Description of the payload
It is an advanced Fourier Transform Infra Red (FTIR) spectrometer specially tailored to the operation on a stratospheric balloon gondola. It allows precise limb emission sounding of chemical constituents related to the stratospheric ozone problem and the greenhouse effect. This method is appropriate to obtain vertical profiles of ozone and a considerable number of key radicals (NO, NO2), reservoir species (HNO3, N2O5, ClONO2, and HO2NO2) as well as source gases (CH4, N2O, H2O, CFC-11, CFC-12, CFC-22, CCl4, CF4, C2H6, and SF6) simultaneously, with an altitude resolution of 2 to 3 km.
The MIPAS-B experiment was also thought as precursor for a space version of MIPAS actually installed onboard ENVISAT.
The instrument is divided in five operational segments:
(1) the gondola,
(2) the line-of-sight (LOS) stabilization and reference system,
(3) the cryogenic spectrometer,
(4) the on-board electronics, and
(5) the ground control equipment
The gondola is a frame construction, developed by the Geneva Observatory, combining high stability and safety with relatively low weight and easy servicing.
The LOS system is based on a miniaturized inertial navigation system with embedded GPS (Global Positioning System) that provides the attitude and heading reference of the instrument frame needed for the control loop to maintain the LOS within 300 m at the tangent point. A CCD star camera takes images of stars in the direction of the LOS that are used as absolute reference.
The spectrometer consists of a three-mirror off-axis telescope, a double-pendulum interferometer, and a four channel liquid-He cooled infrared detector system. The heart of the instrument is the double pendulum interferometer, a modification of the classical Michelson set-up. The four-channel detector system allows the simultaneous coverage of the most important absorption bands of ozone-relevant molecules between 5.2 and 13.3 µm.
The analogue data is sampled on-board, mixed with the information of the other channels and the housekeeping data, and sent to ground via telemetry at a data rate of 250 kbit/s. An uplink connection of 1200 bit/s ensures full commandability of the instrument during flight.
On ground, the raw data is split up again and stored immediately in a data base. At the same time, housekeeping data and interferograms can be viewed and processed to allow on-line evaluation of measured data and of instrumental health.
Details of the balloon flight and scientific outcome
Launch site: European Space Range, Kiruna, Sweden
Balloon launched by: SSC
Balloon manufacturer/size/composition: Open balloon model 400z Zodiac - 400.000 m3
Payload weight: 1200 kgs
The balloon was launched by dynamic method with assistance of the launch vehicle HERCULES at 01:46 local time on 24 January 2010.
After a nominal ascent phase, the balloon reached the float level of 34 km at around 5:00, heading towards the Baltic sea for several hours before it almost stopped and turned his path into Finland. Around 13:00 the valve was opened for a slow descent down to 25 km, then the gondola was cut at 14:40 and safely landed 40 km East of Kuusamo, Finland.
Two days later the gondola was back in Esrange in good shape. All systems could be switched on and were working again.
This was the flight # 18 of MIPAS-B2. The scientific objective of this flight has been two-fold: One goal has been validation of the space experiments ENVISAT and SMILES. The other goal has been to measure the time-dependent chemistry of chlorine and bromine, and to achieve the closure of chemical families (NOy, Cly, Bry, HOx). The measurements have been performed using remote sensing spectroscopic techniques covering the spectral range from the UV via the IR to the MW. Altogether these techniques allow the measurement of more than 30 atmospheric species.
As piggy back payloads were included two others instruments in the gondola. TELIS (Terahertz and Submillimeter Limb Sounder) a 3 channel cryogenic heterodyne receiver developed by DLR with high sensitivity and stability, which like MIPAS is a limb sounder measuring reactive species, water isotopomers and some atmospheric tracers with a vertical resolution of about 2 km. The second one was mini-DOAS (OSAKAR) developed by the IUP Heidelberg, a two channel automated UV/vis Limb scanning spectrometer created to measure measure time dependent profiles of UV/vis absorbing atmospheric radicals.
The balloon was launched right into the centre of the cold chlorine-activated vortex. Thanks to the meteorological situation and the timing of the balloon operations enabling more than 12 hours of measurements the following tasks could be achieved:
(1) to measure the time-dependent chemistry of activated chlorine (ClO and ClOOCl) from the night-time equilibrium until day
(2) to measure the almost complete partitioning and budget of the NOy and Cly families
(3) to match the overpasses of the ENVISAT and SMILES satellite observations
(4) to observe the same air masses as the Geophysica aircraft on the same day.
Both MIPAS and TELIS worked well, and the quick-look at the recorded spectra is very promising. Power problems prevented the mini-DOAS to measure well into daytime, unfortunately.
From a quick-look at the spectra we summarize qualitatively:
a) a significant redistribution of HNO3 pointing at denitrification above about 20 km and renitrification below
b) a strong chlorine activation with very little amounts of ClONO2 and enhanced ClO
c) a relatively slow build-up of ClO after sunrise.
(Extracted from the preliminary report of the flight)
External references and bibliographical sources