AGENDA
BAORadio/Tianlai Telecon & TAC Hacksession
7:30 AM Madison - Begin regular Tianlai Zoom call - (8:30 AM Providence, 2:30 PM Paris, 7 PM India, 9:30 PM China)
- summary of hardware tests of correlator. Tests on (both dish and) cylinder correlators? - Jixia
- see Jixia's slides below
- is it possible to compute an effective coupling (S21) coefficient by comparing the DC offset in the cross-correlation signal (as in slide 5 and 6) to the DC level of the auto-correlation signals?
- Anh & Santanu could do the same thing - compare [5H, 7V] in AlgoSCR paper with [5H 7H] or [5V 7V]
- update on low-z simulations - Olivier & Reza
- John P. knows how to use their Sophya pipeline; Lily and Yanlin could use this for simulations
9:15 AM - Begin Hacksession in 2104 Chamberlin Hall; Zoom call continues all day
- NCCS/GAIA cross-correlation - Olivier
- files are in here: https://box.in2p3.fr/index.php/s/e6KL7Q7zKZiPCkL , which includes:
- catalog.csv a CSV file containing the result of a matching of part of the NCCS (the cleaned version) and GAIA catalog.
- README a file describing the variables listed in the above csv file inspired by the description of the NCCS catalog in vizir at CDS : https://cdsarc.cds.unistra.fr/viz-bin/ReadMe/J/MNRAS/443/725?format=html&tex=true#sRM-F.45 Look also to tables 2 and 3 in arXiv1406.4153 for more explanations.
- Olivier added to the cleancat records two set of variable for the nearest and next-to-nearest neighbor star fond in GAIA (DR3 early release). The distances to gaia stars should be useful to select extragalactic objects for our WIYN observations. I can enlarge if/when needed the initial selection from the NCCS.
- Olivier also put some plots in this folder.
- Olivier volunteered to check for stars in results from WIYN survey to check consistency
- analog electronics design - question from Siddharth about how to balance gain before the mixer and after the mixer for 5 GHz interferometer under construction at IITI. See attached figure below. Will provide specs on parts and send diagram to John M.
- advice for new users of Tianlai01 and TLPipe (especially Samit Pal, Harsha Tanti, Siddharth, Abhirup at IIT-Indore)
- Siddharth has successfully submitted a request (today) for access to Fermilab computing
- Siddharth is trying to install TLPipe (Python 2 version). John M. warns of broken dependencies. Tim Rehm converted TLPipe to Python 3 successfully
- John M. asks: what development do we want to do on TLPipe? What version of Python.
10:00 AM - WIYN survey
- update on WIYN analysis so far - John, Albert, Revsen Karaalp (Brown)
- planning for next observations - Greg, Jocelyn Chu (Brown)
- Albert can do March 7 and 9; Greg can do May 8
- maybe Jocelyn can train on March 7 to observe on later dates
- Siddharth volunteered his team to participate as well.
- observers need good internet connection and to connect via VPN
- need decision from WIYN about who is a 'qualified observer' and whether overseas observers are possible - Peter will check
- Jocelyn showed table of tiles. Many have ~ 20 dim objects that haven't been observed yet and a few brighter objects. Priority is get the bright objects, but assign fibers to the dimmer objects as well (as long as there aren't so many that they interfere with the bright objects.
- Albert suggested getting dimmer objects in regions with high extinction as well
- Olivier suggests increasing area, but this will require much more observing time (2-3 more years to double area) unless we can get a different instrument, such as MMT
- High priority is to publish something about the current survey; maybe we can generate enough interest to expand with another instrument: MMT?
11:00 AM - Coffee
- plans for verification of some redshifts with objects in NED catalog - Lily Robinthal(UW)
- Albert suggests downloading all NED objects in the target volume, then search on those objects as a function of separation
- could search other catalogs:
- WISE satellite catalog - might contain redshifts added after the mission
- Brent Tully local galaxy survey might cover low redshift end z << 0.07
12:00 N - Lunch at Aldo's/WID
1:30 PM - Cross-coupling simulations and correlated noise analysis - David Kwak/ John Podczerwinski (UW)
- David reminded us that spectrum of coupling between pairs of zenith-pointing dishes maintains shape and falls with distance as ~ 1/r2
- Delay spectrum of these S21 plots didn't seem to show a signal at interdish spacing
- Have we done delay spectrum of the nightly mean spectrum itself? A few sharp dips in spectrum could be from standing waves?
- Check simulated S11 curves for dish/feed combo.
- Albert reminded us that nightly mean/correlated noise falls with distance as ~ 1/r1.15
- Reza's simulated NCP sky visibilities fall with distance as TBD
- Albert asks (again): could ground pickup be a significant source of the correlated noise? John P. showed that spill from 10o high hills is ~ 10 K using CST beam patterns. Structure in the hills could give visibilities that fall with baseline length. John M. suggests checking correlated noise for zenith-looking and NCP-looking telescopes. Peter recalls that the spill temp is a weak function of telescope elevation.
- John M. - can we devise an 'in the field' measurement of S11 and S21? John P has been thinking about this.
4:00 PM - ALFALFA analysis
- Albert suggests simulating visibilities as well making maps (with Sophya pipeline)
- Reza points out that observations there will have larger noise than those at higher dec. Because HI signal is known it's possible to do a different kind of x-correlation analysis than he and Olivier are doing in the low-z paper (PT: not sure I understand - theirs accounts for galaxy locations but not simulated HI amplitude?)
6:00 PM - Dinner at Rathskellar
- We could propose to build a 2-element interferometer based on John's P's design and see whether the 'correlated noise' is reduced
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