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.
Launch site: European Space Range, Kiruna, Sweden
Balloon launched by: Centre National d'Etudes Spatiales (CNES)
Balloon manufacturer/size/composition: Zero Pressure Balloon
Campaign: EASOE (European Arctic Stratospheric Ozone Experiment) was undertaken in the northern winter of 1991-92 to study the processes in the Arctic which lead to ozone destruction and their connection with reduced ozone at northern mid-latitudes.
The balloon was launched by CNES using the auxiliary balloon method on March 14, 1992 from Esrange. Apart from minor electrical disturbances, the performance of all systems was excellent. At 03:37 utc, on March 15, 1992, during cut-down operation, the shaft of the azimuth decoupling system broke, and the gondola performed a free fall from an altitude of 32 km. At impact on a frozen lake near Nikel, Russia the whole instrument was completetly destroyed.
This was the fourth and last flight that involved an early version of the instrument known as MIPAS-B1 and the second flight from high latitudes in the framework of a major atmospheric research campaign. As mentioned above, the destruction of the instrument impeded the evaluation of the telemetered data by the loss of the film of the star-camera, which would
have served as absolute reference for the pointing data.