Intro:   

Steps to be taken

• test if the p50 laser scanner has the resolution to measure the dish
• done 11mar20
• purchase the p50 laser scanner
• delivery scheduled
• Setup the coordinate reference points for the p50 measurement
• Primary location for measurements is AO9.
• theodolite mount is in place
• Secondary measurement locations
• The hf dipoles shadow the measurements  from ao9.
• We can do measurements from the rim wall to cover the shadowed areas.
• We need to construct theodolite mounts on at least two locations around the rim wall (maybe 3)
• They can be built on top of the portion of the rim wall that sticks out toward the dish at the original main cable locations:
• eg:  Maybe cable E03 and cable W03.. (need to check the lines of site from these locations)
• We need to be able to survey the location of these mount points from A09 (so they can't be shadowed by an hf dipole)
• These should also be permanent/stable mounts so we can use them in the future.
• It would be good if we could also attach a prism to this mount to use as a reference frame for the rim wall (this attachment should give repeatable measurements when removing and then replacing the prisms (to  1mm).
  
• The distances will be up to 300 meters so we won't be able to use the 270meter mode of 11mar20.
  
• After the mounts are made we need some test data to see whether the 512 meter or 1 km mode should be used.
• When using the p50, the horizontal plane is defined by gravity and the leveling system of the p50. The azimuth location is determined by external targets.
• Here is a link to what the targets look like (.pdf) .. they should be as large as possible, and the white/black boundary should be at 45 deg to the vertical.
• For each p50 mount point we need a set of 3 targets spread around the edge of the rim wall that the p50 can use to determine it's azimuth.
• These should be permanent mountings and we need to be able survey then from ao9 (no hf shadowing).
• If possible these targets should be perpendicular to the line of site of the p50 (for maximum signal return).
• While placing the p50 mounts around the rim wall it might be nice to place about 6 prism mounts around the rim wall that can be seen from ao9.
• This would allow for rapid azimuth referencing of any theodolite measurements done from ao9.
• They could also be used to monitor the stability of the rim wall
• The mounts need to be visible from ao9 (no hf shadowing).
• Test measurements with p50 to check the targets
• from ao9 and the rim wall locations, scan the targets at high resolution.
• from ao9 measure  the locations of the targets. If possible also measure the locations of the 6 prisms around the rim wall to define our ref coord system
• verify that the p50 target locations and tm50 locations of the targets from ao9 agree.
• Actual measurements with the p50.
  
• These should be done at night after the temperature has stabilized.
• If possible we would like to do 2 or 3 passes  (the highest resolution scans may not permit this)
• Rain will cause the measurement to be abandoned (p50 shouldn't get too wet, the dish surface may change with the temp).
• From ao9 we can use the 270m mode. from the rim wall we need the 570 meter mode.
• Scan the targets before starting the scanning. Rescan the targets when done.
  

• resolution @10m	range meters	scan time for sensitivity		#scans	total time hours	location	notes
  		Normal (nr)	high (hr)
  0.8mm	270	01:48:12	03:36:21
  1.6mm	270	00:27:04	01:48:12	3	5.5 high	ao9
  3.6mm	270	00:06:47	00:26:59
  1.6mm	570	00:54:07	01:48:13	2
  3.1	>1km	00:26:49	00:53:57

• Trade offs
  
• repeat multiple scans from 1 location on  1 night
• will see how repeatable the measurements are for a given temp
• do 1 scan from each location on a night
• may allow a better tying of the rimwall with the ao9 measurements
• scheduling:
• Will probably need 3 nights say 7pm to 1 or 2 am.
• may need an hour or 2 of setup time before you start scanning.
  
• When  scheduling it might be best to do 1 night of 3 or 4 locations (shorter scans).. then look at the data and decide how best to proceed.
• if we are doing multiple continuous days, it would be interesting to do a single scan from ao9 during the day to compare with the nighttime measurements.
  
• Things to check:
• how much data can you store on the flash card before you need to unload it.. this may add some time.
• If we limit the scanning range in elevation:
• this will not fill the disc up as fast
• will it speed up the measurement?
• how low an angle can the p50 see from the rim wall.
• Processing the data:
• Fit sphere to each measuring location separately
• try to register all the points to one dataset and do one large fit (may be too much data for 1 fit ?)
• Decide on the radius of curvature we want for the dish.
• We need to know whether the platform can put the horn a the location for the standard radius of curvature.
• This requires a measurement of the secondary/horn) height vs az and za.
• Do this with the tm50 from ao9.
• Measure dome location from ao9.
• Place the 6 prisms around the mouth of the horn.
• measure the location of the dome vs za .. if possible every  degree in za.
• Repeat this as at least every 60 degrees in az.
• We want the distomats working for these measurements.
  
• We then need to measure the backside of the prisms from inside the dome relative to the secondary.. (see measuring the horns).
• Measuring the horns.
• Using the tm50  from the theodolite stand in the dome:
• measure the 50 reference targets on the secondary to define the location of the theodolite
• place the horn covers over the horns and measure the locations of the horns
• Adjust the horn locations and remeasure.
• do this for a number of horns (including cbw).
• also measure the locations of the backsides of the 6 prisms (that were used for the dome measurements).
• Software testing to do before measuring the secondary.
• from inside the rotary floor:
• open the window and mount the theodolite.
• Measure a few known targets on the secondary and then see if the program can move automatically to the rest of the targets.

Sequence

• For p50 measurements
• mount reference targets/prisms
  
• build  p50 mounts around rim wall
• mount p50 targets around rim wall
• mount  6 prisms around rim wall
• Take test data from ao9 with p50. check targets, and scanning of dish. can happen during daytime maintenance.
• survey p50 targets and prisms on rim wall from ao9 with tm50 (this could actually happen after the nighttime measurements if need be)
  
• Take p50 data at night from ao9 and rim wall (multiple nights)
• For tm50 measurements
• From ao9
• make sure 6 prisms are mounted around the rim wall
• measure the dome location at night from ao9 vs az and za
• From inside the dome
• finish the software testing of tm50 from inside the rotary floor room
• mount tm50 on theodolite stand in dome.
• measure 50 targets on secondary
• measure backsides of 6 prisms around the mouth of the dome
• measure the horn locations
• adjust the horn locations and remeasure.
• Analyzing the dome location data.
• figure how far off the horn location is from the design location (radius - 870 feet).
• decide how much this will change with temperature and az,za weight imbalance of the done
• Pick a radius of curvature for the primary that has a horn location that we can access over most temperature  az,za ranges.
• Decide of the main cable tiedowns can get to the curvature we selected.
  
• Figure out how the gain/beamshape changes for the radius of curvature/horn location that we've selected.
• Analyzing the p50 data
• figure out how to register the data from  the different locations.
• fit sphere to data using the radius of curvature that we decided on from the dome location data.
• Adjusting the dish
• adjust the main  cable tiedowns
• remeasure with the p50 from a09 and rim wall.. maybe we only need 1 scan from each location?
• check that the td locations moved by the amount we expected.
• iterate if necessary
• what is the range we have in the panel adjuster (probably depends on where they are currently set at).
• this may determine how many iterations of the td cables are needed.
• adjust the individual panels
• remeasure with the p50.