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December 5, 2004

Keck LGS AO Planning Workshop: Overview, Requirements & Schedule. December 5, 2004. The LGS AO Team. LGS AO Control. Light from Telescope. Offload to telescope. TTM. Tip/tilt. LGS. NGS. IR transmissive dichroic. Science Camera. DM. Offload focus to telescope. Sodium

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December 5, 2004

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  1. Keck LGS AO Planning Workshop: Overview, Requirements & Schedule December 5, 2004

  2. The LGS AO Team

  3. LGS AO Control Light from Telescope Offload to telescope TTM Tip/tilt LGS NGS IR transmissive dichroic Science Camera DM Offload focus to telescope Sodium transmissive dichroic STRAP Wavefront Controller Lenslets WFS LBWFS TSS x,y,z stage Focus (Tip/tilt to Laser) Centroids Pupil Orientation (Subaperture gains)

  4. Dye Laser

  5. Laser Table (on EL ring)

  6. Proposed Top Level Requirements • Sky Coverage • Strehl Ratio • PSF stability & knowledge • Observing Capabilities (nodding, science fov, etc) • Observing Efficiency • Reliability & uptime • Cost (to operate & maintain) • Schedule (timeliness)

  7. 1. Sky Coverage 1Bahcall & Soneira, 1981; 2Keck Report 208, 1996. 1Bahcall & Soneira, 1981; 2Keck Report 208, 1996. LGS NGS

  8. 1. Sky Coverage • 80% at 45° GL requires NGS R=19 & 60” tip/tilt fov • STRAP/LBWFS magnitude limit: • Demonstrated V=16.4 with STRAP • Demonstrated V=15 with LBWFS • At V=17.1 found Na background to be ~ equal to NGS flux. Have installed sodium rejection filter. • At V=17.1 found bench background ~ ½ of NGS flux. Subsequently reduced one source. Still need to deal with STRAP filter wheel source. • STRAP/LBWFS field of view: • Current fov > 30x30” (somewhat off-centered). • Off-axis vignetting by acquisition fold beamsplitter to be addressed

  9. 2. Strehl Ratio • Strehl requirement at K’ • SR  0.25 for V  16 • SR  0.1 for V  19 • Status: • In NGS mode achieve SR = 0.52 at K’ for V = 9 • Demonstrated SR = 0.36 at K’ for V = 14 NGS w/ excellent seeing • Achievable Strehl ratio defined by error budget • MK seeing campaign (Oct&Dec/02; 10-nights) measured d0= 4-5m. • Subsequent work on reducing background, optimizing STRAP & realigning LBWFS should help performance • 2nd LGS milestone requirement has a high priority on demonstrating • SR = 0.2 for V  15 & SR = 0.1 for V  17

  10. Error Budget

  11. First LGS Results(UT 9/20) Extraordinary seeing

  12. LGS Image on Acquisition Camera 30 sec ACAM Image 250 counts at 500 Hz Best spot 1.1x1.7” 11/17/03 9:49 HST

  13. 3. PSF Stability & Knowledge • No requirement currently defined • Laser power & image size stability may be important

  14. 4. Observing Capabilities • Science Instruments • NIRC2, NIRSPEC, OSIRIS (July/04 1st light) • Science Object & LGS Positioning • Independent positioning over 40x40” NIRC2 field of view. • Able to position science object to NGS-level accuracy. • Able to position LGS to  0.5” • Elevation range • Able to observe from 30°  EL  85°. • Nodding • Two modes: LGS fixed or moves with science object. • Maximum individual nod  10” • Rotator • Vertical or position angle mode

  15. 5. Observing Efficiency • Corrected images on science camera after slew •  2 min longer than the LBWFS exposure time •  5 min for a V=19 NGS • The NGS autosetting tool requires ~ 1 min after slew • Nod time  20 sec (including opening & closing loops) • Requires STRAP integration into WFC for automation • Laser overhead  30 min/night • Currently achieving this • Additional potential time losses. Shuttering of laser due to: • Cirrus/clouds. • Laser traffic control collisions. 1-4 times per night. • Aircraft. Very rare. • Satellites. Space command has provided no blackouts.

  16. 6. Reliability, Uptime & Operability • Reliability & Uptime •  10% of nighttime lost to problems • Achieved 2.5% with K2AO for 5 Interferometer runs between April & Oct. (143 clear hrs) • Average uninterrupted observing time > 3 hrs • Achieve this now for NGS • All software tested & released in a controlled version. • Successful completion of an operational readiness review (ORR).

