Weather-Impact Decision Aids Software to Help Plan by ekr11098


									               Weather-Impact Decision Aids: Software to
           Help Plan Optimal Sensor and System Performance
Dr. Richard C. Shirkey                                                                                                                     Melanie Gouveia
Army Research Laboratory                                                                                                                  Northrop Grumman
                Weather can play a decisive role in military battles, in their planning, and in their execution. Weather-impact decision aids
                give the commander an edge by allowing both a determination of the optimum selection of weapon systems and a comparison
                with threat systems under current or forecast weather. This article describes two weather-tactical decision aids: the Integrated
                Weather Effects Decision Aid and the Target Acquisition Weapons Software.

W      eather is ubiquitous; planning for it is
       an everyday occurrence, yet it still
manages to foul up our plans. Recent mili-
                                                      and threat) has its list of relevant rules,
                                                      which include red-amber-green (unfavor-
                                                      able-marginal-favorable) critical value thresh-
                                                                                                             map overlays (see Figure 3, page 18) for the
                                                                                                             region of interest. Environmental data for
                                                                                                             the region of interest is supplied primarily
tary examples abound, such as dust clouds             olds for one or a combination of the envi-             via the Army’s Battlescale Forecast Model
that grounded sorties in Operation Allied             ronmental parameters that affect the sys-              [2], developed for short-range forecasting.
Force in Kosovo. To effectively execute               tem. Results are displayed via a matrix of             The environmental impact rules and critical
missions, the military commander must be              impacts vs. time (see Figures 1 and 2) and             values for the various systems have been
aware of the weather and its impact on                Figure 1: IWEDA Weather Effect Matrices
his/her equipment, personnel, and opera-
tions. There are a number of weather-
impact decision aids (WIDAs) that deter-
mine weather effects on mission-selected
equipment and operations. Generally, these
WIDAs may be broken into two subsets:
rule-based and physics-based.
    Rule-based WIDAs, such as the Army’s
Integrated Weather Effects Decision Aid
(IWEDA) [1], are constructed using
observed weather impacts that have been
collected from field manuals, training cen-
ters and schools, and subject matter experts.
IWEDA provides information (in the form
of stoplight charts) concerning which
weapon systems will work best under fore-
cast weather conditions; no information is
provided concerning target acquisition
    Physics-based tactical decision aids
(TDAs), such as the Tri-Service Target
Acquisition Weapons Software (TAWS) [2],
employ physics calculations that have their           Figure 2: IWEDA Full Impacts
basis in theory and/or measurements.
TAWS determines the probability of detect-
ing a given target at a given range under
existing or predicted weather conditions.
Thus, physics-based systems produce
results in terms of a performance metric
that take on a continuum of values rather
than the simpler stoplight results from the
rule-based systems.

IWEDA, a UNIX-based program written in
Java, is a collection of rules with associated
critical values for aiding the commander in
selecting an appropriate platform, system,
or sensor under given or forecast weather
conditions. It provides qualitative weather
impacts for platforms, weapon systems, and
operations, including soldier performance.
     Each system (Army, Air Force, Navy,

December 2002                                                                                                                      17
Software Engineering Technology

