C. Problems of IRT operation under airborne conditions. 



1. Naval Air Development Center experience with infrared radiometers indicates 

 that the principal internal noise problem stems from aerodynamic flow past 

 the optical system. Aircraft roll, pitch, banking, climbing and descending 

 change the temperature of the optical system and cause variable signals. 



2. Collection of moisture on optics (This sometimes occurs if the aircraft de- 

 scends from high altitude to low, warmer, more humid altitudes.) 



D. When the ocean is viewed at night with a vertical-looking IRT operating at low 

 altitude and with negligible intervening atmospheric water (vapor, liquid or 

 solid), the IRT provides a weighted-average temperature measurement of the 

 upper few thousandths of an inch of the ocean provided the area viewed is free 

 of slicks. 



E. "Bucket depth temperatiires" should be calculable to within ±0.1C° from night- 

 time vertical IRT measurements provided air temperature, wind and humidity 

 are known. 



F. Reports of IRT data should be standardized to include aircraft position as a 

 function of time; cloud cover (altitude and percent coverage), air temperature, 

 wind speed and direction, humidity, wave height, and aircraft altitude as func- 

 tions of position; and synoptic weather and sea information from ships in the 

 area surveyed. 



RECOMMENDATIONS 



1. Infrared mapping devices that can produce continuous thermal strip maps of 

 the ocean should be used in conjunction with infrared radiation thermometers. 

 The interpretation of wiggling recorder pen lines is made obvious in many 

 cases if thermal pictures are available. 



2. If it is desired to correlate IRT readings with bulk water temperatures, map- 

 ping flights should be conducted at night. "Noise" levels (from sun glitter) 

 are lower at night; uncertainties due to surface reflection and due to surface 

 heating from the action of the sun are eliminated. Night-time convective 

 mixing permits the recording of IRT readings that are more indicative of 

 bulk temperatures than recordings taken during periods of stability. 



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