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Chapter 30
sounders—the IS represents the group with the widest range of applications.
Its geometric and spectral resolution is about half way between the other two
optical instrument categories (a rather crude categorization).
There is one fundamental difference between these three main groups of
instruments: while countless data archives from space-borne sensors are
available for high-resolution imager and sounder type instruments, there are,
until now, only airborne IS data, at least of the Earth.