Hi Dave, A minor comment on the time line. We can’t really do a deep foreground survey without some longer baselines. In particular in year two we’ll only have ~1/2 degree imaging under this deployment plan and that could raise a red flag with a reviewer. Easiest fix is to say we’ll start foreground characterization in year 2, leaving it a bit vague.
Best, Miguel > On Jan 18, 2016, at 10:44 AM, DAVID DEBOER <[email protected]> wrote: > > Hi - regardless of the configuration, we need to finalize the build-out > schedule. In the pre-proposal, we indicated that we would build the complete > core, then build the out-riggers. We can remain a bit ambiguous on this in > the proposal, but we will have to decide at some point. In the new config > there are 30 outriggers. > > Here is the proposal schedule (minimal modification needed from the > pre-proposal) and below is an image showing a presumed core-first build-out. > > Year 1: HERA-37 observing and build-out to 125. Characterize system. > Year 2: HERA-125 observing and build-out to 243. Perform deep foreground > survey. Deploy first nodes and update infrastructure. Commission hardware. > HERA-37 results. > Year 3: HERA-243 observing and build-out to 350. Detect EOR power spectrum > in HERA-125 results. > Year 4: HERA-350 observing. Characterize power spectrum, constrain EOR > astrophysics in HERA-243 results. > > Dave > > <PastedGraphic-18.png> > > >> On Jan 17, 2016, at 2:59 PM, Josh Dillon <[email protected] >> <mailto:[email protected]>> wrote: >> >> Are you talking about the dark pixels? That may be a pixelization effect, >> though the others have something similar (if you look closely). Also, I'm >> not worried about dark pixels, since they don't contribute to the confusion >> limit. Remember that this is a log scale (spanning 4 orders of magnitude). >> >> -Josh >> >> On Sun, Jan 17, 2016 at 2:46 PM, Peter Williams <[email protected] >> <mailto:[email protected]>> wrote: >> Hi Josh, >> >> The earth-rotation-synthesis version of the synthesized beam for >> configuration (c) [Figure 5c, right panel] seems to have a grating pattern >> in the sidelobes that's not present for configurations (a) and (b). I don't >> feel like I have a great sense for what the practical effect of that might >> be, but it seems potentially worrisome for imaging. Do you have a sense of >> where that comes from? >> >> Peter >> >> On Sat, 2016-01-16 at 13:23 -0800, Josh Dillon wrote: >>> Dear HERAtics, >>> >>> Aaron and I have been working on investigating how to arrange the >>> “inriggers" and outriggers for HERA. In particular, we’ve been interested >>> in two questions: 1) how do modifications to the configuration affect >>> imaging? and 2) how do they affect the ability to redundantly calibrate the >>> array (including outriggers) using Omnical? That work will become a paper >>> relatively soon (hopefully, before the proposal goes in). >>> >>> The key result is an idea for an array that includes a change to the array >>> core. Basically, I want to split it up into three segments, each relatively >>> displaced by less than the minimum baseline length. This is something we >>> should talk about as a collaboration, so I’d like to give everyone >>> something to think about before the next telecon. >>> >>> I’ve attached the current draft of that paper (which is just an abstract, >>> outline, figures, and captions right now) that helps lay out the argument. >>> Basically, the proposed configuration (which is configuration (c) in the >>> paper) is more robustly calibratable with Omnical, produces lower >>> calibration errors, and modestly suppresses sidelobes. >>> >>> The key figures to look at are 1, 2, 3, 4, 10, and 11. The first four show >>> the proposed configurations and the instantaneous baseline redundancy >>> patters they produce. Both configurations (b) and (c) are designed to tile >>> the uv plane nicely, putting new baselines where information is sparsest. >>> Figures 10 and 11 show the expected gain errors on the antennas after >>> logcal, both with and without the outriggers. The other figures have to do >>> with imaging, where the effect is more subtle, and are harder to understand >>> without the supporting text that I still need to write. >>> >>> Perhaps the most surprising result is that my original attempt to produce >>> perfectly tiled sub-grid baselines (see Figure 2b) actually leads to larger >>> calibration errors throughout the entire core by approximately 10%. That’s >>> because Omnical is trying to solve for a lot more visibilities with very >>> little information about them. That’s the main reason I think the >>> split-core is preferable to the kind of “inriggers" proposed in >>> configurations (a) and (b). The split core also allows for complete >>> simultaneous uv-coverage at triple density out to ~400 meters. >>> >>> In case anyone is curious or wants to try doing a calculation with them, >>> I’ve attached text files with positions of the split-core + outriggers >>> (HERA-361). I’ve also attached a slightly more symmetric version with 11 >>> core antennas removed (HERA-350), that currently Dave, Aaron, and I favor. >>> >>> Of course, I welcome any feedback. Enjoy your long weekend (of proposal >>> writing)! >>> >>> -Josh >>> >> >