                                                             causes a significant (moderate or severe)         systems, their subsystems, and components.
                                                             impact on a military operation, system, sub-      Results are presented as a function of time
                                                             system, or personnel.                             and location.
                                                                 In general, the rules are determined by           To construct the example mission, the
                                                             operational usage (as embodied in the field       A-10, AH-64, personnel, SA-14, and SA-16
                                                             manuals, etc.), whereas the critical values are   systems were selected from IWEDA’s friend-
                                                             determined by doctrine, safety, or engineer-      ly and threat graphical user interfaces (GUI).
                                                             ing factors (people, modeling, or testing).       Once these systems have been selected,
                                                             Currently IWEDA stores information on             IWEDA determines the weather impacts
                                                             102 systems, 86 of which are friendly, 16 of      on the mission; results are presented to the
                                                             which are threat-rated.                           user in the form of a WEM, as shown in
                                                                                                               Figure 1.
                                                             IWEDA Operational Usage                               Initially, the lower half of the WEM is
                                                             IWEDA is arranged in a fashion that pres-         blank with the upper half showing the
                                                             ents systems, subsystems and components           weather impacts as a function of system(s)
                                                             in a hierarchal fashion. A group of systems       and time. By performing a right click on any
Figure 3: IWEDA Map Overlay for AH-64                        is called a mission; a system often contains      of the colored cells, such as the AH-64 for
TADS TV/DVO                                                  one or more subsystems; the subsystems            22/12 (day/time), condensed impacts are
                                                             often have one or more components. The            shown in a scrollable window in the lower
validated through the Training and                                                                             half of the WEM (impacts for the config-
                                                             user has the option to define which systems
Doctrine Command’s organizations, field                      belong to a mission and to delete optional        ured AH-64 system have been reproduced
manuals and the National Ground and                          subsystems and components from a system           in Table 1). The WEM shows impacts on
Intelligence Center.                                         thereby allowing a determination of weath-        the AH-64 system as a function of time and
     IWEDA is currently being fielded as                     er impacts from operations or missions at         general environmental conditions, but we
part of the Army’s Command, Control,                         the highest level down to systems, subsys-        do not know the full (detailed) impact or
Communications, Computers and Intelli-                       tems, and components at the lowest level.         where the impact is occurring within the
gence (C4I) tactical weather system, the                          For missions, systems, subsystems, and       forecast area.
Integrated Meteorological System. As a C4I                   components, the impacts over the forecast             To determine the full impact statement
tool, IWEDA does not dictate a course of                     period are shown on weather effects matri-        and the location, a left mouse click is per-
action, but only informs the commander                       ces (WEMs, see Figure 1). The WEM is              formed on the AH-64 cell for the selected
that there will be weather impacts on the                    color-coded; for use with non-color print-        day of the month and time, i.e., 22/12. This
force (friendly or threat).                                  ers, cells are annotated with R (red), A          brings up the next screen (see Figure 2) that
     IWEDA rules, which interact with the                    (amber), or G (green). Red areas indicate         presents all of the selected AH-64 subsys-
weather database to determine impacts on                     that operations are severely impacted: There      tems and components and their color-
the selected system(s), are determined from                  is either a total or severe degradation or the    coded impacts.
system concepts and are embodied in a                        operational limits or safety criteria have            As in the WEM GUI, initially only the
computer database that has been tied to crit-                been exceeded. Amber indicates that opera-        top half of Figure 2 is presented to the user.
ical values. The critical values are defined, in             tions are marginal and the operational capa-      To obtain further information, the user
a meteorological sense, as those values of                   bility is degraded, or there is a marginal        clicks on one of the colored blocks; in the
weather factors that can significantly reduce                degradation. Green indicates that there are       example presented, the TV/direct view
the effectiveness of, or prevent execution                   no operational restrictions.                      sight component of the Target Acquisition
of, tactical operations and/or weapon sys-                        Based on requirements, users may query       Designation Sight (TADS) has been inter-
tems.                                                        and view various levels of information: text      rogated. This results in a color-coded map
     An example of such a rule would be                      impact statements or spatial distributions of     overlay (Figure 3) showing where the
“usage of TOW2 is not recommended for                        impacts on a map overlay.                         TV/D is affected by the weather. The full
visibilities less than three kilometers.” In                                                                   impact statement, along with its source, can
this example rule, a visibility of three kilo-               IWEDA Example                                     now be obtained by moving the cursor
meters (the critical value) has been coupled                 In the following example, a user-defined          (shown as a white circle) and clicking upon
with a system (TOW2) resulting in a rule.                    mission is created by selecting three friend-     a white area on the map (upper left of cen-
We can further define this critical value, or                ly and two threat systems. Once the mission       ter).
range of values, as the point where the                      has been configured, the database is queried          The associated full impact statement
occurrence of a meteorological element                       to determine the weather impacts on the           then appears in the lower half of Figure 2,
                                                                                                               which in this case is “Any occurrence of fog
Table 1: Impacts for the AH-64 System for 22/12                                                                or visibility <1.9 mi (3100m) significantly
 System AH-64 has marginal impact: High Pressure Altitude                                                      reduces the target and background contrast
 Subsystem 30 MM MACHINE GUN has marginal impact: Low Visibility                                               making target acquisition difficult.”
 Component THERMAL SIGHT has marginal impact: Reduced Visibility                                               Contrast this with the condensed impact
 Component TV/DIRECT VIEW SIGHT has marginal impact: Reduced Visibility                                        statement of “Fog and Low Visibility”
 Component TV/DIRECT VIEW SIGHT has unfavorable impact: Fog and Low Visibility                                 shown in the WEM.
 Component Laser R/D has marginal impact: Reduced Visibility                                                       In summary, the colored cells in the
 Component Laser R/D has unfavorable impact: Low Visibility                                                    WEM display the worst-case condition for the
 Subsystem HELLFIRE has marginal impact: Icing Aloft                                                           selected mission, during the selected time, for
 Subsystem GENERATOR has marginal impact: High Altitude                                                        the entire forecast region. If the user wishes to
 Component NIGHT VISION GOGGLES has unfavorable impact: Reduced Illumination                                   know why a particular cell is red or amber,

