UBC Theses and Dissertations

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UBC Theses and Dissertations

The behavior of the map mirror with changes in temperatures as determined by double exposure holography Jackson, Miranda Sylvia


Changes in shape with temperature, recorded using holographic interferometry, of a prototype MAP reflector are reported. The temperature of the reflector is changed between holographic exposures, so that deviations in the shape show up as fringes of interference between the light from the two images. This method can detect shape changes on the order of half a wavelength of He-Ne laser light (632.8 nm), and when analysis is performed on the image, shape changes of 0.02 microns and less are measured. A change in shape of approximately 4 microns over the entire surface is observed when the temperature of the reflector is changed by approximately 1 K from room temperature. This is insignificant compared to the figure tolerance (A/60). However, this effect may become significant when the temperature is reduced to approximately 50K in space, and therefore, the aluminum in the honeycomb material will be replaced by paper on the MAP satellite. The aluminum honeycomb structure is found to deform the surface with an amplitude of 0.008 to 0.015 microns in a regular pattern, when the temperature changes by 1 K , and this will produce sensitivity in the sidelobes of 1 0 - 7 of the main beam at 40°. This is not expected to affect the data for sources such as the earth, the moon, Jupiter, or the Milky Way, and the sun is expected to be hidden behind the instrument at all times and to never to appear at that angle from the main beam.

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