# Measured horn positions

#### 08may04

The horns are surveyed into position using a theodolite. A cap with targets is placed over the mouth of the horn. This cap has 5 targets  mounted at known positions. The theodolite shoots the secondary to define the  reference dome centerline coordinate system. The turret is moved to the correct position for this feed and then the targets on the horn cap are shot. This gives the cap location in dome centerline coordinates. The horn position is then computed using the distance from the horn cap to the horn phase center.  (The positions are then converted to focus coordinate system where z is along the paraxial ray, y is toward the stairwell, and x is up the elevation rails.. 17apr18.. i think this sentence is incorrect.. i think things remain in dome centerline coordinates.). The table below shows the corrections that must be made to the horns to put them at the nominal positions (you move in the direction of the correction).
NOTES:
• When moving the turret, increasing the turret encoder angle moves a horn at focus towards the stairwell (+y).
• The Alfa receiver wants to be located -1.063 inches in x from the nominal position to balance the uphill and downhill horns. The values reported are relative to this position.

• KEY:

• Note: Lynn's memos show the error. The xxC are the corrections (or minus the errors).
• xxC  Translation correction. Distance to move in domeCenterline  coordinates to correct error.
• +X uphill,+Y toward stairwell, +Z up vertical (this used to say focus direction 19apr18).
• RxC Rotation correction(right handed). RYC + is clockwise around Y axis. RXC + is clockwise about +X axis.
•  ==> lynns' memos define Xtilt,Ytilt  error to be:
•  ==> xtilt err + when moving from the +x axis  in +z direction. This is a +err rotation about yaxis
•  ==> ytilt err + when moving from the +y axis in +z direction . This is a -err  rotation about the x axis.
•  ==> so the mapping from lynn's error Tilt definitions to my correction rotation definitions:
• RYC  = -xtiltErr
• RXC  = +yiltErr
• 23apr18 correction:
• i had been mapping +ytiltErr->- RxC  This was wrong. It should have been +RXC
• on 23apr18 i changed the sign of all of RXC entries so that values are consistent with the rotation definitions.

• <-- This marks the most recent survey for this receiver
• X + along azimuth arm. Y perpendicular to az arm + is toward the stairwell. Z is along the focus direction + makes the  focal length longer.
• nominal: this is the nominal position for the measurement in the focus (ray trace coordinates). If you subtract the correction from the nominal, you will get the current reading.

