Platform tilt model for 2018

• az,za points used for the model (.ps) (.pdf)
• these are the az,za locations of the data.
• The platform translations vs azimuth (.ps) (.pdf)
• All of the data is plotted vs azimuth.
  
• black points are translations in x direction (+ is west)
• red points are translations in y direction (+ is north)
• The platform will translate horizontally when the dome moves in za.
• when pointing at a tower and the corner goes down, the tension in that main cable increases
• This increases the horizontal force toward the tower.
  
• platform rotations vs azimuth (.ps) (.pdf)
• black points are rotations about X (west)
• red points are rotations about Y (north)
• platform translations by az and za with fits for each za range  (.pdf)
• data is separated into 1 degree strips 1 to 20 deg
• Each frame is  x,y translations vs az for the data in the 1 degree strip
• Black is  x translations (west)
• red is y translations (east)
• the green lines are the locations of the towers.
  
• The blue lines are  azimuth fits to the data
• There are two data sets.
• on 29jun18 distomat 5 was replaced. this caused a jump in the distances..
  
• 01jan18 to 29jun18
• 30jun18 to 31aug18
• the fit is y=offset + amp1*sin(az-phase1) + amp2*sin(2az-phase2)
  
• Page 1:za 1 to 5 degrees
• page 2: za 5 to 9 degrees
• Page 3: za 9 to 13 degrees
• Page 4: za 13 to 17 degrees
• Page 5: az 17 to 20 degrees
• platform rotations by az and za with fits for each za range (.pdf)
• each frame is a 1 degree za range. 1 to 20 degrees
• black is rotations about x (west)
• red is rotations about y (north)
• The green lines are the locations of the towers
• the blue lines are 1 azimuth fits to the data.
• There are two data sets.
• on 29jun18 distomat 5 was replaced. this caused a jump in the distances..
  
• 01jan18 to 29jun18
• 30jun18 to 31aug18
• the fit is y=offset + amp1*sin(az-phase1) + amp2*sin(2az-phase2)
  
• With the ch at stow (8.88) the azimuth arm is  balanced with the dome around za=8 degrees. You can see the amplitude of the 1az term go to zero.
  

• stability of the laser ranger data (.ps) (.pdf)
• the top frame plots the x,y translations for za=8-9 degrees vs day of year
• the bottom frame plots the x,y rotations for za=8-9 deg vs day of year
• at 8 degrees, the platform is close to balanced.
• there is jump in the translations and rotations on 29jun18.
  
• distomat 5 was replaced on this day.
• The distances measured by the old and new distomat 5 are not the same..
  
• plotting the rotation fit parameters vs az for 1 deg za steps (.ps) (.pdf)
• The fit was: tilt Angle= offset + amp1*sin(az - phase1) + amp2*sin(2az -phase2)
• The data before and after 29jun18 were fit separately
• colors show different epochs and axis
  
•  

  axis	pre29Jun	post29jun
  x (west)	black	green
  y (north)	red	blue

  
  
•  
  
• top frame: fit offset
• 2nd frame: amplitude for 1az
• 3rd frame: phase for 1az
• after za=8 the phase flips by 180 degrees. The tilt is going from neg to positive.
  
• 4th frame: amplitude for 2az
• bottom frame: phase for 2az fit
• The data for the two epochs differ in the fit offset.
• The largest difference is the offset about the x (west) axis)
• dist 5 measures the north reflector on the corner pointing at T8.
• I think a negative change says the post 29jun measurements are shorter than the pre ones.
  

2018 Summary

• This model can now be used to compute the pointing error when we lose tension in a tiedown (if you have a distomat reading).
• There are separate fits for pre,post 29jun18.
• The program pnterrrot  will use these fits to compute the pointing error caused by the platform being out of position.
• My gut feeling is that the measured values won't be more accurate than maybe 10asecs.