HYGROSCOPIC EFFECTS ON REENTRY VEHICLE ANTENNA WINDOWS

ADVANCED-HIGH ACCURACY AIR FORCE REENTRY SYSTEMS CAN INVOLVE THE USE OF ELECTRICALLY STEERABLE ANTENNAS TO CONDUCT GUIDANCE, SURVEILLANCE AND ACQUISITION FUNCTIONS. TO ACHIEVE THE ACCURARY NECESSARY FOR THESE SYSTEM, LABORATORY TUNING AT SIMULATED OPERATIONAL CONDITIONS IS REQUIRED TO PREVENT ERRORS INDUCED BY FABRICATION TOLERANCES. ESSENTIALLY ALL WINDOW MATERIAL CANDIDATES FOR AIR FORCE SYSTEMS ARE HYGROSCOPIC TO VARYING DEGREES. VARIABILITY IN WATER CONTENT CAN CHANGE THE MATERIALS' DIELECTRIC PROPERTIES AND THUS DEGRADE LABORATORY TUNING AND ANTENNA PERFORMANCE. THE PROPOSED EFFORT IS TO ASSESS THE NEED TO CONTROL ANTENNA WINDOW HYGROSCOPIC BEHVIOR, AND IDENTIFY CANDIDATE METHODS TO REDUCE HYGROSCOPIC SENSITIVITY.