MMA Memo #272

IMAGE FIDELITY: IMPLICATIONS FOR ALMA

M.C.H. Wright (Radio Astronomy Laboratory, University of California, Berkeley, CA 94720)

August 31, 1999

Keywords: imaging, image fidelity, mosaicing, heterogeneous arrays, single dish observing

This memo presents the case for adding smaller antennas to the ALMA array. Smaller, higher precision antennas are better able to exploit the excellent submillimeter potential of the 5000 m altitude site, and are better matched to the angular size of many submillimeter sources. Model studies show that the image fidelity of mosaiced observations with the ALMA array will be limited by pointing and surface errors. This can be understood in terms of the errors in the spatial frequencies derived from the mosaicing process. Spatial frequencies derived from the outer parts of the antennas, which serve to knit together the mosaic, may have larger errors than estimated from the overall surface and pointing RMS values. Adding smaller, higher precision antennas is a unique contribution which a Japanese collaboration could make to improve the submillimeter performance of ALMA, and also the image fidelity of mosaiced millimeter observations.

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Last modified: 01 September, 1999