The Target Acquisition Weapons Software (TAWS) is a strike warfare tactical decision aid. TAWS was originally developed by the U.S. Air Force, but has been significantly upgraded and adapted to meet Army, Navy, and Coast Guard applications. Because of the new modules and enhancements, TAWS needs to be validated for accuracy. This presentation discusses the remote sensing methods used to validate TAWS operation over the marine environment. Zero-range target-background radiance contrasts as viewed along a slant path through the atmosphere are inferred using two different methods. The techniques involve making measurements at varying distances from a target with a calibrated imaging system. The data are extracted from the calibrated images and plotted with an exponential least squares curve fit. Zero-range target-background contrast, transmittance, and detection range can be derived from the resulting equation. A second method for determining the zero-range target-background contrast involves analysis of a single image and then correcting the data for the atmospheric influence using the MODTRAN code. The results, advantages and possible limitations of these techniques are discussed. Also, discussed is the possibility for future improvements to TAWS by replacing some burdensome model calculations with direct inputs from remote sensing and pre-calculated online atmospheric products.
WIN-EOTDA is a Navy strike warfare mission-planning tool based on the original Electrooptical Tactical Decision Aid (EOTDA) developed by the US Air Force in the 1980s. The WIN- EOTDA has been adapted to US Navy applications by adding a MS-Windows graphical user interface, Navy sensors and targets, and an improved ocean background model, atmospheric transmission model and sky radiance mode. Future requirements for the WIN-EOTDA include the addition of scene rendering capability, modeling in the midwave IR band, and scenarios involving near surface sensor heights. This report uses data collected during the Electrooptical Propagation Assessment in Coastal Environments (EOPACE) trials to discuss the current Navy improvements to the original ocean background model as well as improvements needed to meet the future Naval requirements. The current improvements involve replacing the original semi-empirical water background model with a combination of the MODTRAN sky radiance model and the SeaRad ocean radiance model. The SeaRad model is a rigorous geometric capillary wave model based on the Cox and Munk wave-slope statistical model. WHile the SeaRad model is suitable for moderate wind, high altitude, slant-path sensor configurations, it is inadequate for the near-surface scenarios required for the future replacement for the WIN- EOTDA. A near-surface water background model must include wave swell and effects of whitecaps. It must be coupled with an atmospheric model that includes refraction and scintillation effects. This report discusses the current improvements to the WIN-EOTDA and how algorithms used for IR Search and Track development, such as in IRTool, could be adapted to meet future requirements. The eventual replacement for WIN-EOTDA is a software program under development by the US Air Force called Target Acquisition Weather Software. The results of this case study indicate the combined SeaRad and MODTRAN modifications improve ocean background prediction performance for the high-altitude strike warfare view angles. This addition of a clutter model, such as in IRTool, may make the ocean background model suitable for surface warfare and near-horizon scenarios. However, this hypothesis warrants further investigation.
The Electro-Optical Tactical Decision Aid (EOTDA) is a strike warfare mission planning tool originally
developed by the US Air Force. The US Navy has added navy sensors and targets to the EOTDA and installed it
into current fleet mission planning and support systems. Fleet experience with the EOTDA and previous studies
have noted the need for improvement, especially for scenarios involving ocean backgrounds. In order to test and
improve the water background model in the EOTDA, a modified version has been created that replaces the existing
semi-empirical model with the SeaRad model that was developed by Naval Command, Control and Ocean
Surveillance Systems (NRaD). The SeaRad model is a more rigorous solution based on the Cox-Munk wave-slope
probabilities. During the April 1996 Electrooptical Propagation Assessment in Coastal Environments (EOPACE)
trials, data was collected to evaluate the effects of the SeaRad version of the EOTDA. Data was collected using a
calibrated airborne infrared imaging system and operational FUR systems against ship targets. A modified version
of MODTRAN also containing the SeaRad model is used to correct the data for the influences of the atmosphere.
This report uses these data along with the modified EOTDA to evaluate the effects of the SeaRad model on ocean
background predictions under clear and clouded skies. Upon using the more accurate water reflection model, the
significance of the sky and cloud radiance contributions become more apparent leading to recommendations for
The 1993 marine aerosol properties and thermal imager performance (MAPTIP) exercise conducted in the North Sea off the Dutch coast provided data for evaluating the electro- optical tactical decision aid Mark III (EOTDA) in a littoral environment. The EOTDA is a strike-warfare planning tool that is installed in the Navy's tactical environmental support system [TESS(3)] and tactical aircraft mission planning system (TAMPS 6). The objective of this report is to compare predicted detection ranges from the EOTDA with actual reported detection ranges collected during the MAPTIP trials. During MAPTIP, TNO Physics and Electronics Laboratory the Netherlands employed a Safire infrared FLIR system aboard a P-3 Orion aircraft and used the ship, the Hr. Ms. Tydeman, as a target. Ten sorties were flown and meteorological conditions were continuously recorded aboard the Hr. Ms. Tydeman. Additional weather observations were made at an oceanographic platform and at NAS Valkenburg. The weather information was compiled and converted to terminal aerodrome forecast (TAF) code for input to the EOTDA. The Safire FLIR was installed as a user-defined sensor into the EOTDA using the minimum resolvable temperature (MRT) curves of the manufacturer. The EOTDA was then run using the standard frigate model included in the EOTDA target menu. When the results are compared with the reported detection ranges, the data was scattered and showed a tendency to over-predict detection ranges. The average error was 51% on first pass. After correcting the FLIR operator observations using the video recordings, the error was reduced to 41%. Clearly, improvements are needed in the EOTDA, such as, a more accurate target model, a ship course tracking capability, and improvements to the background and transmission models.
Airborne measurements of mid and far infrared (IR) sea radiances were obtained using a calibrated dual-wavelength band thermal imaging system (AGEMA 900). The measurements were used to evaluate a sea radiance model which is based on the Cox-Munk wave slope statistics and is incorporated into a modified version of LOWTRAN 6. The measured and modeled IR blackbody sea temperatures for three days (which included low, moderate and high wind speeds) are compared as a function of the observation altitude. For all three data sets, the far IR modeled sea temperatures are less than the measured values by 1 degree(s)C to 3 degree(s)C at all altitudes. There is slightly better agreement (1 degree(s)C to 2 degree(s)C) between the measured and modeled temperatures for the mid IR band. In these instances, however, the modeled temperatures are greater than the measured values, except at altitudes where the sea backgrounds were contaminated by sun glint. Observations are presented which show that the far IR sea radiances are more closely influenced by the actual sea temperature than are those for the mid IR band, and that the strong `close-in' absorptions of carbon dioxide and water vapor control the mid IR radiances.