The model 17 fit with residuals (.ps) (.pdf)

Checking the model by removing a source at a time and recomputing the model (.ps) (.pdf)

The azimuth encoder table results (.ps) (.pdf)

Measuring the constant offset terms for the other receivers (.ps) (.pdf)

Variogram of the raw errors and pointing residuals (.ps) (.pdf)

verify model17 using sbn (.ps) (.pdf)

Data used to compute the model.

Fitting the model.

Checking the validity of the model.

Azimuth encoder table.

Measuring the constant offsets for the "other" receivers. (not yet done)

Variogram of the pointing residuals.

Background. (top)

- The extra lead in the corners of the platform were removed for
the painting project (about 20,000 lbs). We left this weight off the
platform and used the tiedowns to pull the platform back to a level
position. This gave us some more pretension in td 12 and td 4.

- 465 (and counting) points were used for the model.
- The model data was taken with model15B installed.
- The data was taken with heiles calibration scans.
- Data was taken 13dec07 thru 16dec07.

- A few evenings had some rain. I removed source patterns where the distomats were not working.
- Data was also taken during the day on 15dec and 16dec07. I removed some sources where the tiedowns had gone slack.
- There may still be some errors from loose tension.. The
distomats only read the height once every 2 minutes. When tension comes
back in may take a few minutes to get the platform back where it
belongs.

- On 16dec07 evening i installed the model for sband narrow and
started the verification.

- 5 sources were tracked with sbn using model17A. The pointing errors looked ok (.ps) (.pdf).
- The other receivers can retrack these sources and compute the
avg difference to get the az,za offsets.

- the other receivers are still using the old model15B since i haven't had a chance to measure their feed offsets.
- 18dec07 model17 for lbw and cband installed prior to verify
run. az,za offsets were computed to be the same as the the rcvrs had
with sbn on the previous model.

- NOTE: verify data was also taken with 430,327, and xband but the model 17 files were not installed so the data was taken with the old model (ignore the data).
- 12jan08. noticed that all recievers except sbn,lbw,cb were
still using the old model. Copied the new model 17 in and used
the same offsets as the receivers had with sbn in model 15.

- File locations. The online model files are in
/home/online/vw/etc/Pnt/

- enctbl17A is the encoder table for model 17.
- modelSB is current for model 17 (sband narrow). All other
modelXXX are the old model.

- subdirectory ./Dec07 has model17A for all the feeds. The az,za offsets (except for modelSB) were computed from the previous model15B:
- azZaOffRn= azZaOffRnMod15B - azZaOffSbnMod15B + azZaoffSbnMod17A.
- If the offsets haven't changed then this should be correct.
- To install one of these models, just copy it to the parent
directory: cp modelXB .. and then do a trkinit on this feed.

- subdirecotry ./Modelbkup has a copy of all the models for model15B (the previous model). If the new model doesn't work just copy the bkdup copy to etc/Pnt/.
- After xmas i hope to finish the other receivers.
- The code that reduced each days runs are in /share/megs/phil/x101/071213/domod.pro . and 1214,1215,1216
- The code to compute the model is in /share/megs/phil/x101/model/dec07/doall.pro

Data used to compute the model. (top)

- Fig. 1 is the azimuth/zenith angle coverage for the input data.
- Fig. 2 is the pointing error (za error top, az error bottom) plotted versus azimuth. This is relative to model 15. The left half of each plot is the northern portion of the dish (southern sources with declination < 18.2 degrees). The right half of each plot is the southern portion of the dish (northern sources).
- Figure 3 is the pointing error (za error top, az error bottom) versus zenith angle for the input data relative to the previous model. There is no linear ramp in za error vs az. It looks like there may be a slight ramp in az error vs za (i think we are missing a few compressors on the dome).
- Figure 4 is the za and azimuth errors plotted by source order. The sources are color coded.
- Fig. 5 is the magnitude and direction of these errors plotted versus azimuth and za. 1 tick mark is 5 arc seconds. At the bottom is a table of the average magnitude and rms for the entire dish and computed for every 5 degrees in za.
- Fig. 6 has the raw az, za errors plotted versus azimuth. The model 15 correction has been removed. Model 17 will be fit to this data set. Fits to 1az, 2az, and 3az have been over plotted with the amplitude and phase angle of the maximum.
- Fig. 7 shows the same raw errors plotted versus za. T

Fitting the model. (top)

za residuals | az residuals | total residuals [asecs] | |

mod17 noEncTable | 6.30 |
8.27 |
10.4 |

mod 17 with Enc Table | 4.39 |
2.99 |
5.31 |

- Fig. 1 plots the residuals versus za for the azimuth and za errors. The encoder table has not yet been removed. The computed encoder table is over plotted in red.
- Fig. 2 plots the azimuth and za (raw Errors - ( model + encoderTable) ) residuals versus za.
- Fig. 3 plots the azimuth and za (raw Errors - (model + encoder table) residuals versus azimuth. There is more scatter in the azimuth residuals that the za. The tilt sensor measurements show a 6az term over part of the dish. The encoder rack gear for the azimuth also has some runout. It will cause a azimuth scatter (with a za dependence since these are great circle errors).
- Fig. 4 plots the za and azimuth residual errors by source.
- Fig. 5 shows the za, az model residuals plotted versus source declination.
- Fig. 6 has the residual error plotted versus azimuth and zenith angle. 1 tick mark is 5 arc seconds. A table of the average error and the errors every 5 degrees za is at the bottom of the plot. Also included is the model parameters and values.

