Several FTIR spectrometers, known as MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) have been developed for operation on ground, aircraft, and stratospheric balloon gondolas by the Institut für Meteorologie und Klimaforschung.
An uncooled version of this interferometer was constructed during the first half of the 1980s. This MIPAS-LM (- Lab Model) was used from 1989 till 1993 as a ground-based device for observing time series of column amounts of chemical species such as O3, N2O, CH4, HNO3, NO2, HCl, ClONO2, and HF at polar stations by detecting the attenuated solar radiation. In 1993, MIPAS-LM was replaced by a Bruker IFS 120 M and in 1996, a second Bruker IFS 120 HR was bought. As a result, the observations have been continued (also by using the moon as light source) until today.
During the second half of the 1980s the first cryogenically cooled version of MIPAS (called MIPAS-B) was built to enable observations of the vertical distribution of chemical constituents independent of external light sources from high-altitude balloon platforms (Oelhaf et al., 1991). In 1991, a similar type of instrument (called MIPAS-STR) was integrated in the payload of the German Transall aircraft for observations of column amounts of trace gases along the aircraft's flight track. A modified version of MIPAS, suitable for operation in space (called MIPAS-Envisat) has been constructed as a core payload instrument for ESA's Envisat mission and was launched into orbit on 1 March 2002.
The MIPAS balloon project was launched in 1985. The first MIPAS-B instrument was developed to prove that the Double-Pendulum-Interferometer concept, a new configuration of the classical Michelson set-up, is also working in a cryogenic environment. This version was designed for limb emission sounding of stratospheric trace gases from stratospheric balloons. The MIPAS-B experiment was also thought as precursor for a space version of MIPAS. It flew four times successfully between 1989 and 1992, the latter two flights as part of the European Arctic Stratospheric Ozone Experiment (EASOE).
A new advanced instrument version, called MIPAS-B2, was designed and built in 1993 and 1994 (Friedl-Vallon et al., 2004). This instrument has been upgraded in various aspects compared to its predecessor, particularly regarding the pointing system and the spectral coverage. Its first flights (No. 1 and 2) took place in 1995 from Kiruna within the framework of SESAME (Second European Stratospheric Arctic and Midlatitude Experiment).
Flights No. 3 and 4 (1997) took place in the frame of the BMBF funded CHORUS project and have also contributed to the validation of the Japanese satellite instrument ILAS on ADEOS. Flight No. 5 and 6 (1997 and 1998) took place in mid-latitudes as part of the EU-funded CHELOSBA project. Additionally, data collected during flight 6 have been used for testing of on line processors being developed for the operational analysis of MIPAS-Envisat spectra. Flights No. 7 and 8 (1999) have contributed to the large EU-funded campaign activities called THESEO as part of the HIMSPEC project.
Flight No. 9 (January 2001) was performed well inside the arctic vortex. Sequences of nocturnal limb emission spectra were measured near 65°N and 70°N inside and outside a large PSC field. While for the southern limb scan no prominent features of polar stratospheric clouds could be recognized in the spectra, the data of the northern scan have been affected by a thick PSC layer.
In 2002, three flights were carried out. The first one, flight No. 10 (February) took place inside the arctic vortex around sunset. In September, flight No. 11 was performed from southern France within the validation campaign of MIPAS, GOMOS, and SCIAMACHY aboard the Envisat satellite. Finally, flight No. 12 (December) was carried out in the early winter under very cold conditions in the arctic lower stratosphere.
Two further flights were performed within the Envisat validation programme in 2003. The first one in March (flight No. 13) in the late winter arctic vortex and the second one (flight No. 14) for the first time under polar summer conditions (July). An Envisat Stratospheric Aircraft and Balloon Campaign (ESABC) was carried out in Teresina (Brazil). Here, the first MIPAS-B flight in the tropics was performed in June 2005 (flight No. 15) and the second one from the same location in June 2008 (flight No. 16) within the SCOUT-O3 project which was addressing scientific objectives associated with processes linking the tropical upper troposphere with the lower stratosphere. Flight No. 17, however, was performed again from Kiruna in the late arctic winter in March 2009. This was the first successful combined flight of MIPAS-B together with TELIS (TeraHertz Limb Sounder), a new sub mm-wave limb sounder. Another arctic flight from Kiruna together with TELIS was performed in January 2010 (flight No. 18) inside a very cold chlorine-activated vortex.
A further combined flight (No. 19) of these instruments, embedded in the ENRICHED project, was launched by CNES on 31 March 2011 from Kiruna at 0:46 local time. After a long ascent the balloon reached a maximum altitude of 35.4 km. It was cut at 7:00 local time after about 2:40 min at float and touched down in Russia at 7:40 local time.
The last scientific flight of MIPAS-B (No. 20), together with TELIS and mini-DOAS, was carried out from Timmins (Ontario/Canada) on 7/8 September 2014. The measurements were primarily aimed to measure reactive bromine in the stratosphere, including the most important compounds of the bromine family, BrO and BrONO2.
Pioneering work has been done by providing the first vertical profiles of key reservoir species like ClONO2 and N2O5 (von Clarmann et al., 1993, Oelhaf et al., 1994, Wetzel et al., 1995) and by studying the chlorine and nitrogen partitioning and budget inside the polar vortex (von Clarmann et al., 1995, Wetzel et al., 1997, and 2002, Stowasser et al., 2002, and 2003). In 1995, a strong denitrification of the arctic vortex was detected. Such denitrifications along with climate forcing of greenhouse gases may control efficiently the fate of the ozone layer (Waibel et al., 1999). Remote sensing of polar stratospheric clouds has been used to derive information on composition, volume and size parameters of the cloud particles (Höpfner et al., 2002). HO2NO2 data was taken to successfully check the inclusion of a near-IR photolysis channel in a stratospheric model (Evans et al., 2003). Spatio-temporal variations of NOy species, measured in the polar stratosphere, have been compared to calculations from a box model (Wiegele et al., 2009).
Several studies with regard to accumulated ozone loss (Konopka et al., 2007) and impact of intrusions of mesospheric air into the stratosphere (Engel et al., 2006, Müller et al., 2007) have been performed with the help of MIPAS-B data observed in late winter 2003.
For the first time, MIPAS-B has successfully measured in the ozone layer the chlorine monoxide dimer ClOOCl which plays an important role in polar stratospheric ozone depletion (Wetzel et al., 2010).The partitioning and budget of inorganic and organic chlorine species was derived from combined MIPAS-B and TELIS observations (Wetzel et al., 2015). Furthermore, the first stratospheric measurements of the diurnal variation in the inorganic bromine reservoir species BrONO2 around sunrise and sunset were recorded by MIPAS-B (Wetzel et al., 2017).
MIPAS-B is still involved in numerous validation activities for the space sensors ILAS-II aboard ADEOS-II (e.g. Ejiri et al., 2006, Irie et al., 2006, Nakajima et al., 2006, Wetzel et al., 2006, 2008), SMILES on the International Space Station (Sagawa et al., 2013), and MIPAS, GOMOS, and SCIAMACHY aboard Envisat (e.g. Cortesi et al., 2007, Höpfner et al., 2007, Kleinert et al., 2007, Ridolfi et al., 2007, Steck et al., 2007, Wang et al., 2007, Wetzel et al., 2007, Renard et al., 2008, Milz et al., 2009, Payan et al., 2009, Zhang et al., 2010, Wetzel et al., 2013, Eckert et al., 2016, 2017, Valeri et al., 2017).