r 4 Ch -4- 

- 

r-1 

r•-• CO 00 CO ON CO CT CT 

c■1 Cs] 11 r••• 

cr) cs) cNi Z cn ■Dc000 Z 

CA 

- CO CO CO ,4 t-A 

HH H H H H H •H 

rz) al ACIA A 

--SEC-RE17 D 
Mandatory p

rimary flag 

Mandatory ATS view flag 

Definition 

Table 3-5. Targ

et Tape Entry Data (Continu

ed) 

Qi 1-1 

O 1-) 

U) 

4J 

•e-1 Declaration 

I.D. - last 2 characters 

Special category c

ode 

Targ

et location validity 

Resolution req

uirements 

Weather factor TBD, mission number 

BIF-4-B10009-68 

Page 53 

I.D. - first 8 chara

cters 

144 

0 (/) 

E—I 

"tC 

.7-1 "0 

(1.1 ri •f-i 

-ca 4-4 cti •r-i 

o a) 

31 

414 et) 

Pitch w

eighting fu 

H O 

-6 -6 -7, -6 -6 -0 -0 .7; op 0 U -c) a) 

0 a co 

a) 

0 0 0 0 N-1 a 0 "0 6 (1) 

-4-0 s.0 0 N 0 0 CV CO 0 CV (NI 

• Cn Cn H M Cn • H en i. 

CV ".0 

en m en -a- -a- in in vo "0 .r) CO 

H r—I CV CV 1-1 CO CV CV CA en H N CV CV H 

r—i CV CV ri CV CV 

ON 0 H en in co 

• 

Z esi -I-en ON cn N eV H 

cs.1 en en M

33 

m cc)in in CO Lf1 

• 

1**, 1-1 

Z co 

H H H H H E-I H H 

▪ 

H H E-4 

A A A A A A A A A A A A A A A 

,SECREIID 

Targ

et latitude 

Targ

et latitude 

Targ

et latitude 

Targ

et latitude (Nor

th or South) 
De

finition 

Table 3-5. Targ

et Tape Entry Data (Continu

ed) 

De

claration 

0 

0 Fp 

c• 

>— 

0 

0_ W CL 

< < 

0j 

04 w Z Q 

Total latitude field 

Card type flag 

Visu

al intelligence flag 

Targ

et longitude (East orWest) 

Total longitude field 

Target longitude Targ

et longititude 

Target longitude 

BIF-4—B10009-68 

Page 54 WoRETD 

7:1 

• 

oo a) E u C1.1 "Cl b "0 'CI 

0(0 000 

00 C•4 O N i0 N N 00 

co co c0 ON 00 ON ON 

kC) M N CNI 1-1 

X 

C.7 r.4 

Gzi M N N Z Z r 4'4) 

H HHH 

CN ,4 co 

H 

co 

H 

c0 0 0 

MAXX CC (Z1 H H 

-SEGRETID 
Table 3-6. Epheme

ris Data from Table DEPHDA 

H H 

O 

1-) 

Declaration 

Ascending node flag Vehicle number 

CO 

a) 

a) 

H 

LH 

O .1-1 

4-1 

4-1 

O 

O 0 

11 CU 

O 

• 

0) 

O 

• 

+-I 

o 

0 

H 

C.) •H 

w+3 

ifOREVD BIF-4—B10009-68 

Page 55 

De

finition 

0 

04-1 

.1-1 •ri 

4-1 C.) 

N-I 0 

a) u) H 

CO 0 a) 

cd a. > 4 

a) a) 

O H H 

o c.) 0 

H •H H 

H .0 .0 a) a) 

tr) > > a) 

H 4-I LH 

O 0 0 

U) 

CO CO CO 

0 0 g 0 

a) •T-i 01 N-I 

O o 0 

-rt o. 4-) 0+ 4-) 

4-) 0 0 0 0 

CD CL) 0 0) 

4-1 C.) > U > 

O 0) CU a) 

cu 5 H H 

> •rf C.) 41 C.) 4-1 

w +-1 41 CO fil ai 

N N N 

0 0 0 0 

1-1

0 

ri -1-1 .1-1 4-1 •r-I 

0) - 

0 0 Ei ia 0 

....... -.... ...„ -.... ..... 

1.1 . . 

•T-1 0 H 1-1 $:4 H H 14 ..C:1 '7) 

• 

"0 H 14 1.4 

-I-1 . . 

ia CU (1) a; a) 0 a) 0 0 0 a) a) a) 

0 CD CD 0 0 0 0 CD CD CNI

▪ 

 CD CD CD 

CD 0 

v—I N ("1 Ln s.o r-• co c 

00 ...1" 

N 

rx4 W i W W 44 W H H H W 44 rx4 

H 

0 rE4 43 A A A P = 

5, H H -INQP-itPP al 

N Z c 

CT.) 

> cn A A A A A AA A A A PA A 

iEGRE-17D 
Table 3-7. Ephemeris Data from Ta

ble DEPHID 

First ve

hicle number 

Number of vehicles ontape 

Update number 

base reference 

Earth rotation rate Vehicle number 

Gregorian base r

eference date 

Number of orbit adj

u

sts 

Ea

rth gravitational constant 

0 

-0 "C) "c;. G 

0000 ,230 

O 

,40 

0 

CO 

-. 

H 

cs1 O 0 -r 

r-1 ,--1 

r--- cs1 .-4 

0 0 

00 ..1. ■.0 

c•A 

H 44 H 

<4 w w c) <4 Z 0 E.' A A A A A Z A 0 A A 

0 0 04 M La 

z 41 

0 0 0 0 0 0 

H ,--1 ,--i cs1 01 -.7 r-- 

0 0 0 0 

CO 00 00 CO ...T -.7 -.1- --t 

rx4 H H H 4-4 44 

1-1 0 cd 

0 p E b $4 

BIF-4-B10009-68 

Page 56 Definition 

41 cd 

•■-1 

cl) 

ch 

0 

0 4-1 

0.1 ci al 

cn cd 4-1 4.J a) 

b0 ro 

rl tri 

LYa ..n 

.613 (

-do "Oct -r.; 

.= 

F.+ a+i 

0 0 0 

,..0 r-1 L 

00 Co -.I -7 

44 H H 

0 

f:4 H 

O 0 

Declaration 

4-E-GRETI 
Table 3-8. Ephemeris Data fromTable DOADJ 

Vehicle inclination 

Fuel flowof orbit adjust Pitch of orbit adjust 

Type of orbit adjust Yawof orbit adjust 

Weight of orbit adjust 

-SECIET7 D 

Definition 

0 

cn 

•*-) 7 

cd 

4-) 

ccl 

4.1 

4-1 

$-) 

0 

LH 

o LH 

a)

0 

0 

0 

ell d 0

) 

4-I 

4-) 4-) 

4.4 

$4 a) 

cd cn $.4 

4-I cd 

cn .0 Pa 

cn 

4-I 

-H 

0 (1) 

c) 

0.) 

"r. "0 "0 

cd 

"0 

cd 

co Cl) 0 0 $-1 

O 0 0 0 C 0 0 0 

0 rl cs4 O ("0 •4-0 r4 

H cd 

$.4 0 cd 

1-3 H 

a) co 

H w Pt, w 4.1 4+ 

H 

0 H pa H 1-1 <4 

44 

cn A 

0 

A A 

0 

A 

0 

A 

0 

A 

0 0 

A 

<4 

0 

A 

-SECRETTD 

BIF-4-B10009-68 

Page 57 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 58 iteRET/ D 

3.3.2.4 THINGS Table 

The THINGS table items required by TWPATW as specified through File 7 

and File 8 parameters are described in Table 3-9. 

3.3.3 Output 

The output of TWPATW are the intermediate acquisition tapes. These 

tapes are subsequently processed by TDMERGE into the acquisition tape 

(ACQ tape). The acquisition tape records generated by the TWPATW contain 

the following information: 

a. Header entries for each revolution. 

b. Target acquisition entries. 

The parameters contained within each header entry are described in Table 

3-10. The parameters contained within each target acquisition entry are 

described in Table 3-11. 

3.3.3.1 Method 

TWPATW accepts data from the target tape (construct option) or a previously generated acquisitions tape (update option), and ephemeris data 

produced by the DDI general purpose tracking program. TWPATW computes approximate target acquisition times and other acquisition data and stores 

these data on an intermediate acquisitions tape. 

The target add, delete and change tapes output by TWOPIN may be 

processed together with either the target tape or a previously generated 

acquisitions tape. Thus, the following four modes of TWPATW operation 

are available: 

a. Construct option 

b. Construct with add, change or delete option 

c. Ephemeris update option 

d. Ephemeris update with add, change or delete option 

TWPATW also processes the LAT and TIM tape. LAT entries delete all targets 

of a given priority range within a specified latitude band. TIM entries 

delete all targets of a given priority range within a specified time span. 
THINGS Table Items Req

uired byTWPATW Table 3-9. 

0 0 

0: acq

uire targ

ets NS and SN 

1: acq

uire targ

ets SN only 

-1: acq

uire targets NS o

nly 

4.) 

cC 

ri 

$.1 

CC 

11) 

I-1 

0 

4-1 

4-4 

E-4 

<4 

4-1 

Cd 

-Hi 

LH 4-I 

0 0 

Flag for deletion comme

nts on Tape 8 

U) 

C 

(11 

U

0 

0 

C 

O r--1 comments outp

ut 

Res

et File Definition 

_SECRET7D B IF-4— B10009-68 

Page 59 

H 

CO 

0 U) 

1-I 4-1 

CU 1-1 . 

4-) 0 '1:) '0 $.4 P T) Ti 't; 

0 . 0 

1-4 P $.4

0 0 

a) a) &4 1-4 0 

0 

0 

I-1 vi 

1-1 .11 ce) 

0 0 0 0 0 cl) .....t 

0 ,-1 0 1-) 41 ...7 oi N- q) Lel 0 

a) H N. N. N. In en a% 

A w' W cNI rz4 Cs1 GLI CV 4.1 Cr) Pza CV 1--1 ri 

1—I 

0 1--1 

0 0 <4 0 0 CV 

CC1 1-1 P-■ 4-1 1) 0., "4 z z z cn .-1 

to pc) 0 0 0 W cx) W 

1.--1 0 [4 A al 

CL) CO 

C./ 4.) 

co 00 0 

0 ..-1 )4 

0.0 

I-I IL $-I CO W 

CO a) 0 LI-4 9.-1 4-1 

P• cc) 0 

CH 10 Cr a) 

0 0 C). cu 

W c.) 0 4..) ctl 0 

......... 1-1 c.) 4.1 

OD 0 00 vi 

W 0 a) $.4 0 1..) 00 

4-1 n-I n-I 0 U 44 

9-I 4.4 ,0 a) a) -61 a) 01 ,.Z 00 4-1 

H -0 > $.4 U n-I „O 

al 

0 

0 ..= 00 

0 n-I 

131 0 0 11 vi 4-1 H 

4-1 

C./ 3-1 0 '1) 13.) 

4 4-1 1-1 cd 00 4-1 0 

> .

0 

1-1 CO 03

0 

5 

P 0 n-I 

0 $4 W al (1) NI 

0 cd 4-1 5 0 cd 

0 n-I ai a) 11 

4-1 41 0 H P H 0 

X I-I 00 f-I 00 U 04 0 

cO 0 00

4-i 0 H 

0 00-1-1 

Z u) -0 9-1 4-1 

U) 

4..1 

-H 00 E 0 00 bl) 

0 a) a) 

00 

a) a) 

-0 

A 'V -0 C C -0 -0 C 

Interface Ta

ble Usage 

Definition 

o

bliquity angle (for swath 

Minimum sunangle (for sw

ath sort) 

Maximum slant range (for swath s

o

rt) 

Direction in TW

PATW 

ri O 

O 

CC 

0 0 

vi ri • 

O

E 0 Ln 

cs1 

0 

a) 

Lri 0 

O 

4-1 10.1 a4 CL o o cts Px4 fr.+ CT.4 

W A 

w as 

0 

r■-• 00 0 

H re) ~7 t--- CO -.7 ,--1 1,1 111 1- 

a) 4-1 4-1 0 0 0 0 ON ri H r-i H 

1--I 0 cd 0 0 0 0 0 H r--I 1-1 1-1 

n-I U > J > > E-1 E-I E.! E-4 E-1 

L.4 0 CO3 41 44 0 0 C.) 0 C-) 

0-1 CO CO CO CO 43 PEI W PT-4 44 

_SECRETID 
(base reference time) 

Start time of first revof interest Time ending last revof interest Day of month (base reference time 

Orbit period 

Initial revof interest 

a) .0'o 

4-) CI) •rI 4-1 

00 0 

0 co u" •ri a) C.) 

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r. 

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fr) ,c4 

H 

H A 

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0 

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N.0 

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A 

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Table 3-10. Acquisition Tape Header Entry 

Definition 

5 

a) 

3.1 

Time of ascending node 

Header record flag 

-SEC-RET7 D 
<4 1-1 

0 ti 

Declaration Definition 

Revnumber of targ

et acq

uisition 

Time of vertical acquisition 

Acq

uisitiondirection flag 

Sun elevationangle at acq

uisition 

Slant range at ve

rtic

al acq

uisition 

U ctl 

H 

ccl 

U 

4-1 

4-1 

,c1 O 

H 

4-) 

H 

ca 

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(last 2 characters) 

Latitude 

iEC-RETt D BIF-4—B10009-68 

Page 61 

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Table 3-11. Acq

uisition Tape Targ

et Data Entry 
--SEGRET/ D BIF-4—B10009-68 

Page 62 

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Ta

ble 3-11. Acq

uisitionTape Targ

et Data Entry (Co

ntinued) 

Definition 

Direction of pass 

Visual intelligence flag Targ

et location validity 

Specified ATS dwell time 

Ben

chma

rk flag 

Mandatory p

rimary flag 

Probab

ility of a

ctivity 

Scan targ

et flag 

Desired pitch angle 

Resolution req

uirement 

Photo m

ode w

eighting function 

Prio

rity (a

ctive) 

Priority (inactive) Sp

ecial categ

ory code 

Ma

ndatory ATS view flag 

Targ

et alter ca

rd 
NRO APPROVED FOR 

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Page 63 

The discussion of the computational methods employed by TWPATW presented here is divided into two sections. The first section discusses the 

sequence of computations in TWPATW. The second section discusses the 

significant analytical techniques employed within the computational sequence. 

A flow chart of TWPATW is presented as Figure 3-3. 

3.3.3.1.1 Computational Sequence 

TWPATW computes acquisition data in the following sequence: 

a. Enters closed subroutine PATTAB to develop a table of analytic 

ephemeris data for the specified rev span. PATTAB calls subroutines SUNDECK and LIMLAT to compute the average sun vector 

over the specified rev span and to compute the limiting target 

latitudes over the specified rev span arising from sun angle 

and inclination constraints. Subroutine LIMLAT also computes 

the latitude boundaries which define the regions in which targets may be acquired on multiple revs within one orbit period. 

b. If there are any unprocessed entries on the target add tape, 

or if TWPATW is operating in the construct mode and all the 

target add tape entries have been processed, TWPATW processes 

each target addition or target from the target tape as follows: 

1. Enters subroutine DTPCDT to decode and store the target 

data for processing. 

2. Enters subroutine PATENT. PATENT deletes those targets 

whose latitude exceeds the limiting latitudes computed 

in PATTAB and computes an approximate vertical acquisition 

time for those targets not deleted, to initialize the iteration technique used in subroutine CONTAK. 

3. Enters subroutine CONTAK to compute vertical acquisition 

time and payload operation parameters at vertical acquisition. CONTAK checks the payload parameters against input 

limits. CONTAK processes the target deletion and target 

change tapes and deletes or changes the target if affected. 

CONTAK calls subroutine LATBAN to process the latitude 

band and time band deletion tapes. If the target is not 

deleted CONTAK prepares an acquisition tape entry. 

If TWPATW is operating in the update mode and all the target 

add tape entries have been processed, TWPATW processes each 

target on the old acquisition tape as follows: 

1. Enters subroutine RDACQ to decode and store acquisition 

tape entry information for processing. 
NRO APPROVED FOR 

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IEGREI/D 

2. Enters subroutine CONTAK to compute vertical acquisition time (the iteration technique is initialized 

with the vertical acquisition time on the old acquisi 

tion tape) and payload operation parameters at vertical acquisition. CONTAK checks the payload parameters 

against input limits, processes the target deletion 

and target change tapes and deletes or changes the 

target if affected, and calls subroutine LATBAN to 

process the latitude band and time band deletion tapes 

If the target is not deleted, CONTAK prepares an 

acquisition tape entry. 

3.3.3.1.2 Analytic Techniques 

3.3.3.1.2.1 PATTAB 

Subroutine PATTAB reads and processes data from the ephemeris tape 

to develop an analytic ephemeris table. The ECI coordinates for key times 

(ascending nodes and orbit adjusts) within the specified rev span are converted to a set of orbital parameters which are in turn used to compute an 

average set of parameters for the orbit interval between adjacent key 

times. The sets of average orbit parameters computed for each orbit interval consitute the analytic ephemeris table. 

The ECI quantities that define the state vector at the start of 

each interval are used to determine those PATTAB table parameters for 

the beginning of each interval through the following computational steps. 

Compute vehicle radius from center of the earth, rI 

Compute vehicle inertial velocity, VI 

. . 

V

I 

= y

2 

x + + z

2 

 . 

Compute the quantity (xi.), 

(ri), = xi + yir + zi . 

Compute total angular momentum of the orbit, hi 

hI =-/ri

2

VI

2 - (ri), . 

1-ENETI D 
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Compute ECI components of angular momentum 

h

x 

= yi - z ST 

h = z* - xi 

y 

h

z 

= xST - yk 

Compute right ascension at the beginning of the interval with respect 

to the equatorial plane, aI 

a = tan I 

1 (h

x 

 /-h 

y

) 

(0 < tan 1 < 27) 

Compute longitude of the vehicle at beginning of interval (DI 

(1) = aI 

- a - w

e 

(t

I 

- t

o

) . 

where tI 

is the time at the beginning of the interval and t

o 

is the 

time at which right ascension of Greenwich, a

o

, is defined, both 

referenced to base time. 

Compute auxiliary orbital elements related to eccentricity and true 

anomaly 

e sin u = (ri.) h /p r 

I I I 

e cos u = (h2

/II r

I 

 ) - 1 

I 

Compute orbital eccentricity at interval beginning, eI 

e

I 

=leI

sin u1)2 + (e cos u1)2 
NRO APPROVED FOR 

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-SEGHUD 

Compute orbital true anomaly at interval beginning, III 

u

I 

= tan

1 (e

I

sin u

I

/e

I

cos u

I

) 

(0 tan-1 -<- 27) 

Compute the vehicle in-plane angle (argument of latitude), T , measured 

in the orbit plane from the ascending node to the vehicle. 

YI 

1 = tan [zhI

/(yh

x 

- xh

Y 

 )] 

(0 <tan 1 < 27) 

Compute the argument of perigee of the orbit 

Compute the vehicle mean anomaly 

M

I 

= u

I 

- 2e

I

sin u

I 

. 

Calculation of average orbital parameters 

In order to provide the CONTAK acquisition iteration with more 

uniformly representative values over duration of an interval, average 

values are calculated for some orbital elements that are subject to 

slow change . 

Compute average orbital eccentricity for interval n, en 

kedn + (edn + 1] 

e

n 

- 2 

Compute average argument of perigee for interval n, 811 

s [(q)n + "I)n + 1] 

-n 2 • 
(PV)n (14I

)

n + 1 - (14I

)

n 

(At) n 2Tr 

4E-RETID NRO APPROVED FOR 

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Page 67 

The average vehicle anomalistic period for interval n, (pv)n, is computed 

from the average change in time per unit change in mean anomaly 

••• where (qI)n is the value of mean anomaly at the start of the nth interval. 

The interval n time duration, (At)

n

, is 

(At) n= (tI)n - 1 (t ) I n • 

The average orbit period for interval n, (p0)nis 

271- 

(13°)h- (1)1)n

- (Yn + 1 

(At)n 

where (cynis the longitude at the start of the nthinterval. 

Interval continuity parameters 

In CONTAK additional terms are used in the expressions for the 

quantities Tv, and h (vehicle in-plane angle, rate of change of inplane angle, and vehicle altitude) in order to maintain continuity 

between intervals. These adjustments are made necessary by the use of 

constant average values of e, f, pV and p

o 

in each different interval. 

First, consider continuity constants which ensure the continuity of 

the vehicle in-plane angle, Tv, during acquisition iteration. The 

nominal expression for the in-plane angle during interval n is given by 

= sn+ (uv)n= sn+ (1v)n+ 2ensin(Mv)n 

where 

(MV)n = (1qI)n (1*-[(tV)n (tI)ni • V n 

Since average values are used for e, po, and pv, CONTAK utilizes the 

following equations (to first order) : 
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-SEGREft D 

(TV) n 

 = (TV)n 

t+ A

n 

 + B

n 

 [(tV 

 ) 

n - (tI)n 

• 

V (T ) cos(M„„) + B n (p 

V 

)

n 

v n j 

where A

n 

and B

n 

are constants which provide continuity between intervals 

n and n + 1. 

A

n 

and B

n 

are computed as follows: 

At the start of interval n 

(tv)n= (tI)n 

and 

(41V

)n = (TI

)

n 

= 8

n 

+ (MI)n + 2e

n

sin(M

I

)

n 

+ A

n 

Hence, 

A

n 

= (TI)

n 

- 8

n 

- (MI)n - 2e

n

sin(MI)

n • 

At the end of interval n, i.e., at time (tI)n + 1 

(13.1-19) 

and 

At this point 

(tV)

n 

= (tV

)

n + 1 = (tI)n 

(AM)n = (4I)n+1 - 04 ) - I n r(tV)

n 

- (tI ) 

L 

1 27 (p ) 

V n 

- ) • 

(At) (pvn n 

(TV )n = n (MI)n+ 1 = 2en

sin(MI) n+1 A

n Bn (At)n 

and it is desired to make TV continuous such that at (tI

)

n + 1 

(TV)

n 

= (TV) n + 1 = (TI

)n + 1 
NRO APPROVED FOR 

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Page 69 

Thus 

B

n 

= B

n

(At)

n 

= (TI )n+1 -8 

n 

 -(MI )n+1 -2e 

 n 

 sin(MI )n+1 - [(V )

nn 

 -(MI ) n-2e 

n 

 sin(M ) 

I I n , 

= (IjI)n+1- (TI)n+2en[sin(MI)n-sin(MI) 

27(At)n 

n+1 (PV)n 

and the continuity constant Bn is defined by 

B

n 

= B

n

/(At)n 

Procedure CONTAK makes a second-order correction in the vehicle in-plane 

angle to account for periodic errors by replacing (Tv)nwith 

(1,

V

)

n 

- AT sin 0'V)

n 

where AY is an empirical correction factor. This correction factor, 

however, does not significantly affect acquisition convergence in CONTAK . 

The vehicle altitude during interval n for continuous values of f3, and e 

is nominally given by 

1 

hn - - 1 + f sin2 i sin (1/On 2 (V )n 

where f is the flattening of the earth, and 

1 1 1 1+e

n

cos(T_ 

n" 

- 8_)1 J v 1-cos -T

In

) 

n (rI

)

n 

Ll+e

n

cos(T

In

- an) + 

r )3 

(In 

si 2. n I 

3 21 cosi'I cosTV 

 -1 + sin2T

v 

+sin2Y

i

n n n n 

7cos(TV-TI

)-6: 

n n 

• 

But with the use of average values for S and e, altitude is computed 

(in CONTAK) by 
NRO APPROVED FOR 

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-SEC-REVD 

h

n 

= hn 

+ Cn 

[(tV

)

n 

- (t1)n ] . 

At time (t1)n+1, it is necessary that h+ = hn+1 for altitude to be 

continuous; at this point 

(TV)

n 

= (TV

)

n+1 = (TI

)

n+1 and ( 1 - reduces to 1 

r n+1 (rI

)

n+1 

Thus, 

h

n+1 = (rI

)

n+1 - 1 + f sin2i sin2 

 (TI) n+1 

h

n+1 - 

1 

+ - 1 + f sin2

i sin2 (TI

)

n+1 + Cn

(At)

n 

, 

WO 

and it follows that 

where 

C - 

n 

1 

r)n 

1 1 

(At)n [ 

_ 1 

(r I) n+1 - (1/r)-TEI j 

[ 1+e

n

cos(TI -13n

) 

n+1 

(r )3 I n (rI

)

n 

1+e

n

cos(TI -13n

) 

n 

n 

2. 

El - cos (TI -T si I) + Cn 3I 

n+1 n 

and 

2 Cn = 2 (cosTi

cosT

in+1

-1) +sin2T

in+1 

+ sin Ti 

n n 

[7cos(TI -T1 ) -6] 

n+1 n 

n 
NRO APPROVED FOR 

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Page 71 

Subsequent to the determination of orbital parameters for storage in 

the analytical ephemeris table, PATTAB calls closed subroutines SUNDEK and 

LIMLAT. SUNDEK computes the average sun vector over the specified rev 

span. LIMLAT computes limiting latitudes for acquisition over the specified 

rev span arising from sun angle, inclination and miss distance constraints. 

Subroutine LIMLAT also computes the latitude boundaries which define the 

regions in which targets may be acquired on multiple revs within one orbit 

period. 

3.3.3.1.2.2 PATENT 

PATENT compares the latitude of the target in progress to the maximum 

and minimum latitudes computed in LIMLAT based upon sun angle and inclination constraints. If the latitude of the target is outside of those bounds 

the target is deleted. 

PATENT interrogates the direction flag DF stored in table THINGS to 

determine if targets are to be acquired on both North-South (NS) and SouthNorth (SN) passes, or only on NS passes, or only on SN passes. The flag DF 

is set through File 8 parameter EGT113. 

The quantity, tzo, which is subsequently used by CONTAK to initialize 

the iterative procedure employed therein to determine the time at vertical 

acquisition is computed as discussed below. 

PATENT compares the latitude of the target to the latitude limits 

computed in LIMLAT which determine the possibility of multiple acquisitions 

per orbit period. If multiple acquisitions of the target per orbit period 

are possible, PATENT computes tzoas the earliest time the vehicle will be 

at maximum latitude (for targets in the northern hemisphere) or at minimum 

latitude (for targets in the southern hemisphere). The equations employed 

follow: 

t

zo 

= t1 + 1/4(pV

), 

for targets in the northern hemisphere. 

t

zo 

= t1 + 3/4(pV

), 

for targets in the southern hemisphere, where t1 is the start time of the 

first orbit interval, pvis the average vehicle period for the first orbit 

interval (computed in PATTAB). 

IteREVD 
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BIF-4-B10009-68 

Page 72 

-1-E-ORETiD 

If multiple acquisitions of the target per orbit period are not possible, 

PATENT computes tzo as the earliest time at which the target is in the 

orbit for a SN acquisition, or a NS acquisition or both as dictated by direction flag DF. A discussion of the equations employed follows. 

If at some time the target lies within the orbit plane, then at that 

time, the angle between the target and the ascending node measured in the 

equatorial plane, QS' is equal to 

= 1, { n-sin ktan6 /tan i) NS 

sin 1(tan 6S /tan i) SN 

where e is the latitude of the target, i is the inclination of the orbit. 

Suppose that at time (tI)n' 

the initial time of orbit interval n, the ascending node of the orbit is located at longitude (4)I

)

n

. Then at time (tI)n the 

angle between the target and the ascending node measured in the equatorial 

plane, is equal to cps - (cyn, where cPs is equal to the longitude of the 

target. Thus if the target is to lie within the orbit plane, the ascending 

node must rotate by the quantity, AQ where 

AQ = 2 - (q) - S I

)n) S 

The average orbit period over orbit interval n is (p0)n. Therefore it may be 

written that the change in the location of the ascending node over interval 

n is equal to 

n 

A2 = (t - (tI

)

n

) S (p 2

°

)

n 

where t = time measured from reference time. 

At t

zo 

 the target is to lie in the orbit plane, therefore, 

(p

2n 

) (tzo 

- (tI)

n

) = S - (4) - (0I)n) 

0 n 
+ 

(130)n (

sin 

-1 

- sin 

tan e

s 

s 

] 

0I

)n ) 

(4)I

)

n 

) NS 

271- 

(P0)11 

tan i 

[tan es 

2Tr tan i ()s 

and, thus 

t = 

zo 

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Page 73 

The computation presented above is repeated for each orbit interval within 

the specified rev span until a tzois found for an interval n such that 

(tI

)

n —

< t

zo 

(t

I

)

n+1. 

3.3.3.1.2.3 CONTAK 

Closed subroutine CONTAK employes an iterative procedure to determine the value of the time at vertical acquisition. The procedure is initialized by setting the current estimate of vertical acquisition time 

equal to either the value tzocomputed in PATENT (if the target entered 

TWPATW as an add target or on a target list) or to the acquisition time 

on the old acquisition tape (if the target acquisition data is being updated). 

CONTAK locates the orbit interval containing the current estimate of 

acquisition time. Using the PATTAB computed orbit parameters associated 

with that interval and the current estimate of acquisition time, the 

vehicle in-plane angle from the ascending node at the estimated acquisition 

time. That angle, 11)17, is computed as follows. 

TV = e + U + A + B (t- tI

) 
NRO APPROVED FOR 

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Page 74 

where 

-1E-ORERD 

6 = average argument of perigee for the orbit interval 

A, B = orbit interval continuity constants 

U = true anomaly at time t 

t = current estimate of acquisition time 

t

1 

= start time of interval containing t 

The true anomaly at time t is computed as follows: 

U = M + 2e sin M 

where 

e = average eccentricity for the orbit interval 

M = mean anomaly at time t 

The mean anomaly at time t is computed as follows: 

M = MI 

21T +----(t - t1) (P ) V 

where 

M

I 

= mean anomaly at time t 

p

V 

 = average vehicle period for the orbit interval 

After completing the computation of Tv, CONTAK computes the angle Ts. Ts 

is the vehicle in-plane angle from the ascending node required for vertical 

acquisition at the current estimate of vertical acquisition time. Ts is 

computed on the basis of geometrical considerations at follows: 

11) = tan-1 cosi cos 8

s 

sin

s 

+ sini sin 0

s 

cos e

s 

 cos Sts 

where 

i = orbit indication 

s 

= target latitude 

0

s 

= angle between the target and the ascending 

node measured in the equatorial plane 
--SEIREVD NRO APPROVED FOR 

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BIF-4-B10009-68 

Page 75 

s 

is computed as follows 

Os = (Ps -~I+ (t - ti) 

Po 

where cps = target longitude 

cp

I 

= longitude of ascending node at tI 

p

0 

= average orbit period over orbit interval 

t = current estimated vertical acquisition time 

Ip v and ips are computed using the current estimate of vertical acquisition 

time. If the estimate is correct, IP V = 4)s. If 1PV ips a new estimate of 

vertical acquisition is obtained through solution of the equation 

4)17 

t

new 

= t

old • • 

- 1P V 

where . 

t

new 

= new estimate of vertical acquisition time 

t

old 

= old estimate of vertical acquisition time 

s 

= derivative with respect to t of ip

s 

tp v = derivative with respect to t of ipv 

The process is repeated until 

1p

Vs 

EPSI 

where 

EPSI = convergence constant stored in table THINGS, 

specified through EGT094. 

Subsequent to the determination of a vertical acquisition time which 

satisfies the constraints imposed by EPSI, CONTAK determines whether the 

target can be acquired on multiple revs within an orbit period. 

If multiple acquisitions of the target are possible, CONTAK determines the direction of pass (NS or SN) for the acquisition time found, 

deletes the acquisition if the pass direction is not to be allowed, and 

increments the acquisition times by one vehicle period. CONTAK recycles 

-IMMO 
NRO APPROVED FOR 

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--SEGREVD 

B1F-4-B10009-68 

Page 76 

to search for a new acquisition time using the incremented acquisition 

time as the initial estimate. (THINGS table item DELP02, specified 

through File 8 parameter EGT111, is employed in the determination of pass 

direction.) 

If multiple acquisitions of the target are not possible, CONTAK 

increments the acquisition time found by one orbit period, and recycles to 

search for a new acquisition time using the incremented acquisition time 

to initialize the iterative procedure. 

Subsequent to the computation of each acquisition time CONTAK computes the values of sun angle, target obliquity, slant range to the target 

and vehicle altitude at that time. 

CONTAK compares the values computed to input constraints on these 

quantities. Targets which fail to meet the constraints are deleted. 

THINGS table parameters CONSSA, OBLBAR, CONSRU, and CONSAU are, respectively, 

the minimum sun angle, the maximum obliquity, the maximum slant range, and 

the maximum vehicle altitude. CONSSA, OBLBAR, CONSRU, and CONSAU are 

specified through File 7 parameters SEV004, SEV003, SEV007 and SEV008. 
-SEDRMD NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 77 

TWPATW TWPATW 

,......., 

• Rewind intermediate and 

final acquisition tape 

• Rewind input tape 

Ephemeris 

Tape 

PATTAB 

• Set up table of constants for 

analytic ephemeris 

• Compute limiting sun angle 

• Compute limiting latitudes 

based on sun angle and orbit 

inclination 

Figure 3-3. TWPATW Flow Chart 
V 

Set option flag for 

add option 

(

Is an acquisition tape the 

primary input tape? 

Yes 

Set option flag for 

ephemeris update option 

V 

K Are there any add 

cards? 

Yes 

Read 

add card 

tape 

c) 

).---- Is an acquisition tape No 

the primary input tape? 

Yes 

Read 

acquisition 

tape 

NRO APPROVED FOR 

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BIF-4-B10009-68 

Page 78 

-SICKSYD 

TWPATW TWPATW 

Figure 3-3. TWPATW Flow Chart (Continued) 
(

Are there any 

add cards? 

No 

(

Is option flag set for 

construct option? 

No 

RDACQ 

Decode and store acquisition 

tape entry information for 

processing 

Yes 

Yes 

NRO APPROVED FOR 

RELEASE 1 JULY 2015 

-SttREUD BIF-4-B10009-68 

Page 79 

TWPATW TWPATW 

Read 

target 

tape 

DTPCDT 

Decode and store target card 

information for processing 

~J 

Figure 3-3. TWPATW Flow Chart (Continued) 

SECRET/D 
Yes (

Is option flag set for 

add option or for construct option? 

Set initial values for 

CONTAK from acquisition 

tape entry 

IN° 

CONTAK 

• Compute acquisition time and 

check payload and ephemeris 

parameters against limits 

• Prepare acquisition tape entry 

NRO APPROVED FOR 

RELEASE 1 ##P:A1/110009-68 

Page 80 -SECIET-1 D 

TWPATW TWPATW 

Figure 3-3. TWPATW Flow Chart (Continued) 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 -SEC-RE-T./ D 131F-4-B10009-68 

Page 81 

TWPATW TWPATW 

PATENT 

o Check target latitude against 

maximum and minimum latitudes 

computed in PATTAB 

o Compute an approximate time to 

initialize the iteration technique for CONTAK 

(

Was target deletion flag 

set in PATENT? 

Yes 

No 

Are there any unprocessed target 

tape, acquisition tape, or add 

tape entries? 

Wrap-up 

acquisition 

tape 

( RETURN ) 

Figure 3-3. TWPATW Flow Chart (Continued) 

'SEM/ D 

( No 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 82 

PATTAB PATTAB 

Separate and organize ephemeris 

data for processing over individual orbit intervals 

Set interval counter for first 

interval 

• Find vehicle position and velocity 

in ECI coordinates at start of current interval 

• Compute total angular momentum and 

ECI components 

• Compute longitude at start of current interval 

Compute orbit parameters at beginning of current interval 

( Are present calculations for 

first interval? 

Figure 3-3. TWPATW Flow Chart (Continued) 

--SENEVD 
NRO APPROVED FOR 

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Page 83 

PATTAB PATTAB 

• Compute average eccentricity for 

current interval and preceding 

interval 

• Compute average argument of 

perigee for current interval and 

preceding interval 

7 

• Compute average vehicle 

anomalististic period 

• Compute average orbit 

period 

7 

Compute orbit interval continuity 

constants between current interval 

and preceding interval 

r 

(

Is this the first computation 

of average orbit parameters? 