Checking the validity of the model. (top)

Fig 1 has the model residuals removing one source at a time. 0 is J1504+104, 1=J2123+055.. to 27=J0038+124. The black line is the total rms residuals while the red it the azimuth and the green is the zenith angle. The top plot does not include the encoder table while the bottom plot includes it. Removing the 11th source J1924+334 makes the largest improvement in the model. The previous model also had the largest error for the 33 deg Dec source. This source was taken in the afternoon so there may have been a problem with the tiedown tensions at the start..

Figure 2 plots the mean pointing error and its rms for each source track that was not included in the model. The model was evaluated without source i, then the mean and rms of the pointing model along the az,za track for source i was computed.

Azimuth encoder table. (top)

The table step has 1 degree steps in azimuth. Different az smoothing was tried. The az encoder table results (.ps) (.pdf) are shown in the figure: (the azimuth encoder table has not been installed).

- Fig 1 top is the azimuth encoder table made by smoothing to 1 through 6 degrees azimuth (bottom to top).
- Fig 1 bottom plots the azimuth encoder residuals (black line) for azimuth smoothing 1 through 19 degrees. The green line is the azimuth residuals without the azimuth encoder table. The red line is the total residuals (za plus az) for the various smoothing.
- Fig 2 over plots the azimuth residuals and the az enctable smoothed to 3 and 6 degrees azimuth.
- Fig3 is a fourier transform of the azimuth encoder table (built with 1 degree smoothing). The top plot is plotted versus cycles and the bottom plot versus period (in degrees). The power is at 4 cycles and 12 cycles (90 degree spacing and 30 degree spacing). (I think the az encoder rack gear has 15 degree sections...see az rack gear)

Measuring the constant offsets for the "other" receivers. (top)

On 16dec07 5 sources were tracked with sbn and the new model 17 installed. The sources were:

- J0141+138

- J0431+206 (135 mJy confusing src at 780" (3.7 Jy at lbw))
- J0659+082 (373 mJy confusing src at 617" (908 mJyAtlbw)) confused at low freq don't use
- B0949+287 ( clr for 900" around src)
- J1215+348 (129 mJy confusing src 717" (1.5Jy at
lbw)

Some of these sources were then retracked with the other receivers
to measure the receiver constant az,za values from the sbn model.
Before each receiver was used, an offset was included to get the
receiver
close to where it was supposed to be.

- 16dec07: sbn tracking
- 18dec07: lbw,cb tracking. two cb source offsets don't agree. One was J0659+082. May need to redo it with a different src.
- 18dec07:430, 19dec07 xb.. data taken with old model, ignore
- 21dec07: 430,327 taken with old model.. ignore
- 12jan08: xb only 10 patterns on J0141+138

- 16jan08: xb 4 patterns J0659+082
- 17jan08: 430 using B0949+287. Td 12 was not
working so ignore data.

The plots
show the tracking error for sbn and the other receivers. (.ps)
(.pdf).

The first 9 plots show the sbn error and the other receiver error
(one per page). Black is the sbn measurement. Red, green, blue, purple
are the up to 4 frequency bands of the "other" receiver. The left
column
has azimuth errors while the right column is za errors. The
numbers
printed are the mean(sbnErr) - mean(rcvrErr) in arcseconds. The figures
are:

- 327 Mhz. 3 frequency bands,

- 430 Mhz . 3 frequency bands ,
- 610 Mhz . 3 frequency bands,

- lbw. 4 frequencies, 2sources.
- sbw.

- sbh.

- cband. 4 frequencies, 2 sources. may want to redo one.

- cbandHi.

- xband. 4 frequencies, 1 partial source.
- Mean(sbn)-mean(rcv) for each source and frequency band. black is the azimuth error and red is the za error.

The offsets for the individual receivers as calculated from the above data is shown in the table below.

rcvr | azOffset asecs | za offsets asecs |

sbn | -34.07 |
-101.64 |

327 | ||

430 | ||

610 | ||

lbw | -35.16 |
-117.98 |

sbw | ||

sbh | ||

cb | ||

cbh | - | |

xb |

Variogram of the pointing residuals. (top)

This data can be used to interpolate the residuals onto an az,za grid (it gives the nugget (y intercept), range (where the variance increases), and the sill (value where the variance levels off) for the krigging routine)

- Fig. 1 is the variogram using the great circle angular separation of the points as the metric. The separation was binned to .3 degrees steps. The za correlation increases until za=2. degrees and then levels off. The az residuals variance increases till about 5 degrees. The 25 foot spacing of the north south main cables is about 1.6 degrees (1.5 degrees is close to the 25 foot spacing of the main cables ). The large correlation in the bottom plot is the 1az term of the raw pointing errors.

Fig. 2 projects the points into the xy plane and then measures the distance (since the kriging would be done in this plane). It looks the same as that of figure 1.

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