User's Guide for the Infrared Sensor Modeling Interface (ISMI)jefgeorge.com/Reports/hlpISMI.pdfUSER'S GUIDE FOR THE INFRARED SENSOR MODELING INTERFACE (ISMI) ... Technical Revision:

USER'S GUIDE FOR THE INFRARED SENSORMODELING INTERFACE (ISMI)

Report Prepared by:Everett George

Dahlgren DivisionNaval Surface Warfare CenterElectro-Optical Systems Branch (F44)Dahlgren, VA 22448

Technical Revision:1991-08-23

Format Revision:2014-05-08

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TABLE OF CONTENTS1.0 INTRODUCTION................................................................................32.0 METHODOLOGY...............................................................................33.0 PROCEDURE....................................................................................64.0 FILE NAMING CONVENTION............................................................9

4.1 FILE NAMING CONVENTION EXAMPLE.....................................95.0 INPUT DATA FILE FORMAT.............................................................10

5.1 LOWTRAN TAPE5 INPUT FILE FORMAT..................................105.2 CONTIRR INPUT DATA FILE......................................................115.3 TGTGEN TARGET DATA FILE FORMAT....................................115.4 TGTGEN SENSOR DATA FILE FORMAT...................................125.5 TGTGEN AUXILIARY TRAJECTORY DATA FILE FORMAT.......12

6.0 COMMAND DESCRIPTIONS...........................................................136.1 CONTIRR....................................................................................136.2 LOWR2T.....................................................................................146.3 LOWT2B.....................................................................................146.4 LOWTRAN..................................................................................146.5 TGTBAT......................................................................................156.6 TGTDET......................................................................................156.7 TGTTRJ.......................................................................................16

7.0 ADDITIONAL COMMANDS..............................................................167.1 CONCHG....................................................................................167.2 LOWATM.....................................................................................177.3 LOWHS.......................................................................................177.4 LOWHT.......................................................................................187.5 LOWRHI......................................................................................187.6 LOWRNG....................................................................................197.7 LOWRTB.....................................................................................19

8.0 ATMOSPHERIC PROFILE FILE FORMAT.......................................209.0 REFERENCES.................................................................................2110.0 INDEX............................................................................................22

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1.0 INTRODUCTION

The Infrared Sensor Modeling Interface (ISMI) discussed in this document is a group of software files which supports an interface between the SPIRCADE Target Generator Program (TGTGEN) used at Naval Surface Warfare Center (NAVSWC), White Oak (WO), and the LOWTRAN / CONTIRR Program combination used at NAVSWC, Dahlgren (DL). These programs support development of U.S. Navy infrared (IR) sensors by modeling target approach, sensor detection, and signal processing of target IR radiation emissions.

The purpose of this document is to provide information for usage of the interface in constructing TGTGEN, LOWTRAN, CONTIRR, and SPIRCADE input files. Section 2.0 of this document describes methodology used in the interface development. Section 3.0 gives a step-by-step procedure applying the interface. Section 4.0 explains the file naming convention necessary for interface execution. Input data file formats are discussed in Section 5.0 . Section 6.0 gives a separate review of each software command developed for the interface. Section 7.0 and Section 8.0 give information on additional interface commands which may be useful in the IR analysis process. Section 9.0 cites reference material which contains further information concerning IR sensor modeling used here. Section 10.0 gives an alphabetical index of material contained in this document.

The interface software was developed on a personal computer with an INTEL 8 Megahertz 80286 microprocessor running Microsoft Disk Operating System (MS-DOS) Revision 3.3. The software was written in FORTRAN using a FORTRAN 77 compiler developed by Lahey Computer Systems, Incorporated.

An important part of any software application is feedback to the developer concerning program operation errors. This software is not anticipated to be error free. If errors are detected, they should be recorded and reported such that the problem can be rectified.

2.0 METHODOLOGY

The end products of the interface procedure are specially formatted files containing target detection data. The SPIRCADE Program uses these files as input to simulate signal processing of an IR sensor. TGTGEN essentially duplicates the interface process in support of SPIRCADE. However, the procedure described here introduces high accuracy atmospheric propagation modeling and target spectral signatures to simulate losses and refraction of target emitted IR radiation.

To implement the methodology, the source code of TGTGEN was modified such that LOWTRAN and CONTIRR could interface with SPIRCADE. These later programs (LOWTRAN, CONTIRR, and SPIRCADE) remain unchanged in support of this application. TGTGEN is divided into two separate programs which (1) handle trajectory generation (before the LOWTRAN propagation analysis) and (2) determine detection estimations (after the CONTIRR radiation integration at the sensor). The first TGTGEN modified program is designated as the Target Trajectory Interface (TGTTRJ), the second as the Target Detection Interface (TGTDET). Figure 1 illustrates the relationships between these IR modeling programs. More information concerning TGTGEN applications can be found in Reference [1] .

