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NASA Technical Memorandum 101454

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Numerical Arc Segmentation Algorithm for a

Radio Conference - NASARC (Version 4. O)

User's Manual

Wayne A. Whyte, Jr., Ann O. Heyward, Denise S. Ponchak,

Rodney L. Spence, and John E. Zuzek

National Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio

October 6, 1988
•.qw-, _
Numerical Arc Segmentation Algorithm for a

Radio Conference- NASARC (Version 4.0)

User's Manual

Wayne A. Whyte, Jr., Ann O. Heyward, Denise S. Ponchak,

Rodney L. Spence, and John E. Zuzek

National Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio

October 6, 1988

PREFACE

The software package, Numerical Arc Segmentation Algorithm for a Radio Conference (NASARC), was

developed to provide a method of generating predetermined arc segments for use in the development of an

allotment planning procedure to be carried out at the 1988 World Administrative Radio Conference (WARC-88).

Through careful selection of the predetermined arc (PDA) for each administration, flexibility can be increased in

terms of choice of system technical characteristics and specific orbit location. The NASARC software determines

pairwise compatibility between all possible systems at discrete arc locations. NASARC then exhaustively

enumerates groups of administrations whose satellites can be closely located in orbit and finds the arc segment

over which each such compatible group exists. From the set of all possible compatible groupings, groups and

their associated arc segments are selected using a heuristic procedure such that a PDA is identified for each

administration.

The information contained in the NASARC (Version 4.0) Technical Manual (NASA TM-101453) and NASARC

i Version 4.0) User's Manual (NASA TM-101454) relates to the state of Numerical Arc Segmentation Algorithm

lbr a Radio Conference (NASARC) software development through November 1, 1988. The Technical Manual

describes the NASARC concept and the algorithms used to implement the concept. The User's Manual provides

information on computer system considerations, installation instructions, description of input files, and program

operation instructions. Significant revisions have been incorporated in the Version 4.0 software over prior

versions. These revisions have further enhanced the modeling capabilities of the NASARC procedure and provide

improved arrangements of predetermined arcs within the geostationary orbit. Array dimensions within the

software have been structured to fit within the currently available 12-megabyte memory capacity of the

International Frequency Registration Board (IFRB) computer facility. A piecewise approach to predetermined arc

generation in NASARC (Version 4.0) allows worldwide planning problem scenarios to be accommodated within

computer run time and memory constraints with enhanced likelihood and ease of solution.

PRECEDING PAGE BLANK NOT FIL,_.,_ED

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DA_ ,II IHTt.T|OIdAI_Y

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CONTENTS

Page

PREFACE .................................................................................. iii

1.0 INTRODUCTION ........................................................................ l

2.0 INSTALLATION OF THE NASARC SOFTWARE PACKAGE .................................. i

2. I System Considerations for NASARC Installation ............................................ l

2.1. l Language/Compiler Requirements ................................................... 1

2.1.2 Storage and Memory Requirements ................................................. 1

2.1.3 Tailoring NASARC to the Operating System ......................................... 2

2.2 Detailed Installation Instructions for the NASARC Software Package ........................... 2

2.2.1 Magnetic Tape Attributes .......................................................... 2

2.2.2 Creation of NASARC Program Modules ............................................. 3

2.2.3 Creation of Commands/Job Control Language Necessary to RUN NASARC Programs--

NASARC and INTRFACE Procedure .............................................. 10

2.3 Auxiliary File Requirements ........................................................... 13

2.3.1 Input Files ..................................................................... 14

2.3.1,1 Segments File ........................................................... 14

2.3,1.2 Requirements Data File ................................................... 15

2.3,1.3 Service Area File ........................................................ 15

2.3,1.4 Point Sets File .......................................................... 18

2.3.1.5 Aff'diated Sets File ....................................................... 20

2.3.1.6 Input Data File .......................................................... 20

2.3.1.7 Separation Matrix File ..................................................... 21

2.3.1.8 Ellipse File ............................................................. 21

2.3.2 Intermediate Files ............................................................... 22

2.3.2.1 Intermediate Segments File ................................................ 23

2.3.2.2 Groups File ............................................................ 23

2.3.2.3 Intermediate Allotted Groupings File ........................................ 23

2.3.2.4 Unallotted Groups File .................................................... 24

2.3.2.5 Intermediate Selection File ................................................ 24

2.3.2.6 Intermediate Improvement File ............................................. 25

2.3.3 Output Files ................................................................... 25

2.3.3.1 NASARC Report File .................................................... 26

2.3.3.2 Condensed Report File .................................................... 26

2.3.3.3 Predetermined Arc File ................................................... 26

2.3.3.4 Error Message File ....................................................... 27

3.0 USE OF NASARC SOFTWARE PACKAGE IN PLANNING EXERCISES ....................... 27

3. I Overview of NASARC Procedure and Program Structures .................................. 27

3. I.I NASINTRF Module ............................................................. 28

3.1.2 NASARCO Module .............................................................. 70

3.1.3 NASSEP Module ............................................................... 70

3.1.4 NASARC! Module .............................................................. 72

3.1.5 NASARC2 Module .............................................................. 75

3.1.6 NASARC3 Module .............................................................. 78

3.1.7 NASARC4 Module .............................................................. 80

3.2 Creation of NASARC (Version 4.0) Input Files ........................................... 82

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3.2.1 Segments File Data ............................................................. 83

3.2.2 Service Area Data .............................................................. 85

3.2.2.1 Global Data ............................................................. 85

3.2.2.1.1 Rain Attenuation Flag ............................................ 85

3.2.2.1.2 Minimum Half-Power Beamwidth of Satellite Antenna ................. 85

3.2.2.1.3 Constants for Allotted Arc Equations ............................... 86

3.2.2.1.4 Reference Noise Bandwidth ....................................... 86

3.2.2.1.5 Minimum Earth Station and Satellite Power .......................... 86

3.2.2.2 Service Area Data ....................................................... 86

3.2.2.3 Additional Service Area Data .............................................. 87

3.2.2.3.1 Set Affiliation Code Data ......................................... 87

3.2.2.3.2 Space Station and Earth Station Characteristic Data ................... 87

3.2.2.3.3 Uplink and Downlink Carrier to Noise Ratios ........................ 89

3.2.2.3.4 Aggregate Carrier to Interference Ratio ............................. 89

3.2.2.3.5 Uplink and Downlink Power Calculation Flags ....................... 90

3.2.2.3.6 Existing System Flag ............................................ 90

3.2.2.3.7 Link Calculation Flag ............................................ 90

3.2.3 Point Sets File Data ............................................................. 91

3.2.4 Affiliated Sets Data ............................................................. 91

3.2.5 Inputs to NASARC0 Program/Input Data File ....................................... 92

3.2.5. l Downlink Frequency ..................................................... 92

3.2.5.2 Uplink Frequency ........................................................ 92

3.2.5.3 Percent of Year Outage Due to Rain Attenuation .............................. 94

3.2.5.4 Maximum Rain Attenuation Limit .......................................... 94

3.2.6 Ellipse and Rain Attenuation Data ................................................. 96

3.3 Using the NASARC (Version 4.0) Software Package ....................................... 96

3.3.1 Invoking NASARC Programs ..................................................... 96

3.3.2 Error Messages and Their Meanings ............................................... 96

3.4 Interfacing the NASARC and ORBIT Programs .......................................... 101

REFERENCES ............................................................................. 102

APPENDIX--NASARC PROGRAM PARAMETERS ............................................. 102
1.0 INTRODUCTION

Thisvolumecontainsinformationontheinstallationandoperationof theNASARC(Version4.0)software

packageforthegenerationof predetermined arcsto aidinallotmentplanningprocedures.

Thefirstmajorsectionof thismanual presentsdetailedinstructionsfortheinstallationof theNASARC(Version

4.0)softwarepackage. Whilethespecificsof theinstallationprocessmayvaryfromsiteto siteduetodifferences

incomputerhardwareandoperatingsystems, a sufficientlydetailedprocedureisprovidedtoallowfor

straightforwardinstallation.

Thesecondmajorportionof thismanualprovidesfull informationontheuseof theNASARCpackagefor

planningexercises, includingdescriptionsof allrequiredinputfilesandtheirpreparation, directionsforexecution

of theNASARC(Version4.0)package, andguidelinesfor user-supplied technical parameter values.Information

isalsogivenontheuseof theNASARC(Version4.0)packageinconjunctionwiththesynthesispackage

ORBIT-II,whichwasdevelopedbytheKokusaiDenshinDenshinDenwaCo,Ltd.,Tokyo,Japan.

DetailedinformationontheconceptsandalgorithmscontainedintheNASARC(Version4.0)softwarepackage

maybefoundintheNASARC (Version 4.0) Technical Manual (NASA TM-101453).

2.0 INSTALLATION OF THE NASARC SOFTWARE PACKAGE

In this section, full instructions are given for the installation of the NASARC software package. Information is

given on the attributes of the magnetic tape that contains the NASARC package, creation of program modules

from source codes, construction of appropriate commands necessary to utilize the NASARC software, and

attributes of files needed for program input and output. Prior to this detailed information, a discussion of system

considerations for NASARC installation is given to aid the user in determining appropriate installation procedures

for his or her specific machine and operating system.

2.1 System Considerations for NASARC Installation

In the following sections, information is given on the language and storage requirements of the NASARC

software package.

2.1.1 Language/Compiler Requirements

The NASARC software package is written in the (ANSI standard) FORTRAN 77 computer language. An effort

has been made to ensure that no extensions of the language that are specific to a particular system or machine

have been introduced into the software package. Thus, the user should be able to compile the appropriate

NASARC source codes using an (ANSI standard) FORTRAN 77 compiler suitable for the user's system.

2.1.2 Storage and Memory Requirements

To aid the user in successfully installing and running the NASARC software package on his system, both file

storage requirements and run-time memory requirements are now given. The user should note that these

requirements concern the NASARC source code files and program modules only: storage requirements for

associated input and output files are discussed in section 2.3.

Source file storage requirements:

NASINTRF source code: 36.0 kilobytes

NASARC0 source code: 48.6 kilobytes

NASSEP source code: 155.45 kilobytes

NASARCI source code: 227.45 kilobytes
NASARC2 source code: 430.85 kilobytes

NASARC3 source code: 135.65 kilobytes

NASARC4 source code: 351.07 kilobytes

Object code storage requirements:

NASINTRF object code: 0.043280 megabyte

NASARC0 object code:

NASSEP object code:

NASARCI object code:

NASARC2 object code:

NASARC3 object code:

NASARC4 object code:

0.047440 megabyte

0.120560 megabyte

0.219520 megabyte

0.378240 megabyte

0.134720 megabyte

0.326960 megabyte

Run-time memory requirements:

NASINTRF module:

NASARC0 module:

NASARC 1 module:

NASARC2 module:

NASARC3 module:

NASARC4 module:

0.080880 megabyte

0.036488 megabyte

7.061416 megabytes

8.574322 megabytes

0.791528 megabyte

0.941972 megabyte

2.1.3 Tailoring NASARC to the Operating System

The NASARC software package was developed on an Amdahl 5860 running under the IBM VM operating

system. While example job control language is included in this manual, the user should note that commands

needed to load and run the NASARC modules and create and define files will depend on the user's operating

system. All such system commands are external to the NASARC programs; therefore, no modification to the

NASARC source code is necessary to adapt the package to any particular operating system.

2.2 Detailed Installation Instructions for the NASARC Software Package

In this section, detailed instructions are given for the installation of the NASARC software package. As was

mentioned in section 2.1.3, the specific procedure used to install the NASARC package differs for different

operating systems. However, the guidelines presented in the following sections are sufficiently detailed to allow

straightforward installation of the NASARC package.

2.2.1 Magnetic Tape Attributes

The NASARC software package is provided on a magnetic tape with the following attributes:

Number of tracks, 9 Number of files, 8

Density, 1600 bpi Logical record length, 80 bytes

Character set, EBCDIC Block size, 800

All files included on the tape should be unloaded; source code files should then be compiled to create the

appropriate program modules. The files included, and their attributes and purposes, are listed in table 2.2-1 in the

order in which they appear on the tape. The user is referred to sections 2.1.2 and 2.3 for information on file

storage requirements.
TABLE 2.2-l--FILES INCLUDED ON MAGNETIC TAPE

File name

NASINTRF

NASARC0

NASSEP

NASARCI

NASARC2

NASARC3

NASARC4

EXEC

Purpose

Fortran source code

Fortran source code

Fortran source code

Fortran source code

Fortran source code

Fortran source code

Fortran source code

NASARC procedure

(VM system)

Record length

80

Block size

800

I

2.2.2 Creation of NASARC Program Modules

After the files included on the magnetic tape have been unloaded and named according to the conventions of the

user's system, seven compiled modules must be created from the seven source files (NASINTRF, NASARC0,

NASSEP, NASARC1, NASARC2, NASARC3, and NASARC4) included on the tape. While conventions for

naming load modules differ from system to system, the modules should be named to correspond as closely as

possible to the designations NASINTRF, NASARC0, NASSEP, NASARCI, NASARC2, NASARC3, and

NASARC4 as this will aid the user in following the directions in the remainder of this manual.

Each module has a specific purpose within the software package as a whole. NASINTRF, the interface program,

creates three of the input files utilized by the remaining NASARC modules from the single data file defined by

the International Frequency Registration Board (IFRB) to contain required system parameters for all systems to be

considered in a plan. NASARC0, the input program, prompts the user for further input parameter values and

verifies as correct all inputs supplied via input files; an additional input file is created from the interactively

supplied user inputs, which will be utilized by the remaining NASARC modules. NASSEP, the satellite

separation program, calculates worst-case required orbital separations for all possible pairs of satellites. The

remaining NASARC modules (NASARC1, NASARC2, NASARC3, and NASARC4) are used iteratively in a

piecewise approach to the orbital arc defined by the user. NASARCI, the grouping program, enumerates a list of

compatible groupings of satellites and the arc segments over which each such grouping may exist. NASARC2.

the arc determination program, accepts the output of NASARC1 as input and selects appropriate groupings.

determines their allotted arc lengths, and arranges the arc segments in orbit. NASARC3, the group arc extension

program, examines compatible groupings of systems selected by NASARC2 in order to determine possible

extensions of their group arcs, should rearrangement of allotted arcs in orbit become necessary in examinalion of

subsequent pieces of the orbital arc. NASARC4, the arc interchange program, examines the most current

arrangement of allotted orbital arcs in order to determine if the arrangement may be improved through a heuristic

swapping procedure.

A more detailed explanation of the purposes of NASINTRF, NASARC0, NASSEP, NASARC1, NASARC2,

NASARC3, and NASARC4 may be found in the NASARC Technical Manual; storage and memory requirements

for each program module are addressed in section 2.1.2 of this manual.

Tables 2.2-2 through 2.2-8 contain complete listings of the names of the programs and subroutines that should

appear in each program module after compilation. The purpose of each subroutine is also briefly described. For

further insight on the structure of the NASARC modules, the user is referred to the flowcharts presented in

section 3.1.
TABLE 2.2-2.--PROGRAMS AND SUBROUTINES CONTAINED IN

NASINTRF MODULE AFTER COMPILATION

Program/subprogram name Purpose of program/sul_program

MAIN Construct Service Area file, Affiliated Sets Code

file, and Point Sets file from single requirements

data file utilized by WARC-ORB (2). Files will be

utilized by NASARC0, NASSEP, NASARCI,

NASARC2, NASARC3, and NASARC4 modules.

TABLE 2.2-3--PROGRAMS AND SUBROUTINES CONTAINED IN

NASARC0 MODULE AFTER COMPILATION

Program/subprogram name

MAIN

INTRST

Purpose of program/subprogram

Prompt user for interactive inputs; assemble

interactive inputs into input data file utilized

by NASARCI, NASARC2, NASARC3 and

NASARC4. Verify all externally created input files

consistent and correct.

Determine intersection endpoints of pair of arc

segments; used to verify that arcs of affiliated

service arcs intersect.

TABLE 2.2-4.--PROGRAMS AND SUBROUTINES CONTAINED IN

NASSEP MODULE AFTER COMPILATION

Program/subprogram name Purpose of program/subprogram

SEPAR

SETCON

RDPTS2

CREAT2

1NTRST

NEAR

BISECT

SCOFF

CICHK2

ESOFF

ANGLES

ERRS

Calculate worst-case orbital separations needed to

achieve target single-entry C/i value for all

possible pairs of satellite systems.

Set constant values for use throughout programs.

Read sets of polygon points for service areas from

Point Sets file.

Create arrays of ellipse data needed for separation

calculations.

Determine intersection endpoints of pair of arc

segments.

Determine two nearest endpoints of two service

arcs that do not intersect.

Perform bisecting search to determine new satellite

positions to be tested for achievement of target

single-entry C/ L

Calculate spacecraft antenna off-axis angle.

Verify that current orbital separation is sufficient

to achieve target C/L

Calculate antenna discrimination.

Calculate spacecraft antenna half-power beamwidth

in direction of interest.

Change initial error flag of Input Data file to Y if

error encountered.
TABLE2.2-5--PROGRAMS AND SUBROUTINES CONTAINED IN

NASARCI MODULE AFTER COMPILATION

Program/subprogram name Purpose of program/subprogram

MAIN Determine compatible groupings and arc segments

over which they may exist, in current portion of

orbit.

Set constants used throughout programs.

Determine intersection endpoints of pair of arc

segments.

Read sets of polygon points for service areas from

Point Sets file.

Change initial error flag of Input Data file to Y if

error encountered.

Read necessary ellipses from master Ellipse file

and store in array.

Verify that grouping criterion provides sufficient

orbital separation to achieve target C/I value,

Calculate spacecraft antenna off-axis angle.

Calculate earth station off-axis angle.

Calculate half-power beamwidth for satellite

antenna in direction of service area polygon point,

Calculate antenna discrimination.

Accumulate individual groupings, locations into list

of groupings and segments.

Form list of compatible groups, individual

locations into list of groups, arc segments.

Sort list in ascending order on two fields.

Primary field is compatible group taring; secondary

field is arc location at which group occurs.

Partition list of elements to be sorted.

Sort list of compatible groups, arc segments in

ascending order, by compatible group and western

group arc boundary.

Partition list of elements to be sorted.

Determine if group arc span crosses 180 ° east

longitude. (Entry within subroutine ACCUM.)

Output service areas, service arc longitudes,

individual buffer lengths, list of groupings, arc

segments,

SETCON

INTRST

RDPTS

ERR

CREATE

C1CHK

SCOFF

ESOFF

ANGLES

DISC

ACCUM

ARCSEG

QUICK l

PART I

QUICK2

PART2

CHKIS0

OUTLAST

TABLE 2.2-6--PROGRAMS AND SUBROUTINES CONTAINED IN

NASARC2 MODULE AFTER COMPILATION

Program/subprogram name

MAIN

INPARM

INSEGS

Purpose of program/subprogram

Select appropriate groups from NASARC I output;

determine allotted arc lengths in order to place all

administrations into geostationary orbital arc.

Read NASARC input parameters (C/1, downlink

frequency, antenna diameters, etc.) from Input

Data file.

Read Intermediate Segments file; determine bounds

of cumulative arc, bounds of current segment, and

direction of allotment buildup (E-W or W-E).
TABLE 2.2-6--Continued.

Program/subprogram name Purpose of program/subprogram

INGRPS Read service arc information relevant to present

LSTPAR

INALLT

INRMN

JOINER

PARTIT

CRTADM

MISSPI

LSTA LT

PRIOR

SEGCHK

OUTRMN

UPDATE

UNPACK

ITUARC

portion of orbit (service areas, service arc

longitudes, buffer arcs), along with groups, group

arcs generated over present portion of orbit from

current Groups file.

Echo NASARC input parameters in Intermediate

Selection file.

Read groups, allotted arc bounds, group arc

bounds selected in prior portions of orbit, from

Intermediate Allotted Groups file.

Read those groups that adjoin either edge of

current portion of arc, from Unallotted Groups

file.

Append unallotted groups list read by INRMN to

group list generated by NASARCI for current

portion of orbit; join group arcs of duplicate

groups where overlapping or contiguous.

Partition current service areas into 3 priority

classes according to service arc remaining outside

cumulative arc.

Determine information for each service area from

master group list, to find critical service area,

including number of service areas remaining in

groups list, remaining service areas, and frequency

of occurrence of each service area. Return service

area appearing in fewest number of groups, having

smallest service arc, as critical service area.

Check if Priority 1 service areas are missing

from master groups list.

Write current allotted arcs to Intermediate Selection

file, and to Intermediate Allotted Groups file, at

end of execution for present portion of orbit.

Evaluate service areas as priority 1 (PI), priority 2

(P2), or priority 3 (P3) for allotment.

Check if remaining arc in current portion of orbit

is sufficient to allot at least a 2 member group of

Priority 2 or Priority 3 service areas. If not, no

more arc allotments will be found and NASARC2

will stop.

Scan remaining groups in master list (after arc

determination process for present portion of orbit is

completed): identify groups whose group arc

adjoins one edge of the cumulative arc. Write

groups to Unallotted Groups file.

Update master groups list after arc allotted, by

deleting critical group members from groups in

list, joining group arcs of resultant duplicate

groups where overlapping or contiguous, and

I eliminatingduplicates where appropriate.

Convert group from packed format (no spaces

between service area codes) to unpacked format

(space separating service area codes in group) to

unprove readability when writing groups to files.

Import service area; export associated visible

service arc longitudes, arc length.

6
TABLE 2.2-6--Continued.

Program/subprogram name Purpose of program/subprogram

GRPBUF

PTACHK

ADDBOA

XTRACT

PULL

INDEX2

CHKI80

ADJSTI

COMBIN

QUICKI

PART 1

QUICK2

PART2

QU1CK3

PART3

QUICK4

PART4

QUICK5

Deternune group transitional arc by examining

service area transitional arcs of member service

areas, selecting largest.

Find prior temporary allotted arcs lying within,

overlapping desired potential temporary allotted

arc. For each of these, determine if contiguous arc

space is available within group arc to move allottec

arc to location allowing desired arc to be allotted.

Add group's temporary allotted arc to binary

orbital arc replica.

Extract critical group members from given group

in master list.

Places individual service areas from group into

separate elements of array.

Find starting column of 3-character service area

code within group character string.

Logical function subprogram; determines if given

arc span straddles 180" meridian.

Adjust two longitudes defining arc boundaries so

that westernmost edge is numerically less than

easternmost edge; both in range O* to 360*.

Used in subset arc extension, when forming critical

groups sublist.

Used in groups list updating process; employs

Quicksort algorithm (devised by CAR. Hoare).

Sort groups list alphabetically; for same group.

order group arcs west to east. For duplicate

groups with same west longitude, places group arc

extending furthest east first.

Partitioning module, used by QUICKI.

Used in forming the critical groups sublist;

employs Quicksort algorithm. Perform compound

sort on sublist; first, on number of members in

group (descending order); then on group arc length

(descending order); then group's total frequency

of occurrence (ascending order).

Partitioning module, used by QU1CK2.

Quicksort routine used in subset arc extension

process, when forming critical groups sublist.

Performs compound sort on sublist: first, on

number of members in group (ascending order):

then alphabetically (ascending order); then on

western longitude of group arc (ascending order).

Partitioning module, used by QUICK3.

Quicksort routine used in subset arc extension

process. Sorts group arcs in west to east order:

for segments with same west longitude, places

segment that extends furthest east first.

Partitioning module, used by QU1CK4.

Quicksort routine used in formation of critical

administration list. Sorts administrations in

ascending order, first on frequency of occurrence

of service area in master groups list, then on

visible service arc length.
TABLE 2.2-6--Concluded.

Program/subprogram name]

PART5

ISACHK

SUBLST

CRTGRP

XTEND

QUICK6

PART6

ALLOT

!GRPARC

NEIGH

MATRIX

QUlCK7

PART?

BINARY

MAXSEP

PDASEP

UPDAT2

PUSH

ARCCHK

FINSEP

QUICK8

PART8

Purpose of program/subprogram

Partitioning module, used by QUICKS.

Logical function to determine if sufficient service

arc remains open to allot service area as part of

criticalgroup.

Create sublist of groups from current master list,

containing critical service area. List is sorted in

assending order with respect to group size.

Determine critical group containing critical servic_

area from master groups list.

Extend group arcs which are subsets of other

groups, when forming critical groups suhlist.

Quickson routine used to sort allotments in west

to east order.

Pardoning routine used by QUICK6.

Find allotted arc for critical group within group

arc, changing previous allotted arcs if necessary.

Logical function indicating whether or not group's

i allotted arc is within group's group arc.

Determine, for given allotted arc, endpoints of

closest neighboring allotted arcs.

Read entries of satellite separation matrix

calculated by NASSEP.

Quicksort routine used to sort separation matrix

entries.

Partitioning routine used by QUICK7.

Performs binary search of list sorted in ascending

order.

Determine maximum orbital separation required

between two satellites or groups of satellites.

Determine required separation between two

allotted arcs.

Update master groups list after arc allotted by

deleting allotted group members from groups in

list, joining group arcs of resultant deuplicate

groups where overlapping or contiguous, and

eliminating duplicates where appropriate.

Allots arcs by moving prior allotted arcs. Relative

ordering of allotted arcs to east or west of current

location will not change.

