bs116b holography of the dish
jun 11 , 2003
Links to the plots:
az,za
offsets from 3C454.3 for the 6 patterns.
za
position and position sampling interval
the
phase vs time and zenith angle.
fit
to the phase at the peaks for the 7 patterns versus time.
Initial maps from aips: pat1Amp
pat1Deviations
pat2Amp
pat2Deviations
Sections:
Introdution
The scanning pattern.
Notes while taking the data.
The phase and amplitude for the
hancock,arecibo baseline.
Introdution
On 11jun03 (4am AST) we scanned 3C454.3 using
the vlba recorder and the cband receiver. The radar interface was run at
10 hz sampling of a 5 mhz band while the interim correlator was run with
a 25 Mhz band at 10 hz sampling. Two other vlba antennas were also used.
After 3C454.3 set the calibrator J2334+0736 was tracked for awhile.
The vlba correlator sampled at .13 seconds. There
were 7 patterns. Pattern number 4 has arecibo tracking the source the entire
time (since we passed through low za for this pattern).
The scanning pattern. (top)
The routine used the pattern corstarotf . The driving
routine was in src.11jun03. Each pattern consisted of
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39 strips through the source followed by 3 circles around the source center.
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Each strip was 25 arcminutes (great circle) long (+/-12.5 aminutes).
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The next strip started 180./39. degrees clockwise from the end of the previous
strip.
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Each strip took 18 secs with 5 secs to move to the start of the next strip.
(18+5)*39= 15 minutes for the strips.
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The circles started after the strips. They were at radii: 9.45,10.15,10.85
arcminutes and had a drive rate of 1.5 arcminute/sec. Before each circle
the telescope went on source for 3 seconds. Each circle took about 90 seconds.
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The pointing trajectory preprocessor was turned off for this experiment
(pnt pre 0). The telescope was commanded to the positions once a second.
It waited to be on position at the start of each pattern and at the on
source start of each circle. It did not wait to be at the start of each
strip. It just tried to do as well as it could.
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The pointing program had its fast dump mode enabled. It output the time(millisecs),
az, greg,ch positions in 1/10000 of a degree at about 25 hz. The data was
4 byte bigendian integers.
The first plots shows the az,za
offsets from 3C454.3 for the 6 patterns. The axis are great circle
offsets in az,za from the center of the source. Each plot has the positions
for the start of the pattern up to the positioning for the start of the
next pattern. The circles started at the right of each plot (3 hours on
a clock face).
The 2nd set of plots has the za
position and position sampling interval:
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Fig Top: za position vs utc hour. The start of each pattern is flagged
in red. The smooth line before each start was tracking on source. At the
end of the fifth pattern the horizontal line is where we stopped moving
to get off source and adjust the power levels.
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Fig Middle. This is the time interval between samples of the az,za encoders.
The mean value was 40 millisecs.
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Fig bottom: A blowup of the middle plot. At each 1 sec tick it took twice
as long to record the position since the computer was also busy collecting
other data.
x101/030611/doplot.pro
Notes while
taking the data. (top)
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tape took 22 minutes of data then turn around. We had 1 minute on source,
about 20 minutes of pattern, and then 1 minute on source.
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pat 1 start 08:47:40 [utc]. The 1st pattern started late. Interrupted before
the end to sync up with the vlba antennas for the next pattern.
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pat 2 start 09:10:20.
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pat 3 start 09:33:00. At end of pattern track 3C454.3 (on source)
while telescope transits (about 24 minutes). za was low enough that telescope
would not keep up in azimuth.
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pat 4 this pattern was not done. The telescope went through transit at
low za during this period. Arecibo stayed on source the entire time.
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pat 5 start 10:18:20.
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pat 6 start 10:41:00. At end of pattern, stopped moving to get off source
and adjust power levels. Was back on source at 11:01:50.
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pat 7 start 11:03:40.
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J2334+0736 got on source about 30 seconds late.
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File locations:
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corstarotf pattern:/home/online/Tcl/Proc/astro/cor/corstarotf.proc
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driving routine: /share/obs4/usr/x101/src/src.11jun03
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logfile for pattern: /share/obs4/usr/x101/src/log.11jun03
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az,za encoder log: /share/obs1/pnt/pos/dlogPos.11jun03 or /share/megs/phil/x101/030611/dlogPos.11jun03
The phase and
amplitude for the hancock,arecibo baseline. (top)
The first set of plots shows
the
phase vs time and zenith angle.
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Fig 1. top: The phase versus time at the amplitude peaks with no
phase corrections. The bottom plot has removed 2 pi jumps in the phase.
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Fig 2. top: The phase (at the peaks) vs za for each pattern in units
of degrees. The Bottom plot is in centimeters (360 degrees of phase is
6 cm).
The second set of plots shows the fit
to the phase at the peaks for the 7 patterns versus time.
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The top plot is the amplitude versus time for the patterns (excluding the
circles). The red horizontal line is the clippping level used to define
what points were at the source peak.
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The central plot is the phase at the peaks. Jumps of 2 pi radians have
been removed. The phase at the peaks wanders slowly by a few hundred
degrees. The red line is a high order polynomial fit to the phase.
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The bottom plot shows the phase residuals after the fit has been removed.
processing: x101/030611/vlba/dophcor.pro, phvstmza.pro
home_~phil