TGTTRJ generates trajectory paths and stores possible target detection locations in a file format adequate for LOWTRAN input. Trajectory maneuvers, sensor operational parameters and other target / sensor information are input to the program through data files. From this data, possible detection locations are calculated and inserted into an existing LOWTRAN TAPE5 data file. The TAPE5 file contains atmospheric modeling information required for LOWTRAN analyses. Target locations are included in the TAPE5 file irrespective of whether horizon blockage would occur. The program also outputs SPIRCADE detection input files based on data supplied in the target data files.

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LOWTRAN is a generic atmospheric modeling program which computes refraction and transmittance parameters of radiation propagation. In this application, the program analyzes propagation based on output files generated directly from TGTTRJ. From atmospheric modeling parameters, propagation start and end locations, and spectral wavelengths of interest, the program determines transmittance characteristics, and foreground and background radiation. The program also calculates refraction of target radiation making a determination of horizon blockage. If the program does detect blockage, the output data contains error messages for that target location. More information concerning LOWTRAN can be found in Reference [2] and Reference [3] .

To produce CONTIRR input data, LOWTRAN must be run three separate times. The first LOWTRAN run uses range data generated by TGTTRJ to determine refracted zenith angles of the target in relation to the sensor. These zenith angles are integrated into the TAPE5 input file, and LOWTRAN is run again to determine transmittance and foreground radiation characteristics at each possible target detection location. LOWTRAN is run a third time with the zenith angles to determine background radiation. Auxiliary software commands manipulate LOWTRAN input and output files to aid in the LOWTRAN runs. More information concerning CONTIRR can be found in Reference [3] .

CONTIRR combines the LOWTRAN output files with target radiation signature data files and computes contrast irradiance at possible detection locations. The contrast irradiance is summed over the spectral band that the sensor examines. Contrast irradiance output is given for each possible detection location taking into account horizon blockage, but regardless of detection thresholds set for the sensor. Target radiation characteristics are taken from either empirical measurements or data derived from first principle modeling of the event at a particular point in time. This target signature description defines radiation intensities at a target's specific position, speed, and aspect angle which are held constant through the duration of the trajectory.

TGTDET combines target contrast irradiance and the refracted zenith angle along with trajectory and sensor data and builds a SPIRCADE detection input file. The output takes into account spectral transmittance of the atmosphere, refracted path of radiation propagation computed by LOWTRAN / CONTIRR, and sensor detection threshold limits. In determining refraction effects, LOWTRAN uses an iteration technique which approximates the true range of the target at time of detection. To increase accuracy, both the contrast irradiance and refracted zenith angle used in TGTDET are interpolated from CONTIRR / LOWTRAN generated data.

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Figure 1. BLOCK DIAGRAM OF INFRARED SENSOR MODELING ANALYSYS

3.0 PROCEDURE

This section describes a step-by-step procedure for generating SPIRCADE detection input files using LOWTRAN. The files listed in this procedure follow a file naming convention defined in Section 4.0 . A description of each command is given in Section 6.0 . Figure 2 illustrates command usage and information flow of the procedure described here.

If all runs in the procedure are error-free, the entire process can be performed using the single command TGTBAT. This command is a batch file which implements the procedure described below.

Syntax: TGTBAT name<ENTER>

a) Build initial data files (text editor). These files contain all the information necessary for the interface analyses. Input file formats are discussed in Section 5.0 . The LOWTRAN TAPE5 template data file should contain accurate atmospheric and wavelength parameters (Cards 1, 2, 4, 5).

Input Files:

tgt-sig - target signature filename.TP5 - LOWTRAN TAPE5 data filename.DAT - CONTIRR input data filename.TGT - TGTGEN target data filename.SNR - TGTGEN sensor data filename.TRJ - TGTGEN auxiliary trajectory data file

b) Generate target trajectory data in a format acceptable for LOWTRAN atmospheric propagation analysis. The TAPE5 file generated specifies range-designated data (Card 3) for target locations.

Syntax: TGTTRJ name<ENTER>

c) Find refracted zenith angles of each target location using LOWTRAN and the TAPE5 input files constructed from step (b).

Syntax: LOWTRAN Rname<ENTER>

d) Construct a LOWTRAN TAPE5 input file for the target trajectory based on refracted angles generated in step (c).

Syntax: LOWR2T name<ENTER>

In specific cases, LOWTRAN propagation calculations from target locations will generate execution errors in step (c). These errors will usually be due to horizon blockage of the propagation path. If these errors occur, error messages will be indicated in LOWTRAN TAPE6 and TAPE7 files as well as in the read out of LOWR2T. To eliminate the errors, start / stop trajectory times may be modified in the target data file of step (a).

e) Find transmittance values of radiating target and foreground radiation at the target based on refracted zenith angle locations from step (d).

Syntax: LOWTRAN Tname<ENTER>

f) Construct a LOWTRAN TAPE5 input file to determine background radiation using refracted angles from

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step (d).