Identify prior allotted arc intersecting specified

portion of orbital arc.

Determine final required separations between

allotted arcs.

Quicksort routine used in forming critical service

are,a list.

Partitioning routine used by QUICKS.
TABLE2.2-7--PROGRAMS AND SUBROUTINES CONTAINED IN

NASARC3 MODULE AFTER COMPILATION

Program/subprogram name Purpose of program/subprogram

MAIN

SETCON

INTRST

RDPTS

ERR

CICHK

SCOFF

ANGLES

ESOFF

DISC

Extend group arcs of cumulative set of groups

given allotted arcs by NASARC2 module, if

possible, within current portion of orbit.

Set constants used throughout programs.

Determine intersection endpoints of pair of arc

segments.

Read sets of polygon points for service areas from

Point Sets file.

Change initial error flag of Input Data file to Y if

error encountered.

Verify that grouping criterion provides sufficient

orbital separation to achieve target C/I value.

Calculate spacecraft antenna off-axis angle.

Calculate half-power beamwidth for satellite

antenna in direction of service area polygon point.

Calculate earth station antenna off-axis angle.

Calculate antenna discrimination.

Table 2.2-8.--PROGRAMS AND SUBROUTINES CONTAINED IN

NASARC4 MODULE AFTER COMPILATION

Program/subprogram name Purpose of program/subprogram

MAIN

INTRST

SWAP

FEASIN

REPORT

CNDREP

UNPACK

TEMPOR

ADDBOA

Improve most current arrangement of allotted arcs

through heuristic swapping procedure.

Determine intersection endpoints of pair of arc

segments.

Perform interchange of allotted arc segments after

determining that interchange is feasible and

improves arrangement.

Calculate matrix of feasible arc segment

interchanges.

Produce output report of NASARC results when

all portions of orbit within Segments file are

exhausted.

Produce condensed output report of NASARC

results.

Convert group from packed format (no spaces

between service area codes) to unpacked format

(space separating service area codes in group) to

improve readability when writing groups to files.

Attempt to clear further arc space, if necessary'.

between two allotted arc segments in final

tmproved arrangement.

Add group's temporary allotted arc Io binary

orbital arc replica.
TABLE 2.2-8--Concluded.

l_,ogram/subprogram name Purpose of progran__

PUSH

DENSE

PTACHK

PTRBUB

ARCCHK

IBUB!

PUSHI

PUSH2

ADJSTI

AFFINT

NEAR2

Move prior allotted arcs laterally. Relative

ordering of allotted arc segments will not change.

Determine whether arbitrary portion of arc is

occupied by prior allotted arc segments.

Find prior temporary allotted arcs lying within or

overlapping desired portion of orbit. For each arc

found, determine if contiguous arc space is

available within group arc to move allotted arc to

location allowing desired arc to be occupied by

incoming allotted arc.

Pointer bubble sort routine; sorts potential

temporary allotted arcs according to number of

intersections that each has with prior temporary

allotted arcs.

Identify prior allotted arcs intersecting specified

_ortion or orbital are.

Combination pointer and bubble sort routine.

Determine if two allotted arcs of different lengths

may be interchanged after lateral readjustment of

neighboring allotted arcs.

Attempt to clear sufficient arc space for given

allotted arc length.

Adjust two longitudes defining arc boundaries so

that westernmost edge is numerically less than

easternmost edge; both in range 0" to 360".

Determine service arc of affiliated set.

Determir, e two nearest endpoints of

nonintersecting service arcs.

2.2.3 Creation of Commands/Job Control Language Necessary to RUN NASARC Programs--NASARC

and INTRFACE Procedures

It was stated earlier that the specific set of system commands and/or job control language statements needed to

exercise the NASARC package program modules differ for different operating systems. Thus, the user must issue

the commands and/or job control language statements that are suitable for the system in use. While the specific

commands issued by the user depend on the user's system, the general list of functions that must be performed

by such commands is consistent for all systems. Many operating systems allow the user to create a single named

procedure that executes a sequence of system commands; it is suggested that such a procedure be created to

perform the following described operations.

To utilize the NASARC software package for allotment planning purposes, all seven of the NASARC modules

(NASINTRF, NASARC0, NASSEP, NASARC1, NASARC2, NASARC3, and NASARC4) must be executed in

the proper sequence. If multiple segments are being run, NASARC1, NASARC2, NASARC3, and NASARC4

must be executed consecutively in a repeated fashion for all segments specified by the user. (See fig. 2.2-1.)

The NASINTRF module is the first program module that must be executed, and it is executed only once. Its

purpose is to create the Service Area file, the Affiliated Sets file, and the Point Sets file for use by the remaining

NASARC modules. It reads from a file designed by the International Frequency Registration Board (IFRB) that

contains the required system parameters for all systems to be considered in a planning exercise. The

Requirements Data file contains parameter specifications and options that must be translated to specifications and

options compatible with NASARC; NASINTRF performs this function as well. If the user does not possess, or

10
The NASARC EXEC Procedure

t

FROt4/kNY_ U !

LO01C_ Ull'nl

ICdl_ 11.1E141¢n"

IIRO_AM

!!_ LOOP

Figure 2.2-1.

I!
wish to use, a Requirements Data file, it is possible to create Service Area, Affiliated Sets, and Point Set files

directly; in this ease, the NASINTRF module need not be used. Further details on direct creation of these files

are provided in section 2.3 herein.

To perform the functions described, the INTRFACE procedure to execute NASINTRF should contain appropriate

system commands and/or job control language to execute the following sequence of instructions:

(1) For BATCH processing only, set and define necessary job parameters.

_2) Define all FORTRAN logical units:

(a) Define FORTRAN logical unit 15 as the Service Area file, with appropriate file attributes.

(b) Define FORTRAN logical unit 25 as the Requirements file, with appropriate file attributes.

(c) Define FORTRAN logical unit 13 as the Affiliated Sets file, with appropriate file attributes.

(d) Define FORTRAN logical unit 14 as the Point Sets file, with appropriate file attributes.

(3) Load and execute the NASINTRF module.

(4} For BATCH processing only, submit job for processing.

Following execution of the INTRFACE procedure, the remaining NASARC modules may be run. The

NASARC0 module is the first program element that must be executed, and it is executed only once. Its purpose

ts to create the Input Data file from user prompted inputs for the remaining NASARC modules to use when

executing. It reads from the Service Area file, Point Sets file, Affiliated Sets file, and Segments file. It prompts

the user for the input parameters (date and time of run, comments describing the run, downlink and uplink

frequencies, annual percent outage due to rain attenuation, rain attenuation limit flag, and maximum rain

attenuation limit) and checks if they are within established limits. Also, an error checking procedure is performed

to determine if all files are structured correctly. When an error is discovered, an error flag is set to Y (yes).

This flag is read by all subsequent program elements through the Input Data file and if it is set to Y, it causes

them to immediately STOP executing--thus preventing unnecessary erroneous runs.

The NASSEP program reads all files generated by the NASINTRF and NASARC0 programs, and the master

Ellipse file. NASSEP produces a file that is utilized by both the NASARC2 and NASARC4 modules-the

Satellite Separations file. The NASSEP program needs to be executed only once for a given set of data contained

in the Service Area file, the Affiliated Sets file, and the Point Sets file, and it generates a file that contains the

worst-case separations for all possible pairs of satellites.

The NASARCI program reads all of the files read by the NASARC0 program and, in addition, the Input Data

file. the master Ellipse file, and the Intermediate Allotted Groupings file. NASARCI produces two files that are

used by NASARC2--the Groups file and the Intermediate Segments file. Also, the Segments file is modified for

subsequent runs of the NASARCI module.

The NASARC2 program reads from the Input Data file, the Intermediate Allotted Groupings file, the Unallotted

Groups file, and the two files created by NASARCI. Its updated result, after each segment is executed, is stored

in the Intermediate Allotted Groups file. NASARC2 also generates an Intermediate Selection file which provides

information on the selection of the allotted groups.

The NASARC3 program performs the group arc extension function. For this, it reads the Service Area file,

master Ellipse file, Point Sets file, Affiliated Sets file, Input Data file, and Intermediate Allotted Groupings file.

After execution, its results are stored in a modified Intermediate Allotted Groupings file. NASARC3 extends the

group arcs of allotted groupings as far as possible across the orbital arc.

The NASARC4 program serves two purposes. Up to and including execution during the last segment specified in

the Segments file, NASARC4 attempts to rearrange the most current arrangement of allotted arcs via a heuristic

swapping procedure designed to improve compatibility between neighboring allotted arcs. The resulting new

arrangement is stored in the Intermediate Allotted Groupings file. When executing during the last segment,

NASARC4 also restores the original Segments file and produces the NASARC Report file, Condensed Report

file. and Predetermined Arc file.

1_ TM
To perform the tasks described, the NASARC procedure should contain appropriate system commands andor job

control language to execute the following sequence of instructions in the following order presented (see also fig.

2.2-1):

(I) For BATCH processing only, set and define necessary job parameters.

(2) Erase intermediate files from any previous run:

Intermediate Allotted Groupings file.

Intermediate Segments file.

Unallotted Groups file.

Groups file.

Error Message file.

Intermediate Selection file.

Intermediate Improvement file.

(3) FORTRAN logical units:

(a) Erase

(b) Erase

(c) Erase

(d) Erase

(e) Erase

(f) Erase

(g) Erase

Define all

(a) Define FORTRAN logical

(b) Define FORTRAN logical

(c) Define FORTRAN logical

(d) Define FORTRAN logical unit 13

(e) Define FORTRAN logical unit 14

(f) Define FORTRAN logical unit 15

(g) Define FORTRAN logical unit 16

(h) Define FORTRAN logical unit 17

(i) Define FORTRAN logical unit 18

(j) Define FORTRAN logical unit 19

(k) Define FORTRAN logical unit 20

(!) Define FORTRAN logical unit 21

file attributes.

(m) Define FORTRAN logical unit 22

(n) Define FORTRAN logical unit 23

(o) Define FORTRAN logical unit 24

(p) Define FORTRAN logical unit 25

(q) Define FORTRAN logical unit 27

(r) Define FORTRAN logical unit 28

(s) Define FORTRAN logical unit 29

unit 10 as the terminal (output unit for interactive queries to user).

unit 11 as the terminal (input unit for interactive queries to user).

unit 12 as the Input Data file, with appropriate file attributes.

as the Service Area file, with appropriate file attributes.

as the Affiliated Sets file, with appropriate file attributes.

as the Point Sets file, with appropriate file attributes.

as the Segments file, with appropriate file attributes.

as the Intermediate Segments file, with appropriate file attributes.

as the Ellipse file, with appropriate file attributes.

as the Error Message file, with appropriate file attributes.

as the Groups file, with appropriate file attributes.

as the Intermediate Allotted Groupings file, with appropriate

as the Unallotted Groups file, with appropriate file attributes.

as the Intermediate Selection file, with appropriate file attributes.

as the NASARC Report file, with appropriate file attributes.

as the Predetermined Arc file, with appropriate file attributes.

as the Satellite Separations file, with appropriate file attributes.

as the Intermediate Improvement file, with appropriate file attributes.

as the Condensed Report file, with appropriate file attributes.

(4) Load and execute the NASARC0 module.

(5) Load and execute the NASSEP module.

(6) Determine the number of segments to be run (N).

(7) Load and execute the NASARCI module.")

/

(8) Load and execute the NASARC2 module.(

/

(9) Load and execute the NASARC3 module._

/

(10) Load and execute the NASARC4 module..,,]

(11)

Loop through instructions (7), (8), (9), and (10) N times.

For BATCH processing only, submit job for processing.

If the user's system is unable to perform the loop indicated previously, steps (7) and (10) must be repeated as

many times as there are segments to be run.

2.3 Auxiliary File Requirements

The NASARC software package requires several auxiliary files for program input and output. Auxiliary files

needed fall into one of three categories: input files, which are generally prepared prior to repeated execution of

the NASARC1, NASARC2, NASARC3, and NASARC4 modules; intermediate files, which are generated by

13
NASARCprogramsfortemporary use; and output files, which are produced at the end of use of the NASARC

package. The contents, formats, and approximate storage requirements (where possible) of each file are described

in the following sections.

2.3.1 Input Files

In general, input files are those required for use by one or more of the NASINTRF, NASARC0, NASSEP,

NASARCI, NASARC2, NASARC3, or NASARC4 modules. In most circumstances (discussed in section

2.3.1.5), these files are generated by utilizing the NASARC modules, although the required files may also be

constructed independently. The files must adhere to the file structure, format, and content described in the

appropriate section.

2.3.1.1 Segments File

The NASARC (Version 4.0) software package is based on an approach to developing predetermined orbital arcs

that differs in a significant respect from the approach utilized in prior versions of the software. NASARC

(Version 4.0) applies the general concepts and calculations utilized by earlier versions of the software in a

piecewise approach to the orbital arc as a whole; that is, a segment of the orbital arc is examined for compatible

groups of service areas, and the arc spans over which such groups may exist are found. These group arcs lie

within the portion of the arc currently being examined. From the list of groups and group arcs, groups are

selected and predetermined arcs are found for the selected groups. These arcs also lie in the portion of the arc

currently being examined. The process is be repeated for subsequent segments of the arc.

The Segments file contains the portions of arc that are to be sequentially examined and the grouping criteria to be

applied for each segment. Each segment is listed by its western and eastern limiting longitude; each record of the

file contains one segment. Up to 40 such records may be included in the file; the segments may span the entire

360* of available orbital arc, which is regarded by NASARC Version 2.0 as ranging from - 179" east longitude

to 180" east longitude. If a portion of the orbit under consideration crosses the 180" meridian, the western edge

of the arc segment may have a positive longitude, while the eastern edge has a negative longitude. Each segment

has associated with it a grouping criterion, expressed in degrees, which defines the maximum allowable orbital

separation required between two satellites that will allow them to be considered compatible and eligible for

grouping.

The density of systems that may share portions of the orbital arc varies across the geostationary orbit. Thus, a

particular segment of the orbit to be analyzed may contain locations that are visible to many more service areas

than locations in other segments. For this reason, the user may wish to vary the grouping criterion-an upper

limit on the orbital separation that may be required between two systems in order for them to be considered

compatible-for each segment of the orbit to be processed. A higher value would be suitable for a less dense

portion of the orbit; a lower value would serve to reduce the number of groupings generated in a higher density

portion of the orbit.

The portions of orbital arc listed within the Segments file must be disjoint; that is, no two segments of the orbit

that are listed in the file should encompass arc locations that overlap. Two portions of arc whose western and

eastern boundaries (respectively) are separated by 1" of orbital arc are considered to be adjoining portions of the

arc. After the first portion of the arc listed within the segment file, each subsequent segment must adjoin either

the eastern or western arc boundary of one of the prior segments.

The specific format in which each record must be constructed is (IX, F7.2, IX, F7.2, IX, F7.3), and can be

illustrated as follows:

± X X X . X X ± X X X X X X X X X X X

Colunm no.: I 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

14
Columns 2 through 8 of each record should contain the western boundary of each portion of the orbit to be

considered, expressed in degrees east longitude in the range -179.00 to 180.00. Similarly, columns 10 through

16 should contain the eastern boundary of each segment to be considered in the range - 179.00 to 180.00.

Colunms 18 through 24 contain the grouping criterion, which may range from 0.0 to 1.0.

As each record in the file is of fixed, 80-byte length, and up to 40 such records may be included in the file, the

Segments file may occupy up to 3.2 kilobytes of memory.

2.3.1.2 Requirements Data File

The Requirements Data file was created by the International Frequency Registration Board to contain system

requirements data submitted by administrations for allotment planning of the Fixed Satellite Service at the 1988

World Administrative Radio Conference. An interface module (NASINTRF) was created for the NASARC

(Version 4.0) software package that utilizes the Requirements Data file to create the Service Area file, the

Affiliated Sets file, and the Point Sets file by translating data, codes, and options utilized in other IFRB planning

software to formats and options required by the NASARC software. Because this file is not an integral part of

the NASARC software package, and is of limited application, no further details will be provided in this part of

the NASARC software package, and is of limited application, no further details will be provided in this User's

Manual. The user is advised to create his own Service Area, Affiliated Sets, and Point Sets files to suit his own

application of the NASARC software. Details on creation of these files are presented in subsequent sections.

2.3.1.3 Service Area File

The Service Area file may either be generated automatically from the Requirements Data file, via use of the

NASINTRF (interface) module, or it may be constructed via an editor by the user. The user is reminded that,

should he choose to construct his own file, the format and type of data presented in this section must be strictly

adhered to.

The Service Area file is a particularly important file in several respects. First and foremost, this file is a

complete listing of all service areas to be considered as candidates for an allotted arc. However, the file also

contains information specific to each service area that influences outcomes and decision processes throughout each

of the four NASARC program modules.

The first record of the Service Area file is a unique record. It contains information (in nine items) that is to be

applied globally to the entire scenario. The first item is the rain attenuation flag, a single character code that

specifies whether or not rain attenuation is to be taken into account in subsequent calculations. This is followed

by the minimum half-power beamwidth, expressed in degrees, which provides the smallest realistic elliptical

satellite antenna beamwidth to be considered in processing the scenario. The third, fourth, fifth, and sixth items

are constants utilized in calculating the allotted are length that is required by a particular group of systems. The

seventh item is a reference noise bandwidth, expressed in megahertz (MHz). This value is followed by the

minimum Ix_wer level for the earth station, ecpressed in dBW, and, finally, the minimum power level for the

satellite, also expressed in dBW.

Each subsequent record of the Service Area file may contain up to twenth-three items. The first item of each

rccord is a three-character service area code representing an administration or service area. These codes are

generally taken from the country symbols appearing in the International Frequency List. This item must be

followed, in each record, by the western and eastern longitudinal limits of the service area's service arc,

corresponding to a given elevation angle. As for the Segments file (see section 2.3.1.1) longitudes range from

-179" east longitude to 180" east longitude; if a service arc crosses the 180" meridian, its western service arc

boundary is positive while the eastern arc boundary is negative.

The fourth item in each Service Area file record is an integer numeric code used to identify a single service area

as a member of an affiliated set of service areas. Briefly, the concept of an affiliated set of service areas allows

15
the user to consider situations in which several service areas are to be served from a single orbital location--for

example, a nation with widely dispersed territories. By identifying each such service with the same integer

numeric code, the user signifies to the NASARC program modules that, in any compatible grouping found, either

all or none of the member service areas must be included. The concept of an affiliated set of service areas is

discussed in greater detail in the NASARC ( Version 4.0) Technical Manual.

The fifth, sixth, seventh, and eighth items in each Service Area file record relate to the individual specification of

space station characteristics. The fifth item is a six-character code identifying a choice of space station antenna

patterns to be utilized for the particular service area in question. The user must select such a pattern for each

service area. For further information on the choice of patterns available, the user is referred to section 3. I. 1.2.4

of the NASARC ( Version 4.0) Technical Manual and to section 3.2.2.3.2 herein.

The sixth, seventh, and eighth items in each Service Area file record also relate to space station characteristics

for the individual service area. These items are the space station antenna parameter value, the space station

antenna efficiency, and the spacecraft receiver noise temperature. The space station antenna parameter value must

be specified relative to the choice of the space station antenna pattern selected. The needed space station

parameter value may represent different quantities such as a sidelobe level expressed in decibels, or an antenna

decay constant expressed as a real number, depending on the choice of pattern selected. A value for the seventh

option, antenna efficiency, allows the user to specify a space station antenna efficiency that corresponds to the

specific antenna choice and parameter value already specified in the record. The antenna efficiency is expressed

as a decimal percentage (e.g., 55% = 0.55). The eighth option, spacecraft receiver noise temperature, is specified

in decibels converted from degrees Kelvin (dB-K). The ninth item is the spacecraft power, expressed in decibels

converted from watts (dBW). A more detailed discussion of space station antenna parameters is presented in the

NASARC ( Version 4.0) Technical Manual and in section 3.2.2.3.2 herein.

The tenth and eleventh items relate to the earth station transmit antenna. The tenth item specifies the antenna

pattern code for the earth station transmit antenna; the eleventh item is an associated parameter value. Items

twelve and thirteen are identical in meaning, but relate to the earth station receive antenna. Item fourteen is the

earth station antenna efficiency; the same value will be applied to both transmit and receive antennas. Item fifteen

is the earth station noise temperature, expressed in dB converted from degrees Kelvin. Item sixteen is the earth

station power level, expressed in dBW. Further details of earth station parameters are presented in the NASARC

( Version 4.0) Technical Manual, and in section 3.2.2.5 herein.

The seven remaining items specified for each service area determine how the service area's system will be treated

in the C/I calculations performed by the NASARC modules.

Items seventeen and eighteen are the carrier-to-noise ratios (C/N's) to be achieved on the uplink and downlink,

respectively, expressed in dB. These values are utilized if spacecraft and earth station powers are to be calculated

as those necessary to achieve a given C/N rather than those values directly supplied by the user.

Item nineteen is the target single-entry, total-link C/I to be achieved for the service area's system, expressed in

dB.

Items twenty and twenty-one also refer to the uplink and downlink, respectively, for the service area's system.

These items are single character option codes, specifying the manner in which uplink power and downlink power

are to be included in calculations. As stated previously, power values may be calculated from supplied C/N's or

they may be directly supplied as inputs.

Item twenty-two is also a single character code; it specifies, for the purposes of allotment planning at the 1988

World Administrative Radio Conference (WARC), whether or not the service area's system is to be considered

an existing system. This option impacts compatibility assessment between service areas.

The twenty-third, and final, item for each service area is also a single character flag. This flag specifies whether

the system of the service area in question is to be considered as uplink only, downlink only, or an uplink/downlink

system. This option also answers a specific need arising in allotment planning at the 1988 WARC.

16
Furtherdetailsandexplanationsof these options may be found in the NASARC (Version 4.0) Technical Manual.

The Service Area file must be constructed in a manner which maintains order compatibility with the Ellipse file

(see section 3.2.6 herein). Such ordering must be performed by the user as the NASARC modules do not

permute the order of the input records; the records are stored and processed in the order in which they are read.

The specific format in which Service Area file records must be constructed is presented in table 2.3-1.

As each record in the file is of fixed 150-byte length and up to 301 such records may be included in the file, the

Service Area file may occupy up to 45 kilobytes of memory.

TABLE 2.3-I--FORMAT OF SERVICE AREA FILE

(a) First record

Item Column Description Format Item Column Description

I 2 Rain attenuation AI 6 43 to 52 Allotted arc length

flag equation constant. C4

2 3 to 12 Minimum half-power FI0.0 7 53 to 62 Reference noise

beamwidth, deg bandwidth, MHz

3 13 to 22 Allotted arc equation F10.0 8 63 to 72 Minimum earth

constant, CI station power, dBW

4 23 to 32 Allotted arc length FI0.0 9 73 to 82 Minimum satellite

equation constant, C3 power, dBW

5 33 to 42 Allotted arc length FI0.0

equation constant, C3

Format

FlO.O

FIO.O

FlO.O

FI0.0

Item

I

2

3

4

5

6

7

8

9

13

II

12

(b) Subsequent records

Column Description Formal Item Column

I to 3 Three-character A3 13 88 to 95

service area code

4 to I I Western service arc F8.2 14 96 to 103

boundary, deg

east longitude

Eastern service arc F8.2 15 104 to 11

boundary, deg

east longitude

Numeric code for 13 16 112 to 119 1

set affiliation

Spacecraft antenna A6 17 119 to 126

pattern code

Spacecraft antenna F8.3 18 127 to 134

9arameter value

Spacecraft antenna F8.3 19 135 to 142

efficiency

Spacecraft noise F8.3 20 144

temperature, dB

Spacecraft power, F8.3 21 144

dBW

Earth station transmit A6 22 146

antenna pattern code

Earth station transmit 23 150

antenna parameter

Earth station receive

antenna pattern code

12 to 19

20 to 22

24 to 29

30 to 37

38 to 45

46 to 53

54 to 61

63 to 70

7 to 78

80 to 87

Description

Earth station receive

antenna parameter

Earth station antenna

efficiency

Earth station noise

temperature, dB

Earth station power,

dBW

Uplink C/N, dB

Downlink C/N. dB

Target single-entry carrierto-interference ratio

Power calculation

option, uplink

Power calculation

option, downlink

Existing system flag

Uplink/downlink/both flag

Forma

F8+3

F83

F8,3

F8.3

F8.3

F8.3

F8.3

AI

AI

AI

AI

17
2.3.1.4 Point Sets File

The Point Sets file may either be generated automatically from the Requirements Data file, via use of the

NASINTRF (interface) module, or it may be constructed via an editor by the user. Should the user construct the

file, the format described in this section must be followed.

The Point Sets file is utilized by the NASARC0, NASARCI, and NASARC3 modules to perform link

calculations for assessing interference between systems. As its name suggests, the Point Sets file contains sets of

polygon points defining boundaries of service areas. The general structure of the Point Sets file is illustrated in

figure 2.3- I.