•
 Feed turDeg XC Inches YC Inches ZC Inches RYC Deg RXC Deg notes nominal raytrace -354.00 0. -234.0 1.74 0. Focus in ray trace coordinates nominal Dome Centerline -248.145 0. -389.822 .63 0 focus in dome center line coordinates. Note tht TYC of .63 is a positive (CW) rotation about the Y axis. See note about Lynn's "xtilt,ytilt definitions" LBN 28jan00 309.12 -.193 .104 .296 .099 -.7779 <--see #4. 21aug02 see #9 LBW 28jan00 285.5 -.124 -.922 -.048 -.225 -.9985 see #5. 11feb04 286.52 -.46 -1.36 1.00 .22 -.97 14feb04 285.42 -.47 -.03 1.00 .23 +.76 see  #12 28apr04 285.42 -.93 -.07 .94 02nov12 285.477 -.794 .126 .896 .390 -.738 <-- see survey notes ALFA 28apr04 26.27 -.42* 0 -.51 see #15 02may02 26.64 see survey notes. 02nov12 26.403 .741 .07 -.517 .353 .129 <-- see survey notes SBN 28jan00 76.6 -.003 .292 .112 -.069 .1328 28jan00 76.6 -.038 .253 .079 -.057 .1620 see #1 04feb02 76.83 -.021 -.257 .158 -.028 .0743 29mar02 76.88 -.013 -.132 .123 -.032 .1558 #8 11feb04 76.83 -.13 -.35 .02 -.07 .05 14feb04 76.56 -.07 -.05 -.11 .04 -.20 see # 12 28apr04 76.555 -.59 -.02 -.26 02may04 76.90 -0.59 -0.01 -0.20 08may04 76.94 .01 see survey notes 31oct12 79.6143 -.236 +.01 +1.173 -.45 .51 <-- see survey notes turret later moved to 79.967 SBTX 28jan00 62.25 -.143 .093 -.067 -.086 -.3677 see #6 11feb04 62.16 -.25 -.24 -.19 .00 -.31 14feb04 61.97 -.20 -.06 -.27 .01 .32 see # 12 28apr04 61.96 -.62 -.01 -.43 02may04 62.29 -0.66 -0.00 -0.38 <-- 08may04 62.29 -.02 see survey notes 31oct12 61.9441 -.518 +.181 +.122 1.2 -.2 <-- see survey notes SBW 28jan00 103.8 .447 .141 -.379 -.821 - .3547 see #7 11feb04 103.88 -.14 -.28 -2.54 .25 -.5 14feb04 103.66 -.09 -.07 -2.64 .17 .55 see # 12,#14 28apr04 103.66 -.58 .01 -.269 02may04 104.03 -0.24 0.01 -2.80 02nov12 103.673 -.152 .085 -.021 .536 -.479 <-- see survey notes SBH 29mar02 124.99 -0.027 1.068 .703 .284 .6941 see #8 11feb04 125.83 -.12 -.36 -.91 .23 .56 14feb04 125.55 -.08 -.05 -.12 .31 -.59 see  #12 ,#13 28apr04 125.55 -.53 0 -.23 02may04 125.94 -0.15 0.02 -0.08 02nov12 125.717 -.132 .076 .084 .279 .571 <-- see survey notes CB 28jan00 206.65 -.124 -.001 .010 .410 .1998 28jan00 206.65 -.165 .023 0.020 .396 .2013 repeated 28aug02 see #10 11feb04 206.65 -.17 -.34 -.11 .17 .42 14feb04 206.38 -.15 -.05 -.17 .32 -.43 see # 12 28apr04 206.38 -.66 .05 -.21 02may04 206.77 0.01 0.01 -0.29 02nov12 206.556 -.008 .039 -.214 .524 .489 <-- see survey notes CBH_1 11feb04 164.57 -.13 -.14 2.33 .27 -.96 14feb04 164.67 .23 0.00 .36 -.74 .34 28apr04 164.67 -.28 .01 .23 02may04 165.01 -0.22 0.00 0.05 <-- 08may04 165.03 .02 see survey notes 02nov12 164.711 -.428 .073 .159 .435 -.438 <-- see survey notes CBH_2 11feb04 158.45 .05 -.71 2.28 .27 .42 14feb04 158.01 .51 -.03 .34 -.69 -.86 02may04 158.38 <--see survey notes XB 04feb02 161.99 -.085 -.449 .441 .259 -.0412 see #2. 29mar02 162.39 -.066 -1.131 -.011 .097 .1208 see #3. 08jan04 309.94 see #11 11feb04 309.94 -.17 -.28 -.11 .1 .82 14feb04 309.72 -.15 .02 -.19 .22 -.90 see #12 28apr04 309.72 -.43 .07 -.15 02may04 310.06 -0.22 -0.00 -0.14 02nov12 309.800 -.185 .045 -.121 .385 .811 <-- see survey notes
1. The beam under the floor by the sbn receiver was removed to work on the seti IF box. This caused the floor to shift. The beam was replaced and then this receiver was remeasured. After the measurement, the turret position was moved to 76.83 deg.
2. After the measurement the horn was moved up .44 inches. The turret was moved 161.99 -> 162.34. This turned out to be the wrong turret direction to move. The next survey measured twice the error.
3. The large y error was because the turret was moved the wrong direction on 04feb02. After the measurement the turret was moved to 161.50.
4. After the measurement, the lbn turret position was moved to 310.14.
5. After the measurement the lbw turret position was changed to 286.52. This looks like it was the WRONG direction.
6. After the measurement, the sbtx turret position was moved to 62.16 deg. This was the WRONG direction
7. After the measurement the sbw turret position was moved to 103.8->103.88 degrees.
8. After the measurement (and getting the sign right!), the turret was moved, 124.99->125.827 degrees.
9. 21aug02 lbn horn moved down 3.84 inches to correct for phase center error.
10. 28aug02 cband horn moved down 1.08 inches to put phase center at focus.
11. jan04    receivers moved on floor to get ready for alfa installation.
12. 14feb04. The 11feb04 survey yCorrection was set to zero by moving the turret positions and then the 14feb04 survey was done.
13. 14feb04 sbhigh was moved down .91 inches before the survey to put the phase center at focus.
14. 14feb04 sbw was out of focus in z. It was not moved down because there was no more adjustment room on the mount. We need to make a new bracket.
15. Alfa x listed is measuredCorrection - 1.063 . Alfa wants to be 1.063 downhill from the nominal focus to balance the outer feeds.