Syntax: LOWT2B name<ENTER>

g) Find transmittance and irradiance values of the atmospheric background area in the direction of the target based on refracted zenith angle locations. Use the LOWTRAN TAPE5 file generated in step (f).

Syntax: LOWTRAN Bname<ENTER>

h) Combine LOWTRAN TAPE7 runs for both target and background radiation calculations (step (e) and (g)) along with the target signature file (step (a)) to determine contrast irradiance for each geometric target location.

Syntax: CONTIRR name<ENTER>

i) Generate SPIRCADE input files using trajectory / sensor data defined in initial data files (step (a)) and contrast irradiance data from the CONTIRR Program run (step (h)).

Syntax: TGTDET name<ENTER>

j) Final Output Files:

name.FFL - SPIRCADE detection data file (formatted)name.UFL - SPIRCADE detection data file (unformatted)

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The above diagram shows relationships between files and commands. Data flows chronologically from the top of the illustration to the bottom.

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Figure 2. INFORMATION AND PROCEDURES FLOW CHART

4.0 FILE NAMING CONVENTION

A file naming convention must be followed for the software to identify data files and generate output. A file extension identifies the type of data in a file and the file format. A list of file extensions and their significance is given below.

.DAT - CONTIRR input data file

.FFL - SPIRCADE detection data file (formated)

.PRN - CONTIRR contrast irradiance output file

.SNR - TGTGEN sensor data file

.TGT - TGTGEN target data file

.TRJ - TGTGEN auxiliary trajectory data file

.TP5 - LOWTRAN TAPE5 data file

.TP6 - LOWTRAN TAPE6 output file

.TP7 - LOWTRAN TAPE7 output file

.UFL - SPIRCADE detection data file (unformatted)

A file prefix is used to identify data files which have the same format but different data values in the format. A list of file prefixes and their significance is given below.

R - LOWTRAN range-designated target data fileT - LOWTRAN angle-designated target data fileB - LOWTRAN angle-designated background data file

4.1 FILE NAMING CONVENTION EXAMPLE

The data files listed below identify the initial input files and output data files that would occur in a single SPIRCADE input file generation. The upper-case letters in the file names indicate prefixes and suffixes which must be present for file identification. The lower-case letters in the file name (e.g., “name”) indicate the character string identifier which would be used to group the file set. The character string can contain any valid DOS file name character with up to seven characters in the string. The target signature file is usually a data file located elsewhere in the file directory and conforms to a different naming convention.

Initial Input Files:


Software Generated Output Files:

Rname.FFL - SPIRCADE detection data file using ALRRI/ALPHA dataRname.UFL - SPIRCADE detection data file using ALRRI/ALPHA dataRname.TRJ - TGTGEN auxiliary trajectory data fileRname.TP5 - LOWTRAN TAPE5 range-designated target data fileRname.TP6 - LOWTRAN TAPE6 range-designated target output fileRname.TP7 - LOWTRAN TAPE7 range-designated target output file

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Tname.TP5 - LOWTRAN TAPE5 angle-designated target data fileTname.TP6 - LOWTRAN TAPE6 angle-designated target output fileTname.TP7 - LOWTRAN TAPE7 angle-designated target output fileBname.TP5 - LOWTRAN TAPE5 angle-designated background data fileBname.TP6 - LOWTRAN TAPE6 angle-designated background output fileBname.TP7 - LOWTRAN TAPE7 angle-designated background output filename.PRN - CONTIRR irradiance output filename.FFL - SPIRCADE detection data file using LOWTRAN dataname.UFL - SPIRCADE detection data file using LOWTRAN data

These example file names are used throughout this document in describing data generation.

5.0 INPUT DATA FILE FORMAT

The following data files should be created or modified by the user. In most cases, the other data files contain software output and should be accessed by the user only to determine success or failure of the software calculations.


Except for the target signature file, the above files must reside in the local directory for software access. The files must have the designated file extension for program identification.

The “tgt-sig” file defines target signature data in an FTD format. In addition, the LOWTRAN TAPE5 input file specifies input data in a TAPE5 format. These formats are column specific, i.e., the data values must appear in specific columns on each line. If data is not in the correct column, either read errors will be generated or incorrect values will be read for the program run. Usually, the format can be maintained by copying other files of the same type to a new file name then changing values with a text editor.

In the other four files (with “DAT”, “SNR”, “TGT”, “TRJ” extensions), data is read in using free format. Free format is not column specific. Blank spaces or commas can be used to separate data value within a line.

5.1 LOWTRAN TAPE5 INPUT FILE FORMAT

The LOWTRAN TAPE5 input file contains information necessary to model radiation propagation in specific atmospheric conditions. Such parameters include:

Card 1 - atmospheric model type- propagation path type- radiance mode

Card 2 - instantaneous wind speed- 24-hour average wind speed- rain rate- visibility parameter- propagation path type

Card 2C# - atmospheric profile dataCard 3 - geometry data

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Card 4 - beginning wavenumber (1 / cm)- ending wavenumber (1 / cm)- wavenumber increment (1 / cm)

Card 5 - repeat batch flag

Geometry data (Card 3) is updated through TGTTRJ target generator runs. The TAPE5 input file should have a valid format which does not generate errors during a LOWTRAN run; therefore, all data entries should have valid formats. The LOWTRAN TAPE5 files are identified through file extension “TP5”. More information concerning LOWTRAN TAPE5 file construction is contained in Reference [2] and Reference [3].

