The Instrument MIMOS II

The instrument MIMOS 11 is extremely miniaturized compared to standard laboratory Mossbauer spectrometers and is optimized for low power consumption and high detection efficiency (see Sect. 3.3) and [326, 327, 336-339]. All components were selected to withstand high acceleration forces and shocks, temperature variations over the Martian diurnal cycle, and cosmic ray irradiation. Mossbauer measurements can be done during day and night covering the whole diurnal temperature 

To minimize experiment time a very strong Co/Rh source was used, with an initial source strength of about 350 mCi at launch. Instrument internal calibration is accomplished by a second, less intense radioactive source mounted on the end of the velocity transducer opposite to the main source and in transmission measurement geometry with a reference sample. For further details, see the technical description in Sect. 3.3. 

The MIMOS II Mossbauer spectrometer sensor head (see Sect. 3.3) is located at the end of the /nstrument Deployment Device IDD (see Fig. 8.27) On Mars-Express Beagle-2, an European Space Agency (ESA) mission in 2003, the sensor head was also mounted on a robotic arm integrated to the Position Adjustable Workbench (PAW) instrument assembly [344, 345]. The sensor head shown in Figs. 8.28 and 8.29 carries the electromechanical transducer with the main and reference Co/Rh sources and detectors, a contact plate, and sensor. The contact plate and sensor are used in conjunction with the IDD to apply a small preload when it places the sensor head, holding it firmly against the target. 

Because of the complexity of sample preparation, backscatter measurement geometry is the choice for an in sim planetary Mossbauer instrument [327]. No sample preparation is required, because the instrument is simply presented to the sample for analysis. Both 14.41 keV y-rays and 6.4 keV Fe X-rays are detected simultaneously. 

MIMOS II has three temperature sensors, one on the electronics board and two on the sensor head. One temperature sensor in the sensor head is mounted near the internal reference absorber, and the measured temperature is associated with the reference absorber and the internal volume of the sensor head. The other sensor is mounted outside the sensor head at the contact ring assembly. It gives the analysis temperature for the sample on the Martian surface. This temperature is used to route 

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The instrument MIMOS II will be part of the upcoming ESA-NASA space missions ExoMars in 2018, and the Russian Space Agency sample return mission Phobos Grunt scheduled for launch in 2011 to visit the Mars moon Phobos. 

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