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 > On Jan 17, 2016, at 2:59 PM, Josh Dillon <[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 >> >
