Left Front Bent Gregorian Focal Station Re-Commissioning Plan

Prerequisites

• Day time re-commissioning of AGW3. Able to position AGw on-axis, wfs apert. coincident w/rotator center (Jesper - done)
• AGw3 installed on telescope @ LFBG (done)
• LUCI installed on telescope @ LFBG (done)
• Update hotspot coordinates in GCS configuration files based on Jesper's realignment in July 2010 (Torsten - done).

Initial Pointing and Collimation of LFBG

Initial Pointing with LUCI

• Switch PCS to be Left-sided on TCSGUI.
• Determine initial pointing model zero points
  • Reset AZ and EL encoders
  • Start PCS pointing logging
  • Point to very bright source, e.g.:
    • Vega at 18 36 56.3364 +38 47 01.291
    • Pollux at 07 45 18.9503 +28 01 34.315
    • Regulus at 10 08 22.3107 +11 58 01.945
    • Arcturus at 14 15 39.6720 +19 10 56.677 (watch out for high proper motion)
    • Note: these 4 stars are now in the default catalog used by "pointto".
  • take an image with LUCI, or put LUCI into continuous readout mode
  • collimate (by eye) to correct focus and coma. [Andrew says move only M2 RX/RY for initial collimation.]
  • Offset dAZ = CA, dEL = IE to center star on detector
  • Repeat at low elevation to adjust IA
• Update the pointing model
  • Add zero point offsets to initial pointing model in /home/telescope/TCS/Configuration/PCS.
  • Load updated pointing model
  • Test that a preset now gets you to that star
  • Pointing errors should now be dominated by tube flexure (mostly elevation).

Build Initial Collimation Model with AGw3 (verify the existing model)

• Adjust initial collimation at high elevation
  • Point to an M5 star at high elevation (> 80 degrees)
  • Adjust collimation with M2 RX/RY as above
  • Adjust IE/CA again if needed.
• Establish initial (ON-AXIS) collimation lookup table
  • Point to bright stars at a range of elevations
  • MAT may be useful to help point, else use spiral search ptspiral
  • Adjust Zglobal to get an extrafocal image.
  • Send Z7/Z8 in arbitrator "primary" mode for manual collimation.
  • Implement initial collimation lookup table using CollimationModel instructions.

• What if M1 does not have the range to achieve collimation? (we are slightly close to the M1 Y limit at mid-elevations)
  • Offset both M1 and M2 as needed to being them back on range. See CollimationLimits although this procedure may require more optical insight than those instructions provide.

Initial Rotator Zeropoint with LUCI (open loop)

• PCS/MCSPU: Check Position Angle and Rotator Motion with LUCI
  • Old plan: point to clusters with known asterisms or double stars at several parallactic angles
  • New plan: It was hard to find asterisms, so we made the first cut by offsetting the telescope in known directions.
    • Preset in TRACK mode and center the star with IE/CA.
    • Offset the telescope and observe which way the star moves on LUCI.
    • Be certain that you are sending your offsets in RADEC space and not DETXY space.
  • take LUCI images/cubes at several position angles
  • verify sign (parity) and zeropoint of the position angle for LUCI
  • Adjust LEFTZEROPOINT in PCSInstrument.conf to refine the position angles

DJT notes that with LUCI, you can measure the position angle precisely. Use multiple astrometric fields. There needs to be a significant number (>20) of stars with good positions.

GCSL Functionality Tests

• GCSL (These are interwoven with AGw activities below so nothing to do here.)
  • acquire images (off-sky)
  • move stages (off-sky)
  • guide telescope
  • offset star onto wfs
  • acquire wfs images
  • process wfs images and send Zernike corrections for active optics

AGw Re-Commissioning for AGw3

AGw Guider Initial Calibration

Measure Rotator Center and establish the position of the optical axis

• Determine rotator center in AGw space
  • Start up the AGW unit
  • Move AGw to nominal on axis position
  • point to a cluster of stars
  • take two images 180deg rotation apart and determine rotcen
  • alternately (what we usually do), rotate the rotator while taking a 70 sec exposure on the guide camera
  • Reposition AGw stage to align with rotator center (Jesper)
  • Repeat as needed to position rotator center on WFS aperture
  • Note stage positions, we will need them again!

