Sensitivity of the Band 1 - Incredible

The point source sensitivity of the Band 1 would exceed that of the UPGRADED VLA! There is less total collecting area, but the higher aperture efficiency (>2 x ) more than makes up for it. The much better site and cleaner optics helps further. The field of view of ALMA is 25/12 times larger than the VLA. For a given point source sensitivity the surveying speed of ALMA will be more than 20 times faster than the upgraded VLA. Interesting in its own right and very important for galaxy surveys, CMB foreground experiments, dust surveys, etc. ALMA sensitivity will be superb and unparalleled for arcminute scales at Band 1. A simple estimate including ONLY baselines from nearest neighbor telescopes gives 2 $\mu$K in one hour and an arcminute beam. There are 2.5 x 64 nearest neighbors in a close pack configuration. Of course, for imaging it is much better to include all baselines - see simulations. The bottom line is that it is fantastic. IMPORTANT NOTE: ALMA does not replace the VLA! The VLA has much higher resolution. Together they cover both the N and S hemispheres. The VLA will excell for detailed studies of compact objects (AGN, stellar accretion disks, etc. ALMA will find which objects are worthy of higher resolution studies (eg., survey star forming regions for disks, galaxies, etc.).