Spectral Measurements of Solar Irradiance and Radiance in Clear and Cloudy Atmospheres - Short-Wave Solar Radiation in the Earth's Atmosphere - page 79

Fig. 3.1. Deviation of real instrumental function f Ω

ϑ ϕ

) of the opaque-skinned integrator
of light conductor from the theoretical cosine dependence

( ,

granted to the instrumental function of the K-3 instrument was not enough
at those times. Regretfully, this lack of information makes the application of
modern complex approaches difficult for interpretation of the observational
results considered here.
The first concern of the accomplished airborne observations was to study
the spectral reflectance properties of natural surfaces. For this purpose the
upwelling radiance and downwelling irradiances were measured. Another
concern was the elucidation of the radiative regime of the atmosphere from
measurements of the upwelling and downwelling solar irradiances in different
atmospheric layers. All mentioned observations were accomplished on board
the IL-14 aircraft.
AK-3 spectrometer fixedona special rotationdevicewas set to the hatch, and
allowed registration of nadir angles in the range 0−45 ◦ (the angle is counted
off the vertical to the airplane flight direction). The varying of the viewing
angle azimuth was reached with the change of flight direction, the azimuth
scale was set as follows: 0 ◦ was the direction to the Sun, 180 ◦ was the direction
opposite to the Sun. The instrument angle of view was 2 ◦ during the radiance
registration.
For airborne observations of the upwelling and downwelling irradiances,
a special light conductor was used. There was a metallic tube passing through
the aircraft fuselage and provided with the device allowing the directing of the