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\item at the beginning of each observing night, the AAS must re-align the beam train so that beams of starlight arriving at the beam combiners meet the tilt and shear error budget;  \item during the night, the AAS must make fine adjustments to the alignment so that the tilt and shear error budget is maintained in the presence of thermal drifts, typically introduced by those optics located in temperature unstable environments;  \item when a new beam train is installed or configured, the AAS must allow for measurement of the "piston" term due to the optical path between the beam combiners and the telescopes, in order to allow for rapid acquisition of stellar fringes;  \item at the beginning of the night, the AAS must allow the pathlength differences between the fringe tracker and the science instrument to be measured so that these can be equalized. equalized using the switchyard mirrors.  \end{enumerate}