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

Rene Laporte & SOAR (12 th - 14 th May, 2008) Management – Steve Heathcote – Brooke Gregory – Andrei Tokovinin Electronics – Ricardo Schmidt – Manuel Martinez – Esteban Parkes Software – Marco Bonati – German Schumcaher Mechancial – Patricio Schurter – Eduardo Serrano Optical – Roberto Tighe

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

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.

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.

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

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

Seeing measures (Tokovinin)

Detector Cooling System (LN 2 -vs- CryoTiger) Initial motivation for visit to SOAR - visits to CTIO labs, Telescope, LCO offices. CTIO labs: – Example LN 2 dewars (weight/size/hold-time issues) – Notional solution using LN 2 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 PDR

Backend of IMAX (LCO)

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