18   CROSSTALK The Journal of Defense Software Engineering                                                                                         December 2002
                                                             Weather-Impact Decision Aids: Software to Help Plan Optimal Sensor and System Performance

further information is available in impact       position), contrast at visible wavelengths,        by the Multi-Service Electro-optic Signature
statements, which explain why a particular       C(0), is the difference between the target,        model (MuSES) [6], which calculates the
cell exists. Detailed analysis for the impact-   It , and background, Ib, radiances, divided        equilibrium background and target temper-
ed system or sensor can be obtained from         by the background radiance,                        atures using antecedent illumination and
the color-coded map.                                                                                weather data.
                                                     C(0) = [It(0) — Ib(0)]/Ib(0).          (1)         MuSES has two primary components: a
The TAWS                                                                                            thermal analyzer module and a signature
TAWS [3], a GUI-based program running            We may express the apparent contrast at            model. Thermal analysis is the computation
under the Windows operating system, is a         range r as                                         of physical temperature and heat rates that
Tri-Service program that includes Air                              C(0)                             are obtained through energy balance on a
Force, Army, and Navy sensors and targets.       C(r) = ___________________ ,                       node or isothermal element using a finite-
TAWS supports systems in three regions of                1+[ Ip(r)/Ib(0)][ 1/T(r)]          (2)     difference numerical solution of the differ-
the spectrum: visible (0.4 - 0.9 microns),                                                          ential equations. The main output of a ther-
laser (1.06 microns), and infrared (IR) (3-5     where T(r) is the atmospheric transmission,        mal model is physical temperatures and net
microns; 8-12 microns). It accepts current       and Ip is radiation scattered from atmos-          heat rates that compare to empirical meas-
or forecast weather data to determine target     pheric aerosols and gases into the line-of-        urements of contact sensors.
detection range for selected sensors and tar-    sight. Ip is called the path radiance and may          The signature analysis is the computa-
gets. The commander uses this information        be thought of as atmospheric noise scat-           tion of apparent temperature or radiance,
for mission-planning purposes or to ascer-       tered into the sensor’s field of view; it is not   which is composed of an emitted compo-
tain which sensors can see the furthest          dependent upon the target.                         nent that is a function of physical tempera-
under the given weather conditions.                  In TAWS at visible wavelengths, the tar-       ture and emissivity and a reflected compo-
    TAWS performs both illumination and          get and background radiances are deter-            nent that is a function of irradiance from its
performance prediction calculations (PPC).       mined using Hering and Johnson’s Fast              surroundings and its reflectivity. In other
The PPC can be done for single or multiple       Atmospheric SCATtering model (FASCAT)              words, the signature is what a sensor views
locations during a mission. The illumination     [4], which calculates upwelling and down-          and measures the radiance of a target,
analysis involves the computation of solar       welling radiance terms at specified heights        which is only partially dependent on its
and lunar ephemeris information for a spec-      in the atmosphere.                                 physical temperature. Thus, the signature
ified location. A mission planner, for exam-         For designated sensor and target alti-         model provides a link between the output
ple, might be interested in an illumination      tudes, the apparent contrast is calculated for     of the thermal model and the desired out-
analysis to determine the time of sunset for     slant paths, which may include an optional         put in signature analyses.
a particular mission date and location. For a    cloud layer. Objects in sunlight or shadow             The basic heat source components con-
single location, the PPC could be used to        may be viewed against sky, cloud, or terrain       sidered by MuSES include longwave radia-
predict detection range for a particularly       backgrounds. The path radiance Ip, and the         tion, solar absorption, engine heating,
important target as a function of time,          background radiance Ib, are determined by          engine compartment air, exhaust gas, track
while a PPC for multiple locations along a       a multiple scattering calculation using the        and wheel heating, and convection. Inter-
mission route would be useful to a mission       delta-Eddington approximation [5] in con-          reflections between diffuse surfaces are also
planner predicting detection ranges for a        junction with the atmospheric model. The           taken into consideration. These various
series of key locations as a function of time.   contrast is subsequently determined using          temperatures and effects are used to calcu-
    To determine the acquisition range to a      equation (2).                                      late ∆T.
given target a number of quantities need to          For visible/near-IR scenarios, the target
be known: the target-to-background con-          may be on the ground or elevated. An ele-          Laser Contrast Model: The laser model
trast, the atmospheric conditions, solar or      vated target may be viewed with an upward          does not compute contrast.
lunar luminance, and sensor characteristics,     or downward line-of-sight (LOS). Sky and
all of which vary with spectral region. We       cloud backgrounds are supported for the            Atmospheric Information
discuss each of these in the following sec-      upward LOS; distant earth and low-lying            To determine the loss of energy as radiation
tions and provide an illustrative example at     cloud backgrounds are supported for the            passes through the atmosphere requires
the end.                                         downward LOS.                                      knowledge of the atmospheric constituents
                                                                                                    (gases and aerosols) and its state (pressure,
Target-to-Background Contrast                    Thermal Contrast Model: The inherent               temperature, relative humidity, etc.). This
Contrast is defined as the ability of an         contrast at thermal wavelengths is defined         loss of energy is expressed in the form of
observer to distinguish an object from its       as the target temperature minus the back-          atmospheric transmission, which ranges in
background; it degrades as the atmospheric       ground temperature,                                value from zero to one and is highly
path length increases. At visible wave-                                                             dependent upon the aerosol type present.
lengths, where radiation scattering from             C(0) = [It(0) — Ib(0)] = ∆T,           (3)     This loss of energy can be represented by
atmospheric particulates is important, the                                                          Beer’s law for atmospheric transmission,
mathematical formulation of the contrast is      where ∆T is the temperature difference
different than in the infrared (IR), where       between the target and background. Note                 T(r) = e- (ka + kp + km) r,                    (5)
emission is the dominant process. Since          that as the temperature increases, so will the
TAWS computes contrast in both of these          inherent radiance, I(0). Thus, the contrast in     where ka, kp, and km are the aerosol, pre-
spectral regions, we present the following       the IR is,                                         cipitation, and molecular extinction coeffi-
formulations.                                                                                       cients, respectively. The molecular extinc-
                                                     C(r) = C(0) T(r) = ∆T T(r).            (4)     tion coefficients are determined in TAWS
Visual Contrast Model: The inherent, or                                                             by using a scaled down version of the low
zero range (usually defined as the target’s          In TAWS, C(0) is determined indirectly         transmission atmospheric propagation code

December 2002                                                                                                               19
Software Engineering Technology

