Remote sounding of the Martian atmosphere
Abstract
This thesis describes the development and characterization of the optical elements for six channels of the Pressure Modulated Infrared Radiometer (PMIRR) due for launch on Mars Observer in 1992. This instrument uses two pressure modulators, one containing CO2 for temperature sounding and the other containing H2O. The CO2 gas sample is enriched in some isotopes to allow sounding of the deep atmosphere. The dynamic equilibrium between these isotopes was investigated using infrared spectroscopy to measure surface effects, reaction rates and stability. The reaction rate was found to be increased by the presence of a sieve and having verified the flight mixture to be in stable equilibrium, the composition was determined. The fabrication of the filters for two longest wave channels was not possible using conventional multi-layer dielectric techniques. Thus the extension of far-infrared/microwave mesh filter design was investigated. Test filters were designed and fabricated and, using their measured transmission spectra, a new model of the behavior of meshes in both air and dielectrics was developed. The low transmission of these filters made them unsuitable for PMIRR but the model will be important for future designs if a new, less absorbing, dielectric can be found. To verify the spectroscopy and the modelled behavior of the pressure modulated cells (PMC's), the waveforms and phases of the transmission, emission, pressure and piston cycles were simultaneously measured for the first time for any PMC, together with the mean absorption. Although anomalies were seen in the H2O PMC driving frequency, as have been observed by other authors, none were evident in the cell waveforms. A thermal diffusion model was developed and used to calculate temperature cycles throughout the cells. These were in good agreement with emission measurements made using the cylindrical H2O cell and acceptable for the conical CO2 cell.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1991
- Bibcode:
- 1991PhDT.........1I
- Keywords:
-
- Atmospheric Sounding;
- Atmospheric Temperature;
- Infrared Radiometers;
- Infrared Spectroscopy;
- Mars Atmosphere;
- Mars Observer;
- Remote Sensors;
- Spacecraft Instruments;
- Carbon Dioxide;
- Channels (Data Transmission);
- Fabrication;
- Infrared Filters;
- Microwave Filters;
- Modulators;
- Thermal Diffusion;
- Water;
- Lunar and Planetary Exploration