The point set data contained in the Point Sets file include a set of polygon points, expressed as latitude-longitude

pairs, for each of up to 300 service areas. Polygon points are those which define the boundaries of the service

area or administration and are selected so as to form a convex polygon on the surface of the Earth. For

NASARC (Version 4.0) up to 10 such points may be specified for each service area. The user will save a

considerable amount of time in file editing and construction by employing a master Point Sets file that includes

point set data for all administrations and service areas rather than constructing an individual Point Set file for

each scenario. Polygon point sets may be added to the Points Sets file for new service areas, such as subregional

coverages which may be identified. The data contained in the Point Sets file must conform to a specific format.

The format is described in table 2.3-2.

Each set of points corresponding to an individual service area contains an initial descriptive record. In this record

are the three-character service area code, the number of polygon points for the service area, and the

corresponding eight-character beam code found in the Requirements file. This initial descriptive record is

followed by a series of records containing the polygon points themselves. The number of such records utilized

for the service area depends on the total number of points specified in the initial record; up to five points are

listed on each record following the initial record. Each of these records contains a series of five sets of columns,

each set containing the point latitude and point longitude.

The Point Sets file may occupy up to 90 kilobytes of memory, depending on the number of service areas

included in the file and the number of points supplied for each service area.

TABLE 2.3-2--FORMAT FOR POINT SET DATA FOR INDIVIDUAL SERVICE AREA

!Item[Column [ Description I Formal

Initial record

1 1 to 3 Three-character service area code A3

2 9 to 10 Number of points for service area 12

3 16 to 23 Requirements file eight-character A8

beam code

Subsequent records (2)

I 1 to 10 Point latitude (north, + ; south, - )

2 I 1 to 20 Point longitude (east, +; west, -)

3 21 to 30 See item 1

4 31 to 40 See item 2

5 41 to 50 See item I

6 51 to 60 See item 2

7 61 to 70 See item 1

8 71 to 80 See item2

9 81 to 90 See item I

10 91 to 1130 See item 2

FI0.0

FI0.0

18
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19
2.3.1.5 Affiliated Sets File

Like the Service Area and Point Sets files, the Affiliated Sets file may be generated from requirements data via

the interface module, or it may be constructed by the user.

In section 2.3.1.3, which describes the Service Area file, reference was made to an optional entry for each

service area that allows the user to indicate that a service area is a member of an affiliated set of service areas

that are to be served from a single space station location. In the Service Area file, membership in such a set was

signified by placing the same integer numeric code in the appropriate service area records. The result of

specifying such membership in an affiliated set was stated to be that all such service areas would be treated in an

all or nothing manner in the determination of compatible groups of service areas and the generation of allotted

arcs: that is, either all affiliated member service areas must be included in a compatible group of service areas or

no members must be included.

The purpose of the Affiliated Sets file is to aid in implementing the all or nothing treatment of member service

areas. Each record of the Affiliated Sets file contains an integer numeric code, corresponding to the code

specified on the records of the member service areas within the Service Area file. The integer codes should be in

ascending numeric order starting with one (1) and proceeding through to the number of separate affiliated sets

(i.e., 1. 2. 3. etc.). This integer code is followed by a three character code, for the affiliated set of service areas,

that will replace individual service area codes within a compatible grouping. The final item in each record is an

integer, equal to the number of individual service areas that are to be included as members in the affiliated set.

The format of each record is described in table 2.3-3.

The Affiliated Sets file may contain up to 25 such records. As each record is of fixed 80-byte length, the

Affiliated Sets file may occupy up to 2 kilobytes of memory.

The user is referred to the NASARC ( Version 4.0) Technicla Manual for further discussion of the affiliated set

concept, and to section 3.2.4 herein for further directions on use of the concept in construction of NASARC

(Version 4.0) input data.

TABLE 2.3-3--FORMAT FOR DATA IN AFFILIATED SETS FILE

Item Column

1 2to3

2 5 to 7

3 9 to 10

Description

Numeric code for

affiliated set

(=1,2,3 .... )

Three-character code

for affiliated set

Number of member

service areas in set

(=2 or more)

Format

!

12

A3

12

.... 1.6 Input Data File

The input Data file is created via execution of the NASARC0 module. The Input Data file contains a series of

records created primarily, though not exclusively, in response to the user's interactively supplied answers to a

series of input prompts issued by the NASARC0 module. In addition to these records, the Input Data file

contains several flags indicating various conditions of the input to the NASARCI, NASARC2, NASARC3, and

NASARC4 modules. These flags are the product of file checking and correlation operations performed by the

NASARC0 module and are thus only indirectly influenced by the user's input. Finally, the Input Data file

contains the four constants used in calculating the length of the allotted arcs to be given to service areas; as

mentioned previously, these constants are extracted from the Service Area file.

Further information on correct responses to the interactive prompts mentioned previously may be found in section

3.2.5 herein along with further details on the remainder of the Input Data file.
The Input Data file contains 18 records of fixed 80-byte length and thus occupies 1.44 kilobytes of memory.

2.3.1.7 Separation Matrix File

The Separation Matrix file, required by the NASARC2 and NASARC4 modules as input, is created by using the

NASSEP (the satellite separations program) module. The Separation Matrix file contains required orbital

separations for all possible pairs of satellites for a given scenario, in degrees, and represents a symmetric matrix.

Thus, the separations presented in the file are structured to reduce the storage space required: separations are

listed in the file for the first service area paired with the second and all subsequent areas, followed by the

separation required for the second service area paired with the third and all subsequent areas, and so on.

Further details of the method by which the separations are calculated may be found in the NASARC ( Version

4.0) Technical Manual and in section 3.1.3 of this User's Manual.

The specific format of each record of the separation matrix file is (IX, A3, 2X, A3, 2X, F7.2) and may be

illustrated as follows:

AA A B B B X X X X X X

Column: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

The separation matrix file may contain up to approximately 45,000 records of 20 bytes each; therefore, it may

occupy up to 0.9 megabyte of memory.

2.3.1.8 Ellipse File

The Ellipse file, an input to the NASSEP, NASARCI, and NASARC3 modules, contains ellipse and rain

attenuation data for service areas. For each service area, the Ellipse file contains ellipses at all possible integral

locations within the service area's visible arc (0" elevation angle) plus uplink and downlink rain attenuation data

tbr t_o sets of frequencies for all test points for the service area.

Each ellipse contained in the ellipse file is actually represented by three records. The first record describes the

ellipse beam parameters for a particular service area at a particular satellite longitude. The second record contains

rain attenuation data for one set of uplink and downlink frequencies for each test point defining the service area.

The third record contains rain attenuation data for a second set of uplink and downlink frequencies for each test

point defining the service area. The two sets of frequencies expected by the NASARC programs are currently

those expansion band frequencies subject to allotment planning at the 1988 World Administrative Radio

Conference. Should the user wish to use other frequency bands, some minor modifications to the NASARC

programs may be necessary. Rain attenuation data are presented at each longitude represented in the file because

attenuation varies with the variations in path length for each test point produced by a change in satellite

longitude.

Each set of three records that corresponds to a given service area and satellite longitude is composed according to

thc format presented in table 2.3-4. The first of the three records contains ellipse beam parameters: an eight

character beam code corresponding to a service area, the satellite longitude for which the ellipse and rain

_tttcnuation data were calculated, the longitude and latitude of the elliptical beam aimpoint, the major and minor

axes of the ellipse, and the ellipse orientation angle. The second and third records are identical in content: as

stated previously, they correspond to two sets of uplink and downlink frequencies and contain rain attenuations

(in dB) for each of up to 10 service area test points. In each such record the series of downlink attenuations for

all test points is followed by the series of uplink attenuations for all test points.

The sets of records in the Ellipse file must conform to a specific ordering. Sets of records are arranged in blocks

corresponding to service areas; sets of ellipse records for a given service area must all appear consecutively in

21
the same block of data. Within a block of records corresponding to a given service area, the sets of records should

be arranged by the longitude for which they were calculated in a west-to-east direction over the service area's

service arc. Ellipse records within each block should represent calculations performed at 1" intervals across the

service area's possible service arc; that is, if the service arc crosses the 180" meridian, the ellipse calculated at

180" east longitude should be immediately followed by the data corresponding to -179" east longitude. Further,

the blocks of data corresponding to individual service areas should appear with service area codes in an order

corresponding to the ordering of the Service Area/Service Arc file, discussed in section 2.3.1.3.

An Ellipse file that corresponds to a world-sized scenario occupies approximately 12.3 megabytes of storage.

Item Column

1 7 to 14

2 15to21

22 to 29

30 to 35

TABLE 2.3-4--FORMAT FOR ELLIPSE AND RAIN ATTENUATION DATA

Description

Eight character

beam code

Satellite longitude

for which ellipse and

rain data were

calculated, deg

Beam aimpoint

longitude, deg

Beam aimpoint

latitude, deg

(a) First record of three

Format Item Column

A8 5 36 to 40

F7.2 6 41 to 45

7 46 to 52

F7.2

F6.2

Description Format

Major axis F5.2

beamwidth, deg

Minor axis F5.2

beamwidth, deg

Orientation angle of F7.2

ellipse, deg

Item

I to I0

Column

I to6,

7to 12,

13 to 18,

19 to 24,

25 to 30,

31 to36,

37 to 42,

43 to 48,

49 to 54,

55 to 60 [

(b) Second/third record of three

Description

Rain attenuation (dB)

for each of up to 10

test points, calculated

at downlink frequency

Format Item

F6.2 II to 20

Column Description

61 to 66,

67 to 72,

73 to 78,

79 to 84,

85 to 90,

91 to 96,

97 to 102,

103 to 108,

109to 114,

115 to 120

Rain attenuation (dB)

for each of up to 10

test points, calculated

at uplink frequency

Format

F6.2

2.3.2 Intermediate Files

To utilize the NASARC (Version 4.0) software package for planning exercises, it is necessary to execute the

NASARCI module (the grouping program), the NASARC2 module (the arc determination program), the

NASARC3 module (the group arc extension program), and the NASARC4 module (the arc interchange program)

over all portions of the geostationary orbit that the user has defined within the Segments file. As results are

considered to be final only when all segments of the orbit specified by the user have been examined, it is clear

that intermediate results achieved using the NASARCI, NASARC2, NASARC3, and NASARC4 modules in one

portion of the arc must be stored for possible future consideration as other portions of the arc are examined.

Thus, intermediate files include those files which are generated and used by the NASARC (Version 4.0) program

modules on an interim basis; that is, they are files which contain data that are altered or updated periodically by one

or more modules for use by other modules in determining a final output solution. As such, these files require no user

intervention and may be treated as being transparent to the user. However, the user should be aware of the contents

of each such file and their approximate storage requirements, which are presented in the subsequent sections.
2.3.2.1 IntermediateSegmentsFile

The Intermedi_ Segments file is identical in format to the _ file discussed in section 2.3.1.1 and contains

similar data-western and eastern longitudinal limits of portions of the orbital arc and the grouping criterion value

to be applied within that segment. However, while the Segments file contains portions of the orbit that are yet to

be operated on by the NASARCI, NASARC2, NASARC3, and NASARC4 modules, the Intermediate Segments

file contains portions of the orbital arc that have already undergone analysis by these four modules. At the

conclusion of the analysis--when all portions of the orbit have been examined--the Intermediate Segments file is

identical to the original Segments file constructed by the user.

As each segment of orbit within the user's Segments file is encountered by NASARC 1, it is copied to the bottom of

the Intermediate Segments file. The Intermediate Segments file is then utilized by the NASARC2 module to determine

the cumulative orbital arc analyzed in order to rearrange prior allotted arcs for the accommodation of newly allotted

arcs within the orbit. Finally, the Intermediate Segments file is used by the NASARC4 module to restore the user's

original Segments file after all portions of the orbital arc listed have been examined for potential arc allocation.

The Intermediate Segments file may contain up to 40 records of fixed 80-byte length. Thus, the file may occupy

up to 3.2 kilobytes of memory.

2.3.2.2 Groups File

The Groups file, which is generated by executing the NASARCI module, is utilized as input by the NASARC2

and NASARC4 modules.

The Groups file contains a complete listing of all service areas, their corresponding service arcs, and transitional

arcs processed within the most recently examined portion of the orbit. It also contains a complete listing of all

compatible groups of service areas (and arc segments over which they exis0 that have been found by the

NASARCI module. The NASARC2 module chooses from this list in constructing sets of allotted arcs. As its first

record the Groups file contains a global transitional arc length that is read and reported by NASARC4.

Actual storage requirements for this file are somewhat difficult to predict since the number of records produced

by the NASARC 1 module depends on both the number of service areas processed and the set of technical

parameters supplied as input. However, NASARCI (Version 4.0) is capable of generating 90,000 groups and arc

segments; the list of service areas processed may occupy up to 300 records of the output file. As each record has

a fixed 80-byte length, this file may occupy up to 7.2 megabytes of storage.

2.3.2.3 Intermediate Allotted Groupings File

The Intermediate Allotted Groupings file, which is generated by the NASARC2 module, is utilized as input by

the NASARCI module and may be updated by the NASARC3 and NASARC4 modules.

As stated in the previous section, the NASARC2 module selects groups of compatible service areas, from the list

of groups and arc segments produced by the NASARC1 module, and attempts to allot portions of the orbit to

such groups. When the NASARC2 module finishes making such selections, the selections are appended to the list

of selections that may have been made in processing prior portions of the orbit within the Segments file. Prior

selections are also subject to revision by the NASARC2 module should revision become necessary to

accommodate the allotted arcs of new groups of administrations. Thus, the Intermediate Allotted Groupings file

contains all the compatible groups of service areas that have received allotted portions of the geostationary arc via

the NASARC2 module. The file also contains, for each such group of service areas, the boundaries of the

portion of arc that they have received (the allotted arc) as well as the boundaries of the segment of orbital arc

over which each such grouping has been found to exist (the group arc).

This file is examined by the NASARC3 module, which determines if any group are may be extended further over

the orbit. If such extension is possible for any group within the file, the Intermediate Allotted Groupings file is

modified to reflect such revised group arcs. The file is also examined by the NASARC4 module in seeking an

23
improvedarrangement of allottedarcs.If suchanimprovedarrangement is found, the intermediate Allotted

Groupings file is updated to reflect revised allotted arcs. The Intermediate Allotted Groupings file is then utilized

by NASARCI to eliminate service areas that have already received allotted arcs in prior steps from consideration

in the next portion of the arc to be analyzed.

The file may contain up to 150 records of 80 bytes each; therefore, the file may occupy up to 12 kilobytes of

memory.

2.3.2.4 Unallotted Groups File

The Unallotted Groups file is utilized as both an input and output file for the NASARC2 module.

As stated earlier, the NASARCI, NASARC2, NASARC3, and NASARC4 modules are exercised repeatedly over

the portions of the geostationary orbital arc that the user has defined within the Segments file. This is a

cumulative process, which results in the gradual development of a set of groups of compatible service areas and

their allotted arcs, over the span of orbital arc locations defined by the user's portions within the Segments file.

At the end of the NASARC2 arc allotment process for a particular segment (and cumulative arc), there may still

exist unaUotted groups whose group arc extends to one or both edges of this cumulative arc. The Unailotted

Groups file saves all groups whose group arc adjoins an edge of any previous cumulative arc. The file also

contains the group arc for each such group and the number of member service areas of each group. Since these

groups have the potential of existing beyond the bounds of the current cumulative arc, they appear in the

NASARC 1 output during processing of a future portion of arc in the Segments file. If they appear in the

NASARC1 output groups list, their group arcs appear to extend only as far as the bounds of the segment

currently being processed. Hence, in order to work with complete group arcs, it is necessary to save the

unallotted groups just described and merge them with the groups output by NASARCI in processing subsequent

segments. This is accomplished at the start of each NASARC2 run by appending the unallotted groups to the end

of the present NASARCI groups and combining the group arcs of duplicate groups where they are contiguous.

The maximum amount of group arc that exists within the current cumulative arc is then identified for each group.

Storage requirements are somewhat difficult to predict since the size of the file will depend on user-supplied

technical parameters; however, 4 megabytes should be a sufficient storage allocation.

2.3.2.5 Intermediate Selection File

The Intermediate Selection file is created and modified by the NASARC2 module. It contains information

gencrated by the NASARC2 module during each step of the arc determination process. The file contains

cumulative information in the sense that such information is gathered and retained within the file for each userspecified portion of the orbit that undergoes analysis. As a new portion is analyzed, the information generated is

added to existing information generated during performance of the arc determination process on previously

analyzed portions of the orbital arc. Thus, by examining the contents of this file, the user may follow the

decision-making of the NASARC2 arc generation process as applied to all portions of the arc analyzed.

The file contains information related to the current status of the analysis and to the decision-making processes of

arc determination. The current status of the analysis is reflected by the number of user-specified portions of the

orbit that have been processed, the longitudinal edges of the cumulative orbital arc span that has been analyzed,

and the edges of the portion of the orbit most recently examined. For informational purposes, the data contained

in the Input Data file are echoed within the Intermediate Selection file; also included is a list of service areas,

servicc arc boundaries, and any buffer arc lengths included in the most recent analysis of a portion of the arc.

The course of the decision-making processes involved in arc determination may be followed by examining various

ordered lists generated by the NASARC2 module. A list of critical service areas is produced; it is ordered by the

number of occurrences of each such service area in groups contained in the most current list of compatible

24
groups and group arc segments. That service area occurring in the fewest such groups appears at the top of the

list. This list also contains the priority (P1, P2, or P3) with which each service area is to receive an allotted arc

length. A list of critical groups--compatible groups of service areas which contain the critical service area--is

also generated and ordered by group arc boundaries, number of service areas included in the group, and the sum

of frequency of occurrence within any group of each critical group member. The frequency of occurrence of any

service area within a group is calculated by examining the most current list of compatible groups of service

areas. This list is periodically updated as service areas receive allotted arc lengths. While the list itself is not

presented in the file, information related to updating this list is presented in the file--for example, the number of

groups contained in the list before and after updating, the number of groups from which members were extracted

(due to receiving an allotted arc length), and the number of groups (if any) eliminated by selection of the critical

group to receive an allotted arc. The updated list is searched to determine if elimination of any service area not a

member of the critical group has occurred; such service areas are listed within the Intermediate Selection file as

are those service areas for which no allotted arc can be found. Finally, a complete list of groups selected, their

arc length requirements, and received allotted arc boundaries is generated.

Exact storage requirements for this file are difficult to predict. Once again, storage requirements depend to a

great extent on the scenario undergoing analysis. However, 4 megabytes for records of fixed 80-byte length is

felt to be a sufficient allocation for most scenarios.

2.3.2.6 Intermediate Improvement File

The Intermediate Improvement file is created and modified by the NASARC4 module. It contains information

generated by NASARC4 during the process of attempting to improve the most current arrangement of allotted

arcs in orbit. As was true for the Intermediate Selection file, the information contained in the Intermediate

Improvement file is cumulative over all segments of the orbit for which the NASARC4 module has been

executed. By examining the contents of this file, the user may follow the decision-making of the NASARC4 Arc

Interchange process over all portions of the arc analyzed.

As NASARC4 is executed during each new portion of the orbital arc specified in the Segments file, the program

reads and evaluates the arrangement of allotted arcs in orbit most recently determined by NASARC2 as an initial

arrangement, The initial arrangement and its corresponding objective values are reported in the Intermediate

Improvement file. After evaluating the initial incoming arrangement, the NASARC4 program attempts to find a

more efficient initial arrangement by performing improving pair-restricted interchanges of allotted arcs. An

interchange is pair-restricted if two candidate arcs may only be interchanged with each other. After this

operation, the improved initial arrangement and its objective values are reported in the Intermediate Improvement

file. When an efficient initial arrangement has been found, NASARC4 begins to examine alternative arrangements

generated by performing interchanges of allotted arcs. As improved arrangements are found, they are compared

with the best existing arrangement; NASARC4 determines which _,rangemcnt is preferred. As new preferred

arrangements are determined, the preferred arrangements are reported, with their objective values, in the

Intermediate Improvement file. When no more improved arrangements can be found, the best alternative

arrangement is indicated as such and written to the file, along with its objective values. The NASARC4 module

then attempts to ensure that allotted arcs within the best existing arrangement have sufficient separation from

other allotted arcs. If further separation for a given pair of arcs is not needed, NASARC4 reports that fact in the

Intermediate Improvement file. If, however, a pair of allotted arcs requires further separation, this is also

reported. The program attempts to gain as much separation as possible by progressively reducing the required

spacing between the two arcs. Each such attempt is also reported in the file. Finally, when maximal separation

between the necessary allotted arcs has been obtained, the final arrangement of the allotted arcs is reported to the

file along with objective function values for the arrangement.

Storage requirements for this file are, once again, difficult to predict; however, an allocation of 200 kilobytes of

storage for fixed-length, 80-byte records should be sufficient.

2.3.3 Output Files

Output files are those produced by one or more modules of the NASARC software package that are used to store

results at the conclusion of an exercise of the NASARC modules on a particular scenario. These results may be

25
thoseof asuccessful exercisewhichareoutputto theNASARCReportfiledescribedinsection2.3.3.1,the

CondensedReportfiledescribedin section2.3.3.2,andthePredetermined Arcfiledescribedin section2.3.3.3,or

theymaybethoseof anunsuccessful exercise--anexerciseinwhichdatainputerrorshaveresultedinpremature

terminationof oneor moremodules--whichareoutputtotheErrorMessagefiledescribedinsection2.3.3.4.

2.3.3.1 NASARCReportFile

Asstatedpreviously, theNASARCReportfileisproducedattheconclusionof a successful exerciseof the

NASARCpackageona particularscenario.("Successful exercise"refersonlyto thefactthatall moduleshave

executedsuccessfullyontheinputdataprovided;theusermaystillwishto improveontheresultsobtainedby

alteringhisorherinputdata.)TheNASARCReportfileisproducedbytheNASARC4moduleattheconclusion

of examinationof allportionsof theorbitspecifiedbytheuserwithintheSegmentsfile.

TheNASARCReportfilecontainscompleteinformationonall scenarioinputdatasuchasacompletelistof

serviceareasconsidered, theirassociatedservicearcs,associatedparameterssuppliedbytheuserforeachservice

area.a listof all user-specifiedportionsof theorbitalarcthathavebeenexamined, andalistof all interactively

specifiedinputparameters. If applicable, additional informationis printedaboutaffiliationof serviceareas.

Followingacompletedescriptionof theinputsuppliedtotheprogram,theNASARCReportfilepresentshe

resultsof exercisingtheNASARCI,NASARC2,NASARC3,andNASARC4modulesonthedatajustdescribed.

First.atableof compatiblegroupsof serviceareasselectedtoreceiveallottedarcsispresented, containingthe

groupselected,theirallottedarcboundaries, theirgrouparcboundaries, thelengthof theirallottedarc,andthe

numberof memberserviceareascontainedineachgroup.Overallresults,suchasthetotalamountof orbitalarc

utilizedforallottedarcs,thenumberof groupsof serviceareasthatreceivedsuchallottedarcs,thenumberof

serviceareasthatreceivedsuchallottedarcs,and(if any)thenumberof serviceareasthatdidnotreceive

allottedarcs,arepresentedwiththetable.A pictorialrepresentation of theallottedportionsof theorbitandthe

groupsof serviceareasto whichtheyhavebeenallottedisproduced, presentinga visualsummaryof thescenario

results.Furtherinformation,onaserviceareabyserviceareabasis,ispresentedfollowingthegraph.After

informationforindividualserviceareasisgiven,detailedinformationisgiven,if necessary, for unallottedservice

areas.This is followed by a cross reference table for three-character and eight-character service area codes.

Exact storage requirements of the NASARC Report file are, once again, dependent on the scenario supplied by

the user. However, an allocation of 160 kilobytes for fixed-length, 132-byte records is sufficient for most

scenarios.

When printing the NASARC Report file, it is suggested that the carriage control option be selected, as this file

contains carriage control characters and the resulting document is easier to read.

2.3.3.2 Condensed Report File

The Condensed Report file is also produced by the NASARC4 module at the conclusion of scenario processing.

This file contains selected information that is also presented in the NASARC Report file, discussed in the

previ_us section.

As is true for the NASARC Report file, the Condensed Report file contains complete information on all inputs

supplied to the NASARC software. Results are then presented, followed by information on unallotted systems (if

any) and concluding with a graphical representation of the predetermined arcs found by the NASARC software.

2.3.3.3 Predetermined Arc File

For applicatons of allotment planning of the Fixed Satellite Service at the 1988 World Administrative Radio

Conference. the NASARC software was used in conjuction with another planning software package residing at

2f_
the International Frequency Registration Board--the ORBIT program. The Predetermined Arc file, which is

produced by NASARC4, contains for each service area a three-character code, a corresponding eigth-character

code, the western boundary of the system's allotted arc, and the eastern boundary of the system's allotted arc.

This information was utilized by an external interface program to modify arc limits for each service area within

the Requirements Data file prior to using the modified file as input to the ORBIT program.

For the reasons just stated, it is not strictly necessary to generate the Predetermined Arc file. However, the file is

a useful short summary of the results of the NASARC programs on arc placement of systems for individual

service areas.

The Predetermined Arc file may occupy up to 24 kilobytes of memory, composed of up to 300 80-byte records.

2.3.3.4 Error Message File

The Error Message file may be written to by any of the NASARC0, NASSEP, NASARC1, NASARC2,

NASARC3, or NASARC4 modules under a variety of circumstances. Generally, these circumstances represent

errors in data input that result in a premature termination of the appropriate modules. Should the user encounter

such a premature termination, the Error Message file is an aid to discovering the source of the problem.

