ALMA Memo #277

Sensitivity Loss versus Duration of Reconfiguration and ALMA Array Design

Keywords: time loss, reconfiguration, antennas

The analysis of effective time loss during reconfiguration by Guilloteau (1999) is re-examined for the robustness of his conclusion that the time loss is minimized by moving only a small number of antennas each day. I am able to reproduce this analysis and found that this conclusion is independent of the assumptions on antenna move time and the length of post-move calibration. I find, however, this optimization to compete against the total duration for reconfiguration, which is a serious concern for the reconfiguration to and from the largest configuration. A more fundamental problem is that this concern over reconfiguration efficiency is dwarfed by the concern over observing efficiency in most cases, as previously shown by the cost-benefit analysis by Holdaway (1998) and by Yun & Kogan (1999). A stronger case will be made if such a gradual reconfiguration scheme can be shown to achieve a high observing efficiency as well.

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Last modified:1999-dec-09