Space infrared telescope pointing control system. Automated star pattern recognition

The Space Infrared Telescope Facility (SIRTF) is a free flying spacecraft carrying a 1 meter class cryogenically cooled infrared telescope nearly three oders of magnitude most sensitive than the current generation of infrared telescopes. Three automatic target acquisition methods will be presented that are based on the use of an imaging star tracker. The methods are distinguished by the number of guidestars that are required per target, the amount of computational capability necessary, and the time required for the complete acquisition process. Each method is described in detail

The application of aperture synthesis techniques to satellite radar altimetry

Radar altimetry over the ocean is now a well established discipline of satellite remote sensing, providing measurements of mean height, significant waveheight and surface wind speed. In contrast, radar altimetry over non-ocean surfaces, to obtain topography of land and polar ice sheets, is still a new idea. The difference between these two situations is that the ocean surface is essentially flat with a very small vertical extent, so a broad-beam pulse-limited mode radar altimeter having a relatively small antenna is sufficient to give very accurate measurements of the ocean mean height. However for topographic surfaces, variations in the elevation can be much higher, and using a conventional altimeter causes serious problems, such as interpretation error and misregistration of a measured range, which cannot be normally corrected. To avoid these problems, a considerably narrower beam antenna has to be used to localise the surface under observation. This requires very large antenna structures, which would be both complex and costly. This thesis investigates the application of aperture synthesis techniques to narrow-beam altimetry as an alternative to physically large antennas, to achieve high along-track resolution. It considers the analysis of the involved factors and design parameters, errors, data handling and signal processing requirements and methods for fixing the antenna beam accurately with the ultimate goal of providing a dynamic global altimetric database. In the second half of the thesis, an experimental aircraft-borne altimeter is examined. Details of the design, construction and evaluation of a prototype system are described. This radar includes several novel features, such as aperture synthesis with full-deramp range processing, digital chirp generation, bistatic FMCW operation and off-line digital signal processing. Also a series of experiments are arranged for this radar to examine its performance to process the signature of corner reflector targets, and consideration is given to the extension of these ideas to a satellite-borne instrument