Generally, error messages that are written to the Error Message file are also written to the user's terminal; the

file provides a record of such messages for consideration at the user's leisure.

As errors that produce error messages are generally of sufficient severity to halt execution of the program, the

Error Message file will almost always contain only one such message. Thus, a storage allocation of 0.8 kilobyte

for fixed-length, 80-byte records should be adequate.

3.0 USE OF NASARC SOFTWARE PACKAGE IN PLANNING EXERCISES

This section provides the user with the information necessary to utilize the NASARC (Version 4.0) softwarc

package for generation of predetermined arcs for allotment planning exercises. Interface (NASINTRF), input

{NASARC0), satellite separation (NASSEP), grouping (NASARCI), arc determination (NASARC2), group arc

extension (NASARC3), and arc interchange (NASARC4) program structures are briefly discussed with the aid of

flowcharts also provided in this section. Guidelines for preparing input files are given as are suggestions for

interactively input technical parameter values. Suggestions for using ORBIT in conjunction with NASARC are

also given. Finally, a complete list of program-generated error messages is given along with information on

possible causes of such errors.

It is suggested that the user refer to the NASARC (Version 4.0) Technical Manual for detailed information on the

technical basis of the NASARC (Version 4.0) software package. It is also suggested that, if he or she has not

done so, the user refer to section 2.0 of this manual for information on input and output file structures and

formats as this information will greatly aid the user in constructing new files.

3. I Overview of NASARC Procedure and Program Structures

During the development of the NASARC software package, it was recognized that, for the software to be useful

for planning exercises involving large numbers of service areas, a piecewise approach to allotting orbital arcs

would have to be applied to the geostationary orbital arc. The NASARC procedure allows the NASARC1.

NASARC2. NASARC3, and NASARC4 modules to be applied in such a piecewise approach to a user-specified

partitioning of the orbital arc into individual segments of arc to be successively examined. The user is referred to

figure 3. I-I, which presents a flowchart of the NASARC procedure, and to figure 3.1-2, which presents a

flowchart of the interaction between modules.

27
Bct'orcusingany of the NASARC0, NASSEP, NASARCI, NASARC2, NASARC3 or NASARC4 modules, it is

necessary to create input files for the programs. If the user possesses a Requirements Data file (see section

2.3. i.2), NASINTRF--the interface program--may be utilized to create the Service Area file, the Point Sets file,

and the Affiliated Sets file. If the files are to be created independently of the interface program, they must adhere

to the formats described in sections 2.3.1.3, 2.3.1.4, and 2.3.1.5, respectively.

Prior to use of the NASARC1, NASARC2, NASARC3, and NASARC4 modules within a portion of the orbit, it

is necessary to collect data from the user and to verify the input data supplied in external files to assure that the

NASARCI, NASARC2, NASARC3, and NASARC4 modules will be able to execute successfully. These

functions are performed by the NASARC0 module--the input program. The NASARC0 module is utilized once

(see figs. 3.1-1 and 3.1-2); the data that are collected and verified are then utilized over all portions of the orbit

to be examined for the given scenario.

Required satellite separations are needed as input data by both the NASARC2 and NASARC4 programs to

determine the most compatible arrangement of allotted arcs within the orbit. The satellite separations are

calculated by NASSEP--the satellite separations program. Since NASSEP also requires the input data supplied to

NASARC0, it is executed just after NASARC0 in the NASARC procedure. The resulting separation matrix file

may then be used in the remaining steps of the procedure.

Within each segment of the arc examined within the NASARC procedure, several major functions must be

performed to obtain allotted arcs for service areas. First, all possible compatible groupings of service areas and the

arc spans over which each such grouping exists (the group arc) must be determined within the portion of the orbit

currently being examined. This function is accomplished by the NASARC1 module--the grouping program. Next,

selections of compatible groups and allotted arcs must be made in a manner which includes as many service areas

as possible and which provides each chosen group with an allotted arc within its group arc. This function is

accomplished by the NASARC2 module--the arc determination program. Groups of service areas that have been

selected to receive allotted arcs within their group arcs must next be examined to determine if their group arcs may

be extended further into the orbit. This step is necessary to provide as much flexibility as possible in remaining

p_rtions of the orbit when exercising the arc determination procedure, as the procedure may need to adjust

pre_ iously allotted arcs in order to accommodate new allotted arcs. This function--the extension of group arcs for

t_ssible future use--is performed by NASARC3--the group arc extension program. Finally, it is possible that the

existing arrangement of allotted arcs found by NASARC2 may be improved with respect to compatibility of

sy_tcms in adjacent allotted arcs. This function is performed by NASARC4--the arc interchange program.

A flowchart illustrating the sequence of, and interaction between, the NASINTRF, NASARC0, NASSEP,

NASARCI, NASARC2, NASARC3, and NASARC4 modules appears in figure 3.1-2. The data conversion and

translation operations performed by the NASINTRF module are illustrated in the flowchart appearing in figure

3. I-3. The data-gathering and verification operations performed by the NASARC0 module are illustrated in the

flowchart appearing in figures 3.1-4(a) to (c). The operations of the NASSEP module are illustrated in the

flowchart appearing in figures 3.1-5(a) and (b). The operations of the NASARC1 module, are described by the

flowchart contained in figures 3.1-6(a) to (f), 3.1-7(a) to (d), and 3.1-8. Processes of the NASARC2 module, are

described in the flowchart in figures 3. l-9(a) to (b) and 3.1-10(a) to (c). The operations performed in NASARC3

are illustrated in the flowchart appearing in figures 3.1-11(a) to (e). Finally, the operations performed by the

NASARC4, module are illustrated in the flowcharts appearing in figures 3.1-12(a) to (g), 3.1-13(a) to (b), and

3.1-14(a_ to (c). These flowcharts are referred to throughout the remainder of this section when the NASARC

mt_dules are described. Where possible, references are also made to specific subroutine names; the user will

recall that complete lists of subroutine names for the NASARC modules appear in tables 2.2-2 through 2.2-8.

tTt?xl resumes on page 70.)

3 I. I NASINTRF Module

The NASINTRF module, as stated previously, serves as an interface from the Requirements Data file (see section

2.3.1.2) to the remaining NASARC modules. The NASINTRF module extracts and translates data from the

Requirements Data file into files that are usable by NASARC--the Service Area file, the Point Sets file, and the

Affiliated Sets file.

2_
The NASARC EXEC Procedure

Figure 3.1- I.

_7 t"

I 'm"_ """ T° /-_-------I

E lIROCnil_ FR011 I

I i.W_ _HD EXlEOJTE

le41Sl_i "IHE/_C

I

W.li_O_ THE ARC

¢_bmqT RI.E

29
NASARC Program Module File Overview

ORIGINAL PAGE IS

OF POOR QUALITY

r i

il'--_- I=_>

NASINTRF

_ql,mll

MAll&

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Ttm 6r_r_i

1

NASARC2

At©

l_olrun

NASARC3

GroupAro

Proorm

,1

NASARC4

Figure 3 1 2

L=m

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OF POOR QI.:_4L_Ty.

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/ __"_/

p_m

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l,,ll_'tiillt nl . I u.,lllt nl I

Figure 3.1-3.

31
ORIGINAL

OF POOR

NASARCO The Input Program

(i) Figure 3.1-4(a).

32
OF POGF: " :'-'"

(9 C)

M_

IP[-,_ m

fILE

NO
ORIG|NAL P_,_= J'_3

OF POOR QUALITY

NO

Figure 3. I-4(c).

34
OF POOR QUALITY

NASSEP -- The Sstelllte Sepsrstlons Progrsm

® Q

Figure 3.1-5(a).

35
ORiGl_qt_L ' _'_*_ :"

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Figure 3.1-5(b).

36
NASARCl The Grouping Program

Q

Figure 3.1-6(a).

37
ORIGIN';_L r_"_" i_

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pl_Y IB.L_

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Figure 3, l-6(b).

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Figure 3.1-6(c).

(9

39
ORIGINAL FA_ i_

OF POOR QUALITY

NO

Figure 3. l-6(d).

NO

@
OF POOi_ qU_Lii'Y @@0®

®

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Figure ?,. I-6(e).

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41
( ,) OF POOR QUALITY

IWIAll_ POR I"I'IB LOCAll_ !

i

I¢Ol.l_m OF M/_11_ "i

I BKIMB_'II ,_ICL /

m_,llNI/0' 1HII _ r

Q_OUPARCK ®

42
Verification of Sufficient Space Station

Separation at Grouping Criterion

TOEl" GROUPING SEPARATION CRITERION EQUAL i

TEFIMIqE COfVIECT BJ.JPaEi

FOe_rrm _ I

AREA AT WARI"ED I

PACE IrrAllON LOCAT1ON |

I DET'ERMINECORRECT ELLIPSEi

FOR NTEFM:B:I_ IERVR£ I

kqEA AT INTERFERING I

SPACESTATIONLOCATION J

NO

UNIT IIO:TB_IkCNAL I

IT 19:INPUT DATAFILE J

J s_EF.O__.,_,._u_/

DATAFILE TO "YES': /

7_,T _O..ES_ TO/

/TE_,,_. _ ._o_ FU /

NO

THE NECESSARY

BIJPSE BEEH

FOUN_

IS

TO BE

RERFORMED9

NO

IN INPUT

DATA FILETO 'YEll';

B;IROR MESSAaE TO

tqa_ML'qlN.AND EI_tOR FILE

Figure 3. l-7(a).

YES

43
OR|G|NAL PP_GEiS

OF pOOR QUALITY

® E)

i==_=_1

Figure 3. l-7(b).
®

_'_ .... _' _" _ i .",, '_i_'. ' _:_ Q

/ vNr_m_'ma.nt_.Mc_ I

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f4gure 3.|_7(c_

I
OF POOR QUALITY (i)

i

I----I

EVALLUffE_ OF

EARTH #ITA'IION

AN'I_ "r_ IN'm_

UTI_

(S)

IIET00_'I_ 14.AB

L_TOZ_

Nm )

EQU_ 'I_ _E

Ir

mm

Figure 3. l-7(d).

4(-,
FORMATION OF GROUP ARC SEGMENTS

AND CREATION / UPDATING OF MASTER GROUPS LIST

DETERMINE ARC SEGMENTS FOR B.OCK OF GROUPS :

t PERFORM A COMPOUND SORT ON THE LIST :

THE MAJOR SORT KEY IS THE GROUPS FIELD

ISORTED IN ASCENDING ALPHABETIC ORDER).

THE MINOR SORT KEY IS THE A_C LOCATIONS FIELD

{SORTIED IN ASCENDING M.JIv_RIC O_JOEl_.

THIS WILL FORCE IXI::_TE GROLPS TO APPEAR

TOGETHER WITH THEIR ARC LOCATIONS ORDERED V_ST-EAST,

2. WORK DOW_ THE LIST _ COMBINE ARC

LOCATIONS OF DUPUCATE GROLJPS WHERE

THEY ARE/M_JACENT TO FORM GROI.IP AFIC

SEGMENTS FOR EACH _ CaciouP.

YES

i

IINtTt_tJZE MASTER LIST OF I

I C,ROUPS_0 GROUP_ I

! SEGMENTS I

NO

I illm i

"MERGE GROUPS AND ARC SEGMENTS INTO E_-_rlNG MASTER LIST

BY COMBINING ARC SEGMENTS OF D(PUCATE GROUPS WHERE

THEY ARE CONTIGtJOU_ PERFORM THE FOLLO_NG STEPS:

ii

t APPEND GROUPS AND ARC SEGMENTS FROM LATEST BLOCK TO

END OF EXISTING LI_T.

i

2 PERFORM COMP(XJNO SORT ON RESULTING LIST:

a. PRIMARY SORT KEY IS GROUPING SORTED IN ALPHABETIC ORDER

b. SECONDARY SORT KEY IS WEST LON_ OF GROUP ARC

SORTED IN ASCENDING NUMERIC ORDER

[_Pt.W_TE GROUPS WILL NOW APPEAR TOGETHER IN THE LLST

WITH THE ARC SEGMENTS FOR ANY PARTICIJJU4 GROUP ORDERED

_E ST- TO-EAST.

i

1

3, WORK DOWN THE LIST AND JOIN THE GROUP ARCS OF: OIJPIJCATE

GRO4JI::)S WHEF_ THEY ARE ADdACENT, THEN DELETE FiEDUNDANT

GROIJP_

Figure 3.1-8.

47
NAILARCS - THE ARC DETERMINATION PROGRAM

ORIGINAL P_.G_ _3

OF pOOR QUALITY

IqLE

Figure 3.1-9(a).

_mawwcr _ _-,m,_.mu_'TMmrrY I

_,w_'_ufr_ I I n-u_m.o'ummmmr I

'l__"lt_ I ! n-_,_r,._rY I
OF POOR QUALiTy

__J

__/

NO

Figure 3. l-9(b).

4t_
ORIGINAL p,_GE _3

OF POOR QUALITY

r

u= [

_ _,,_I =,,=.,,=-

I'TNW CRI/I_L mOUll

OFI_UP &q¢

NASARC2

ALLOTTED ARC

SUBROUTINE

® ©

5O
OF PO0_ QU,!_.L_T_t

_ I_F_L 0

lAVE CUNqm'T U

A/4) _R

OL.DWt'T-W_O_

IIGlflwLIJITal_,

114'T1.FT,BlrmlT.

IIIII_niT.IIITE ILIIs't IB_

y

Figure 3.1-10(b). @

51
ORIGINAL PAGE tS

Oi= POOR QUALITY

© @

YIE8

Figure 3. L-IO(c).

52
OF POOR QU_L_._-,_:

NASARC3 -- The Group Arc

Extension Program

i

_-/= /

2

-7

L

=/__"m,/--

Figure 3.1-1 l{a). O
ORIG_Nt_L .......

OF POOR QUALii+¢

r JNtTt3:SERV)CEAREA !

RIlE

rR_IT'PGNT LIE SEIS !

'/uNr/le: ELLIPSERLE J

?

I°°°++-I _-IO_E GROUP,I_RC:6WILL

REt,'PDATED

/

l _i_°uP TO iEX_Ua_ /

._qF.,l,lIN (IqOUP I

=/_.= ,=.v,=mm,/

NO

SET OF8_(X/

TO BEE)_k4NEO/

NO

SEFMOE

YES

r_Ul_l .uI'IT1_ 1EllIINAL I

tt ml40R MBIIAeE FILEI

t2 INl_n O,k'fARLE J

®

Figure 3,1 II(bL

54
OF POOR _Ez'_+r+._+, ?

ITD_F_Iq

aqOUP +_qc EIqI+N_

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J UI,g_/IlUNIX I

(3)

4

IFI' I_I1_11B.1_

I=1./_ - 1

®

Figure 3.1-1 l(c).

55
56

ORIGINAL P,_(:,:. -F: ......!_

OF POOR QUALIFY

(D C) () O

NO

NO

O ®

®

NO

l

Fig Q O ® ® ,1,o
®

YES

NO

I _ QROUP/_RCTO I

CURRBCr ARC LOP.A'rlON

l r

I MOWE "TONI_ ARC

LOCATIONTO I_ EXAMI_O !

NO

NO

Figure 3. l- l I(e).

YES

® ®

57
oR|GINAL FA£'_ '"

OF pOOR QUALITY

NASARC4 The Arc Interchange Program

NO

58
OF POOR QUAL;'!"K

i

(.._m I

i

NI_ COST IW_ _WS

_ m'BON W_I'_

_ AL_.W OF m

l,J

Q Figure 3.1-12{b). Q

C)

®

C)

59
ORIGINAL P,_.C'_t_

OF POOR QUALITY

e e e _ e

ADO RL_ al_ J

POR I_l TO 11Pli_l.POR

glROI,JP61ANOJ

0_'1" ldt ,, ling OF m_atll_m

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m _l_lBams M

aMuP ,I

Q Figure 3.I-12(c).

6O
OF POL_-_..... ':__

OF GMU_ OLE_'N_ VAI._ I

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NO

Q Figure3.1-12(d).

61
ORIGINAL PAGC _,

OF POOR QUALITY

® ® ®

®

®

! -='-". I,,,,,-=.®

ii I .=r.=.,=.F

I

6

Figure 3.1-12(e).

®

62
Figure 3.1-12(f).

_ _11Q

63
ORIGINAL PAG._ _S

OF POOR QUALffI'

®

NO I

lqII_ lq.MIIItL TO

II

II1"II_"I1,1_I I

IIfl1.Y ImIqInIID

I

_i_"_'_'n'' I IIIIq,IIl I,IT f

_ A/qI/_I_IM*ITIRL

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I RIIWIIIT,_III

PIqIIllmIID _qC U

./ UIT Ill IqIl_flT FU I

'r

( .. )

Figure 3.1-12(g).

64
Caloulstlon of Matrix of Feasible Interohsngee

@

HO

NO

Figure 3.1-13(a).

(9 ®

65
E)

ORIGINAL PAGE IS

OF POOR OUALITY

Figure 3.1-13('o).

66
Generation of New Aro Arrangement Through

Allotted Arc Interchange

I GN.a.CATE NL_ (:BJECTNE J

,, VN.UIEFOR 11H ILOT: J

YES

Figure 3.1-14(a).

67
ORIGINAL PAGE IS

OF POOR QUALITY

NO

NO

NO

II

ILOTWl

NO

68
0 DLw'_ _ _ _

OF POOR QUALITy

(Z)

NO SIT IMl_ovma_1"

NO

I

Figure 3. I- 14(c).

69
The NASINTRF module need not be used unless the user wishes to utilize a Requirements Data file; for most

applications, the user will want to create his own Service Area, Point Sets, and Affiliated Sets files. Therefore,

further information on the NASINTRF module is not presented in this manual, with the exception of the

flowchart presented in figure 3.1-3.

3.1.2 NASARC0 Module

As stated previously, the NASARC0 module collects data from the user and verifies data present in externally

prepared input files to ensure successful execution of NASARCI, NASARC2, NASARC3, and NASARC4 over

all portions of the orbit to be examined. (See fig. 3.1-2.)

Input data file verification is performed first. The NASARC0 module first collects constants from the Service

Area file (see section 2.3.1.3) that will be used in the allotted arc length equation within NASARC2. If all four

constants are zero, NASARC0 prints an error flag at the top of the Input Data file and writes an appropriate

message to the terminal and the Error Message file; otherwise, NASARC0 proceeds. The Segments file is then

read by NASARC0; the user will recall from section 2.3.1.1 that the Segments file contains user-specified

portions of the orbit to be successively examined by the NASARCI, NASARC2, NASARC3, and NASARC4

modules. NASARC0 verifies that the portions of the orbit specified within the Segments file form a contiguous

cumulative arc when joined together. If the specified portions of arc do not form such an arc, the error flag

within the Input Data file is appropriately set, and error messages are written to the terminal and the Error

Message file. After verification of the Segments file, NASARC0 proceeds to perform several checks on the

Service Area file data (see section 2.3.1.3): lengths of service arcs are checked to ensure that they are feasible;

service arcs of affiliated service areas are checked to ensure that they intersect; and individually specified antenna

characteristics are verified as valid. If any invalid specifications are found, the appropriate error flags and

messages are written to the appropriate files. Information gathered from the service area file--such as presence or

absence of affiliations between service areas--is used to set appropriate flags within the Input Data file produced

by NASARC0. If affiliated sets of service areas are present, NASARC0 reads the Affiliated Sets file (see section

2.3.1.5) and verifies that the appropriate number of member service areas for each set are present within the

Service Area file. If the Service Area file and Affiliated Sets file are not in agreement, appropriate error flags

and error messages are sent to the appropriate locations. If the two files are in agreement, NASARC0 then

verifies that the same set of space station antenna parameters have been specified for all member service areas.

(The user will recall that an affiliated set of service areas consists of dispersed service areas that are intended to

be served from the same satellite.) If such agreement is not found, the appropriate error messages and flags are

produced. If agreement exists, NASARC0 has concluded the file verification portion of its operation. (See figs.

3.1-4(a), (b), and (c).)

Following verification of externally prepared input data files, NASARC0 queries the user for input parameter

values to be supplied interactively, such as date and time of run, uplink and downlink frequencies, percent-oftime outage due to rain, and an upper limit on rain attenuation, default earth station antenna characteristics, and

default space station antenna characteristics (see fig. 3.1-4(c)). Further information on the interactive prompts

issued by NASARC0, and expected responses, is presented in section 3.2.5.

Prior to conclusion of the NASARC0 program, the user's responses to interactive prompts are written to the

terminal; the user is at this time afforded the opportunity to alter his or her input values. If any values are

altered, the appropriate NASARC0 operations are repeated. When all values are specified to the user's

satisfaction, NASARC0 concludes by producing the Input Data file (see section 2.3.1.6) utilized by NASSEP,

NASARC1, NASARC2, NASARC3, and NASARC4 (see fig. 3.1.4(c)).

3.1.3 NASSEP Module

The functions of NASSEP, the satellite separations program, are to find the required separations between each

pair of satellites corresponding to each possible pair of service areas present in the Service Area file and to write

a separation data matrix to be utilized by the NASARC2 and NASARC4 modules in performing their functions of

70
positioningthe interchanging allotted arcs. The format and use of the Separation Matrix file are given in section

2.3.1.7 of this manual. This program requires much the same input data as does NASARCI, the grouping

program. The Input Data file, the Point Sets file, the Affiliated Sets file, the Service Area file, and the Ellipse

file are used as inputs to the separation program. This program does not require any segment information as it

operates on the entire geostationary orbital arc,

The satellite separations program is used in the NASARC process to calculate the maximum required orbital

separations between the satellites of each service area or affiliated set of service areas based on achieving a given

single-entry C/I. A bisecting search process is utilized to collapse on the required separation which allows the

target C/I for the wanted system to just be met. The target C/I for each system is determined from the aggregate

C/I value given in the Service Area file for each service area by using set ratio between aggregate and singleentry C/l's which is set in the main program module of this program. It should be noted that larger values of ,he

ratio in question result in larger required separations and smaller values result in smaller required separations.

Ultimately, the separation information stored in the output file is used by NASARC2 and NASARC4 to effect a

reduction in the interference between adjacent groupings which are selected in the NASARC process.

NASSEP first sets various constants required for the calculations in subroutine SETCON and places them in a

common block for use by the many subprograms in NASSEP. Input parameters are read from the Input Data file

and the wavelength is calculated from the transmission frequency for use in antenna calculations. The global

scenario information is read from the Service Area file and then the individual service area information is read in

for each service area present in the Service Area file. Next, the program checks the affiliated set flag from the

Input Data file to determine if affiliated sets are present in the scenario. If they are present, the program

determines who the members are in each affiliated set and uses subroutine INTRST to find the intersection of the

component service areas' service arcs; this intersection then becomes the affiliated set's service arc.

The polygon/test point data for each service area are read from the Point Sets file using subroutine RDPTS2. Thc

number of arc increments (integral orbital locations) for each service area are calculated from the service arc

information. The program then calls subroutine CREAT2 to fill the ellipse array with all the required cllipse

information for the scenario.

The satellite separations program operates on the premise that the worst-case required orbital separations between

any two service area's satellites occur at the ends of the intersections of their service arcs. This has been shown

inductively in several informal studies. Thus, for each pair of wanted and interfering satellites corresponding to

the service areas delineated in the Service Area file, the following procedure is performed. First, the program

checks each pair of satellites to see if (1) the wanted and the interferer are the same service area, (2) the wanted

satellite is operating as uplink only and the interferer as downlink only or vice versa, (3) both wanted and

interfering satellites are existing systems, or (4) both wanted and interfering satellites are from the same affiliated

set. If any of these four cases are true, the program sets the maximum required separation to 0* and goes on to

the next pair to be examined.

The program next checks to see if the two service areas in question have service arcs that intersect. If they do

not, subroutine NEAR is called to find the two closet endpoints, the wanted satellite is put at the edge of its

service arc closest to the interfering satellite, and the interfering satellite is placed at the edge of its service arc

closest to the wanted satellite. This situation represents the least possible orbital separation for the pair of

satellites in question. If the service arcs do intersect, both the wanted and interfering satellites are placed at the

western edge of the intersected arc.

At this point, subroutine CICHK2 is called to determine the achieved C/I value for the present separation (i.e..

0* for the intersecting case and the nearest separation possible for the nonintersecting case). Subroutine CICHK2

calculates the achieved C/I value for the current positions of the satellites using all the technical parameters

available to it. It calls subroutine ANGLES to calculate the satellite and earth station antenna off-axis angles and

the half-power beamwidths in the direction of interest (i.e., towards the worst-case point) and subroutine DISC to

calculate the satellite and earth station antenna discrimination values. If the achieved C/I is greater than or equal

to the required C/I, then the required separation for this arrangement is set to zero.