Yes 

V 

SUNDEK 

Compute average sun vector 

over rev span of interest 

• 

LIMLAT 

• Computes limiting latitudes over 

rev span of interest arising from 

sun angle and inclination constraints 

• Compute latitude boundaries defining 

areas in which targets may be acquired 

on multiple revs within one orbit period 

EGT115 = half-swath width used in 

computation of limiting latitude 

Figure 3-3. TWPATW Flow Chart (Continued) 
Save orbit parameters at 

beginning of current interval 

so as to be able to compute 

averages with orbit parameters 

of succeeding interval 

REVD NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 84 

PATTAB PATTAB 

V 

(

Is current orbit interval 

the last interval to be 

processed? 

Yes 

RETURN 

Increment interval 

counter 

Figure 3-3. TWPATW Flow Chart (Continued) 
—JO( RETURN ) Delete 

target 

NRO APPROVED FOR 

RELEASE 1 JULY 2015 

--SEGRETID BIF-4-B10009-68 

Page 85 

PATENT 

PATENT 

PATENT 

Set latest allowable acquisition 

time equal to time at the end of 

the last orbit interval 

(

Is target latitude within 

LIMLAT computed bounds on 

latitude for acquisition 

over current rev span? 

Yes 

• 

( 

Yes 

Are acquisitions to be NS only? 

EGT113: Direction of flight 

flag 

Set azimuth 

Yes, 

flag for 

NS only 

0 

• 

( 

Are acquisitions to be SN only? 

EGT113: Direction of flight 

flag 

Set azimuth 

flag for 

SN only 

• 

Figure 3-3. TWPATW Flow Chart (Continued) 
NRO APPROVED FOR 

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BIF-4-B10009-68 

Page 86 --SECRETI D 

PATENT PATENT 

(

Is target latitude within 

latitude limits for multiple 

acquisitions per orbit period? 

Yes 

• 

Set acquisition mode to multiple 

acquisitions per orbit period 

• 

Compute earliest time vehicle 

will be at maximum latitude 

(for targets in the northern 

hemisphere) or at minimum 

latitude (for targets in the 

southern hemisphere) 

• 

( RETURN ) 

Figure 3-3. TWPATW Flow Chart (Continued) 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

'SEC-REV D BIF-4-B10009-68 

Page 87 

PATENT PATENT 

Compute longitude from 

ascending node to target 

at acquisition, for SN 

pass 

• 

(

Is azimuth flag set for 

both NS and SN directions? 

Yes • Set flag for first 

pass in bi-directional 

mode 

No 

K

Is azimuth flag set for 

SN only? 

Yes 

Compute longitude from 

ascending node to target 

at acquisition, for NS 

pass 

• 

Set orbit interval counter 

to first interval 

• 

Set orbit parameters to 

PATTAB values for current 

interval 

Figure 3-3. TWPATW Flow Chart (Continued) 

--SECRE-TI 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 88 

-SENE-TI-D 

PATENT PATENT 

V 

(

Does this interval begin 

Prior to latest acquisition 

time? 

Yes 

V 

Compute rotation of node 

required to bring target 

into orbit plane 

• 

Compute time of 

first acquisition 

V 

(

Is acquisition time less than 

time at end of current interval? 

Yes 

,jNo 

Increment orbit 

interval counter 

Figure 3-3. TWPATW Flow Chart (Continued) 
(

Is this a SN pass in Yes 

N 01 

Set direction flag to 

indicate bi-directional 

 mode, no SN acquisition, 

searching for NS acquisition bi-directional mode? 

K

Is this a NS pass in a 

bi-directional mode in 

which a SN acquisition 

was found? 

Figure 3-3. TWPATW Flow Chart (Continued) 

NRO APPROVED FOR 

RELEASE1JULY2015 -SECRET/ D 111F-4-B10009-68 

Page 89 

PATENT PATENT 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 90 'SEC-REVD 

PATENT PATENT 

V 

Is this a SN pass in 

the bi-directional mode? 

Yes 

V 

Set time of SN 

acquisition 

Set direction flag to 

indicate bi-directional 

mode, SN acquisition 

found, searching for NS 

acquisition 

Pi( Is the pass direction 

SN only? 

Yes 

Set time of SN 

acquisition 

( RETURN ) 

Figure 3-3. TWPATW Flow Chart (Continued) 
• 

Set flag for 

NS only 

V 

Set time of NS 

acquisition 

1°( Is the pass direction 

NS only? 

N 

V 

Set flag for both 

NS and SN 

Yes 

NRO APPROVED FOR 

RELEASE 1 JULY 2015 D BIF-4-B10009-68 

Page 91 

PATENT PATENT 

Is this the NS pass of 

a bi-directional mode 

in which a SN acquisition was not found? 

Yes 

Figure 3-3. TWPATW Flow Chart (Continued) 
NRO APPROVED FOR 

RELEATI1ALAB10909-68 

Page 92 D 

CONTAK CONTAK 

CONTAK 

• 

Set latest allowable acquisition 

time. 

Set first estimate of acquisition 

Are multiple acquisitions 

( possible per orbit period? Yes 

time from old acquisition tape 

(for update option) or set first 

estimate to PATENT value computed 

for multiple acquisitions 

• 

Set first estimate of SN vertical 

acquisition time to PATENT value or 

(for update option) to value from 

old acquisition tape 

• 

(

Is acquisition direction NS 

only? 

Yes 

• 

Set first estimate of NS vertical 

acquisition to PATENT value or 

(for update option) to value 

from old acquisition tape 

r 

• 

Set orbit interval counter 

for first interval 

• 

Set orbit parameters to PATTAB 

values for current orbit interval 

Figure 3-3. TWPATW Flow Chart (Continued) 

EC R / D 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 Tip BIF-4-B10009-68 

Page 93 

CONTAK CONTAK 

Does current orbit interval begin 

prior to the latest allowable 

acquisition time? 

Yes 

( 

V 

Is the current estimate of 

vertical acquisition time within 

the bounds of the current orbit 

interval? 

V 

Increment or decrement the 

orbit interval counter as 

appropriate 

Yes 

Figure 3-3. TWPATW Flow Chart (Continued) 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 94 4E4E17 D 

CONTAK CONTAK 

Using PATTAB computed orbit parameters 

and current estimate of acquisition time, 

compute the vehicle in-plane angle from 

the ascending node, at the estimated 

acquisition time 

Using the current estimate of 

acquisition time to determine 

the location of the target 

w.r.t. the orbit, compute the 

vehicle in-plane angle from 

the ascending node for 

vertical acquisition 

( Is the magnitude of the difference 

between the vehicle in-plane angle at 

estimated acquisition time and the vehicle 

in-plane angle required for acquisition at 

the current estimated acquisition time 

less than a specified constant? 

EGT094: Convergence constant for in-plane 

angle 

No 

• Compute the rate of change 

of the vehicle in-plane angle 

• Compute the rte of change 

of the vehicle in-plane angle 

required for vertical acquistion 

Compute new estimate 

of vertical acquisition time 

Yes 

Figure 3-3. TWPATW Flow Chart (Continued) 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 131F-4-B10009-68 

Page 95 11C-RETID 

CONTAK CONTAK 

(

Have the maximum number of 

iterations for computation of 

acquisition time been made? 

Yes 

-11K 

Is the current target 

an old acquisition tape 

entry? 

Yes 

RETURN 

V 

(

Are multiple acquisitions per 

orbit period possible? 

Yes 

V 

Increment current estimated 

acquisition time by one 

vehicle period 

4 

Increment current estimated 

acquisition time by one orbit 

period 

Figure 3-3. TWPATW Flow Chart (Continued) 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 96 

CONTAK CONTAK 

(

Is the acquisition direction 

either NS or SN only? 

Yes RETURN 

( 

N 

• 

Are multiple acquisitions per 

orbit interval possible? 

No 

Set direction flag 

for NS only 

Yes 

RETURN 

Figure 3-3. TWPATW Flow Chart (Continued) 
Compute sun elevation angle 

NRO APPROVED FOR 

RELEASE 1 JULY 2015 'SEOREVD BIF-4-B10009-68 

Page 97 

CONTAK CONTAK 

( 

• 

Is sun elevation angle less than 

minimum allowable? 

SEV004 = Minimum sun angle 

N 

• 

Is the acquisition time within 

the bounds of the current orbit 

interval? 

Increment or decrement the 

orbit interval counter as 

appropriate 

Yes( 

Are multiple acquisitions per 

orbit interval possible? 

Figure 3-3. TWPATW Flow Chart (Continued) 
(

Is vehicle altitude greater than 

maximum allowable? 

SEV008 = Maximum vehicle altitude 

Compute velocity components of the 

target relative to the vehicle in 

the vehicle coordinate system 

NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 98 'SIC-RET/D 

CONTAK CONTAK 

Process change card tape 

to determine existence of 

change cards for current 

target and make any required 

target card data changes 

Compute vehicle altitude at 

vertical acquisition 

No 

Compute target obliquity at 

vertical acquisition 

K

Is obliquity less than 

maximum allowable for swath sort? 

Yes 

SEV003 = Maximum obliquity angle 

Figure 3-3. TWPATW Flow Chart (Continued) 

'SUREILD 
Save rev number and time 

of vertical acquisition 

) 

Are there any latitude band 

or time band delete cards? 

Yes 

V 

LATBAN 

Determine whether target is within 

a latitude band or is acquired within 

a time band which requires deletion 

Was the deleted acquisition by a 

time band or latitude band? 

No 

Yes 

NRO APPROVED FOR 

RELEASE 1 JULY 2015 BIF-4-B10009-68 'SELIETID Page 99 

CONTAK CONTAK 

Compute slant range 

Compute forward to vertical 

acquisition time difference 

Is slant range greater than 

maximum allowable? 

SEV007 = Maximum slant range 

Yes 

N 

Figure 3-3. TWPATW Flow Chart (Continued) 

-MEND 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 100 

111-RELTID 

CONTAK CONTAK 

Are there any delete 

cards? 

IrYes 

Process delete card 

tape and determine 

whether or not acquisition is to be deleted 

(

Is acquisition to be 

deleted? 

Yes 

001( 

Is the rev of acquisition Yes 

not equal to a specified 

rev of acquisition? 

No 

DTSTDU 

Store target acquisition data )

Figure 3-3. TWPATW Flow Chart (Continued) 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 101 

CONTAK CONTAK 

( Are deletion comments to 

be placed on Tape 8? 

EGT117 = Flag for deletion 

comments on tape 8 

Yes 

11/ 

Prepare tape 8 

deletion -..omment 

Figure 3-3. TWPATW Flow Chart (Continued) 

T/D 

'SEORET/D 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

'131F-4-B10009-68 

Page 102 --SECRETID 

CONTAK CONTAK 

(

No Are acquisitions to be 

Yes 

( Does acquisition found 

correspond to a SN pass? 

EGT111 = Constant added to inplane 

angle to determine pass 

direction 

SN only? 

•K Are acquisitions to 

be NS only? 

Yes 

Does acquisition found 

correspond to a NS pass? ) Yes 

( 

EGT111 = Constant subtracted 

from inplane angle to 

determine pass direction 

No 

Figure 3-3. TWPATW Flow Chart (Continued) 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

11-ORETID BIF-4-B10009-68 

Page 103 

3.4 TDMERGE 

3.4.1 Purpose 

After TWPATW has processed the target list, and the target and acquisition data for all acquired targets has been written on intermediate tapes, 

TDMERGE sorts the targets and writes the final time ordered acquisition 

tape. On option, new acquisition data can be stacked onto an existing 

acquisition tape. 

3.4.2 Input 

The input to TDMERGE consists of the intermediate acquisition tapes 

output by TWPATW. The acquisition data is described in Section 3.3. 

3.4.3 Output 

The output of TDMERGE is the final acquisition tape. The format of 

the entries on this tape is the same as that of the intermediate acquisition tape (see Section 3.3). The data contained on the acquisition tape 

include the full set of target card parameters. Also entered in the data 

block are the target acquisition parameters computed by TWPATW: 

a. Time of vertical acquisition 

b. The difference between earliest acquisition time and 

vertical acquisition time 

c. Parameters at vertical acquisition 

• Target obliquity 

• Altitude 

• Slant range 

• Sun elevation angle 

The final acquisition tape is time ordered on the basis of vertical 

acquisition time. 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 104 

IltRET/D 

3.4.4 Method 

If all the acquisitions from the intermediate acquisition tapes can 

be simultaneously placed in core (2800 acquisition entries maximum), the 

acquisitions are sorted by acquisition time, and the final acquisition tape 

is written. 

If the total number of acquisitions exceeds 2800, up to four intermediate merge tapes are generated, each containing a maximum of 2800 

acquisitions. These intermediate merge tapes are time ordered as they 

are generated. When all the acquisitions have been written on the merge 

tapes, these tapes are merged to form the final acquisition tape. 

If it is desired to stack current acquisitions behind the entries on 

an existing acquisition tape, then the final two significant data records 

of the existing acquisition tape are also merged with the intermediate 

acquisition tapes. No acquisition times of the current run may precede 

acquisition times on the existing acquisition tape. A flow chart of 

TDMERGE is shown in Figure 3-4. 

3.4.5 Restrictions 

The maximum number of acquired targets that can be processed by 

TDMERGE is 11,200. This limits the rev span that can be handled in a single 

run. As discussed in Section 2.1.1, the number of acquisitions per day is 

approximately one-fifth of the total target population (assuming 16 revs 

per day and a highly inclined orbit). For a target deck of 15,000 targets, 

approximately 3000 per day will be acquired. Therefore, a time period of 

about 3-1/2 days would be the maximum duration that could be considered in 

a single run. For rev spans covering a longer time period, the stack option 

can be employed. 
Yes ( Stack 

No 

Write label on 

acquisition tape 

No 

Yes 

STACK1 

Position acquisition 

tape before last two 

data records in two 

files 

(::: 

Read last two data 

records from acquisition tape 

case? 

Read 

tape DRDA 

10 

( End of file ) Yes 

on tape 10? 

No 

DMMII 

Read 

tape 

11 

NRO APPROVED FOR 

RELEASE 1 JULY 2015 

ITC-REVD 

TDMERGE 

Initialize - set 

flags I/O buffers 

Rewind 

I/O tapes 

BIF-4-B10009-68 

Page 105 

TDMERGE 

V 

(..„

Read intermediate 

acquisition tapes, 

(tapes 10 & 11) 

Figure 3-4. TDMERGE Flow Chart 

--SEGREYD 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 106 1ECRETID 

TDMERGE TDMERGE 

(

End of file 

on tape 10? 

No 

Move tape to 

buffer to 

large buffer 

1 

(

End of file)Yes 

on tape 11? 

IN° 

Move tape 11 

buffer to 

large buffer 

V 

Reset buffer 

counters 

Is large No 

buffer full? 

Yes 

Yes 

IF 

Move fillers 

into large 

buffer 

SORT 

Sort large buffer 

Figure 3-4. TDMERGE Flow Chart (Continued) 
B1F-4-B10009 '3 

Page 107 

TDMERGE 

D 

(

Should large buffer be 

written on intermediate 

merge tape? 

Yes 

Rewind 

intermediate 

merge tape 

4 

V 

Move large buffer 

into write buffer 

DMW10 

NRO APPROVED FOR 

RELEASE 1 JULY 2015 

TDMERGE 

Write 

acquisition 

tape record 

V 

Yes Is this a 

filler record? 

No 

Has all of large No 

buffer been written? 

Yes 

Was only acquisition 

tape written? 

Yes 

Are intermediate 

acquisition tapes 

written? 

Yes 

N 

Write end of 

file and rewind 

acquisition 00(: RETURN 

Figure 3-4. TDMERGE Flow Chart (Continued) 
Fill next buffer 

from large buffer 

NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 108 MILIEUD 

TDMERGE TDMERGE 

Is entire large 

buffer written? 

Yes 

s only acquisi- Yes 

tion tape written? 

N 

ONEXT 

Write end of 

file and rewind 

intermediate 

acquisition tape 

processed? 

)Yes entries been 

( Have all 

No 

(

Have all merge 

tapes been 

written? 

Yes 

c7) .

lop 

Figure 3-4. TDMERGE Flow Chart (Continued) 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

-1E-C-RETID BIF-4-B10009-68 

Page 109 

TDMERGE TDMERGE 

Set tapes 

written flags 

Merge tapes 

MOVE 

Move into 

output buffers 

Figure 3-4. TDMERGE Flow Chart (Continued) 

.••••••■ 

(REVERSE OF THIS PAGE LEFT BLANK) 

-SECRETED 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 --SEGRETID 131F-4-B10009-68 

Page 111 

is 

a. 

3.5 TWACQPR 

3.5.1 Purpose 

The subfunction TWACQPR reads either target acquisition records from 

the acquisition tape or COTPRIME records from the COTPRIME tape, depending 

upon the options requested and the calling sequence. The data are interpreted and reformatted to provide listable output. This output is ordered 

by rev number and by vertical acquisition time within each rev. 

3.5.2 Input 

On option, either an acquisition tape (see Section 3.3) or a COTPRIME 

tape (see Section 3.6) is employed as the primary input to TWACQPR. In 

addition, the setting of two File 8 parameters controls the usage of TWACQPR. 

The parameter EGT109 controls the printing of the acquisition data (1 = 

print, 0 = don't print). The printing of COTPRIME data is controlled by 

the summable print flag EGT134 as described in the TWONDER User's Manual 

(Reference 1). 

3.5.3 Output 

The output of TWACQPR consists of a formatted data display of information from the input tape. A sample of the acquisition output is provided 

in Table 3-12. Definitions of the column headers are provided in Table 3-13. 

The COTPRIME output, as shown in Table 3-14,consists of the acquisition 

data described in Table 3-12 plus additional parameters that define target 

worth and pointing information. These additional items are defined in 

Table 3-15. 

3.5.4 Method 

TWACQPR first determines the type of tape being input and then 

extracts appropriate information for output according to a predetermined 

format. The program consists of a set of logical decisions based upon 

fixed input and does not perform a mathematical or computational function. 

Flow charts describing the subfunction TWACQPR are provided in 

Figure 3-5 . 
D 

X to 

ON 

.-j 

0 >" L11 

0 -) 

XLIJ 

ELM 

< L1J 

OJ 

X Ill 

Z X 

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r maromm..4ommom.rmommomo.mommecconmocco.mcmc000 mmewm 000 

a L...L.--1,-L, L..L.E.L.t.,I.L.,t,.._LI,..u.L.L. L.L.I.L.L.u. 

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Table 3-

12. Acq

uisitionList 

,J 000o000000o0000000000000000 m 00000mo 0000000000oo 

2 0 

0 3) 

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0 

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0 0 IAIA M m MIA IAN IAN IA m in in lA tnininin in in lf% Mtn tf% in inWln in min in 'nal 

f-J in ea . I • n • • • • 0 • • • 0 a a • a ..... I 0 • m 0 a • 

✓
NRO APPROVED FOR 

RELEASE 1 JULY 2015 BIF-4-B10009-68 11G-RETID Page 113 

Table 3-13. Acquisition List Key 

Item Target Card Column Definition 

ID 38-47 Target identifier 

P1 1-2 Priority (inactive) 

SHD 10-12 Shade factor 

M 13 Photo mode weighting function 

D 4-5 Target diameter (ft x 10-1) 

W 35 Pitch weighting function 

SCC 56-58 Special category code 

S 21 Exposure setting sequence 

FL Two octal digits containing the 

following flags: 

28 Benchmark flag (208)* 

30 Mandatory primary flag (108)* 

29 Mandatory ATS view flag (048)* 

76 Visual intelligence flag (028)* 

27 Scan target flag (018)* 

*FL is formed by summing the octal 

codes indicated ( ) for those flags 

which are set. 

PR 31-32 Probability of activity (%) 

WF 35 Weather factor 

14-17 14-17 Target alter flag and specified 

rev number 

TIME none Time of vertical acquisition 

(system time, sec) 

LAT 60-66 Target latitude (deg, min,sec, 

north or south) 

LONG 67-74 Target longitude (deg,min,sec, 

east or west) 

, ALT 6-9 Target altitude (ft x 10-2) 

DWEL 33-34 Specified ATS view time 

(sec x 10-1) 

SA none Sun elevation angle (deg) 

OBL none Target obliquity (deg) 

WDP 24-26 Desired pitch (I- deg) 

P2 22-23 Priority (active) 

S/R none Target-vehicle slant range (n.mi.) 

VALT none Vehicle altitude (n.mi.) 
BIF-4-B10009-68 

Page 114 

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P a a Ca a at a a a a a a a 

Table 3-14. COTPRIME Outp

ut 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 BIF-4-B10009-68 1 Page 115 -EGRETLD 

4!. 

Table 3-15. COTPRIME* Key 

Item Definition 

Ti Initial acquisition time 

T2 Vertical acquisition time 

T3 Final acquisition time 

WI Inactive weight 

WA Active weight 

OM1 Obliquity at time Tl 

0M2 Obliquity at time T2 

0M3 Obliquity at time T3 

* The COTPRIME contains these parameters 

in addition to the acquisition data 

described in Table 3-12. 

a 
NROAPPROWF_T_Pc .D10009-68 RELEASE17a 215 

Page ii6 'SE6REIl D 

TWACQPR 

TWACQPR 

TWACQPR 

Initialize 

Set print 

flags 

SALONE 

Stand alone 

Set flags mode? 

N 

Neither acquisition 

tape or COTPRIME 

tape? 

N 

Yes 

Yes 

Rewind input 

tape 

Read 

input 

tape 

(End of file? 

N 

Yes Filler rec 

reached first? 

Yes 

V 

Header or No 

COTPRIME 

record? 

Yes 

V 

(

First time 

thru? 

( RETURN ) 

Yes 

Print header 

for output 

Figure 3-5. TWACQPR Flow Chart 

IENETID 

RETURN 
Ili Interrogate 

EGT109 and print 

on-line accordingly 

FORL. 

Header ) Yes 

record? 

N 

Print more 

header for 

output 

COTPRIME 

tape? 

Yes 

OPTIONS 

PRINT2 

Yes 

) 

Convert time to 

year, month, day 

SYSTEM 

BR180 

PAGEJ, OPTIONS 

Interrogate 

EGT109 and print 

on-line accordingly 

Print first 

line of page 

header 

Print page 

header 2nd line 

NRO APPROVED FOR 

RELEASE 1 JULY 2015 BIF-4-B10009-68 

Page 117 

TWACQPR TWACQPR 

V 

)

PAGEJ, OPTIONS, LINESK 

Interrogate EGT109 and 

print on-line accordingly 

Figure 3-5. TWACQPR Flow Chart (Continued) 

'SIOREUD 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 118 'STORM 

TWACQPR TWACQPR 

OPTIONS 

Interrogate EGT109 

and print on-line 

accordingly 

V 

Print page 

header 3rd line 

V 

OPTIONS 

Interrogate EGT109 

and print on-line 

accordingly 

V 

Filled 

page? 

]No 

) Yes 

COTPRIME No 

tape? 

) 

Yes 

cE) 

Figure 3-5. TWACQPR Flow Chart (Continued) 
(

Have 

filler rev? 

Yes 

Print one 

line 

Page 

filled? 

Yes 

Yes 

IEGRETa NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 119 

TWACQPR TWACQPR 

PRINT6 

Print rev 

sum 

LINESK, OPTIONS 

Interrograte EGT109 

and print on-line 

accordingly 

V 

End of file? Filler 

rec? 

Yes 

Interrogate EGT109 and )41 

print on-line accordingly 

LINESK 

tt 

• 

Print rev 

span summary 

OPTIONS, PAGEJ 

Interrogate EGT109 and 

print on-line accordingly 

( RETURN 

Figure 3-5. TWACQPR Flow Chart (Continued) 
OPTIONS 

Interrogate EGT109 

and print on-line 

accordingly 

COTPRIME 

tape? 

OPTIONS, LINESK 

Interrogate EGT109 and 

print on-line accordingly 

EXCH. 

lYes 

Print one 

line 

OPTIONS 

Interrogate EGT109 

and print on-line 

accordingly 

Print two 

lines 

NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 120 1-EIREP D 

TWACQPR TWACQPR 

Figure 3-5. TWACQPR Flow Chart (Continued) 

-111104 D 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

----SEGRETa BIF-4-B10009-68 

Page 121 

3.6 TWOPS 

3.6.1 Purpose 

The purpose of TWOPS is to compute precise pointing data and the 

active and inactive worths (weighted as a function of target obliquity at 

vertical acquisition), and to generate the COTPRIME tape which subsequently 

becomes the basic source of target information for the successor functions 

of TWONDER. 

3.6.2 Input 

The inputs required by TWOPS are as follows: 

a. Acquisition tape 

b. Ephemeris data 

3. THINGS and ALSO tables 

The acquisition tape required is as described in Section 3.3.3. The ephemeris data required are as described in Section 3.3.2. The THINGS and ALSO 

table items required are described in Table 3-16. 

3.6.3 Output 

The output of TWOPS is the COTPRIME tape. The parameters contained 

within each entry are described in Table 3-17. 

3.6.4 Method 

TWOPS reads in and checks each record of the acquisition tape one 

record at a time. After a record is read, each entry in that record is 

checked to ensure that the associated target is acquired within the input 

specified rev span; COMOPERA is called to compute the precise pointing data 

and weights to be stored on the COTPRIME tape. 

COMOPERA sets the forward, vertical, and aft main optics stereo 

a“gles to the values stored in table THINGS (SIGMAF, SIGMAV, and SIGMAA) 

which are specified through File 7 inputs, SEV063, SEV064, and SEV065, 

respectively. Initial estimates of the forward, vertical, and aft acquisition times are set based upon the vertical acquisition time and the difference between the vertical acquisition time and the forward acquisition 

SEPOREu D 
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0 

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0 

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CH 43 

0 

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3-1 

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wN 

0 41 z 

o 

Fi4 

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1-1 

0 

4-4 44 

0 0 CIS 

0) 

Interface Ta

ble Usa Res

et F

ile Definition 

Table 3-

16. 

THINGS a

nd ALSO Table Items Req

uir

ed by TWOPS 

a) 

Locations 

c

o 0 

44 a) g, Definition 

CO 

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BIF-4-B10009-68 

Page 122 

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BIF-4-B10009-68 

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Definition 

Table 3-17. COTPRIME Entry Data 

H 

O 

I 

cn 

Inactive worth 

a) 

r-I 

00 

Ca 

COTPRIME entry number 

Priority (inactive) 

Slant range Total I.D. cn 

Active worth Vehicle altitude 

Obliquity at forward acquisition Obliquity at aft acquisition 

Total acquisition time Obliquity at vertical acquisition 

Time at aft acquisition 

CY La 

0 

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BIF-4-B10009-68 

Page 124

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Scan target flag 

Photo mode weighting function 

Priority (active) 

Benchmark flag 

Mandatory primary flag Mandatory ATS view flag 

Desired pitch angle 

Exposure setting sequence 

Acquisition revnumber Directionof pass 

Pitch weighting function 

Target I.D. (first 8 characters) 

Definition 

Table 3-17. COTPRIME Entry Data (Continued) 

e: 

Csi 

,SEDREliD BIF-4-B10009-68 

Page 125 

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ather factor 

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BIF-4—B10009-68 

Page 126 ,s1DREV D 

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SE-GRW D 
BIF-4-B10009-68 

Page 127 

NRO APPROVED FOR 

RELEASE 1 JULY 2015 'MEV D 

time, both of which are computed through approximate methods in TWPATW, and 

stored on the acquisition tape. The CW array stored in table ALSO and set 

through File 8 parameters EGT251 through EGT260 is employed, using a linear 

interpolation technique, to determine the active and inactive target worths 

based upon target active and inactive priorities. Upon completing these 

operations COMOPERA calls the closed subroutines TITANIC and CONDUCT three 

times, once for each main optics stereo angle position. TITANIC computes 

the acquisition time and the target position and velocity in vehicle coordinates for the specified stereo angle. CONDUCT computes the slant range to 

the target and the target obliquity at the acquisition time of the specified 

stereo angle. 

Prior to calling TITANIC for the computation of the vertical and aft 

acquisition times, the initial estimates of these times, based upon the 

data on the acquisition tape, are biased to take advantage of the previous 

passes through TITANIC. The equations employed are as follows: 

t'SIGV = tSIGV (tF tSIGF) 

t

SIGA = 2(tv) - tF 

where 

t'SIGV = Initial estimate of vertical acquisition time 

used by TITANIC 

t'SIGA = Initial estimate of aft aquisition time used 

by TITANIC 

t = Forward acquisition time from acquisition tape SIGF 

t = Vertical acquisition time from acquisition tape SIGV 

t

F = TITANIC computed value of forward acquisition 

time 

t

V = TITANIC computed value of vertical acquisition 
NRO APPROVED FOR 

RELEASE1JULY2W5 

BIF-4-B10009-68 

Page 128 lEORELTID 

The closed subroutine TITANIC is the driver which controls the generation 

of precise pointing data. TITANIC accepts as input the stereo angle, the 

estimated acquisition time, the target latitude, longitude, and altitude, 

and a block of ephemeris data for the rev on which the target is acquired; 

TITANIC then calls subroutine COMPOSE to compute a precise acquisition 

time, and the target position and velocity in vehicle centered coordinates. 

COMPOSE calls procedures TNTERP, TOVER, TIRCOS, TSTACOR, TANGVEL, TSTAVEC 

and TSIGMA. 

TNTERP 

TNTERP obtains the vehicle state vector in the ECI coordinate system 

corresponding to the current estimated acquisition time. The origin of the 

ECI system is located at the center of the earth, the X axis points to the 

Vernal Equinox, the Z axis points up through the north pole, and the Y axes 

completes the right handed orthogonal system. The ephemeris data points 

which bound the time interval containing the current estimated acquisition 

time are found. The ECI position and velocity of the vehicle is then computed at precisely the current estimated acquisition time by a Lagrange 

interpolation technique between these points. 

TOVER 

TOVER computes the vehicle altitude and the direction cosines between 

goedetic vertical and the ECI coordinate axes. 

The earth's figure is defined by the surface S, where 

2 

2 2 z S =x +y + -1= 0, 

e e b2 

where x

e

, y

e

, z

e 

are the ECI coordinates of points on the earth's surface 

per unit equatorial radius and b is the ratio of the polar radius to the 

equatorial radius. 

The altitude vector, h, is defined by the equation 

VS 

h =r-rn = h 17-OS-T 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 BIF-4-B10009-68 

Page 129 -3ECIETID 

where r, - vehicle position = xe

- x

+ ye 

- 

+ ze

z 

r

- n'

nadir position = x

n

e

x 

+ y

n

e

y 

+ z

n

e

z 

h = scalar altitude 

IVS

VS 1 = unit vector normal to the earth's surface 

If the scalar parameter, k, is defined as follows: 

h 

k = 2 

Ivs I 

then the vehicle position and nadir position are related by the following 

equations: 

x 

X = 

n — 

l+k 

Yn = 

1+k 

z 

z = 

1+ k2 b 

Since the nadir point must be on the earth's surface, k must satisfy the 

quartic equation: 

2

+v

2 2

b

2 

S= x 

z 1 = 0 

(l+k)2 (17.,2+k)2 

A solution for k is obtained by starting with the circular earth solution 

(b = 1) 

1 2 2 2 , k

o 

= lix + y +z2 -1 
dS2 

= - 

dk l+k 

since [1 + S + z2 b

2 (1-b2) ]

(b2+k)3 . 

NRO APPROVED FOR 

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BIF-4-B10009-68 

Page 130 D 

and iterating as follows: 

Denoting kn + 1 = kn (A k)n 

then Sn +1nd = S + (Ak)n= 0 

S

n 

hence (A k)n= dS

d

- 

k

n 

then (Ak)n = 

1 (l+kn) Sn 

2 1 + S + z

2 b2 (1-b2) 

(b2

+kn)

3 

When k is determined, the altitude vector is given by 

kx ky kz 

h - 1 + k e + x 1 + k ey

e 

b

2 + k

z 

Defining 

(1-b2) 

(b2

+k) pz = x 2 2 

+ y

2 

+ z

2 (1-k)2 - (l+k) 1 + z2 

(b2

+k)2 

then the altitude and direction cosines are given by 

k 

h = 17TR Pz 

x 

Z

x PZ 

z y 

P Z 

z 1 + kl 

p

Z b

2

+ k 

Z

z 
NRO APPROVED FOR 

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Page 131 

TIRCOS 

TIRCOS computes the direction cosines between the vehicle centered 

coordinate axes and the ECI coordinate axes. The origin of the vehicle 

coordinate system is taken at the center of the vehicle, the Z axis points 

up along the instantaneous geodetic vertical, the Y axes is orthogonal to 

the orbit plane, the X axis lies in the orbit plane and completes a right 

handed orthogonal system. 

Thus 

- v x h 

e = 

Y 

e

- x

= e

y 

x e

z 

where 

e = direction cosines between vehicle y axis and 

y ECI coordinates 

e

- x

= direction cosines between vehicle x axis and 

ECI coordinates 

e

- z

= direction cosines between vehicle z axis and 

ECI coordinates (computed in TOVER) 

v = vehicle velocity vector in ECI coordinates 

h = vehicle altitude vector in ECI coordinate 

e = 1.17 x • 

y 

TSTACOR 

TSTACOR computes the target position and velocity in ECI coordinates 

at the current estimated acquisition time. 

The radius of the earth per unit equatorial radius at the station is 

given by 

4 2 1 1 + b tan e

s 

r

s 

- 

1 + b2 tan2 0

s 

-SteRETID 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 132 'SLEIREVD 

where 0s is the geodetic latitude of the station and b is that ratio of 

the polar radius to the equatorial radius. If the station altitude is 

given in terms of geodetic height, h

s

, then the ECI coordinates of the 

station are given by 

x = (r cos 6 + h cos e) cos a 

s s s s 

s 

s 

y = (r cos (5 + h cos0sin a 

S S S S S) S 

z = r sin (5 + h sin 0 

s s s S s 

where 

S

s 

= station declination (geocentric latitude) 

a

s 

= station right ascension (a +w

e

t +0 

s) 

g

a

o 

W = earth's rotation rate 

e 

0 = station longitude 

since 

tan

s 

= b2 tan 0

s 

cos ISs/ vi + b4 tan2 

sin

s vl + b4 tan / 

+ h

s 

cos 6

s 

cos a

s b2 tan2 OsI 

1 

Ys + b tan

s 

+ h

s 

cos O

s 

sin a

s 

g

o 

= right ascension of Greenwich at base time 

then 

and 

X

s 

1 

b

2 tan e 

1 
NRO APPROVED FOR BIF-4-B10009-68 

RELEASE 1 JULY 2015 SECRET /0 Page 133 

b

2 tan 6 

z - / s + h sin 0 

s V1 + b2 tan

2 (3 s s 

s 

The velocity components are determined by differentiation. 

X

s 

= - w

e

y

s 

s 

= w

e

x

s 

s 

= 0 

TANGVEL 

TANGVEL computes the components of the angular velocity of the vehicle 

coordinate system. 

The angular velocity of the vehicle centered coordinate system is 

determined from two conditions. First, the negative e axis must point 

at the instantaneous nadir position, and second, the inertial acceleration 

must have a zero component on the e axis. 

