Figure 1-8.Data coverage on successive orbits of a polar-orbiting satellite.
polar-orbiting satellites circle the earth at a much lower
altitude (about 850 km), they have the advantage of
photographing clouds directly beneath them at
relatively high resolution.
Although nearly every
environmental satellite provides both infrared and
visual imagery, polar-orbiting satellites are better
suited to gathering imagery from the high-latitude and
polar regions. They also provide imagery as they cross
the equatorial regions. This makes them extremely
well suited for oceanographic applications where slow
changes in water temperature are adequately tracked
by only two or four images a day.
The width of the usable image from a polar-
orbiting satellite is a function of the satellites altitude.
The average swath width is about 2700 km (1500 nmi).
Polar-orbiting environmental satellite orbits are
planned so that the usable image area overlaps slightly.
Figure 1-7 shows a typical TIROS-N satellite, while
figure 1-8 shows the area covered by usable imagery
on successive orbits of a polar-orbiting satellite.
As of this writing, NOAA 12 (TIROS-ND) and
NOAA 14 (TIROS-NJ) are the two fully operational
polar-orbiting satellites in the TIROS-N series. A new
series of polar-orbiting satellites will be launched by
the spring of 1998, and will be referred to as NOAA-
POES (NOAA-Polar-orbiting Operational
Environmental Satellite). Table 1-1 compares various
characteristics between geostationary and polar-
Table 1-1.Geostationary Versus Polar-orbiting Characteristics