Brazilian Tunable Filter Imager (BTFI) Preliminary Design Review (PDR) ‏

1. Brazilian Tunable Filter Imager(BTFI)Preliminary Design Review (PDR)‏ SOAR Preliminary Interface Review (PIR @ SOAR/CTIO) (Keith Taylor) Version 1.0 USP-IAG Universidade de São Paulo 18-19th June 2008

2. Rene Laporte & KT @ SOAR(12th - 14th May, 2008) • Management • Steve Heathcote (sheathcote@ctio.noao.edu) • Brooke Gregory (bgregory@ctio.noao.edu) • Andrei Tokovinin (atokovini@ctio.noao.edu) • Electronics • Ricardo Schmidt (rschmidt@ctio.noao.edu) • Manuel Martinez (mmartinez@ctio.noao.edu) • Esteban Parkes (eparkes@ctio.noao.edu) • Software • Marco Bonati (mbonati@ctio.noao.edu) • German Schumcaher (gschumacher@ctio.noao.edu) • Mechancial • Patricio Schurter (pschurter@ctio.noao.edu) • Eduardo Serrano (eserrano@ctio.noao.edu) • Optical • Roberto Tighe (rtighe@ctio.noao.edu)

3. The Big Picture • SAM development time-scales: • Natural guide-star (NGS) operations: Sep’09 • Laser guide-star (LGS) operations: ~Sep’10 (tbc) • Consequences … • The predicted delivery of BTFI ~ SAM in NGS mode; • SAM in NGS mode not common-user -- development path to full LGS ops; • BTFI science limited by the small sky coverage offered by SAM in NGS mode; • The development time-scales for AO systems are notoriously difficult to predict • Conclusions: • IBTF on IR-Direct ISB port for first 1 or 2 years of ops • Fixed, stable configuration - what about Phoenix? • No problems with CryoTiger cooling line swaps • Commissioning of SAM & BTFI independent – minimize interference of commission teams • Worries: • BTFI’s major science impact is with GLAO

4. Optimal Instrument Configuration for SAM(BTFI advantages over SAMI) • iBTF mode allows for continuously variable filtered imaging as opposed to SAMI’s limited set of interference and B-B filters; • iBTF gives 5 > R > 5,000 cf: SAMI where R <500 range with a semi-infinite no. of filters; • iBTF’s wavelength PSF is ~Gaussian profile; SAMI is ill-defined and limited to current interference filter set; • iBTF allows observations of arbitrary red-shifts and rest-frame wavelengths without the need for new interference filters; • BTFI has two complementary outputs giving (eg) matched pairs of line/continuum observations with the same PSF and ; • BTFI uses EMCCDs which allow for optimum use of variable GLAO PSF thus maximizing benefit of SAM’s performance.

5. Optimal Instrument Configuration for SAM(BTFI disadvantages over SAMI) • SAMI is a simple camera with 12-position filters in a simple filter wheel. BTFI can only support a <8. SAMI is operationally simpler than BTFI. • SAMI has no optics and hence will have a superior efficiency to the iBTF mode of BTFI. BTFI suffers an efficiency loss averaging around ~20%. However it has 2 channels and hence more than recovers from any losses in its optical train. Conclusions (personal) • BTFI is better than SAMI in almost all respects • BTFI is highly complementary to SIFS, so SIFS+BTFI should be a winning combination for SAM.

6. SAM/GLAO issues: • SAM’s PSF is highly variable: • by factors >>2 • in time-scales of a few minutes or shorter • EMCCD on BTFI allows time-resolution of ~2s • Select frames of good PSF for incorporation into data-cube • in pipe-line data reduction? • Avoids averaging PSF over integration time • multiple sweeps using EMCCD • Much superior to convolving to worst PSF • single sweep using conventional CCD output

7. Weight / Moment constraints • Pre-PDR: • BTFI alone, assuming SAM as a rigid body • done - see Santoro’s report • Post-PDR: • SAM alone, with loads representing BTFI and SIFS; • SAM plus BTFI as an integrated unit • With SIFS as a load • Final ratification by SOAR Board

8. Seeing measures(Tokovinin)

9. Detector Cooling System(LN2 -vs- CryoTiger) • Initial motivation for visit to SOAR - visits to CTIO labs, Telescope, LCO offices. • CTIO labs: • Example LN2 dewars (weight/size/hold-time issues) • Notional solution using LN2 semi-autofill with reasonable sized dewars • SOAR Telescope: • Goodman S’graph CryoTiger cooling line routing • Static config - cf: BTFI swaps between SAM and IR-Direct port • LCO offices (with David Osip): • Frequent IMAX camera swaps – connectors a problem but not insurmountable • Lots of great advice – including stand-offs at detector (see next slide) • Summary: • No strong arguments either way (both feasible) • Decision to base-line CryoTigers for size/weight/(maintenance) reasons • tbc @ PDR

10. Backend of IMAX (LCO)

11. Other interface issues • Calibration unit is readily adapted to supply fibre feeds to BTFI (as well as large-field illumination); • Flexure in BTFI is monitored semi-continuously, • Flexure in SAM will have to be measured and open-loop corrected • SAM/BTFI mechanical interface resolved • ISB port/BTFI mechanical interface - no obvious problems • BTFI mounted on SAM interferes with Nasmyth support truss in similar way as SAM itself; • Problem resolved in principle but needs Patricio to follow through • Electronics cabling clarified • Handling requirements discussed • Control system architecture agreed (Bonati – see Giseli’s talk) • Support for CCCP-v2 & Etalon Controllers • Training and spares • Outstanding GLAO questions for Andrei