Starting with the equation for vehicle altitude, h which is the difference between the radius vector to the vehicle, r, and the radius vector 

to the vehicle nadir, rn 

= he = r- r

n 

and differentiating 

• _ _ _ 

h = h e + w x (he Z Z) = v - v

n 

where the angular velocity, w, is defined as follows: 

w=wX

e

X +wY e+we Y Z Z 

Thus v - v

n 

= hwYeX - hw

XeY + A e Z 

and - - (v - v

n

) . e Y 

w

X h

- 

(v - v

n

) . eX 

WY = 

-IMMO 

h 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 134 IECREi1D 

Using the same notation as defined in TOVER, the vector r - 7nis given by 

- - - kx ky kz 

r - r

n 

= h = x l+k ey 11 2.44c;z 

Differentiating 

d 

dt (7 - rn) = v - = 

[kk kx v

n 

e

x 

+ l+k 77752 

+ III__ I b2fcz 

l+k (l+k)2 e + 

[ 

b

2

+k (b2+k)2 e

z 

Since 

h - l+k pZ 

w

X = 

w = Y 

1 

- kY

x 

+ ;TY 

xY 

y 

l+k ZY 

b

2

(l+k) 

P Z 

+ 

z 

y b

2

+k 

x 

+ yY zY 

z 

• l+k 

k(l+k)pz 

1 • + yX 

x 

[kX 

(b2+k)2 

p + z X 

z

b

2

+k 

b2(1+k)2 

+ k(l+k)pz xX

x 

+ yX + zX 

z (b2

+k)2 

then 

Using the relations 

kY

x 

+ ;TYy + ZYz = 0 

xY

x 

+ yY + zY

z 

= - zY

y z 

xX

x 

+ yXy + zX

z 

= - zX

z 

[ 1-b 

b

2

+k 

b

2

+k 

[1-b2 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 BIF-4-B10009-68 

Page 135 

then 

wX 

w = Y 

- Yz kz 1-b2 

wx 

- 

b

2

+k b

2 

kx + yx + Zx 

x Y z 

[ 

+k 

X

z 

pZ

1 

y

z 

k is evaluated by differentiating the equation 

x

2 

+ y

2 

z

2

b

2 

= 1 

(1+k)2 (b2

+k)2 

to obtain 

0 

x;(4-yir b`z 

(1+k)2 (b2

+k)2 

x2+ 

2 b

2

z

2 

(l+k)3 (b2

+k)3 

then p prX 

• kz Y Z z 

z 

- 

b

2

+k = x2+y2+b2z

2 (l+k)3 

(b2

+k)3 

since 

2 + b 2 

 p

z 

2 

x

2 

+ y

2 + b2

z

2 (1-k)3 k(l+k) 

(b2+k)3 b

2

+k 

p

Y

p

Z

X

z

Y

z

(1-b2

) 

w

X b

2

p

2 + k(l+k)2 

The determination of w is based on the condition that the inertial 

acceleration must have a zero component on the eyaxis. The inertial 

velocity in the vehicle centered system is given by 

. • v = (xX

x 

+ yX + zX

z

) e

x 

+ (xZ

x 

+ yZ + zz

z

) eZ 

k - 

then 

-SEC-RERD 
X -X 

S 

X 

Y 

X X X X y z 

Ys 

Y y y 

x y z 

Z Z Z Z X y z 

NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 136 -SECIETID 

Differentiating to obtain the acceleration 

a dt 

d • • • • • 

= (xX

x 

 + yX + x e

z ) eX dt + — (xZ

x 

 + yZ +

z

) e

d Z 

+ wxv 

For the Y component to be zero 

• 

xZ

x 

+ yZ + zZ y 

z 

wz wx Xx

x 

+ STx + ix

y z 

TSTAVEC 

TSTAVEC computes the components of target position and velocity in 

the vehicle coordinate system. 

The direction cosines computed in TOVER and TIRCOS are used to transform the vector difference between the station position and vehicle position 

to the vehicle system. 

Since 

1-b2 

xX

x 

+ yX + zX y 

z 

= - z 2 X

z b +k 

1-b2 

xY

x 

 + yY

y 

 + zY

z 

= - z 2 Y

z b +k 

1-b2 

xZ

x 

+ yZ + zZ y z = p2 - z 2 Zz 

b +k 
then 

1-b2 

X = xsXx+ ysXy+ (zs + z 2 ) Xx 

b +k 

1-b2 

Y =xY

x 

 +yY+ (zs+z 2 ) Yx 

s s y b +k 

1-b2 

Z =x

s

Zx +ysZy + (zs+z 2 ) Zx- ox 

b +k 

The apparent velocity of the station relative to the vehicle is obtained by 

differentiating the station position vector. 

Denoting the station position vector by R

s 

where 

R

s

=r

s 

-r=XeX +Ye +Ze Z 

then 

dRs =Ve +Ve +Ve +wx R

s 

— — — 

XX YY ZZ 

Thus 

dt 

NRO APPROVED FOR 

RELEASE 1 JULY 2015 BIF-4-B10009-68 

Page 137 

v

z 

V 

v

x 

X 

x 

 X X 

y z 

Y 

x 

 Y Y 

y z 

Z 

x 

 Z Z 

Y z 

X -X 

• Ys -37 

z -z 

w

Z Y -wY Z 

wxz -wZX 

wyX - wxY 

ET/D 

Since 

z

s 

= 0 

• • • xY

x 

+ yY + zY

z 

= 0 

y 

then 

. . 

. . 

• 

V

X = (x

s 

-x) X

x 

+ (y

s 

-y) X

y 

-2X

z 

w

Z

Y - w Z 

V

Y = x

s

Y

x 

+ y

s

Y

y 

+ wX

Z - w

z

X 

. . 

. . • V = (x

s

-x) Z

x 

+ (y-y) Z - zZ

z 

 + wYX - wX Y 

IfeRET/D 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-810009-68 

Page 138 SECRET/D 

TSIGMA 

TSIGMA computes an improved estimate of the time at which the stereo 

angle is equal to the specified stereo angle. TSIGMA computes the actual 

stereo angle at the new estimated acquisition. If the difference between 

this actual stereo angle and the specified stereo is less than ESIG, a convergence constant stored in table THINGS, the new estimate of acquisition 

time is taken as the required output; if the difference is greater than 

ESIG the entire computational cycle of COMPOSE is repeated using the TSIGMA 

value as the current estimated acquisition time. THINGS table item ESIG is 

specified through File 8 parameter EGT095. 

The stereo angle, E, and the time rate of change of stereo angle, E, 

are computed from the equations 

= - tan 1 X 

Y + Z2 

E - X(YV + ZV

z

) - V

x

(Y2 + Z2) 

(X2 + Y2 + Z2

)(Y2 + Z2

) 1/2 

where X, Y, Z are the station position coordinates and VX, VY' VZ are the 

station apparent velocity components relative to the vehicle in the vehicle 

centered coordinate system. 

If the computed value for E is different than a desired value, E0, 

then an estimate of the time for which E = E

o 

can be computed using the 

equations 

t

n+1 = to 

+ (At)

n 

(At)nE

o 

- E

n 

E

n 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

-1-EGREVD 

BIF-4-B10009-68 

Page 139 

This technique will not converge if the initial time estimate is 

greatly in error. To insure convergence in all cases it is necessary to 

provide bounds on the time increment At. 

The proper bounding procedure can be determined by solving for the 

approximate variation in stereo angle with time as the vehicle rotates 

around the earth with the stereo mirror tracking an earth-fixed station. 

For this analysis it will be assumed that the vehicle is in a circular 

orbit and the Y coordinate of the station is zero. Furthermore, the rotation of the earth about the polar axis will be disregarded. Defining y 

as the apparent angle of rotation of the earth below a stationary vehicle 

then 

X = R sing 

Z = - {(R+h) - R cos y] 

and 

tan E - R sing 

h + R (1-cosy) 

27 

y = — (t-to) 

V 

where p

V = period of the vehicle 

t

o = time at which station is at vehicle nadir 

For a low altitude circular orbit 

p

V= 271. 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 140 IECREVD 

The, maximum and minimum values of E are obtained when 

cosy = 

R 

h+R 

which can be approximated by 

2h 

= R 

hence 

tan E

max 

R 

2h 

min 

ThetimeintervalbetweenEmax andEmin is given by 

AtE = 2 = 23/2 .\,/ h 

The maximum increment in time is set at half this time interval 

(At)

max 

2h 

g 

TSIGMA is the last procedure within COMPOSE. Subsequent to the operation of TITANIC and COMPOSE to determine the acquisition time for the 

specified stereo angle, COMOPERA calls subroutine CONDUCT to compute the 

slant range and target obliquity at the specified stereo angle. CONDUCT 

consists basically of two equations 

Obliquity = tan 1 (Y/-Z) 

Slant Range = X2 + Y2 + Z2 

where X, Y, Z = target location in vehicle centered 

coordinates 
NRO APPROVED FOR 

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Page 141 

CONDUCT returns program control to COMOPERA. COMOPERA computes the obliquity 

weighting factor for the target obliquity corresponding to the current stereo 

angle, and determines whether pointing data has been generated for all three 

stereo angles (forward, vertical, and aft). If pointing data has not been 

generated for the three stereo angles, COMOPERA recycles through TITANIC 

and CONDUCT for the next stereo angle. 

The following equation is used to compute the obliquity weighting 

factor: 

Obliquity Weighting Factor = cosn(Obliquity-Ref. Obliquity) 

where 

Ref. Obliquity = THINGS table item, OBLZRO, specified reference 

obliquity in calculation of obliquity weighting 

factor 

n = THINGS table item, NOBL, cosine exponent for 

obliquity weighting 

THINGS table items OBLZRO and NOBL are specified through File 8 parameters 

EGT044 and EGT140, respectively. 

At the completion of the generation of pointing data for the three 

stereo angles, COMOPERA computes the obliquity weighted active and inactive 

worths, determines whether or not the target obliquity is within the main 

optics obliquity constraints, operates as a target density filter, prepares 

a COTPRIME entry for the target, and returns control to TWOPS. TWOPS determines whether any unprocessed entries remain on the input acquisition tape. 

Each of the unprocessed entries which remain is in turn processed through 

the computational cycle described above. If all the acquisition tape 

entries have been processed, TWOPS completes the COTPRIME tape and returns 

control to TWONDER2. 

The final computations within COMOPERA proceed as described in the 

following text. 

COMOPERA obliquity weights the active and inactive worths of each 

target through multiplication of those worths by the value of the obliquity 

weighting factor, computed for the target obliquity at vertical acquisition. 

--SteRETiD 
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The target obliquity at vertical acquisition is compared to THINGS 

table item OMEGMX. If the target obliquity is greater than OMEGMX the target is deleted. OMEGMX is specified through File 8 parameter EGT147. 

The last operation performed by COMOPERA is to delete those targets 

which fail to pass through a target density filter. The filter compares the 

basic worth of the target in process with the basic worths of targets 

already stored in the COTPRIME. The basic worth of each target is computed 

as follows: 

Basic Worth = WI (1 - P

A

) + WA (PA

) 

where 

W

I 

= the obliquity weighted inactive worth of the target 

WA= the obliquity weighted active worth of the target 

PA= probability of activity 

The probability of activity is a target card parameter which is stored 

on the acquisition tape. If the probability of activity on the acquisition 

tape for the current target is equal to zero, COMOPERA sets the probability 

of activity equal to THINGS table item PROBA. PROBA is specified through 

File 8 parameter EGT922. The density filter operates as follows: 

The previously generated COTPRIME entries are searched to find all 

those entries whose vertical acquisition time occurs within a specified 

number of seconds (THINGS table item DTIME, EGT937) before the vertical 

acquisition time of the current target. If there are too many COTPRIME 

entries among those found whose basic worth is greater than the basic worth 

of the current target, the current target is deleted (THINGS table item 

DNUM, EGT936, is the maximum number of higher worth targets allowed in time 

interval DTIME before deleting). 

Flow charts illustrating the computational processes within TWOPS are 

presented as Figure 3-6. 

ET/D 
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Page 143 

TWOPS TWOPS 

TWOPS 

TWOPS 

INITIALIZATION 

• Rewind input and output tapes 

• Set buffer sizes 

• Clear COTPRIME table entries 

Initialize counters 

• 

Read in and check one 

record of acquisition 

tape 

• 

( Was an end of file Yes 

)1 

Pick up next acquisition 

tape entry in acq record 

read? 

Is entry a filler 

entry? 

Yes 

N 

( 

• 

)Yes Does rev of acquisition 

occur before specified 

rev span? 

N 

• 

Figure 3-6. TWOPS Flow Chart 
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Page 144 

( occur later than specified 

rev span? 

Does rev of acquisition ) Yes 

TWOPS TWOPS 

V 

Set up COTPRIME entry 

for acquisition tape entry 

in process 

Figure 3-6. TWOPS Flow Chart (Continued) 

Wrap-up 

COTPRIME 

tape 1.1 

COMOPERA 

Compute active and inactive worths 

based upon active and inactive 

priorities 

Set forward, vertical, and aft 

stereo angles 

Set initial estimates of forward, 

vertical, and aft acquisition times 

TITANIC 

Compute acquisition times, and 

target position and velocity in 

vehicle coordinates for forward 

vertical, and aft acquisitions 

CONDUCT 

Compute slant range and 

obliquity at forward, vertical 

and aft acquisitions 
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TWOPS TWOPS 

Is target obliquity at vertical 

( acquisition within specified limits? No • 

Yes 

Delete 

COTPRIME 

entry 

Does the target satisfy No 

Delete 

target density/worth COTPRIME 

constraints? entry 

Yes 

(

Does COTPRIME entry 

fill a COTPRIME record? 

Yes 

Write COTPRIME 

record on tape 

Figure 3-6. TWOPS Flow Chart (Continued) 
TITANIC 

Compute acquisition time and target 

position and velocity in vehicle 

coordinates for stereo angle corresponding to current stereo angle index. 

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Page 146 --SERETID 

COMOPERA COMOPERA 

COMOPERA 

• Set forward, vertical, and aft 

main optics stereo angles 

SEV063 = Maximum forward stereo 

angle for main optics 

SEV064 = Vertical stereo angle 

for main optics 

SEV065 = Maximum aft stereo 

angle for main optics 

• Set initial estimates of forward, 

vertical, and aft acquisition times 

based on acquisition tape values 

Compute active and inactive worths 

based upon active and inactive priorities 

EGT251 to 260 = Target worth as a function 

of priority 

• 

Set stereo angle index to correspond 

to forward stereo angle 

• 

Set estimate of acquisition time to be used by 

TITANIC for stereo angle corresponding to current 

stereo angle index. If not for forward stereo angle 

adjust initial estimate to reflect acquisitions 

times previously computed by TITANIC 

Figure 3-6. TWOPS Flow Chart (Continued) 

-SEGRET/D 
e 

( Did TITANIC computations Yes 

converge? 

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COMOPERA COMOPERA 

V 

(

Is stereo angle index set Yes 

No 

Delete temporary entries made 

for forward or forward and 

vertical stereo angles 

( RETURN 

for forward stereo angle? 

10.(: RETURN 

2. 

CONDUCT 

Compute slant range and 

obliquity corresponding to 

current stereo angle 

Compute obliquity weighting factor 

for obliquity corresponding to 

current stereo angle 

.EGT140 = Cosine 2 exponent for 

obliquity weighting 

EGT044 = Specified reference 

obliquity in calculation 

of the obliquity weighting factor 

Figure 3-6. TWOPS Flow Chart (Continued) 

D 
Set temporary entries in 

COTPRIME corresponding to 

current stereo angle 

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itCitEILD 

COMOPERA COMOPERA 

(

Is stereo angle index set 

for forward or vertical 

stereo angles? 

Yes 

Set stereo angle index 

for next stereo angle 

Figure 3-6. TWOPS Flow Chart (Continued) 
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Page 149 

COMOPERA COMOPERA 

Weight active and inactive worths 

using obliquity weighting factor 

computed for vertical stereo 

angle acquisition 

7 

Set up COTPRIME entry for 

acquisition tape entry in 

process 

Is obliquity at vertical 

acquisition within specified 

limits? 

EGT147 = Maximum obliquity 

angle 

Yes 

No 

• 

Delete COTPRIME 

entry 

Are deletion comments to be 

placed on Tape 8? 

EGT117 = Flag for deletion comments 

on Tape 8 

Yes 

• 

Set up obliquity 

delete comment for 

Tape 8 

( RETURN 

Figure 3-6. TWOPS Flow Chart (Continued) 

D 

( RETURN 
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Page 150 

--MEW 

COMOPERA COMOPERA 

(

Is current target a 

mandatory main optics or a 

mandatory ATS target? 

Yes 

No 

(

Is probability of activity on 

acquisition tape for current 

target equal to zero? 

Yes 

• 

Set probability of activity 

equal to specified value 

EGT922 = Probability of activity 

• 

Compute basic target worth based upon 

obliquity weighted active and inactive 

worths, and the probability of activity 

( 

Search previously generated COTPRIME 

entries to find all those entries whose 

vertical acquisition time occurs within 

a specified number of seconds before the 

vertical acquisition time of the current 

COTPRIME entry 

EGT937 = Time interval in density filter 

1 

Are there too many COTPRIME entries among those 

found above whose worth is greater than the worth 

of the current COTPRIME entry? 

EGT963 = Maximum number of higher worth targets 

allowed in time interval before deleting 

target by density filter 

Figure 3-6. TWOPS Flow Chart (Continued) 

"IEDRE-1/D 
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Page 151 

COMOPERA COMOPERA 

• 

( 

Delete current COTPRIME 

entry 

• 

Are deletion comments to be 

placed on Tape 8? 

EGT117 = Flag for deletion 

comments on Tape 8 

Yes 

• 

Set up density delete 

comment for Tape 8 

( RETURN ) 

( Does current COTPRIME No 

entry fill an COTPRIME 

record? 

Yes 

• 

Write COTPRIME 

record on tape 

RETURN 2) 

Figure 3-6. TWOPS Flow Chart (Continued) 

-SfERETID 
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Page 152 11-C-RETAD 

TITANIC TITANIC 

( TITANIC ) 

COMPOSE 

V 

TNTERP 

Computes vehicle coordinates 

in the ECI coordinate system 

corresponding to the estimated 

acquisition time 

• 

TOVER 

Computes the vehicle altitude 

and the direction cosines 

between geodetic vertical and 

the ECI coordinate axes 

TIRCOS 

Computes the vehicle 

altitude and the direction 

cosines between the vehicle 

X and Y axes and the coordinate axes 

V 

TSTACOR 

Computes the target 

position and velocity in 

ECI coordinates 

Figure 3-6. TWOPS Flow Chart (Continued) 

-"Steffy D 
TANGVEL 

Computes the components 

of angular velocity of the 

vehicle coordinate system 

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Page 153 

TITANIC TITANIC 

• 

TSTAVEC 

Computes the components of 

target position and velocity 

in the vehicle coordinate system 

• 

TSIGMA 

Computes the time of the target 

acquisition for the specified 

pitch angle 

1 

• 

( RETURN ) 

Figure 3-6. TWOPS Flow Chart (Continued) 
KI Is correction less than a 

specified convergence constant? 

EGT093: Convergence constant used 

in iteration for intersection 

of optical axis with earth's 

surface 

Compute vehicle vertical 

altitude 

Compute direction cosines 

between geodetic vertical 

and ECI coordinates 

lirYes 

No 

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'SUIRETID 

TOVER TOVER 

TOVER 

1 

Compute location of intersection of 

vehicle optical axis with surface of 

the earth based on ECI coordinates of 

vehicle at vertical acquisition of 

target computed in TWPATW assuming 

spherical earth 

Compute correction for 

location of intersection 

for oblate earth 

01 

Recompute 

 intersection 

location 

( RETURN ) 

Figure 3-6. TWOPS Flow Chart (Continued) 
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Page 155 

........ ..., . 

CONDUCT CONDUCT 

• Compute target obliquity 

• Compute slant range 

......---.. 

Figure 3-6. TWOPS Flow Chart (Continued) 
• 

Set flag to indicate 

current estimate is 

the required output 

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. SEC-RELTID 

TSIGMA TSIGMA 

TSIGMA 

• 

Compute estimate of the 

time of target acquisition 

for the specified stereo 

angle. 

• 

Compute stereo angle at 

estimated acquisition time 

• 

Is difference between specified stereo 

angle and stereo angle correspondthg 

estimated acquisition time less than 

specified convergence constant? 

EGT095: Constant for control of 

iteration on stereo angle 

( 

to 

a No the time of 

of 

acquisition 

stereo 

Oi

Recompute estimate 

of the specified 

angle 

Yes 

( RETURN ) 

Figure 3-6. TWOPS Flow Chart (Continued) 
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Page 157 

ti 

3.7 TWEEDOFF 

3.7.1 Purpose 

The subfunction TWEEDOFF acts as a preprocessor for the main optics 

algorithm (TWMOSP). The basic functions performed by TWEEDOFF are: 

a. Abstraction of the information required by the main optics 

target selection algorithm (TWMOSP) from the COTPRIME. 

This information is then tabulated in the MOCOT. 

b. Provision of a means of limiting the number or targets 

that must be considered by TWMOSP. This is accomplished 

by means of either a priority filter or a priority/target 

density filter. 

c. Determination of the number of targets which can be considered as predecessor candidates for each target in 

TWMOSP. 

d. Setting of the basic weight of each target to be considered by TWMOSP to be either its inactive or its 

expected worth, depending upon a File 8 input parameter. 

3.7.2 Input 

The target specific information required by TWEEDOFF is obtained from 

the COTPRIME Table (see Section 3.6.3). File 7 and File 8 parameters used 

by TWEEDOFF and located in table THINGS are depicted in Table 3-18. Input 

arrays located in table ALSO are provided in Table 3-19. 

3.7.3 Output 

The output of TWEEDOFF is contained in the MOCOT Table. This table 

provides four words of information about each target as shown in Table 3-20. 

This information is required by the main optics algorithm (TWMOSP) in order 

to determine the optimal strategy for main optics photography. 

3.7.4 Method 

The following sections describe the computations included in this 

subfunction. In addition to performing these computations, the subfunction 

TWEEDOFF abstracts target specific information from the COTPRIME for entry 

in the MOCOT. 
Ma

ximumo

bliquity angle 

C-1 

.4441 

a. 

CO 

sa 

00 

0 

4-) 

0 

a. 

$.4 0 

C 

O 

4.1 

CO 

O 0

seq

uence 

Definition 

0) 

0 0 rl H 

0 > z 

0 0 

00 0 4.4 

4.4 

H U 

it 

9-4 4.1 0 

a) (0 

c0 

>4 

al CO 

0 0 00 04 

H H <4 H 

a4 El 0 p4 , H t-a 

04 

1-1 14 

A 

G.1 

A 

W r4 

A 

1 41 

CO 

•O 

U Cl) 

4-4 c) O Co 

4-1 4-4 is 0 

O. 4..) ,-.1 

04 4.4 

Co 0 U 04 

c.) 0 

H 0 

‘) H a 0 

0 CO 0 H 

0 0 cc) 

0 )4 

H 0 

Cd 4-1 0) 0 

0 HI 14-4 a) 

a) 4 H 

HI CI 0.1 ,n 

O 4:10 4-I r....1 0 

44 0 00 4.4 

a) al 00 c0 a) 0 

U H 0 a) r-1 L'ICL bp 

4-1 

4.4 

9-1C0 C.) 41.4 C0 r-1 4H 

4-14-1 Cl) /-14-1HI 

•1441 HI 0 C1) 

00 on a Co 00 00 $.4 ,--) 

0 0 0 0 Co 

4-1 44-1 Cd ,.0 .1-1 •r1 al 

4-1 c.) 4•J 

CD

3 

 c0)) H 4.) a) cll ,--) .-

1-1

I 

r-1 r-1 W 44 HI Hi CW 0 

CI) 0) A P4 cn 0) q ).4 

to 

) 

co 'CO cn 

(14 04 

44 R4 Ex4 

O 0 0 0 

4-1 4-1 

0 01 

Lri 

cr, 

E-1 

CD 0 

c.4 

W 

4r) 

cr) rn 

H E-1 

0 0 

r. 

7.; 

Interface Table Usa 

Table 3-

19. F

ile 8 Parameters Us

ed in TWEEDOFF Located in Ta

ble ALSO 

Res

et F

ile Definition 

Definition 

Definition 

<4 

0 1-) 

Location 

a) 

CO 

and File 8 Pa

ram

eters Us

ed in TWEEDOFF Located in Ta

ble THINGS 

a) H 

•14.4 Table 3-18. 

a) Interface Table Usa 

File Definition 

a) 

a) 

04 

131F-4-B10009-68 

Page 158 ,SEDITO D 

c.) 

a) 

0.) 

(I) 

co 

0 0 

0 4-I '-0 I. 

Lf1 in 0 0 N. CO 

44 r-I 44 r-I 44 C',1 44 VI cr.., r■ W1. 

H 

0 H 

H 

0 Z 4.1 M CD Z 

2!)01 0 3 A 14 I-4 

H cn r./) Z X 0 

0 V) H H 0 0 Z Z 

114 

$.4 

0 

I 4-4 aJ 0 

$.4 0 

0 0 

HI

1) U O 4-1 

14-4 0 H H 

C13 co 

a) .40

0) 

0 

H 0 a) 

00 a) 0 'CO 

0 $.4 4) 

CO a) m 4.J 4.4 4-) a) 

0 o 0 .Co 00 a) t).0 (.1 $-4 CO 

0 44-1 41-1 CO 0 

0) 

9-1 3 

0 11) 4.) 

4-4 a. 4-1 

co 4_1 o a) 

ci)

u .4-) CU H 

'0) ca cn 0 .):3 H $.4 ,-4 u .4-1 .,1 co (1.) 

Cd 0 41-1 4-1 CCI CA 

C/) U a. L,0 1"-) Cj 0 H1 co 

0 u al 0 44 0 H u 

4.4 .ri 44 H co .ri 

0 R. U 4,1 

cct 4-)a) 0 O -o El 

el e co).) 0 

.1.4 g w a) H 0 

X I< 3 -0 X 4-4 

CO CO 0 0 H CO CO 

Z 0 H 441-1 Co Z 0 

-., 

cn 

00 00 'CO. H t) 00 c.) 

cll a) 0 a) a) Cl) 

'CO 'CO 0 E-1u) 'CO Co 

O 

cx4 44 R4 

-44 H 

H 

O 

De

finition 

01 --.1- kr) s.0 N. CO 

s. 0 sn --.1' •.-1- .--1- ---.1- 

0 0 H H H H 

> > H H H H 

44 44 CD CD CCD cD 

C/) co C4 rz.1 fr.1 41 

_SECREV 
those tarentry number conflict with the 

E-4 0 

C.) 

0 

Z numberof 

for scoring function. 

-0 a) 

to Shape to be 

COTPRIME entry numberof targ

et. 

Desir

ed photographic mode. 

a) a) ro 

to to 

0 0 

0 H 

tf) 

stereo angle for photography. 

0 

a) 

to 

ro 

00 

a) 

-0 

Definition 

MOCOT Table 

to 

r4 Declaration 

1-1 

O 

1-) 

3 

z 

frominitial acquisition 

Initial acq

uisition time of target 

4-1 g 

a)0 

00 •rl 

)-1 

ttl 

to

O 

0 04 

ro 

Obliquity at MT1 

Total time 

to final 

O r4 

4.) 

ro 

4-) . 

Ea g 0 

4-1 4.) 

E 

0 0 

•?-1 

4.1 

cr) 

H 

0 cr 

u 

0 0 

1-1 

0 

(1.) 

00

0 

al 6 

H 

O4.c 

0 

CO 

Cr) 

Cs) 

The sma

llest 

Itr/REk/ D 

a) 

4-) 4 -0 4.) 

+J-0 H 

H 

td -0 

0 a) g 

*ri 0 4-) $.4 

4-1 C) 

)-1 4 4.) 

0 0 4_c H 

a'0 

0 

W 0D G rd 

4-1 4.1 0 

.0 0 a) 

$.4 a) 4_1 I, 

0 

ct) 4 0 ro 

4-1 4..1 

'0 

CO 4-1 0 4-1 

',

I 0 CD 0 

a. 

4-) .0 a) 

" $4 • 

0 0 4 0 

0 4-1 4.) 

•H 

4-1 Q) 0 (1) •H 

0 H rl 4.) 

4-I 0 4.1 g 

t) 61-1 (.) ro 

0 P. 0 cd G 44.4 

H 4 4-1 0 

BIF-4—B10009-68 

Page 159 

4-1 Li-i c.) 

0H H 

)4 4-4 

(1) 0 

ro E 0 

o 0 

›, 

).4 

.61 

0 

ai 

ai 0 

0 4-1 Z )4 co 0 H ..--, 4-■ H 

.0 4 

0 I+4 Z a) u 44 

H

bp .'l 0 4 "-I 0 44 

4.1 C..) Ca 3.0 a) 0 H 

Ca 00 Z a) 

a) cd u., 4 a) cri 

00 4.) -,-1 H Oa 4_1 

be either 

0 0 csi 

N 

sso 

Cr) 

0 

0 

Cr) 

k„0 

H H H 

Cr.1 a LT.1 A g E_4 

0 0 

z 

iFweRrITD 
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Page 160 'SEOREILD 

3.7.4.1 Filtering 

The filtering of low priority targets is accomplished through the use 

of File 8 parameters MOWGT (EGT145) and MODENS (EGT146). MOGWT is the lowest effective weight that will be considered in the main optics selection. 

Those targets having a weight, MWI, less than MOWGT are not entered in the 

MOCOT table. The parameter MODENS is the maximum allowable target density 

measured in targets per second. When it is determined that the target density exceeds this value, the lowest worth (highest numerical priority) targets are selectively eliminated until the allowable density is attained. 

There is currently a more effective filter in TWOPS. The target density 

filter was designed in the earlier stages of program development and 

although still in use the majority of the target density filtering is done 

in TWOPS. 

A fixed number of targets (200) is used in the determination of target 

density. This number corresponds to the number of targets in a COTPRIME 

record and was used for convenience. The allowable number of targets, TOTNO, 

is calculated from the equation 

TOTNO = At x MODENS 

where 

At = TT1 (199) - TT1 (0) 

TT1 (199) = First acquisition time of the last target 

in the record 

TT1 (0) = First acquisition time of the first target 

in the record where TT1 is a COTPRIME 

parameter. 

When the allowable number of targets, TOTNO, is found to be less than 

the 200 targets available in a COTPRIME record, the lowest worth targets are 

selectively deleted. 
NRO APPROVED FOR 

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Page 161 'METZ D 

3.7.4.2 MOCOT Predecessor Range 

Another major function of TWEEDOFF is the determination of the number 

of targets that must be considered as possible immediate predecessors by 

the TWMOSP selection algorithm. This problem can be visualized as is shown 

in Figure 3-7. Target A, having a first acquisition time of MT1, is shown 

on an obliquity-time swath plot. Three regions can then be defined which 

correspond to total conflict, partial conflict, and no conflict. The times 

LUTM and LUTN define the boundaries between these regions such that all 

targets having a first acquisition time between LUTM and LUTN are in the 

partial conflict region. These times are determined using the following 

equations: 

LUTM - 

121 + 2max 

+ (t3 

- t1) cos Q/cosmax + S

max 

LUTN = (t3 - t1

) - 2P min + S . 

nun Ila n 

MR 

(A+B) (1 -Pmin) (A+B) (Pmin+ Smin) 

MP * T

max 

(t3 - t1

) 

The quanties 0, tl, and t3 are, respectively, the obliquity, first acquision time, and last acquisition time of the target being considered. These 

items are obtained from the COTPRIME. The remaining quantities define the 

physical limitations. These are defined as follows: 

0 

max 

maximum obliquity 

A maximum forward stereo angle 

B maximum aft stereo angle 

MP maximum pitch slewing rate 

MR maximum roll slewing rate 

S

max 

maximum settling time 

Smin minimum settling time 

P

min minimum photographic sequence duration 

iferREIC 
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Page 162 -- SECTREVD 

B (MTM) 

C 

LUTN 

MT1 

A 

D (MTN) 

— LIJTM 

Direction of Trav

el 

0 bo a) Partial Conflict 

Figure 3-7. Definition of MTM and MTN 
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Page 163 

Using these parameters, the above equations conservatively determine the 

region of partial conflict. The quantities Qmax, A, B, and Pminare 

obtained directly from the input parameters EGT147, SEV063, SEV065, and 

EGT148, respectively. 

The settling times and maneuvering rates ire obtained from the input 

parameters that define main optics maneuvering capability (EGT950 to 

EGT965). 

After the times LUTM and LUTN have been determined for a particular 

target (A), the quantities MTM and MTN can be determined. MTM is the MOCOT 

entry number of the earliest target (based on first acquisition time) in the 

partial conflict region, and MTN is the MOCOT entry number of the latest 

target in the partial conflict region. For the example shown in Figure 3-7, 

MTM would be set equal to the MOCOT entry number of target B and MTN would 

be the MOCOT entry number of target D. 

3.7.4.3 Target Worth 

The target weight or worth (MWI) is calculated for each terget entered 

in the MOCOT. If the target has been designated as a mandatory primary 

(through target card input), MWI is set equal to the worth of a zero priority 

target. Otherwise, MWI is optionally set equal to either the inactive target worth (TWI) or the average worth depending on the setting of EGT 938. 

Average worth is calculated from the following equation: 

MWI = TWI(1 - PROBA) TWA*PROBA 

where TWI and TWA are the inactive and active target worths obtained from 

the COTPRIME. PROBA is the probability of activity. This quantity can be 

input as either a target specific parameter on the target card or as a constant used for all targets using EGT922. When the target card probability 

is set to zero, the File 8 probability is utilized. 

3.7.4.4 Flow Charts 

Flow charts of the subfunction TWEEDOFF and its key procedures, ENTMO 

and LUSERCH, are provided in Figure 3-8. 

3.7.5 Restrictions 

The maximum number of targets that can be considered on a single rev 

is 4000. Since 4000 targets are considered to be the limit for a given 

revolution, no special measures have been taken to deal with a larger number. 

-SENETAD 
B NCW(B) = NCW(B) + DELCW 

Construct a weight table for 

all priorities via linear inter- 

' 

polation in the CW table. Used 

in density deletions. 

L L 

B 

NRO APPROVED FOR 

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Page 164 --SEDREUD 

TWEEDOFF TWEEDOFF 

TWEEDOFF 

E

Rewind 

1) COTPRIME ... 

2) INTERMEDIATE 

MOCOT 

3) AND MOCOT 

1 

A 

For A=9, -1, 0 

A DELCW = (CW(A) - CW(A-1))/10 

Calculate the differences in 

weight as a function of priority 

For B=A*10+9, -1, A*10 

Read 

COTPRIME 

tape 

End of file Yes 

mark? 

Determine no. of targets 

in this COTPRIME record 

(NOCTP) 

Figure 3-8. TWEEDOFF Flow Chart 
■■•••■■■ 

Yes 

Yes 

NRO APPROVED FOR 

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Page 165 

TWEEDOFF TWEEDOFF 

Are there less than Yes 

50 COTPRTME entries? 

No 

IF 

((TT1(LAST) - TT1(FIRST))*No. 

of targets LS MODENS 

N 

Construct a priority table, NPRI, 

containing the number of targets in 

each priority level plus the number 

of higher priority to be used in the 

density deletion. 

Locate the level, PRIGD, at which all 

targets of lower priority will be 

deleted on density 

Is density less than 

maximum allowable? 

PRIGD = 1000 

Pass all targets 

thru density filter 

Yes 

For T = 0, 1, NOCTP •

I

__ 

Is this a mandatory primary 

target? 

TMPF 

N 

V 

Is this a visual intelligence 

target? 

TVIF 

No 

V 

V 

Figure 3-8. TWEEDOFF Flow Chart (Continued) 
TWEEDOFF 

TWEEDOFF 

Yes 

Is the inactive worth option to 

be used to determine the worth 

(WPRI) of this target? 

NRO APPROVED FOR 

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BIF-4—B10009-68 

Page 166 --SUREPD 

MOEX 

V 

WPRI = Average weight WPRI = Inactive weight 

) 

Is the weight, WPRI, 

acceptable? 

Yes 

V 

V 

V 

WPRI > MOWGT 

Is the priority level 

acceptable? Yes 

RPRI < PRIGD 

N 

V 

Is deletion print flag 

set? 

DEPRFG 

Yes 

V 

Print target ID and 

deletion comment 

ENTMO 

L 

( 

) 

Generate the MOCOT entry 

for target, T 

Figure 3-8. TWEEDOFF Flow Chart (Continued) 

EXPRI 

Locate the priority level in which 

this target, T, is located. Store 

in RPRI. 
.10•11■ apww011■1■ 

A 

L 

MOCOT(A) = 0 

Set remainder of 

MOCOT buffer to zero 

NRO APPROVED FOR 

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BIF-4-B10009-68 

Page 167 

TWEEDOFF TWEEDOFF 

For A=TJ, 1, MOCOTMX 

(I 

 Write final record 

onto intermediate 

MOCOT tape 

..).--, 

/.. Write end of file 

V 

LUSERCH 

Computer first. MTM. and 

last, MTN, target in partial 

conflict with each target in 

the MOCOT 

( RETURN ) 

Figure 3-8. TWEEDOFF Flow Chart (Continued) 

---Ste-RHAD 

mark and rewind 

MOCOT 
For Z = NN COTPRIME 

••••■•• 

For I =TJ 

MTDUR(I) = 

MOMEGA1(I) 

MOMEGAD(I) 

MMODE(I) = 

MSHAPE(I) 

MSIGMAD(I) 

MCOTENT(I) 

MOCOT 111•••••■■•• 

TT3(Z) - TT1(Z) 

= TOMEGA1(Z) 

= TOMEGA3(Z) - TOMEGA1(Z) 

TMODE(Z) 

= TSHAPE(Z) 

= TSIGMAD(Z) 

= Z+KKNT 

Transfer the following COTPRIME 

parameters into the MOCOT table 

Determine the earliest time, LUTM 

and latest time, LUTN, in which any 

target can be in partial conflict 

with this target. Record LUTM, 

LUTN, MCOTENT and TT1 in the LUJENT 

table for use by procedure LUSERCH. 

