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LBTO PSF Subsystem

LBTO PSF Subsystem

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LBTO PSF Subsystem

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  1. LBTO PSF Subsystem April 24, 2007 Chris Biddick 1 cjb

  2. Introduction • The Point Spread Function Subsystem (PSF) controls the optical collimation and active optics on one telescope side • Primary mirror collimation • Secondary mirror (hexapod) collimation • Tertiary mirror collimation • Primary mirror active optics • Secondary mirror active optics • Arbitration among all the above 2 cjb

  3. Introduction (2) • Gets commands from the CSQ/IIF, (PCS, GCS, AOS), and GUI • Sends commands to the PMC, (OSS, AOS) • Partly finished – currently supports primary mirror collimation and active optics 3 cjb

  4. Subsystem Command Classes • PrimaryMirror – 14 commands • PSF – 2 commands 4 cjb

  5. Primary Mirror Collimation • Collimation file • Altitude compensation • Temperature compensation • Active optics focus and coma • Global offsets • Entered by TO • Instrument offsets • IIF stepFocus for example • All above values are summed for each DOF 5 cjb

  6. Primary Mirror Collimation File • A file for each instrument • Generated by observing staff from instrument data with IDL program • [S|D]XPM<inst>Collimation.dat • Currently part of the TCS distribution • Only SXPMLBCCollimation.dat has real data 6 cjb

  7. Primary Mirror Collimation File • Altitude compensation • Adjusts mirror position (translation and rotation) as a function of altitude • Table quantized in 0.1 degree steps from -2 to 92 degrees • Temperature compensation • 3rd order polynomial in delta temperature for each DOF (X, Y, Z, Rx, Ry, Rz) • Currently only linear term for Z is used 7 cjb

  8. Primary Mirror Active Optics • Zernike coefficients from instrument • Supports up to 56 coefficients • Uses Buddy Martin’s code to correct distortions with mirror bending modes • Focus and coma are normally handled by moving the mirror (added to collimation) • Calculated forces are sent to the PMC which does sanity check 8 cjb

  9. Zernike Polynomials 9 cjb

  10. Z5 Correction Surface displacement Correction forces 10 cjb

  11. Z16 Correction Surface displacement Correction forces 11 cjb

  12. Z36 Correction Surface displacement Correction forces 12 cjb

  13. Z5+Z16+Z36 Correction Surface displacement Correction forces 13 cjb

  14. Z5+Z16+Z36 Correction Total correction Total forces 14 cjb

  15. CSQ requests • Set new instrument • Loads collimation table • Set mirror position (instrument offsets) • Step mirror position (instrument offsets) • Set Zernike coefficients • Adjust mirror • Calculates forces and sends to PMC 15 cjb

  16. Future directions • Secondary mirror (hexapod) collimation • Tertiary mirror collimation • Only has four degrees of freedom • Secondary mirror active optics • Offloading • Adaptive optics to hexapod, primary • Hexapod to/from primary • To/from tertiary • Arbitration 16 cjb

  17. Active Optics Command & Data Flow Primary Mirror Cell PMC (position / wavefront) Accumulated Wavefront PSF Diagnostics Adaptive Secondary Control AOS (position / wavefront) Secondary Hexapod Control OSS Left Right Gate Gate Primary Mirror Collimation Arbitrator PSF Secondary Hexapod Collimation Arbitrator PSF LUT LUT Gate IIF IIF Tertiary Mirror Collimation Arbitrator PSF USR USR LUT IIF Gate Gate USR Primary Mirror Active Wavefront Arbitrator PSF Adaptive Secondary Active Wavefront Arbitrator PSF LUT LUT Pointing & Guiding Arbitrator PCS IIF IIF USR USR Tertiary Mirror Unit OSS Fast Slow Slow, Incremental Slow Gregorian Case Mount Control System MCS Open-loop Pointing Model Off-axis Guiding Agent GCS Active Optics Agent GCS

  18. References • 481s060 Arbitrators for the PSF subsystem, J.M. Hill • 480s002 LBT Telescope Control System, J.M. Hill • 481s062 PSF Subsystem User’s Manual, C. Biddick 18 cjb