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LBTO PSF Subsystem. April 24, 2007 Chris Biddick. 1 cjb. 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
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LBTO PSF Subsystem April 24, 2007 Chris Biddick 1 cjb
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
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
Subsystem Command Classes • PrimaryMirror – 14 commands • PSF – 2 commands 4 cjb
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
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
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
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
Zernike Polynomials 9 cjb
Z5 Correction Surface displacement Correction forces 10 cjb
Z16 Correction Surface displacement Correction forces 11 cjb
Z36 Correction Surface displacement Correction forces 12 cjb
Z5+Z16+Z36 Correction Surface displacement Correction forces 13 cjb
Z5+Z16+Z36 Correction Total correction Total forces 14 cjb
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
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
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
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