NRO APPROVED FOR 

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Page 168 

-11C-RETID 

ENTMO ENTMO 

ENTMO 

Figure 3-8. TWEEDOFF Flow Chart (Continued) 
I I

I I 

I I 

I I 

I 

I 

II 

II 

NRO APPROVED FOR 

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IEGREV D BIF-4-B10009-68 

Page 169 

ENTMO ENTMO 

Is this target a 

mandatory primary? 

TMPF 

NO 

K

Is the worth of this 

target to be its 

average worth ? 

YES 

• 

• 

(

Is MOCOT buffer 

full ? 

NO 

YES 

• 

Write 

intermediate 

MOCOT 

• 

RETURN ) 

I 

I 

II 

I 

1

II 

II 

II 

Yes 

No 

MOEX 

MWI(I) = CWSUBZ 

110' MWI(I) = TWI(Z) 

MWI(I) = TWI(Z) * (1-PROBA) + TWA(Z) * PROBA 

Figure 3-8. TWEEDOFF Flow Chart (Continued) 

IEGRW D 
Is this the latest target 

entry, I, which has no 

conflict with target Z? 

TJENT(I) < TJENT(P) - LUTM(P) 

Yes 

I + 1 is the first 

target in partial 

conflict with target Z 

MTM(Z) = I + 1 

4 

NO 

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Page 170 

'SEOREIL D 

LUSERCH LUSERCH 

LUSERCH 

POINTER = 

Read record 

intermediate 

MOCOT 

For Z=0, 1, MOCOTMX 

[-For P = pointer 

For I = P 

Z I 

P 

I 

I 

I I 

I I 

I 

1 

II 

I I 

Figure 3-8. TWEEDOFF Flow Chart (Continued) 

IBREV D 
= p 

YES 

V 

MTN(Z) = I - 1 

I - 1 is the last target 

in partial conflict with 

target Z. 

( TJENT(I) > TJENT(P) + LUTN(P) 

Is this the earliest target 

entry, I, in total conflict 

with target Z? 

V 

POINTER = POINTER + 1 

NRO APPROVED FOR 

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MIORETID BIF-4-B10009-68 

Page 171 

LUSERCH LUSERCH 

1 I 

, 

I ; 

I I 

I I 

I 

LL 

I 

1 I I 

I 

1 I 

ii i 

11 I 

JJ 

Figure 3-8. TWEEDOFF Flow Chart (Continued) 

(REVERSE OF THIS PAGE LEFT BLANK) 

1-ENEVD 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 BIF-4-B10009-68 D Page 173 

3.8 TWMOSP 

3.8.1 Purpose 

The main optics algorithm TWMOSP selects the best score set of nonconflicting photographic sequences. The effective worth of an individual 

photographic sequence is based on the active target priority, the inactive 

target priority, the probability of activity, the photographic mode, an 

obliquity weighting function, and a stereo weighting function. 

In TWMOSP, the best score set of predecessors is determined for each 

of the targets available in the MOCOT. This information is tabulated in the 

ALMOST table, and the job of reconstructing the optimal path is delegated 

to the successor function TWMOSP2. 

There are three options in TWMOSP: 

a. Interleave Select an optimal sequence of targets regardless 

of whether the same target is selected more than once. 

b. Time Order Select an optimal sequence of targets with the 

constraint that a predecessor for a given target will have 

an earlier initial acquisition time. This eliminates the 

possibility of selecting a target more than once. 

c. Interleave Inhibit Select an optimal sequence of targets 

with the limitation that a target (A) cannot be selected 

more than once if there is only one other target (B) 

between consecutive photographs of A; i.e., the sequence 

ABA is prohibited. 

3.8.2 Input 

The MOCOT table, described in Section 3.7.3, provides the target 

specific information required by TWMOSP. The File 7 and File 8 parameters 

required as input located in Table THINGS are depicted in Table 3-21. The 

File 8 parameters required as input located in Table ALSO are depicted in 

Table 3-22. 

3.8.3 Output 

The output of TWMOSP is contained in the ALMOST table. The content 

of this table is shown in Table 3-23. 

The ALMOST table consists of two files labeled File 1 and File 2. 

File 1 contains data necessary to construct an optimal sequence of targets 

to be photographed which will terminate with any arbitrary target j at 

some finish time a. + T.. Each record consists of a variable number of 

IleRET/ D 

MM. 
Definition 

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Inhibit interleave 

Interleave flag 

0 H 

BIF-4-B10009-68 

Page 174 SECRET/ D 

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Table 3-21. File 7 and File 8 Parameters Used in TWMOSP Located in Table THINGS 

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BIF-4-B10009-68 

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F

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BIF-4—B10009-68 

Page 176 

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SENET7 D BIF-4—B10009-68 

Page 177 

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Page 178 

Definition 

Initial acq

uisition time 

Table 3-23. Format of the ALMOSTTa

ble Entry (Co

ntinued) 

■-1 

O 

Declaration 

COTPRIME entry number of last targ

et in optim

al seq

u

ence 

Time from initial acq

uisition at which optimal score is attained 

Optimal sco

re 

0 cn 

_SE-CitE0 D 
NRO APPROVED FOR 

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ITORETi D 81F-4-B10009-68 

Page 179 

entries, and each entry is variable in length. The first word in each 

record gives the number of 48 bit words in the record. 

The second word of the record is the start of an entry. An entry is 

target specific and will contain information derived from the maximum score 

function or from the alternate maximum score function for an interval of 

time (a, a). The maximum and alternate maximum score functions are constructed piecewise, and the information derived from these functions is put 

into the ALMOST table as the functions are constructed. 

From the above discussion, the tabular listing File 1 in Table 3-23 

cannot be complete, but is intended to show what would be present in one 

entry. The process is repeated for each entry. The maximum number of words 

in a record is 348. 

File 2 consists of one record of four words which specifies the last 

target to be photographed in the optimal sequence, the finish time, the 

optimal score, and the initial acquisition time. 

3.8.4 Method 

There are three different options in the program; the option which 

allows interleaving will be described first since the other two algorithms 

are variations of it. Section 3.8.4.1 describes the basic algorithm. 

This is followed by sections describing the scoring function for an individual target, 4, the conflict parameter, and the method used to 

Qkj 

construct the maximum score function These are the key parameters employed in the determination of the optimal sequence. The time ordered 

algorithm is then discussed in Section 3.8.4.5, and the interleave inhibit 

algorithm is described in Section 3.8.4.6. Section 3.8.4.7 contains a discussion of the TWMOSP flow charts. 

• 

3.8.4.1 The Statement of the Interleave Algorithm 

The algorithm calculates for each target the maximum score obtainable 

by photographing a sequence of non-conflicting targets which terminates at 

that target at a specified finish time. For each target an optimal predecessor is given as a function of finish time. The following notation is 

used for the statement of the algorithm: 

'MS/ D 
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Page 180 'SEGRETID 

(D. (T) = the maximum score obtainable by a sequence of 

J,2, non-conflicting photographs which terminates 

with the photograph of target j in photographic 

mode Q. The finish time of the photographic 

sequence is T measured from the initial acquisition time of target j. 

0. (T) = Max 0. (T) 

J22, J t<T 

1, if 0j,,,(T)> (Dj,z(T) 

Flat(j,2,T) = 

0, if (D. (T) = 0. (T) 

= Optimal predecessor to target j when the mode 

of the photography on j is 2, and the photographic 

finish time is T (measured from initial acquisition 

time of j). 

= a conflict parameter which is used to determine 

whether the target k is a valid predecessor of 

target j. If T. and Tk are the finish times for 

photography on iargets, j and k respectively then 

T. — T

k 

 > Qkj + P. where P. is the time 

— 3,Z 

required to photograph j in mode Z. See Section 

3.8.4.3 for additional information on the conflict 

parameter. 

KyT,Z) = The score for photographing target j in mode i at 

finish time T (measured from initial acquisition 

time of target j). This term is written in this 

way because the shape of the function is basically 

determined by the stereo weighting function (T). 

k

(T) = Max (T) = (I) —(T) 

ksZ 

where 

= 

Mode (k,T) = T 

Pred 

Qkj 
NRO APPROVED FOR 

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Page 181 

--S-EC-RET/ D 

The algorithm for calculating (D (T ,k) and Pred (j,T ,k) is then 

O.(T, = 1(0.(T,,) + Max 0 (T,-Q. .-P. .) 

J J2 J k#j k 3 k3 , 

= K(1).(T,,k) +-QJ J k J KJ J 2 2,) 

where k = Pred 

The selection of the last target in the optimal sequence

t is then done 

as follows: 

Best Score = Max (Max ).(T)) 

j T 

* - 

= 01)7 (T-:) 

3 3 

Then j is the last target to be photographed in the optimal sequence and 

T' = Min T7 

J 

at which 

-(T) = Best Score 

This algorithm allows T. to take on any value over its range, rather 

than having T. chosen from a discrete set of values . The algorithm as 

stated will permit interleaving. The occurance of interleaving can be 

prohibited by the use of an option which employs a modification of the 

above stated algorithm. This is discussed in a later section. 

tThe optimal sequence of targets to be photographed is selected recursively 

in TWMOSP2 by finding an optimal finish time and an optimal predecessor 

for each target in the sequence. 

--MEP D 
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Page 182 SECRET/ D 

3.8.4.2 The Individual Scoring Function For a Given Target 

The value of a specific target is a function of the Basic worth 

calculated in TWEEDOFF and the parameters MMULT and (1)(T). Thus the value 

of a target takes into account such factors as obliquity, activity of the 

target, stereo angle, and priority. In TWMOSP, the value of a specific 

target using a specific kind of photographic sequence (a specific mode) is 

a function only of the finish time t. of the photographic sequence. 

The individual score or weight, W(T), of a given target j with a photographic finish time T is calculated as follows: 

Or 

where 

W(T) = Basic Worth x MMULT x (1)(T) 

W(T) = K x (I)(T) 

K = TWI x MMULT 

MMULT is the photographic mode multiplier which is a function of the 

mode requested and the mode selected. This coefficient is a number between 

zero and one which is input by the File 8 parameters EGT300 through EGT399 

(see Reference 1). 

TWI is the basic worth of a target as computed by the subfunction 

TWEEDOFF and stored in the MOCOT table (see Section 3.7). 

The stereo angle deweighting factor, (1)(T), is determined from the 

File 8 parameters EGT180 to EGT229, which can be used to define up to 10 

stereo weighting functions. The function to be used for a particular target 

is specified as a target card parameter. A description of the function cp(T) 

is provided in Figure 3-9. 
NRO APPROVED FOR 

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Page 183 

114 

Stereo Angle, deg 

Figure 3-9. Stereo Angle Weighting Function 

where 

W is an angle defining the area in which (OW = 1 

(measured in degrees) 

RS1 is the reciprocal slope of this line segment 

(measured in degrees) 

RS2 is the reciprocal slope of this line segment 

(measured in degrees) 

El is the height of this horizontal segment 

(non-dimensional) 

E2 is the height of this horizontal segment 

(non-dimensional) 

c is the desired central stereo angle (this is 

indicated on the target card) 

It should be noted that the input function is provided in terms of 

stereo angle, E, rather than time. The conversion from stereo angle to 

time is performed by the procedure PHIC which is used to determine the 

4(T) function for each target. The stero angle used to define the input 

function is the stereo angle at the midpoint of the photographic sequence. 

SECRET/D 
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Since the algorithm is based on finish times rather than mid sequence 

times, a translation of the function is required. This is also performed 

by the procedure PHIC. 

3.8.4.3 The Conflict Equations and the Determination of Possible 

Predecessor Targets 

The range of possible predecessors is limited by the quantities MTM 

and MTN which are computed in the subfunction TWEEDOFF. That is, the 

MOCOT number k of a possible predecessor to j is such that 

MTM < k < MTN. 

When considering a target k as an immediate predecessor to a target j with 

a photographic finish time T., there are three possibilities. 

a. It is possible to photograph target k for its maximum score 

at some finish time Tk, maneuver from k to j, and settle in 

time to initiate photography of k and finish at time T.. 

b. It is impossible to photograph k for any score and still 

have time to maneuver from k to j, settle, and initiate 

photography on j and finish at time T3. 

c. The time required to slew from target k to target j, settle, 

and initiate photography on j with finish time Tj is such 

that it is not possible to photograph k with a maximum 

score. It is possible, however, to obtain some score from k. 

Consider a method used to distinguish between the three cases. The following definitions are needed in the analysis: 

a. = time when it is first possible to acquire target j 

with main optics 

T. = time interval between first and last possible acquisition 

times of target j with the main optics 

-A = minimum main optics stereo angle (stereo required at 

timea. for acquisition of target j by main optics) j 

B = maximum main optics stereo angle (stereo required at 

time aj + T. for acquisition of target j by main optics) 

b. = main optics obliquity angle required for acquisition of 

target j at time aj 

dbj = change in main optics obliquity angle between times aj 

and aj + Tj 

P. = time required to photograph target j 

T. = time at which the photography of target j is finished 

(measured from a.) 

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Assume that target k is photographed first with finish time Tkand, then, 

target j is photographed with finish time t.. The required obliquity angle 

through which the main optics must move in order to finish photography of 

katTkandbereadYtophotograPhjattimeT.-P.is AR

req 

where 

db. (Sb k 

= (b. + 

4 

AR

req J T. JJ 

(T. - P.) - (bk Tk T1) 

Similarly, the required stereo angle change APreq 

is 

AP

req 

(...A B+A (T. p.)_ (_AT(To) 

T. J J 

Let 

Ab = b. - b j k 

AT = T. - T j k 

a = T. - Tk 

Aa = a. - a j k 

and 

= (a. + T. - P.) - (ak+ Tk) 

J J J 

Aa + AT - P. 

Moreover, let 

(

db. dbk) 

T. 

3 Tk

2 

and assume that 

db. 

J2. a 2. 

61)

k TJ T k 

At 

a

kj 

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SEGRE17 D 

This latter assumption will introduce some error in ARreq, 

 but this error 

is small (see Reference 2 pp.96-97). Thus, the equations for ARreq and 

AP

req 

can be rewritten as 

AR

req 

= Ab + akiAt - akiAa 

B+A (

AP At - Aa 

req T

k 

a (T 

.-P. 

T. 

J 

IfthefinishtimeT.of photography of target j is fixed, then AP

req 

and ARreq 

are linear functions of At. The time required to perform various 

stereo and obliquity maneuvers is assumed to be a piecewise linear function 

of time as shown in Figure 3-10. 

(T4, AS4) 

AS3) 

, As ) 

AS1

) 

Maneuver Angle, AS (degrees) 

Figure 3-10. Maneuver Time Required vs Maneuver Magnitude 

-SEGRER D 

Time, T (Seco

nds) 
AR(At) 

AR

req 

At,sec 

At=Aa-.4.11 

clkj 

Obliquity Maneuver Time 

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These functions are determined by the points (ti, AS.) (i = 1,2,3,4) which 

are defined by the File 8 input parameters EGT950 through EGT 965. The 

quantity AS in the previous figure represents both obliquity (AR) and 

stereo (AP) maneuvers. Denote the obliquity angle achievable in a time 

interval At by AR(At). Then, in order for a Tk to be feasible, the relation 

AR

req 

<. AR(At) must hold. Figure 3-11 below shows AR

req 

and AR(At) plotted 

as a function of At. At the point G, AR

req 

= AR(At), and for At < AtG the 

required obliquity maneuver cannot be performed in the time available. 

AR, degrees 

Figure 3-11. ARreq and AR(At) vs At. 

-SECRET/0 
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Similarly, denoting the stereo angle change achievable in time At by AP(At), 

the relation 

AP

req 

<. AP(At) 

must be satisfied in order for a time T

k 

to be feasible. A plot similar 

to that shown in Figure 3-11 can then be drawn for stereo versus At. This 

yields a AtHsuch that for At < AtH, the required stereo maneuver cannot 

be achieved in the time available. 

The piecewise linear functions which yield AP(At) and AR(At) are 

specified as: 

AP = + M

P

(m) (At - S (m)) 

At (m-1) < At < At (m) 

p — P 

m = 1, 

AR = + MR(n) (At - SR(n)) 

AtR

(n-1) < At < AtR (n) — — 

n = 1, • N 

for 

and 

for 

where 

A+B < M (1) < M (2) < • ' • < M (m) 

T

k 

clkj < MR(1) <MR(2) < • 

The M's are the slopes of the lines, the S's are the intercepts of the lines, 

and the At's are the limits of the domains of definition for each line 

segment. The parameters QkjRand Qkjpare then defined by the equations 

given below. These parameters then define Qkj which satisfies the relation 

AT > Q . + P. kj j 

-SHIM D 
+P. = min kjR j + P. - Aa 

(Ab-akiAa-MR(n)SR(n) 

-MR

(n) - akj ) 

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The following equations are used by the procedure CONFLICT to determine the 

parameter Oki. 

(Ab-akiAa+MR(n)SR(n)) + P. - Aa 

j +P = min kjR MR(n) akj 

n=1, ,N 

for 

Aa - Ab < SR(1) 

kj 

or 

n=1,...,N 

for 

b Aa - A > S (1) 

akj R 

for the obliquity. Similarly, for the stereo 

Q . +P. = min kjP 

Aa ( a“m)(T.-P.) S (m) P 

J J 

B00-1 T. (f3(m)-l) 13(m)-1) Pj 

m=1, ,M 

o(T.-P.) 

J 

T. < S (1) 

for 

Aa + 
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or 

( as(m) (T.-P.) Aa 

S (m) 

Q, .

Kir

,,+P.3 = min (3 1+(3 (m) + P

T.(1+(m)) 1+(m) j ' 

3- 

for 

cr(T.-P.) 

Aa + T. 

> SP

(1) 

So, it is necessary that 

AT > Qkjp, 

AT > QkjR, 

and 

T, - T = AT k > Qkin 

where 

= max (Qk3 .

P Q . ) Qkj 

SinceO<T.

3 

 < T. and 0 < Tk< Tk' 3 

the limits of AT = T. - Tk are 

— 3 — — 

T. > AT > - Tk

. At the beginning of this section, three possible cases 

3 — _ 

for k being a predecessor of j were discussed. These are related to Qkj 

as follows: 

1) Qkj + Pj < -Tk; k is a predecessor of j for the entire range 

2)1Qkj +P.>T.;Ic is not a feasible predecessor of k 

3) Tjkj + P > -T • k is a predecessor of j for some of 

— 

. — k' the range of values of AT 

The calculation ofQkj is discussed in more detail in Reference 2 on 

pp. 91-124. 

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SO 

3.8.4.4 The Construction of 0.t 

J 

The computation (T.) requires(r,) for each mode k (1 < k < L.). 

J 19J 2, 

_ j 

In computing the function 0 (T.)' for each of the modes k(l< < L.), the 

, 19)2 J J 

computation must, in general, be done over only part of the range 0 < T < T. 

J J 

of that target. The interval over which computation may be carried out is 

a. < T. < a.. Furthermore, the construction of 4) 

j

(1 ) is dependent upon 

9 9, 

the existence of k

(T

k

) for each predecessor k of j. There are two important decisions to be made in computingO.); the choice of the proper 

)j2 2,J 

j and the determination of the largest possible range a. < T < a. over which 

calculations can be carried out. 

The parameters a defines the extent to which the function4) has been 

J

, 

completed. Sincea, is reverenced to initial acquisition time, this corres- j 

ponds to a time a. + a.. The target that has the lowest numerical value of 

a. -Faisthentheearliestuncompletedtarget(providedthatu since 

aj = T. implies that the function for this target has been completed). The 

process of finding the proper target to analyze is performed by simply findingthetargetthathastheminimmvalueofa.+a subject to the constraint 

that only targets that have not already been completely defined are considered. 

Initially, a. is set equal to zero for all targets. The first target to be 

considered is then the target that has the earliest first acquisition time, 

a. 

The extent to which the function 1. can be developed is limited by 

the state of completion of the candidate predecessors with respect to target 

j. If all predecessor functions k (T

k

) have been completed over the 

allowable range OfTkfTk' then the target j can be completed (i.e., a =T.). 

If the predecessor functions have not been completed, the target j can be 

developed up to the time a where 

a. = Min (Q + P. + ak) 

3kfj kj J 

Beyond this time, the predecessors to target j are not properly defined. 

The computations then proceeds by deve, ping segments of individual targets 

until all targets have been completed. 

t

Symbols used are defined in Sections 3.8,.4.1 and 3.8.4.2. 

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After the target j has been chosen and the parameters a has been 

determined, the function (T.) is determined for each photographic 

j,k J 

mode 9.. 

Thus, 

0. (T.) = Max *(T. - Q . - P.) + KcID (T.,9,) 

J,k J k kJ 

k#j 

where MTM < k < MTN and a. < T. - Q - P. < a . 

— kj — k 

Therefore, 

* 

(T.) = CD- (T - Q . - P ) + (T j ,9) j j ' 

for some k. The optimal predecessor is then k 

TheuseofT.--Ptranslates the time axes of each feasible pred- J Qkj . 

ecessor k by the photography time P. plus the minimum time required to 

maneuver from k to j and settle. 

The function 0. (T.) is then flattened, that is, the function 

J 

0. (T.) is calculated for the mode Z. This calculation is 

J 

* 

0. (T) = Max 0. (T) 

J j 339, 

T < T. 

A flattening table Flat (j,9.0.) is also constructed defining, the 

regions where 0* is greater than . This table contains the T values at 

the beginning and end of each flattened region and a bit (ff) that identifies where flattening has occurred. A setting of ff=1 identifies the beginning of a flattened region and ff=0 indicates the beginning of an unflattened region. 

NOTE: The parameters MTM and MTN are MOCOT table entries. For their 

description, see Section 3.7.3. 

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An example of a flattening is shown in Figure 3-12. The dotted lines show 

where 0* (T)> 0. (T) 

i•SZ, JsQ 

(T,ff) 

Figure 3-12. Example of flattened Function 

The entire process is repeated for each possible photographic mode 

of target j to yield a maximum score function 0. (T) for each mode 

J,k 

= 1, 2, L. Then, 

0*(T.) = Max 01! (T.) = 4,* (1.) 

k=1,...,L. J'k j92 3 

where It = the optimal mode for the jth target and photographic finish T. 

time T,. 

TheoPtimalPreclecessoratT.isPred0,Tiformodekeri. 

The construction of 0.(T.) is continued until all of the targets 

J J 

in the MOCOT have been completed. Then the target with the largest maximum 

score is found, and this information is entered in the second file of the 

ALMOST Table. 

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--SEC-RET1 D 

3.8.4.5Constructicncfq).(T) for the Time Ordered Algorithm 

When EGT941 is set equal to 1, the following modifications are made 

in the construction of 4).(j). 

a. The value of MTN for each target is set equal to the MOCOT 

number of the target. 

b. For a given target j, only those predecessors k are considered whose initial acquisition time akis less than or equal 

to a., the initial acquisition time of the target j. In the 

caseJ of ak = a., the target k is considered as predecessor 

of j only if is maximum score functioncl ) (T) has already 

been computed. 

c. The entire range of values of (DAT) is computed at one time. 

That is, a. = T. which is the maximum of T for target j. 

The principle effect of the above modifications is to shorten running 

time considerably. The reasons for this are fairly obvious. The number 

of possible predecessors for a given target is often reduced, and the 

(1).(T) for each target is computed for the entire range 0 < T < T. at one 

J 

time. The reduction in running time is, of course, dependent on the particular selection of targets passed to TWMOSP in the MOCOT. Since the time 

ordered algorithm limits the number of possible predecessors to a given 

target, the resultant selection may be suboptimal. However, the conditions 

under which this represents a significant decrease from the optimum are 

not known and this option will require further study. 

3.8.4.6Constructionof'D.(T) and (DjA(T) for the Inhibit Interleave Algorithm 

The output of TWMOSP may result in a selection of targets for the 

main optics which contains the same target more than once. If targets 

are denoted by A, B, and C, then the inhibit interleaving option (EGT042=1) 

is designed to prohibit a selection of targets for the main optics where 

A is photographed then B, and then A again (ABA). The algorithm will not 

specifically prohibit other types of interleaving such as ABCA. This option 

computes a maximum score function (I) *(T) and an alternate maximum score 

function (1)Aj *(T) for each target j. The algorithm for computing these 

functions is very similar to that used in 3.8.4.1 for computing *(T). 

The notation used for the statement of the algorithm is as follows: 
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CD. (T.) 

J 

= Maximum score obtained by photographing a sequence 

of targets ending with target j and finishing the 

photography of j at time Tj. The mode of photography of j.at time Tj. The mode of photography on 

j is Q. The sequence will not contain ABA interleaving. 

= Max 0. (T) j,k 

T < T. 

J 

Pred(j,2„1- .)= Optimal predecessor of j when the photographic mode 

of j is k and the finish time of the photography is 

1, if 0. (T.) > (1).

J2, ,

(T.) 

J92,J J 

Flat (j,k,T.) 

0, otherwise 

* * * 

4).

.7

(T.) = Max 0.

J'i 

 (T.) = 0. (T.) 

J J J,Z J T. 

k=1,...,L. 

Mode (j,T.) = R. in the above definition 

3 T. 

A,j,k(T.) = Alternate maximum score obtained by photographing 

a sequence of targets such that: 

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1-EiREUD 

a) the sequence terminates with target j 

b) the mode of photography on j is 2, 

c) the finish time of the photography on j is Tj 

d) the predecessor of j in the "alternate optimal 

sequence" is not pred ,T.) T. 3 

e) the sequence will not interleave. 

PredA(j,t,Tj

) = The alternate optimal predecessor to j. That is, 

the predecessor used to compute (I) (T.). By A,j,k 

its definition, FredA

(j,R,Tj

) Pred ) 

The terms Pred

'

k

'

T

j

), FlatA (j,k,T.), (I)A3 .(T.), and ModeA (j,T.) are de-• 

finedanalogouslytothetermsPred(j,k,T.), Flat (j,i,T.), (1).(T.), and 

J J J 

Mode (j,T.). The statement of the algorithm is: 

(J (T.) = t) 

IR J J, 

+ Max/6 k

(Tj-Qkj -Pj

) + (1-6) Ak (Tj -Q . k3 

MTM < k < MTN 

1 if Pred (k,tt, Tj - Qki - pj) # j, 

.1 

where 6 = 

0 otherwise 

and 0 < T. - - < a.. 

— kJ 3 
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Then 

(I). 

lk

(T.) = K4.(T.) 

i J J 

{ 

(1)-

k

(T.-Q- -P.), if 6=1 

(D A -(T.-Q-. -P.), if 6=0 

J kJ 

and 

Pred-(jlk,T.) = 1( 

The computation of(T.) is the same as (1). n(T.) except that the preAj,Z j J 

decessor k cannot equal Pred (j,R,Ti). The computation of Flat (j,k,ri), 

Mode (A,T- .), and ModeA 

(j'

T

j

) is done the same as in Section 3.8.4.3. 
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'ITORETZD 

3.8.4.7 Flow Charts 

A few remarks concerning the flow charts shown in Figure 13 are in 

order. The parameters f and g are used in the inhibit interleaving option 

to identify maximum score functions and alternate maximum score functions. 

The parameter f refers to the target whose score function is being computed. 

The parameter g refers to the target which is being considered as a predecessor. A setting of 0 indicates that the function is the maximum score 

function and 1 identifies the alternate maximum score function. 

The flow of computations is roughly as follows. 

a. Read in data from MOCOT as memroy space is available. 

b. Select target, j, whose maximum score function is to 

be computed. 

c. The score function is computed piecewise, and the time 

interval a. < T. < a.3 over which compution is done is 

computed. If the time ordered solution is being computed, then the entire range of values for the score 

function is computed at once. 

d. For each feasible predecessor k of j, the following 

is done: 

1. If the predecessor k is not 

flict then translated0

k 

is 

Q . + P.. kJ 3 

2. If interleaving is to be inhibited then 

the scoring function of k is set equal to 

zero where the predecessor of k is j. 

This will inhibit a selection of j k j. 

3. When the alternate maximum score function 

(f = 1) is being constructed, the predecessors of the maximum score function 

(f = 0) are disallowed. This is accomplished by setting the worth of a predecessor to zero in regions where this predecessor is included in the maximum score 

function. 

4. The resultant predecessor score functions 

are used to find a maximum score function 

of j. 

in total contranslated by 
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5. The process is repeated for all feasible 

predecessors. A table of optimal predecessors is computed. 

e. The resultant maximum score function is added to the 

basic scoring function of j. 

f. The resultant sum is flattened by the formula 

_ * 

AL. (T.) = Max T.(T). 

J J 

T < Ti 

The flattening table is also computed at this time. 

g. The foregoing calculations are repeated for 

each mode and the resultant family of maximum score 

functions for j (one for each mode) is then maximized 

to form a maximum score function for j. An optimal 

mode table is also computed. 

h. The resultant target information to be used in 

TWMOSP2 is stored in the MOST table and read into 

tape as necessary. 

i. The process is repeated for (f = 1) if the inhibit 

interleaving option is to be used. 

j. When all of the functions have been computed for 

each target, the last target to be photographed in 

the optimal sequence along with its finish time, 

initial acquisition time and the maximum score 

attained are stored in the ALMOST table and read 

onto tape. 

k. The program exits from the subfunction. 

3.8.5 Restrictions 

The maximum number of targets that can be contained in core is 220. 

This becomes a problem only if the target density is such that the number 

of acquired targets exceeds 220 within approximately 50-60 seconds. If 

this happens, the program will produce an optimal target selection until 

the density gets too high and then print an error message. The selection 

achieved to that point can be obtained by continuing the run or the run 

can be restarted using a tighter setting of the TWOPS density filter 

(EGT936 and EGT937). 

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'SMEUD 

To inhibit A-B-A type interleaving, a maximum of 20 targets can be 

stored as valid predecessor of a given target. This limit is liberal for 

realistic maneuver and settle times for the vehicle and realistic photography sequence times. A-B-A interleaving can occasionally be forced to 

occur in high target density areas with infinite maneuver rates and short 

photographic sequences. 

A set of 20 discrete points is available to describe the function 

representing the sum of the basic scoring function of the target and the 

resultant maximum function of all possible predecessors. This limit may 

occasionally be exceeded in regions of dense target distribution. If so, 

an error analysis is performed to determine which points can be removed 

producing the minimum amount of error in the function. No discernable 

errors in the optimal selection have even been detected, due to the 

limitation. 

•.) 
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TWMOSP TWMOSP 

ri 

TWMOSP 

(ewind 

MOCOT and 

N .ALMOST 

11r 

Initialize 

tables 

For I=0, 1, 21 

IF 

Read MOCOT 

tape 22 

records 

• 

Select target whose 

scoring function is 

to be computed 

j=MIN(a.3.+a.) 

for K<i < 

and ai < MT1 

• 

Determine time interval over 

which function will be computed 

a=MIN(Q + P kj ) 

Lj 

for MTM < K < MTN and 

0 < L < no. of modes of j 

Figure 3-13. TWMOSP Flow Chart 

-SEGRETID 

11111.111=1• 
a = MTDUR, 

where MTDUR, is 

the total time on 

target j 

V 

L = 0 

V 

V 

Initialize: 

f = 0 

LL = No. of modes - 

CONFLICT 

Calculate the time for 

the main optics to maneuver 

from target k to target j 

and settle (Qkj). 

SHIFT 

Translate predecessor scoring 

function by Qkj for either best 

(g=0) or 2nd best (g=1) version 

onto time axis of target j and 

store result in 1' 

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TWMOSP 

TWMOSP 

MOFLG = 1 

 Yes 

Time-order 

solution? 

No 

Figure 3-13. TWMOSP Flow Chart (Continued) 

-SERER D 
DEPRESS 

Set the scoring function of k 

to zero where the best version 

of target j has target k as a 

predecessor 

Allow interleaving. 

N 

V 

PREDSHIF 

Shift the predecessor table 

of target k onto time axis of 

tarjet j, via Qkj 

DEPRESS 

Set the scoring function, T, of 

target k to zero where the predecessor 

of k is j to inhibit interleaving 

NiYes 

f = 0? 

MAXIM 

Calculate a new r by maximizing 

the old I' and T for target k, and 

construct the predecessor table 

which reflects this maximum 

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TWMOSP TWMOSP 

INLEVE = 1 Yes 

V 

Figure 3-13. TWMOSP Flow Chart (Continued) 

-SfERHfD 
PHIC 

Construct basic scoring function, 

4)., for the target between time 

limits a and a 

• 

Add maximum, r, and basic scoring 

function, 4)j, store in 8 

= r + . 

4'3 

• 

Wherever 8 decreases in worth, 

artifically flatten 6 and generate 

table FLATFUN to indicate regions 

of artificial flattening 

L= 0? 

No 

) Yes 

MAXIM 

Maximize the scoring function for 

the modes of photography and 

construct the resultant mode table 

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SLEORET-1-1) 

TWMOSP TWMOSP 

Figure 3-13. TWMOSP Flow Chart (Continued) 

---SECTRETID 
L + 1 i L 

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TWMOSP TWMOSP 

Merge the target information 

j, a„ a„ MT1, PEED table 

FLATFUN table, MODE table, 

into an entry in ALMOST buffer 

7 

( Is ALMOST buffer full? 

Yes 

Write 

ALMOST 

on tape 

• 

( f = 0? 

No 

Q) ,

)Yes 

Figure 3-13. TWMOSP Flow Chart (Continued) 

-1-EtREVD 
Yes 

Determine starting point for 

reconstruction of optimal 

sequence (j, 

Ti9 MT1., SCORE) 

3 -> ALMOST 

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-MEV D 

TWMOSP TWMOSP 

(

Is there any 

MOCOT (target) 

data not yet in 

core? 

Yes 

Is there any target 

specific data in core 

than can be released? 

N 

IlrYes 

Read new MOCOT 

(:(I 

data over old 

unneeded data L1 

Has all data been 

processed? 

T 

Write T4 

ALMOST 

RETURN ) 

Figure 3-13. TWMOSP Flow Chart (Continued) 
From the predecessor table, 

extract the time span, 

t. I+1 P I.and tP over which ' te Ith predecessor is 

the best 

Yes 

Have all 

predecessors 

been examined? 

Yes 

RETURN 

DEPRESS 

I = 0 

N 

(

Is predecessor target, 

No I, one which would 

allow A-B-A interleaving? 

= I + 1 

Set the function, Y, to 

zero between ti and tP I+1 

-SECRET!D NRO APPROVED FOR 

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BIF-4-B10009-68 

Page 207 

DEPRESS DEPRESS 

Figure 3-13. TWMOSP Flow Chart (Continued) 

ID 
V 

Determine which function r 

or T has the greater worth at 

the beginning of the a - a 

region and record point in 

B function 

NRO APPROVED FOR 

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BIF-4-B10009-68 

Page 208 

-SEG-REVD 

MAXIM MAXIM 

( MAXIM 

No Is the maximization for Yes 

predecessor targets? 

Record the resultant best 

mode of photography in the 

mode table 

V 

Record the winning 

predecessor target in 

the PRED table 

• 

Examine each discrete breakpoint of r and T 

( Is the winning function, Yes 

the same as the previous 

winner? 

V 

TINSECT 

Compute the intersection 

of r and T and store in 

8 

Figure 3-13. TWMOSP Flow Chart (Continued) 

-SEC-REVD 
• 

Record the r or T 

breakpoint in B if it 

belongs to the resultant 

best function 

) 

( Have all breakpoints of 

r and 'P been examined? 

