Improved In-Flight Pattern Retrieval by Reflector Deformation Fitting
The in-flight pattern measurements of a sub-millimetre space telescope may be improved by determining the actual reflector anomalies and then include the knowledge to these in the final pattern de-termination. The pattern measurements with a celestial object as source often have an insufficient signal-to-noise ratio for a pattern prediction outside the main lobe. Repeated measurements may improve this but even better is the possibility to extract data from different detectors operating at different frequencies.
With the Planck Space Telescope as example, simulations of a displaced and distorted reflector have been carried out for noise contaminated amplitude measurements of Jupiter by 5, respectively 10, different detectors. First, the main beams of the antenna patterns are retrieved in a regular grid. Here the accuracy is limited by the noise level. Then, by a Physical Optics optimization the actual distortions of the telescope’s reflector are determined so that the calculated radiation patterns of the antenna are correlated to the measured main beams. The patterns for the optimized and retrieved reflector geometry are shown to be precise at levels far below the noise floor in the direct measurements.
Publication: AMTA 32nd Annual Symposium (AMTA2010)
Place: Atlanta, Georgia, USA, 10-15 October, 2010