[mmaimcal] Summary of case for OSF interferometry

[Alwyn Wootten]

Folks,
Truth time is here--comments on the following?
Holdaway’s simple holography simulation package in AIPS++/glish
See https://wikio.nrao.edu/bin/view/ALMA/HoloGraphy
Using two-element interferometric holography and the brightest compact
celestial radio sources available, we will have enough sensitivity to
accurately set the panels near the center of the dish, and not at the edge
of the dish. Alternatively, using a larger cell size (0.4 m) which won't
permit panel setting, we can very accurately confirm the surface accuracy
of the dishes.
Discussion: The basic question: is it worthwhile to set up a correlator at
the OSF site to do two element holography on astronomical sources?
Note that second antenna is followed one month later by third—time for
interferometry at the OSF is very limited.
NOTE: if we want to do panel settings from astronomical holography at the
AOS, we will have to wait until we have 10 antennas.
Alternatives:
	Tower holography provides setting at one elevation.
       Photogrammetry provides measure of surface variation as f(el); has
worked better than expected at ATF (numbers secret?)
Out of focus beam maps have given good results at ATF (numbers secret?)
Out of focus holography has given poor results at ATF owing to limitations
of the evaluation receivers.  (Numbers secret?)
Need estimate of accuracy at OSF with ALMA receivers.
I think that the project might not establish an interferometer at the OSF
and be just as well off.