• 

-SEMI D NRO APPROVED FOR 

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Page 209 

MAXIM MAXIM 

(

No Is the maximization for Yes 

predecessor targets? 

• 

Record the resultant best 

mode of photography in 

the mode table 

Record the winning predecessor target in the 

PRED table 

Yes 

• 

Copy the resultant 

maximum function 8 

into r 

( RETURN 

Figure 3-13. TWMOSP Flow Chart (Continued) 

-SECRETID 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 210 

-S-EC-REM 

CONFLICT CONFLICT 

( CONFLICT ) 

• Compute required stereo 

tracking rate for target k 

• Compute approximate obliquity 

tracking rate for target k 

• Compute differences in initial 

targets obliquities, total 

acquisition times, and initial 

acquisition times for targets 

j and k 

EGT063:Maximum forward stereo 

angle for main optics 

EGT065:Maximum aft stereo angle 

for main optics 

• Determine intersection of stereo 

maneuver required line with 

specified stereo maneuver capability curve 

EGT950-953: Slewing times for main 

optics stereo angle 

slewing table 

EGT954-957: Delta stereo angles for 

main optics stereo angle 

slewing table 

Determine Qkj for stereo maneuver 

Figure 3-13. TWMOSP Flow Chart (Continued) 

SECRET/ D 
Oe 

NRO APPROVED FOR 

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Page 211 

CONFLICT CONFLICT 

o Determine intersection of 

obliquity maneuver required 

line with specified obliquity 

maneuver capability curve 

EGT958-961: Slewing times for main 

optics obliquity slewing 

table 

EGT962-965: Delta obliquities for 

main optics obliquity 

slewing table 

o DetermineQkj for obliquity maneuver 

Set Qkj equal to the maximum 

of Q for the stereo Maneuver and 

Oki igr the obliquity maneuver 

• 

RETURN 

Figure 3-13. TWMOSP Flow Chart (Continued) 

---SH-RET/ D (REVERSE OF THIS PAGE LEFT BLANK) 
NRO APPROVED FOR 

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Page 213 

3.9 TWMOSP2 

3.9.1 Purpose 

The subfunction TWMOSP2 abstracts the optimal main optics photographic 

sequence from the ALMOST table and outputs that sequence in the Main Optics 

Strategy Table (MOST). The ALMOST table contains the set of optimal sequences 

down to and including every target under consideration. The sequence that 

attains the maximum score is then the overall optimum. TWMOSP2 scans the 

ALMOST table to find the target that completes the la 

The predecessor information is 

and to determine which targets 

and photographic mode are also 

target identifier, acquisition 

lated in the MOST. 

then utilized to trace 

are contained therein. 

determined for each of 

time, and photographic 

rgest score sequence. 

this optimum sequence 

The acquisition time 

these targets. The 

mode are then tabu3.9.2 Input 

The input to TWMOSP2 is the ALMOST table described in Section 3.8.3 

3.9.3 Output 

The output of TWMOSP2 is the MOST table. The contents of the MOST 

are shown in Table 3-24. The MOST table contains the sequence of targets 

that yields an optimal score. For each target in the optimal sequence, 

there are two words in the MOST table. They contain the finish time, the 

optimal photographic mode, and the COTPRIME entry number of the target. 

Table 3-24. MOST Table 

Units 

sec 

Definition 

The time that photography will 

be complete on this target 

(i.e., finish time) 

n.d. Mode in which photograph is to 

be taken 

n.d. COTPRIME entry number of 

target 

Symbol JOVIAL Declaration 

PPFIN F 0 0 

PMODE 14 U 10 

PCOTENT I 2 U 14 

Repeated for each target in the main optics selection. 

3EEREiYD 
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BIF-4-B10009-68 

Page 214 

-S-EC-REIT D 

3.9.4 Method 

File 2 of the ALMOST yields the last target j, to be photographed 

along with its finish time, T . File 1 is then searched until the data 

on this last target, j, is found which covers the finish time T,. The 

optimal mode 9Ti selected from the mode table, and the predecessor 

and flattening tables corresponding to this mode are then selected. 

The finish time will fall between two consecutive entries in the 

flattening table, e.g., T ys T p+1. If the flattening bit ff(t ) is 

equaltozero,thenthefinishtimeiskeptatthevalueT,If, however, 

ff(T ) is equal to one, then the finish time is set equal to T since a 

larger total score can be obtained by completing photography at this 

earlier time. In either case, this finish time is used to select an 

oPtimalPredecessor,1"ThefirlishtimeistranslatedbY 1)to yield 

Q kj -1- P. 

a finish time T

k 

for the predecessor k. The finish time for target k is 

determinedfromtherelationTiki - P. where Oki is the conflict 

parameter described in Section 3.8 and P. is the time required to photograph 

target j. The process is repeated until a special kind of predecessor 

called the pseudo target is encountered. The pseudo target simply designates 

that a target has no predecessor. Therefore, the target in the optimal 

sequence which has the pseudo target as its predecessor is the first target 

in the optimal sequence. The MOST table is then written on tape and the 

program exits from TWMOSP2. Figure 3-14 presents the TWMOSP2 flow chart. 

3.9.5 Restrictions 

The subfunction TWMOSP2 can produce a Main Optics Strategy Table 

(MOST) consisting of up to 150 targets. If there are any more than 150 

targets belonging to the optimal sequence set, they would be lost from 

the sequence. Since 150 targets is considered to be the limit for a single 

rev, no provision was made to produce a larger set. 
Yes (

Does entry (I) of 

ALMOST contain proper 

COTPRIME entry no.? 

EXTRACT: 

1) COTPRIME entry no. 

2) Time from initial 

acquisition at which 

optimal score attained (T) 

3) Optimal score 

4) Acquisition time (MT1) 

Read ALMOST 

double buffer 

opera 

• 

No 

(

Yes Is this the last entry 

in record? 

I = 0 

irmitrio NRO APPROVED FOR 

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Page 215 

TWMOSP2 TWMOSP2 

TWMOSP2 

Position ALMOST 

to 2nd file and 

read record 

Figure 3-14. TWMOSP2 Flow Chart 

,SECRW D 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 216 

TWMOSP2 TWMOSP2 

(

Does the time (T) fall 

within the time limits 

(a, a) of this entry? 

Yes 

• 

Transfer the ALMOST 

entry into the working 

buffer (DATIN) 

Unpack DATAIN: 

Mode data --> MSMODE table 

Predecessor -> PRED table 

Flattening data --> FLATFUN table 

., 

Get proper updated time 

(T) from FLATFUN table 

V 

COPY: COTPRIME entry no., 

mode and finish time (MT1 + T) 

into MOST table 

V 

(

Is the predecessor target 

of this COTPRIME no. the 

psuedo target? 

Yes 

......1 

Write the 

MOST tape 

Ilr No 

Calculate time of predecessor 

attachment (T) RETURN 

STORE: COTPRIME entry no. 

and time (T) for optimal 

predecessor 

CA) 

Figure 3-14. TWMOSP2 Flow Chart (Continued) 

--SECREY D 

a < T < a 
NRO APPROVED FOR 

RELEASE 1 JULY 2015 --SECIEND BIF-4-B10009-68 

Page 217 

3.10 TWASCON 

3.10.1 Purpose 

The Acquisition Telescope (ATS) portion of the TWONDER program 

simulates the area of the mission in which the human factor plays an important role. By means of tracking telescopes, the crew views an optimally 

selected number of targets. These targets are of three types: targets 

selected by the main optics algorithm for photography; targets that can be 

substituted for a main optics target because some important variable used 

in the main optics selection is changed; or visual intelligence targets 

(VITs) for which main optics photography is not required. If, for instance, 

heavy cloud cover obscures the primary target, it might be possible to 

photograph a nearby target without interrupting the remainder of the main 

optics sequence. Another possibility is the crew detecting something about 

a target not previously known that would make photography of this target 

quite valuable. In both of these instances, the crew must make a decision 

or help an on-board computer make a decision whether to photograph a target 

other than the previously determined primary. 

Targets that might be substituted for a primary target or for which 

there is no photographic requirement are referred to as alternate targets. 

It is the purpose of the ATS to view all primary targets as selected by the 

main optics algorithm and all alternate targets as selected by the ATS 

algorithm. 

The subfunction TWASCON provides a list of potential alternate targets that will be considered in the ATS algorithm employed in the subfunction TWASSP2. This list of alternates is determined by investigating all 

available targets and deleting certain ones because of physical constraints, 

conflicts, or other pertinent reasons. 

3.10.2 Input 

The primary inputs to TWASCON are the THINGS table, the COTPRIME. 

information generated by TWOPS, the MOST data generated by the main optics 

selection algorithm, the PCURVE and RCURVE table generated in TWOPIN, and the 

DELTAT1, DELTAT2, and DELTAS arrays obtained from ALSO table. The File 

8 parameters required as input are depicted in Tables 3-25 and 3-26. 

-SEGREVD 
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BIF-4-810009-68 

Page 218 

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,SEC-RETIO BIF-4-B10009-68 

Page 219 

Table 3-25. 

File 8 Parameters Used byTWASCON Located in Table THINGS (Co

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BIF-4-B10009-68 

Page 220 

5EGREV D 

Table 3-25. File 8 Parameters Used by TWASCON Located in Table THINGS (Continu

ed) 

Inte

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iEntl7D BIF-4—B10009-68 

Page 221 

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BIF-4—B10009-68 

Page 222 

Table 3-26. F

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SECRET/0 NRO APPROVED FOR 

RELEASE 1 JULY 2015 BIF-4-B10009-68 

Page 223 

The following THINGS table items are referenced by TWASCON and are not 

File 8 parameters, but values calculated or set by certain routines to be 

used by later routines. 

ASIG = Maximum forward stereo angle for main optics 

BSIG = Maximum aft stereo angle for main optics 

NASCOTE = Number of ASCOT entries 

NMOSTE = Number of MOST entries 

Tl 

T2 

T4 

T5 

Logical tape unit assignments 

The pitch and roll rates and settle times for the main optics are 

acquired from the tables PCURVE and RCURVE where 

PCURVE = table calculated by TWOPIN using the input arrays DELTP 

and DELP 

RCURVE = table calculated by TWOPIN using the input arrays DELTR 

and DELR 

The forward and aft photography times are obtained from the DELTAT1 and 

DELTAT2 arrays as a function of mode and the stereo angle is obtained from 

the array DELTAS as a function of mode. 

3.10.3 Output 

The primary output of the subfunction TWASCON is the ASCOT table. 

This is a serial table of 200 entries per record and 7 words per entry. 

The items that make up the ASCOT are as follows: 

RCOTENT = OOTPRIME entry number 

ROMEGA = mean obliquity 

RTDWELL = dwell time 

RTFIRST = earliest ATS viewing start time 

RTLAST = latest ATS viewing start time 

RWGTHI = high order weight 
NRO APPROVED FOR 

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BIF-4-B10009-68 -SE-RETID 

low order weight 

group number 

total time target is visible through main optics 

earliest time target is visible through main optics 

last decision time 

The number of ASCOT entries, NASCOTE, is set in the THINGS table. 

The COTPRIME table is added to by TWASCON and the extended table is 

written. The new items are: 

TSCOPON1 = earliest ATS on time 

TSCOPON2 = latest ATS on time 

reason target was deleted from ASCOT 

NOT OK or delete flag 

weather alternate flag 

activity alternate flag 

primary or MO flag 

high order weight 

low order weight 

TMOSTENT = MOST entry number 

TMOSTGP = MOST group number 

TLASTDT = last decision time 

The capability of writing the ASCOT table provides additional output. 

This can be either on-line, off-line, or both, and is a function of an input 

option. 

The following comments are output from TWASCON: 

NUMBER OF ITEMS ACQUIRED BY ASCON = XXXX, and is simply a statement 

of the number of items in the ASCOT table. 

Page 224 

RWGTLO = 

RGROUP = 

RT3T1 = 

RT1 = 

RLASTDT = 

TREASON = 

TNOTOKF = 

TWXAF = 

TAAF = 

TPRIF = 

TWGTHI = 

TWGTLO = 
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NUMBER OF TWASCON DELETIONS DUE TO GROUP SIZE = XXXX, which tells 

4 the total number of deletions from the ASCOT because the individual group 

sizes exceeded the maximum acceptable. 

When deletion print is requested, all COTPRIME items that have their 

delete flag set are listed along with the reason they were deleted. 

3.10.4 Method 

By using various filters, the number and type of targets that are 

passed on to the algorithm can be closely controlled. The density control 

is especially necessary to the proper functioning of TWASSP2. The number 

of targets in an ATS group, which consists of all the targets that could 

possibly be viewed as an alternate to a main optics selected target, must 

be kept under a certain maximum. An unlimited number of candidate alternates leads to an inefficient and time consuming solution. Filtering as to 

particular types gives the program greater flexibility and contributes to 

program efficiency and faster computation times. 

In addition to filtering, targets are not considered as potential 

alternates if there is any physical conflict, either of a hardware nature or 

an imposed software condition. By definition, a target is an acceptable 

alternate if it is possible for the main optics to change its predetermined 

path, move to the alternate instead of the primary, complete requested 

photography, and return to the next primary in the main optics sequence. If 

any of these conditions cannot be met, the target cannot be an alternate 

and, consequently, is not inserted in the list of potential alternates. 

••■ 

When all the potential alternates input to TWASCON have been checked 

for acceptability, the completed list of alternates, called the ASCOT table, 

is passed on to the subfunction TWASSP2. Here the optimization algorithm 

selects for viewing those targets that produce the best score. Every target in the ASCOT table meets all the conditions of an alternate, and the 

only reason a target would not be viewed is if it is not found to fit into 

one of the optimum (score maximizing) paths. 

In addition to the main program, the subfunction TWASCON is composed 

of three main procedures. The procedures are TYPEFILT, GEOMFILT, and GENASCOT 

and are included in the TWASCON flow chart, Figure 3-15. 
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-SWIM D 

TYPEFILT performs the filtering of particular types, GEOMFILT makes the 

calculations necessary for the geometric compatibility checks, and GENASCOT 

constructs the ASCOT table. There are also several smaller routines whose 

functions will be discussed as they are referred to. 

The main program performs most of the table and item definition and 

initialization functions in TWASCON. The primary tables used are the MOST 

table, the COTPRIME and COTPRIMEX tables, the ASCOT and ASCOTX tables, and 

the THINGS table. The MOST table contains the data read from the MOST tape 

generated by the main optics selection algorithm. The COTPRIMEX table is 

the buffer used for reading and writing the COTPRIME tape. The COTPRIME 

table is the buffer used as working storage while processing the individual 

records of the COTPRIME tape. The ASCOT table is the buffer used to build 

the ASCOT tape, and the ASCOTX table is the buffer used for writing the 

ASCOT tape. 

The main program reads the MOST tape and the COTPRIME tape. The 

COTPRIME buffer is designed to contain the record currently being processed, 

the last half of the previous record, and the record to be processed next. 

This is required as the targets necessary to complete each alternate group 

may occur earlier or later than the primary for that group. The COTPRIME 

table is a very large buffer defined as 500 entries (since each record is 

200 entries) at 23 words per entry. 

3.10.4.1 ADDMOST 

After reading the MOST tape, the program must then compute the start 

times for each target in the MOST table, since the main optics algorithm 

does not pass this information. These calculations are done in the procedure ADDMOST by the following equation: 

PPSTART = PPFIN - ((DELTAT1 + DELTAT2) + 

(DELTAS) (TT3-TT1)/(ASIG + BSIG)) 

where 

PPSTART = start time of Main Optics photography 

PPFIN = finish time of Main Optics photography 

DELTAT1 = forward photographic time as a function of mode 
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DELTAT2 = 

DELTAS = 

TT3 = 

TT1 = 

ASIG = 

BSIG = 

-SECRETID BIF-4-B10009-68 

Page 227 

aft photographic time as a function of mode 

stereo angle as a function of mode 

latest possible photography time 

earliest possible photography time 

maximum forward stereo angle for main optics 

maximum aft stereo angle for main optics 

3.10.4.2 TYPEFILT 

The procedure TYPEFILT is then called. This routine determines if the 

targets are visual intelligence targets (VITs), primaries, activity alternates, or weather alternates. It then checks the individual target type 

view flags which are input, and, if a particular type is not to be viewed, 

sets a flag (called the NOT OK FLAG) to prevent this type from being placed 

in the ASCOT table when it is constructed. The probability of activity and 

dwell time are set for all targets that are acceptable for viewing. The 

probability of activity is simply a percentage chance that any infrequent 

but unusually high intelligence value situation exists at the target site, 

while the dwell time is an input specifying the amount of time the crew has 

to look at a target through a scope before the scope moves to another target. 

3.10.4.3 GEOMFILT 

Having determined which of the targets are to be considered for viewing, it is necessary to determine which of them it is possible to view 

taking into account the physical limitations imposed on the system. This 

is done in the procedure GEOMFILT. For each target the NOT OK FLAG is 

checked and, if set, no further calculations are made for the target. For 

VITs and primaries that are to be viewed, target weights are computed. The 

weight equations will appear later, but it should be noted that the word 

defining the weight has two parts, a high order part and a low order part. 

The high order bits are used as flags to signal if the target is a mandatory 

ATS target (one that must be viewed) or a primary. The low order bits contain the actual computed weight in an integer form. The weights Are computed either considering or not considering probability factors depending 

upon the option requested by input. 

REi/ 
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1-E-RETID 

For targets other than VITs and primaries, i.e., activity or weather 

alternates, a NEARMOST table is generated. This is a table that contains 

the earliest and latest possible photographic times for the target if considered as an alternate for any nearby main optics targets. These earliest 

and latest times are calculated in the subroutines CALCALFA and CALCBETA. 

The latest possible main optics photography time is calculated, and the 

primary that this time is associated with is noted. Weights are then calculated for the activity and weather alternates. 

If probability factors for the various conditions are to be considered, 

the low order weights for all alternates are calculated by the equation: 

TWGTLO = PROBV [(TPROBA/100) (PROBREC) (TWA) + (1-TPROBA/100) 

(PROBFA) (TWI)] + (1-PROBV) [(TPROBA/100) (TWA) 

+ (1-TPROBA/100) (TWI)] 

low order weight, actual target worth 

probability of visibility 

probability of activity 

PROBREC = probability of recognition of activity 

nominal active weight 

probability of falsely reporting activity 

nominal inactive weight 

If probability factors are not to be considered, the low order weights 

for activity alternates are set equal to their nominal active weights 

TWGTLO = TWA 

and the low order weights for all other alternates are set equal to their 

normal inactive weights 

TWGTLO = TWI 

Using strictly hardware constraints, the earliest possible scope on 

time and the latest possible scope on time are calculated for each target. 

where 

TWGTLO = 

PROBV = 

TPROBA = 

TWA = 

PROBFA = 

TWI = 
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Page 229 

A 

Then, the latest possible decision time for the target as an alternate is 

calculated. This decision time is the time at which the main optics must 

begin maneuvering to photograph the alternate target and is calculated by 

the procedure CALCDECN. Unless there is a physical conflict, the actual 

latest possible scope on time is this decision time minus the dwell time. 

3.10.4.4 GENASCOT 

By now all the significant parameters necessary for each target for 

its consideration as an alternate have been determined, and the construction 

of the ASCOT table can begin. 

The ASCOT table construction is done in the procedure GENASCOT. The 

ASCOT buffer used during building of the ASCOT table is a 400 entry buffer. 

Because the ASCOT is first time ordered, and then ordered according to group 

number, it is necessary for several entries beyond those to be written out 

on tape to be processed and, consequently, properly ordered. This is 

accomplished by filling the entire 400 entry buffer, ordering the entire 

buffer, and then moving 200 of these entries to the ASCOTX buffer to be 

written onto tape. The remaining 200 entries are then used to start the 

next phase of table building, and any ordering to be done is not likely to 

reach back into the table beyond 200 entries. 

In the actual table construction, the program first checks the NOT OK 

FLAG for each target and those targets whose flag is set are not included 

in the table. ASCOT entries are made for all others. When the buffer is 

full, the entries are ordered by time and then group number. 

As was mentioned earlier, it is necessary to hold the group size below 

a certain maximum number of targets; each group in the ASCOT buffer is 

checked, and if there are too many in the group, it is sized. The group is 

ordered by weight, and a deletion flag is set for all targets beyond the 

maximum allowable number (and consequently, of lower worth). When the 

program prepares to write the ASCOT tape, it checks each entry, and those 

whose deletion flags are set are purged from the table. 

GENASCOT also calls the procedure WRTASCOT that determines if the 

ASCOT table is to be listed. 
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-SECIEND 

3.10.4.5 CALCALFA 

Procedure CALCALFA calculates the earliest possible time to start 

photography on an alternate target coming from a main optics target. The 

times at which the obliquity and stereo maneuvers are completed are calculated and the later of the two times is the earliest start time. 

After the difference in the obliquity between the main optics target 

and the alternate is determined, the time required to perform the obliquity 

maneuver to negotiate this angular change (a function of the RCURVE table) 

is found by solving the following equation: 

TESR = (BB - AL(SRMO))/(AL + MRMO) + SRMO 

where 

TESR = time required for obliquity maneuver 

BB change in obliquity between Main Optics (MO) and alternate 

AL = rate of obliquity change of the alternate target 

SRMO = settle time required by MO for given obliquity rates 

MRMO = obliquity rates for MO 

A similar calculation is then performed to determine the time required for 

the stereo maneuver. The equation for this calculation is: 

TESP = (PP - AA - GA(SPM0))/(GA + MPM0) + SPMO 

where 

TEST = time required for stereo maneuver 

PP = total target stereo angle traveled while photographing 

previous primary 

AA = total change in stereo while target is viewable 

GA = rate of change of stereo of target 

SPMO = settle time required by MO for given stereo rates 

MPMO = stereo rates for MO 

These maneuver times are added to the finish photography time of the previous 

primary to establish the earliest start time for the alternate. 
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Page 231 

3.10.4.6 CALCBETA 

4 CALCBETA determines the latest time that the MO may finish photography 

on an alternate and still maneuver to initiate photography of the next 

scheduled primary. Again, both the stereo and obliquity maneuvers must be 

considered, and the one taking the longer time is the constraining maneuver. 

By first finding the rate of obliquity change at the alternate and the 

difference in obliquities of the alternate and primary at the start time of 

photography for the primary, the time to complete the required obliquity 

maneuver is determined by use of the equation: 

TLFR = (BB + (MRMO) (SRMO))/(AL + MRMO) 

where 

TLFR = time required to complete obliquity maneuvers 

BB = difference in obliquites of the two targets 

MRMO = obliquity rate of the MO 

SRMO = settle times for obliquity rates of MO 

AL = rate of change of obliquity of alternate target 

This time combined with the time to start photography of the next primary 

gives the latest time to finish photography on the alternate considering the 

required obliquity change. 

For the stereo maneuver, the stereo angle at the start time of photography for the primary and the change in stereo angle at the alternate from 

first view time to the start time of photography for the primary are found. 

Then, the time required to complete the stereo maneuver from the alternate 

to the primary in time to start photography of the primary is calculated 

as follows: 

TLFP = (PP - AA + (MPM0)(SPM0))/(GA + MPMO) 

where 

TLFP = time to complete stereo maneuver 

PP = stereo angle at start time of photography to primary 
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change in stereo of primary by start time for photography 

stereo rate of MO 

settle time for stereo rate of MO 

rate of change of stereo at alternate 

The time to complete the stereo maneuver is combined with the start time of 

photography for the next primary to determine the latest time photography 

of the alternate can be concluded. 

The earlier of the latest times required for completion of the stereo 

and obliquity maneuvers is the latest time that the MO can complete photography of the alternate. 

3.10.4.7 CALCDECN 

When photography is finished on the previous primary and the main 

optics are maneuvering to the next projected primary, there exists a time 

at which it is still possible to decide to photograph an alternate instead 

of the primary. After this time it would be impossible to get to the alternate, perform the required photography, and return to the next primary. 

This latest time to start the maneuvering is called decision time and is 

calculated by the procedure CALCDECN. The calculation is performed by 

considering the time at which photography of the alternate must start to 

satisfy the conditions of the photographic mode requested and the latest 

time at which maneuvering must begin to return to the next primary. 

There are two equations involved in the calculation of decision time. 

If the maneuvering to the next primary is in the direction of the alternate, 

the equation used is: 

F4 = F2 - F3 + MM (STANT3 - STANT1 - SS)/(+ MM) 

where 

F4 = time increment from previous primary until maneuvering 

begins to alternate 

F2 = attitude (stereo or obliquity) of MO 

F3 = attitude (stereo or obliquity) of alternate 

MM = stereo or obliquity rate 

Page 232 

AA = 

MPMO = 

SPMO = 

GA = 
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STANT3 = 

STANT1 = 

SS = 

start time of photography for alternate 

end time of photography for previous primary 

settle time for this maneuver rate 

However, if the initial maneuver to the next primary is away from the alternate, the equation used is: 

F4 = (F3 + MM (STANT3 - STANT1 - SS) - Fl)/ (+. 2MM) 

where every term is the same as in the earlier equation and: 

Fl = attitude (stereo or obliquity) of previous primary 

3.10.4.8 WRTASCOT 

The ability to write out the ASCOT internal table is a function of 

input. If the proper bit of the input parameter OUTFLG is set, the ASCOT 

can be output on-line, off-line, or both. If the bit is not set, WRTASCOT 

does nothing. The procedure first calculates the number of ASCOT entries 

to be written, and then one entry at a time is taken from the ASCOTX buffer 

and moved to the locations used in the printout. After determining whether 

the output is to be on-line, off-line, or both, one line of output is 

generated by a call to the system routine OUTPUT. This listing of one 

entry at a time is continued until all ASCOTX entries have been processed. 
TWASCON 

Preset internal 

constants and rewind 

tapes 

(

Is there a 

MOST table? 

Yes 

Read MOST table 

into core buffer 

SKIPMOST 

o Initialize program 

constants 

o Preset additional 

constants 

o Zero COTPRIME buffer 

o Zero COTPRIMEX buffer 

RDCOTPR 

Zero COTPRIMEX buffer and 

read next COTPRIME record 

into COTPRIMEX buffer 

/ 

Was an end-of-file found Yes 

on the COTPRIME tape? 

No 

V 

Set end of 

COTPRIME tape 

flag 

Move COTPRIMEX buffer 

content into appropriate 

COTPRIME buffer location 

- 

Calculate number of COTPRIME 

entries read this time and 

total number of entries read 

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Page 234 

'SEC-RETID 

TWASCON TWASCON 

Figure 3-15. TWASCON Flow Chart 
NRO APPROVED FOR 

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Page 235 

TWASCON TWASCON 

ADMOST 

ADDMOST 

Calculate start time 

for MOST entries from 

finish time and mode 

TYPEFILT 

• Perform target type filtering 

• Set dwell time from COTPRIME 

or File 8 

• Set probability of activity 

from COTPRIME or File 8 

• Perform target parameter 

threshold filtering 

• Identify each target as a 

visual intelligence, primary, 

weather alternate, or activity 

alternate 

Figure 3-15. TWASCON Flow Chart (Continued) 
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11C-REILD 

TWASCON TWASCON 

GEOMFILT 

• Calculate weights of 

targets 

• Determine to which primary 

target will be an alternate 

• Determine earliest and 

latest allowable scope on 

time for target 

• Calculate latest possible 

decision time for target 

GENASCOT 

• Generate ASCOT table from 

remaining COTPRIME entries 

• Perform maximum group size 

filtering 

• Write ASCOT tape 

Increment COTPRIME index 

to locate absolute position 

in COTPRIME table 

WRTASCOT 

Print ASCOT 

internal table 

if requested 

WRTCTPR V 

Move the COTPRIME record 

just processed into the 

COTPRIMEX buffer for writeout 

( 

Write out modified COTPRIME 

record on tape 

Figure 3-15. TWASCON Flow Chart (Continued) 

EtIRETZ D 
CALCALFA 

Calculate earliest time can 

start photography of this 

target coming from nearby 

primary 

■ •■••=1.÷ 

CALLBETA 

Calculate latest time 

can end photography of 

this target and get to 

next primary 

CALCDECN 

Calculate latest possible 

decision time for this 

target 

1MWD NRO APPROVED FOR 

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Page 237 

TWASCON TWASCON 

Figure 3-15. TWASCON Flow Chart (Continued) 

'SEORMD 
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-SEC-RETAD 

TWASCON 

TWASCON 

(

Is flag set to output 

deletion comments? 

Yes 

Check NOT OK flag for 

each COTPRIME entry. 

If set, print appropriate 

deletion comment using 

switch COMCNTRL 

41 

ENDCTPR 

>---+ 

Is end of COTPRIME No 

tape flag set? 

Yes 

V 

Write end-of-file on 

output COTPRIME tape 

WRTEOF V 

Write second end-of-file 

on ASCOT tape to show 

end of tape 

Move COTPRIME entries 

up one record's worth in 

COTPRIME buffer 

(

Is flag set to output 

deletion comments? 

Yes 

Print statement giving 

number of targets deleted 

due to group size 

4 

Tir 

Print statement giving 

number of targets acquired 

by TWASCON 

RETURN 

Figure 3-15. TWASCON Flow Chart (Continued) 
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Page 239 

ADDMOST ADDMOST 

ADDMOST 

( Are there no 

MOST entries? 

N 

RICHECK 

Have all MOST entries 

been processed? 

No 

Yes 

)Yes 

(

Have all COTPRIME entries Yes 

in core at present been 

processed? 

No 

Calculate photography 

start time for MOST entry 

T 

RETURN ) 

Figure 3-15. TWASCON Flow Chart (Continued) 

ET/D 
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Page 240 

4E-RET1 D 

TYPEFILT TYPEFILT 

(

Have all COTPRIME entries 

been processed? 

Yes 

RETURN 

Should this type of 

target be viewed? 

Yes 

DWCHK 

Set dwell time and 

probability of activity 

01 

Set NOT OK flag 

and reason 

oD 

Figure 3-15. TWASCON Flow Chart (Continued) 

---SEGRETI D 
Set dwell time 

Are there any MOST 

entries? 

Yes 

Is this target a 

primary? 

ShOuld this type of 

target be viewed? 

Set NOT OK flag 

and reason 

--MEV D NRO APPROVED FOR 

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Page 241 

TYPEFILT TYPEFILT 

A 

Figure 3-15. TWASCON Flow Chart (Continued) 

--SKREftD 
V 

Set dwell time 

Should this type of 

target be viewed? 

Yes 

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Page 242 

--SECREVD 

TYPEFILT TYPEFILT 

PROBATST 

Set probability of activity 

(

Can this target be an 

activity alternate? 

Yes 

V 

---) 

Can this target be 

an weather alternate? 

Yes 

Set NOT OK flag 

and reason 

Figure 3-15. TWASCON Flow Chart (Continued) 

-SECIET1 D 
V 

Yes (

RETURN Have all COTPRIME 

entries been processed? 

Yes (

Has NOT OK flag for this 

COTPRIME entry already 

been set in TYPEFILT? 

No 

Is this a V.I. target? 

Is this a primary? 

Calculate weight of 

target 

Yes 

No 

Initialize parameters 

iYes 

Calculate weight of 

primary 

-SECRETID NRO APPROVED FOR 

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Page 243 

GEOMFILT GEOMFILT 

GEOMFILT 

Figure 3-15. TWASCON Flow Chart (Continued) 

---SEGREY-D 
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GEOMFILT GEOMFILT 

Yes 

Yes 

NOMONEAR ... 

Is this a V.I. target? 

N 

Figure 3-15. TWASCON Flow Chart (Continued) 

Are there any 

MOST entries? 

Set NOT OK flag and 

reason 

ALFABETA 
( Are there any nearby No 

primary targets? 

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GEOMFILT 

CHKFSTMO 

Generate NEARMOST table with 

earliest and latest possible 

photography time for this 

alternate considering, in 

turn, each nearby MOST entry 

GEOMFILT 

CALCALFA 

01 Calculate earliest time 

can start photography of 

this target coming from 

nearby primary 

CALCBETA 

Calculate latest time can 

end photography of this 

target and get to nearby 

primary 

4 

Yes 

WHICHMO 

Is this an activity Yes 

alternate? 

No 

V 

Calculate photographic 

mode duration for weather 

alternate or set to zero 

if V.I. target 

Figure 3-15. TWASCON Flow Chart (Continued) 
Set NOT OK flag and 

reason 

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-sfeitnin 

GEOMFILT GEOMFILT 

RKZERO 

Search for latest occurring 

primary to which this target 

can be an alternate 

K

Can this target be an No 

alternate to any primary? 

Yes 

Calculate latest possible 

main optics• on time for 

this alternate and specify 

which primary 

( Is this a V.I. target? )Yes 

No 

V 

Calculate weight of this 

weather alternate 

Figure 3-15. TWASCON Flow Chart (Continued) 

-IMMO 
K

Can this target be an 

alternate to any primary? 

ges 

Calculate latest possible 

main optics on time for this 

alternate and specify which 

primary 

Set NOT OK flag 

and reason 

TRYDECSN 

Search for latest occurring 

primary to which this target 

can be an alternate 

V 

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GEOMFILT GEOMFILT 

Figure 3-15. TWASCON Flow Chart (Continued) 
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BIF-4-B10009-68 

Page 248 

GEOMFILT 

GEOMFILT 

Calculate weight for this 

alternate 

CALCSCP1 V 

Is maximum allowable scope 

angle from vertical less 

than obliquity of target? 

No 

Set NOT OK flag and 

reason 

Yes 

V 

( Is maximum allowable obliquity Yes 

angle for scope less than 

obliquity of target? 

irNo 

Set NOT OK flag and 

reason 

Calculate earliest possible 

scope on time for this 

target 

Calculate temporary latest 

possible scope on time for 

this target considering 

only viewing and backstop 

aspects 

V 

Is this a V.I. target not Yes 

near a primary? 

Set decision time as 

latest possible scope 

on time plus dwell 

time 

N 

(

Is this target alternate 

to a primary? 

Set latest possible scope 

on time equal to photography start time minus 

(dwell time plus setup time) 

Figure 3-15. TWASCON Flow Chart (Continued) 

SECRET/ D 
SCOTST V 

Calculate latest possible 

scope on time from latest 

possible decision time minus 

dwell time 

Is temporary latest scope 

on time less than latest 

scope on time? 

Yes 

4 

NOBRNCH 

V 

Set latest scope on time 

equal to temporary latest 

scope on time 

CTDEC 

Set parameters necessary 

to perform latest possible 

decision time calculations 

CALCDECN 

Calculate latest possible 

decision time for this 

alternate target 

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GEOMFILT GEOMFILT 

Is earliest possible scope 

on time less than or equal 

to latest possible scope on 

time? 

Yes 

Figure 3-15. TWASCON Flow Chart (Continued) 

--SECREUD 
Set NOT OK flag and 

reason 

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-SECRET/ D 

GEOMFILT GEOMFILT 

Is this target a primary? 

Yes 

Set earliest possible scope 

on time 0.1 second earlier 

than latest possible scope 

on time 

TSCOP 

Set temporary ASCOT parameters in addended 

COTPRIME entry 

Set decision time as 

latest possible scope on 

time plus dwell time 

Figure 3-15. TWASCON Flow Chart (Continued) 

E RET/ D 
( Has complete COTPRIME Yes 

record been processed? 

RETURN 

Has end of COTPRIME 

flag been set? 

Yes 

V 

N )

( Have all COTPRIME Yes 

entries been processed? 

ORDER V 

Time order ASCOT 

entries 

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GENASCOT GENASCOT 

GENASCOT 

• 

01 

N 

• 

( Is NOT OK flag set for Yes 

N 

• 

Make ASCOT entry from 

this COTPRIME entry 

Is ASCOT buffer not Yes 

yet full? 

this COTPRIME entry? 

No 

Figure 3-15. TWASCON Flow Chart (Continued) 
HELL 

Do any necessary reordering 

of ASCOT entries so that all 

ASCOT entries of a group are 

together 

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--SE-6RE41 D 

GENASCOT GENASCOT 

04 

Have all ASCOT entries 

been processed? 

No 

Yes 

Determine total number 

of targets in this group 

(I

\ Are the total number of 

targets in the group not 

greater than maximum allowable? 

