MIPAS-B2 is a balloon-borne limb-emission sounder for atmospheric research. The heart of the instrument is a Fourier spectrometer that covers the mid-infrared spectral range (4-14 microns) and operates at cryogenic temperatures. Essential for this application is the sophisticated line-of-sight stabilization system, which is based on an inertial navigation system and is supplemented with an additional star reference system. The major scientific benefit of the instrument is the simultaneous detection of complete trace gas families in the stratosphere without restrictions concerning the time of day and viewing directions. The specifications, the design considerations, the actual realization of the instrument, and the results of characterization measurements that have been performed are described.

Polar stratospheric clouds (PSCs) were observed by the high resolution mid infrared Michelson Interferometer for Passive Atmospheric Sounding, Balloon borne version (MIPAS‐B), on a flight from Kiruna/Sweden on January 11, 2001. Highly resolved spectral features in the limb measurements could only be explained by tropospheric radiation scattered into the line of sight by large PSC particles. Furthermore, model calculations showed that for PSCs with particles of radius ≥1 μm, a significant part of the broadband continuum radiance signal is due to scattering. Inclusion of scattering in the retrieval process resulted in reasonable values of otherwise largely overestimated PSC volume density profiles.

Abstract. The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an imaging limb emission sounder operating in the thermal infrared region. It is designed to provide measurements of the upper troposphere/lower stratosphere with high spatial and high spectral resolution. The instrument consists of an imaging Fourier transform spectrometer integrated into a gimbal. The assembly can be mounted in the belly pod of the German High Altitude and Long Range research aircraft (HALO) and in instrument bays of the Russian M55 Geophysica. Measurements are made in two distinct modes: the chemistry mode emphasises chemical analysis with high spectral resolution, and the dynamics mode focuses on dynamical processes of the atmosphere with very high spatial resolution. In addition, the instrument allows tomographic analyses of air volumes. The first measurement campaigns have shown compliance with key performance and operational requirements.

Vertical profiles of the most important species of nocturnal total reactive nitrogen (NOy = NO2 + HNO3 + ClONO2 + 2 N2O5 + HO2NO2) together with its source gas N2O were retrieved from infrared limb emission spectra measured by the Michelson Interferometer for Passive Atmospheric Sounding, Balloon‐borne version (MIPAS‐B) instrument inside the late winter arctic vortex from Kiruna (Sweden, 68°N) on 24 March 1997 and in summer midlatitudes from Gap (France, 44°N) on 2 July 1997. The measured data were compared to calculations performed with the three‐dimensional chemistry transport model (CTM) Karlsruhe Simulation model of the Middle Atmosphere (KASIMA). The results show that in the late winter arctic vortex most of the available nitrogen and chlorine is in the form of HNO3 and ClONO2, respectively. An anomalous N2O‐NOy correlation observed in March 1997 appears to be caused to a large extent by quasi‐horizontal mixing of air masses across the vortex edge. However, near 20 km some denitrification of ∼1.5 to 2 ppbv NOy could be observed. The N2O profile measured in July 1997 indicates remnants of polar vortex air and is not reproduced by the CTM at the same location. However, the profile shapes of the individual compounds of the NOy family as well as the NOx/NOy ratio are reproduced fairly well by the model.

Abstract. The ENVISAT validation programme for the atmospheric instruments MIPAS, SCIAMACHY and GOMOS is based on a number of balloon-borne, aircraft, satellite and ground-based correlative measurements. In particular the activities of validation scientists were coordinated by ESA within the ENVISAT Stratospheric Aircraft and Balloon Campaign or ESABC. As part of a series of similar papers on other species [this issue] and in parallel to the contribution of the individual validation teams, the present paper provides a synthesis of comparisons performed between MIPAS CH 4 and N 2 O profiles produced by the current ESA operational software (Instrument Processing Facility version