 Aerosol                     Properties                                                                      ible and infrared spectral bands. Ranges and
 Rural                       Boundary layer background aerosol found in continental air masses.              probabilities predicted by the model repre-
 Urban                       Rural aerosol plus an added component representing soot-like                    sent the expected performance of an
                             aerosols that include particles produced in urban and industrial                ensemble of trained military observers with
                             complexes.                                                                      respect to an average target having a speci-
 Maritime                    Characterizes aerosols that include sea-salt particles; the target area
                             is more than a few kilometers inland.
                                                                                                             fied signature and size. TAWS currently
 Tropospheric                Characterizes aerosols found in very clean air masses and in the free           only supports detection ranges; other acqui-
                             atmosphere above the boundary layer.                                            sition ranges are scheduled to be added in
 Desert                      Characterizes aerosols found in the boundary layer of desert, arid, or          the near term.
                             semi-arid climatic regions.                                                          TAWS supports two different classes of
 Navy Maritime               Describes aerosols found in the boundary layer of oceanic                       systems that employ laser designators oper-
                             environments; includes wind speed dependence.                                   ating at 1.06 microns: laser ranging and laser
 Advective Fog               Characterizes wet aerosols found in dense fogs, where visibility is
                             less than 1 km.
                                                                                                             lock-on systems. Each of these has designa-
 Radiative Fog               Describes aerosol properties in less dense fogs, where visibility is 1 km       tor and receiver components. The airborne
                             or greater.                                                                     laser ranging systems measure the distance
 Camouflage Smokes           Characterizes white phosphorus, fog oil, and hexachloroethane                   from the ranger system to the target by
                             smoke.                                                                          measuring the travel time of the laser pulse
 Battlefield Induced         A persistent pall of smoke and dust that sometimes covers areas                 from the designator to the target and from
 Contaminants (BIC)          where intense combat has occurred.
                                                                                                             the target to the receiver. The designator
Table 2: TAWS Aerosol Models                                                                                 and receiver are physically collocated in the
LOWTRAN [7]. The aerosol extinction                          itation type/rate; surface aerosol type; bat-   same hardware package for all ranging sys-
coefficients [8, 9] are read from pre-calcu-                 tlefield induced contaminants; high-, mid-,     tems. For the laser lock-on weapons, the
lated internal tables.                                       and low-level clouds*; and the boundary         designator illuminates the target and the
    TAWS contains 10 aerosol and two pre-                    layer height.                                   receiver receives the reflected beam. TAWS
cipitation models that are used in various                                                                   predicts the maximum effective range for
combinations by the IR, television/night                     Solar/Lunar Illumination                        either the designator or lock-on receiver.
vision goggles, and laser models to deter-                   Illumination analysis in TAWS involves the
mine the appropriate aerosol and/or pre-                     computation of solar and lunar ephemeris        Example
cipitation extinction coefficients. The                      data for a specified location and a series of   We present here a winter scenario using a T-
aerosols describe the primary particulates of                dates or times. Solar/lunar ephemeris input     80 Soviet main battle tank in exercised and
the air mass close to the surface at the loca-               information is derived from user-input time     off modes, against a snow background at
tion of interest. The naturally occurring                    of day/time of year and latitude/longitude,     IR wavelengths. The sensor and tank were
aerosols include rural, urban, maritime, tro-                in conjunction with the Solar-Lunar             aligned such that the sensor always had a
pospheric, desert, advective fog, radiative                  Almanac Code [10].                              frontal view of the tank; the sensor height
