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Effects of Atmospheric Refraction on U.S. Ground Warfare

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Effects of Atmospheric Refraction on U.S. Ground Warfare Calhoun: The NPS Institutional Archive Theses and Dissertations Thesis Collection 1983 Effects of atmospheric refraction on U.S. ground warfare Mouras, Theodore Paul. Monterey, California. Naval Postgraduate School http://hdl.handle.net/10945/19769 liiix *(';• iWi'i iiii' i is Kif/g/v( :;,,:' i'*ti;;' mi lit; NPS Dudley Knox Library. Monterey. CA 93943 NAVAL POSTGRADUATE SCHOOL Monterey, California THESIS EFFECTS OF ATMOSPHERIC REFRACTION ON U.S. GROUND WARFARE by Theodore Paul Mouras and Charles Thomas Houser September 1983 Th esis Advisor: G. E. Schacher Approved for public release, distribution unlimited T210U5 Dudley Knox Library. NPS SeCURITY CLASSiriCATION OF THIS PACE (Wt,mt Dmtm Enfrmd) Monterey. CA 95943 READ INSTRUCTIONS REPORT DOCUMENTATiON PAGE BEFORE COMPLETING FORM 1. MCPOHT NUMBCn 2. GOVT ACCESSION NO. 3. RECIPIENT'S CATALOG NUMBER 4. TITLE fand SuhlItU) 5. TYPE OF REPORT & PERIOD COVERED Effects of Atmospheric Refraction on Master's Thesis; U.S. Ground Warfare September 19 8 3 «. PERFORMING ORG. REPORT NUMBER 7. AUTHOn<«; B. CONTRACT OR GRANT NUM8ERC«J Theodore Paul Mouras and Charles Thomas Houser • PEnPORMINOOROANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT, PROJECT, TASK Naval Postgraduate School AREA & WORK UNIT NUMBERS Monterey, California 9 39 43 It. CONTMOUUINO OFFICE NAME AND AOOMESS 12. REPORT DATE Naval Postgraduate School September 1983 Monterey, California 93943 13- NUMBER OF PAGES 316 U. MONITORING ACENCY NAME 4 AOORESSfi/ dl//*ran( /rem Conlrolllna OWcm) 15. SECURITY CLASS, (al thia raport) UNCLASSIFIED tS«. DECLASSIFICATION/ DOWNGRADING SCHEDULE U. mSTRiauTlON STATEMENT (ol thia Rmpatt) Approved for public release, distribution unlimited 17. mSTRiauTION STATEMENT fo/ (A« •batwmet mtmnd In Block 30, It dillmranf Item Raport) It. SUPPLEMENTARY NOTES It. KEY WORDS CConfinu* on tovotmo oldo II nocoaoarr «Rd Idontlly by block numbmr) Atmospheric Refraction; Anomalous Propagation; Mirage; Optical Turbulence; Atmospheric Turbulence; Electromagnetic Propagation; Refractive Prediction; Ducting 20. ABSTRACT (Canttmto «n i«v«r«* aid* II tiocmmmary and Idontlly by block numbmr) This thesis investigates the effects of atmospheric refraction on military ground-force tactical systems which utilize EM energy propagating through the troposphere. Anomalous propaga- tion, mirages, and atmospheric turbulence are the three major atmospheric refractive conditions discussed. EM energy, from visible light to VHF radio is considered. The refractive characteristics of the atmosphere and the conditions that lead to significant refractive effects are FORM COITION OF I tt IS 00.; AN 7S 1473 NOV OBSOLETE S/N 0102' LF. 014- 6601 1 SECURITY CLASSIFICATION OF THIS PAGE (Whon Data Sntaraa . SCCumTY CLASSiriCATIOM OF THIS PAGE fWh««» Dmlm Bnfr*d) reviewed. The means of predicting atmospheric refraction and the usefulness of such predictions, along with the probability of occurrence of atmospheric refraction is also discussed. Specific examples of atmospheric refractive effects are provided in two forms: computer simulations and qualitative studies. A scenario is simulated showing the wide range of atmospheric refractive effects a typical ground force might anticipate in a desert environment. Finally, the thesis provides conclusions and recommendations for further studies S'N 0102- LF-014-6601 SECURITY CLASSIFICATION OF THIS PAGtrWi*" Daim Bnfrmd) Approved for public release, distribution unlimited Effects of Atmospheric Refraction on U.S. Ground Warfare by Theodore Paul Mouras Captain, United States Army B.S., Virginia Military Institute, 1976 and Charles Thomas Houser Lieutenant Colonel, United States Army B.S., University of Tampa, 1975 Submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN SYSTEMS TECHNOLOGY (ELECTRONIC WARFARE) from the NAVAL POSTGRADUATE SCHOOL September 1983 . ABSTRACT This thesis investigates the effects of atmospheric refraction on military ground-force tactical systems which utilize EM energy propagating through the troposphere. Anomalous propagation, mirages, and atmospheric turbulence are the three major atmospheric refractive conditions discussed. EM energy from visible light to VHF radio is considered. The refractive characteristics of the atmosphere and the conditions that lead to significant refractive effects are reviewed. The means of predicting atmospheric refraction and the usefulness of such predictions, along with the probability of occurrence of atmospheric refraction is also discussed. Specific examples of atmospheric refractive effects are provided in two forms: computer simulations and qualitative studies. A scenario is simulated showing the wide range of atmospheric