temperature dependency; wire wound resistors are 

 selected wherever dividers or calibration adjust- 

 ments and networks are used; very highly regu- 

 lated power supplies are employed using either 

 closed loop regulation or precise zener diode 

 regulation; highest quality components are util- 

 ized and all leads that might he a source of 

 extraneous or varying pickup are shielded. 



Presentation 



Data output is provided in two forms . An 

 approximate value of the sea surface temperature 

 is indicated continuously on the sea surface 

 temperature panel meter. Temperature precise to 

 i0.2°C is presented as an instantaneous indica- 

 tion in the form of a continuously printed 

 recorder output on the strip chart. 



Both the panel meter and strip chart recorder 

 present the data in four 10°C ranges; -2°C to 

 +8°C, +7°C to +17°C, +l6°C to +26°C and +25°C 

 to +35°C These ranges overlap one degree, with 

 the upper end of each range overlapping the lower 

 end of the next higher range. 



Operating Characteristics 



The following operating characteristics have 

 been determined from laboratory tests. Calibra- 

 tion runs show an accuracy of absolute tempera- 

 ture measurement of better than it).2 C. System 

 electronic noise is equivalent to 0.05 C and it 

 can be reduced further . Reference temperature 

 (cavity) control drift is within to.05°C. 



INFRARED RADIATION THERMOMETER 



The infrared radiation thermometer (IRT) was 

 developed to provide a small, compact and por- 

 table radiometer where the size and precision 

 performance requirements of the ART were not 

 needed. Basically, the two instruments are 

 identical in principles of operation. 



The IRT differs from the ART in the following 

 respects: 



1. Smaller entrance aperture. 



2. On-off cavity controller rather than pro- 

 portional controller. 



A photograph of the IRT is shown in Fig. 7- 

 As in the ART it consists of three units — 

 radiometer, electronic unit and optionally sup- 

 plied recorder. Operation consists of setting 

 up the radiometer to view in the desired direc- 

 tion, turning on main power and reading panel 

 meter (and/or recorder) after the reference 

 cavity is up to operating temperature. 



The IRT can be supplied with a filter similar 

 to the ART (to pass only energy in the 8-13 

 region) . The unit shown in Fig. 7 was calibrated 

 on a black body and adjusted for a full scale 

 panel meter readout of 15°F to 100°F. 



FIELD TEST OF AIRBORNE RADIATION THERMOMETER 



Field tests have been carried out by the 

 Navy Oceanographic Office for which the instru- 

 ment was developed. Test data have been obtained 

 from 3 "types of platforms under the conditions 

 described below. 



Static Tower Tests 



In June 1962 the ART was mounted on ARGUS 

 ISLAND, an oceanographic tower in 19^ feet of 

 water 22 miles southwest of Bermuda. The tower 

 platform was easily adapted for mounting the ART. 

 The instrument had an unobstructed view of the 

 sea surface from a height of 65 feet and was 

 operated continuously during daylight hours . 

 Bucket temperatures were taken periodically. 

 Comparison of ART temperatures and bucket tempera- 

 tures are shown in Figs. 8 and 9- The trend of 

 the curves shows a greater change in ART tempera- 

 tures than in bucket temperatures with the maxi- 

 mum change occurring at 1^00 hours. On 26 and 

 27 June skies were 0.8 obscured by clouds and air 

 temperature reached a maximum value at about 1300 

 hours. The ART appears to be recording the tem- 

 perature of the surface of the water accurately. 

 This has been shown in the laboratory; however, 

 methods remain to be devised for relating these 

 values to water temperatures at depths of 5 to 

 10 feet. Future tests are being planned to 

 repeat the ARGUS ISLAND tests on a more compre- 

 hensive scale. The ART measurement will be 

 related to humidity, air temperature, wave height 

 and albedo. A thermistor chain will make con- 

 tinuous recordings of water temperature at various 

 levels in the upper foot of water. 



3 . More rudimentary reference cavity structure . 



k. AC signal panel readout instead of DC 

 synchronous detection. 



5. Calibrated to temperature range as desired. 



These basic changes have resulted in a highly 

 compact, simply operated unit having an accuracy 

 of the order of 1°C and a sensitivity of 0.1 to 

 . 2°C . 



Helicopter Flight Tests 



Prior to acceptance of the prototype ART 

 several flight tests of the instrument were made 

 over Chesapeake Bay on 23 and 2k June i960. The 

 ART was mounted in a HUP-2 helicopter. A series 

 of passes were made across the track of a small 

 boat which towed a thermistor probe clear of the 

 boat's wake. These instruments were calibrated 

 under identical conditions; equal accuracies were 

 indicated. 



66 



