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 UT 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 UT 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

10:50 UT Looks like the wind has died down a bit, so I have started a 3C273 observations (3 bands). Ant 14 Dec drive had a permit error, but I cleared it, so Ant 14 is tracking at 10:56 UT. Ant 2 was "sticky" too, and required two power-cycles to clear, but on source at 11:00 UT.

17:20 UT We discovered that the YY-XX delays put in at 00 UT were mistaken. We reversed these values, added the correct values and sent to ACC. The correct YY-XX delay values based on the Jan 4 3C84 observation should be [-1.62, -1.53, 0.56, 0.50, 1.95, 0.34, 0., -1.40, -0.99, 3.62, -1.11, -1.85, 1.78, 0.05] in nanoseconds. A new observation is taken on 3C286 starting at ~17:20 UT. Observing AMC-11 at band6 at 17:43 to check the result of the polarization (amplitude) rotation.

19:04 UT We also discovered that X and Y delays were being set independently, which made them step at different times. They need to change simultaneously. This was corrected, and new data on 2136+006 started at 19:04 UT.

19:25 UT I put in the Dec. 22 Bz corrections in, and have started a new scan on 2136+006 at 19:22 UT.

22:45 UT Bx and By corrections derived from the Jan 6 3c273 data were put in. New scans on 2136+006 and 2253+161 started at ~22:45 UT.

Jan 07

00:25 UT Now we are starting 3C84 for an all-night run, to check and possibly refine baselines and delays.

16:00 UT Now on the Sun--hoping to get a good all-day observation for an image. Did not work well, however, due to snow and sleet all day.

Jan 09

01:05 UT Observations on 3C84 started at 00:20 UT with 6 bands, but just now I stopped the observing and set the equalizer settings to 4 (from 32). New data started at 01:04 UT. I also grabbed some packets to do a proper evaluation, and may update the equalizers further shortly.

02:08 UT The 3C84 phase coherence seems less than last night, so we are setting the coefficients back to 32 as a test. Also took 3 dB out of Ant 14 H and V pol in front end.

02:49 UT The result of the test was not very conclusive. I have compromised by setting the coefficients all to 8, and have gone back to 3 bands on 3C84. I will let it run in that mode for the remainder of the evening.

Jan 15

13:12 UT Quick observation with high receiver on 3C273 (3bands.fsq), to check delay centers. I assume that delays should be good, and then I will go to Ciel-2 and see what delays are indicated (I presume they will be substantial, due to the satellite position being different than calculated from the TLE data). Hmm. I did not go to Ciel-2, but I did take data with ND-ON, and found that the X-Y delays are still nicely zeroed. On 3C273, the XX delays are small, but the YY delays are 1, 2, or even 3 steps off (the bad one is Ant 8). This clearly does not agree with the ND-ON measurement.

15:10 UT I decided to take some data on 3C273 with the low-frequency receiver on the 27-m. I created a sequence 3bands_lo.fsq, which tunes to bands 5, 7, 9. These three bands are in the range of both LO and HI receivers. The scan started around 15:09 UT. I set the focus of the low-frequency receiver to 50. I will also take some data on the high-frequency receiver with the same bands, as a head-to-head comparison.

15:28 UT Switched to HI receiver starting 15:27:00 UT, reached position at 15:28:15 UT. Did not stop recording. The comparison between receivers is very good. The phase fluctuations appear to be similar between receivers. Ant 13 is over-noisy, probably because it needs stowing to reset its zero position. I did that at 15:44 UT, back on source at 15:45 UT.

Jan 17

00:40 UT Running a long 3C84 run with pcal.fsq, for possible calibration of the solar data of the past few days.

Jan 26

02:10 UT Started observing 3C84, to redetermine delays after reboot of ROACH boards due to power outage earlier this week.

08:20 UT Started a long 3C273 observation with pcal.fsq (scheduled, but not monitored).

12:55 UT Discovered that Ant 14 was not tracking, with PERMIT fault on Dec axis. Data before now is probably no good. I rebooted and resumed, but the antenna had another fault before reaching the source. Another reboot, and it is tracking now. Ambient temp is only 16 F. Barring another fault, good data should be between 12:55 - 15:40 UT.

13:20 UT Updated delays according to Bin's analysis of 02:10 UT 3C84 data. New delays take effect in scan starting at 13:20 UT. I used the sign of Bin's delays directly. (Analyzed results confirm that most changes are good. Some antennas may still be problematic).

Jan 27

04:28 UT I am doing a long series of interferometric pointing measurements, using the high-frequency receiver on band 14. One scan was missed up to now due to bad Ant 14 tracking (Dec PERMIT).

11:40 UT I found Ant 14 with a Dec PERMIT condition when I looked this morning. I got it tracking just as a WINDSCRAM occurred. I do not know when the observations were interrupted, or how many pointings were successful overnight. (I checked later, and the error seems to have occurred around 11:17 UT, midway into the 11:02 UT scan. We have 21 good scans.)

13:20 UT I gave up on the pointing observations, since the wind is now steady at 20 mph. There will be some good observations up to whenever the Dec PERMIT error occurred. I will likely have to try again tonight after the Sun sets. NB: Bin reports a first "burst" image from a small B8 flare that occurred on Jan 25!

Jan 28

04:37 UT I am rerunning the pointing observations. So far they have gone without interruption from 00:45 UT. The wind is low, so barring an Ant14 Dec problem, the observations should go well.

12:06 UT When I checked this morning, Ant 14 was found to have an HA cable tension alarm. That is bad news--we will not be able to continue any measurements with it until it is fixed, which means Monday at the earliest. It is currently at a large HA angle (-51). Looks like it died at 05:43 UT.