A first beam of light from a laser is split by a beam splitter into a
reference beam and at least one second beam of light, the latter of which
is directed from an optical head into an atmosphere. Light from the at
least one second beam of light scattered by molecules or aerosols in the
atmosphere is collected by a corresponding at least one telescope of the
optical head as at least one light signal. The at least one light signal
and the reference beam are simultaneously processed by different portions
of a Fabry-Perot interferometer, and resulting fringe patterns are imaged
onto a detector and processed by a data processor to determine at least
one associated air data product.