71
If this arrangement, which corresponds to the minimum possible separation for the two satellites under

investigation, does not achieve the required C/I, then the interfering satellite is placed at the western edge of its

service arc and the available C/I is again calculated. If the available C/I exceeds the required amount, the

interferer is moved toward the wanted satellite using subroutine BISECT to do a bisecting search routine and find

the minimum required spacing. If the available C/I does not exceed the required C/I, then the wanted satellite is

positioned at the eastern edge of its service arc and the available C/I is calculated. If the achieved C/I is still not

greater than the required C/I, then the required separation for this case is set to the difference between the two

satellite positions. If the achieved C/I is greater than necessary, then the current interval is reduced using the

bisecting search algorithm by moving the wanted satellite toward the interferer satellite until the separation found

is the minimum necessary to achieve the required C/I.

Similarly, the next operation is to position the wanted satellite at the western edge of the intersected arc and the

interfering satellite at the eastern edge of its service arc to get the opposite case to that which was just examined

Once again, the achieved C/I is evaluated and if it is greater than necessary, another bisecting search is

performed moving the interferer rather than the wanted satellite until the minimum separation which provides

sufficient C/I is found. If greater separation is required than this case provides, the wanted satellite is positioned

at the western edge of its service arc and the achieved C/I is found once again. If the available C/I exceeds the

required C/1, then the bisecting search is used to reduce the separation to the correct amount by moving the

wanted satellite toward the interfering satellite. If the achieved C/I does not meet or exceed the required C/1,

then the required separation for this case is set equal to the maximum allowable within the service arc constraints

of the given pair which is defined by the wanted and interfering satellite locations.

Next, the identical operations must be repeated for the case of the wanted satellite being placed at the eastern

edge of the intersected arc. If the service arcs of the pair in question intersect, then both the wanted and

interfering satellites are placed at the eastern edge of the intersected arc. If the service arcs do not intersect, then

the wanted and interfering satellites are placed at their nearest boundaries with respect to each other as given by

subroutine NEAR. The C/I is evaluated for this arrangement; if the available C/I exceeds the required value,

the required separation for this case is set to 0". If the achieved C/I does not exceed the requirements, the

interferer is positioned at the western edge of its service arc and C/I is evaluated once again. The rest of the

process for this pair of wanted and interfering satellites is analogous to that presented in the preceding paragraphs

except that the wanted system is initially positioned at the eastern edge of the intersected arc rather than at the

western edge.

Once the maximum required separation between this pair of wanted and interfering satellites has been found, the

roles of wanted and interferer are reversed and the exhaustive exammation of all possible arrangements of the

two satellites in question is repeated. When the separation has been found for that pair of satellites, all other

possible pairs of satellites are examined in like fashion. For each pair of satellites, the maximum required

separation found is the maximum of all the described cases regardless of which satellite was the wanted and

which was the interferer. Both separation matrix entries will have the same value; thus, the separation matrix will

be symmetric.

If there are any affiliated sets present in the given scenario, the program consolidates their separation entries into

a single row and column as if each affiliated set were a single service area because members of an affiliated set

of service areas are served from the same satellite. Lastly, NASSEP outputs the separation data to the Separation

Matrix file.

A flowchart of the NASSEP module is presented in figures 3. l-5(a) and (b).

3.1.4 NASARC 1 Module

The NASARC1 module, as stated previously, enumerates compatible groupings of service areas and the arc spans

over which each such grouping may exist within the portion of the arc currently being examined.

72
Acompatiblegroupof service areas consists of a set of service areas, each of which is compatible with all other

members on a pairwise basis. Pairwise compatibility between service areas is assessed on the basis of the satellite

separation required to allow systems serving both service areas to meet a target single-entry C/! value. A usersupplied grouping criterion, extracted by the NASARC1 module from the Segments file, expresses (in degrees of

orbital arc) the maximum orbital separation allowable between systems at which the target C/! value may be

achieved for compatibility. That is, if systems serving two service areas achieve or exceed the target C/I xalue at

the grouping criterion spacing, they may be placed closely together in the orbit and are hence compatible.

Over the range of orbital locations currently being examined, assessment of compatibility between all possible

pairs of service areas takes place. Groups of systems that may be spaced closely together in orbit (i.e., those that

are compatible) are enumerated at each discrete location in the current portion of the orbit. These groups are

periodically accumulated into a list of compatible groups and arc spans over which each such group may exist

until all possibilities for compatibility in the current portion of the orbit have been exhausted.

The NASARC1 module first collects needed inputs from the Input Data file (see fig. 3. l-6(a)). These inputs

include technical parameter values supplied by the user as well as other data that affect various operations within

the program (see section 2.3.1.6).

The second input file required by the procedure is the Service Area file, which contains a list of service area.

their eastmost and westmost feasible arc locations, and data specified for each service area (see section 2.3.1.31.

This file is utilized to establish a preliminary list of service areas to be examined for compatibility within the

current portion of the orbit.

If the appropriate flag within the Input Data file indicates that affiliated sets of service areas are to be taken into

consideration, NASARCI then reads the Affiliated Sets file (see section 2.3.1.5). The user will recall that

affiliated sets of service areas--geographically dispersed areas that are to be served from a single satellite--

require special handling within NASARCI (see figs. 3.1-6(a) to (d) and (f)).

As described in section 3.1, the NASARC1, NASARC2, NASARC3, and NASARC4 modules are applied to

successive portions of the orbit specified by the user. Thus, any given execution of the NASARC1 module may

follow an application of the NASARCI, NASARC2, NASARC3, and NASARC4 modules to a prior portion of

the orbit. The user will also recall from section 3.1 that the purpose of the NASARC2 module is to select

compatible groups of service areas from those found within a portion of the orbit and to determine allotted arcs

for the selected groups. Thus, service areas that are included in such groups have already received allotted arcs

and do not need to be considered further by the NASARC1 module in subsequent segments of the orbit. For this

reason, the NASARC1 module utilizes the Intermediate Allotted Groupings file (see section 2.3.2.3) as input; the

service areas that have received allotted arcs are eliminated from the preliminary list of service areas to be

considered. If a service area that has received an allotted arc is, in fact, an affiliated set of service areas, its

member service areas have received allotted arcs and are thus also eliminated from the preliminary list of serx ice

areas to be considered within the current portion of the orbit (see figs. 3. l-6(a) and (b)). Such elimination of

service areas that need no longer be considered greatly reduces the computer time required to analyze all portions

of the orbit.

The NASARC1 module must next determine the portion of the orbit to be examined for compatible groups of

service areas. The user will recall that the portions of the orbit that are to be analyzed are specified within the

Segments file (see section 2.3.1.1). The top record of the Segments file defines the western and eastern arc limits

of the current portion of the arc to be examined and the grouping criterion to be applied within that segment;

when the top record has been read, the remaining records are read and rewritten to the Segments file; the

updated Segments file thus contains, in its top record, the longitudinal limits and grouping criterion for the next

portion of the orbit to be examined. The limits and grouping criterion of the current portion of the arc to be

examined by NASARC1 are also written to the Intermediate Segments file (see section 2.3.2.1), which contains

the portions of the orbit that have been examined (see fig. 3. l-6(b)).

The service arcs of the service areas contained in the current list are then compared with the current segment to

be analyzed by NASARC1; service arc boundaries are adjusted internally--i.e., within NASARCI--to conform to

73
theboundariesof the current segment. If a service area's service arc does not intersect the current segment to bc

examined, that service area is eliminated from the list of service areas to be considered (see figure 3.1-6(b)). A

further check is performed, if applicable, to determine if all affiliated service areas within a set are present within

the current segment. The user will recall that affiliated sets of service areas must be treated in an all or nothing

manner--that is, all numbers of an affiliated set of service areas must be able to be included in a compatible

group or no members must be included. Thus, if the service arc of any member service area of an affiliated set

does no1 intersect the current segment, the remaining member service areas must be eliminated from the list of

service areas to be considered (see fig. 3.1-4(c)).

The list of service areas to be considered has now been finalized. Intersections of their modified service arcs

(i.e., the segments of service arc that lie within the segment currently being examined) are determined for all

pairs of service areas using subroutine INTRST. Sets of polygon points for service areas are extracted from the

Points Sets file using subroutine RDPTS; if point sets are not found for all service areas, the error flag within

the Input Data file is changed appropriately, error messages are written to the Error Message File and the

terminal, and NASARCI ceases execution (subroutine ERR) (see fig. 3.1-6(c)).

After the extraction of polygon points from the Point Sets file, NASARC1 creates an array of needed ellipse data

extracted from the Ellipse file using the CREATE subroutine. Once again, if an error in collecting the needed

data is encountered, appropriate flags and messages are written and the NASARCI module stops (subroutine

ERR).

Beginning with the westmost possible arc location for any service area, the NASARC 1 module calculates a

compatibility matrix and enumerates groups of compatible systems for that location. The location is then

incremented and the process is repeated until all possible discrete arc locations within the current segment are

exhausted. In constructing the compatibility matrix for each location, compatibility assessment for a pair of

satellites is not performed unless the current location lies within the intersection of the feasible arcs for both

service areas (see figs. 3. l-6(d) and (e)).

At each arc location, calculation of a compatibility matrix takes place. Each entry indicates whether or not a

target C/I value is achieved with a specified orbital separation between two satellites, serving a pair of service

areas, where the satellite regarded as wanted is represented by the row index and the interfering satellite is

represented by the column index. Due to differences in the geographical extent of the service areas corresponding

to the satellites (and thus, beam coverage size), the C/I achieved when one satellite is seen as wanted and the

other is regarded as an interferer may not be identical to the C/I achieved when the roles of the two satellites are

reversed. Thus, the compatibility matrix is initially nonsymmetric (see fig. 3.1-6(f)). Compatibility is indicated by

a one (1); incompatibility is indicated by a zero (0).

The user will recall that affiliated sets of service areas require special treatment in the determination of

compatible groups of service areas. If two service areas are members of the same affiliated set, they are

regarded, automatically, as compatible. However, compatibility between each member service area and all other

nonmember service areas is assessed in the manner to be described.

Calculation of the C/I achieved by each pair of systems at the orbital separation specified by the grouping

criterion is performed on the basis of the total link performance achieved (subroutine CICHK--see figs. 3.1-7(a)

to (d)). Thus, system characteristics are required by the program and are read from the Service Area file. The

characteristics required are those representing the satellite antenna pattern, earth station antenna patterns, satellite

and earth station receiver noise temperatures, satellite and earth station power levels, uplink and downlink C/l's,

target aggregate C/l, uplink and downlink power calculation flags, existing system flag, and link calculation flag.

As falloff from the on-axis satellite antenna gain is most often expressed in terms of relative off-axis angle (i.e.,

the off-axis angle of the satellite antenna divided by the half-power beamwidth in the direction of interest), the

half-power beamwidth in the direction on interest must be calculated (subroutine ANGLES). For this reason, a

file of ellipses covering the service areas is also utilized by the program. The ellipses needed by the program are

extracted from the Ellipse file using the CREATE subroutine. The achieved C/I value is calculated at the given

orbital separation between satellites as follows (see figs. 3.1-7(a) to (d)). The current arc location is assumed to

be the location of the wanted satellite; what must be determined is whether or not a given orbital separation

74
betweenthislocationandthelocationof theinterferersatelliteallows the wanted system to meet a target C/I

calculated from user inputs. First, the uplink C/I is calculated, provided that the link calculation flag indicates to

the program to do so. Free space losses are calculated on both wanted and interfering uplink path. Depending on

the power calculation option for the uplink, the user-supplied values for wanted and interfering earth stations may

be utilized or the values may be calculated from the uplink carrier to noise ratio (C/N). Antenna discriminations

are calculated for the interfering earth station toward the wanted spacecraft, the wanted spacecraft toward the

interfering earth station, and the wanted spacecraft toward the wanted earth station (subroutines ESOFF.

ANGLES, and DISC). The achieved uplink C/I value is then determined.

A similar operation is performed for the downlink if required by the link calculation flag. Depending on the

value of the downlink power calculation option, user-supplied values for spacecraft powers may be utilized or

calculated from downlink C/N values. Antenna discriminations are calculated (subroutines ESOFF, ANGLES,

and DISC) for the interfering spacecraft antenna toward the wanted earth station and the wanted earth station

toward the interfering spacecraft. The downlink C/I value is then evaluated and combined with the uplink C/I

value for the overall single-entry C/I achieved.

When evaluation of the achieved C/I values has been completed at a location, the compatibility matrix for the

location is made symmetric, using the results obtained by CICHK. Each entry of the compatibility matrix

corresponding to a row and column index is compared to its corresponding entry--that with the row and column

indices reversed. If the two entries both indicate compatibility, l's are present in the corresponding locations of

the compatibility matrix. If either or both of the compatibility matrix entries contains a 0, 0's are placed in both

corresponding locations of the compatibility matrix.

The compatibility matrix which results thus expresses in l's and O's whether any two service areas are

compatible at the particular location. The compatibility matrix is now symmetric; symmetry is required for the

enumeration of groups of compatible service areas at the current location. Diagonal entries will be set to 1, as

each service area is regarded as being compatible with itself (see figs. 3. l-6(d) to (f)). The symmetric

compatibility matrix may be regarded as a collection of vectors--one vector for each service area--which

expresses compatibility between that service area and all others. A compatible group consists of a set of service

areas whose members are each compatible with all other members. Affiliated sets of service areas are, once

again, treated in an all-or-nothing fashion; rows and columns of the compatibility matrix that correspond to single

service areas that are members of an affiliated set must be consolidated into a single row and column that

expresses the set's compatibilites with other nonmember service areas.

To enumerate groups of compatible service areas, each vector is examined in turn. Each vector has 1 in the

element corresponding to its own service area index, and additional 1's and O's indicating compatibilities with

other service areas. A complete list of compatible groupings for the current arc location is found by exhaustively

examining all possible compatibilities. When a large number of such groups, over several arc locations, have

been determined, the groups and arc locations are accumulated into a list of groupings and their associated group

arcs over which they have been found (subroutine ACCUM--see fig. 3.1-8). Finally, when all locations have

been exhausted, the list of grolJpings and arc spans is processed one final time in subroutine ACCUM to ensure

that the list contains all compatible groupings and the arc spans over which they may exist. This final list is

output by subroutine OUTLST to the NASARCI output file--the Groups file (see section 2.3.2.2) which is

utilized by the NASARC2 module as input.

3.1.5 NASARC2 Module

The function of NASARC2, the arc determination program, remains the same in Version 4.0 as in previous

versions. NASARC2 performs the following functions: (1) selects appropriate groups of service areas from an

exhaustive list of groups generated by NASARCI for a given portion of the orbit; (2) determines allotted arc

lengths for these selected groups; and (3) allots each selected group an arc segment within its group arc that is of

the appropriate size.

75
The major change to NASARC2 in Version 4.0 is that it has been modified to take advantage of the satellite

separation information available in the satellite separation matrix file during the group selection process. This file

contains the minimal satellite orbital separations needed between each pair of systems in the scenario such that a

specified single-entry C/I criterion is satisfied. These values are used to aid in selecting a critical group and

positioning the group in an allotted arc which improves the compatibility between satellites in adjacent arcs. This

selection process is described in more detail subsequently. What follows is an overview of the NASARC2 group

selection and arc determination procedures. The reader is referred to the NASARC2 flowcharts in figures

3. l-9(a) and 0a) throughout this description.

NASARC2 begins by reading in required input data as shown in the top portion of figure 3. l-9(a). This includes the

grouping criterion and arc length equation constants from the Input Parameters file (unit 12); the pairwise minimum

satellite orbital separations from the Separation Matrix file (unit 27); and the orbit segments that have been processed

thus far by NASARC1 from the Intermediate Segments file (unit 17). Using the segment information, NASARC2

determines the west and east bounds of the current cumulative arc, the west and east bounds of the current segment,

and the direction (east or west) in which the arc determination procedure will proceed. If the current segment

boundaries are eastward of the previous cumulative arc (in the last NASARC2 execution), the allotted arc buildup

occurs west-to-east. If the current segment boundaries are westward of the previous cumulative arc, allotted arc

buildup is east-to-west. This prevents large gaps from occurring between adjacent allotted groups. NASARC2

next reads the Groups and Service Arcs file (unit 20) to obtain the service areas for the current segment, their

service arc boundaries, the service area individual buffer arc sizes, the compatible groups generated by NASARCI

for the current segment and their respective group arc boundaries. Finally, if the current segment is not the first

segment to have been processed, then information related to groups which have been allotted in past segments

must also be read in along with any unallotted groups whose group arc adjoins an edge of the current segment.

The unallotted groups are then appended to the groups list from the Groups file and the group arcs of duplicate

groups are combined where appropriate to form a master groups list for the current cumulative arc.

The next major step in the NASARC2 procedure involves sorting the service areas into a priority order. Service

areas are partitioned into three classes, designated P1 (priority 1), P2 (priority 2), and P3 (priority 3), according

to the amount of contiguous service arc they have outside of the cumulative arc. P1 service areas have the

highest priority for inclusion in an allotted group. The amount of service arc they have that extends outside the

cumulative arc is no more than their transitional arc size. Therefore, almost all their service arc falls within the

present cumulative arc. It is important, then, that groups which contain P1 service areas be given the first chance

of being allotted in the present execution, since they will probably not appear in groups generated in subsequent

segments. P2 service areas have an amount of service arc outside the cumdative arc which is greater than their

transitional arc size but less than or equal to 20 °. They have medium priority. Finally, P3 service areas have

more than 20* of service arc outside the cumulative are. They have a low priority to be allotted in the current

segment since there is a good chance that they may be accommodated in later segments. After the service areas

have been classified into P1, P'2, and P3 classes, further sorting is done on the service areas within each class.

For each class, service areas are sorted in ascending order according to their frequency of occurrence within the

master groups list (i.e., the number of groups that the service area appears in). If two service areas have the

same frequency, then the service area that has the smaller service arc has priority. Thus, in the end, a service

area list is created in which the service area at the top of the list is considered to be the critical service area.

This means it has the highest priority (P1) and appears in the fewest number of groups of any of the service

areas represented in the current segment. Groups in the master list which contain this service area will be the

first ones considered for selection. Before compiling these critical groups, however, NASARC2 first checks to

see if any of the PI service areas are missing from the master groups list. If a PI service area is missing, the

program computes its arc length requirement using the service area's transitional arc and tries to allot the service

area an arc (equal to its computed arc length) within its service arc.

Once NASARC2 has sorted the service areas into the allotment priority described previously and taken care of

any missing P1 service areas, the program enters a loop and repeatedly performs the steps outlined below.

Iteration continues until either (1) all service areas in the present segment have been included in allotted groups,

(2) there are no more groups left in the master groups list, or (3) there is no more unoccupied arc left in the

current segment. The steps performed in the loop are as follows:

76
(1) Groups containing the current critical service area are collected from the master groups list.

(2) This subset of groups is prioritized to choose a critical group.

(3) An allotted arc length is computed for the critical group.

(4) NASARC2 tries to allot the critical group an arc segment within its group arc that is equal to the size

computed in step (3) and which is most compatible to neighboring allotted groups.

(5) If the group can be allotted, the master groups list is updated to reflect the most recent allotment.

(6) The next critical service area is found by recomputing the frequency of occurrence of each remaining service

area in the updated master groups list, and the steps are repeated.

A more detailed description of each step is presented in the following paragraphs.

Step (1) in the loop involves forming a sublist of groups from the master groups list. Each group in the sublist

contains the critical service area. For P2 and P3 critical service areas, a check is first done to see if there is

enough arc in the present segment for a two-member P2 group or a three-member P3 group, respectively. If

there is not, the allotment process for the present segment stops and the run ends. This is done to prevent

inefficient use of the arc by the allotment of large numbers of single P2 and two-member P3 groups. Once the

sublist of groups has been formed, processing is done within this sublist to extend the group arcs of groups

which are subsets of other groups. This is done in order to work with each group's total available group arc.

In step (2), the sublist groups are prioritized by performing a compound sort. The groups are first sorted

according to the number of service areas in each group so that the group with the largest number of service areas

appears at the top of the list. Then, groups with equal numbers of service areas are sorted so that the group with

the largest group arc length appears first. Finally, groups with equal group size and equal group arc length are

sorted so that the group with the smallest total frequency of occurrence is first. A group's total frequency of

occurrence is defined to be the sum of the frequencies of occurrence of its constituent members. Once the sublist

has been ordered in this way, the critical group is chosen as the first group in the list. The group transitional arc

size for this critical group is then determined as the largest individual transitional arc area buffer among its

constituent members.

In step (3), an allotted arc length is computed for the critical group as follows:

AL = C_,(N- 1),GRP + C2*T+ C3*N+ Ca

where

AL

c.c2,c3,c4

N

GRP

T

allotted arc length, deg

user specified constants from NASARC0

number of service areas in group

grouping criterion, deg

group transitional arc length, deg

The result is then rounded up to the nearest whole degree.

In step (4), NASARC2 tries to allot the critical group an arc segment within its group arc that is equal in size to

the value computed in step (3). The orbital separation values in the Satellite Separation Matrix file (unit 27) are

used in positioning the group within its group arc to improve the compatibility between satellites in adjacent

PDA's. In the positioning process, the critical group is moved along its group arc in 1" increments. At each

position, tests are performed to determine if an orbital slot of sufficient width (equal to the critical group's

computed arc length) exists to possibly accommodate the group or if such a slot can be opened by pushing

existing allotted groups within their respective group arcs (the relative west-to-east ordering of existing groups

77
remainsunchangedduringtheprocess). If aslotcannotbeopened,thenthecriticalgroupissimplystepped1"

furthereastward(orwestward)initsgrouparcandthetestsarerepeated. If a slotcanbeopened, thenthe

requiredseparationbetweenthecriticalgroupanditspotential eastandwestneighboringgroupsisdetermined

usingthevaluesin theseparationmatrixandthearclengthsof thecriticalgroupanditspotential neighbors.

Specifically, therequiredseparationbetweentwogroups(betweenthenearestedgesof theirallottedarcs)is

foundbytakingthedifferenceof theworst-case(largest)separationrequiredbetweenanypairof serviceareasin

thetwogroupsandtheavailableseparationthatcanbeachievedbyplacingthisworst-casepairof serviceareas

attheextremendsof theirrespectiveallottedarcs.Requiredseparationiscalculatedontheworst-case

assumptionthatthetwogroupsabutoneanother,althoughtheymay,infact,haveseveraldegreesof arcbetween

them.If therequiredseparationbetweenthecriticalgroupanditseastandwestneighborsisnegativeor zero

(i.e.,theavailableseparationisgreaterthanorequalto theworst-caseparation), thensatellitesof serviceareas

inthecriticalgroupwill experienceminimalinterferencefromneighboringsatellitesintheadjacent groupings.

Accordingly, for eachcriticalservicearea,NASARC2will attemptto selectthelargestcriticalgroupand

positionit betweenneighborswhereit hasminimalseparationrequirements. Furtherimprovement itheallotted

grouparrangement isaccomplishedintheNASARC4arcinterchangeprogram.

If anallotmentcanbemade,thenthecriticalgroupisrecordedasanallottedgroupanditsgrouparcboundaries

andallottedarcboundariesarealsorecorded. Executionthenproceedsto step(5).If anallotmentcannotbe

made,thenthecriticalserviceareaischeckedtoseeif it isasinglePI servicearea.If it is,thenit is listedas

anunallottableservicearea.If it is not,thenthenextgroupinthesublistof step(2)isdesignatedasthecritical

groupandexecutionproceedsfromthere.

In step(5),themastergroupslistisupdatedto reflecthecriticalgroupselectionbydeletingthecriticalgroup

membersfromallgroupsinthemasterlistinwhichtheyappear.Asa resultof thesedeletions, groupswhich

werepreviouslydifferentfromeachothermaynowbecomeduplicates, withtheirgrouparcsbeingadjacent or

overlappingin somecases.Hence,it is necessarytoexaminethelistandcombinethegrouparcsof these

duplicategroupswheretheyarecontiguousor overlapping. Lastly,becauseselectionof thenextcriticalservice

areaispartlybasedonfrequencyof occurrenceinthemasterlist,redundant groupsmustbeeliminatedfromthe

listinorderto maintaintheintegrityof theselectioncriterioninchoosingthetruecriticalservicearea.

Step(6)intheloopinvolvesfindingthenextcriticalserviceareabyrecomputingthefrequencyof occurrence of

each of the remaining service areas in the updated master groups list. Then, within each of the PI/P2/P3 priority

classes, service areas are sorted in ascending order: first with respect to frequency of occurrence, then with

respect to service arc length. The separate ordered PI/P2/P3 sublists are then appended to one another to form

the complete updated service area list. The service area at the top of the list is then chosen as the new critical

service area. Execution then proceeds back to step (1) and the entire process is repeated.

As mentioned before, NASARC2 stops when either all service areas in the present segment have been included in

allotted groups, there are no groups left in the master groups list, or there is no arc left in the current segment.

Before NASARC2 stops, however, it writes all allotted groups to the Intermediate Allotted Groups file (unit 21).

It also finds the unallotted groups in the master list (if there are any) that adjoin either edge of the cumulative arc

and writes them to the Unallotted Groups file (unit 22). Control then passes to the NASARC3 module.

3.1.6 NASARC3 Module

The NASARC3 module--the group arc extension program--examines groups of systems that have received

allotted arcs through the arc determination process (NASARC2 module) in order to determine if their group arcs

may be extended further in the orbital arc. This operation is performed to retain as much flexibility as possible in

the arc determination process as applied to all segments of the orbit; that is, should adjustment of prior allotted

arcs become necessary in order to accomodate newly allotted arcs, the full group arc will be available for the

adjustment.

