Page 154 - Intro to Space Sciences Spacecraft Applications

Remote Sensing
satellite direction of flight and held at a fixed look angle of 30 degrees. 141
This orientation is identical to the example shown in the previous fig-
ure. The aperture dimensions are 5 m (Dazimufh) 1 m (Dcmss.uack) and
x
the radiometer center frequency is 2 GHz. If the radiometer is held at
a fixed look angle of 30", determine the slant range to the ground,
IFOV, and GIFOV for the along-track and cross-track dimensions.

Solution:

Using equation 6-2 (knowing the look angle, h and RJ we can
solve for all the other unknowns:

(w + 90) = 35.3" or 144.7" (must be > 90')

3i = 5-34"

R = 1186.8 km

From the center frequency of observation:

IFOV,,s.,k = 178.1 km

GIFOV,,,,~,,,k = 218.2 km

Observation of Electromagnetic Radiations

The electromagnetic spectrum was described in Chapter 4 along with the
relative frequencies and energies radiated by the sun and the earth due to their
respective surface temperatures. In the case of passive sensors, these natural
radiations, and their interaction with the earth and atmosphere, are what is
sensed. Active sensors operate in exactly the same manner except that they
provide a known spectral illumination of the target area and then sense the
reaction of the target and atmosphere to the transmitted frequencies.

Target Spectral Interaction Mechanisms. A number of interactions are
possible when electromagnetic energy encounters a target or scene. The