N 

V 

Generate table of all targets 

in the group ordered by weight 

of target 

V 

Set deletion flag for all low 

worth targets beyond maximum 

number allowable in a group 

Figure 3-15. TWASCON Flow Chart (Continued) 

-SEMI/ D 

Yes 
DELGRP 

No 

V 

Move up valid ASCOT entry in 

ASCOT buffer 

Is group size delete flag 

been set for this ASCOT entry? 

V 

Have all ASCOT entries 

been processed? 

Yes 

V 

Load ASCOTX buffer with 

record of ASCOT entries 

V 

Write a record of ASCOT 

entries onto ASCOT tape 

WRTASCOT 

Print out record of 

ASCOT internal table 

if requested 

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GENASCOT GENASCOT 

V 

Bump delete 

counter 

V 

lJ 

Yes 

Figure 3-15. TWASCON Flow Chart (Continued) 

'SEERET1D 
11, 

Move ASCOT entries up in 

buffer one record 

Yes 

WRTLAREC 1E------------ 

Load ASCOTX buffer with 

remaining ASCOT entries 

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11.6-MUD 

GENASCOT GENASCOT 

Have all COTPRIME entries 

been processed? 

Write remaining 

ASCOT entries on 

ASCOT tape 

o Write end-of-file on 

ASCOT tape 

o Set number of ASCOT entries 

1 

WRTASCOT 

Print out remaining ASCOT 

internal table if requested 

4 

( RETURN ) 

Figure 3-15. TWASCON Flow Chart (Continued) 

-SEC-REVD 
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CALCALFA CALCALFA 

CALCALFA 

Initialize parameters 

CALCTESR V 

Calculate earliest time 

to start photography on 

alternate coming from 

primary due to required 

obliquity maneuver 

CALCTESP 

Calculate earliest time 

to start photography on 

alternate coming from 

primary due to required 

stereo maneuver 

ALFACALC 

Calculate earliest time 

to start photography on 

alternate coming from 

primary 

( RETURN ) 

Figure 3-15. TWASCON Flow Chart (Continued) 

IEDRETI-D 
CALCTLFP 

Calculate latest time to 

finish photography on alternate 

and get to next primary considering required stereo maneuver 

BETACALC 

Calculate latest time to 

finish photography on alternate 

then going to next primary 

Initialize parameters 

CALCTLFR 

Calculate latest time to 

finish photography on alternate 

and get to next primary considering required obliquity maneuver 

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-MET/ D 

CALCBETA CALCBETA 

CALCBETA 

( RETURN ) 

Figure 3-15. TWASCON Flow Chart (Continued) 

11111E-T1 D 
(

Was this an obliquity Yes 

time calculation? 

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CALCDECN CALCDECN 

CALCDECN 

I. 

 Initialize flag for 

obliquity calculation 

V 

``Is this to be obliquity 

maneuver time calculation? 

Yes 

V V 

Initialize parameters 

for obliquity maneuver 

calculations 

Initialize parameters for 

stereo maneuver calculations 

4 

V 

Calculate latest possible 

time to initiate obliquity 

(or stereo) maneuver to 

alternate so that main optics 

can start photography at required time 

No 

V 

Calculate latest possible 

time to initiate maneuver 

to alternate so that main 

optics can start photography at required time 

( RETURN ) 

Figure 3-15. TWASCON Flow Chart (Continued) 

(REVERSE OF THIS PAGE LEFT BLANK) 

--SE-RETID 
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3.11 TWASSP2 

3.11.1 Purpose 

TWASSP2 is employed to determine the optimal acquisition scope strategy 

when either one or two scopes are to be utilized. The worth of an individual target is based on active priority, inactive priority, probability of 

activity, probability of visibility, probability of falsely reporting a 

target to be active or inactive, and obliquity weighting. The targets to 

be considered are obtained from the ASCOT, and the best score sequence down 

to and including each target is determined. 

In addition, the optimal decision time is determined for each target 

group. A target group consists of a single primary (or main optics) target 

plus a number of alternate targets. Both the primary and the selected 

alternates are to be viewed through the acquisition scopes, and the status 

of each target (active, inactive, cloudy, or mandatory override) reported 

to the onboard computer prior to decision time. A voting logic is then 

employed to determine which target should be photographed by the main optics. 

In order to ensure that any of the selected alternates can be photographed, 

a decision time must be selected that is compatible with the entire group. 

This group decision time is optimized by the algorithm through the use of 

an imbedding technique, in which multiple entries are made, when necessary, 

to allow for the possibility of variations in decision time. 

As is the case in the main optics algorithm, a list is generated that 

contains the optimal sequences down to and including each of the targets 

being considered. The best score path is determined by first scanning the 

list to find the target that completes the maximum score sequence and then 

using the predecessor information to determine which targets are contained 

in the sequence. The output of TWASSP2 is the Acquisition Scope Strategy 

Table (ASST), which provides the optimal acquisition scope target sequence. 

3.11.2 Input 

The ASCOT table, described in Section 3.10.3, and the THINGS table, 

described in Section 3.2.3, provide the information required by TWASSP2. 

The File 8 parameters required as input are depicted in Table 3-27. 
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--SEDRET/ D 

Table 3-27. File 8 Parameters Used in TWASSP2 

Located in Table THINGS 

File 

8 

Location 

Form 

of 

Data 

Nominal 

Value Units 

900 I 2 n.d. 

920 FP 20. deg/ 

sec 

921 FP 20. deg/ 

sec 

926 FP 1. sec 

940 I 25 n.d. 

Internal JOVIAL Internal Definition Symbol Def. Units 

Number of scopes NUMSCOP I 48 U n.d. 

in use:O=none, 56 0 

1=one scope, 

2=two scopes 

Obliquity slewing MRAS F rad/ 

rate for ATS 309 0 sec 

Stereo slewing MPAS F rad/ 

rate for ATS 310 0 sec 

Settle time SAS F sec 

for ATS 25 0 

Maximum number MAXLATE I 48 U n.d. 

of list entries 112 0 

allowed per target pair and 

decision time 

3.11.3 Output 

The output of TWASSP2 is the Acquisition Scope Strategy Table (ASST) 

intermediate data tape which contains the optimal target viewing schedule of 

the operating scopes. The format of the ASST is depicted in Table 3-28. 

Table 3-28. ASST Format 

Symbol JOVIAL 

Declaration Units Definition 

GCOTENT I 15 U 0 0 n.d. COTPRIME entry number 

GASCOT I 14 U 0 15 n.d. ASCOT entry number 

GGROUPNO I 14 U 0 29 n.d. Target group number 

GEXTRA I 4 U 0 43 n.d. Unused bits 

GPATH B 0 47 n.d. Target path: 

0 denotes Path 2 

1 denotes Path 1 

GWGT I 48 U 1 0 n.d. Target weight 

GTSTART F 2 0 sec Time scope initiates target 

viewing 

GDECIS F 3 0 sec Target group decision time 

Not printed out. 
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3.11.4 Method 

The optimal acquisition scope target sequence is determined by a front 

to end dynamic programming approach for both the case of one and two scopes 

being utilized. The recurrence relation, which is the basis of the acquisition scope target selection algorithm, is 

S. = wi + wk+ max S. 

Js m 

jEJ 

mEM 

.10m 

where 

S

ik = the maximum score possible starting before the rev distribut tion is encountered down to and including targets i and k 

w.1 = worth of target i 

wk= worth of target k 

J = set of all nonconflicting candidate predecessor targets 

of target i 

M = set of all nonconflicting candidate predecessor targets 

of target k 

j = immediate predecessor of i 

m = immediate predecessor of k 

A nonconflicting candidate predecessor target of target i must satisfy 

the following conditions: 

• It must be a target other than i or k. 

• Its earliest scope on time must be earlier than the earliest 

scope on time of i. 

The requirements for a nonconflicting predecessor of target k are equivalent. 

The reasoning behind Equation (1) is that since the score maximized 

paths to every valid predecessor pair j,m of target pair i,k have already 

been determined, this knowledge can be used to find the score maximized 

---SEMWD 

(1) 
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-1-ERETID 

A 

paths to target pair i,k. That predecessor pair j,m which, in conjunction 

with target pair i,k, yields the best score is chosen as the immediate 

predecessor pair of target pair i,k. Since the optimal paths to predecessors 

j

A and m have been previously determined, the optimal paths to targets i and 

k are now known. 

It is readily apparent that the solution for one scope being employed 

is just a special case of the solution for two scopes where variables k, m, 

and wk are not employed. 

It is necessary to include the selection of the group decision time 

(TD) in the acquisition scope target selection algorithm. Choosing an early 

group decision time can cause deletion of targets whose earliest possible 

scope on times plus dwell times terminate after this decision time. Choosing a late group decision time can cause the deletion of targets whose 

latest possible scope on times plus dwell times terminate before this decision time. The inclusion of the selection of the optimal (score maximizing) 

group decision time is accomplished by imbedding the above particular problem into the whole class of problems characterized by consideration of all 

the meaningful decision times (TD) for each group. 

The appropriate equation now becomes 

Si k(TD) = wi + wk+ max S. (TD) 

39m 

j eJ 

meM 

where TD is a particular decision time compatible with both targets i and k 

such that both the following relationships are simultaneously satisfied. 

A target group consists of a primary target plus feasible alternate targets 

for the main optics to photograph if it is determined by the onboard voting 

procedure to be more desirable to do so than to photograph the primary target. Such a situation can occur if bad weather conditions preclude photographing the primary target, or an alternate target is active while the 

primary target is inactive and the score of the active alternate target 

exceeds that of the inactive primary target. 

(2) 

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4k 

TFIRST + TDWELL < TD < TLAST + TDWELL. (3) 

TFIRSTk + TDWELLk < TD < TLASTk + TDWELLk 

(4) 

— — 

where 

TFIRST

x 

= earliest possible scope on time for target x 

TLAST

x 

= latest possible scope on time for target x 

TDWELL

x 

= length of time scope views target x 

All such compatible decision times are termed mutual decision times. 

It is initially assumed that each target is viewed commencing at its 

earliest scope on time TFIRST. If the scope is not able to maneuver from a 

target predecessor j to the target i rapidly enough to initiate viewing at 

time TFIRST, a conflict is said to exist. However, if the scope could 

maneuver to initiate viewing at a later time TLATEi where TLATEi < TLASTi, 

the conflict could be resolved. Therefore, it is necessary to include provisions for consideration of such possibilities in the algorithm to ensure 

that the solution will be optimal. A new target LATEi is designated with 

the same characteristics as target i, with the one exception that 

TFIRSTLATE. = TLATE. (5) 

Thus, TWASSP2 can be segmented as illustrated in Figure 3-16. The 

incorporation of group decision time and the conflict of the type described 

may be seen to have significant effect on the operation of the algorithm. 

To illustrate the methodology of the algorithm, the solution of a 

simplified example problem will be performed where there is one primary 

target (3) and three alternate targets (0,1,2) to be viewed by the acquisition scopes. The targets are depicted in Figure 3-17 and are time ordered by 

their earliest possible scope on time. The target parameters that are of 

primary importance in the algorithm are the following: 

TFIRST = earliest scope on time 

TLAST = latest scope on time 

TDWELL = scope dwell time 

-SECRET-1D 
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4EC-REVD 

Mutual Group 

Decision Time 

Selection 

Input 

(ASCOT) 

V 

01 Acquisition 

Scope Target 

 Selection Algorithm 

Output 

(ASST) 

----ON. Conflict 

4- Analysis 

Figure 3-16. TWASSP2 Function Flow Chart 
TFIRST

o 

TFIRST1 

TFIRST2 

TFIRST3 

 TLAST

o 

TDWELL / 

TD1 

TD TD 0' 2 

TD3 

Main Optics 

Dwell Time 

le__Primary 

Target 

TLAST1 

TLAST2 

TLAST3 

V 

Increasing 

Time 

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••• 

Target Weight 

Alternate 0 2 

Alternate 1 3 

Alternate 2 1 

Primary 3 10 

, 

/ Main Optics Path 

TARGET GROUP NUMBER = 1 

Figure 3-17. Example Target Distribution 
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--SEC-RET-/ D 

TD = latest possible decision time 

WGT = weight 

GROUP = group number 

and are given in Figure 3-17. 

The scope parameters that are of primary importance in the algorithm 

are the following: 

EGT920, MRAS = scope obliquity slewing rate 

EGT921, MPAS = scope stereo slewing rate 

EGT926, SAS = scope settle time 

The operation of the program will be specifically illustrated for two 

separate target pairs. The first example will be the illustration of the 

scope target selection algorithm and the mutual group decision time selection operation for the first target pair to be considered so that the 

initial pass through the program is depicted, and a general understanding 

of the program methodology can be obtained. 

The second example will be the illustration of the acquisition target 

selection algorithm and the conflict analysis processes for an arbitrary 

target pair, which will serve to provide a more comprehensive understanding 

of the program methodology as well as the construction of the Acquisition 

Scope Selection Table (ASST) which contains the optimal Path 1 and Path 2 

target selections. 

3.11.4.1 Example 1: Initial run through the acquisition scope 

target selection program 

MAIN PROGRAM (Executive Procedure) 

The procedure MAIN PROGRAM is the TWASSP2 executive routine. It 

defines all data and tables, performs program initialization, and inhibits 

multiple viewing of a target. 

TWASSP2 (MAIN PROGRAM Logic Block) 

TWASSP2 initializes the program variables and indices as well as 

rewinds the ASCOT, LIST, and ASST tapes. It calls procedures ASREAD and 

NEXTHIHK. 
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ASREAD (Procedure) 

The procedure ASREAD reads the ASCOT tape, which contains all the target information required for the determination of the optimal scope strategy, 

and loads the ASCOT buffer in core. Because of storage limitations, it is 

not possible to read the entire ASCOT tape into the ASCOT buffer. For convenience of data handling, a buffer entry number is assigned to each target 

entry when it is read into the ASCOT buffer. This entry number is related 

to the actual ASCOT entry number by the parameter ASCOTO, which provides a 

measure of the preceding ASCOT entries that have been stored and removed 

from the ASCOT buffer prior to the insertion of the current ASCOT entries. 

Thus, the actual ASCOT entry number is given by the sum of ASCOTO and the 

ASCOT buffer entry number. 

NEXTHIHK (Procedure) 

The first time that procedure NEXTHIHK is entered, the number of scopes 

to be employed is specified by the File 8 parameter: 

0, no scopes employed 

EGT900: NUMSCOP = 1, 1 scope employed 

2, 2 scopes employed 

However, the driver routine, TWONDER2, does not call the acquisition scope 

target selection algorithm if EGT900 = 0, so EGT900 will always be 1 or 2. 

The first pair (HI,HK) to be considered, as well as the applicable 

mutual decision times, are determined. Each succeeding time NEXTHINK is 

called, it determines the next target pair to be considered along with the 

applicable group decision times. Although in the equations previously 

developed targets were identified by lower case letters, the use of 

JOVIAL requires the following terminology to be employed. 

HI = target i (target viewed by Scope 1) 

HK = target k (target viewed by Scope 2) 

HN = entry number of target pair i,k 

IHM = predecessor j of i (viewed by Scope 1) 

KHM = predecessor m of k (viewed by Scope 2) 

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SE E ID 

HM = entry number of predecessor pair j,m of target pair i,k 

HISTART = first target in group (target with earliest TFIRST) 

The first target to be considered is that target in the first group 

with the earliest scope on time TFIRST. This is Target 0 and it is viewed 

first by Scope 1; thus, HI is set equal to zero. For the first target 

pair, it is assumed that no target is viewed by Scope 2. Such a case 

might occur if it would be optimal for Scope 2 to maneuver to view another 

target with a later TFIRST, while Scope 1 was viewing a target. HK is set 

equal to -1, which is a dummy value to indicate that Scope 2 is not viewing any target and is considered to be viewing a "pseudo target." Similarly, if Scope 1 was not viewing any target, HI would be set equal to -1. 

This target pair is then analyzed for every different compatible target 

decision time in the group. 

STORETDS (NEXTHIHK Logic Block) 

The decision times for all the targets in the group being considered 

are collected. These times would be TD0, TD1, TD2, and TD3. 

ORDERTDS (NEXTHIHK Logic Block) 

The decision times are now time ordered in the group decision time 

table: TD1, TD0, TD2, TD3. 

ONCEMOR (NEXTHIHK Logic Block) 

All entries with identical decision times are eliminated and the 

remaining entries are reindexed. Thus, since TD0 and TD2 are identical, 

only entries for TD1, TD2, and TD3 are made in the group decision time 

table. 

MUTUAL (NEXTHIHK Logic Block) 

The earliest and latest time bounds for decision times for each target of the target pair being considered are set by Equations (3) and (4). 

For target pair HI,HK(0,1), the Equation (3) requirement is: 

TFIRST0 + TDWELL0 < TD < TLAST0 + TDWELL

— — 0 (7) 
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Since target HK is a pseudo target, dummy values of zero and a) are entered 

for TFIRST-1 and TLAST-1' which results in Equation (4) allowing TD to be 

virtually unrestricted in magnitude. 

SETB1 (NEXTHIHK Logic Block) 

The earliest and latest time bounds for the mutual decision times of 

target pair HI,HK are set. Thus, TD is constrained by the greatest lower 

bound and the least upper bound of Equations (3) and (4). For the case of 

interest, both the earliest and latest bounds are given by Equation (3), 

and are TFIRST0 + TDWELL0 and TLAST0 + TDWELL0, respectively. 

BIB2 (NEXTHIHK Logic Block) 

The earliest and latest decision time bounds are checked to insure 

that the earliest bound is not greater than the latest bound, which implies 

that there is no decision time that is compatible for both targets. All 

valid decision times for this target pair are then stored. For the example, 

the valid mutual decision times are found to be TD1 and TD2, as TD3 

violates the latest bound.* 

BUMPHN (MAIN PROGRAM Logic Block) 

The first mutual decision time (TD1) is selected for the target pair 

HI,HK(0,-1) under consideration. 

SCREWUP2 (MAIN PROGRAM Logic Block) 

The mutual decision time specific parameters are initialized. The 

LIST entry number HN for the first target pair HI,HK(0,-1) for the first 

mutual decision time to be considered (TD1

) is set at 1. The current 

candidate predecessor and corresponding score indices are set to zero, and 

the LIST entry number HM of the first candidate predecessor pair to be 

tested is set equal to HN-1. 

The NEXTHIHK logic blocks which have not been described are not employed 

the first time that NEXTHIHK is entered and will be described in Example 2. 
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11 ft tr- T D 

HIHKPARS (Procedure) 

The ASCOT target parameter values are entered for the target pair 

HI,HK(0,-1). A list of these parameters is given in Table 3-29. 

CHECKTOP (MAIN PROGRAM Logic Block) 

The part of the LIST that contains target pair entries located in the 

LIST buffer is searched to determine if candidate predecessor pairs for 

the target pair HN(1) exist in core.* Since HN(1) is the first LIST 

entry, no predecessors exist as HM is zero. Thus, there are no possibilities 

of conflicts or of selecting a better solution because only one solution 

exists for specified decision time (TD1). Therefore, none of the conflict 

logic is required, and control is transferred to LISTGEN. 

Table 3-29. ASCOT Target Values Entered for Target Pair 

HI,HK(0,-1) Parameter Values 

Parameter 

Real Target 

HI(0) 

Pseudo Target 

HK(-1) 

COTPRIME entry number XCONTENTI -1 

Earliest scope on time XTFIRSTI 1.0 

Latest scope on time XTLASTI 1.0 

Scope dwell time XDWELLI 0 

Target weight XWGTI 0 

Target obliquity XOMEGAI 

Target group number XGROUPI XRGROUP (HI) 

Earliest main optics acquisition time XT1I - 

Time of interval between earliest and XT3T1I - 

latest main optics acquisition times 

* Only the part of the LIST stored in core is searched for predecessors to 

avoid excessive running time caused by data transfer into and out of core. 

111 R E D 
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Page 271 

LISTGEN (MAIN PROGRAM Logic Block) 

LISTGEN governs the selection of target-predecessor pair LIST entries 

as well as the future target pairs and mutual decision times to be considered.' It calls procedures GENLIST and NEXTHIHK. 

GENLIST (Procedure) 

The procedure GENLIST generates the LIST, which contains the best target predecessor LIST entry for a specified mutual decision time for each 

target pair. It also performs another task that will be discussed in 

Example 2. 

STARTER (GENLIST Logic Block) 

A LIST entry is made for the target pair mutual decision time under 

consideration. If the score obtained with this target pair is not exceeded 

by any previous score, the MAXIMER flag is set. The purpose of this flag 

is to facilitate the selection of an optimum predecessor pair for the target 

pair and will be more fully discussed in Example 2. 

For the case of the example initial target pair HN:HI,HK,TD(1:0,-1,TD1), 

an entry is made in the LIST buffer in the format depicted in Table 3-30. 

This analysis is then repeated for target pair (0,-1) for all the remaining 

mutual decision times (TD2). The target pair HI,HK,TD(0,-1,TD2) is given a 

LIST entry number of HN(2). 

After all the decision times have been considered for the target pair 

of interest, the procedure NEXTHIHK is entered to select the next target 

pair to be considered as well as the mutual decision times. 

3.11.4.2 Example 2: Arbitrary run through the acquisition scope target 

selection program 

Any run through the program subsequent to the first run for the initial 

target pair of LIST entry HN(1) originates in the procedure NEXTHIHK 

called by MAIN PROGRAM logic block LISTGEN. The analysis commencing with 

target pair LIST entry HN:HI,HK,TD(22:3,2,TD2) will now be illustrated to 

further explain the scope selection algorithm, the conflict analysis process, 

and the generation of the ASST. Since target pair LIST entry HN(22) is to 

be examined, the analysis has been concluded for previous target pairs 

LIST entries HN (1, ..., 21). The LIST that contains the best target 

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H 

H 

H 

0 H

H z

x •. Table 3-30. LIST Format for Target Pair 

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H 

1=4 0 

ci) 

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H 

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C_b 0 H 

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a, H

0 

H 

0 

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0 

0 

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is not generated in the LIST, but is presented to aid in the understanding of the algorithm. 
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predecessor LIST entry for a specified mutual decision time has already been 

constructed for these target pairs by use of Equation (1), and a modified 

version of it is depicted in Table 3-31. For the purpose of illustration, 

entries that would have been deleted because of violation of the requirement 

that the primary target may only be viewed by Scope 1 or because no mutual 

decision times exist are also shown in Table 3-31, as are the remaining 

entries, HN(22) and HN(23), to be made. Note that the format used in Table 

3-31 is not the actual LIST format previously illustrated, but rather a 

modified version which better illustrates the methodology of the algorithm. 

NEXTHIHK (Procedure) 

This procedure determines the next target pair to be considered as well 

as the mutual decision times. The list of all target pairs along with their 

mutual decision times is presented in Table 3-32. Note that if it is desired 

that primary targets always be viewed by a specific scope, all that is 

required is to delete those entries where a primary target is viewed by the 

other scope. Since, for the example being considered, all primaries are to 

be viewed by Scope 1 and Target 3 is the primary target, all entries where 

HK = 3 are deleted. Similarly, if only one scope is specified to be operating, all entries where Scope 2 is viewing a target are deleted, i.e., all 

entries other than HK = -1 are deleted. 

The analysis associated with target pair HI,HK,TD(3,2,TD2) of LIST 

entry HN(22) will now be illustrated to further explain the acquisition 

scope target selection algorithm and the conflict analysis. Since the 

procedure NEXTHIHK is not being entered for the first time, the initial 

NEXTHIHK logic block entered is THISTHAT. 

THISTHAT, IFHKPRIM, BUMPHI (NEXTHIHK Logic Blocks) 

These three logic blocks determine the next target pair to be considered. A description of each individual logic block is given first, and 

then an illustration of how they function together is presented. 

THISTHAT (NEXTHIHK Logic Block) 

This logic block switches the scope assignments for target pair HI,HK. 

Scope 1 is assigned the target currently assigned to Scope 2, and Scope 2 

is assigned the target currently assigned to Scope 1. The File 8 parameter 

-MEW) 
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-SECIEUD 

Table 3-31. Example Modified LIST 

Optimal 

LIST Mutual Predecessor Path 1 Path 2 

Entry Path 1 Path 2 Decision Path LIST MAXIMER Target Target 

Number Target Target Time Entry Flag Weight Weight Score 

HN/HM HI HK TD HM S

i wi wj 

--->1 0 -1 TD1 0 1 2 0 2 

2 0 -1 TD2 0 1 2 0 2 

3 -1 0 TD1 0 1 0 2 2 

4 -1 0 TD2 0 1 0 2 2 

5 1 -1 TD1 0 1 3 0 3 

6 1 -1 TD2 0 1 3 0 3 

7 -1 1 TD1 1 1 0 3 5 

8 -1 1 TD2 2 1 0 3 5 

9 1 0 TD1 0 1 3 2 5 

10 1 0 TD2 0 1 3 2 5 

11 0 1 TD1 0 1 2 3 5 

12 0 1 TD2 0 1 2 3 5 

13 2 -1 TD2 8 1 1 0 5 

14 -1 2 TD2 6 0 0 1 4 

15 2 0 TD2 0 0 1 2 3 

16 0 2 TD2 0 0 2 1 3 

17 2 1 TD2 0 0 1 3 4 

18 1 2 TD2 0 0 3 1 4 

19 3 -1 TD2 12 1 10 0 15 

20 3 -1 TD3 0 0 10 0. 10 

X -1 3 Deleted 

X -1 3 Deleted 

21 3 0 TD2 0 0 10 2 12 

X 0 3 Deleted 

X 3 1 None Deleted 

X 1 3 Deleted 

---->22 3 2 TD2 2 0 10 1 13 

X 2 3 Deleted 

---->23 Late 3 Late 2 TD2 12 1 10 1 16 

X Late 2 Late 3 Deleted 

* 

Maximum score solution 
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Table 3-32. Example Target Pairs and Mutual Decision Times 

LIST Entry 

HN 

1 

2 

Path 1 

Target 

HK 

0 

0 

Path 2 

Target 

HK 

-1* 

-1* 

Mutual 

Decision Time 

TD 

TD1 

TD2 

3 -1 0 TD1 

4 -1 0 TD2 

5 1 -1* TD1 

6 1 -1* TD2 

7 -1 1 TD1 

8 -1 1 TD2 

9 1 0 TD1 

10 1 0 TD2 

11 0 1 TD1 

12 0 1 TD2 

13 2 -1* TD2 

14 -1 2 TD2 

15 2 0 TD2 

16 0 2 TD2 

17 2 1 TD2 

18 1 2 TD2 

19 3 -1* TD2 

20 3 -1* TD3 

21 -1 3** 'TD 2 

22 -1 3** TD3 

23 3 0 TD2 

24 0 3** TD2 

25 3 1 None 

26 1 3** None 

27 3 2 TD2 

28 2 3** TD 2 

Only these entries are made if only one scope is employed, all others are 

deleted. 

** 

Entry is deleted if primary target must always lie on Path 1. 

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EGT900: NUMSCOP is employed to determine the number of operating scopes. 

If only one scope is being employed (NUMSCOP = 1), only pseudo targets 

(HK = -1) are allowed for Path 2, and all other target pair entries are 

deleted. 

Example: NUMSCOP = 2, therefore real targets are allowed on 

Path 2. 

IFHKPRIM (NEXTHIHK Logic Block) 

The entry HK is examined to determine whether the current target pair 

has a primary target on Path 2, which is disallowed. The validity of the 

current target pair is checked as well as whether this combination has 

been previously generated. If required, the Path 2 assigned target entry 

HK is incremented. 

Example: Primary Target 3 is on Path 1 as HI is 3. 

BUMPHI (NEXTHIHK Logic Block) 

The Path 1 assigned target entry, HI, is incremented, and it is 

determined whether all targets have been examined by observing whether the 

incremented value of HI exceeds the last target entry number in the ASCOT. 

If so, the flag DONE is set, and control is transferred to MAIN PROGRAM 

logic block ASSTGEN. 

Example: The last target entry number in ASCOT is 3. Since 

HI = 3, the ASCOT number is not exceeded, and the 

flag DONE is not set. 

MORASCOT (NEXTHIHK Logic Block) 

If more ASCOT entries are required to be placed in the ASCOT buffer, 

procedure ASREAD is called to read in another record of ASCOT entries into 

the ASCOT buffer. The top portion of the ASCOT entries are written over in 

core, the remaining ASCOT entries in the ASCOT buffer are moved up to 

the top portion, and the buffer target entry numbers are reset. 

SCREWUP1 (NEXTHIHK Logic Block) 

If the new Path 1 target is a member of the same group as the previous 

Path 1 target, control is transferred to MUTUAL; if it is a member of a 

new group, control is transferred to STORETDS, ORDERTDS, and ONCEMOR, where 

the decision times for all the targets in the new group are collected, 

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time ordered, and redundant entries deleted, respectively,' as previously 

described in Example 1. 

Example: The target pair of interest is HN:HI,HK,TD(22:3,2,TD2). 

Currently in storage is LIST entry HN:HI,HK,TD2 

(21:3,0,TD2). Logic block THISTHAT is entered and HI 

and HK areswitched, switched, resulting in HI,HK(0,3). Control 

is then transferred back and forth between NEXTHIHK 

logic blocks THISTHAT, IFHKPRIM, BUMPHI, MORASCOT, and 

SCREWUP1 until the next valid target pair is finally 

determined to be HI,HK(3,2). 

Control is then transferred to MUTUAL, SETB1, and B1B2, where mutual 

decision times are determined for the current target pair HI,HK. 

Example: The only valid mutual decision time for target pair 

HI,HK(3,2) is TD2. 

BUMPHN (MAIN PROGRAM Logic Block) 

The first mutual decision time is selected for target pair HI,HK. 

Example: For HI,HK(3,2), the first mutual decision time is 

TD2

. 

SCREWUP2 (MAIN PROGRAM Logic Block) 

The mutual decision time specific parameters are initialized, the 

LIST entry number HN for the target pair HI,HK(3,2) is set, the current 

score and predecessor indices are reset to zero, and the first candidate 

predecessor pair LIST entry number HM is determined. 

Example: HN = 23 

HM = 22 

HIHKPARS (Procedure) 

The ASCOT target parameter values are entered for the target pair 

HI,HK. 

Example: A list of these parameters is given in Table 3-29. 

CHECKTOP (MAIN PROGRAM Logic Block) 

The part of the LIST which contains target pair entries located in 

core is examined to determine if any candidate predecessor pairs for the 

target pair HN:HI,HK exist in core. If no entries exist, control is transferred to LISTGEN, where the target pair HN:HI,HK generates a new target 

pair chain. 
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Example: Candidate predecessor pair LIST entries 

exist for target pair HN(22). 

SEARCHUP and YESCON (MAIN PROGRAM Logic Blocks) 

The LIST is searched backwards starting from the immediately preceeding target pair HM(HN-1) for a predecessor pair which yields a score 

greater than presently achieved. If the search reaches the beginning of the 

LIST stored in the LIST buffer without finding a predecessor entry which 

yields a score greater than that achieved so far, control is transferred to 

LISTGEN, where a new target pair chain is generated. 

When a candidate predecessor pair HM:IHM,KHM,TD is chosen where IHM 

is the predecessor of target HI and KHM is the predecessor of target HK, a 

check is made to insure that neither target HI or HK is a predecessor of 

itself or of the other target. 

Example: HI 0 IHM or KHM, and HK # IHM or KHM 

Furthermore, checks are made to insure that targets HI and HK have not been 

included in any LIST entry that serves as a predecessor pair to entry 

HN:HI,HK,TD. If either HI or HK has been previously assigned to a scope, 

logic block YESCON determines if there are any more candidate predecessor 

pairs for the specified target pair. If so, SEARCHUP is repeated; otherwise, LISTGEN is entered. 

If neither HI or HK has been a predecessor of itself or the other 

target, control is transferred to CHKGROUP. 

Example: The LIST, which has been already calculated by use of 

Equation (2), is depicted in Table 3-31 for target pair 

HN:HI,HK,TD2(22:3,2,TD2). The immediate predecessor 

LIST entry for HN(22) is HM:IHM,KHM,TD(21:3,0,TD2). 

But for this case, target HI(3) is a predecessor of 

itself, and HM(21) is not a valid predecessor pair 

LIST entry for HN(22). The next candidate predecessor 

entry to be examined is HM(20). However, once again, 

HI is a predecessor of itself. Either HI or HK is a 

predecessor of itself or of the other for predecessor 

LIST entries HM(19) through HM(13), so these candidate 

predecessor pairs are also eliminated. The first candidate predecessor pair examined where such is not the 

case is HM:IHM,KHM,TD(12:0,1,TD2). 
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CHKGROUP (MAIN PROGRAM Logic Block) 

The current target pair LIST entry HN and the candidate predecessor 

pair LIST entry HM are examined, first, to determine if they belong to the 

same group, and, second, if they do belong to the same group, whether they 

have the same mutual decision time. If both target pairs belong to the 

same group and have the same mutual decision time, control is transferred 

to CONCON and the analysis is continued. If the groups or mutual decision 

times are different, examination of a different candidate predecessor pair 

is initiated by YESCON. 

Example: Since both candidate predecessor pair HM:IHM,KBM,TD 

(12:0,1,TD2) and target pair HN:HI,HK,TD(22:3,2,TD2) 

belong to the same group and have the same mutual 

decision time TD2, this test is satisfied. 

CONCON (MAIN PROGRAM Logic Block) 

Logic block CONCON controls the conflict analysis portion of the program. Its basic purpose is to determine whether a scope can maneuver to a 

target from a predecessor to initiate viewing at the earliest possible 

scope on time TFIRST. If such a maneuver is not possible, a conflict is 

said to exist. CONCON determines whether such a conflict can be eliminated 

by delaying the time at which the target is viewed, and if such is the case, 

whether the resulting score is worth the delay encountered. 

The procedures called by CONCON are HMPARS, ASSP2CON, and IKDELAY, 

and ASSP2CON calls procedure CONFLICT. HMPARS sets the LIST entry and 

ASCOT entry numbers for the candidate predecessor pair HM:IHM,KHM,TD. 

ASSP2CON, in conjunction with CONFLICT, determines whether the time 

required to maneuver the scopes from the candidate predecessor pair to 

the target pair results in an inability for either or both targets to be 

viewed at the earliest possible time scope on TFIRST. IKDELAY determines 

if it is possible to resolve the conflict by delaying the viewing of the 

target or targets in conflict and if the score obtained by doing so is 

worth the time delay, in which case this information is stored for future 

use. If a conflict is found to exist, CONCON transfers control to YESCON. 

If a no-conflict situation is found, CONCON determines if there can exist 

any predecessor pairs not yet tested which can yield a better score than 

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that obtained by the current best predecessor pair. This process is performed by use of the MAXIMER flag. The MAXIMER flag is set for every target 

pair LIST entry whose score is greater than or equal to that achieved by 

any previous target pair LIST entry. Thus, if a target pair HN:HI,HK,TD 

can have as a valid predecessor pair HM:IHM,KHM,TD for which the MAXIMER 

flag is set, it is impossible for the score achieved by choosing a predecessor pair for target pair HN whose entry number is less than HM to 

exceed this score, and no more predecessor pairs need be tested. That such 

is indeed the case can be best illustrated by referring to LIST entry 

HN(20) in Table 3-31. The score is 10 and the MAXIMER flag is not set. 

Thus, it is possible for a target pair with an earlier LIST entry to yield a 

better score, which is indeed the case for LIST entry HN(19), which attains 

a better score of 15. However, since the MAXIMER flag is set for HN(19), 

no target pair with an earlier LIST entry, i.e., HN(1) through HN(18) can 

have a better score, as can be seen in Table 3-31. 

If the MAXIMER flag is set for the candidate predecessor pair, no 

more predecessor pairs will be tested, and control is transferred to LISTGEN. 

If the flag is not set, control is transferred to CHECKTOP where another 

candidate predecessor pair will be tested. 

Example: The MAXIMER flag is set for LIST entry HM(12) so there 

is no possibility of attaining a better score by considering target pairs with LIST entries of less than HN(12). 

However, predecessor pair LIST entry HM(12) is found to 

conflict with target pair LIST entry HN(22). Therefore, 

at the conclusion of the conflict analysis for predecessor 

pair HM(12), testing of a different candidate predecessor 

pair is initiated by YESCON. The results of this predecessor testing will be summarized below, and a discussion 

of the conflict analysis procedure for HM(12) will commence 

with the description of the procedure HMPARS. 