                                                                                                             was 10 feet. The date and location were
fog, and Navy maritime. There are three                           The solar/lunar ephemeris information
                                                                                                             fixed at 21 December, latitude 37° 32’ N,
types of camouflage smokes: white phos-                      is also computed and used for target acqui-
                                                                                                             longitude 127° 00’ E (Seoul, S. Korea),
phorus, fog oil, and hexachloroethane. A                     sition analysis. In this case, in conjunction
                                                                                                             respectively. The weather conditions were
10th aerosol, in the form of battlefield                     with variable cloud cover, the solar/lunar
                                                                                                             overcast and snowing with visibilities of
induced contaminants, is available for situa-                position is used to calculate target/back-
                                                                                                             three miles (light snow) and one mile (heavy
tions where there is a persistent pall of                    ground heating for the IR model and inher-
                                                                                                             snow) with a light breeze (~3m/s) from the
smoke and dust raised by combat.                             ent target/background radiance for the vis-
                                                                                                             west. The relative humidity and tempera-
Properties of the aerosol models are pre-                    ible model. The laser model does not use
                                                                                                             ture, taken from a climatological database
sented in Table 2. TAWS also contains rain                   ephemeris information.                          [12], as a function of local time are present-
and snow precipitation models.                                                                               ed in Table 3.
    TAWS allows a wide range of meteoro-                     Sensor Information                                   The results of the model run are shown
logical conditions, all of which may be                      Sensors are user-selected once the spectral     in Figure 4. The two vertical lines, deter-
selected by the user and some of which may                   region has been chosen. The relevant sensor     mined using the illumination analysis capa-
be automatically input via the Air Force                     curve is automatically retrieved from the       bility of TAWS, indicate the sunrise and
Weather Agency (AFWA) or the Navy                            sensor database.                                sunset times. As expected, the detection
Tactical Environmental Data Server                               Within TAWS, target detection range         range is considerably larger when the visi-
(TEDS). These meteorological parameters                      for Silicon TeleVision (TV), night vision       bility is higher; for given weather conditions
include the following (those values noted                    goggles (NVG), and IR sensors is deter-         the exercised tank is easier to detect relative
with an asterisk may be downloaded from                      mined by using the Acquire sensor per-          to the tank in the off state.
AFWA or TEDS): atmospheric dewpoint                          formance model [11]. Acquire predicts tar-           Thermal crossover, defined as the time
temperature*; sea surface temperature*;                      get detection and discrimination range per-     during the day when the thermal contrast is
wind velocity/direction*; visibility*; precip-               formance for systems that image in the vis-     at a minimum and the polarity of the con-
Table 3: Input Relative Humidity (RH) (%) and Temperature (°C) as a Function of Time (HRS)                   trast reverses, generally occurs at mid-
                                                                                                             morning and late afternoon. For example,
 Time           1800    2100     0000     0300     0600       0900    1200   1500    1800    2100   0000
                                                                                                             in early morning the background tempera-
                                                                                                             ture may be greater than the target temper-
 Temp               1      -3       -3        -5      -5          0      0       1       1     -3     -3     ature. After thermal crossover, the target
                                                                                                             temperature may be greater than the back-
                   69      74       74       86       86         80     80      69     69      74     74
 RH                                                                                                          ground temperature. In the example, ther-

