ALMA Memo 415 Phase Correction using Submillimeter Atmospheric Continuum Emission

We discuss a phase correction method using total power from submillimeter/millimeter SIS receivers. The discussion is based on FTS measurements and model calculations of submillimeter/millimeter atmospheric emission under various weather conditions. Liquid water in the atmosphere (cloud or fog) limits the phase correction accuracy using the total power measurements. Comparison between millimeter and submillimeter total power phase correction shows that the sensitivity requirement is more easily met at submillimeter wavelengths under good atmospheric conditions (precipitable water vapor [pwv] < 1 mm), and the phase correction error due to liquid water is much less at these wavelengths. Simultaneous operation of millimeter and submillimeter receivers will further reduce the phase correction error appreciably.