Measure Fixed Angular Offset

This was subsumed into the initial measurement of the transformation.

Guiding Tests

• Test closed loop guiding on-axis with GCS
  • Did the acquisition offset center the star in the guide box
  • Is the guiding stable to perturbations, or does the star drift off in the wrong direction?
• Sort out required parameter changes to make guiding stable.
• Repeat the test and Guide off-axis to verify rotator rates and flip parameters

AGw WFS Camera Initial Calibration

Warning: AGW2 WFS camera is upside down compared to AGW3 and AGW4. This is because of clearance issues for the new flexible cables.

Find Hotspot on Guider to put star in center of WFSC pinhole

• Send a GUIDE preset
• Acquire star on WFSC
  • Option A
    • Place star on nominal "Center of WFSC Pin Hole" position (guiding is doing this)
    • If no S-H spots, then stop guiding and move guide probe small amounts in spiral pattern until spots found
    • Move guide probe in +x,-x, and +y,-y till spots are vignetted
  • Option B
    • Stop guiding
    • Move telescope around with IE/CA to search for spots
  • Note guider (x,y) image position of "Center of WFSC Pin Hole" and guide probe position of "Center of WFSC Pin Hole". Adjust the configuration file as needed.

Initial Check of Active Optics Corrections

• Option A - GCS
  • Send preset to on-axis star in ACTIVE mode with sending corrections to PSF blocked
  • Calculate Zernike aberrations, send them manually with PSF starting with focus, then coma, then astigmatism, trefoil
  • Calibrate orientation of Z's, single mode, and adjust rotation of zernikes as needed.
• Option B - IDL
• Use Z9, Z10 to refine the Doug's angle offset
• Verify that both IDL and GCS agree on the angles and flips.

Initial Closing of Active Optics Loop

• Option A - GCS
  • Send preset to on-axis star in ACTIVE mode with sending corrections to PSF enabled
  • Calculate Zernike aberrations, send them manually with PSF starting with focus, then coma, then astigmatism, trefoil
• Option B - IDL
• Verify that both IDL and GCS agree on the convergence of the active wavefront solution.

Off-axis Active Optics

• Verify the pupil positioning for off-axis stars is going in the right direction.
  • First on the Y-axis
  • Then over the whole field
• Verify the range of pupil motion available on the WFS camera.
• Verify active optics convergence at extreme field positions
• Calculate Zernike aberrations, send them manually with PSF starting with focus, then coma, then astigmatism, trefoil
• Verify that both IDL and GCS agree on the angles and flips.
• Refine the pupil centering position. (Doug)

Focus the Guider relative to LUCI

This procedure needs good seeing. 0.6 arcsec or better in order to achieve sufficient precision.

• This is the fast procedure which does NOT run Active Optics while stepping the secondary mirror.
  • Preset in ACTIVE mode
  • Allow a few minutes for active optics to collimate.
  • Record the nominal focus offset and the present off-axis position.
  • Press StopWFS button on GCSGUI
  • Run a script to take a series of image cubes while offsetting focus. (for IRTC: cl < home$focus_seq.cl )
• Repeat the procedure several times until you've converged on a value for the focus offset.

• The slow procedure would make steps in the nominal probe focus offsets and run active optics at each step. This turns out to be vulnerable to changes in the seeing

over the tens of minutes that the procedure.

Check X-Y position of probe relative to focus position (postponed)

This procedure does not care so much about the seeing.

See BGTechProcedures for the procedure.

Initial Calibration of AGw coordinate transform

See document 481g221c "AGW Coordinate Transformations and their Calibration".

Preset to one of the Stone fields close to the meridian listed in StarCharts. Only these Stone fields with good astrometry and proper motions are useful.

Use the IRAF transtar script described in JohnSpecial. Doug should also have a new IDL command to test. Script needs some modification for using LUCI images. With LUCIFER, make sure flexure compensation is on!