#### Survey notes:

• 28apr04: after kevlar cables and alfa installed. The tilt values were small and were not reported.
• 02may04: Horn survey after horns moved (sbtx,sbrx,lbw,sbw(focus) were not moved). The corrections quoted are after the turret postions were updated. Previous surveys (11feb04 till 01may04) had been using an "old" secondary reference set for the secondary.  On 01may04 we switched back to the "new" set. This caused a motion of about .45 inches y (.37 turret degrees). The turret position for cbh_2, lbw,alfa  were also updated by .37 turret degrees because of the reference system change (even though they were not measured).
• 08may04:The turret encoder lost its position index on 06may04 (alfa cover broke encoder). I aligned the encoder tracking some lbw sources. Mike and Ellen then surveyed sbtx,sbn, and cbh_1. Using all of the measurements there was a -.027Deg  (before-after) difference in the turret encoder. This is .034 inches or -1.199 arcseconds on the sky. Since this is small we'll continue to use the turret positions computed by lynn. If you wanted to correct  for this, you would subtract .027 turret degrees from the offset i've put in the encoder offset of the little stars. The current offset in the little stars is 40843 enc counts. The correct value should be: (40843 - (.027TurDeg*477.867TurDegToEncCnts))=40830 encoder counts.
• 31oct12,02nov12 (see below)

## 31oct,02nov12 horn surveys (top)

A new sband narrow horn was installed on 28oct12. Lynn surveyed the sbn and sbtx horns on 31oct12. He surveyed the rest of the horns on 02nov12. An "old" (pre may04) secondary reference file  was used for the theodolite shooting. This data set was used for the sbn and sbtx analysis. Lynn did a comparison with the old and "newer" secondary references and saw little difference. All of the other receivers were analyzed using the newer secondary reference derived from the 28jun04 videogrammetry.
On 02may04 this "old" secondary reference was also used. At that time it was thought that there was a .45" y error between the two system (see 02may04 above).

• sbn
• New receiver. Had to move the floor  location since the new receiver was bumping up against the transmitter.
• turret position used for last measurement was79.6143.
• The errrors,corrections reported here are used the old secondary reference.
• in 02may04 this reference set was also used. later analysis showed a .45 inch y offset between old and new ref sets.
• after the survey was done, i moved the final sbn turret position to 79.967 deg (to correct for this .45 inch error).
• After taking into account the tilt errors, this may have not been the optimum solution.
• The sbn receiver was lifted in Z 1.2 inches on 26nov12 to correct for Z the measured z error. It was not resurveyed.
• sbtx:
• shot 3 times.
• final turret was 61.9441
• correction was  .181 inches or .181*.7973(turdeg/inch) = +.1418 deg.
• this would give 62.086 deg for turret
• there would also be a possible .45" correction for the old secondary ref set
• giving 62.44 tur deg pos
• I'm leaving the tx turret position unchanged: 62.29 turret deg.
• sbw,lbw,cb,xb,cbh,alfa,sbh
• All analysis done with latest 28jun04 videogrametry survey data.
• The turret positions remained as they were prior to the 02nov12 survey.
• I did not correct the turret position to minimize the y error..
Table showing the corrections needed from the nov12 surveys.
• These are taken from the large table above.
• The numbers are corrections. You need to move the feed by this amount. This is the negative of what lynn reports.
 rcvr turPos for measurement deg Xcor inches Ycor inches Zcor inches TYcor deg TZcor deg lbw 285.477 -.794 .126 .896 .390 .738 alfa 26.403 .741 .07 -.517 .353 -.129 sbn 79.6143 -.236 +.01 +1.173 -.45 -.51 sbtx 61.9441 -.518 +.181 +.122 1.2 .2 sbw 103.673 -.152 .085 -.021 .536 .479 sbh 125.717 -.132 .076 .084 .279 -.571 cb 206.556 -.008 .039 -.214 .524 -.489 cbh 164.711 -.428 .073 .159 .435 .438 xb 309.800 -.185 .045 -.121 .385 -.811

