Wilson, Daniel
(2014)
Quasi-Optical Modelling of Telescope
Systems for Planck and STEAMR.
PhD thesis, National University of Ireland Maynooth.
Abstract
This thesis is concerned with the high-frequency quasi-optical modelling of telescope
systems, with special attention paid to the Planck satellite, but further work is also
performed on the Stratosphere-Troposphere Exchange And climate Monitor Radiome-
ter (STEAMR) and the Far Infrared Instrument (FIRI). The primary work surrounds
the modelling of far sidelobe (FSL) patterns of the Planck telescope, with a view to
replicating features seen in some of the difference maps made by the 857-GHz channel
of Planck's High Frequency Instrument (HFI). This is done using a variety of techniques
in a number of software packages. The General Reector Antenna Software Package
(GRASP9) is used for accurate characterisation of the FSLs using two analysis methods: Physical Optics (PO), and Geometrical Optics (GO) with the Geometrical Theory
of Diffraction (GTD). This is then compared against two simplified paraxial lens models
of the telescope, namely the Projected-Aperture (PA) technique and Gaussian Beam
Mode Analysis (GBMA). PA is performed by Fresnel integration of fields from source
to sky, while GBM requires decomposition of a field into a set of Gauss-Laguerre modes
which are propagated from source to sky using a ray matrix formalism. The motivation
for analysing the Planck FSL structure is to test the assumption that features in the
difference map are a result of manufacturing imperfections in the detector horns. To
test this hypothesis a number of altered horn geometries are modelled using the NUI
Maynooth Experimental Physics departments in-house waveguide mode-matching soft-
ware called SCATTER, and these are then used in the analysis of the telescope system.
Further use of SCATTER is illustrated in work on ultra-Gaussian horns for STEAMR,
and here it is tested against commercial waveguide modelling software Microwave Wizard
(uWW).
Further modelling is performed for the Cardiff test-bed of the Planck telescope simulator,
which was used for qualification of the Planck HFI
ight horns pre-launch. Here we test
the hypothesis that manufacturing imperfections could be missed if the effects on beam
pattern were imperceptible to measurement. This is done using GRASP9, as is the
modelling of FIRI, a multi-beam spectral/spatial interferometer which will hopefully
break current constraints on angular resolution obtainable at infra-red wavelengths.
In general, this thesis aims to provide insight into the modelling of quasi-optical telescope
systems, with particular emphasis on multi-moded systems, providing useful information
for future data analysis by the Planck project team.
| Item Type: |
Thesis
(PhD)
|
| Keywords: |
Quasi-Optical Modelling; Telescope Systems; Planck; STEAMR; |
| Academic Unit: |
Faculty of Science and Engineering > Experimental Physics |
| Item ID: |
5402 |
| Depositing User: |
IR eTheses
|
| Date Deposited: |
16 Sep 2014 15:56 |
| URI: |
|
| Use Licence: |
This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available
here |
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