Example LOWTRAN TAPE5 Input File Format:

[Start of File]

BLANKED

[End of File]

5.2 CONTIRR INPUT DATA FILE

The CONTIRR input data file identifies other input files for the program run as well as specific variables needed for contrast irradiance calculations. The file is identified by file name extension “DAT”. The file format consists of seven or more data entry lines. The function and format of the lines are as follows:

Line 1: LOWTRAN TAPE7 angle-designated target output file nameLine 2: LOWTRAN TAPE7 angle-designated background output file nameLine 3: FTD format target signature fileLine 4: CONTIRR data output fileLine 5: beginning wavelength (microns), ending wavelength (microns), target area (cm2)

Line 6: noise equivalent irradiance (NEI) (W / cm2), threshold-to-noise ratio (TNR), estimated declaration lag time (s)

Line 7: batch flag number (1 – more data, 0 – end of data)

More information concerning the CONTIRR input data file can be found in Reference [3] .

Example CONTIRR Input File Format:

[Start of File]

BLANKED

[End of File]

5.3 TGTGEN TARGET DATA FILE FORMAT

The target data file contains information which is specific to the target and its trajectory. The file is identified through file name extension “TGT”. The order and format of the file follow the interactive format used in the TGTGEN interface. The file has a single data entry per line format such that the first non-blank character string in the file is read as the beginning of data. Information after the values is comments which can identify the entry for the user. The data is limited to the units of measure specified. Only one target type and target trajectory can be specified in the file. More information about target parameter values can be found in Reference [1] .

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Example TGTGEN Target Data Format:

[Start of File]

BLANKED

[End of File]

5.4 TGTGEN SENSOR DATA FILE FORMAT

The sensor data file contains information specific to the sensor and signal processor. The file is identified through file name extension “SNR”. The order and format of the file are the same used in the sensor data file for TGTGEN. Except for the spatial filter weights, the file has a single data entry per line. Data values are separated by commas “,” for spatial filter weights. Information after the values is comments that identify the entry for the user. The data is limited to the units of measure specified. More information about sensor parameter values can be found in Reference [1] .

Example TGTGEN Sensor Data File Format:

[Start of File]

BLANKED

[End of File]

5.5 TGTGEN AUXILIARY TRAJECTORY DATA FILE FORMAT

The auxiliary target data file contains information which, when used with the CONTIRR output file, defines the target trajectory for detection analysis in TGTDET. The file is identified by the file name extension “TRJ”. If TGTTRJ is used as a target trajectory generator, the auxiliary trajectory data file is generated automatically. However, trajectories can be generated from other sources and input into TGTDET providing this data file exists and its data correlates with geometry data in the LOWTRAN TAPE5 input file.

Each data line entry in the file corresponds to a possible detection in the trajectory. The detection entries are entered in chronological order of occurrence. These directions are based on a match in sensor azimuthal position and trajectory bearing. The detection occurrences need not consider horizon blockage or target radiation losses. For each detection the following information is recorded:

time of detection - secondsrange of target from sensor - kilometerstarget bearing - degreestarget altitude - kilometerstarget velocity x-coordinate - kilometers / secondtarget velocity y-coordinate - kilometers / secondtarget velocity z-coordinate - kilometers / secondstandard deviation of target - percent intensity as percent of meanhorizontal extent of target - metersvertical extent of target - meters

The data must appear in the above order on each line. When the file is read by TGTDET, free format is used to parse the data; therefore, column location of the data is not important. Data values within the line

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are separated by spaces. Units of the data are limited to those as indicated above. An asterisk “*” appearing as the first character in the line designates the line as a comment, i.e., the line is ignored when data is read in by software.

Target velocity is defined in a fixed three-dimensional Cartesian coordinate system dependent on sensor orientation. The x-coordinate velocity is measured in the zero degree azimuthal direction of the sensor with positive directions going outward from the sensor. The y-coordinate velocity is measured in the sensor ninety degree azimuthal direction with positive values outward. The z-direction velocity is measured vertically with the positive direction upward. More information about parameter values in this data file can be found in Reference [1] .

Example TGTGEN Auxiliary Trajectory Data File Format:

[Start of File]

BLANKED

[End of File]

6.0 COMMAND DESCRIPTIONS

This section identifies software commands used to support the TGTGEN / LOWTRAN / CONTIRR / SPIRCADE interface. A listing of the commands follows.