refractive effects a typical ground force might anticipate in a desert environment. Finally, the thesis provides conclusions and recommendations for further studies \ i TABLE OF CONTENTS I. INTRODUCTION 9 II. ATMOSPHERIC REFRACTIVE EFFECTS n A. EM WAVE PROPAGATION IN THE ATMOSPHERE -^^ 1. Wavelength Dependence of EM Propagation Effects ]_]_ 2. Index of Refraction (n) -.3 3. Snail's Law 14 B. REFRACTIVITY 20 1. Refractivity (N) 20 2. Anomalous Propagation, Mirage, S Optical Turbulence 2 5 C. ANOMALOUS PROPAGATION 27 1. Superrefraction , Subrefraction , and Ducting Defined 28 2. Means of Describing Refraction 31 3. Duct Characteristics 32 4- . Causes of Superrefraction, Ducting, and Subrefraction M-O 5. Consequences of Anomalous Propagation 47 6. Methods of Predicting Refractive Effects- 66 D. MIRAGE 69 1. General Description of the Mirage Phenomena 6 9 2. Effects of Mirages on Optical Devices 77 E. TURBULENCE 79 1. General Description of Turbulence 7 9 2. Principal Effects of Turbulence on Optical Propagation 90 5 ( i c a. Scintillation g-]_ b. Wave Front Tilt and Beam Spread 93 c. Resolution 95 3. Manifestation of Turbulence in Optical Systems 100 4. Turbulence and MMW Propagation in the Atmosphere 10 6 F. PREDICTION AND PROBABILITY OF OCCURRENCE OF ANOMALOUS PROPAGATION, MIRAGE FORMATIONS, AND TURBULENCE 107 1. Anomalous Propagation 109 2. Mirages and Turbulence 12 5 3. Comparison of Mid-East and Central Europe 12 8 M-. Conclusions 134- III. ATMOSPHERIC REFRACTION AND GROUND WARFARE 136 A. INTRODUCTION 136 B. EFFECTS OF ATMOSPHERIC REFRACTION ON TANK OPTICAL FIRE CONTROL SYSTEMS 137 1. Atmospheric Conditions Creating the Gunnery Errors 140 2. Expected Effects on Tank Gunnery 141 3. Experimental Results 142 4. Conclusions 149 C. COMPUTER SIMULATION 1 - THE EFFECT OF REFRACTIVE CONDITIONS ON U. S. TACTICAL SYSTEMS, USING THE TROPOPLOT COMPUTER PROGRAM 15 4 1. Tropoplot Program Description 155 2. AN/FPS-16 Radar 156 3. AN/VRC-12 Radio 160 6 ( <l c M- . Conclusions 2.61 D. COMPUTER SIMULATION 2 - THE EFFECT OF HORIZONTAL REFRACTIVE GRADIENTS ON AIRBORNE DIRECTION FINDING ACCURACY 161 1. General Description of Direction Finding and the Tactical Scenario 163 2. Algorithm Description 168 3. Results and Conclusions 173 E. SCENARIO 187 1. Scenario Background 187 2. Atmospheric Refractive Effects 190 a. Optical Effects 190 b. Effects on Communications and Electronic Warfare Systems 191 c. Effects on Noncommunications Emitters 19 3 3. Conclusions 19M- IV. CONCLUSIONS AMD RECOMMENDATIONS 196 A. CONCLUSIONS 196 B. RECOMMENDATIONS 198 APPENDIX A - IREPS 200 APPENDIX B - COMPUTER SIMULATION 1 LISTING AND OUTPUT— 212 APPENDIX C - COMPUTER SIMULATION 2 LISTING AND OUTPUT-- 271 LIST OF REFERENCES 311 BIBLIOGRAPHY 314 INITIAL DISTRIBUTION LIST — - 316 ACKNOWLEDGEMENT We would both like to express our gratitude and sincere appreciation for the guidance and patience extended to us by our thesis advisor, Professor Gordon Schacher. Without Professor Schacher 's assistance, the problems involved in this thesis would have been insurmountable. We would also like to extend our appreciation to Dr. Don Snider, of ASL, for his assistance as our second reader, and for the technical input he provided. Likewise, we would like to thank Professor Ken Davidson for his contributions to this thesis. Several other individuals also provided technical input; thus, thanks is extended to Distinguished Professor E. C. Crittenden, Professor R. L. Kelly, Professor Jeff Knorr, Professor B. A. Milne, Professor Will Shaw, and LCDR Jim Corbin of the Geophysical Technical Readiness Center. Finally, a special thanks to Melanie Mouras, for ruthlessly editing many of the sections in this thesis. Despite all the red ink involved, both of us are appreciative of her assistance. i . I. INT-RODUCTION In order to enhance and extend surveillance and communications capabilities, modern ground warfare has become increasingly dependent on the entire electromagnetic (EM) spectrum. Uses of electromagnetic energy include airborne and ground target detection, weapons system tracking and guidance, command and control, and electronic warfare. Utilization of this energy requires an under- standing of the phenomena that affect the propagation of EM waves as they travel through the atmosphere. After nearly 5 years of study, it is now widely accepted that dispersion, extinction, refraction, reflection, and diffraction all affect EM propagation significantly. Dispersion, extinction, and refraction are properties of the atmosphere, while reflection and diffraction are properties both of the atmosphere and of the terrain of the earth's surface. For radio/radar frequency (RF) and electro-optical (EO) systems, the physical factors listed impact on system performance above and beyond the more obvious effects of precipitation, wind, and temperature extremes (
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