PntErrors, sysperf after platform painting
The telescope was
shutdown 16feb16 to 21apr16 to finish the painting of the azimuth
arm. X102 calibration runs were run on 21apr16 (sbn) and
22apr16(lbw) to check the pointing and system performance after the
21apr16: sbn calibration run results
- data was taken 16:48 till 07:06 . 7 sources (not all full
- Page 1: az, za covered
- Page 2: gain,Tsys,sefd, average beam width
- gain: avg of about 9K/Jy
- Tsys: around 25K
- sefd: about 2.5Jy
- beamWidth: 120 asecs
- B0618+145,B0831+171 had large fluctuations in gain
and Tsys.. but the sefd was relatively stable
- There was lots of low level in band rfi (at 2380) during
the run (i could see it on the spectra).
- The cal measurement was probably affected by the rfi..
but the source and Tsys were ok.
- the sefd cancels the cal value... so it was stable.
- B1218+339: low gain,low tsys, low sefd, and large
- Not sure why this occurred. The source is no extended...
- Page 3: coma, sidelobe height, main beam efficiency
- Page 4: pointing errors:
- frame 1,2: za errors vs za, az
- frame 3,4: az errors vs za,az
- zaErr: mean: .27, rms 3.73 asecs
- azErr: mean: -1.4, rms 5.76 asecs
- these are reasonable values for the current state of the
- there are a few outliers (see page 5)
- Page 5, az,za errors, az,za position, and tiedown tensions
- I've flagged some of the pointing error outliers (to line
them up in the different plots)
- the outliers a little before 20 hours:
- these occurred on source B0331+171.
- The problem was probably rfi..
- The outlier at 26.7 hours...
- this was at transit for B1615+212. This was at transit..
za< 3deg.. The model is not very good at za=3 deg..
- Something happened between 25 and 26.6 hours.. no data was
taken (although the source was up).
- I didn't see any notes in the operator log. but it looks
like the telescope wasn't tracking ??
22apr16: lbw calibration run results
- data was taken 16:30 till 01:30. 6 sources (some only a few
- These were a subset of the sources taken with sbn on 21apr16.
since the observing time was shorter, not all sources were
- Frequencies used: 1155, 1310, 1375, 1415 MHz
- page 1: az , za coverage
- page 2: gain,tsys,sefd, beamwidth
- The gain and Tsys are higher than normal (see sysperf
by month, for last lbw data)
- The SEFD is normal. This says that the cal values are wrong
(since the sefd ration Tsys/gain cancels the cal value)
- The daily tsys measurements have also been high 38 ->
40k.. (for all the diode combinations).
- so we have a problem with the lbw cals.
- A larger tsys means the actual cal power has decreased..
- Since it occurs with all cal values, it may be a loose
- Felix has checked the cables from cal chassis to dewar
input and he said they were ok
- It could be a cable inside the postamp/cal chassis. If so,
it would need to be one of the cables common to all of the
cal switching combinations.
- We need to check the cables and then remeasure the cals
- There is no jumping around of the gain (like sbn).. no rfi
present in the bandwidth used.
- Page 3:
- coma, sidelobe height, eta main beam, eta mainbeam + 1st
- normal values.
- page 4: pointing errors:
- frame 1,2: za errors vs za,az
- frame 3,4: az errors vs za,az
- za Err: mean=-1.47, rms: 4.65 asecs
- az err: mean =-.9, rms: 4.09 asecs
- typical values for current state of the pointing model
- page 5: az,za errors, az,za position, and td tensions..
- I've put a blue dashed line at some of the pointing outliers
to line them up between frames.
- 19.8 hours: low za ..2deg..
- 20.5 hours: high za (> 19 deg)
- 23.5 hours: source rising, no tension in tiedown 8 (green
- pointing error:
- I left the outliers in the average.. removing them would
decrease the error (especially sbn with the rfi).
- constant birdie around 2390 MHz. we've seen this in the
hilltop monitoring system (more
- broad band lowerlevel rfi covering 2380 MHz
- The rfi came and went.. this rfi has previously seen.. it
has an az, za dependence.
- the cal output power has decreased since before the shutdown