When a group of compatible systems has been selected by NASARC2 to receive an allotted arc, the NASARC2

module will examine the arc span over which the group has been found to exist--the group arc--and will select a

78
suitableportionof the group arc to become the group's allotted arc. As stated previously, it may become

necessary to revise prior allotted arcs by moving them from their original locations in order to accommodate

additional allotted arcs. However, a revised allotted arc for a compatible group of systems must still lie within

that group's group arc. For this reason, the full extent of each group arc into the remainder of the orbit to be

analyzed must be determined.

Group arc extension is accomplished by the NASARC3 module in much the same way that group arcs are

determined by the NASARC1 module; however, the computational effort required is considerably less. In

NASARCI, all possible compatible groups of systems, and their group arcs, are found within the segment

currently being examined; in NASARC3, the group arc that exists for known, previously selected groups of

systems is determined over the full extent of the remaining orbital arc. Thus, analysis of compatibility is

restricted to a small, known set of service areas.

The NASARC3 module first collects needed information from the Input Data file (see section 2.3.1.6_: as in

NASARCI, various operations of the program are affected by data within this file--such as treatment of affihated

sets of service areas. If affiliated sets of service areas are to be considered, the Affiliated Sets file (see scctio.:_

2.3.1.5) is read and processed by NASARC3 (see fig. 3.1-12(a)).

A group of service areas and its group arc are retrieved from the Intermediate Allotted Groupings file (see

section 2.3.2.3). The group is checked to determine if its group arc has been previously extended, which is

indicated by a flag at the end of the group's record. If the flag indicates that the group's group arc has already

been extended, the NASARC3 module returns to the Intermediate Allotted Groupings file to obtain and check the

next group and group arc. If the flag indicates otherwise, the program attempts to extend the group arc in

question. When all groups have been exhausted, the Intermediate Allotted Groupings file is updated (if necessary)

and the program terminates.

If group arc extension has not yet taken place for a particular group, the NASARC3 module extracts information

about the service areas contained in the group from the Service Area file (see section 2.3.1.3). The service arcs

of the service areas are then intersected; if the intersection is not sufficient to provide room for further expansion

of the group arc, NASARC3 retrieves the next group from the Intermediate Allotted Groupings file. If the

intersection is sufficient, then group arc extension is feasible.

If group arc extension is feasible for the group of service areas in question, polygon points for the appropriate

service areas are extracted from the Point Sets file (subroutines POSPAR, RDPTS). As in NASARC1, if point

sets are not found for all service areas, error flags and error messages are written to the appropriate locations

(subroutine ERR), and the program ceases execution. If point set data are collected successfully, ellipse data are

then extracted from the Ellipse file (see section 2.3.1.8). Once again, if the data cannot be successfully extracted.

subroutine ERR is called and the NASARC3 module stops (see figs. 3.1-11Co)).

The initial arc location is set to the appropriate western or eastern longitudinal limit of the existing group arc;

this arc location is incremented if expansion of the group arc is to take place in a west-to-east direction or

decremented if expansion is in an east-to-west direction. Expansion is attempted in both directions.

Over the remainder of the orbital arc, pairwise compatibility between service areas is assessed for each pair of

service areas within the current group whose arc is to be extended as in NASARCI (subroutine CICHK). At each

discrete arc location where compatibility between all service areas within the group still holds, the appropriate

group arc boundary is adjusted to encompass the new location where the compatible grouping continues to exist.

When the group of service areas no longer continues to be compatible, or the intersected service arc has been

completely examined for group arc extention, the next compatible group to be examined is taken from the

Intermediate Allotted Groupings file (see figs. 3.11 (a), (d), and (e)).

When all groups and group arcs in the Intermediate Allotted Groupings file have been examined for possible

extension, the Intermediate Allotted Groupings file will be updated to reflect the revised group arcs (see fig.

3.1-1 l(a)). When this operation has been performed, the NASARC3 module concludes operation.

79
3.1.7 NASARC4 Module

The NASARC4 module is the arc interchange program. NASARC4 seeks to improve the most current

arrangement of allotted arcs in orbit through a heuristic swapping procedure. Like NASARCI, NASARC2, and

NASARC3, the NASARC4 module is applied within each segment of the orbital arc specified by the user in the

Segments file. Thus, in each segment, NASARC4 seeks to improve the arrangement of arcs derived from use of

the NASARC modules during all segments of the orbit up to and including the segment currently being

processed.

The NASARC software package utilizes heuristic algorithms to produce a collection of allotted arcs, each shared

by a group of compatible satellite systems. Systems are compatible if their service areas are sufficiently

geographically separated to allow achievement of a required single-entry (pairwise) C/I with relatively little ( l °

or less) orbital separation between satellites. Within each allotted arc, satellites have a high degree of flexibility

in positioning due to minimal intersatellite spacing requirements.

However, when several allotted arcs are placed adjacent to one another in orbit, flexibility in positioning within a

given arc may be reduced if a system in an adjacent arc is highly incompatible. In other words, a satellite within

a given arc may have its flexibility in positioning limited by the need to maintain a large orbital separation from

a system in an adjacent arc. Thus, while satellites within a given allotted arc are compatible, satellites grouped in

different segments are incompatible. Some arrangements of allotted arcs in orbit are thus less beneficial than

other arrangements in terms of both flexibility in positioning and aggregate C/Fs achieved for individual systems

within allotted arcs.

For this reason, an additional module was developed for the NASARC (Version 4.0) software package. This

module--NASARC4--is de,signed to improve the arrangement of allotted arcs in orbit produced by NASARC2 by

placing more compatible allotted arcs in adjacent portions of the orbital arc.

The user will recall from section 3.1.5 that NASARC2 produces an arrangement of allotted arcs in orbit. This

arrangement is treated as an initial arrangement by the NASARC4 module. NASARC4 seeks to improve the

arrangement of allotted arcs in orbit via an heuristic swapping procedure which has proven to be both effective

and computationally efficient.

The degree of incompatibility experienced by each allotted arc, with respect to its neighboring allotted arcs, can

be evaluated by summing the incompatibility contributions presented by the arcs immediately adjacent to the west

and east of the allotted arc in question. The incompatibility is evaluated as the normalized orbital separation

required between systems in adjacent arcs as follows:

M N

i=I j=l

Ex (or Wx) -

MN

where

M number of systems in allotted arc K

N number of systems in K+ 1 or K- 1

s,j orbital separation required between system i and j

NASARC4 seeks improvement in n objectives for n allotted arcs, i.e.,

Minimize IK = Ex + Wx K= 1..... n

While the objectives described provide a measure of each allotted arc's compatibility with its immediate

neighbors, they do not account for situations where two allotted arcs are not adjacent but may still have

insufficient orbital separation. To assess the separation required between all pairs of allotted arcs, the worst-case

80
orbital separation between any two systems in a pair of arcs is found. Since we wish to evaluate the orbital

separation that is desired between the closest endpoints of the pair of allotted arcs, we must first determine the

separation that may be achieved betwen the two most incompatible systems if the arc were immediately adjacent

The available separation is calculated as follows:

Aij = Ri + Rj - T

where

Aij available separation between worst-case pair of systems in allotted arcs i and j

Ri arc length of allotted arc i

Rj arc length of allotted arc j

T transitional arc length

If the available separation is greater than or equal to the worst-case separation required, no additional separation

is required between the closest endpoints of the allotted arcs. If, however, the available separation is not

sufficient, the difference between the worst-ease separation required and the available separation represents the

additional separation that is sought between the endpoints of the allotted arcs.

As stated earlier, the original arrangement of allotted arcs in orbit, as derived by NASARC2, is rearranged and

improved by NASARC4 via a heuristic swapping procedure. That is, pairs of allotted arcs are interchanged to

occupy different arc segments than they did originally in an attempt to place more compatible allotted arcs in

adjacent portions of the orbit.

To perform such interchanges, NASARC4 first determines a complete list of all arc interchanges that are

feasible. For an interchange of allotted arcs to be feasible, the two allotted arcs must meet the following

conditions:

(1) The group arcs associated with each allotted arc must intersect by at least the sum of the required arc lengths

for each allotted arc.

(2) The intersection of the group arcs associated with each allotted arc must encompass both allotted arc

locations.

Condition (I) restricts consideration of alternatives to meaningful alternatives; if condition (1) is not met b_ two

allotted arcs, the two segments are restricted to portions of the orbit that are sufficiently distant to imply that the

appropriate service area cannot be served by the appropriate satellites if the locations of the allotted arcs were to

be interchanged. Condition (2) ensures that slots in the arrangrnent may be directly interchanged, subject to minor

adjustments for slightly different length requirements for the two segments.

When a complete list of feasible interchanges has been assembled and stored in a matrix (subroutine FEASIN),

NASARC4 begins the improvement process. The improvement process has three major phases:

(1) Generation of an improved starting arrangement

(2) Generation of the best alternative arrangement over all possible interchanges

(3) Spreading of the allotted arc arrangement found in phase (2) to achieve the necessary separation between

endpoints of allotted arcs

To generate an improved starting arrangement, the matrix of feasible interchanges is examined for pairs of

elements that may be interchanged only with each other. Such elements are termed pair-restricted. If these

interchanges result in an improvement of the arrangement's objective function values, they may be performed

without affecting the outcome of any other interchanges. When all such pairs have been found and interchanged,

NASARC4 has an improved starting arrangement. As the pair-restricted interchanges need no longer be

81
considered, theyareeliminatedfromthe matrix of feasible interchanges, which are then used to generate

arrangements that improve further on the starting solution. If no pair-restricted interchanges exist, the starting

arrangement is that derived by the NASARC2 module.

The search for the best alternative over all possible interchanges begins with a reexamination of the matrix of

feasible interchanges. When an arc with one or more candidate interchanges has been found, alternative

arrangements of allotted arcs are generated (subroutine SWAP). The basic arrangement--initiaily, our starting

arrangement found in phase (D--is held constant. Alternatives to the basic arrangement are generated by

examining all possible interchanges for each allotted arc. Each interchange is examined for efficiency--i.e.,

improvement of the objective functions of the basic arrangement. If an interchange produces an efficient

alternative arrangement, the new alternative is then compared with the current best alternative to determine which

alternative is preferred. Preference of one arrangement over another is measured, first, by counting both the

number of allotted arcs for which the first alternative's objective values are lower than the corresponding values

for the second alternative, and vice versa. The alternative with the greater number of lower objective values is

preferred. If, however, a tie results, the average objective function value is calculated for each alternative; the

arrangement with the lower average objective is preferred. Finally, in the unlikely event that both alternatives

have the same average objective value, the current best alternative is retained.

During the process just described, the basic arrangement is held constant. When all alternatives reachable from

the current basic alternative have been examined, the basic alternative is replaced by the best alternative found

over all interchanges. The process of generating new alternatives begins again with the new basic alternative. The

matrix of feasible interchanges is regenerated (subroutine FEASIN) to account for the effects of changes in

allotted arc locations. When no further improvement of the current basic alternative is possible, no further

alternatives are generated and phase (2) is concluded.

Phase (3) of the arc rearrangement process attempts to spread the allottod arc segments, as ordered by phase (2),

further apart if needed. Additional separation requirements consist of orbital spacings necessary between the nearest

endpoints of allotted arc segments. In the majority of cases, no orbital separation is required between allotted arcs; in

other cases, the required distance between allotted arcs is acquired through the swapping process of phase (2).

Phase (3) attempts to provide further required separation between both adjacent and nonadjacent allotted arc

segments by pushing allotted arcs in an east-to-west direction (subroutine TEMPOR). This process is nearly

identical to the pushing operation of NASARC2 and is not discussed in further detail here. The operations differ

in that while NASARC2 attempts to create an unoccupied orbital segment of a single specified length NASARC4

first attempts to obtain the full separation still needed between allotted arcs; if this separation cannot be obtained,

successive reductions of the required separation take place until the maximum obtainable separation is achieved.

When all phases of the improvement process are completed, the new orbital locations are output to the

Intermediate Allotted Groupings file originally produced by NASARC2.

When all segments of orbital arc specified within the Segments file have been processed, the NASARC4 module

produces the NASARC Report file (subroutine REPORT) and the Condensed Report file (subroutine CNDREP).

Flowcharts of the NASARC4 module and selected subroutines are presented in figures 3.1-12(a) to (g), 3.l-13(a)

and (b), and 3.1-14(a) to (c), respectively.

3.2 Creation of NASARC (Version 4.0) Input Files

In this section details are given on the preparation of data for files input to the NASARC modules. The user will

recall that detailed discussions of the structures and formats of the Segments file, the Service Area file, the Point

Sets file, the Affiliated Sets file, the Input Data file, and the Ellipse file were given in sections 2.3.1.1 and

2.3.1.3 to 2.3.1.6; the user is urged to refer to these sections for information on the specific format for the data

the user wishes to input. This section is concerned with the derivation of data for input to the NASARC software

package and with the transformation of the data into a form compatible with the formats described in section 2.3;

the user is also urged to refer to the NASARC (Version 4.0) Technical Manual for conceptual discussion of

material presented in this section.

82
3.2.1 Segments File Data

As was stated in section 2.3.1.1, the NASARC (Version 4.0) software package is designed to apply the

NASARCI, NASARC2, NASARC3, and NASARC4 modules in sequential fashion to successive portions of the

orbital arc defined by the user within the Segments file.

Segments to be examined by NASARC1, NASARC2, NASARC3, and NASARC4 must be specified in the

format presented in section 2.3.1.1. The only restriction on ordering records within the Segments file is that

following the first record all subsequent records must adjoin either the eastern or western boundary of the

cumulative arc segment defined by preceding records. A segment adjoins a prior segment if the western and

eastern arc limits or eastern and western arc limits, respectively, differ by exactly 1*. As may be inferred from

the preceding statement, no two segments specified within the Segments file may overlap--that is, encompass any

of the same orbital locations.

The segments to be examined by the NASARC1, NASARC2, NASARC3, and NASARC4 modules are defined

by longitudinal limits expressed in decimal degrees. In each record, the western longitudinal limit of the segment

to be examined must be followed by the eastern longitudinal limit. Such longitudes must be in the range

(-179.00", 180.00"); should a segment cross the 180" meridian, the western longitudinal limit is numericall2,

greater than the eastern longitudinal limit. Thus, it is possible that a segment described within the Segments file

has a positive (greater than or equal to 0.0) western limit and a negative eastern limit. It is also possible (if a

large portion of the orbit is used) that both limits are negative but that the western limit is less negative than the

eastern limit.

Each set of segment limits is also accompanied by a grouping criterion value to be applied within that portion of

the orbital arc. As stated earlier, the grouping criterion expresses, in degrees of orbital arc, the maximal orbital

separation that may be required between two systems for the systems to be considered compatible.

While all sets of segments specified according to the previous guidelines are valid, the most effective and

efficient use of the NASARC (Version 4.0) software package is achieved if the segments to be analyzed, and

their associated grouping criterion, are selected in a strategic manner. The primary goal of the piecewise

approach to allotting orbital arcs is to reduce memory requirements and run time needed for execution of the

overall software package while obtaining useful allotted arcs for all service areas considered. This goal may be

achieved by attempting to equalize the number of service areas to be considered within each segment of the

orbital arc and by adjusting the grouping criterion to make grouping of systems either more likely or less likely.

Figure 3.2-1 presents a graph of the number of service areas whose service arcs encompass an orbital location

(longitude) versus orbital location (longitude). From the figure, we see that there is a portion of the orbital arc--

extending from approximately - 10" east longitude to 40* east longitude--that contains the area of peak density

of service arcs for service areas. However, many service areas whose service arcs intersect the peak-density

portion of the orbit have service arcs that include significant portions of arc that fall outside the peak-density

segment. If allotted arcs can be obtained for these service areas in portions of the orbit outside the peak-density

area, the number of service areas that must be considered for the peak-density portion of the orbit can be

reduced--requiring less computer time and memory for use of the NASARC modules on this portion of the orbit.

After consideration of the previous discussion, it should be clear to the user that it is desirable to begin use of

the software package in a low-density portion of the orbital arc. It is not necessarily more advantageous,

however, to begin with the portion of the orbit which encompasses the lowest density of service arcs. The user

must keep in mind that the goal is to equalize the number of service areas examined within each segment of the

arc. Thus, the most effective approach may be to begin with a portion of the orbit to the east or west of the peak

area and progress through areas of lower density using larger segments of arc until all the segments that the user

wishes to examine have been considered. Alternatively, the user might choose a large segment of arc

encompassing low-density areas of the curve and alternate segments of arc to the east or west of the original

segment in approaching the peak-density portion of the orbit. It is difficult to quantify a precise recipe for

selecting the segments to be analyzed and the order in which to analyze them; the user will quickly learn from

his own experience which approaches are suited to particular sets of circumstances.

83
0

I

0

SD}IV ._DIA}J_S _IO _IS_M_IN

C  ̧

o

c

o

0

o

d

o

o

O0

I

o _

Z

0

O

d

_0

I

o

IL

o

d

I

o

d

I
It is also difficult to present a precise recipe for selecting a grouping

criterion to be applied within each segment. The purpose of applying a

separate grouping criterion value for each segment is to allow the user to 120.00 -12 ¢_

influence the number of compatible groupings in a particular segment. This 80.00 119

ability is particularly useful if a NASARC run results in an unallotted 60.00 79 -125.00 -55

administration within a particular segment; the grouping criterion for this -5_. 00 -28

segment could be adjusted to a higher value to make accommodation of the _ 5.00 59

administration within a compatible group more likely. Once again, the user -27.00 0

1.00 c¢_

will learn from experience what combinations of segments and grouping

criteria are suited to his particular scenario. An example Segments file (see

fig. 3.2-2) may help to illustrate the discussion presented in this section.

FILEt INITIAL SEGMNTS AI

O0 1.000

O0 0.750

O0 0.750

O0 0.500

O0 0.750

O0 0.750

00 0.750

O0 1.000

Figure 3.2-2 --Segments file

3.2.2 Service Area Data

Data in the Service Area file, as discussed in section 2.3.1.3, have a variety of functions. First and foremost, the

data in the Service Area file establish a complete list of service areas to be examined for arc determination within

the segments defined by the user along with service arc limits for each area. Each record of the file also contains

data that are applied to the individual service area in question. The required inputs are described in subsequent

sections; details of their format appear in section 2.3.1.3. Prior to the data for individual service areas, however.

the file contains a single record with global data to be applied to the entire scenario.

3.2.2.1 Global Data

As discussed in section 2.3.1.2, the Service Area contains, in its first record, global data that are to be applied to

the entire scenario described by the Service Area file. These inputs are described in the following sections.

3.2.2.1.1 Rain Attenuation Flag

The rain attenuation flag is a single character code that indicates whether or not rain attenuation is to be includcd in

C/I calculations. If the flag is set to Y (yes), rain attenuation is added to the power calculated from the C/N value.

If a user-supplied power value is to be utilized, that value is assumed to be sufficiently high to include

compensation for rain fade. If the flag is set to N (no), all calculations are performed on a clear-sky basis.

Further discussion on the use of rain attenuation in C/I calculations is provided in the NASARC ( Version 4.0)

Technical Manual.

3.2.2.1.2 Minimum Half-Power Beamwidth of Satellite Antenna

The minimum half-power beamwidth of the satellite antenna serves two purposes. As ellipses are read from the

Ellipse file, those having major and/or minor axis beamwidths less than this minimum value are adjusted so that the

minimum value is satisfied. In addition, the minimum half-power beamwidth is utilized within the fast rolloff

antenna patterns--where the gain for any size beam falls off at the same rate as for the minimum size beam.

The minimum half-power beamwidth for the satellite antenna is interpreted as the entire half-power beamwidth,

from edge-to-edge of coverage, rather than from center to edge. All calculations within the NASARC programs

involving satellite half-power beamwidth interpret the beamwidth in this way.

It is suggested the user calculate a minimum beamwidth that is suitable for the chosen frequency and a reasonable

physical size for the satellite antenna. As an example, a minimum beamwidth of 1.4" would correspond to a

satellite antenna diameter of 3.3 m operating at a frequency of 4.50 GHz. Values of 0.8* and 1.6" have been

suggested for allotment planning in the Fixed Satellite Service.

_5
3.2.2.1.3 Constants for Allotted Arc Equation

The four constants contained within the first record of the Service Area file are used to calculate the length of the

allotted arc to be given to a particular group of compatible systems. The allotted arc length is determined in the

NASARC2 module as follows:

AL = Ct,(N- I).GRP + C2,T + C3,N+ (?4 (3.2-1)

where

c,,c2,c3,c4

AL

N

GRP

T

constants specified within first line of Service Area file

allotted arc length

number of compatible service areas contained in group

user-supplied grouping criterion, deg

calculated group transitional axe length, deg (see NASARC Technical Manual)

Equation (3.2-1) shows that it is not desirable to set all con,_ants Ct, C,,z, C3, and C4 equal to 0.0 as this would

result in an allotted arc length of 0". For this reason, an error message is generated by the NASARC0 module

during verification of user input files if Cj -- C2 = C3 = C4 = 0.0 exists within the Service Area file.

The user will observe that equation (3.2-1) allows for weighting the factors to be taken into account when

calculating the allotted arc length. For instance, the user might have selected 0.0" (colocation) for the value of the

grouping criterion GRP. In this situation, the user would be well advised to include provision in the equation to

adjust the value of the allotted arc length for the number of compatible service areas involved. Thus, the user

would wish to provide a nonzero value for the constant Ca. A variety of other situations may be taken into account

in a similar manner.

The user is strongly advised to consult the NASARC (Version 4.0) Technical Manual (section 3.3.4.2) before

experimenting with values for C_, (?2, Cj, and (?4.

3.2.2.1.4 Reference Noise Bandwidth

The reference noise bandwidth is used to present a noise bandwidth that an input C/N may be referenced to.

Typically, this input has a value of 1 MHz. The reference noise bandwidth must be included in the calculation of

power from the input C/N value.

3.2.2.1.5 Minimum Earth Station and Satellite Power

Minimum earth station and satellite power limits may be used to set a lower bound for transmitter power levels for

all systems. Power levels are either calculated, based on the C/N criteria, or taken directly from input values, as

required by power calculation options, and compared against the appropriate lower power limit. The maximum of

the two values is utilized in C/I calculations. This feature is provided as a means of reducing power

inhomogeneities between systems.

Further information on the use of these values is provided in the NASARC ( Version 4.0) Technical Manual.

3.2.2.2 Service Area Data

As stated in section 2.3.1.3, the Service Area file utilized by NASARC modules contains a list of service areas and

the western and eastern longitudinal limits of the service arc associated with each. Each service area is

86
symbolizedbyathree-character serviceareacode.It ismostconvenient to usethedesignations utilizedbythe

International Telecommunication Union(ITU);however, anyITUdesignationcontaininglessthanthreecharacters

mustbepaddedwith0"sforproperprocessingbytheNASARCmodules. Westernandeasternlimitsof each

servicearea'sassociatedarcareexpressedinintegraldecimal degreesof eastlongitude,rangingfrom-179.00"to

180.00".Theselimitscorrespondtothelimitsof aservicearea'sservicearcfortheelevationangledesiredbythe

user.However,it mustberemembered thathigh-latitudeserviceareasmayhavenarrowor nonexistent sepdcearcs

forhighelevationangles.It issuggestedthat,in suchcases,theuserchoosetheelevationanglethatproducesa

servicearclengthof atleast30"whenavailable. Thiswillgreatlyincreasethelikelihoodof findingcompatible

groupscontainingtheserviceareainquestionandof allottinganarctothatservicearea.Forprecisedetailofa

suggestedservicearcdeterminationmethodtheuserisreferredto section3.1.1.5of theNASARC (Version 4.0)

Technical Manual.

Within the Service Area file, records for service areas must be placed in an order that maintains consistency with

the Ellipse file that is to be used with the NASARC (Version 4.0) software package.

3.2.2.3 Additional Service Area Data

As discussed in section 2.3.1.3, specification of additional service arca data depends on the precise situation the

user wishes to examine with the NASARC (Version 4.0) software package: the inputs have a variety of purposes

described in the following sections. The user is also referred to the NASARC (Version 4.0) Technical Mamml fi_r a

detailed discussion related to these inputs: the data items are described m subsequent sections in the order in which

they appear following the data entries described in section 3.2.2.2.

3.2.2.3.1 Set Affiliation Code Data

The set affiliation code is an integer which indicates that a service area is to be included in an affiliated set of

service areas. The user will recall that an affiliated set of service areas consists of geographically dispersed areas

that are to be served from a single satellite. By placing the same numeric code in the records of several service

areas, the user indicates that the service areas are all members of the same set. Service areas with nonidentical

codes are not considered to be members of the same set. If no code is specified, or the code specified is equal to

zero, the service area is regarded as independent--that is, not a member of any set.

Integer codes utilized to express set affiliation must correspond with numeric codes in the Affiliated Sets file--that

is, no code (other than zero or blank) should appear in the Service Area file unless that code also appears in the

Affiliated Sets file. Codes utilized in both files should follow the sequence I, 2 ..... etc.; that is, 3 should not be

utilized as a set affiliation code unless 1 and 2 have already been utilized to designate other affiliated set members.