20   CROSSTALK The Journal of Defense Software Engineering                                                                                      December 2002
                                                             Weather-Impact Decision Aids: Software to Help Plan Optimal Sensor and System Performance

mal crossover occurs at approximately 0900            Software Products for Operational                                                                    Light snow, 3 mi visibility, Tank on
                                                                                                                                                           Light snow, 3 mi visibility, Tank off
and 1700, accounting for the low detection            Weather Support. Proc. of the                                                                        Heavy snow, 1mi visibility, Tank on
                                                                                                                                                           Heavy snow, 1 mi visibility, Tank off
range at those times. The commander/user              Battlespace Atmospheric and Cloud                         5

can now optimize assets by choosing a time            Impacts on Military Operations Con-
when detection range is maximized and by              ference. Fort Collins, CO, Apr. 2000.
avoiding those times such as when thermal        4.   Hering, W.S., and R.W. Johnson. The

crossover occurs, when detection ranges are

                                                                                                      Detection Range (km)
                                                      FASCAT Model Performance Under
at a minimum.                                         Fractional Cloud Conditions and                           3

    Using this information in conjunction
                                                      Related Studies No. 84-0168. University
with weather forecast information (as                 of California, Scripps Institution of                                        Sunrise

opposed to static information used in this            Oceanography. San Diego, CA, 1984.

example) provides additional relevant infor-     5.   Joseph, J.H., W.J. Wiscombe, and J.A.
mation. For example, let us examine the               Weinman. “The Delta-Eddington                             1
“tank on” curves in Figure 4. If the weath-           Approximation for Radiative Flux
er conditions were predicted to change                Transfer.” JAS Vol. 33: 2452.
from heavy to light snow at 1200 local, the      6.   Johnson, K., MuSES: A New Heat

detection range would increase from                   and Signature Management Design Tool
                                                                                                                             0       4       8      12
                                                                                                                                             Local Time (hrs)
                                                                                                                                                                16            20        24

