2017 January

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Jan 03

15:00 UT Rebooted ROACHes due to bad communication with Roach 1.

21:00 UT New delay center corrections derived from the 2016 Dec 22 calibrator survey observation (using 2136+006) were sent to acc. The values for Ant 1-14 are: [0., 0., 0., -1.27, 0., 1.48, 4.26, 0., 1.5, 0., -10.24, 0., 0.] in nanoseconds

Jan 04

01:16 UT We were not getting good phases on calibrators, and discovered that my reboot of the ROACHes this morning left them with incorrect equalizer coefficients. This has been corrected as of 0100 UT.

01:50 UT Updated delay centers again, based on data taken today (01:01 UT).

02:14 UT Delays look good! Now going to 3C84--first scan starts 02:11 UT, on source at 02:15 UT. 3 bands

23:59 UT Start of a really useful scan (filename IDB20170104235937), which is on a satellite (AMC-11) that broadcasts linear polarization at C band. The observation used a special band6 science channel definition, so that science channels are 5 MHz apart, and during the observation the Ant14 feed rotator was swept from -80 to 80 degrees. The data show very nice nulls at the lowest few frequencies that should indicate when the relevant polarization product has perpendicular feeds.

Jan 05

14:02 We are observing 3C273, but this morning I found Ant 14 was not tracking. I got it on source around 14:03 UT. We lost about 4+ hours, unfortunately.

Jan 06

00:00 We had to restart the Roaches for the 300 MHz clock test. We made another observation on 2136+006 to derive the new delays, which were put in. We also derived a set of YY-XX delays and updated to the ACC. The YY-XX delays we put in (relative to Ant 1) were [0.0, -0.09, -2.18, -2.12, -3.57, -1.96, 0., -0.22, -0.63, -5.24, -0.51, 0.23, -3.40, -1.62] in nanoseconds, derived from the Jan 4 3C84 data.

00:20 It appears that after correcting for the differential YY-XX delays and rotating the visibility about the differential parallactic angle (w.r.t. ant 14), the amplitudes of the 2017 Jan 4 observation on 3C84 get corrected! Now we need to see if updating the YY-XX delays to the system would be the fix.

Fig. 1:Amp vs. hour angle of the Jan 4 observations on 3C84 on all antennas (column) and polarizations (row; showing XX, XY, YX, and YY). Blue is the original and red is the corrected