Finally, the number of service area records containing a particular set affiliation code should correspond to the

number of members identified for the appropriate affiliated set in the Affiliated Sets file.

For further discussion of the concept of affiliated sets the user is referred to the NASARC (Version 4.0) Technical

Manual.

3.2.2.3.2 Space Station and Earth Station Characteristic Data

Section 2.3.1.3 states that space station characteristics are specified individually fi_r each service area. These

characteristics are described by five inputs--the space station antenna pattern code, the space station antenna

parameter, the space station antenna, the space station receiver noise tempcrature, and satellite transmitter powcr.

The format for specifying these items is given in section 2.3.1.3.

Similarly, earth station characteristics are specified individually for each service area. Earth station characteristics

are described by seven inputs--in this case, the earth station transmit antenna pattern code, the earth station

87
transmitantennadiameter(expressed in meters), the earth station receive antenna pattern code, the receivc antenna

diameter, the earth station antenna efficiency, the earth station receiver noise temperature, and the earth statism

transmitter p_wer. The fornlat for specifying these items is given in section 2.3.1.3.

-Xntcnna efficiencies are always expressed as decimal percentages--that is, 55-percent efficiency is expressed a_

0.55. Thus, any antenna efficiency specified must be greater than or equal to 0.0 and less than or equal to 1.0,

Antenna efficiency for space station and earth station antennas is expressed in this manner regardless of the antenna

pattern type and antenna parameter value otherwise specified.

The user may select a space station antenna pattern type from a collection of patterns implemented within the

NASARC programs; once a six-character pattern code has been selected, the user need specify at most one

additional space station antenna parameter value in order to fully describe the desired antennas.

The eleven types of space station antennas available in the NASARC (Version 4.0) software package, and their

associated six-character codes, are as follows:

SCA558

RARCST

RARCFR

FASTRO

ORBIT()

ORBITF

WARC77

IW4/1

IWPREV

JIWPRF

JIWPRV

Satellite antenna pattern presented in CCIR Report 558-3

Standard rolloff satellite antenna pattern given in RARC-83 Final Acts

Fast rolloff satellite antenna pattern given in RARC-83 Final Acts

Improved fast rolloff satellite antenna pattern presented in Document No. AH-178-296 of the

lnterdeparcmental Radio Advisory Committee

Satellite antenna pattern utilized in ORBIT-II synthesis program developed by Kokusai Denshin Denwa

of Japan

ORB1T-II satellite antenna pattern with a -10 dB floor added for use in NASARC

Satellite antenna pattern given in the WARC-77 Final Acts

Fast rolloff satellite antenna pattern presented in CCIR Report 558-3 and recommended by IWP4/I

(June 1986)

Similar to IWP4/I, but utilizing simple ellipse as main beam

Fast rolloff satellite antenna pattern presented in the CCIR Report to Second Session of the Space

World Administrative Radio Conference (WARC-88) (December 1987)

Similar to JIWPFR, but utilizing simple ellipse as main beam

The user may select from three earth station antenna patterns implemented within the NASARC (Version 4.0)

software. The three patterns available are the following:

ETA391

ETAIMP

I_TACOM

Earth station antenna pattern presented in CCIR Report 391-4 with 32-25 log (,p) characteristic

Earth station antenna pattern presented in CCIR Rep_rl 391-4 with 29-25 log tip) characteristic

Earth station antenna pattern, combining features of ETA391 and ETAIMP

The associated input parameters related to each of the antenna patterns are given in table 3.2-1; the corresponding

falloff equations are given in the NASARC (Version 4.0) Technical Manual in section 3.1. ! .2.4. Satellite and earth

station receiver noise temperatures (expressed in dB-K) are also specified for each service area's system. Satellite

and earth station transmitter powers (expressed in dBW) are specified for each service area's system. These values

are utilized unless the user specifies that the powers are to be calculated to meet a target uplink or downlink C/N.

The user is referred to section 3.2.2.3.5 herein for information on power calculation options.

88
TABLE 3.2-I--ANTENNA PATTERNS AND

ASSOCIATED INPUT PARAMETERS

Antenna code Associated input Typical range Technical Manual

parameter of values reference section

ETA391

ETAIMP

ETACOM

SCA558

RARCST

RARCFR

FASTRO

ORBIT0

ORBITF

WARC77

IWP4/I

IWPREV

J1WPFR

JIWPRV

Antenna diameter

Antenna diameter

Antenna diameter

Falloff to first

sidelob¢ level

None required

None required

None required

Decay constant, ot

Decay constant, ct

None required

Falloff to first

sidelobe level

Falloff to first

sideiobe level

Focal length It)

diameter ratio

Focal length to

diameter ratio

3.0 to 10.0 m

3.0 to 10.0 m

3.0 to 10.0 m

20.0 to 30.0 dB

3.5 to 5.5

3.5 to 5.5

20.0 to 30.0 dB

20.0 to 30.0 dB

0.73 to 1.3

0.73 to 1.3

3.1.1.2.4.1

3.1.1.2.4.2

3.1.1.2,4.3

3.1.1.2.4.4

3.1.1.2.4.5

3.1.1.2.4.6

3.1.1.2.4.7

3.1.1.2.4.8

3.1.1.2.4.9

3.1.1.2.4.10

3.1.1.2.4.11

3.1.1.2.4.12

3.1.1.2.4.13

3.1.1.2.4.14

3.2.2.3.3 Uplink and Downlink Carder to Noise Ratios

Target uplink and/or downlink C/N's may be included for each service area's system. As was briefly discussed in

section 3.2.2.3.2, satellite and/or earth station power may be supplied by the user or it may be calculated as that

power necessary to achieve a target C/N value. Thus, the uplink and downlink C/N values are intended as criterion

values that must be achieved with appropriate power levels. The C/N criteria are expressed in decibels per

megahertz (dB/MHz). Further information on power calculation options is provided in section 3.2.2.3.5 herein.

3.2.2.3.4 Aggregate Carrier to Interference Ratio

The aggregate C/I is also specified as a criterion value for each service area's system. However, unlike the target

C/N values described in the previous section, the aggregate C/1 criterion is not utilized directly by major

calculations in NASARC. As stated previously, NASARC determines compatibility between systems based on the

slngle-entry C/I achieved at the orbital spacing between satellites specified by the grouping criterion. The aggregate

C/I criterion is used to determine the single-entry C/I criterion to be achieved as follows:

C/lsingle entry= C/[aggregat e -I- RATIO

where RAT/O is the margin of difference necessary to achieve an aggregate C/1, given a single-entry C/I (in dB).

Program variable RAT/O is currently set within the NASARC modules to a value of 6 dB. Thus, for example,

Version 4.0 of the NASARC software assumes that a target aggregate C/I value of 26 dB will be achieved for a

system if single-entry C/I calculations are performed on the basis of a 32-dB criterion.

89
3.2,2.3.5 Uplink and Downlink Power Calculation Flags

The uplink and downlink power calculation flags provide the user with the capability to specify, for each system,

the bases on which both satellite and earth station powers are included in calculations of effective isotropically

radiated power (EIRP).

Two options are available for both the uplink and the downlink. The user's choice in each case is indicated

numerically with a single-digit specification. If the user selects option 1, the power utilized in the EIRP calculation

is the value that the user supplies in specifying space station and earth station characteristics. If the user selects

option 2, the appropriate power value is first calculated from the user's specified target uplink or downlink C/N

ratio (see section 3.2.2.3.3 herein), and other values, as follows:

P = C/N- Gt + L + B + k - Gr/T + R

where

C/N

L

B

k

G,

T

G,

R

link carrier to noise ratio

free space loss on desired path

noise bandwidth in specifying C/N

Boltzmann's constant

on-axis gain of wanted receive antenna

noise temperature of wanted receive antenna

on-axis gain of transmit antenna

link ram attenuation compensation

Since two options are available for both the uplink and downlink, four combinations of options are available to the

user. For example, the user may specify use of a supplied transmit power value for the uplink and calculation of

power from the target C/N value for the downlink. Thus, the specification of power calculation options for the

uplink and downlink are independent of one another.

3.2.2.3.6 Existing System Flag

The existing system flag is of limited application, but it can affect how compatibility assessment takes place. This

single-character flag allows the user to indicate whether or not a given service area's system is an existing system

(indicated by a Y) or a planned system (indicated by an N). Originally, this flag was incorporated as an input to

allow the NASARC software to properly accommodate existing systems as defined for purposes of allotment

planning at the 1988 World Administrative Radio Conference. However, an explanation of this option is provided

herein in the event that the user may have an alternative application for the NASARC software for which this

option is appropriate.

The existing system option affects compatibility assessment for the system in question with all other systems. If the

system in question is designated as an existing system, it is regarded as being automatically compatible with other

systems also designated as existing. That is, the usual evaluation of the single-entry C/I value achieved at the

grouping criterion orbital spacing is suppressed. In all other cases--where one or both systems of the pair being

examined for compatibility are designated as planned rather than existing--compatibility assessment takes place as

usual, unless it is suppressed by some other factor such as service area affiliation.

3.2.2.3.7 Link Calculation Flag

Like the existing system flag, the link calculation flag is also of limited application, and also affects compatibility

assessments involving the system in question. The link calculation flag allows the user to specify, via a single9o
character option, whether the system is to be considered on an uplink-only basis (indicated by a U), downlink only

basis (indicated by a D), or on the basis of both uplink and downlink (indicated by a B).

In compatibility assessment, pairs of systems in which one system is uplink only and one system is downlink only

are regarded as automatically compatible. For all other combinations, compatibility is assessed in the usual manner

3.2.3 Point Sets File Data

In order for the NASARC modules to run successfully, the Point Sets file must contain (at minimum) a set of

polygon points for each service area included in the Service Area file. Up to ten such points may be specified f-r

each service area; the points should define a convex polygon of latitude-longitude pairs that closely approximatc._

the geographical boundary of the service area. Generally, a good representation may be obtained with ten or l'ex_cr

points. The data that the user must provide, if constructing a point set for a given service area, are listed and

described in table 2.2-3.

Precise format requirements for this type of data are given in section 2.3.1.4.

3.2.4 Affiliated Sets Data

The Affiliated Sets file, described in section 2.3.1.5, contains an integer numeric code, a three-character code. and

the number of member service areas for each affiliated set of service areas to be examined by the NASARC

modules. The user will recall that an affiliated set of service areas consists of a collection of geographically

dispersed service areas that are to be served from a single spacecraft.

Each item of data furnished for each affiliated set of service areas has a specific purpose. The user will recall from

the discussion presented in section 3.2.2.3.1 that each service area within the Service Area file may be assigned an

integer numeric code indicating membership in an affiliated set of service areas. The integer numeric code provided

for each affiliated set within the affiliated sets file provides a link between each affiliated set and its member

service areas; thus, the numeric code supplied for each affiliated set within the Affiliated Sets file must match the

numeric code in number of records of member service areas within the Service Area file. Codes utilized should

follow the sequence 1, 2 ..... etc.; that is, the first affiliated set represented within the Affiliated Sets file should

have numeric code 1; the second, 2; and so on. Service Area file records for service areas that are members ot the

set with code 1 should all contain a 1 in the affiliation code field.

Each affiliated set's numeric code is followed by a three-character set code. The user will recall from previous

discussions within this manual that affiliated sets of service areas must be treated in an all-or-nothing manner within

the NASARC modules. As an affiliated set is a set of geographically separated service areas that are to be serv_

from a single satellite, affiliated set members may only be placed in a larger compatible group of service areas if

all set members are eligible for inclusion. Service area codes for individual member service areas do not appear in

any compatible groups of service areas generated by NASARC1. Rather, if and only if all member service areas of

an affiliated set may be included in a compatible group of service areas, can the three character set code take the

place of individual three-character codes for member service areas. In this way, it is ensured that all members of

an affiliated set of service areas are treated as a single entity in the arc determination process, as desired. The

choice of a three-character set code is left to the user; however, care should be taken to avoid accidental

duplication of any administration code.

The final item to be included for each affiliated set in the Affiliated Sets file is an integer, expressing the number

of members in each affiliated set of service areas. This item is used for a variety of purposes within the NASARC

modules, including file checking and verification in NASARC0, construction of the list of service areas to be

examined within a portion of the orbit in the NASARC 1 module, and assembling a list of compatible candidate

service areas for group arc extension in the NASARC3 module.

91
Precise format information is contained in section 2.3.1.4 of this manual; for further discussion of the affiliated sets

concept, the user is referred to the NASARC (Version 4.0) Technical Manual (see section 3.1.1.2.2).

An example Affiliated Sets file and a partial Service Area file are presented in figure 3.2-3.

3.2.5 Inputs to NASARC0 Program/Input Data File

As discussed in section 2.3.1.6, the Input Data file is produced by execution of the NASARC0 module. The Input

Data file is composed partially of data drawn from several files; variables included in this category are the allotted

arc length equation constants and the grouping criterion. The file also contains the user's responses to queries

generated by the NASARC0 program. The input parameters to be supplied by the user are detailed in the

subsequent sections; guidelines are also given for the selection of appropriate values.

Following the discussion of required user inputs in the subsequent sections, the interactive prompts issued by the

NASARC0 program and the correct formats for responses are presented in table 3.2-2. An example Input Data file

is presented in figure 3.2-4. Those user inputs discussed in the subsequent sections are technical parameter values;

inputs such as the date and time of run and scenario description comments are also prompted for by NASARC0 but

are self-explanatory.

3.2.5.1 Downlink Frequency

The user is requested by the NASARC0 module to supply a single downlink frequency (expressed in GHz). The

frequency parameter has an important effect on antenna gain calculations and, therelore, on antenna discrimination

calculations. The value of frequency supplied by the user is utilized directly or indirectly in the calculation of

antenna on-axis gains, antenna half-power beamwidths, and coefficients for antenna discrimination equations: the

frequency affects antenna diameter-to-wavelength ratio and thus may determine which set of equations is utilized to

model the antenna fall-off characteristics for the earth station.

It is suggested that the user supply a frequency equal to the midpoint of the downlink band for which he or she

intends to apply NASARC; for exercises related to allotment planning of the Fixed Satellite Service, the selected

frequency should lie in one of the following intervals:

4.5 GHz =< FREQ __<4.8 GHz

10.7 GHz _< FREQ =< 10.95 GHz

11.2 GHz _<_FREQ ___11.45 GHz

3.2.5.2 Uplink Frequency

The user is requested by the NASARC0 module to supply a single uplink frequency (expressed in GHz). As for the

downlink, this parameter has an important effect on antenna gain calculations and antenna discrimination

calculations.

For the uplink frequency, it is suggested that the user supply a frequency equal to the midpoint of the uplink band

for which he or she intends to apply NASARC; for exercises related to allotment planning of the Fixed Satellite

Service, the selected frequency should lie in one of the following intervals:

6.425 GHz -< FREQ = 7.075 GHz

12.75 GHz - FREQ _< 13.25 GHz

92
FILE= CINP14AN CODES A1 FILE= PART ARCS A1

1 500 5

2 510 12

5 520 2

4 550 4

5 540 2

6 550 5

7 560 5

8 570 2

9 580 3

10 590 3

11 600 6

12 620 3

13 630 2

14 6_0 2

15 650 2

16 660 2

Y 0.8000 1.0000

ABN -119.00 -19.00

ADL 104.00 176.00 1

AFG 43.00 95.00

AFS" -25.00 84.00

AGL -37.00 74.00

ALB -29.00 69.00

ALG -50.00 37.00

ALS -169.00 -139.00 2

AND -48 O0

ARG -89 O0

AR2 -58 O0

ARS 21 O0

ASC -76

ATG -112

ATN -135

AUS 85

51.00

-55.00

-2q. O0

60.00

O0 53.00

O0 -12.00

O0 1.00

O0 -178.00

AU2 100.00 -133.00

AU3 35.00 167.00

AU4 103.00 -145.00

AU5 73.00 148.00

AUT -18.00 46.00

AZR -65.00 6.00

BOO -70.00 -61.00

B02 -70.00 -61.00

B03 -70.00 -61.00

5

6

6

6

6

6

Figure 3.2-3.--Affiliated Sets and Service Area files structure.

FILE= TEST DATA AI

ERROR FLAG : N

DOHNLINK FREQUENCY (GHZ) = 11.200

UPLINK FREQUENCY (GHZ) = 13.000

RECIEVER NOISE BANDHIDTH (MHZ) = 1.000

AFFILIATED SETS FLAG = Y

RAIN OUTAGE PERCENTAGE OF YEAR = 0.I00

MAXIMUM RAIN ATTENUATION LIMIT = 8.00

GROUPING CRITERION (DEGREES) = 1.000

CONSTANT C1= Clx(N-1)WCRIT = 1.000

CONSTANT C2= C2wBUFARC = 1.000

CONSTANT C3, C3WN = 0.000

CONSTANT C4, C4 = 0.500

SCENARIO IDENTIFIER = 01/23/89

COMMENT, EXAMPLE NASARCO INPUT DATA SET

COMMENT= FOR NASARC VERSION 4.0

12,30

Figure 3,2-4.--Example Input Data file.

93
3.2.5.3 Percent of Year Outage Due to Rain Attenuation

As has been stated, the NASARC0 program reads from several files to gather selected data, in part to determine

appropriate prompts to issue to the user. If the rain attenuation flag in the Service Area file is set to Y, indicating

that rain attenuation is to be included in appropriate calculations, the NASARC0 program prompts the user to

supply an annual percent-of-time outage for the link due to rain attenuation.

The selected percentage should lie within the following interval:

0.001 < RNOUT < 1.0

3.2.5.4 Maximum Rain Attenuation Limit

If the rain attenuation flag in the Service Area File read by NASARC0 is set to Y, the program first queries the

user regarding whether or not the rain attenuation to be taken into consideration is to be limited to a maximum

value. If the user responds in the affirmative, a prompt is issued for a value (in dB) that expresses the maximum

rain attenuation to be taken into account.

TABLE 3.2-2--INTERACTIVE PROMTS/USER RESPONSES FOR NASARC0 MODULE

PLEASE ENTER THE DATE AND TIME OF THIS RUN. ENTER THE DATE AS: "MONTH/DAY/YEAR" (EG. 03/09,'88). ENTER THE

TIME AS: "HOURS:MINUTES" (EG. 08:25).

ENTER DATE

(Response:date)

ENTER TIME

(Response:time)

if an Input Data file already exists, the existing input data will be displayed as follows:

THE AVAILABLE INPUT DATA IS THE FOLLOWING:

SCENARIO IDENTIFIER = 01/20/88 14:30

COMMENT:

COMMENT:

DOWNLINK FREQUENCY (GHZ) = 4.650

UPLINK FREQUENCY (GHZ) = 6,500

RAIN OUTAGE PERCENTAGE OF YEAR = 0.050

MAXIMUM RAIN ATTENUATION LIMIT = 10.00

WOULD YOU LIKE TO CHANGE ANY OF THE DATA ENTRIES AT THIS TIME? (IF SO, YOU WILL BE REPROMPTED FOR ALL

ENTRIES.) ENTER Y OR N

(Response: One character, Y or N)

If the user's response is N, NASARC0 will terminate.

If the user's response is Y, the following prompt will be issued:

YOU MAY NOW ENTER UP TO TWO LINES OF COMMENTS RELATED TO THIS SCENARIO. EACH LINE IS LIMITED TO 60

CHARACTERS. DO YOU WISH TO ENTER A COMMENT?. ENTER Y OR N

(Response: One character. Y or N)

If the user's response is N, NASARC0 will prompt for the next succeeding input.

If the user's response is Y, the following prompts will be issued:

ENTER LINE 1 OF COMMENT (60 CHARACTERS MAX)

(Response: descriptive text, 60 characters or less)

DO YOU WANT TO ENTER AN ADDITIONAL LINE OF COMMENT?. Y or N

(Response: one character, Y or N)

94
TABLE3.2-2.-- Concluded.

If the user's tzslxmse is N, the program will proceed to prompt for the next input.

If the user's response is Y the following prompt will be issued:

ENTER LINE I OF COMMENT (60 CHARACTERS MAX)

(Response: descriptive text, 60 characters or less)

The program willnow begin prompting for parameter values.

SPECIFY INPUTS AS REAL NUMBERS UNLESS PROMPTED OTHERWISE.

INPUT DOWNLINK FREQUENCY IN GHZ.

(Response: real number, range 4.5 to 4.8 GHz, 10.7 to 19.95 GHz, or 11.2 to 11.45 GHz)

INPUT UPLINK FREQUENCY IN GHZ

(Response: realnumber, range 6.425 to 7.075 Gl-lzor 12.75 to 13.25 Oliz).

ENTER THE PERCENT RAIN OUTAGE IN TERMS OF PERCENT OF THE YEAR.

THE DEFAULT VALUE IS 0.050 PERCENT OF THE YEAR.

DO YOU WISH TO RETAIN THIS VALUE? (ENTER Y OR N)

(Response: one character, Y or N)

If the user's response is Y, the program will issue the next prompt.

If the user's response is N, the following prompt will be issued:

ENTER NEW VALUE

?

(Response: real number, range 0.001 to 1.0)

WOULD YOU LIKE TO LIMIT THE MAXIMUM RAIN ATI'ENUATION? (ENTER Y OR N)

(Response: one characmr, Y or N)

If the user's response is N, the program will proceed.

If the user's response is Y the following prompt will be issued:

ENTER THE MAXIMUM RAIN ATTENUATION LIMIT.

THE DEFAULT VALUE IS 10.00 DB.

DO YOU WISH TO RETAIN THIS VALUE? (ENTER Y OR N)

(Response: one character, Y or N)

Ifthe user'sresponse isY, the defaultvalue willbe assigned and the program willproceed.

If the user's response if N, the following prompt will be issued:

ENTER NEW VALUE

(Response: real number, dB)

THE AVAILABLE INPUT DATA IS THE FOLLOWING:

SCENARIO IDENTIFIER = DATE, TIME

COMMENT: = USER SUPPLIED COMMENT 1

COMMENT: = USER SUPPLIED COMMENT 2

DOWNLINK FREQUENCY (GHZ) = USER SUPPLIED VALUE

UPLINK FREQUENCY (GHZ) = USER SUPPLIED VALUE

RAIN OUTAGE PERCENTAGE OF YEAR = USER SUPPLIED VALUE

MAXIMUM RAIN ATTENUATION LIMIT = USER SUPPLIED VALUE

WOULD YOU LIKE TO CHANGE ANY OF THE DATA ENTRIES AT THIS TIME?

(IF SO, YOU WILL BE REPROMPTED FOR ALL ENTRIES.) ENTER Y OR N

(Response: one character, Y or N)

If the user's response is Y, the entire sequence of prompts will be reissued.

If the user's response is N, the NASARC0 program will terminate.

95
3.2.6 Ellipse and Rain Attenuation Data

As stated in section 2.3.1.8, the Ellipse file is composed of blocks of three records. The first record of each set of

three contains an eight-character service area code, the orbital longitude at which the ellipse covering the service

area was calculated, the longitude and latitude of the beam aimpoint, the ellipse major and minor axis beamwidths,

and the orientation angle of the ellipse. Any ellipse calculation procedure may be utilized so long as the output of

the ellipse calculation is placed in the correct format to be utilized by the NASARC modules (see table 2.3-5).

For any ellipse calculation procedure used to construct an ellipse file for use by the NASARC modules, it is

important that the ellipse calculations for a service area be performed utilizing the same set of service area

polygon points that the user intends to use in the NASARC Point Sets file. This will ensure maximal accuracy

and consistency of the NASARC program calculations.

Ellipse data for service areas must correspond to the ordering of service areas within the Service Area file;

within each block of ellipse data, longitudes for which the ellipses have been calculated must range from the

westmost longitudinal limit of the service area's visible arc to the eastmost limit of that arc. Thus, in blocks of

data for service areas whose arcs cross the 180" meridian, the record containing the ellipse calculated at 180"

east longitude must be immediately followed by the record containing the ellipse parameters calculated at -179"

east longitude. As may be inferred from the preceding, ellipse records should reflect ellipse parameters calculated

at 1" increments for integral (whole degree) longitudes.

Rain attenuation data are contained in the subsequent two records of each block of three. The two records

correspond to two sets of uplink and downlink frequencies (e.g., C-band and Ku-band). Each of these records

contains attenuations calculated for each of up to 10 polygon points for the downlink frequency followed by

attenuations calculated for each of the points for the uplink frequency. For the sake of consistency with certain

portions of the NASARC software, it is suggested that the attenuations be calculated at 0.01-percent annual

outage, in accordance with the attenuation model currently adopted by the Consultative Committee for

International Radio (CCIR).

3.3 Using the NASARC (Version 4.0) Software Package

3.3.1 Invoking NASARC Programs

To utilize NASARC (Version 4.0) for a planning exercise, the NASARC procedure described in section 2.2.3

must be invoked by the user. The procedure first loads and executes the NASARC0 modules. The NASARC0

module verifies input data files for accuracy and prompts the user interactively for further input. When the user's

responses have been gathered, the Input Data file is generated.

The NASSEP module is then executed and calculates a matrix of required orbital separations for all possible pairs

of systems. This information is stored in the Separation Matrix file.

