search

HERA-Team / hera_cal

Library for HERA data reduction, including redundant calibration, absolute calibration, and LST-binning.
MIT License
11 stars 8 forks source link

remove firstcal tip-tilt degeneracy #113

Closed nkern closed 6 years ago

nkern commented 7 years ago

firstcal seems to be inserting a tip-tilt solution into raw data. we need a remove-degen function to take it out before passing firstcal solutions to omnical.

dannyjacobs commented 7 years ago

wait, you sure we didn't do this already?

On Mon, Oct 23, 2017 at 10:20 PM, Nicholas Kern notifications@github.com wrote:

firstcal seems to be inserting a tip-tilt degeneracy into raw data. we need a remove-degen function to take it out before passing firstcal solutions to omnical.

— You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub https://github.com/HERA-Team/hera_cal/issues/113, or mute the thread https://github.com/notifications/unsubscribe-auth/AAD21yPQAS289FaU2GF0-LyJntx8asqiks5svREfgaJpZM4QDk7j .

--

Daniel C. Jacobs KE7DHQ Assistant Professor Arizona State University School of Earth and Space Exploration Low Frequency Cosmology Phone: (505) 500 4521 Homepage: danielcjacobs.com MWA: mwatelescope.org HERA: reionization.org PAPER: eor.berkeley.edu

jsdillon commented 7 years ago

Yeah, it turns out we fix the overall average delay to be zero (need to double check that), but we don't fix the tip and tilt in delays (which are also degeneracies of firstcal). Omnical keeps whatever firstcal put in, so this explains a fair bit of why the omnical solutions cause images to wander around.

plaplant commented 7 years ago

Naive question: is this more complicated than running the existing remove-degen on the firstcal results?

nkern commented 6 years ago

5/15/2018 update: we didn't write a firstcal remove-degen. we did write an abscal module to correct for any degeneracy firstcal puts in and correctly phase the data