will provide a more stable environment for operation of the instrument. It was also noted 

 that the view path of the instrument should avoid the exhaust path of the airplane engine. 



Vibration. Vibration is not considered an important problem with the instrument 

 on shock mounts. Shock, however, can be a problem and should be avoided. 



Moisture on Optics . Problems developing from this source could be eliminated by 

 heating the optics, or more simply by protective location of instrument. 



Interference . There can be pronounced effects from radio transmission and an 

 attempt should be made to eliminate such interference. Since the effects are generally in- 

 duced through the power lines, insertion of R.F.I, (radio frequency interference) filters in 

 the power lines should reduce this to an acceptable level. 



Question 4. What limitations are imposed by variable meteorological conditions 

 and to what extent can the effect of any of these be predicted and the data corrected? 



The consensus was that effect of the sky reflectivity component could, in practice, 

 cause a variability of 0.5°C. Theoretically the variability could exceed 1.0°C. Water 

 vapor in the air path could, in practice, cause an error of 0.5°C. or even greater error 

 under unfavorable conditions. If all meteorological variables could be properly recorded, 

 corrections could be applied which could reduce the variation to 0.1 to 0.2°C. Therefore, 

 it appears of the utmost importance that sky temperature, air temperature, and humidity 

 be accurately measured. It is recognized that measurements would have to be made at 

 various altitudes to detect variations through the air column from the water surface 

 upward. 



Humidity. A correction can be made for water vapor with a relatively short air 

 column by measuring the average air temperature in the column and the amount of water 

 vapor and using the following formula developed by the Weather Bureau: 



t^ = (t - t ) (1 - 0.8^) 

 E a s 



where 



t„ = temperature error, 



t = mean temperature of the air column, 



t = surface water temperature, 



w = optical thickness (measurement of water vapor in the air column), and 



0.8 = mean value of transmission coefficients for wave lengths between 8 and 

 13 microns. 



-19- 



