Page 53 - Intro to Space Sciences Spacecraft Applications

Introduction to Space Sciences and Spacecraft Applications
40

h= 35,786 krn

Figure 2-7. Field of view. Properties that a spacecraft has with respect to
the surface of the earth change dramatically with altitude.

q=cos-l ~ (2 - 14)
(R:: h)

The maximum distance visible from one tangential horizon to the other
is known as the swath width SW which can be found from:

SW = 2R& (2-15)

The area on the surface of the earth associated with the swath width is
shown shaded in Figure 2-7. This is thefootprint area of coverage theo-
retically possible from the satellite position. This area can be found from:

A = 2nR; sin@ (2-16)

Finally, the angle subtended (from the perspective of the satellite)
between the line from nadir to a line toward the tangential horizon is
known as the angular field of view (FOV) Q and is determined from:

(2 - 17)

This angle is important, as it represents the angle that a particular sensor
would have to be able to scan or view in order to cover all the potentially
visible surface of the earth.
All of these terms have similar but slightly different meanings when
used to describe the capabilities of a particular sensor in space, as dis-
cussed in Chapter 6. For instance, swath width may be used to describe