





“INCOMING 
RADIATION 


THERMISTOR— 
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| HEATER 
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SENSING HEAD 
Fak ews 
aide ater 
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[i] CONTROLLER 
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POWER 
SUPPLY 
ELECTRONICS CONSOLE 


Figure 7.--Block diagram of Barnes Engineering Infrared Bolometer ® , Instrument reads out directly in 
degrees Fabrenheit temperature, 

Figure 8,--Barnes Engineering Bolometer ® sensing 
head pointed at noctuid moth mounted onsmalltherm= 
istor hypodermic probe, Oscilloscope recordings are 
made on dual=beam oscilloscope both of internal 
temperature and FIR emission of moth, 
temperatures were recorded from the therm- 
istor probe on the lower beam and their IR 
emission from the bolometer on the upper 
beam. 
The thoracic temperatures for the various 
species and the A m (FIR emissions) of the 
moths are given in table 3. The highest emis- 
sion was recorded from the sphingid Epistor 
164 
lugubris L, This is alarge, thick-bodied, very 
dark species. The lowest recording was from 
the much smaller noctuid armyworm moth 
(Pseudaletia unipuncta (Haworth)). Since the 
noctuid species filled only half or less of the 
resolving power (area) of the bolometer sens- 
ing head, this result was to be expected. 
The emission of the moth Herse cingulata 
(F.) above the emission of the background tem- 
perature is shown in figure 9, top. Figure 9, 
bottom, shows that asthe bolometer was moved 
in a circular pattern around a moth, the maxi- 
mum output was obtained from the side of the 
thorax off the "shoulder" of the moth. Inasmuch 
as the bolometer has maximum pickup for a 
source with an emissivity (€) of 1.0, the high 
signals received indicated that moths have an 
emissivity near unity (1.0). Calculated peak 
frequency (fig. 9, top) for the sphingid moth 
H, cingulata was 9.25 w at 399C,, or 15° above 
the laboratory temperature of 24° (9.75 yn). 
The laboratory temperature, as measured by 
an air probe, is shown as the solid line (24°) 
on the oscilloscope. The calculated energy for 
H, cingulata at 39° (oscilloscope recording), 
considering the moth thorax asa 1-cm.” source 
with an e of 0.95, would be 5x 10~ watts/ 
cm.”. Ata distance of 1 km., this value would 
translate to an incident energy signal of 1.6 
X 10°” watts /cm.*, energy easily detectable 
by a receiver. This frequency is in the middle 
