Science IPT NA 2005 Feb 8
Comment on Bacmann and Guilloteau. 2-3% is the best that can be done for amplitude
calibration. MH: pretty pessimistic numbers for phase flcs and water. Worst
conditions go to 90 GHz and best to 650 GHz. Fluctuations are pessimistic.
Study of their numbers suggests that they correspond to 4d rms on 300m baseline.
This is moderately bad at 11.2 GHz. Sky fluctuation level of 0.67K and kappa
of 23 milliK per micron implies sigma of 254 microns which at the appropriate
el angle of 36 degrees. 1 degree is 74 microns.
Simulation plans. Configurations. Plan to study a suite of configurations
40, 43, 46 element configurations. Numbers as low as 36 or as high as 56 might
be considered. Could depopulate Conway configuration. This becomes nonoptimal
for sparse arrays. New configuratons created without topography constraints for
36 to 56 antennas using Boone algorithm. Very short baselines kept in each
configuration to avoid holes in the uv plane dominating. Thermal noise included.
We don't need to study the radiometry equation, so lets study how the image
degrades at the same noise level for each configuration. One doesn't want to
integrate below certain hour angles, +/- 2 hours is used. Each smaller configuration
repeats until enough S/N (so no new unique uv samples are added, just integration.
Noise levels: 100::1, 1000::1 10000::1. Presumably in the first, thermal noise
will dominate. In the latter, deconvolution errors will dominated. In the middle
we should get something real. M31 HII region image and M51 Halpha image are
being used. Preliminary results must be out by the end of next week. Configurations
done, scripts in place, will start performing simulations tomorrow.
BG: Late 1998 the MMA was going to be 36 antennas.
- 08 Feb 2005