There are two main reasons to operate this instrument from an aircraft.
One reason is that the water vapor signal at lower altitudes becomes too strong
because of the large amount of water vapor in the troposphere. This blocks the
much weaker stratospheric signal at low altitudes. The second reason is that by
flying the instrument around, we get a good look at the distribution of these
important trace gases over a large geographical range.
Fig. Set of H2O spectra measured at different altitudes during an ascent in the tropics