Data for model3A was taken feb,mar16 (more info
1D gaussian fits to the az and elevation strips were used to
compute the system performance. Data with poor fits (large
pointing errors, were excluded).
The gaussian fit used for each strip was:
- y=A0 +A1*exp(-(*x-A2)/A3)^2) + a4*x
- x is the great circle offset from the center of each
- I used 8 sources. We had fluxed for 6 of them.
- the data was taken over 2 weeks.
- There was no cal available
- The data from each rise,set of a source was normalized
to have a median value of 1. So the units of each data set
should be close to tsys
- The electronic gain was necessarily the same for each
source data sets (although the src and Tsys measurement
for a single cross will have the same units..).
The plots show the
results from the fits (.ps)
- Page 1: Tsys and src strength
- This plots all of the data taken
- black has the azimuth strips, red has the elevation
- Top: Fit to Tsys vs cross sample number.
- the units are normalized to 1 for each data set (so
all the data does not have the same electronic gain).
- 2nd: Fit to source strength vs cross sample number.
- The strongest source (Cas A) was about .25 to .3 of
- Bottom: srcFit/Tsysfit
- this is source strength in units of Tsys (but the flux
has not been included yet).
- Tsys can change because of the elevation, or the
- Page 2: Compare data from az and el strips.
- Top: ( fit TsysAzstrip)/( fit TsysElStrip).
- The variation is a fraction of 1%
- bottom: Ratio of (azFit srcStrength)/ (elFit
- The noisy ratios are the source with smaller
flux (< 1% of Tsys).
- Page 3: Tsy Fits vs elevation. plotting each source
- Try to see if there are any strange variations in gain
- Top: the 3 strong sources
- green: 3C461.. one of the strips looks like it had a
strong tsys or gain variation (rain?)
- Bottom: the 5 weaker sources
- black 3C123 had a large gain or tsys variation around
- Each source is plotted in a different color
- Page 4: TSource/Tsys vs elevation by source
- Top: 3 strong sources
- bottom: 5 weaker sources
- The large change in 3C461 remained with the ratio. So
the change was probably a Tsys change.
- 3C123 had no jump around el=60.. so the Tsys jump was
probably an electronic gain jump (it cancels in the
- Page 5,6 : SEFD vs elevation by source
- Each source is plotted in a separate frame.
- I corrected the source strength by the pointing error
(although it was < 1%)
- No correction was done for the source being extended..
- The beam is 40 Amin, the largest sources were about
- Black is from the az strip, red if from the elevation
- There doesn't seem to be a very large difference
between the two.
- The median value for the az and el strips are also
printed on the frame.
- The fluxes were taken from:
- baars et al.
- I corrected 3C461 from the 1980 fits to 2016 using:
- (.97 -.3*log(freqGhz)) % change per year
- Looks like the correction was a little to much.. the
sefd came a little lower than the others
- Pictor_A flux comes from the 2nd attempt pictor_a fits
by chris salter.
- The sefd was computed using the 1d fits to the az,el
strips taken when making model 3A.
- The median sefds are:
|1% of Tsys
|+40Dec Cygnus A
||-45Dec. chris salters 2nd fit
|+58Dec Cas A (variable,extended)
looks like time correction overdid it...
- Using the 1st 5 sources, the sefd is 4434Jy. The
measured rms is 7%.
- There is a 20% Tsys variation with el for sband.. (more info)