In discussion it was brought out that study is being undertaken by W. L. Godson to 

 determine a practical means of correcting the IRT records to reveal the true temperature 

 to about ±0.1°C. Other work is going on to determine the difference between microsurface 

 and bucket-depth temperature. It is believed that if the IRT instrument can operate with an 

 error limit of ±0.5°F. or less, the aerial survey temperature data will be widely useful. 

 Dr. TuUy believes that because "normal ambient" variation is near 1.0°C., precision to 

 0.1°C. may not be required in environmental studies.-'- 



John Clark and Richard B. Stone: Use of the Infrared Thermometer in Routine 



Coastal Survey 



The Sandy Hook Marine Laboratory has carried out monthly aerial surveys of sea 

 surface temperature over the Atlantic Continental Shelf routinely since December 1962. 

 The basic requirement was to estimate surface temperatures with a maximum of error of 

 ±1.0°C. The greatest problem with this has been that there is no longer a single definable 

 "surface" temperature because of the vertical thermal gradient between microsurface and 

 "bucket depth." To adjust for many sources of error, such as input-voltage variation, 

 bias-battery deterioration (with IT-1), etc., the temperature record was corrected in flight 

 to agree with regular calibration readings against a container of water of known temperature 

 measured by immersion thermometer. The error in temperature readout associated with 

 frequency change was found to be about 1.5°C. for a shift from 59.9 to 61.1 cycles. Repeat- 

 ability tests were made in cooperation with the Naval Oceanographic Office in which the 

 Na-vy and Sandy Hook IRT's, in separate aircraft, were flown over the same track. 



Post workshop note. — Dr. Tully advised on September 14, 1964: 



(1) Four units of the airborne radiation thermometer (FRB-2) have been completed and are in service 

 with RCAF- Maritime Air Command, as planned. 



(2) The equipment is not as quiet (electrically) as we would like to have had it. The ambient variation of 

 the temperature record, due to internal electrical variation, is about 0.3°C. Final elimination of this 

 "noise" could require many months of research. This level of uncertainty is tolerable in the present 

 state of the art of infrared thermometry, so we have decided to accept it for the present. However, 

 we plan to devote as much time to corrective measures as our work load here will allow. 



(3) Also, we have abandoned the construction of an inflight calibration device, partly because primary 

 calibration using a tub of water is quite satisfactory, and partly because the ec(uipment is temperature 

 stable and does not require in-flight calibration. 



(4) Two units are in service here on the west coast. Two units of the ART have been dispatched to the east 

 coast for equipment proving and evaluation and to support the Information Service there. 



(5) The fifth unit will be used here at Nanaimo to verify the relation between the radiated sea surface 

 temperature and the subsurface temperature and structure. This could not be done until now because 

 adequate equipment was not available. An oceanographic tower has been built in Departure Bay. From 

 it, thermistors will be suspended in the water to record the temperature, structure and variations 

 (heating, cooling, transients, etc.). At the same time the surface condition will be recorded by the ART, 

 at constant height. Finally the records will be correlated and analyzed. This series of tests may con- 

 tinue through next summer (1965). 



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