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MMA Memo #178

Effects of Pointing Errors on Mosaic Images with 8m, 12m, and 15m Dishes

M.A. Holdaway [1]

August 10, 1997

Keywords: mosaicing, pointing errors, image quality, LSA-MMA collaboration

To better understand the tradeoffs involved in the various LSA-MMA collaborative arrays under discussion, we have revisited the effects of pointing errors on mosaic images. Pointing drifts which are linear in time and the same for all antennas (such as may be induced by thermal effects) can be back-interpolated during post processing to determine the actual mean pointing position of the array. The pointing errors are then dominated by wind-induced pointing errors, which are assumed to be systematic across the array, and random residuals from the removed pointing drift. Using this new pointing error model, we investigate the effects of pointing errors on mosaic imaging with arrays of 40 8 m antennas with 1 arcsecond errors, 27 12 m antennas and 60 12 m antennas with 1 arcsecond errors, and 35 15 m antennas with 1.5 arcsecond errors. We find that the 8 m antennas mosaic pretty well even into the submillimeter, the 12 m antennas begin to fail in the submillimeter, and the 15 m antennas do a poor job mosaicing even at frequencies as low as 230 GHz. With our pointing error model, there is little difference between the imaging quality of an array of 27 antennas and 60 antennas. Adding typical phase errors to the observations does not change the results as the imaging is limited by pointing errors.

[1] NRAO

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Last modified: 09 December, 1999