Minutes for meeting Mon, 1 February 1999 at 4pm EST.
Date: 1 February 1999
Time: 4:00 pm EST (2:00 pm Socorro, 2:00 pm Tucson)
Phone: (804)296-7082 (CV SoundStation Premier Conference phone).
Past minutes, etc on MMA Imaging and Calibration Division Page
Simon gave us a report on the site testing meeting which was held at the URSI meeting, along with an update on the activities.
Activity will be picking up at the site with visits for SMT FTS He refill, sonde launches, etc. If Bryan goes to the site in March, it would be good for him to inspect at least some of the sites for the 10km array pads.
After the meeting there was some email discussion of the problems associated with the VLA array naming convention. HAW sensed a consensus to name the arrays after their approximage diameters. I have changed these notes to reflect that convention, as a way of trying it on for size, so to speak.
Leonia has compared an optimal array (minimum sidelobes) with a non-optimal one for two source classes.
He simulated the UV data for the two array configurations using two source classes as a model. The simulation was done with different noise levels. In all cases the image was resrored by IMAGR and compared with model.
The image provided by the optimal array is better in all cases considered.
Leonia issued the MMA memo 247.
Leonia made a presentation at the calibration imaging meeting about simulation and his memo.
We have been asked to provide example layouts of the antennas in the LMA, using for example 50 x 12m antennas. These should be from the smallest configuration up to 10 km in extent. The Europeans are interested in 20km; a second step would be to investigate the practicality of this. Tamara has estimated what these new antenna parameters mean for our standard arrays--for example, the compact array may expand to 135m in size. This has ramifications, of course, for the HDF simulations and other work.
Tamara Helfer Notes on LMA configuration design:
We assume 48 antennas of 12m each, with a minimum separation of 1.25 D or 15m.
If we again take a filling fraction of .4 for D array, then the (circular) compact array diameter is about 130m, up from 95m for the 36x10m case. If we fix the large array at 3 km still, then we get a resolution scale factor of about 3.2 instead of 3.6, a 10% reduction.
As a starting point, I've chosen .3, 1 and 3 km array minimum and maximum annuli for donut configurations based on some guesses as to what are reasonable compromises between sidelobes and uniformity. Based on Adrian Webster's and John Conway's memos, the Europeans may not sign on for fixed arrays for the intermediate cases, but I think this is still a reasonable starting point for the combined array.
Let's discuss the simulation of the HDF some more. Examples are the SIRTF simulation. Min has produced an effort at his page and Jack Gallimore has also produced a simulation.
I updated the MMA history, which I put at our site. Any comments? I will abstract some point from this for a history slide.
SKA diagram of M101. Is this a weak galaxy? Why does the MMA/LSA fare so poorly here--or did they make a mistake. I thought we went to 7000 m^2 or whatever just so we could get 'normal, unevolved' galaxies like this at z=3!
Looks like the European-US meeting in Tucson may occur 21-23 Feb 1999. What MMA Imaging and Calibration tasks might the Europeans aid us in?
1. Investigation of 183 GHz phase correction systems. This would be a continuation of the current program, in which one 183 GHz radiometer is situated at each end of the 12 GHz interferometer baseline at Chajnantor.
2. Investigation of total power imaging modes. The continuing 'DREAM' mode and related modes at the JCMT, as well as characterization of 1/f noise in SIS receivers, could help us to understand problems associated with sensitive total power observing modes.
3. Soil sampling.
4. Configuration studies. There has already been sizable interest in this subject, resulting in several memos in the Memo Series. We need to put prototype 50 x 12m antenna configurations down on a plat of the site, up to 10km in size, for purposes of example. European collaboration in this and in imaging studies seems possible.
Note that the 12m '30th birthday meeting' will be of substantial interest to our group:
6- 9 Jun 'Imaging at Radio through Submillimeter Wavelengths' meeting in Tucson
As you may know, a meeting of U. S. and European scientists is being planned for the Fall of 1999 in Washington, D. C. The goal of the meeting is to review the scientific program planned for the joint array and how that program interacts with the science goals of other astronomical facilities expected to be operational at the time that the MMA/LSA becomes operational.
Please comment upon the prototype WWW page for the Science With A Large Millimeter Array meeting at:
Science topics for this suggestion were drawn from those identified by the 1997 Thaddeus committee (Task Group on Space Astronomy and Astrophysics, Committee on Astronomy and Astrophysics, Board on Physics and Astronomy, Space Studies Board, Commission on Physical Sciences, Mathematics and Applications, National Research Council) report A New Science Strategy for Space Astronomy and Astrophysics", or by McKee:
DECISION: 183 GHz or 22 GHz phase correction?
DECISION: Is a nutating secondary necessary?
DECISION: What is the effect of 1/f noise in the HEMT amplifiers of SIS receivers upon our ability to combine total power and interferometric images into a faithful representation of the sky?
A. Wootten: 3-6 Feb (12m observing) 8-9 Feb (MMA talk at SPECS conference) 16 Feb (43m observing) 20-24 Feb Tucson 22-30 May househubby 9 - 13 Jun CSO