Left Direct Gregorian Focal Station Re-Commissioning with MODS1 Plan

Prerequisites

  • MODS1 installed on telescope @ LDG (done)
  • Update hotspot coordinates in GCS configuration files based on lab measurements

Initial Pointing and Collimation of LDG

Initial Pointing with MODS1 DONE

  • Switch PCS to be Left-sided on TCSGUI. DONE
  • Determine initial pointing model zero points DONE
    • 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 DONE
    • 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 AGw5 (MODS1 AGw) DONE

  • 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 MODS (open loop) DONE

Note: Since MODS is a dual-channel instrument this alignment needs to be done relative to a long slit mask rather than relative to detector pixel columns. Note that the two MODS cameras have slighly different pixel scales, centering relative to the ISS Center-of-Rotation, and rotation relative to the slit.

  • PCS/MCSPU: Check Position Angle and Rotator Motion with MODS
    • 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 MODS.
      • Be certain that you are sending your offsets in RADEC space and not DETXY space.
    • take MODS images/cubes at several position angles
    • verify sign (parity) and zeropoint of the position angle for MODS
    • Adjust LEFTZEROPOINT in PCSInstrument.conf to refine the position angles

Update: 2010 Sept 25 The initial estimate of the MODS rotator angle for alignment, 210-degrees instead of 180-degrees because of the need to clear obstructions between the rotator drive motors and the MODS envelope proved to be sufficient to adopt without needing to follow the measurement procedure described above. Also our initial assessment of the PCS to MODS AGw coordinate space are close enough to do this by adoption rather than measurement to establish the starting point of the refined calibration.

GCSL Functionality Tests needs DONE

  • 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

Note that the WFS functions of the GCS are currently not able to handle the MODS1 WFS camera S-H images because of a combination of rotation and coordinate transposition. For the Sept commissioning run we are using the IDL routines for WFS image analysis and correction to accomplish these tasks. Details are in the commissioning wiki pages for MODS - (rwp/jh - 2010 Sept 27)

AGw Commissioning for AGw5

AGw Guider Initial Calibration

Measure Rotator Center and establish the position of the optical axis DONE

  • Determine rotator center in AGw space
    • Start up the AGW unit
    • Move AGw to nominal on axis position
    • point a star and acquire an image in track mode.
    • Slew the rotator 0 to 360-deg while exposing on the star for 70 sec
    • In the images, the smeared star looks like a ring, measure the center of the ring to determine the center-of-rotation
    • Check alignment of the guide camera relative to the rotation center, adjust the stage "field-zero" mechanism position values as required.
    • Note stage positions, we will need them again!

Measure Fixed Angular Offset

This was subsumed into the initial measurement of the transformation.

Guiding Tests DONE

  • 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.

2010 Sept 27: a combination of rotation and tranposition is involved in the WFS calibration, see the Commissioning wiki for the gory details...

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

  • 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.

Focus the Guider relative to MODS

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

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 the Stone-O field (21 48 03.9798 +00 00 13.540). Four PAs are available: 0, +90, -90, 180 deg.
It crosses the meridian at El ~ +58 deg. at Eve Twilight in November
The catalog is in MODS's PC and it's also on the mountain at: /home/mpedani/MODS-CATALOGS/Astrometric-Catalog-Sept10.cat
Additionally, the Stone-A is available (00 55 09.500 +00 03 27.0)
It crosses the meridian at ~03:45 UT in November.
Two Orion astrometric fields (Plate107 and 111) (05 35 00 -05 31 ) catalogs/finding charts are also available.
They cross the meridian at ~08:30 UT in November.

Use the IRAF transtar script described in JohnSpecial. Doug should also have a new IDL command to test. Script needs some modification for using MODS images.

Issue: Will MODS need a neutral density or narrow band filter for the astrometric fields?

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.
As above, slew to the Stone-O field (21 48 03.9798 +00 00 13.540). Four PAs are available: 0, +90, -90, 180 deg.
It crosses the meridian at El ~ +58 deg. at 5:00 UT.
We have 57 data points when we take all the stars at the Four different PAs.

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

  • Slew to IC1613A and IC1613B fields (RA: 01 04 59.986 Dec. +02 06 57.83). A total of 38 stars are observable in these two fields with complete BVRI data.
  • It crosses the meridian at El ~ +60 deg. at 3:45 UT in november.
  • Marco prepared the catalogs and finding charts. They are in MODS and in: /home/mpedani/MODS-CATALOGS/Photometric-Catalog-Sept10.cat

Astrometric Performance of Guider

  • Slew to Orion_Plate111 field (RA:05 35 15.20, Dec -05 20 15.0). A total of 20 stars with precise proper motions are visible within the 50"x50" F.o.V.
  • It reaches El ~ +48 Deg. only at ~08:30 UT in november.
  • Marco prepared the catalog but no finding chart (inside the M42 nebula!). Catalog in MODS and in: /home/mpedani/MODS-CATALOGS/Astrometric-Catalog-Sept10.cat

Flexure During Guiding

See section 6.5 of Jesper's AGW Commissioning Plan. Measure flexure as AGw rotates crossing meridian at several elevations.

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)

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......

Continue to the Performance Verification Activity

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 - 08 Sep 2010

This topic: Commissioning > Main > WebHome > Com201009MODSplan
Topic revision: 01 Nov 2010, MarcoPedani
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