B n; T s
½
Š ¼
an
3
exp
bn
T s
À1
;
(7.3)
where a ¼ 1.1909 Á 10
À5 , b ¼ 1.438786, dimensions of the wave number and
temperature are: [n] ¼ cм
À1
, and [T] ¼
0 K.
Actually, by taking into account for the expression
J
"
n ¼ e n
an
3
exp
bn
Ts
À1
;
(7.4)
The expression for obtaining surface temperature is obtained after elementary
transformations
T s ¼
bn
ln e n
an 3
J
"
n
þ1
h
i:
(7.5)
The Eq. 7.4 together with direct measurements of the surface temperature T s
might be evidently used for retrieving the surface emissivity e n :
e n ¼ J
"
n
exp
bn
T s
À1
an 3
:
(7.6)
However, the above relations do not take into account for special features of the
radiometer calibration, they can’t be directly used. The instrument calibration has
been fulfilled for the water surface (with the emissivity e n ¼ 0.993) only, the
calibration curve memorized by computer is not suitable for another surface, and
the temperature recorded by radiometer does not correspond to real one. Thus,
radiometer’s reading is necessary to correct, if the other surfaces are under consideration for temperature and emissivity retrieval.
Let the methodology for recounting the radiometer reading consider when
accomplishing observation.
7.2 Determination of the Surface Emissivity
Input data for determining the emissivity e n are:
– The surface temperature T s measured with contact method;
– Radiometer recordings T r .
IR-radiometer records the self heat radiation intensity above water surface
J
"
n ¼ e
ðwÞ
n B n; T r
½
Š;
(7.7)
64
7 Remote Measurement of the Surface Temperature Field