Prof. Patrick Irwin

Abstract:

The spectral band data derived by Strong et al. [1993] for laboratory-measured transmission spectra of hydrogen-broadened methane at 10 cm-1 resolution have been fitted with k coefficients over a wide range of pressures and temperatures representing those likely to be encountered in the atmosphere of Jupiter. The mean fitting error is found to be only 2.0×10-3 in transmission. These data are essential for the scattering calculations likely to be necessary for analysis of the data from the Near Infrared Mapping Spectrometer aboard the NASA Galileo spacecraft. The new data have significant advantages over those previously derived by Baines et al. [1993] in that they cover a wider spectral range, are applicable to longer paths, and also apply to the hydrogen-broadened case, which is the dominant broadening mechanism in this atmosphere. A similar table has also been calculated for the self-broadening case for comparison. Copyright 1996 by the American Geophysical Union.

Abstract:

A concept has been developed for a remote sensing experiment to investigate the physics of the Martian atmosphere from a spin-stabilized orbiter, like that planned for the InterMarsNet mission. Using coincident infrared and microwave channels and limb-to-limb scanning, it can map the planet much more extensively than previously in temperature, atmospheric dust loading, and humidity. When combined with one or more surface stations measuring the same variables, the sounder experiment can contribute to major progress in understanding the general circulation and dust and water cycles of the atmosphere of Mars, and the characterization of medium-scale meteorological systems. Copyright © 1996 Elsevier Science Ltd.

Abstract:

A radiometric experiment was conducted to investigate the thermodynamic behaviour of the H2O and CO2 pressure modulated cells of the Pressure Modulator Infrared Radiometer (PMIRR) which flew on "Mars Observer" in 1992. The wave forms and phases of the transmission, emission, pressure and piston position cycles, together with the mean absorption were, for the first time, all measured during the same experiment. The measured transmission and emission cycles were used to calculate the phase and amplitude of the temperature cycles and were found to be super-adiabatic for both cells, in reasonable agreement with a thermal diffusion model. Anomalies were seen in the H2O modulator driving frequency, as has been observed by other authors, but none were evident in the measured cell wave forms suggesting that the water vapour behaves as an ideal gas in the cell. © 1994.

Abstract:

The fabrication of the filters for the two longest wave channels of the Pressure Modulator Infra-red Radiometer (PMIRR), launched in September 1992 on Mars Observer, was not possible using conventional multilayer dielectric techniques. Thus the extension of far-infrared/microwave mesh filter designs was investigated using a new dielectric spacing material. Test filters were designed and fabricated and, using their measured transmission spectra, a new model of the behaviour of resonant meshes in both air and dielectrics was developed. The low transmission of these filters in the end made them unsuitable for PMIRR but the model provides a useful design tool for future dielectric spaced filters providing a new, less absorbing dielectric can be found. © 1993.