New technique for retrieving pressure and temperature distributions in the Martian atmosphere from the infrared limb observations
Final Report Abstract
Due to the instrument originally intended to be used for this study, the TES spectrometer, having a noise level much higher than foreseen, an instrument not originally planned for scientific observation, the TES bolometer, was utilized instead. Additional work was necessary, both in the analysis of the composition of the instrument signal as well as in the technique used to retrieve pressure and temperature data from the signal. The work performed is estimated by the research team as a very successful one: (a) it introduced into the study of the Martian atmosphere an entire new, very important database of observations, namely the MGS/TES bolometer limb radiances of the middle and upper Marian atmosphere. It is worth noticing here that IR TES bolometer was not planned for atmospheric observations, but mostly for controlling the performance of the IR TES spectrometer – the core instrument of the TES experiment. However, due to a significantly higher signal-to-noise ratio compared to that of the TES spectrometer the bolometer collected important information about the thermal state of the Martian middle and upper atmosphere; (b) it led to the development of a new efficient algorithm for retrieving pressure and temperature information from the broadband limb observations of the middle and upper layers of the planetary atmosphere, accounting for the breakdown of local thermodynamic equilibrium (non-LTE). The latter required from the research team in Munich additional studies aimed at optimizing the algorithm performance to make it efficient enough for processing large volume of TES bolometric observations. This was achieved by implementing an “opacity distribution function” technique developed and applied in stellar astrophysics. It is worth stressing here that the ODF technique was successfully implemented both into the calculations of the non-LTE populations of the molecular levels and into the calculations of the broadband limb bolometer radiances. However, while the former implementation was planned in our preliminary study and foreseen in the proposal as the way to accelerate the non-LTE calculations, the need of the latter one was recognized only later due to the necessity of accounting for an extremely large number of spectral lines in modeling the broadband signal of the bolometer. From the point of view of the ODF technique implementation the work done represents a very good example of successful “technology transfer” from one research field, stellar astrophysics, to another one, namely to planetary atmospheres. This is particularly true if one takes into account that the ALI-ARMS code applied in this study and optimized to work as a core of the developed forward-fit scheme is based on the Accelerated Lambda Iteration (ALI), a technique also developed and applied in studies of stellar atmospheres done in our institute.
Publications
- Temperatures of Martian atmosphere in the altitude region 60–100 km retrieved from the MGS/TES bolometer infrared limb radiances. In: Proceedings of the Workshop on Planetary Atmospheres, November 6–7, 2007, Greenbelt, Maryland (2007)
Kutepov A. A., Feofilov A. G., and Smith M.