Target pairs HM(11,9,7,5,3) are rejected by CHKGROUP 

because their mutual decision times are different from 

that of target pair HN(22). Target pairs HM(10,8,6,4) 

are rejected by CONCON as both predecessors conflict with 

the targets of target pair HN(22). Predecessor pair 

HM:IHM,KHM,TD(2:0,-1,TD2) is found to be a valid predecessor 

pair of target pair HN(22), as the mutual decision times 

are the same and there is no conflict. Since the MAXIMER 

flag is set for HM(2), the score achieved by choosing this 

predecessor cannot be exceeded by searching back for additional predecessor pairs. Since both targets of target 
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pair HI,HK(3,2) are being viewed at the earliest possible 

times, no time saving can be obtained by use of another 

predecessor pair. Thus, the predecessor pair search is 

terminated and control is transferred to LISTGEN. 

HMPARS (Procedure) 

Procedure HMPARS sets the LIST entry and ASCOT entry numbers for the 

candidate predecessors HM:IH,KHM,TD to be examined in conflict analysis. 

Example: Predecessor pair HM:IHM,KHM,TD (12:0,1,TD2) will be 

examined. 

TESTIHM and TESTKHM (HMPARS Logic Blocks) 

Candidate predecessors IHM and KHM are examined to determine whether 

they are real predecessors of HI and HK or pseudo predecessors where Scopes 

1 or 2 is setting up for HI or HK, respectively, rather than actually 

viewing a target. 

Example: For target pair IHM,KHM(0,1), both targets IHM and KHM 

are real targets as neither are equal to -1. 

MIPARS and MKPARS (HMPARS Logic Blocks) 

The LIST entry of the real predecessor of HI is stored in TEMPHMI, and 

the LIST entry of the real predecessor of HK is stored in TEMPHMK. The 

ASCOT entries of the real predecessors are also stored in the ASCOT buffer. 

TRIP1 and TRIP2 (HMPARS Logic Blocks) 

If either the immediate predecessor of HI or of HK is not real, a 

real earlier predecessor LIST entry is searched for in core. If none is 

found, the corresponding predecessor is left as a pseudo target and a noconflict relationship is assumed. If a real predecessor LIST entry is 

found, control is transferred to MIPARS or MKPARS, where its LIST and 

ASCOT entries are stored. 

ASSP2CON (Procedure) 

ASSP2CON, in conjunction with the procedure CONFLICT, determines 

whether a conflict exists between the candidate predecessor pair and the 

specified target pair, and if so, the magnitude of the conflict. CONFLICT 

determines the time required for the scopes to maneuver from the predecessor 

pair to the target pair, and ASSP2CON determines if this required time causes 

a conflict. 

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ASSP2CON (ASSP2CON Logic Block) 

If the candidate predecessor target IHM is a pseudo target, the ASCOT 

entry of IHM is not in core, i.e., no data for target IHM is stored in core, 

or the current target is a pseudo target, control is transferred to HOOKONI, 

where a no-conflict situation is designated for HI and IHM. A similar procedure is performed for the Path 2 target and candidate predecessor by 

KAYBABY. Otherwise, the following target and predecessor parameters listed 

in Table 3-33 are set for conflict analysis. 

Example: The time at which the stereo and obliquity maneuver from IHM(0) 

to HI(3) is completed is computed in procedure CONFLICT and 

is given by the parameter BAUMTE. This time is then compared 

to the earliest scope on time for target HI(3), TFIRST. 

If it exceeds TFIRST3, a conflict is said to exist as it 

is impossible for the scope to view the target at the 

earliest possible time. For the example, BAUMTE < TFIRST; 

thus no conflict exists. 

HOOKONI (ASSP2CON Logic Block) 

A no-conflict condition is noted for the Path 1 target and predecessor, 

HI and IHM by setting the conflict flag YACON to zero, and inputting zero 

into CONI, which gives the magnitude of any conflict. 

KAYBABY (ASSP2CON Logic Block) 

Logic Block KAYBABY is a duplicate of ASSP2CON for the Path 2 target 

and predecessor HK and KHM. 

Example: The time at which the stereo and obliquity maneuver from KHM(1) 

to HK(2) is given by BAUMTE, and exceeds TFIRST2 indicating 

that a conflict exists. This results in the conflict flag 

YACON being set, and magnitude of the conflict, BAUMTE -

TFIRST2 is stored in CONK, i.e., CONK = BAUMTE-TFIRST2. 

HOOKONK (ASSP2CON Logic Block) 

It is indicated that a no-conflict condition exists for the Path 2 

candidate predecessor and target in the same manner as done in HOOKONI. 

CONFLICT (Procedure) 

The procedure CONFLICT computes the time at which both the stereo and 

obliquity maneuvers from a candidate predecessor to a target are completed. 
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Table 3-33. Target and Predecessor Parameters 

Set For Conflict Analysis 

Parameter 

Candidate 

Predecessor Target 

Time of internal between 

earliest and latest main 

optics acquisition times 

BIRNT BAUMT 

Earliest main optics 

acquisition time 

BIRNTT1 BAUMTT1 

Scope departure 

time 

BIRNT1 -- 

Obliquity BIRNO1 BAUM01 
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CONFLICT (CONFLICT Logic Block) 

The time at which the completion of the obliquity maneuver, including 

the settle time, occurs is computed by use of the equation: 

TER = BIRNT1 + IDELOI /MRAS + SAS (8) 

where 

TER = time at which obliquity maneuver is completed 

BIRNT1 = time at which scope departs predecessor 

DELO = difference in obliquity of predecessor and target (rad) 

MRAS = EGT920, scope obliquity slewing rate (rad/sec) 

SAS = EGT926, scope settle time (sec) 

BOMB1 (CONFLICT Logic Block) 

The time at which the completion of the stereo maneuver, including the 

settle time, occurs is computed by use of the equation 

TEP = TEP1 + BIRNTI + SAS (9) 

where 

TEP = time at which stereo maneuver is completed 

TEP1 = time required for pitching of scope which is a function 

of EGT921, MPAS, the scope stereo slewing rate (rad/sec) 

BIRNT1 = time at which scope departs predecessor 

SAS = EGT926, scope settle time (sec) 

SETTE (CONFLICT Logic Block) 

The larger of TER and TEP is specified to be the time at which the 

stereo and obliquity maneuver from predecessor IHM to target HI is completed 

and stored as BAUMTE This process is later performed for predecessor 

IHK and target HK. 

IKDELAY (Procedure) 

If a conflict exists, procedure IKDELAY determines if the conflict 

can be eliminated by delaying the viewing times of the targets in conflict, 

and if the resulting score is worth the delay encountered. If so, a LATEIK 

entry is made to save this information. 
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IKDELAY (IKDELAY Logic Block) 

It is first determined if the start of the delayed viewing time of 

the target for which a conflict exists exceeds the latest allowable target 

viewing start time TLAST, i.e., is TLATE > TLAST. If so, the conflict is 

not resolvable, the target pair HM:IHM,KHM,TD containing the conflicting 

predecessor is not an acceptable predecessor pair, and the procedure IKDELAY 

is exited. 

Example: TLATE3 < TLAST3 and the delayed starting time is acceptable. 

The next test is whether the delayed target viewing start time plus 

the dwell time TDWELL exceeds the group decision time TD presently being 

considered, i.e., if the relation TLATE + TDWELL > TD is true. If this is 

the case, it will be impossible to complete viewing of the target before 

it is necessary to make a decision as to which target in the group shall be 

viewed by the main optics. Thus, the conflict is not resolvable and procedure IKDELAY is exited. 

Example: TLATE3 + TDWELL3 < TD2 and the decision time is compatible. 

If the analysis currently being performed is for the first time that 

the viewing time for target HI and/or HK of LIST entry HN has been delayed, 

control is transferred to NEWLATER, otherwise control is transferred to 

CHKDELAY. 

NEWLATER (IKDELAY Logic Block) 

If there is no conflict, the procedure IKDELAY determines whether or 

not the number of late entries (i.e., the number of times the viewing times 

of either or both targets of HN:HI,HK,TD have been delayed by different 

amounts) exceeds the maximum number allowable, which is specified by 

EGT940, MAXLATE. If EGT940 has been exceeded, the procedure IKDELAY is 

exited and no entry is made for the case under consideration. The EGT940 

parameter is required because of core storage limitations and is currently 

set at 15. Thus for each target pair HN:HI,HK for the specified decision 

time TD, there are 15 entries allowable for delayed viewing times. If the 

EGT940 parameter is not exceeded, a LATEIK entry is made containing: 
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• Delayed viewing start time(s) 

• Score 

• Predecessor LIST entry number 

Example: These values are: 

D 

Late entry number 

Tentative LIST 

entry number 

Target 3 delayed 

viewing time 

Target 2 delayed 

viewing time 

Score 

Predecessor LIST 

entry number 

LATECNT 1 

HATE 23 

(HN+LATECNT) 

TSTART3 TFIRST3 

TSTART2 TLATE2 

SSCORE HM(23) 16 

GOODHM (23) 12 

After a late entry is made, the late entry counter is incremented by 

one and control is transferred to CHKDELAY. 

CHKDELAY (IKDELAY Logic Block) 

The current candidate LATEIK entry is compared with all valid late 

entries previously generated for this particular target pair and decision 

time HN:HI,HK,TD(22:3,2,TD2). If the current candidate LATEIK entry has 

the same or greater score than a previous entry and is delayed less in time, 

the old late entry is deleted and the process is repeated for another valid 

late entry. 

If the current candidate LATEIK entry has the same or less score than 

a previous late entry, and it is delayed more in time, no late entry is 

made for it. Otherwise, a new late entry is made for the current candidate 

LATEIK entry. In both cases, the procedure IKDELAY is then exited. Thus, 

only entries are kept which either improve the score previously obtained or 

lessen the amount of time delay. 

Example: The candidate LATEIK entry is the first late entry 

considered for target pair HN:HI,HK,TD(22:3,2,TD2) 

and the score of 16 is better than any previous 

entry. Thus, a late entry is made. 
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LISTGEN (MAIN PROGRAM Logic Block) 

LISTGEN governs the selection of target-predecessor pair LIST entries 

as well as the future target pairs and mutual decision times to be considered. 

It calls procedures GENLIST and NEXTHIHK. 

GENLIST (Procedure) 

GENLIST generates the best target-predecessor pair LIST entry for a 

specified mutual decision time, and generates all valid LATEIK LIST entries 

for this specified mutual decision time. 

STARTER (GENLIST Logic Block) 

A LIST entry is made for the current target pair HN:HI,HK,TD 

Example: LIST entry HN(22) is made for target pair HI,HK(3,2) for 

decision time TD(TD2). The score is calculated by use 

of Equation (1) 

S

3,2 = w3 + w2 + Max S. 

301 

to be 13 where 

jeJ 

mcM 

53,2 = 13 

w3 = 10 

w

2 = 1 

j = 0 

m = -1 

0,-1 = 2 

If the score achieved by this target under consideration is greater 

than or equal to all previous scores, the MAXIMER flag is set and control 

is transferred to LISTOUT. 

Example: For target pair HN(22), the score of 13 is exceeded by the 

score of target pair HN(19), which is 15. Consequently, 

the MAXIMER flag is not set for HN(22). 

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ANYLATER (GENLIST Logic Block) 

If there are no late entries to be made where the viewing times of 

target HI and/or HK have been delayed, control is transferred to LISTOUT. 

Example: There is one late entry to be made for target pair 

HI,HK,TD(3,2,TD2). In reality, there are many more 

possibilities that can be generated by the conflict 

analysis procedure. But it would serve no useful purpose 

in this document to list all these possibilities, so it 

will be assumed that the only valid late entry for the 

example problem is the one described. 

ADDLIST (GENLIST Logic Block) 

If the score obtained for each LATEIK LIST entry is greater than or 

equal to all previous entries, the MAXIMER flag is set. 

Example: A LATEIK entry is made in procedure IKDELAY logic block 

NEWLATER for target pair HI,HK,TD, which has a score given 

by the expression 

SLATE3,LATE2 = w3 + w2 + Max Sj,m(12) 

jeJ 

meM 

where 

sLATE3,LATE2 = 16 

w

3 = 10 

w

2 = 1 

= 0 

m = 1 

S0,1(12) = 5 

The score of 16 exceeds all previous scores so a LIST entry 

HN(23) is made for this case and the MAXIMER flag is set. 

LISTOUT (GENLIST Logic Block) 

If a LIST printout is requested, a new batch of LIST entries is 

printed out. 
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BOTTOMCK (GENLIST Logic Block) 

If the LIST buffer in core is almost full, it is necessary to make 

room for potential future LIST entries by removing earlier entries from 

the LIST buffer and storing them outside core. The top portion of the 

LIST entries is written out, the remaining LIST entries in the LIST 

buffer are moved up to the top portion, and the indices are reset. Thus, 

each target pair can possess two LIST entry numbers, one being a true or 

absolute LIST entry number, which starts from the first target pair considered in the program, and a relative LIST entry number, which identifies 

the target pair when it is located in the LIST buffer. 

If all mutual decision times for the target pair have been considered, 

the next target pair is determined by procedure NEXTHIHK. 

NEXTHIHK (Procedure) 

This procedure determines the next target pair to be considered and 

has been previously described. 

Example: The next target pair is HI,HK(2,3). However, this target 

pair is rejected by logic block IFHKPRIM as Target 3 is a 

primary target and cannot be assigned to Path 2. Since 

this is the last target pair to be considered, the DONE 

flag is set in BUMPHI, and control is transferred to MAIN 

PROGRAM logic block ASSTGEN. 

ASSTGEN (MAIN PROGRAM Logic Block) 

ASSTGEN controls the generation of the Acquisition Scope Selection 

table (ASST), which yields the optimum target scheduling for Path 1 and 

Path 2. 

GENASST (Procedure) 

GENASST reconstructs the optimum sequence of LIST entries from the 

LIST to form the LISTX, which has the same format as the LIST. The ASST 

tape is then formed from the LISTX tape. GENNASST calls the procedure 

READLIST, which enters target and predecessor pair LIST entries into core 

for the formulation of the LISTX. 

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ILEVIEVD 

AREYOUIT (GENASST Logic Block) 

The LIST buffer is searched for the LIST entry HN that has the maximum 

score. This entry will be the largest LIST entry number for which the 

MAXIMER flag is set. If such an entry does not exist in the LIST buffer, 

procedure READLIST is called to read more LIST entries into the LIST buffer, 

and the process is repeated until such an optimum LIST entry is found. 

Example: The LIST entry for which the maximum score is 

obtained is HN(23). 

EUREKA (GENASST Logic Block) 

The maximum score LIST entry is entered in the LISTX, in this case 

HN(23). 

ROBLSO (GENASST Logic Block) 

The LIST buffer is searched for the optimal predecessor pair LIST 

entry, which is specified by the optimal target pair LIST entry. If it is 

not in the LIST buffer, procedure READLIST is called to read more LIST 

entries into the LIST buffer. Since each target pair LIST entry always 

contains the LIST entry of the predecessor pair, the determination of the 

optimum predecessor pair LIST entry is no problem. This LIST entry is then 

read into the LISTX. 

Example: The LIST entry of the optimal predecessor pair is HM(12). 

ATTOP (GENASST Logic Block) 

If all predecessor pair LIST entries for the maximum score paths have 

not been entered into LISTX, the process initiated by EUREKA is continued. 

If all LISTX entries have been made, the LISTX is then time ordered and 

the target groups are seqentially renumbered. 

Example: The LISTX consists of LIST entries HN(12) and HN(23) 

and is presented in Table 3-34. 

READLIST (Procedure) 

READLIST reads more LIST entries from the LIST tape into the LIST 

buffer. This procedure is required because there is not sufficient room 

in the LIST buffer to store all of the LIST entries. Because some LIST 
Table 3-34. Example Time Ordered LISTX 

Mutual 

Decision 

Time TDECIS 

N 

A 

Er 

t11 

P 

E-4 

P4 

41 

4 00 ,--, _1 

1 44 

Predecessor 

LIST Entry 

Number 

PREDNUM 

0 

C■4 

1-1 

Total 

Score 

SUMSCOR 

in %I:4 

1--1 

Start of Scope 

Target View Time 

Path 2 TSTARTK 

TFIRST1 

TLATE2 

Path 1 

TSTARTI 

TFIRST

o 

TFIRST3 

LISTX 

Entry 

Number 

HN 

CV 

r4 

el 

CN4 

4) 

4 

00 

444 

CU 

4) a) 

Path 2 

WEIGHTK* 

en ,-4 

Path 1 WEIGHTI 

00 CV 0 

$-1 

4111 

rI 

P Numberof LIST Entries 

for Target Pair and 

Specified Decision Time 

LISTCNT 

r--1 CV 

ASCOTTarget 

Entry Number 

Path 1 Path 2 

ASCOTI ASCOTK 

4-4 eN1 

o el 

Group Number 

GROUPNO 

1-4 1-I 

COTRIME Target 

Entry Number 

Path 1 Path 2 

COTPI COTPK 

I-I C*4 

0 el 

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BIF-4—B10009-68 

Page 291 
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Page 292 

'SHAW D 

entries are in the LIST buffer and the remainder are not, it facilitates 

matters to assign to each LIST entry a buffer entry number in addition to 

its actual entry number. These two entries are related by the parameters 

LISTO and LISTDROP. LISTO represents the number of entries written out of 

core, and LISTDROP represents the number of entries written out each time 

a write out of the LIST is required. 

LISTXOUT (GENASST Logic Block) 

The LISTX is printed out if requested. 

NOLISTX (GENASST Logic Block) 

Individual ASST entries are formed from the LISTX entries, and all 

pseudo target LISTX entries are eliminated since they are no longer required. 

ORDERAST (GENASST Logic Block) 

The ASST entries are time ordered. 

Example: The time ordered ASST entries are presented in Table 3-35 

Scope 1 views Target 0 at the earliest possible on time 

TFIRSTnand then views the primary Target 3 at the earliest 

possible on time TFIRST3. Scope 2 views Target 1 at the 

earliest possible on time TFIRST1 and then views Target 2 

at the delayed time TLATE2. 

ASSTOUT (GENASST Logic Block) 

The ASST is printed out if requested. 

NOASST (GENASST Logic Block) 

The ASST tape is written; the format has been previously illustrated 

in Table 3-28. 
r-I 

denotes Path denotes Path 

O 1-1 

Table 3-35. Acquisition Scope Selection Table (ASST) 

if-DREVD 

Group 

Decision 

Time 

GTDECIS 

CV 

A E-1 

cN 

A Hi 

CN 

A H 

c..4 

A 

H 

Scope 

View Start 

Time 

H 

H 

cn 

H 0 

TFIRST

o 

TFIRST1 

TFIRST3 TLATE2 

4-1 

OJ 

bi) 

I.1 

cd 

HI 

1., 

4 

oti 

.1.4 a) 

3 

C.D 

3 

H 

0 

CNI M 0 

H 

,—I 

4-+ 

cu 

OD 

ca 

H 

A 

cd 

a 

is -K 

CNI 1-1 

o H 

GPATH 

r-i 0 0 ,--i 

4-1 

W Ca 

gi 

E-4 

a Z 0 

0 

1-1 a) _0 ei 

z 

Z 

GGROUPNO 

H H H H 

ASCOTENTRY 

Number 

E-1 0 0 tr) 

<4 0 

o H cn N 

COTPRIME Entry 

Number 

43 

E-4 0 0 

0 

0 ,--1 en csi 

H U) 

GO 

P-. $.4 

4-i 

0 

41 

P (i) .Cl 

E 

Z 

Z 0 

H c's I m 

-SKREVD 

BIF-4-B10009-68 

Page 293 
Ili Read ASCOT tape and 

load ASCOT buffer in core 

ASCOT 

AS READ 

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11C-REI/ D 

TWASSP2 TWASSP2 

C TWASSP2 ) 

TWASSP2 

Initialize program 

variables and indices, 

and rewind ASCOT, LIST, 

and ASST tapes 

V 

BUMPHN V 

V 

NEXTHIHK 

Determine first target 

pair (HI, HK) and 

applicable mutual group 

decision times 

Select first mutual 

decision time for target 

pair 

SCREWUP2 

Initialize decision time 

specific parameters for 

target pair 

Figure 3-18. TWASSP2 Flow Chart 

'SERE-t1 D 
• 

( Has predecessor search Yes 

N 

• 

K

Is either target of current 

LIST entry HN a predecessor 

of itself or of the other 

target? 

reached top of LIST? 

'SECRET/ D NRO APPROVED FOR 

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TWASSP2 TWASSP2 

HIHKPARS 

Set conflict analysis 

parameters for target 

pair 

110 

CHECKTOP 

Has predecessor search ) Yes 

N 

SEARCHUP 

• 

Search up LIST for predecessor entry HM of 

current LIST entry HN 

which yields a score 

greater than achieved so 

far 

reached top of LIST? 

Figure 3-18. TWASSP2 Flow Chart (Continued) 

'SEM/ D 
Initiate conflict 

analysis 

• 

ASSP2CON 

Yes 

V 

HMPARS 

Set conflict analysis 

parameters for predecessor 

pair IHM or KHM of LIST 

entry HM 

CONCON 

CONFLICT 

Determine time at which 

slewing maneuver (stereo 

and obliquity plus settle 

time) of scopes from predecessor pair to target 

pair is completed 

• 

IKDELAY 

If a conflict exists determine 

if it can be eliminated by 

delaying viewing times of 

either or both of the target 

pair, and whether the resulting 

score exceeds that obtained using 

a predecessor pair other than HM. 

If so, make a LATEIK entry which 

saves this information 

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TWASSP2 TWASSP2 

CHKGROUP 

• 

K

Do current and candidate 

predecessor LIST entry 

group numbers differ or 

are their mutual decision 

times the same? 

Figure 3-18. TWASSP2 Flow Chart (Continued) 

SICREZD 
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Page 297 

TWASSP2 TWASSP2 

V 

( Does a conflict exist? 

) Yes 

V 

Update current best predecessor 

pair LIST entry number and score 

V 

(

Can score of current best predecessor 

pair be exceeded? 

Yes 

V 

CF) 

Figure 3-18. TWASSP2 Flow Chart (Continued) 
LISTGEN 

-T> No 

V 

GENLIST 

Generate best target - predecessor list 

entry for a specified mutual decision time 

and generate all valid LATEIK list entries 

for the same target pair and decision time 

Have all mutual decision times for 

target pair been considered? 

> 

Determine next target pair and 

mutual decision times 

NEXTHIHK 

Yes 

ASSTGEN V 

GENASST 

Reconstruct optimum sequence 

of LIST entries (LISTX) from 

LIST. Form ASST from LISTX 

and write ASST tape 

READLIST 

Enter target and 

predecessor pairs 

LIST entries into 

core for LISTX 

formulation 

ASST 

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TWASSP2 

YESCON 

Are there any other LIST entries to be 

examined as candidate predecessor 

pairs for the specified target pair? 

(

Have all appropriate combinations of N0

target pairs been processed? 

00p 

V 

( RETURN ) 

Figure 3-18. TWASSP2 Flow Chart (Continued) 

ITOREVD 
Is this the first time 

the procedure is entered? 

Yes 

ORDERTDS V 

STORETDS 

Collect decision times 

for all targets in this 

group . 

Time order the decision 

time entries in the group 

decision time table 

ONCEMOR 

Eliminate entries with 

identical decision times 

and reindex remaining entries 

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11011E1/ D 

BIF-4-B10009-68 

Page 299 

NEXTHIHK NEXTHIHK 

NEXTHIHK 

NEXTHIHK 

Figure 3-18. TWASSP2 Flow Chart (Continued) 
NRO APPROVED FOR 

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BIF-4-B10009-68 

Page 300 

MIC-RETAD 

NEXTHIHK NEXTHIHK 

MUTUAL 

Set earliest and latest time 

bounds for decision time for each 

of the targets HI and HK in the 

target pair 

SETB1 V 

Set earliest and latest time bounds 

for decision time compatible with 

targets HI and HK 

B1B2 

• 

Is there a valid interval of 

decision times compatible with 

both targets? 

Yes 

• 

Store all valid mutual decision 

times for this target pair HI, HK 

• 

( RETURN ) 

Figure 3-18. TWASSP2 Flow Chart (Continued) 
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Page 301 

NEXTHIHK NEXTHIHK 

Yes 

THISTHAT V 

Switch the targets of the target 

pair to be considered on path one 

and path two 

• 

Does number of operating scopes 

equal one? 

File 8 parameter - EGT 900: 

number of operating scopes 

N 

• 

Oi

Allow only psuedo' 

targets for path two 

Does this combination of targets 

and paths have the primary target 

on path two? 

Yes 

• 

Has this combination of 

targets and paths been generated 

previously or is it otherwise 

invalid? 

a 

Figure 3-18. TWASSP2 Flow Chart (Continued) 
Yes 

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Page 302 

'SEIREVD 

NEXTHIHK NEXTHIHK 

BUMPHI 

Select next target for path 

one 

(

Have all targets been Yes 

examined? 

Set DONE 

flag .---10( RETURN 

MORASCOT II 

Are more ASCOT 

entries required 

in core? 

N 

Yes 

ASREAD 

Read another record 

of ASCOT entries 

into ASCOT buffer 

4 1 

SCREWUP1I v 

Is the new target a member 

of the same group as the 

previous target considered 

(whose group decision times 

are presently stored and ordered)? 

Figure 3-18. TWASSP2 Flow Chart (Continued) 
XIPARS 

(XKPARS) 

Input ASCOT target parameter 

values for target HI (HK) 

COTPRIME entry number 

Earliest scope on time 

Latest scope on time 

Scope dwell time 

Weight 

Obliquity 

Group number 

Earliest main optics acquisition 

time 

Time between earliest and latest 

main optics acquisition times 

HIHKPARS 

(HKEQMI) 

Is HI (HK) a real target, 

i.e., does scope 1 (2) 

view an actual target or 

is it in the process of 

setting up for viewing a 

succeeding target while 

scope 2 (1) views target 

HK(HI)? 

Input dummy target parameter 

values for HI (HK) 

NRO APPROVED FOR 

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Page 303 

ti 

HIHKPARS HIHKPARS 

HIHKPARS) 

( RETURN 

Figure 3-18. TWASSP2 Flow Chart (Continued) 
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BIF-4-B10009-68 

Page 304 

E G R E 

HMPARS HMPARS 

HMPARS 

TESTIHM 

(TESTKHM) 

Is IHM (KHM) a real predecessor 

of target HI (HK), i.e., was 

scope 1 (2) not previously setting 

up for HI (HK) but actually 

viewing a target? 

TRIP1 

(TRIP2) V 

Does the real predecessor LIST 

entry for HI (HK) exist in core? 

Leave IHM (KHM) as a psuedo target 

and assume a no conflict relationship later in ASSP2CON 

Yes 

Yes 

MIPARS 

(MKPARS) V 

Store list entry of real predecessor 

for HI (HK) in TEMPHMI (TEMPHMK) and 

store ASCOT entry of real predecessor 

for HI (HK) in IHM (KHM) 

11, 

C RETURN ) 

Figure 3-18. TWASSP2 Flow Chart (Continued) 
No 

ANYLATER 

• 

Are there any LATEIK entries 

to be made where the viewing 

times of HI and/or HK have 

been delayed? 

Yes 

ADDLIST 7 

Make LIST entries for all cases 

where the score is improved by 

delaying the viewing times of 

HI and/or HK 

SEGi NRO APPROVED FOR 

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BIF-4-B10009-68 

Page 305 

GENLIST GENLIST 

GENLIST 

STARTER 

• 

Make LIST entry for 

target pair HI, HK 

Is score obtained with target Yes 

pair HI, HK greater than or 

equal to all previous scores? 

(

Is score obtained with this LIST entry No 

greater than or equal to those obtained 

with all previous entries? 

Yes 

• 

Set MAXIMER flag 

Set MAXIMER flag 

Figure 3-18. TWASSP2 Flow Chart (Continued) 
LISTOUT 

Is LIST printout 

requested? 

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Page 306 

IEGREVD 

GENLIST GENLIST 

Yes Print out new batch 

of LIST entries 

BOTTOMCK 

Is LIST buffer 

full? 

almost 

Yes 

Write out top portion of 

LIST, move remaining portion 

up in buffer, and reset 

indices 

( RETURN 

Figure 3-18. TWASSP2 Flow Chart (Continued) 
Set conflict flag appropriately 

and determine how much (if 

any) conflict exists between 

candidate predecessor and target 

Set candidate predecessor 

parameters for conflict 

analysis 

Set current target parameters 

for conflict analysis 

CONFLICT 

Determine time at which 

slewing (stereo and obliquity) 

maneuver from predecessor 

to target is completed 

V 

( Is this first path HI/IHM? Yes 

No 

V 

RETURN 

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Page 307 

ASSP2CON ASSP2CON 

(ASSP2CON 

/\)

\ Is candidate predecessor IHM (KHM) 

of current target HI (HK) a psuedo 

target or is the ASCOT entry of 

IHM (KHM) not in core? 

(

Is current target HI(HK) 

a psuedo target? 

HOOKONI 

(HOOKONK) 

ASSP2CON 

(KAYBABY) V 

Yes 

ONO 

Yes 

Assume no conflict exists 

between current target HI(HK) 

and candidate predecessor target 

IHM (KHM) 

Figure 3-18. TWASSP2 Flow Chart (Continued) 
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BIF-4-B10009-68 

Page 308 

11C-REILD 

CONFLICT CONFLICT 

( CONFLICT ) 

CONFLICT 

Compute time at which obliquity 

and settle maneuver from tentative 

predecessor to target is completed 

File 8 parameters - 

EGT920: obliquity slewing rate 

EGT926: settle time 

BOMB1 

Compute time at which stereo and settle 

maneuver from tentative predecessor 

to target is completed 

File 8 parameters - 

EGT921: stereo slewing rate 

EGT926: settle time 

SETTE 

Obtain the larger of the two 

required times 

( RETURN 

Figure 3-18. TWASSP2 Flow Chart (Continued) 
 Yes 

NEWLATER 

Is this the first time that 

the viewing times for HI and/or 

HK have been delayed? 

V 

1EGREIL D NRO APPROVED FOR 

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Page 309 

IKDELAY IKDELAY 

IKDELAY 

IKDELAY 

V 

Does start of delayed viewing time Yes 

exceed latest allowable target 

viewing start time? 

No 

V 

(

Does delayed target viewing start 

decision time? 

time plus dwell time exceed group 

Yes 

No 

Does a conflict exist? 

1Yes 

Does number of late entries 

exceed maximum number allowable? 

File 8 parameter - 

EGT940: maximum number of 

LIST entries allowable per target and 

decision time 

No 

Make LATEIK entry containing: 

Delayed viewing start times 

Score 

Predecessor LIST entry number 

Bump late entry counter 

(: RETURN ;) 

Figure 3-18. TWASSP2 Flow Chart (Continued) 

1-ECREU D 

Yes 
Yes 

Has entry been compared 

with all previously 

generated LATEIK entries? 

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BIF-4-B10009-68 

Page 310 

110RETID 

IKDELAY IKDELAY 

CHKDELAY V 

Compare current tentative LATEIK 

entry with all valid late entries 

previously generated for this 

particular target pair HI, HK 

decision time combination 

Can this entry be delayed less 

in time than a previous entry 

and have the same or greater 

score than did that previous 

entry? 

Yes Delete previous 

LATEIK entry 

Is this entry delayed more 

in time than a previous late 

entry and does it have the same 

or lesser score? 

No 

Do not make a late entry 

with current tentative 

LATEIK 

V 

RETURN D 

Figure 3-18. TWASSP2 Flow Chart (Continued) 
ROBLSO 

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Page 311 

Yes 

Y ATTOP 

GENASST GENASST 

Is optimum predecessor 

LIST entry stored in core? 

Have all predecessor LIST No 

entries in optimum paths 

been entered in LISTX? 

Yes 

• 

Time order LISTX and sequentially 

renumber target groups 

) 

Read more LIST 

into LIST buffer 

READLIST 

Figure 3-18. TWASSP2 Flow Chart (Continued) 

) 

Read more LIST 

into LIST buffer 

READLIST 

GENASST 

• 

AREYOUIT 

Search LIST buffer from bottom 

for entry HN with maximum 

score (MAXIMER = 1) 

V 

Enter LIST entry into 

LISTX 
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--SEDREW 

GENASST GENASST 

LISTXOUT 

Is LISTX printout 

requested? 

No 

4 

NOLISTX 

• 

)Yes 

Oi

Print out 

LISTX 

Break apart LISTX entries into individual 

ASST entries neglecting all psuedo targets 

in LISTX 

ORDERAST V 

Time order ASST entries 

ASSTOUT 

Is ASST printout requested? 

4 

NOASST 

(: :l 

Write ASST Tape 

Yes 

01 

Print out 

ASST 

( RETURN 

Figure 3-18. TWASSP2 Flow Chart (Continued) 
--SEG-REVD NRO APPROVED FOR 

RELEASE 1 JULY 2015 

BIF-4-B10009-68 

Page 313 

3.12 TWOUT 

3.12.1 Purpose 

The subfunction TWOUT is the basic output routine for TWONDER. The 

inputs to this routine are the COTPRIME, the MOST and the ASST. The following basic types of output are available for listing: 

. Main Optics Strategy 

. ATS Strategy 

. Results of expected score calculation per target 

. Rev summaries of the above three items. 

Computations are required in TWOUT for the required output parameters. 

Since only the essential information pertaining to target selection 

is contained in the MOST and ASST, the detailed characteristics of the 

selected targets, photographic sequences, ATS viewing, target worth, and 

expected score per target group are computed. 

3.12.2 Input 

The following input tables are required by TWOUT: 

a. COTPRIME (see Section 3.6.3) 

b. MOST (see Section 3.9.3) 

c. ASST (see Section 3.11.3) 

d. THINGS (see Section 3.2.3) 

e. ALSO (see Section 3.2.3) 

The File 7 and File 8 parameters used by TWOUT, and located in table THINGS, 

are shown in Table 3-36. 

Input arrays located in table ALSO are depicted in Table 3-37. 

3.12.3 Output 

Samples of the listable outputs provided by the subfunction TWOUT 

are provided in Table 3-38. In addition to these listable outputs the 

table PATHDATA is passed via tape to TWPLOT1 with the information required 

for plotting of the Main Optics and ATS strategies. The content of this 

table is shown in Table 3-39. 
H 

cd 

U) 

a) 

• 

4-1 

4-1 

H 

c"

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Definition 

U) iJ 

O 

H 

0 a) 

a 0 

rl H 

ca 

O z 

r, CO 0 

a) R:1 4.1 

"--1 0 co 

rl ca C.) 

PT..1 0 

File 7 and File 8 Param

eters Used in TWOUTLocated in Table THINGS Table 3-

36. 

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0 ZS 

LL C•I 

0 ›- 

> 

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CC o L1.1 

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a w 0 

CC 

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BIF-4—B10009-68 

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v-1 r-I r-I C11 CV CV ty1 C•1 C.1 

01 01 ON 01 ON 01 CT■ ON ON 

H H H E-I 0-1 E-I H H H 

CD a 0 0 0 0 0 0 0 4.1 r.T.3 41 r.T4 44 r..1 r..3 r7.3 

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Parameters Us

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tinu

ed) co a) 

•

r4 

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PRIMARY TARGETS 

Table 3-38. 

TWONDER 

21 
BIF-4-B10009-68 

Page 318 

1114907725 

TOTAL WEIGHTS 

9761144936 VIT 9616228682 TOT GROUP 

EXPECTED WEIGHT SUMMARY(TOTALS) FORREVNUMBER 

VEHICLE 9999 

REVS 6 THRU 6 

PAGENUMBER 20 

PAGE NUMBER 18 

ER OF ACTIVE SCOPES 

NUMBER OF ACTIVE SCOPES 

RUNNUMBER 

EXPECTED WEIGHT INFORMATION FOR 

Table 3-38. TWOUTOutput (Continued) 

O z 

H 

REVS 6 THRU 6 

VEHICLE 9999 
NRO APPROVED FOR 

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BIF-4-B10009-68 

Page 319 

Table 3-38a. Target Card Data Key 

Item Description 

IP Priority (inactive) 

D Target diameter (ft x 10-1) 

ALT Target altitude (ft x 10-2) 

SHD Shade factor 

Photo mode weighting function 

CC Country code 

ESS Exposure setting sequence 

AP Priority (active) 

DPA Desired pitch angle (+ deg) 

STF Scan target flag 

BMF Benchmark flag 

MF Mandatory flag 

PA Probability of activity (%) 

SVT Specified ATS view time 

(sec x 10-1) 

PWF Pitch weighting function 

TGT ID Target identifier 

WF Weather factor 

RR Resolution requirement (in.) 

