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The in-flight pattern measurements of a sub-millimeter space telescope may be improved by determining the actual reflector anomalies, and then including the knowledge of these in the final pattern determination. The pattern measurements with a celestial object as a source often have an insufficient signal-to-noise ratio for pattern prediction outside the main lobe. Repeated measurements may improve this, but even better is the possibility of extracting data from different detectors operating at different frequencies. With the Planck Space Telescope as an example, simulations of a displaced and distorted reflector were carried out for noise-contaminated amplitude measurements of Jupiter by five and 10 different detectors, respectively. First, the main beams of the antenna patterns were retrieved in a regular grid. Here, the accuracy was limited by the noise level. By a Physical Optics optimization, the actual distortions of the telescope's reflector were then determined, so that the calculated radiation patterns of the antenna were correlated to the measured main beams. The patterns for the optimized and retrieved reflector geometry were shown to be precise at levels far below the noise floor in the direct measurements.
Date of Publication: Oct. 2011