Accession Number : ADA118425
Title : A Comparison of the AFGL Flash, Draper Dart and AWS Haze Models with the Rand Wetta Model for Calculating Atmospheric Contrast Reduction.
Descriptive Note : Technical note,
Corporate Author : AIR FORCE ENVIRONMENTAL TECHNICAL APPLICATIONS CENTER SCOTT AFB IL
Personal Author(s) : Breitling,Patrick J
Report Date : Mar 1982
Pagination or Media Count : 55
Abstract : In 1975 the US Air Force Environmental Technical Applications Center (USAFETAC) was tasked to develop a model to calculate the lock-on range for TV-guided precision guided munitions. Investigation revealed the availability of several models for calculating contrast reduction by the atmosphere. These models, the Air Fore Geophysics Lab (AFGL) Flash model, the Air Weather Service (AWS) Haze Model, the Draper Lab Dart model, and the Rand Corp. WETTA model, were compared with one another using the same input data. The FLASH Monte Carlo model was assumed as the standard for the comparison. Visible Contrast transmission values were computed for all models for a TV sensor at 12,000 feet AGL, for two mixing depths (200 and 1500 meters), two visibilities (5 and 23 kilometers), three solar zenith (20, 60, and 85 degrees), three albedos (.06,.18, and .80), and seven dive angles (85,70,50,30,20,10 and 7 degrees). If one accounts for the difference in optical depths which results from Huschke's (Rand Corp.) stair step treatment of vertical extinction coefficients, his model does an acceptable job of approximating FLASH contrast transmission values for a visibility of 23 kilometers. When the visibility is 5 kilometers, the agreement is not as good due to a combination of mathematical and geometrical factors.
Descriptors : *ATMOSPHERE MODELS , *RADIATIVE TRANSFER , TELEVISION GUIDANCE , HAZE , ADVERSE CONDITIONS
Subject Categories : Meteorology
Distribution Statement : APPROVED FOR PUBLIC RELEASE