SCC Special category code 

LATITUDE Target latitude (deg, + = north) 

LONGITUDE Target longitude (deg, + = west) 

VIF Visual intelligence flag 
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Table 3-38b. Main Optics Selection Key 

Item Description 

S.ANG Sun elevation 

SLNTRNG Slant range (n.mi.) 

VEH.ATL Vehicle altitude (n.mi.) 

TIME ON Time "ON" (system time, sec) 

OBLIQ Obliquity (deg) 

STEREO Stereo angle (deg) 

M Mode 

CONVANG Stereo convergence angle 

WEIGHT Operation weight 

Table 3-38c. ATS Selection Key 

Item Description 

S.ANG Sun elevation angle (deg) 

SLNTRNG Slant range (n.mi.) 

VEH.ALT Vehicle altitude (n.mi.) 

TIME ON Time "ON" (system time, sec) 

TIME OFF Time "OFF" (system time, sec) 

OBLIQ Obliquity (deg) 

STEREO Stereo angle (deg) 

VERT.ANG Average angle from vertical (deg) 

WEIGHT Operation weight 

DEC.TIME Decision time (system time, sec) 

PT Primary target flag 

GR.NO. Group identifier 

SN Scope number 
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Page 321 

Table 3-39. 

Symbol JOVIAL Declaration 

PLTTON F 0 00 

PLTTOFF F 1 00 

PLTIDL H 8 2 00 

PLTIDR H 2 3 00 

PLTGRNO I 14 U 4 00 

PLTITEM I 2 U 4 46 

PLTDLT1 I 4 U 5 0 

PLTDLT2 I 4 U 5 4 

PLTDECT F 5 0 

PLTOBLQ F 6 0 

3.12.4 Method 

Table PATHDATA 

Definition 

Beginning of main optics photo sequence 

or ATS tracking sequence in system time 

End of main optics photo sequence or 

ATS tracking sequence in system time 

Left 8 characters of target ID 

Right 2 characters of target ID 

Group number if ATS selection 

Type selection: 0=MO, 1=ATS1 2=ATS2 

Time duration. 1st half stereo 

sequence if MO 

Time duration, 2nd half stereo 

sequence if MO 

Group decision time (system) if ATS 

Target obliquity from COTPRIME table 

The subfunction TWOUT combines the data available in the input tables 

(COTPRIME, MOST, and ASST) and performs the computations necessary to provide 

the listable output. Flow charts for TWOUT and the key procedures used by 

TWOUT are provided in Figure 3-19. Essentially, three types of computation 

are performed by this subfunction. These are: 

a. Computation of Main Optics Strategy output parameters 

b. Computation of ATS Strategy output parameters 

c. Computation of expected score per target group 

These computations are performed by the procedures OUTMO, OUTSC and EXWGTSC 

described in Sections 3.12.4.1 through 3.12.4.3. 

3.12.4.1 OUTMO 

The first line of the Main Optics output (as shown in Table 3-38) includes target specific parameters obtained directly from the COTPRIME table. 

Parameters defining Main Optics photographic activity are given on the 
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-1E-RETID 

second line. These parameters are determined from the information available 

in the COTPRIME and MOST tables. The MOST table contains only the information necessary to define (not fully describe) the Main Optics Strategy. 

The following items are stored in the MOST for each target which is part of 

the strategy: the COTPRIME entry number of the selected target, the photographic mode, and the time of completion of the photographic sequence for 

the target. Given the photographic finish time MOT2, the photographic start 

time is calculated from the equation 

PT = (it1 + Lit2) + AE(t3 - t1) / (A-B) 

The parameters Litt , Ott, and AE are determined as a function of photographic 

mode from File 8 input parameters defined by EGT150 through EGT179. The 

difference (t3 - t1

) is the elapsed time from first acquisition to last 

acquisition. These parameters are obtained from the COTPRIME table for 

the particular target being considered. The quantity (A-B) is the total 

change in stereo angle from first acquisition to last acquisition. These 

parameters are defined by the File 7 parameters SEV063 and SEV065. The 

stereo angle (E), obliquity (0), and slant range are then determined at the 

midsequence time t: 

t = (MOT1 + MOT2)/2 

E = (t - t1) - B)/(t3 - t1) - A 

O = (t - t1) (03 - 01)/(t3 - t1) + 01 

SR = SR (tca)/ cos (E) 

where 

1 = obliquity at first acquisition time 

0

3 

= obliquity at last acquisition time 

SR(tca) = slant range at time of closest approach 

These parameters are obtained from the COTPRIME. 
--SECREUD NRO APPROVED FOR 

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Page 323 

The remaining parameters on the second line of the Main Optics outputs 

are obtained directly from the input tables with the exception of target 

weight. The target weight is calculated by the method described in 

Sections 3.7 and 3.8. 

3.12.4.2 OUTSC 

The ATS output is determined from the data available in the COTPRIME 

and ASST tables. Since dwell time is available in the COTPRIME and target 

worth is available in the ASST, the only calculations required are for the 

determination of stereo angle (E), obliquity (Q), and slant range (SR). 

These parameters are determined at an average time (t) by the method described in Section 3.12.4.1. 

3.12.4.3 EXWGTSC . 

Procedure EXWGTSC computes the expected score of each target group 

generated and stored in the ASST by the ATS target selection algorithm. 

EXWGTSC sums the expected scores of all target groups in each rev to determine the expected score of each rev. 

A target group as output by TWONDER consists of a primary target, 

alternate targets and/or visual intelligence targets. EXWGTSC does not 

include visual intelligence targets in the computation of expected score; 

therefore, for the purposes of EXWGTSC a target group consists only of the 

primary target and it's alternates. 

The probability that a target j is reported by a crew member as being 

active is 

pA(j) = P{RA}(j) = PA(j) PITPR+ (1-PA(j))PVPF 

where PA(j) = Probability of activity of target j 

V = Probability of visibility (EXWGTSC employs the 

same value of P

V for all targets) 
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-SEGRETID 

P

R 

= Probability of recognition of activity (EXWGTSC 

employs the same value of PRfor all targets) 

P

F 

= Probability of false alarm, that is, reporting an 

inactive target active (EXWGTSC employs the same 

value of P

F 

for all targets) 

The probability that the target j is reported inactive is 

PI(j)= P {RI}(j) = PA(j) PV 

 (1-PR) + (1-PA(j)) PV (1-PF) 

The expected worth of a target j if reported active is 

WA(j) 

= E(W/RA)(j) = (WA(j) PA(j) PvPR+ WI(j) (1-PA(j)) PvPF)/pA(j) 

The expected worth of target j if reported inactive is 

WI(j)= E(W/RI)(j) = (WA(j)PA(j) 

 P

V(1-PR) + WI(j) (1-PA(j)) Pv(1-PF))/PI(j) 

where WA(.) = the basic active worth of target j 

WI(j) = the basic inactive worth of target j. 

The expected score of a target group is computed as follows: 

1. The quantities WA, p

A and WI, p

I are computed for each target. 

2. For each W (regardless of subscript A or I) and corresponding 

p the quantity w is computed 

w = x p fl (1 - 

M 

p(m)) II (1 - P

v

) 

N 

where M is the set 

417

A 

A> TT (then 

N is the set 

and TI > W. 

3. The expected score 

of the w's. 

of targets in the group such that either 

p(m) = PA) or WI > W (then p(m) = pi) 

of targets in the group such that WA> 171 

of the target group is computed as the sum 
-MEVD NRO APPROVED FOR 

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BIF-4-B10009-68 

Page 325 

P

V' 

the probability of visibility, is specified through File 8 parameter 

EGT937. PR' 

the probability of recognition, is specified through File 8 

parameter EGT924. PF, the probability of false alarm, is specified through 

File 8 parameter EGT923. 
NRO APPROVED FOR 

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Page 326 

--SKRETAD 

TWOUT 

TWOUT 

TWOUT 

Set selection plot flag 

INTIAL 

Perform general 

initialization 

INTIMO 

Perform initialization 

for MO output 

(

Is there at least one 

entry in the MOST table? 

Yes 

OUTMO 

Calculate and print payload 

parameters including score for 

each item in the optimal sequence 

of the MO. Also calculate and 

print summary (totals) for each 

rev. In addition calculate MO plot 

parameters. 

(

Was the COTPRIME tape found to 

be readable in OUTMO? 

No 

Clear selection plot flag 

( RETURN ) 

Yes 

Figure 3-19. TWOUT Flow Chart 
-SEG-REVD NRO APPROVED FOR 

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Page 327 

TWOUT 

WARPATH 

Write MO selection on tape 

for plotting purposes 

INTISC 

Perform initialization for 

ATS output 

TWOUT 

(

Was ATS output selected and 

is there at least one entry 

in the ASST? 

Yes 

OUTSC 

Calculate and print payload 

parameters including score for 

each target in the optimal 

sequence of the ATS. Also 

calculate and print summary 

(totals) for each rev. In 

addition calculate ATS plot 

parameters. 

(

Was the COTPRINE tape found to 

be readable in OUTSC? 

Yes 

EXWGTSC 

Calculate and print expected 

score for each ATS group. 

Also calculate and print 

expected score summary for 

each rev. 

V 

4 

V 0UT99 

) 

Write ATS selection on tape 

for plotting purposes 

WARPATH 

RETURN 

Figure 3-19. TWOUT Flow Chart (Continued) 

1E-RgiD 
TREAD(MOST) 

Read first MOST record 

OUT2 

ACQN 

RETURN ) 

Find entry number of 

current MOST entry OUT5 

PRNTSM 

Print rev summary 

ACQCP 

Find matching COTPRIME 

entry number 

OUTMO 

TREAD(COTPP) 

Read first COTPRIME record 

PHIC 

Compute score for current 

target using stereo weighting function 

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Page 328 

--SEDREW-D 

OUTMO OUTMO 

Figure 3-19. TWOUT Flow Chart (Continued) 
SETL1 

Set up buffers for printing 

of target specific payload 

parameters for the current 

target 

OUT2+5 

Calculate selection specific 

payload parameters for printing 

SUMMO 

Perform rev summary bookkeeping 

OUT2+22 • 

Compute and store selection plot 

parameters 

OUTLMO 

Print out previously calculated 

payload parameters for the 

current target 

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Page 329 

OUTMO OUTMO 

V 

Figure 3-19. TWOUT Flow Chart (Continued) 

--SEGRETI-D 
Yes 

RETURN Is this a "NO 

PRINTOUT" case? 

OUTLMO 

(

Is it time to begin 

a new page? 

1Yes 

PGEHDR 

Complete current page 

and begin new one 

K

Is this the first line 

of the current page? 

Yes 

No 

Print MO specific page 

headers online and/or 

offline 

Print target specific 

line header online and/ 

or offline 

LINE1 

Print target specific 

line data 

NRO APPROVED FOR 

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Page 330 

--SEC-RETI D 

OUTLMO OUTLMO 

Figure 3-19. TWOUT Flow Chart (Continued) 

SEG-RETi-D 
NRO APPROVED FOR 

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Page 331 

OUTLMO OUTLMO 

03 

Print MO specific line 

header online and/or 

offline 

V 

OUTPUT 

Print MO specific data 

online and/or offline > 

( RETURN 

Figure 3-19. TWOUT Flow Chart (Continued) 
Read first COTPRIME record 

TREAD(COTPP) 

)

Read first ASST record 

TREAD(ASST) 

RET2 

) 

Find entry number of 

current ASST entry 

ACQN 

Yes 

RET5 

PRNTSC 

Print rev summary )

) 

Find matching COTPRIME 

entry number 

ACQCP 

SETL1 

Set up buffers for printing 

of target specific payload 

parameters for current target 

RET2+4 V 

Calculate selection specific 

payload parameters for printing 

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Page 332 

-SECTRETI D 

OUT SC OUT SC 

OUTSC 

Is End-of-file 

on ASST tape? 

No 

RETURN 

Figure 3-19. TWOUT Flow Chart (Continued) 

11414.1/ D 
1-EGRETID NRO APPROVED FOR 

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Page 333 

OUTSC OUTSC 

SUMSC 

Perform rev summary bookkeeping 

OUTLSC 

Print out previously calculated 

payload parameters for the 

current target 

V 

Calculate and store selection 

plot parameters 

Figure 3-19. TWOUT Flow Chart (Continued) 
Yes 

RETURN Is this a "NO 

PRINTOUT" case? 

OUTLSC 

No 

V 

Is it time to 

begin a new page? 

Yes 

PGEHDR 

Complete current 

page and begin 

new one 

Is this the 1st 

line of the 

current page? 

4 

Yes 

V 

Print ATS specific 

page headers online 

and/or offline 

Print item specific 

line header online 

and/or offline 

NRO APPROVED FOR 

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Page 334 

-SECRETID 

OUTLSC OUTLSC 

Figure 3-19. TWOUT Flow Chart (Continued) 
-SEGRETID NRO APPROVED FOR 

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BIF-4-B10009-68 

Page 335 

OUTLSC OUTLSC 

LINE1 

Print target specific 

line data 

V 

Print ATS specific 

line header online 

and/or offline 

V 

OUTPUT 

Print ATS specific 

data online and/or 

offline 

V 

( RETURN 

Figure 3-19. TWOUT Flow Chart (uontinuea) 
Yes 

TREAD (COTPP) 

Read the first COTPRIME 

record 

EW060 

ACQCP 

Determine the COTPRIME entry 

number corresponding to the 

current ASST entry 

EW060+9 

EXWGTSC 

Reorder the ASST according 

to ascending group number 

Is current item a primary? 

11,Yes 

Calculate primary score 

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-SigittILD 

EXWGTSC EXWGTSC 

Figure 3-19. TWOUT Flow Chart (Continued) 
Is next ASST entry on the same Yes 

group as the current one? 

Yes 

No 

V 

Were there any other 

targets in this group? 

Was group by group expected No 

score print selected?' 

No 

EW080 

Yes 

4 

411 

s this rev completed? 

RETURN 

EWO7O V 

Calculate VIT score 

\;) 

Print expected score for 

the current group 

PRNTEW 

Perform rev summary bookkeeping 

and group initialization 

EWO9O 

IIFYes 

PRNTEWSM 

Print rev summary 

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EXWGTSC EXWGTSC 

FIGURE 3-19. TWOUT Flow Chart (Continued) 

'ffe-REILD 
EXWGTSC EXWGT SC 

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BIF-4-B10009-68 

Page 338 

-SEC-RETID 

Yes 

EW120 

Reorder expected score table 

according to descending score 

EW130 

Calculate expected score for 

the group 

Figure 3-19. TWOUT Flow Chart (Continued) 

Is next ASST item a member No 

of a new group? .1D 

EW100 

Make active and inactive entries 

to expected score table 

EW110+14 
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Page 339 

3.13 TWPLOT1 

3.13.1 Purpose 

TWPLOT1 produces a time-obliquity swath plot of all targets on the 

acquisition tape. On option, the targets selected for main optics photography 

and ATS viewing are superimposed on the plot. 

3.13.2 Input 

The following inputs are required by TWPLOT1 

a. Acquisition tape (See Section 3.3.3) 

b. PATHDATA (see Section 3.12.3) 

c. THINGS (see Section 3.2.3) 

The table THINGS parameters that control TWPLOT1 output options are 

input through the File 8 parameters used by TWPLOT1 and located in table 

THINGS as depicted in Table 3-40. 

3.13.3 Output 

The output of TWPLOT1 is a time obliquity swath plot as shown in 

Table 3-41. 

A hierarchy of characters is employed to resolve conflicts in printing 

requirements. This hierarchy is shown in Table 3-42. The character having 

a lower rank will be printed if a conflict occurs. 

SEtRETiD 
BIF-4—B10009-68 ID 

Page 340 

ii 

0 

Definition 

co

ntrol in 

generate PLOT 

H 

0 

H 

H 

E-I 

CD 

44 

-S-EC-RET-tD 

Ta

ble 3-40. File 8 Parameters Used in TWPLOT1 Located in Table THINGS 

Res

et FileDefinition Interface Table Usage 

Definition 

Generate 

1: Generate 

selection plot 
Table 3-40. File 8 Parameters Used in TWPLOT1 Located in Ta

b le THINGS (Co

n

tinued) 

Definition 

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co 

cr, 

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JEGREI7D 

BIF-4—B10009-68 

Page 341 

Reset F

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- ca 

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o co 0 

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ga. 

a) 0 

a) 

Ca 0 

0 

1-1

W 

0-1 0

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3 

4-) 

c.) a) 

a) 

c—i a) H 

cn G O 

4.1 

a) co 

to 4.) 

(C1 

H P. 
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ble 3-41. Acq

uisition a

nd Targ

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ction Plot 

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0 

LL CN 

0 ›- 

W 

0 

X 

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0_ Ci) 

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O- Lj 

W 

Z 

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AAA a AA A AA A An 

.4 ./ 

BIF-4-B10009-68 ID 

Page 342 

N 

0 

N 

N 

v1•r0 N 

000140 

A 

N, 

N G 

CC 

O. 

0 

N 

vr.5,0 

NIP.O. 

.. 

,,, 

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.... 

I. 

P 

....6.4 

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... 

PP 

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N 

• 

• • 

• 

N N 

• 

• 

•■ •• . 

NN.W4"0 ,. NN,VP 

 ++++ 

• .04.007J . • 

:71N.VAC ,A A 

• n • 

30• .N.VA 

it • 

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NN.VAC 

• 

0 • • • • 

00 • 

...K. • 

. • 

• • • • 

C 

1-). • • • 

.0 • 

• 

v • 

..I • • • 0 

LIWW. . N .. .11 ...... Nn*A0,0ponN.M. A ...... N.,,A41,0po.N.WA ...... N.2.10 

vp..- 

W.NNNNNNNNAINMMNNNNNNNNN MNMNNNMNNNNNNNNNNN..P1...,.....Orq.*0 1 

A NNNVNINNNMNN N. .NNNNNNNNNNNNNNNNNLONNNNNNNNNNNNNJ 

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• 

• 

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0 

'.0 1/40 '.0 N. N. 

0 0 0 0 0 

/".`, /1 /1 /1 /1 /1 m ul n o rl 0 (,) 

0 0 0 0 0 0 0 0 0 

rx.1 w C2 x H h 1:4 1-1 z CN] + 

co 

4.) 

U 

O Cd 

Representation Table 3-42. Hierachy of Characters in TWPLO

T1 

Character 

Character 

C.; 

Ir e' O 

c) >- In —I 

> 

CL 1.1.1 0_ CO 

w 0 LLJ Z 

,SECIrin BIF-4—B10009-68 

Page 343 

/1 /1 /1 /1 /1 

o N. N Cc) 1/40 

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0 0 0 0 0 0 0 

co) 

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z -X ° 

1-4H 

cd 

0 

Cd 

Pr) CD o 0 Ce) 1.11 1/40 CO CT 0 H C+1 

C•4 N Cs1 CV Cs) C■I M cf, CA) 01 M M M c,) 

NI N. e1/41 t-1 C•I Ln 1/40 N. O r1 H CNI Ce) 

N. in cn H 0 0 0 0 0 0 0 H 1/40 1/40 1/40 1/40 

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

A 0 H N M d v1 1/40 N. 00 c0N al 0 A 

'.0 co C.% O H N 01 -4' ul '.0 CO CT 0 H CNI 

PG H H H H H H H H H H CNI N CNI 
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Page 344 

SEC.11U/D 

3.13.4 Method 

The flow charts for TWPLOT1 and the key procedures employed by this 

subfunction are provided in Figure 3-20. The key procedures are described 

in the following paragraphs. 

3.13.4.1 TPLOTS 

Generation of the swath plot is accomplished by the procedure TPLOTS. 

An image of two pages of the plot is maintained in core. This image is 

initially filled with blanks by the procedures PAGESET1 and PAGESET2. If 

the largest allowable plot obliquity is other than the nominal 45°, an appropriate scale change is then made. Two hundred entries are read into 

core from the acquisition tape. Acquisition entries are then examined 

until the first target in the rev span of interest is found. When a selection plot is requested, a target selected by the main optics target selection algorithm or the ATS target selection algorithm is flagged so that 

selection symbols may be affixed to the target. Forward, vertical, and aft 

acquisition times are converted to page row numbers and obliquity is converted to page column number. If the row number of the forward acquisition 

time indicates that a new page must be started, control is passed to 

PGEWRITE which produces the selection plot and writes the completed page on 

the list tape. Control is passed to TSTORE which plots the most significant digit of the target inactive priority in the vertical time row. The 

characters "+" and "-" are plotted in the forward and aft rows if requested. 

TSTORE also writes each target ID in the right hand margin of the page in 

the vertical acquisition row. 

The successive acquisition entries are then processed as described 

above until all targets in the rev span of interest have been processed. 

Control is then returned to TWONDER2. 

3.13.4.2 TSTORE 

The procedure TSTORE initially determines if the current target vertical acquisition row is the same as the last one. If not, a check is 

made to determine if the ID's of targets in the earlier row have been 

stored in the right margin of the page and stores them if not. If the 

number of targets in the last row is greater than 2, the three right most 
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Page 345 

characters of each ID are stored. If the number of targets exceeds the 

maximum number of 3 character fragments, which is seven, the number of targets is stored in the left hand margin overriding the system time print. 

The "+", the most significant digit of priority, and the "-" are stored in 

the appropriate column and rows by the procedure PLACE and control is returned to TPLOTS. If the current target vertical acquisition row is the 

same as the last one, PLACE stores the "+", the most significant digit of 

priority, and the "-". The target ID and obliquity are stored in a special 

ID buffer with the other target(s) in the same row; only the seven highest 

priority targets are retained if there are more than seven targets in the 

TOW. Control is then returned to TPLOTS. The procedure SYSTIME is used 

as necessary to store a running count of system time in the left hand margin. 

3.13.4.3 PGEWRITE 

If the selection plot is not desired, the acquisition plot is immediately written online and/or offline and control is returned to TPLOTS. 

If the selection plot is desired, each ATS selection is processed as folfows: the group decision time of each selection is indicated by overriding 

the system time in the left margin with the group number and printing a set 

of "*"'s across the plot page at five column intervals. PLACE is used to 

store the "*"'s and will not allow them to be stored if a more important 

character already occupies the intended space. Path number and a running 

count of the duration of the scope dwell time are stored in the appropriate 

obliquity column enclosed in parentheses. 

After all ATS selections for the page have been processed, the main 

optics selection is processed as follows: a running count for the forward 

photographic sequence is stored in the appropriate obliquity column followed by blanks representing the dead time and a running count for the aft 

photographic sequence. The entire sequence is enclosed in carets. 

After all main optics selections have been processed, the completed 

plot page is written online and/or offline and control is returned to 

TPLOTS. 
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Page 346 

--SEOREVD 

3.13.4.4 Utility Subroutines 

The following utility subroutines are used by TWPLOT1. 

PLACE A procedure which compares a character to be stored in 

the plot page image buffer with the character (including 

BLANK) already present according to the hierarchy of 

characters in TWPLOT1. The new character overrides the 

old one only if it is found to be more important in the 

hierarchy scheme. 

PAGESET1 A procedure which stores all blanks in the first page 

image buffer. PAGESET1 is used by TPLOTS. 

PAGESET2 A procedure which stores all blanks in the second page 

image buffer. PAGESET2 is used by TPLOTS and PGESHIFT. 

PAGEHDR A procedure which stores page headers to begin pages and 

stores page trailers to complete pages. PAGEHDR is used 

by TPLOTS. 

PGESHIFT A procedure which shifts the second page image buffer 

into the first one. PGESHIFT is used by TPLOTS. 

SYSTIME A procedure which stores system time in seconds modulo 

86,400 (one day) in the left hand margin of the plot 

page image buffer. SYSTIME is used by TPLOTS and TSTORE. 

TSHIFT A procedure which stores target ID and obliquity column 

in a buffer in order of obliquity. If the buffer is full 

(7 entries) the incoming entry will bump the entry of 

lowest rank from the buffer if the new entry is of 

higher rank. TSHIFT is used by TSTORE. 

FATR A procedure which converts forward, vertical and aft acquisition times from machine time to system time. FATR 

is used by TPLOTS. 

TIMR A procedure which converts forward, vertical and aft acquisition time (system) to page row numbers. TIMR also 

converts obliquity to page column number. TIMR is used 

by TPLOTS. 

TWTIMR A procedure which computes the duration of photographic 

sequences. TWTIMR also converts selection obliquities to 

column numbers. TWTIMR is used by PGEWRITE. 

TWFATR A procedure which computes the starting row of a photographic sequence from system start time. TWFATR is used 

by PGEWRITE. 
Perform general 

initialization 

TWPLOT1+10 V 

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Page 347 

TWPLOT1 TWPLOT1 

TWPLOT1 

(

Was TWPLOT1 called by 

TWONDER2? 

Yes 

No 

Acquire parameters from function 

card: Rev span, selection plot 

flag, online and offline print 

flags. 

Get parameters from "LOCPAR" 

parameter table for stand 

alone mode. 

TP17 

s selection PLOT being done? 

No 

Yes 

Read interface tape for selection PLOT 

information (fill table PATHDATA) 

TP20+3 

) 

Do requested PLOT procedure for 

appropriate revs 

V 

TPLOTS 

( RETURN ) 

Figure 3-20. TWPLOT1 Flow Chart 

-SEC-RE-I/ D 
TP16 V 

TP15 

Was TWPLOT1 called for 

ACQ plot only? 

) No (ACQ and SELECT) 

RETURN 

Set rev span to TWONDER 

function card rev span 

Turn off TWOUT predecessor 

flag 

Was selection PLOT requested? RETURN 

Yes 

Set rev span to _include current 

rev only. Set selection plot flag. 

Set online and offline print flags 

from File 8 

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TWPLOT1 TWPLOT1 

Figure 3-20. TWPLOT1 Flow Chart (Continued) 
TPLOTS 

PL10 

)

PAGESET1 and PAGESET2 

• 

Set page images to 

all blanks 

)

allowable obliquity No 

IrYes 

nominal (45°)? 

PL10+10 

Is largest 

other than 

Make appropriate scale change 

to reflect new maximum obliquity 

PL12 

• 

PL15+5 

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Page 349 

TPLOTS 

E4 ERROR Read header 

record on 

ACQ tape 

EOF 

Check to see if first five 

characters are the BCD word "BASIC" 

N 

• 

Print Message: 1st 5 characters 

of 1st record of ACQ tape not equal 

to "BASIC" press start to continue 

Yes 

Figure 3-20. TWPLOT1 Flow Chart (Continued) 

--SEDRERD 
Yes 

Is this a header entry or is 

the rev number less than the 

span of interest? 

(Process 200 ACQ entries) 

PL65+7 

For A=0,1,199$ 

TPLOTS TPLOTS 

IIMI•••■ asOINNIIIM •••••11.• MNIMMO limmenir daemon. 

BUMP A 

Yes 

STOP 

START PRESSED 

PL40 

ir 

(

Is this the last entry of 

the ACQ table? 

I 

I 

I 

I 

A 

I 

0 

Read information 

record or ACQ tape 

(

Is the rev number greater than Yes 

the span of interest? 

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Figure 3-20. TWPLOT1 Flow Chart (Continued) 
V PL105+14 

FINISAS+6 V 

TIMR 

Convert fwd, vert and aft machine 

,times to system times. Also convert 

obliquity to page column number 

FATR 

Convert fwd, vert and aft system 

times to page row numbers 

/\!Is it time to start a new page? 

PL110 

No 

Yes 

PL120+22 

TSTORE 

Store the current entry in the plot 

page buffer 

LTD A 

( Is selection plot desired? 

TPLOTS 

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TPLOTS 

1111.1=1111•1M1 .11•■■• ONVIIIMM• 

Figure 3-20. TWPLOT1 Flow Chart (Continued) 

PGEWRITE 

Add the MO and ATS selection symbols 

to the plot and write the page 

image buffer into the list tape 

PL65+21 

Yes 

V 

Flag items selected by MO and ATS 

so that selection symbols may be 

affixed to their printed ID's 
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TPLOTS TPLOTS 

PL13 

Print message: No items 

)

for rev XX on the ACQ tape 

Is this the first ACQ yes 

entry being processed? 

Was the last row of 

print completed? 

RETURN 

RETURN ) 

Figure 3-20. TWPLOT1 Flow Chart (Continued) 

PL45 

PGEWRITE 

Add the MO and ATS selection 

symbols to the PLOT and write 

the page image buffer onto 

the list tape 

Yes 

TSTORE 

Complete the last row of 

print in the plot page 

buffer 
PL15 

Print Message: Error reading ACQ 

tape in TPLOTS in TPLOT. Press start 

to try again. 

r - I._ --1 

L STOP .-- 1■1. oi 

START PRESSED 

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Page 353 

TPLOTS TPLOTS 

Figure 3-20. TWPLOT1 Flow Chart (Continued) 
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--SEGREWD 

TSTORE TSTORE 

TSTORE 

(

Is this the 1st acq entry 

to be processed? 

Yes 

No 

Is the current item in the 

same row as the last item? 

Yes 

No Perform row completion as 

shown below for the row 

which contains the last 

item 

(

Is the ID print buffer empty? 

(Initialized) 

Yes 

ST20 

Store ID's (or 3-character fragments 

if more than 2 ID's) from the ID print 

buffer into the ID field of the page 

buffer. In addition, override first 

character of each ID (or fragment) with 

appropriate selection character on ID's 

of selected items. 

(

Is the number of items in this 

row greater than the number allowed 

in the ID field? (7) 

Yes 

Print actual total number of 

items in system time field. 

(Overriding the system time) 

Q)- 

Figure 3-20. TWPLOT1 Flow Chart (Continued) 

--SECIET/D 
ST100 I 

Enter the current target into the 

ID print buffer. Since this 

follows the completion of a line 

of plot, this is the 1st entry for 

the next line (of at least 1-item) 

in the buffer 

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Page 355 

TSTORE TSOTRE 

Initialize (empty) the ID 

print buffer 

Is this the last row (with at 

(

Yes 

least one item) of the current 

page? 

RETURN 

No 

Is the obliquity of the current No 

( 

. 4vYes 

) 

Place appropriate character in 

margin (column 6 or 98) 

ST60 

Does system time print field need 

to be updated? 

Yes 

) 

Place system time in page buffer 

up to current plot line 

item outside obliquity limits? 

Place 

SYSTIME 

ST60+6 V 

Store "+", "TENS DIGIT OF PRI", 

and "-" characters in rows of fwd, 

vert, and aft system time, 

respectively, for the current item 

using the subroutine "PLACE". 

Also fill'in system time on the 

page as needed using the subroutine 

"SYSTIME". 

(: RETURN ) 

Figure 3-20. TWPLOT1 Flow Chart (Continued) 

'MEV D 
ST100+8 

Bump the counter for the number 

of items in the current row 

No 

ST100+11 V 

Store "+", "TENS DIGIT OF PRI", and 

"-" in rows of fwd, vert, and aft 

system time, respectively, for the 

current item using the subroutine 

"PLACE". Also fill in system time 

on the page as needed using the subroutine "SYSTIME". 

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'fft-REVD 

TSTORE TSTORE 

(

Is the obliquity of the current 

item outside obliquity limits? 

Yes 

(

Is the ID print buffer filled? 

(Contains 7 entries. Limited size 

of ID field imposes this restriction) 

No 

ST100+29 

Enter the current item into the ID 

buffer. The subroutine "TSHIFT" 

orders the ID buffer by obliquity. 

V 

( RETURN ) 

Yes 

Figure 3-20. TWPLOT1 Flow Chart (Continued) 
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Page 357 

TSTORE TSTORE 

ST210 

Determine the item of lowest priority 

in the ID buffer for potential deletion. 

V 

Yes Is the obliquity of the current item 

outside of obliquity limits? 

No 

ST400 

Enter the current target into the 

ID buffer only if it has a priority 

higher than the item of lowest 

priority in the buffer which must 

also be outside of obliquity limits 

ST225+10 

Enter the current item into the ID 

buffer only if (1) it has a higher 

priority than the item of lowest 

priority already in the buffer or (2) 

the item of lowest priority already in 

the buffer is outside of obliquity limits. 

The subroutine "TSHIFT" is used as above. 

V 

( RETURN 

Figure 3-20. TWPLOT1 Flow Chart (Continued) 
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Page 358 

IbEC—REILD 

PLACE PLACE 

PLACE 

K

Is the character to be 

inserted A "+" or "-"? 

Yes 

K

Was the "+" and "-" print option 

requested by File 8? 

Yes 

(

Is the space intended for 

insert blank? 

No 

PC20 

Determine the priorities of 

the character to be inserted 

and the character already present 

using the BCD character hierarchy 

No Is the priority of the character to 

 be inserted numerically less than 

the character already present? 

Yes 

PC30 

Replace the character already 

present with the character to 

be inserted 

No 

No 

•

ir 

Yes 

( RETURN 

Figure 3-20. TWPLOT1 Flow Chart (Continued) 
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Page 359 

PGEWRITE 

PGEWRITE 

PGEWRITE 

Is selection PLOT desired? 

Yes 

NEXTASST 

Has full ATS data table been Yes 

processed? 

No 

(

Have all ATS selections for 

the current rev been processed? 

ir No 

TWTIMR 

Calculate duration (number of rows) 

of ATS event given TON and TOFF. Also 

calculate appropriate column given 

obliquity. 

( Does this event start at a time not Yes 

No 

TWFATR 

Compute row number for 

ATS decision time 

( Does the decision time row number ) Yes 

Yes 

yet covered by the ACQ plot? 

exceed the page buffer? 

No 

Figure 3-20. TWPLOT1 Flow Chart (Continued) 
( Does ATS TON row number exceed the ) Yes 

page buffer? 

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'SEDREILD 

PGEWRITE PGEWRITE 

NEXTASST+17 

Fill decision time row 

(1) Insert asterisks across page 

using "PLACE". (2) Insert group 

number in system time field 

TWFATR 

Compute row number for ATS TON. 

TEST DELA+12 V 

Fill in ATS track in obliquity column 

Insert running count for duration of 

dwell time (in parentheses),Insert path 

number at start 

Bump ATS data table 

index 

Figure 3-20. TWPLOT1 Flow Chart (Continued) 
SECHALF I V 

Yes 

Yes V 

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Page 361 

PGEWRITE PGEWRITE 

( Has full MO data table been 

processed? 

NEXTMOST 

Have all MO selections for the 

current rev been processed? 

No 

NEXTMOST+5 

Calculate TON and TOFF of first 

half of MO event 

V 

Calculate TON and TOFF 

of second half of MO 

event 

TIMRCALL 

TWTIMR 

Calculate duration 

of 1st or 2nd half 

TON or TOFF. Also 

appropriate column 

(number of rows) 

MO event given 

calculate 

given obliquity 

Figure 3-20. TWPLOT1 Flow Chart (Continued) 
Does MO TON row number 

exceed the page buffer? ( Yes 

TESTDELM+18 V 

Fill in MO column 

Insert running count of 1st or 2nd 

half of MO event (in carets). 

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'SEfiREIVD 

PGEWRITE PGEWRITE 

(

Does the 2nd half of the MO event Yes 

start at a time not yet covered by 

the ACQ plot? 

N 

V 

) 

Compute row number 

for MO TON 

TWFATR 

P 

(

Has the 2nd half of this MO 

event been processed? 

Yes 

PG100 

01 

Write completed plot page 

 buffer online and/or 

offline as requested 

RETURN 

V 

Bump MO data table index 

vir 

Figure 3-20. TWPLOT1 Flow Chart (Continued) 
BIF-4-B10009-68 

Page 363 

REFERENCES 

1. "Users Manual for TWONDER (Revised),"DM 38-0071, 24 June 1968. 

2. "Study Results Report;'DM 36-0067, 1 December 1967. 

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