MMA Memo: 225: Radiometer Calibration at the Cassegrain Secondary Mirror
نویسندگان
چکیده
The technique presently used at most millimeter telescopes is the "Chopper Wheel Method" introduced by Penzias and Burrus (ARAA, 1973, 11,51), in which the output de ection of an observed source is compared with the di erence between the sky brightness and that of an ambient temperature load. The physical temperature of the absorbing atmosphere is then taken to be the same as the ambient load or a mean model of the atmosphere is used. The method is convenient to use, and absolute accuracies of a few percent are typically obtained. Obtaining accuracies at the level of 1% or better requires the use of two black-body loads.
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