Pointing errors oct,nov10

• These change were not installed in the pointing model
• On  14oct10 the td12 encoder was changed. This could have generated a 1az error term.
  

• Page 1: az,za coverage of data
• top: all the data
• middle sbn  coverage
• bottom: cband
• The telescope was limited to za<16 deg za for this data.
• Page 2: pointing errors, sband,cband over plotted
• black is sband, red is cband
• 1,2: za error vs za,az
• 3,4: az error vs za,az
• You can see the 1az term in the za and az errors vs az.
• errors:
• za:mean:1.7   rms:4.26
• az:mean:-.89  rms:6.15
  
• Page 3: pointing errors  sbn by source
• Same as page 2 but limited to sbn. Plotted by source
• errors:
• za:mean:1.39   rms:4.86
• az:mean:1.33  rms:5.83
• Page 4: pointing errors cband by source
• errors:
• za:mean:1.86   rms:3.90
• az:mean:-2.08  rms:5.99
• Page 5: 1,2,3 az fits to errors (all the data)
• top: za errors vs as with fit (red)
• 2nd: az errors vs az with fit (red)
• 3rd: az (black), za(green) residuals from fit vs az.
• 3th: az(black), za(green) residuals from fit vs za
  
• Page 5: pointing errors all data vs za with fit removed (by source)
  
• 1,2: za errors vs za,az
• 3,4: az errors vs za,az

•  y=C0 + C1*sin(az - C2) + C3*sin(2*az-C4) + C5*sin(3*az-C6).

• Values to SUBTRACT from current model

  Model Term	az Err Asecs	za Err Asecs
  constant	0.649	0.911
  cos(az)	-1.377	6.055
  sin(az)	-5.440	-0.076
  cos(2az)	0.349	0.967
  sin(2az)	0.172	-0.135
  cos(3az)	2.263	-0.075
  sin(3az)	-0.048	-0.248

  
  

Summary:

• The pointing errors after the U2-U2L3 beam repair were
• az: mean:-.89  , rms:6.15 asecs
• za: mean: 1.70, rms:4.26 asecs
• Fitting 1,2,3 az terms showed that the largest error was a 1az term which is a platform tilt.
• On 14oct10 the tiedown 12 encoder was changed.
• If the new encoder was not replaced with exactly the same value as the old setting, then this could have caused a platform tilt.
• This tilt should have had a phase near 180,270 (az,za) which is pretty close to what was measured.
  
• The individual sbn,cband errors differed probably because they didn't sample a complete 1az cycle.
• The errors after fitting for 1,2,3 az were:
• az: rms: 3.47 asecs
• za: rms: 2.68
• This is probably better then expected since we did not have a complete az,za coverage.
• The pointing model was not corrected for these errors.
• The u3-l4 reinforcement will probably change these values.
• If the error was from the td12 encoder replacement then we probably should install the changes.
  

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