approximately one and one-half kilometers             for Virtual Prototyping. Proc. Ninth
to approximately four and one-half kilome-                                                           Figure 4: Detection Range vs. Time
                                                      Annual Ground Target Modeling &
ters, providing the commander with an                 Validation Conference. Houghton, MI,              DAT.” ASL Technical Report 0160-3.
opportunity for increased detection. Such             Aug. 1998.                                        July 1986.
scenarios may also be used for                   7.   Kneizys, F.X., et. al. “Atmospheric           10. Bangert, J.A. Solar-Lunar Almanac
friendly/threat comparisons to determine              Transmittance/Radiance: Computer                  Code (SLAC) Software User’s Guide
the delta in range due to differing systems.          Code LOWTRAN 6.” Air Force                        Version 1.1. U.S. Naval Observatory,
                                                      Geophysics Laboratory Technical                   Astronomical Applications Depart-
Conclusions                                           Report 83-0187. Hanscom AFB, MA,
IWEDA provides the commander with an                                                                    ment, 1998.
easy-to-use and interpret tactical application        1983.                                         11. U.S. Army. Acquire Range Performance
that allows for near real-time evaluation of     8.   Shettle, E.P., and R.W. Fenn. “Models             Model for Target Acquisition Systems.
sensor employment options. Automating                 for the Aerosols of the Lower
                                                                                                        Version 1 User’s Guide. U.S. Army
the environmental parameter retrieval by              Atmosphere and the Effects of
                                                      Humidity Variations on Their Optical              CECOM Night Vision and Electronic
using a prognostic data set further enhances                                                            Sensors Directorate Report, Ft. Belvoir,
the application and allows for realistic plan-        Properties.” Air Force Geophysics
                                                      Laboratory Technical Report 79-0214.              VA, 1995.
ning based on evolving weather.
                                                      Hanscom AFB, MA, 1979.                        12. Avara, E., and B. Miers. “The
    TAWS aids the warfighter in determin-
ing what sensor/weapon system will work          9.   Shirkey, R. C., R. A. Sutherland, and M.          Climatology Model CLIMAT.” Army
best against a user-selected target under             A. Seagraves. “EOSAEL 84: Vol. 3,                 Research Laboratory Technical Report
adverse weather conditions. TAWS accom-               Aerosol Phase Function Database PFN-              273-8. Adelphi, MD, June 1998.
plishes this by using accepted sensor per-
formance and aerosol models coupled with                                          About the Authors
proven techniques for determining atmos-                         Richard C. Shirkey,                                           Melanie        Gouveia
pheric transmission and contrast. In addi-
                                                                 Ph.D, is a physicist with                                     manages the Weather
tion to determination of acquisition ranges,
TAWS may be used for mission planning                            the Army Research                                             Impact Decision Aid
and for determination of deltas between                          Laboratory’s Compu-                                           projects at Northrop
friendly and threat systems.                                     tational and Infor-                                           Grumman. She has
    Taken together, these TDAs provide the                       mation Sciences Direc-                                        worked in the areas of
commander a significant advantage for sys-        torate,   Battlefield     Environment                        atmospheric modeling and tactical
tem selection under adverse weather condi-        Division. He has worked in the area of                       decision aids for the past 12 years. She
tions.◆                                           atmospheric modeling and simulation                          is currently leading model improve-
                                                  for the past 23 years and is currently                       ment, graphical user interface develop-
References                                        engaged in atmospheric effects for tar-                      ment, and environmental data source
1. Sauter, D., and R. C. Shirkey. Target Ac-      get acquisition and their impacts on                         efforts for the Target Acquisition
   quisition Modeling with Automated              wargames.                                                    Weapons Software effort.
   Environmental Data Ingest for Weapon
   System Evaluation. Proc. of Ground                  US Army Research Laboratory                                               Northrop Grumman
   Target Modeling & Validation                        AMSRL-CI-EE                                                               Information Technology
   Conference. MI, Aug. 1999.                          White Sands Missile Range, NM                                             55 Walkers Brook Drive
2. Henmi, T., R. Dumais Jr. “Description               88002-5501                                                                Reading, MA 01867
   of the Battlescale Forecast Model.”
                                                       Phone: (505) 678-5470                                                     Phone: (781) 205-7202
   Army Research Laboratory Technical
                                                       Fax: (505) 678-4449                                                       Fax: (781) 942-2571
   Report 1032. White Sands Missile
   Range, NM, June 1997.                               E-mail:                                             E-mail: mgouveia@northrop
3. Gouveia, M.J., et. al. TAWS and NOWS:                                                                               

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