Note: ImportantParameters in LBTtools for RFBG/LFBG

Be sure that you are taking IRTC data in H-band. If you want to use J-band, it will be necessary to change LEFTWAVELENGTH/RIGHTWAVELENGTH in the appropriate place in /home/telescope/TCS/Configuration/PCS/PCSInstruments.conf.

Please record the current value of LEFTZEROPOINT/RIGHTZEROPOINT.

Collecting Transform Data

The initial transform needs about 25 stars. Seeing should be no worse than 0.8 arcsec.

Detailed instructions appear in TransformationData .

Collect Data for Refinement of AGw coordinate transform

As above, but we want ~50 stars on a single field over a range of position angles.

Initial adjusting Field Aberrations with M2 collimation table

See the detailed setup in AOwithIDL, and see the more general description in FieldAberrationMeasurementDetails .

AGw On-Sky Commissioning

Calibrate WFS corrections

• • Take Intra/Extra-focal Image Pairs adjusting focus with M2
    • optimize size of the extrafocal pupils
    • take multi-extension image cubes for averaging the atmosphere (40 sec)
    • verify sign and rotation of EF corrections by applying known wavefront distortions to M1

Photometric Performance of Guider

Astrometric Performance of Guider

Flexure During Guiding

See section 6.5 of Jesper's AGW Commissioning Plan. Measure flexure as AGw rotates crossing meridian at several elevations. It probably isn't possible to measure the AGw flexure with LUCI imaging, as the flexure is dominated by LUCI internal flexure. Maybe there is a trick you can do with a slit mask to measure the flexure at the LUCI telescope focal plane.

Refining Field Aberrations with M1/M2 collimation table

This procedure needs good seeing.

Measure two deliberately induced offset vectors (4-6 hours)

Apply the corrections

Measure the final result (3 hours)

Check Field Aberrations at Two Elevations (6 hours)

Tertiary Mirror Tests

Verify angular offsets on sky

Need to think about which coordinate system to make these tests in. At minimum we should verify the expected scale of motion.

Further Improvements

Recheck Rotator Center on AGw

• (Optional, sanity check) Re-determine rotator center
  • Position AGw at the rotator center as above
  • point to a cluster of stars
  • take two images 180deg rotaton apart
  • Determine rotcen as mean of average coords of matched sources
  • Reposition AGw stage
  • Repeat as needed to position rotator center on WFS aperture
  • Note stage positions, we will need this again!

Improve Collimation Model

• Improve collimation model - precise instructions for the collimation model are found in CollimationModel (bullets below are only a summary).
  • Point to bright stars at a range of elevations
  • MAT may be useful to help point, else use spiral search ptspiral
  • Take Intra/Extra-focal Image Pairs adjusting focus with M2
    • optimize size of the extrafocal pupils
    • test multi-extension image cubes for averaging the atmosphere
    • verify sign and rotation of EF corrections by applying known wavefront distortions to M1
  • Collimate (using EF) [Move only M1 for initial collimation.]
  • Implement initial collimation lookup table using mkcoll.pro

Improve Pointing Model

• Improve pointing model - precise instructions for the pointing model are found in PointingModel (bullets below are only a summary).
  • Turn on mount pointing logging on PCS
  • Point to ~52 W&T pointing stars well-distributed across sky
  • spiral search to find if needed (hopefully not!)
  • position accurately on the WFS/rotcen
  • take an image, note time reasonably accurately (+/- 5s)
  • match source RA/DEC and mount pointing for tpoint
  • run tpoint
  • install improved pointing model
  • Hope that this gets us below ~5" rms (what we see at other focal stations)

Improve AGw Probe Transformation

As above......

Completion of the SX Hardpoint Checkout (partial)

See Engineering.NewHardpointCellCheckoutSX.

This document has a heritage in GregorianCommissioning which was used for LFBG and LDG, and Com201003AOPlan which was used for RFBG. JMH has rearranged the order of some activities to match practical reality.

-- JohnHill - 27 Aug 2010