CONTIRR - calculates target contrast irradianceLOWR2T - builds a LOWTRAN TAPE5 T-file (target)LOWT2B - builds a LOWTRAN TAPE5 B-file (background)LOWTRAN - calculates atmospheric propagation parametersTGTBAT - executes command sequences for interfaced executionTGTDET - builds SPIRCADE detection data filesTGTTRJ - inserts target trajectories into a LOWTRAN TAPE5 R-file

For each command, a brief description is given along with file input and output names, syntax and a command example. To execute the software, the command syntax is entered at the MS-DOS prompt in the directory of the data files.

6.1 CONTIRR

CONTIRR calculates contrast irradiance from LOWTRAN TAPE7 and target signature files. See Reference [2] .

File input:name.DAT - CONTIRR input data fileTname.TP7 - LOWTRAN TAPE7 target output fileBname.TP7 - LOWTRAN TAPE7 background output filetgt-sig - target signature file

File output:name.PRN - CONTIRR irradiance output file

Syntax:CONTIRR name<ENTER>

where

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name – file identifier (without extension) for the CONTIRR data file

Example:CONTIRR t183<ENTER>

6.2 LOWR2T

LOWR2T constructs a LOWTRAN TAPE5 angle-designated file from LOWTRAN TAPE5 and TAPE7 range-designated files. The TAPE7 file is scanned to find zenith angle data associated with each range data of the TAPE5 file. For each Card 3 occurrence in the range-designated TAPE5 file, the associated zenith angle is entered in the angle-designated TAPE5 file with target range and earth-centered angle set at zero. If the number of TAPE7 zenith angles do not correspond to the number of TAPE5 Card 3 occurrences, an error message is given.

File Input:Rname.TP5 - LOWTRAN TAPE5 range data fileRname.TP7 - LOWTRAN TAPE7 range output file

File Output:Tname.TP5 - LOWTRAN TAPE5 target data file

Syntax:LOWR2T name<ENTER>

wherename - file identifier (without prefixes or extensions) for LOWTRAN data files

Example:LOWR2T d261<ENTER>

6.3 LOWT2B

LOWT2B converts a LOWTRAN TAPE5 angle-designated target file to a LOWTRAN TAPE5 angle-designated background file. In the output, the variable ITYPE of Card 1 is set at “3” to indicate a propagation path to space. For each Card 3 occurrence, the target height, range, and earth-centered angle are set to zero.

File Input:Tname.TP5 - LOWTRAN TAPE5 target data file

File Output:Bname.TP5 - LOWTRAN TAPE5 background data file

Syntax:LOWT2B name<ENTER>


Example:LOWT2B d261<ENTER>

6.4 LOWTRAN

LOWTRAN calculates atmospheric propagation parameters. See Reference [2] . The command automatically renames LOWTRAN generated TAPE6 and TAPE7 files to the file names indicated below.

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File Input:name.TP5 - LOWTRAN TAPE5 data file

File Output:name.TP6 - LOWTRAN TAPE6 output filename.TP7 - LOWTRAN TAPE7 output file

Syntax:LOWTRAN name<ENTER>


Example:LOWTRAN d261<ENTER>

6.5 TGTBAT

TGTBAT is a batch command which executes the proper command sequences to produce SPIRCADE detection data files from TGTTRJ target trajectory data. For this command to run successfully, the command sequences must execute without error.

File Input:name.DAT - CONTIRR input data filename.SNR - TGTGEN sensor data filename.TGT - TGTGEN target data filename.TP5 - LOWTRAN TAPE5 data filetgt-sig - target signature file

File Output:name.FFL - SPIRCADE detection data file (formatted)name.UFL - SPIRCADE detection data file (unformatted)

Syntax:TGTBAT name<ENTER>

wherename - file identifier (without extensions) for CONTIRR, LOWTRAN, and TGTGEN data files

Example:TGTBAT d261<ENTER>

6.6 TGTDET

TGTDET generates target detection data for SPIRCADE signal processing analyses based on LOWTRAN / CONTIRR atmospheric propagation analyses. See Section 2.0 .

File Input:name.PRN - CONTIRR irradiance output filename.SNR - TGTGEN sensor data filename.TRJ - TGTGEN auxiliary trajectory data filename.TP5 - LOWTRAN TAPE5 data file

File Output:name.FFL - SPIRCADE detection data file (formatted)name.UFL - SPIRCADE detection data file (unformatted)

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Syntax:TGTDET name<ENTER>

wherename - file identifier (without extensions) for CONTIRR, LOWTRAN, and TGTGEN data files

Example:TGTDET d261<ENTER>

6.7 TGTTRJ

TGTTRJ generates target trajectories for LOWTRAN program runs and SPIRCADE signal processing analyses. The SPIRCADE detection data files produced are based on ALRRI / ALPHA parameters supplied in the target input data file. See Section 2.0 .