  17. 7. Operational Costs • Maintenance • Requirement: •  2 days of laser maintenance / month •  1 day of LGS AO maintenance / month • $50k/yr in parts (primarily for laser) • Run setup & calibrations • Requirement: •  1 day of AO expert & 1 day of laser expert / run •  2 hrs of AO expert & 2 hrs of laser expert / night • Currently: • Laser: 1 day prior to run + ~ 5 hrs on 1st day of run + ~ 3 hrs on subsequent days. 2-3 people. • AO: ~ 5 hrs on day of run + ~ 2 hrs on subsequent days. ~ 5 people.

  18. 7. Operational Costs • Nighttime Operation • Requirement:  1 AO/laser expert in addition to regular crew. • Currently entire team for engineering nights. • Laser at Summit: Chin & Lafon all night, Lynn for start-up + 4 spotters • LGS AO at HQ: Bouchez, Hartman, Johansson, Le Mignant, Stomski, Summers, van Dam, Wizinowich • For 2nd milestone reduce to 3 AO + 1 laser expert + spotters • Plan to test remote laser nighttime operation in Dec. • All monitoring from summit control room during Nov. night • Currently small tweaks needed at least at start of run (but getting better) • Need to implement at least wide field camera(s) to get FAA approval for no spotters. May also require mosaic radar. • Cost Summary (assuming 10 runs & 70 nights/yr) • Maintenance + setup + nighttime = 3d/m*12m + (2d/r*10 + 0.5d/n*70n) + 1.5d/n*70 = 196d = 0.9 FTEs • Labor + parts  $150k/yr

  19. Requirements Summary Potential Criteria • Performance Success Criteria: • Achieve a Strehl  0.25 in Kp for a V  16 mag NGS. • Achieve a Strehl  0.1 in Kp for a V  19 mag NGS. • Corrected images on science camera  5 min after slew. • Nod time  20 sec (including opening & closing loops). • Operability Success Criteria: • LGS AO operation over 30°  EL  85°. •  40x40” field of view to science camera. •  60” diameter field for tip/tilt & LBWFS NGS. • Nodding demonstrated over a  5x5” field. • Vertical and positional angle modes. •  10% of nighttime lost to problems. • Average uninterrupted science time > 3 hrs. • All software tested & released in a controlled version. • Successful completion of an operational readiness review (ORR). • Operational costs  $150k/yr. LGS AO operable by OA +  1 expert

  20. 8. Schedule: LGS AO Top-level Milestones • Top-level milestones (as of fall/02): • 9/03 - 1st corrected images on NIRC2 with laser • Achieved Sept. 18 & 19, 2003 • 12/03 – LGS AO facility operable by AO experts • 3/04 – 1st engineering science • 6/04 – 1st shared risk science • 3/05 – Operable for science by OA & 1 expert • 6/05 – 1st queue scheduled science? • How important is timeliness? • ESO & Gemini should have lasers in 2004

  21. Current Emphasis LGS facility operable by AO experts (12/03) & 1st eng. science (3/04). • Performance Success Criteria: • Achieve a Strehl > 0.2 in Kp for a V > 15 mag NGS. • Achieve a Strehl > 0.1 in Kp for a V > 17 mag NGS. • Corrected images on science camera < 5 min after slew. • Nod time < 20 sec (including opening & closing loops). • Operability Success Criteria: • LGS AO operable by 3 AO + 1 laser expert (+ NIRC2 operator). • All software tested & released in a controlled version (by Dec. 15) • Demonstrate correction over 50° < EL < 85°. • Off-axis science demonstrated for a target > 20 arcsec from NGS. • Nodding demonstrated over a 5x5” field. • Numbers indicate relative priorities. • Faint performance higher priority than off-axis operation • Performance documentation included in above tasks.

  22. Current Emphasis - Task Flow Down

  23. Science Demonstration • Engineering science demonstration (see DLM presentation) • Includes system characterization for science • Shared risk science • LGS AO availability for shared risk science with NIRC2 in 04B (starts Aug/04) requires Observatory notification by ~ Feb. 3. • Will have had Dec. eng. nights + Feb. 1&2. • Need to document performance for this shared risk availability. • Available for shared risk science with OSIRIS in 05A? • Science operations • Operational Readiness Review by early Aug. for 05A (or early Feb. for 05B). Initially with NIRC2 only. • Handover to Operations Group • Handover Review (after 1 or 2 semesters of science).

  24. K2 AO Observing Schedule (12/03-7/04) 39% of nights use AO

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