The NASARC1, NASARC2, NASARC3, and NASARC4 modules are executed in sequence for as many

segments to be examined as there are specified within the Segments file. Therefore, if the user's system does not

allow DO-loop constructs within user-created procedures, the NASARC1, NASARC2, NASARC3, and

NASARC4 modules must be loaded and executed as many times as necessary by the user.

When all the segments specified have been examined, the NASARC4 module produces the NASARC Report file,

the Condensed Report file, and the Predetermined Arc file.

3.3.2 Error Messages and Their Meanings

Table 3.3-1 contains a complete list of error messages generated by the NASARC modules. Information is also

included on subroutines that produce the messages and suggested sources of error. This information is intended to

96
allow the user to quickly and easily identify causes of execution errors. The error messages are written to the

logical unit defined for error messages--unit 19. The messages also appear on the user's screen; FORTRAN

logical unit 10 should be defined as the user's terminal. The user is advised to examine the Error Message file if

the expected results are not achieved (see section 2.3.3.4). The errors described generally result in premature

termination of the module in question, with the exception of those indicated in the table. Errors, which result m

necessary program termination, trigger the setting of an error flag in the Input Data file so that subsequent

program modules are not executed on invalid data. The occurrence of various error messages might be eliminated

by modifying the value of a parameter and recompiling to achieve a successful program run if the user has

sufficient memory. All parameter names, the programs and/or subprograms in which they occur, and their

current values are listed in the appendix.

TABLE 3.3-I--ERROR MESSAGES AND THEIR MEANINGS

Message Program/sabprogram Potential source

producing message of error

"ERROR--THE CONSTANTS NASARC0

USED IN DETERMINING PDA

LENGTH HAVE ALL BEEN

SPECIFIED AS 0.0 OR LEFT

BLANK. PLEASE CHECK THE

!FIRST RECORD OF THE

SERVICE AREA FILE."

"ERROR--THE SEGMENT FILE

BOUNDARIES DO NOT

PROVIDE CONTINUOUS

!PROGRESSION OF

CUMULATIVE ORBITAL ARC.

CHECK THE SEGMENT WITH

BOUNDARIES XXX.XX,

XXX.XX."

"ERROR--THE SERVICE ARC

SPECIFIED FOR AAA

EXCEEDS THE MAXIMUM

POSSIBLE VISIBLE ARC FOR

POSITIVE ELEVATIONS, OR

THE WEST AND EAST

BOUNDARIES FOR AAA MAY

BE REVERSED. CHECK THE

SERVICE AREA FILE."

"ERROR--MEMBERS OF THE

AFFILIATED SET WITH CODE

NUMBER N DO NOT

INTERSECT A COMMON

PORTION OF THE ORBITAL

ARC. CHECK SERVICE AREA

FILE FOR THE WEST AND

EAST BOUNDARIES OF

AFFILIATED SET MEMBERS

WITH CODE NUMBER N."

"ERROR--THE SPACE STATION

ANTENNA CODE SPECIFIED

IN THE SERVICE AREA FILE

FOR AAA IS NOT ONE OF THE

AVAILABLE CODES. PLEASE

CONSULT THE NASARC

MANUALS FOR AVAILABLE

CODES, THEN MAKE THE

APPROPRIATE CHANGES TO

THE SERVICE AREA FILE."

NASARC0

NASARC0

NASARC0

NASARC0

1. Self-explanatory. All

constants cannot be

set to 0.0 at same

time.

I. A record of Segments

file does not adjoin

any previous segment.

Correct the record

indicated.

1. Self-explanatory;

correct the record

indicated in the

Service Area file.

1. Incorrect Service Area

may have been

indicated as member of

set with code number N.

2. A service arc for

rn_mber service area may

have been incorrectly

specified.

1. Self-explanatory.

97
TABLE3.3-l--Continued.

Message Program/subprogram Potential source

producing message of error

"'ERROR--AN ILLEGAL NASARC0 I. Self-explanatory,

ANTENNA DATA ENTRY HAS

3EEN MADE IN THE SERVICE

_REA FILE FOR SERVICE

AREA AAA. PLEASE BE SURE

THE VALUES FOR DIAMETER,

SPACE STATION PARAMETER,

AND THE EFFIC1ENC1ES ARE

ALL POSITIVE."

"ERROR--THE EARTH

TERMINAL TRANSMIT

ANTENNA CODE SPECIFIED

IN THE SERVICE AREA FILE

FOR AAA IS NOT ONE OF THE

AVAILABLE CODES. PLEASE

CONSULT THE NASARC

MANUALS FOR APPROPRIATE

CODES, THEN MAKE THE

APPROPRIATE CHANGES TO

THE SERVICE AREA FILE."

"'ERROR--THE EARTH

TERMINAL RECEIVE

ANTENNA CODE SPECIFIED

IN THE SERVICE AREA FILE

FOR AAA IS NOT ONE OF THE

AVAILABLE CODES. PLEASE

CONSULT THE NASARC

MANUALS FOR APPROPRIATE

CODES, THEN MAKE THE

APPROPRIATE CHANGES TO

THE SERVICE AREA FILE."

"ERROR--THE NUMBER OF

MEMBERS IDENTIFIED IN THE

AFFILIATED SETS FILE FOR

AFFILIATED SET N DOES NOT

AGREE WITH THE AFFILIATED

SET FLAGS 1N THE SERVICE

AREA FILE."

"'ERROR--THE SPACE STATION

ANTENNA PARAMETERS

INDIVIDUALLY SPECIFIED IN

THE SERVICE AREA FILE FOR

MEMBERS FROM AFFILIATED

SET AAA ARE NOT THE

SAME. ALL MEMBERS OF THE

SAME AFFILIATED MUST

HAVE IDENTICAL SPACE

STATION PARAMETERS.

PLEASE CORRECT THE

PROBLEM AND RERUN."

"'ERROR--THE NUMBER OF

AFFILIATED SETS SPECIFIED

IN THE AFFILIATED SETS

FILE DOES NOT AGREE WITH

THE NUMBER OF FLAGS IN

THE SERVICE AREA FILE.

PLEASE CORRECT THE

PROBLEM AND RERUN."

NASARC0

NASARC0

NASARC0

NASARC0

NASARC0

1. Self-explanatory.

I. Self-explanatory.

I. Incorrect number of

members in Affiliated

Set file for set N.

2. Incorrect number of

service areas have

been identified as

members of set N within the Service Area file

1. Self-explanatory. Check

all Service Area file

entries belonging to

affiliated set AAA.

I. There are more/less

unique affiliated sets

identified in the

Affiliated Sets file

than are identified in

the Service Area file.

98
TABLE 3.3-1--Continued.

Message Program/mbprogram

producing message

"DATA ENTRY ERROR-- NASARC0

PLEASE ENTER A POSITIVE

REAL NUMBER."*

"YOU HAVE SPECIFIED A

FREQUENCY OUTSIDE OF THE

BANDS ALLOCATED TO THE

DOWNLINK FOR ALLOTMENT

PLANNING PURPOSES. PLEASE

CHECK YOUR DESIRED

VALUE AND RE-ENTER."a

"THE UPI.JNK FREQUENCY

SPECIFIED IS NOT IN THE

COMPANION FREQUENCY

BAND WITH THAT O_ THE

DOWNLINK FREQUENCY.

PLEASE RE-SPECIFY THE

UPLINK FREQUENCY IN THE

RANGE 6.425 to 7.075 GHz."

"THE UPL/NK FREQUENCY

SPECIFIED IS NOT IN THE

COMPANION FREQUENCY

BAND WITH THAT OF THE

DOWNLINK FREQUENCY.

PLEASE RE-SPECIFY THE

UPI.JNK FREQUENCY IN THE

RANGE 12.75 to 13.25 GHz."

"YOU HAVE SPECIFIED A

FREQUENCY OUTSIDE OF

THE BANDS ALLOCATED TO

THE UPLINK FOR ALLOTMENT

PLANNING PURPOSES. PLEASE

CHECK YOUR DESIRED

VALUE AND RE-ENTER."

"PLEASE ENTER YOUR

PREFERENCE AS Y OR N. TM

"NO POINT SET FOUND FOR

AAA"

"ERROR READING POINT SET

DATA WHILE LOOKING FOR

KEY: BBB. LAST KEY READ

BEFORE ERROR OCCURRED:

AAA"

"WESTERN ARC LIMIT FOR

AAA IS INCONSISTENT WITH

ELLIPSE FILE."

NASARC0

NASARC0

NASARC0

NASARC0

NASARC0

NASSEP/RDFTS2

NASSEP/RDPTS2

NASSEP/CREAT2

aDoes not terminate program execution.

Potential source

of error

I. User has entered a

reponse of incorrect

type to interactive

prompt by NASARC0.

i. User has specified a

downlink frequency

that is outside the

range:

(a) 4.5--4.8 GHz

03) 10.7--10.95 GHz

(c) 11.2--11.45 GHz

!. Self-explanatory.

1. Self-explanatory.

1. User has specified an

uplink frequency that is

outside the range:

(a) 6.425--7.075 GHz

03) 12.75--13.75 GHz

1. The user has supplied

a response inconsistent

with a required Y or N

response.

1. Point Sets file does not

contain point set for a

service area contained

in Service Area file.

2. Point set corresponding

to service area has code

that does not match

service area code.

1. Point Sets fde contains

error in one or more

records that causes error

in FORTRAN READ.

1. Ellipse file incorrectly

constructed.

2. Service arc for service

area AAA incorrectly

specified.

99
TABLE3.3- l--Continued.

Message Program/subprogram

producing message

"EASTERN ARC LIMIT FOR NASSEP/CREAT2

AAA IS INCONSISTENT WITH

ELLIPSE FILE."

"THE ELI2PSE PARAMETERS

FOR SERVICE AREA AAA AND

S/C LONG. XXXX.X COULD

NOT BE FOUND. INSTEAD THE

ELLIPSE FILE WAS POINTED

AT SERVICE AREA AAA AND

SIC LONG. XXXX.X."

"NO POINT SET FOUND FOR

AAA"

"'ERROR READING POINT SET

DATA WHILE LOOKING FOR

KEY BBB: LAST KEY READ

BEFORE ERROR OCCURRED:

AAA"

"WESTERN ARC LIMIT FOR

AAA IS INCONSISTENT WITH

ELLIPSE FILE."

"EASTERN ARC LIMIT FOR

AAA IS INCONSISTENT WITH

EI_II_E FILE."

"'THE ELLIPSE PARAMETERS

FOR SERVICE AREA AAA AND I

S/C LONG, XXXX.X COULD

NOT BE FOUND. INSTEAD THE

ELLIPSE FILE WAS POINTED

AT SERVICE AREA AAA AND

S/C LONG. XXXX.X."

"A GROUP EXCEEDS MAX

NUMBER OF MEMBERS AND

IS TRUNCATED. THE ARC

LOCATION IS XXX.XX:

CURRENT SEGMENT IS

XXX.XX TO XXX.XX.""

"THE MAXIMUM NUMBER OF

GROUPS HAS BEEN EXCEEDED

WITHIN THE SEGMENT

XXX.XX TO XXX.XX AT THE

LOCATION XXX.XX. ADJUST

SEGMENT LIMITS WITHIN

'THE SEGMENTS FILE."

NASSEP/CICHK2

NASARC I/RDPTS

NASARC !/RDPTS

NASARC 1/CREATE

NASARC 1/CREATE

NASARC 1/CICHK

NASARC 1

NASARC 1/ACCUM

mDoea _ terminate program execution.

Potential source

of error

1. Ellipse file incorrectly

conlRructed.

2. Service area for service

area AAA incorrectly

specified.

1. Ellipae array incorrectly

_; check

Ellipae file.

1, Point Sets file does not

contain point set for a

service area contained in

Service Area file,

2. Point set corresponding

to service area has code

that does not match

service area code.

I. Point Sets file contains

error in one or more

records that causes error

in FORTRAN READ,

1. Ellipse file incorrectly

constructed.

2. Service arc for service

area AAA incorrectly

specified.

1. Ellipse file incorrectly

constructed.

2. Service arc for service

area AAA incorrectly

specified.

1. Ellipse array incorrectly

constructed; check

Ellipse file.

1. A compatible group of

service areas has more

than MAXMEM

members. Redistribute

arc segments in

Segments file.

1. The total number of

compatible groups of

service areas has

exceeded MAXGRP.

Redistribute arc

segments in Segments

file.

100
TABLE3.3-l--Concluded.

Message Program/subprogram

producing messag_

"ERROR IN INPUT NASARC2/IIqPARM

PARAMETERS. NASARC2 RUN

TERMINATED."

"ERROR: THERE ARE MORE

GROUPS IN THE INPUT LIST

THAN THE ARRAYS CAN

HOLD. INCREASE THE VALUE

OF MAXGRP IN THE NASARC2

SOURCE CODE, RECOMPILE,

AND RE-EXECUTE."

"'ERROR: THERE ARE MORE

GROUPS IN THE INPUT LIST

THAN THE ARRAY CAN

HOLD. INCREASE THE VALUE

OF MAXRMN IN THE

NASARC2 SOURCE CODE,

RECOMPILE, AND

RE-EXECUTE."

"NO POINT SET FOUND FOR

AAA"

"ERROR READING POINT SET

DATA WHILE LOOKING FOR

KEY BBB: LAST KEY READ

BEFORE ERROR OCCURRED:

A_LA t'

"THE ELLIPSE PARAMETERS

I FOR SERVICE AREA AAA AND

S/C LONG. XXXX.X COULD

NOT BE FOUND. INSTEAD

THE ELLIPSE FILE WAS

POINTED AT SERVICE AREA

AAA AND S/C LONG.

XXXX.X."

NASARC2/INGRPS

NASARC2/INRMN

NASARC3/RDPTS

NASARC3/RDPTS

NASARC3/CICHK

aDoes not terminate program eJtecuUon.

Potential source

of error

!. Error flag in Input Data

file has been sel to Y as

result of previous error;

check Error Message

file for source.

1. There are too many

groups contained in the

NASARC I module

output Groups file.

Adjust parameter as

suggested or reduce list

by other means.

I. There are too many

groups in Unallotted

Groups file that adjoin

current segment. Adjust

parameter or reduce list

by other means.

I. Point Sets file does not

contain point set for a

service area contained

Service Area file.

2. Point set corresponding

to service area has code

that does not match

service area code.

!. Point Sets file contains

error in one or more

records that causes error

FORTRAN READ.

1. Ellipse array incorrectly

constructed; check

Ellipse file.

3.4 Interfacing the NASARC and ORBIT Programs

While the NASARC software package identifies common, overlapping arc segments that are shared by compatible

groups of satellite systems, the NASARC software does not identify specific orbital locations for individual

satellites. Also, while the NASARC software bases compatibility assessment of pairs of systems on a target

single-entry C/! that is calculated from an aggregate criterion, the software does not perform an aggregate

interference analysis. Aggregate interference analysis may only be performed when specific satellite positions are

known.

The ORBIT program, originally developed in Japan and now residing on the computer at the International

Frequency Registration Board, employs optimization techniques to determine satellite placements that allow a

I01
given aggregate C/I to be achieved for all systems. These operations are performed under constraints imposed by

service arc limitations and other technical parameters that are common to both the NASARC and ORBIT

programs. In fact, the input data me for the ORBIT program is the Requirements Data file discussed in section

2.3.1.2 of this User's Manual. In conjunction with the satellite positioning process, ORBIT also performs a full

aggregate interference analysis for the input scenario.

The preceding discussion indicates that it is desirable to dovetail the capabilities of NASARC and ORBIT via an

interface to allow the arc limitations de2.crmined by NASARC to be superimposed on the appropriate inputs of the

Requirements Data file. Then ORBIT may be run to determine precise satellite locations within predetermined

arcs found by NASARC and to demonstrate that aggregate interference criteria may be satisfied.

For purposes of allotment planning of the Fixed Satellite Service at the 1988 Space World Administrative Radio

Conference, an automated interface program was constructed to perform the function described previously--i.e.,

superimpose predetermined arc limits for each administration, found by NASARC, onto the appropriate fields of

the Requirements Data file. This interface uses the Predetermined Arc file (discussed in section 2.3.3.3 of this

User's Manual) and the Requirements Data file (see section 2.3.1.2) as input files; the output is a modified copy

of the Requirements Data file.

Since the NASARC/ORBIT interface was developed for the specific purpose of allotment planning at the 1988

Conference, it is not included as part of the NASARC software package. The program is also only useful if the

user posseses a Requirements Data file (see section 2.3.1.2 herein) and the ORBIT software. The interested user

is urged to contact the International Frequency Registration Board in Geneva, Switzerland, if further information

on the ORBIT software is desired.

REFERENCES

The Orbit Spacing Minimizer (ORBIT-R) User's Manual. Kokusai Denshin Denwa Co., LTD. Apr. 1984.

APPENDIX--NASARC PROGRAM PARAMETERS

The NASARC program parameters described in the following table largely affect array dimensions within one or

more NASARC modules. Thus, they also affect the storage requirements of the modules in which they occur.

The values listed in the table were carefully selected to provide the programs with maximum capability to

accommodate a variety of scenarios, while still permitting each module to be loaded within the 12-megabyte

memory limitation of the IFRB computer system.

The user is reminded that if a parameter value is changed within the NASARC source code, the appropriate

module must be recompiled prior to use.

NASARC PROGRAM PARAMETERS

Name Definition Locations Value a

MAXITU Maximum number of service area 3OO

records that may be contained

in the Service Area file

NASINTRF:

MAIN

NASARC0:

MAIN

NASSEP:

MAIN

RDPTS2

CREAT2

CICHK2

aValues are those that meet the |2-megabyte memory limitationof the IFRB computer,

102
Nani¢

MAXITU

:(cont.)

MAXCOD

MAXSEG

MAXTER

MAXMEM

Definition

Maximum number of service area

records that may be contained

in the Service Area file

Maximum number of service areas

to be included in affiliated sets

Maximum numbex of segme_ to be

examined, within the Segment file

Maximum number of _ sets

of service areas within Affiliated

Sets file

Maximum number of service areas

that may be included in a

compatible group

aValues are Ihose thai meet the 12-megabytememory limitatio_of the

_OnS

NASARC I :

MAIN

CREATE

RDPTS

NASARC3:

MAIN

RDPTS

REPORT

NASARC4:

MAIN

REPORT

CNDREP

NASINTRF:

MAIN

NASARC0:

MAIN

NASARC4:

REPORT

CNDREP

AFFINT

NASARC0:

MAIN

NASARC 1 :

MAIN

NASARC2:

INSEGS

NASARC4:

MAIN

REPORT

CNDREP

NASINTRF:

MAIN

NASARC0:

MAIN

NASSEP:

MAIN

NASARC I :

MAIN

NASARC3:

MAIN

NASARC4:

MAIN

REPORT

CNDREP

NASARC0:

MAIN

NASARC 1 :

MAIN

NASARC2:

MAIN

INGRPS

INALLT

LSTALT

CRTGRP

IFRB _omputer.

Value*

99

40

25

15

103
Name Definition Locations Value*

MAXMEM

(cont.)

MAXELL

MAXGRP

MAXIFr

MAXTEM

NUMR

Miutimum number of service areas

that may be included in a

compatible group

Maximum number of _ records

that may be contained in Ellipse

file

Maximum number of compatible

groups and group arcs that may be

produced by NASARCI within a

single segment of the orbit

Mmmum mr_ef of _go. pomt_

for each service area

Maximum number of groups, group

arcs in temporary list

Number of groups, individual arc

locations processed at one time, in

creating temporary list of groups,

group arcs

UPDATE

UNPACK

GRPBUF

XTRACT

PULL

INDEX2

SUBLST

MAXSEP

UPDAT'2

NASARC3:

,MAIN

NASARCA:

MAIN

UNPACK

NASSEP:

MAIN

CREAT2

CICHK2

NASARC 1:

MAIN

CREATE

NASARC 1:

MAIN

ACCUM

CHKIS0

OUTLST

NASA RC2:

MAIN

INGRPS

JOINER

CRTADM

SUBLST

OUTRMN

_ASINTRF:

MAIN

NASSEP:

MAIN

NASARC 1:

MAIN

CREATE

RDPTS

CICHK

NASARC3:

MAIN

RDPTS

CICHK

NASARCI :

MAIN

ACCUM

CHKI80

NASARC 1 :

MAIN

ACCUM

CHKi80

avatues are those that rnee/ the 12-megabytememory limitationof the IFRB computer.

35,000

90,000

10

10,000

10,000

104
Name

MSGELL

MSGITU

MAXALT

MAXALT

MAXSUB

Definition Locations

Maximum number of ellipe records NASARCI:

to be utilized in single segment of MAIN

the orbit CREATE

CICHK

NASARC3:

MAIN

CICHK

Maximum number of service areas NASARC I:

to be examined for compatibility MAIN

within single segment of the orbit CREATE

RDPTS

CICHK

OUTLST

NASARC2:

MAIN

INGRPS

PARTIT

CRTADM

MISSPI

PRIOR

ITUARC

GRPBUF

SACHK

CRTGRP

NASARC3:

MAIN

RDPTS

CICHK

Maximum number of allotted groups NASARC2

(over all segments of orbit) MAIN

INALLT

CRTADM

LSTALT

SEGCHK

PTACHK

ALLOT

NEIGH

PDASEP

UPDAT2

PUSH

ARCCHK

FINSEP

NASARC3:

MAIN

NASARC4:

MAIN

SWAP

FEASIN

REPORT

CNDREP

TEMPOR

PUSH

PTACHK

ARCCHK

NASARC2:

MAIN

GRTGRP

meet the 6-megabyte memory limitation of the IFRB computer

Maximum number of allotted groups

(over all segments of orbit)

Maximum number of groups

containing critical service area

aValuesare those th

Value a

16,000

100

150

10,000

105
Name Definition

MAXRMN

MAXREC

MAXF

MAXX

MAXZ

MAXD

MAXMAT

MAXPTA

NGROUP

MAXPDA

Maximum number of unallotted

groups that adjoin either edge

of current segment of orbit

Maximum number of records

in NASARC2 Intermediate

Selection file, Unallotted

Groups file

Maximum number of aggregate arcs

for subset arc extensions

Maximum number of groups in

sublist of groups containing

critical service area

Maximum number of groups in

sublist for which given group is a

sublis!

Maximum number of groups in

critical groups sublist for which

duplicates or subsets exist

Maximum number of entries in

satellite separations file

Maximum numbex of pow, ntial

mmpotm_ allotments within

group's group arc

Maximum number of allo{tod

groupings

Maximum number of allotted

groupings

Locations Value a

NASARC2: 10,000

MAIN

INRMN

JOINER

NASARC2: 1,000,000

MAIN

INRMN

OUTRMN

NASARCA:

MAIN

NASARC2: 100

COMBIN

NASARC2: 10,000

MAIN

CRTGRP

NASARC2: 10,000

SUBLST

XTEND

NASARC2: 18,000

XTEND

NASARC2: 20,000

MATRIX

MAXSEP

NASARC4: 180

TEMPOR

NASARC4: 150

PUSH 1

NASARC4: 150

PUSH2

aValues are those thai meet the 12*mcg_ytc memory limitation of the IFI_ cornl_ter.

I06
Report Documentation Page Nal_onal AeronaL, tlcs and

Space Adm_ntslrat,on

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.

NASA TM-101454

4. Title and Subtitle

Numerical Arc Segmentation Algorithm for a Radio Conference--NASARC

(Version 4.0)

User's Manual

7. Author(s)

Wayne A. Whyte, Jr., Ann O. Heyward, Denise S. Ponchak,

Rodney L. Spence, and John E. Zuzek

9. Performing Organization Name and Address

National Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio 44135-3191

12. Sponsoring Agency Name and Address

National Aeronautics and Space Administration

Washington, D.C. 20546-0001

5. Report Date

October 6, 1988

6. Performing Organization Code

8. Performing Organization Report No.

E-4987

10. Work Unit No.

643-10-01

11. Contract or Grant No.

13. Type of Report and Period Covered

Technical Memorandum

14. Sponsoring Agency Code

15. Supplementary Notes

16. Abstract

The information contained in the NASARC (Version 4.0) Technical Manual (NASA TM-101453) and NASARC

(Version 4.0) User's Manual (NASA TM-101454) relates to the state of Numerical Arc Segmentation Algorithm

for a Radio Conference (NASARC) software development through November 1, 1988. The Technical Manual

describes the NASARC concept and the algorithms used to implement the concept. The User's Manual provides

information on computer system considerations, installation instructions, description of input files, and program

operation instructions. Significant revisions have been incorporated in the Version 4.0 software over prior

versions. These revisions have further enhanced the modeling capabilities of the NASARC procedure and provide

improved arrangements of predetermined arcs within the geostationary orbit. Array dimensions within the

software have been structured to fit within the currently available 12-megabyte memory capacity of the

International Frequency Registration Board (IFRB) computer facility. A piecewise approach to predetermined arc

generation in NASARC (Version 4.0) allows worldwide planning problem scenarios to be accommodated within

computer run time and memory constraints with enhanced likelihood and ease of solution.

17. Key Words (Suggested by Author(s))

Orbit planning

Arc segmentation

Predetermined arcs

18. Distribution Statement

Unclassified - Unlimited

Subject Category 32

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No of pages 22. Price*

Unclassified Unclassified 112 A06

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Cleveland, Ohio 44135

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