File Input:name.SNR - TGTGEN sensor data filename.TRJ - TGTGEN auxiliary trajectory data filename.TP5 - LOWTRAN TAPE5 data file

File Output:name.TRJ - TGTGEN auxiliary trajectory data fileRname.FFL - SPIRCADE detection data file (formatted)Rname.UFL - SPIRCADE detection data file (unformatted)Rname.TP5 - LOWTRAN TAPE5 data file

Syntax:TGTTRJ name<ENTER>

wherename - file identifier (without extensions) for LOWTRAN and TGTGEN data files

Example:TGTTRJ d261<ENTER>

7.0 ADDITIONAL COMMANDS

This section lists additional commands which may be useful in conducting TGTGEN / LOWTRAN / CONTIRR / SPIRCADE analyses.

CONCHG - modifies a CONTIRR data file then runs CONTIRRLOWATM - updates atmospheric data in a LOWTRAN TAPE5 fileLOWHS - inserts a new sensor height into a LOWTRAN TAPE5 fileLOWHT - inserts a new target height into a LOWTRAN TAPE5 fileLOWRHI - limits range in a LOWTRAN TAPE5 R-fileLOWRNG - inserts incremental ranges in a LOWTRAN TAPE5 R-fileLOWRTB - builds LOWTRAN TAPE7 T-files and B-files

For each command, a brief description is given along with file input and output names, syntax and a command example. To execute the software, the command is entered at the MS-DOS prompt in the directory of the data files.

7.1 CONCHG

CONCHG changes root names of LOWTRAN TAPE7 & CONTIRR output files in the CONTIRR.DAT file,

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then runs CONTIRR. This command is useful in CONTIRR runs in which parameters in CONTIRR.DAT remain constant except for the LOWTRAN TAPE7 and CONTIRR output files. In modifying the file names, the file extensions and single letter prefixes of the LOWTRAN files are preserved. The extension of the CONTIRR output file is also preserved. The remaining portion of the filenames incorporate the new file designation.

File Input:name1.DAT - CONTIRR input data fileTname2.TP7 - LOWTRAN TAPE7 target output fileBname2.TP7 - LOWTRAN TAPE7 background output filetgt-sig - target signature file

File Output:name2.PRN - CONTIRR irradiance output file

Syntax:CONCHG name1 name2<ENTER>

wherename1 - file identifier (without extensions) for the CONTIRR data filename2 - file identifier (without prefixes or extensions) for LOWTRAN and CONTIRR data files

Example:CONCHG d261 d262<ENTER>

7.2 LOWATM

LOWATM merges atmospheric profile data with a LOWTRAN TAPE5 file. The atmospheric data file has a special format which facilitates input from Naval Sea Weapon Systems Engineering Station (NSWSES) test data records and is identified by file extension “ATM”. See Section 8.0 for file format.

File Input:name.TP5 - LOWTRAN TAPE5 data filename.ATM - Atmospheric data file

File Output:name.TP5 - LOWTRAN TAPE5 data file

Syntax:LOWATM name<ENTER>

wherename - file identifier (without extensions) for LOWTRAN and atmospheric data files

Example:LOWATM d261<ENTER>

7.3 LOWHS

LOWHS inserts a new sensor height into a LOWTRAN TAPE5 file. The new height is assumed constant and appears in each Card 3 occurrence of the file. In the command syntax, the file name is identified first, followed by the height, and units of the height. If no units are specified, kilometers are assumed. The units are designated by one of the following abbreviations:

cm - centimeter m meterin - inch mi mile

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km - kilometer nm nautical mile



Syntax:LOWHS name height units<ENTER>

wherename - file identifier (without extensions) for the LOWTRAN data fileheight - numeric value of sensor height (units)units - abbreviation of units for sensor height

Example:LOWHS d261 100 ft<ENTER>

7.4 LOWHT

LOWHT inserts a new target height into a LOWTRAN TAPE5 file. The new height is assumed constant and appears in each Card 3 occurrence of the file. In the command syntax, the file name is identified first, followed by the height, and units of the height. If no units are specified, kilometers are assumed. The units are designated by one of the following abbreviations:

cm - centimeter m meterin - inch mi milekm - kilometer nm nautical mile



Syntax:LOWHT name height units<ENTER>

wherename - file identifier (without extensions) for the LOWTRAN data fileheight - numeric value of target height (units)units - abbreviation of units for target height

Example:LOWHT d261 500 ft<ENTER>

7.5 LOWRHI

LOWRHI omits Card 3 entries of a LOWTRAN TAPE5 file whose ranges are above a user-specified limit. This command can be used to eliminate LOWTRAN run errors generated from ranges which extend beyond and below the horizon. In the command syntax, the file name is identified first, followed by the maximum range, and units of the range. If no units are specified, kilometers are assumed. The units are designated by one of the following abbreviations:

cm - centimeter m meterin - inch mi mile

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km - kilometer nm nautical mile



Syntax:LOWRHI name range units<ENTER>

wherename - file identifier (without extensions) for the LOWTRAN data filerange - maximum range for geometry data (units)units - abbreviation of units for range value

