There are, however, also disadvantages to the limb nadir matching technique.

1. It can currently only be applied to SCIAMACHY measurements, because this is the only instrument taking both limb and nadir observations.
2. Limb retrieval is quite time consuming, at least compared with the DOAS analysis of nadir data.
3. Limb measurements also introduce uncertainties. In particular, because the sensitivity in the lower stratosphere is reduced, and because of the differences in nadir and limb measurements, errors can no longer be expected to cancel as often as they do in the reference sector method.