The HIRDLS instrument is a limb viewing infra-red radiometer on the NASA Aura spacecraft in a sun synchronous low
earth orbit and obtains measurements of the composition of the atmosphere covering the whole Earth each day. The
MIPAS instrument is a limb viewing infra-red interferometer on board the European Envisat satellite in a very similar
orbit to Aura except that the local solar time is different. The complement of geophysical data products of both
instruments is very similar, and because of similar observation strategies their two data sets can be usefully compared.
The comparison provides the means to support validation in order to obtain statistics such as systematic differences and
variance. This is performed over the full latitude range of HIRDLS and height range of MIPAS and thereby helps to
identify sources of errors. The identification of known atmospheric features is a useful diagnostic, and includes such
things as regions of upwelling of tracer gases, or the propagation of coherent structures as with mid-latitude waves and
we can test whether these structures are consistently represented in both data sets. HIRDLS version 2.04.19 (v004)
temperature, ozone and nitric acid show very low systematic 'errors' compared to MIPAS over most of the spatial range.
Currently pre-released water vapour, nitrous oxide and F-11 are reasonably similar, CH4 somewhat more restricted, and
nitrogen dioxide, N2O5, chlorine nitrate and F-12 as yet susceptible to complications from the obstructed telescope.
Further details are discussed in the paper.