Example:LOWRHI d261 10 km<ENTER>

7.6 LOWRNG

LOWRNG inserts incremental range values into a LOWTRAN TAPE5 file. The range starts at a user-specified start value and increases / decreases with each succeeding Card 3 entry until the second range value is surpassed. Card 3 entries in the file are added or deleted to accommodate the range increments. In the command syntax, the file name is followed by the range start, range end, range increment, and units of the range values. If no units are specified, kilometers are assumed. The units are designated by one of the following abbreviations:

cm - centimeter m meterin - inch mi milekm - kilometer nm nautical mile



Syntax:LOWRNG name start end delta units<ENTER>

wherename - file identifier (without extensions) for the LOWTRAN data filestart - initial range value to increment from (units)end - terminal range value to increment to (units)delta - incremental value for range to increase / decrease (units)units - abbreviation of units for range values

Example:LOWRNG d261 5 20 4 mi<ENTER>

7.7 LOWRTB

LOWRTB executes the correct series of commands to create target and background LOWTRAN TAPE7 files for CONTIRR Program analysis. LOWTRAN TAPE6 files are automatically deleted.

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File Input:Rname.TP5 - LOWTRAN TAPE5 range data file

File Output:Tname.TP5 - LOWTRAN TAPE5 target data fileBname.TP5 - LOWTRAN TAPE5 background data fileRname.TP7 - LOWTRAN TAPE7 range output fileTname.TP7 - LOWTRAN TAPE7 target output fileBname.TP7 - LOWTRAN TAPE7 background output file

Syntax:LOWRTB name<ENTER>


Example:LOWRTB d261<ENTER>

8.0 ATMOSPHERIC PROFILE FILE FORMAT

For NAVSWC LOWTRAN runs (especially those simulating Naval Sea Weapon Systems Engineering Station (NSWSES) sensor testing), atmospheric profile data is basically derived from two different sets of sources. All molecular amounts (except for that of water) are taken from pollution monitoring instruments, whereas temperature, pressure, and relative humidity are from weather balloon data. The pollution readings are ground level measurements extrapolated to specific heights in the atmospheric profile. Weather balloon data are readings sampled at different heights as a weather balloon rises. This data gives an indication of atmospheric properties as a function of altitude. In most cases, if a value in the atmospheric profile is not known, the default value for the standard atmospheric model is used. More information concerning atmospheric profile definitions can be found in Reference [2] .

The software command LOWATM constructs a LOWTRAN TAPE5 data file based on the above information which is compiled in an atmospheric profile data file. The atmospheric profile is read by the program; the data is processed, then merged into a LOWTRAN TAPE5 file. In Card 1 of the LOWTRAN TAPE5 file, the value of variable MODEL is set at “7”; the value of variable IM is set at “1”. Card 2C is added or modified to incorporate the number of atmospheric profile layers and title information. Card 2C1, 2C2A, and 2C2B are added as necessary to define the molecular amounts on each layer.

The atmospheric profile data file is in three sections: (1) Title Information, (2) Molecular Amounts, and (3) Altitude Profile. These sections appear in the file in the above order. Each data section has a different format. In any of the sections, if the first character of the line is an asterisk “*”, the line is ignored and can be used for comments.

(1) Title Information: The first section gives the data title which appears on Card 2C of the LOWTRAN TAPE5 run file. The text is read from the first column and is limited by LOWTRAN to 72 characters.

(2) Molecular Amounts: The second section identifies molecular amounts which remain constant in the atmospheric profile models. The molecular amount is given first, followed by the zero calibration measure of the instrument, units of measure and molecular type. Any information following the last entry is ignored and can be considered a comment. The molecular types can occur in any order. End of data for molecular amounts is designated by “-1”.

Units of measure for molecular amounts are abbreviated as follows:

ppb - parts per billion

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pphm - parts per hundred millionpptm - parts per ten millionppm - parts per million

Molecular types are abbreviated as follows:

CO - carbon monoxideCO2 - carbon dioxideCH4 - methaneHNO3 - nitric acidN2O - nitrous oxideNH3 - ammoniaNO - nitric oxideNO2 - nitrogen dioxideNOX - nitrogen oxidesO2 - oxygenO3 - ozoneSO2 - sulfur dioxide

If the molecular amount of “NOX” is entered, the following equation is used to derive one of the amounts of “NO” or “NO2”, provided the other amount is supplied.

NOX = NO + NO2

In the software, quantitative altitudes to which the ground level molecular measurements are extrapolated are:

Ground-level molecular amount of O3 up to @@@ kilometers altitudeGround-level molecular amount of CO up to @@@ kilometers altitudeGround-level molecular amount of NO up to @@@ kilometers altitudeGround-level molecular amount of NO2 up to @@@ kilometers altitude

Unless the molecular amount for CO2 is specified, the default value is @@@ per million, which is held constant throughout the atmospheric profile altitudes.