### Plotting the corrections for each receiver:

The plot shows the x,y,z errors (in dome centerline coordinates) from the survey (.ps) (.pdf):
• The data is in dome centerline coordinates.
• X positive up the azimuth arm
• Y perpendicular to azimuth.+ is towards the stairwell. This is the turret direction for small turret moves.
• Z focus. + is up.
• colors show the different errors:
• Black:X
• Red : Y
• solid line uses turret position of measurement
• dashed line uses current turret position (11jan13).
• Green: Z or focus.
• The data shows the amount to move the feed to correct for the error. (this is the negative of lynn's reported errors).
• Top: The Correction need in inches
• Bottom: The correction needed in lambdas (using the lambda for the center of the feed).

### Lynn's emails and reports:

processing: /share/megs/survey/121102/hornsurvey.pro, /share/megs/survey/121031/xxx

# Horn phase centers.

Many of our horns are kildall horns. A paper written by per simon kildall was used to calculate the phase center of the horns and position them. They computed the phase center for a horn that covered 9 to 17 Ghz. For this horn the phase center was z= 7 +/- 1.7 mm (see paper for definition of z=0 .. end of waveguide in horn).  The phase center should scale with with the throatdiameter of the horn.

For 13 Ghz (assuming diameter = lambda) the focus is z= .31*throatDiameter. This was then used to position our kildall horns in the focus direction.

Focus curves were done (by moving the platform up and down) to try and find the optimum platform height. After doing this, all of the kildall horns needed  a platform height  that was lambda/2  higher than the none kildall horns (more info)

German cortes modeled the lbw kildall horn, and found that the phase center was about  z=-3.05 cm inside the waveguide. After more research, i think it turned out that there was a sign error in the original kildall paper. The kildall horns were repositioned (scaling  the lbw position by the throat diameter).

 horn throatDiameter z focus from horn throat lbw 20.254 cm (7.975") -3.0401 cm sbw 12.253 cm (4.824") -1.845 cm sbh 7.945 cm (3.128") -1.197 cm cband 5.969 cm (2.350") -0.899 cm

note: lbw was switched from a kildall horn to a cortes horn design on feb2003

When surveying, we measure the locations of targets sitting on a plate connected to the mouth of the horn. You then need to translate these numbers up the z axis to the focus position. To do this we need to know :
• the target height above the plate (1")
• the plate thickness
• the distance from top of horn (where plate connects to the throat of the horn (z=0)
• the distance from throat of horn to horn focus.

The table below tries to summarize this info

 horn type throat Diameter zFocus from horn throat hornThroat to horn end survey plate thickness targetTo focus lbw 1.115-1.760Ghz kildall cortes after feb03 20.254 cm (7.975") -3.0401 cm 2.813 cm sbn lynn? sbtx lynn? sbw 1.7-3 GHz kildall 12.253 cm (4.824") -1.845 cm 1.702 cm .665 cm (.262") sbh 3-4GHz kildall 7.945 cm (3.128") -1.197 cm 1.103 cm .665 cm (.262") cband 4-6GHz kildall 5.969 cm (2.350") -0.899 cm 0.829 cm .665 cm (.262") cbandWide 4-8GHz cortes xband 8-10GHz lynn

Notes:

• throatDiameter
• kildall horns.. may have scaled it from lbw
• zfocus
• kildall horns:
• used germans hfss modeling of lbw and then scaled by throat diameter for other kildall horns
• survey plate thickness
• measured.

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