(3) Altitude Profile: The third section identifies the atmospheric profile information which is derived from meteorological balloon data. This data consists of altitude, temperature, pressure, and relative humidity. On each data line, altitude is given first, followed by temperature, pressure, and relative humidity. Altitude must be given in units of feet, temperature in units of Celsius, pressure in millibars, and water in percent relative humidity. The data should be given in order of ascending altitude with the lowest altitude listed first. LOWTRAN limits the number of profile entries to @@@. End of data for the profile is in indicated by “-1”.

Example Atmospheric Profile Data Format

[Start of File]

BLANKED

[End of File]

9.0 REFERENCES

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[1] “SPIRCADE Target Generator User's Guide”, NSWC White Oak Division Internal Report, White Oak, Maryland.

[2] Kneizys, F.X. et al, "Users Guide to LOWTRAN 7", U.S. Air Force Technical Report AFGL-TR-88-0177, 16 August 1988.

[3] Rudzinsky, M.R., “Directions for Calculating IRST Sensor Performance Using the LOWTRAN 7 and CONTIRR Models”, NSWC Dahlgren Division Internal Report, Dahlgren, Virginia, 10 September 1990.

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10.0 INDEX

application of software.........................................0 3 ATM file name extension......................................20atmosphere..............................................................

background irradiance....................................14foreground irradiance.....................................14horizon due to refraction.................................06spectral transmission......................................14

atmospheric profile data..........................................from NSWSES................................................20from weather balloons....................................20using LOWATM...............................................17using LOWTRAN TAPE5 file format...............10

B* file name prefix................................................0 9 changing..................................................................

root names of output files...............................16sensor height..................................................17target height....................................................18

CONCHG command description..........................16CONTIRR command description.........................13DAT file name extension......................................13defining atmospheric data....................................10defining sensor........................................................

data................................................................12height..............................................................12rotation rate....................................................12spectral window..............................................11threshold for target detection..........................12

defining target..........................................................data................................................................10radiating area..................................................10signature.........................................................10spectral radiance............................................10trajectory data.................................................12trajectory with incremental ranges..................19

deleting target ranges outside a maximum..........18determining target....................................................

atmospheric transmission...............................10background irradiance....................................10blockage by horizon........................................06contrast irradiance..........................................13detection from sensor threshold.....................15foreground irradiance.....................................10trajectory based on refracted angles..............14

end product..........................................................03entering NSWSES atmospheric data...................17entering target trajectory based on range............11FFL file name extension.......................................0 9 file naming...............................................................

convention......................................................0 9 example..........................................................0 9

final output files for SPIRCADE detection data....03improvement for SPIRCADE applications............03initial input files........................................................

atmospheric data............................................10CONTIRR DAT................................................11LOWTRAN TAPE5..........................................10sensor data.....................................................12target spectral signature data.........................10target trajectory data.......................................12TGTGEN.........................................................10

input data file formats..............................................CONTIRR data...............................................13LOWATM atmospheric data............................20LOWTRAN TAPE5 data..................................10target signature...............................................10TGTGEN auxiliary trajectory data...................12TGTGEN sensor data.....................................12TGTGEN target data.......................................11

input files in procedure.........................................06ISMI.........................................................................

definition.........................................................0 3 purpose..........................................................0 3 support organizations.....................................0 3

LOWATM command description..........................17LOWHS command description.............................17LOWHT command description.............................18LOWR2T command description...........................14LOWRHI command description...........................18LOWRNG command description..........................19LOWRTB command description..........................19LOWT2B command description...........................14LOWTRAN command description........................14methodology for software application..................03NAVSWC.................................................................

Dahlgren usage..............................................0 3 White Oak usage............................................0 3

NSWSES atmospheric data application...............20output files in procedure......................................06PRN file name extension.....................................0 9 R* file name prefix...............................................0 9 references............................................................21sample execution.................................................06sensor......................................................................

height..............................................................12rotation rate....................................................12spectral window..............................................13threshold for target detection..........................12

SNR file name extension.....................................12SPIRCADE program description..........................03support software..................................................03

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T* file name prefix................................................0 9 target.......................................................................

atmospheric transmission...............................14background irradiance....................................14blockage by horizon from refraction................06contrast irradiance..........................................13detection from sensor threshold.....................15foreground irradiance.....................................14radiating area..................................................10signature.........................................................10spectral radiance............................................10trajectory based on refracted angle................06trajectory data.................................................11

trajectory with incremental ranges..................19TGT file name extension......................................11TGTBAT command description............................15TGTDET command description...........................15TGTGEN program description.............................03TGTTRJ command description............................16TP5 file name extension......................................10TP6 file name extension......................................0 9 TP7 file name extension......................................0 9 TRJ file name extension......................................12UFL file name extension......................................0 9 weather balloon data...........................................20

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Documents

User's Guide for the Infrared Sensor Modeling Interface (ISMI)jefgeorge.com/Reports/hlpISMI.pdfUSER'S GUIDE FOR THE INFRARED SENSOR MODELING INTERFACE (ISMI) ... Technical Revision: