Tim Abbott DECam & CTIO

Tim Abbott DECam & CTIO DECam will greatly expand and extend wide field imaging capability at CTIO DECam makes new demands on Blanco image quality, reliability, efficiency and functionality. CTIO is responding by investigating and improving telescope performance, improving image quality, and upgrading telescope systems to adequately support DECam. DECam must also fit within the NOAO system as a facility instrument, the design reflects this.

Tim Abbott DECam & CTIO: CTIO’s preparations, recent Radial support mechanism now understood –24 supports, 3 pivot points each; complex, gravity-driven system. –Supports were detaching from the primary due to mechanical interference and accumulated misalignments resulting from inadequate repairs. Primary mirror movement identified and (partially) resolved –Broken radial supports generated imbalances in the radial support system –Primary mirror movement in cell involved hysteresis and was unpredictable

Tim Abbott DECam & CTIO: CTIO’s preparations, recent Primary mirror repositioned 2.3mm in z-direction Primary mirror is now centered in cell –Coma was dominant and variable, is now the third most significant aberration and stable. Image Quality obtained by the SuperMacho program, 2005B, airmass corrected, VR filter to , Blue: pre-shutdown, red: post-shutdown, approx equal number (~580) exposures each.

Tim Abbott DECam & CTIO: CTIO’s preparations, recent Radial support counterweights augmented Telescope flexure measured –Movements of primary w.r.t. corrector no longer show hysteresis and are believed to be due to flexure. Aluminization chamber upgrade underway Two degree slew time reduction from 35s to 17s - feasibility established Telescope FEA model built, drawings supplied, design limits explored

Tim Abbott DECam & CTIO: CTIO’s preparations, to do and under way Complete radial support repairs –Either: complete review of repaired supports & retune as necessary –Or: upgrade & re-site all radial supports to virgin glass TCS upgrade –Retire irreplaceable, obsolete components –Move to modern, integrated system (Linux, ethernet, current gen PMAC, tape encoders) –To incorporate & supply observation telemetry & metadata Cleanroom –Coude room, required for assembly, testing & future repairs

Tim Abbott DECam & CTIO Significant upgrades will come with the instrument itself: –Alignment sensors and active alignment correction –Contemporaneous focusing –Active instrument cooling –New corrector (better design, not damaged!)

Tim Abbott DECam & CTIO: Integration & Community Use DECam is to be a facility instrument. DECam will replace Mosaic II and must offer the same functionality and similar flexibility –f/8 secondary (top-end flip) DECam U band is limited by CCD response, Mosaic II by corrector transmission → ~same efficiency Filters –Must be able to use non-DES filters on non-DES nights 6 filter positions minimum, 8 preferred (Safe change procedure) Observing environment –Observer interface –Integration into NOAO Science Archive

Tim Abbott DECam & CTIO: Integration, Physical Envelope Installation & integration considerations –Mechanical limits (Instrument max mass ~5 tons) –Interfaces –Assembly –Mounting (DECam replaces the entire top-end, excluding top- rings and spider) –Alignment (Hexapod) –Commissioning –Environmental conditions: Temperatures, humidity, orientation changes, earthquakes –Maintenance, spares, tooling, documentation –Operations

Tim Abbott Documents in preparation Much of what has been discussed here is already incorporated in the design, and will be laid out in detail in the following documents: Integration Plan Defines the interfaces between DECam, the Blanco Telescope and the outside world Installation Plan Defines procedures and responsibilities for the initial installation of DECam Operations and Maintenance plan Defines and documents the procedures and responsibilities for servicing DECam. Community use document Defines and documents the needs of the NOAO/Blanco community for DECam.

Tim Abbott DECam & CTIO END

Tim Abbott

Tim Abbott Radial Support M C B D E P G H A F F One radial support, in below- mirror (compression) position. M: Primary mirror H: H-bar attachment to primary (old style) A: Lever arm C: Counterweight D: Cast bracket E: Plug, fits into socket (not shown) mounted on inside of telescope barrel B: Point of attachment to mirror cell F: Force vector radial support applies to primary mirror G: Gravity vector P: Pivot points.

Tim Abbott

Tim Abbott Current H-bar design: Strains are not uniform in the pads

Tim Abbott New H-bar design

Tim Abbott – another spin around the pole

Tim Abbott m TCS Upgrade: Current TCS Rack VME Chassis (Obsolete comms board) VME Interface (Wire-wrap & breadboarded components) Drive Interface (Wire-wrap and breadboarded components) Power Supplies

Tim Abbott Existing Blanco TCS

Tim Abbott m TCS Upgrade: Rack Evolution Proposed Rack TCS App + TCS Kernel (Industrial PC) Dome Control (Industrial PC) Dome Control Interface Utility PC Lamps and Guider Utility Interface Mount Control Mount Control Interface Power Supplies Current Rack

Tim Abbott Current TCS: telescope control PMAC TCS (algorithms) 10Hz VME GUI SunOS, ctiot2 Incremental encoders Absolute encoders Telemetry & Interlocks Motors

Tim Abbott SOAR control model IN → PID → OUT SetpointStatus Motor Controller TCS App Kernel Setpoint Position Status Telemetry Encoders Motors Interlocks GUI In SOAR this is proprietary

Tim Abbott Planned Blanco TCS TCS App (Linux PC) GUI (Linux PC) Instrument Motor control PMAC Utility (Linux PC) Active OpticsTemperature sensors Guider Comp. lamps PFADC Encoders Interlocks PXI Ethernet

Tim Abbott Shutter specifications Shutter performance requirements are based on the precision required to make calibrations via standard star observations: The shutter should provide 1 percent uniformity at a 1 second exposure time. (i.e. the actual exposure time anywhere on the CCD should not be more than 1% different from anywhere else at this exposure time). Shutter exposure time repeatability should be better than seconds (5 milliseconds). Shutter exposure time accuracy should be such that the offset from the nominal exposure should be less than 0.05 seconds (ie 50 milliseconds) Absolute timing of an exposure should be measured to a precision of 10ms and recorded in the resulting image FITS header. The shutter should allow exposures from 1 second upwards. We will not test performance for shorter exposure times, but capability to take shorter exposures (e.g. down to 0.2 seconds) would be useful as goal, not a specification. Performance maintained -5C to +20C. Performance maintained after high duty-cycle tests, 7. Approximately 125,000 shutter movements will take place per year, Shutter MTBF and MTTR should be based on a 10-year lifetime. Monitoring and diagnosis of performance anomalies (Uniformity, Repeatability, Accuracy above) would be aided by suitably telemetry from sensors associated with the shutter mechanism.

Tim Abbott Community Filters Filter review panel recommends considering: –BVRI –wide VR –SDSS u –Washington C –DD 051 –Hα –[OIII] –[SII]

Tim Abbott DECam as community instrument DECam will replace Mosaic II in all respects therefore must be able to perform as Mosaic II f/8 function must be maintained DECam U band limited by CCD response, Mosaic II by glass → ~same efficiency Shutter performance – driven by standard star observations, minimum exposure time 1s Filters – current concept is for 6, possibly 8. 4 DES, remainder for community Community/NOAO will have to purchase own filters beyond DES 4.

Tim Abbott DECam & CTIO: CTIO’s preparations, previously High-quality primary, D80 at manufacture: 0.25” Active Optics –33-pad system, LUT driven, updated every few months –DECam will provide in-line updates (via “donut”) possibly allowing us to close the loop during observations

Tim Abbott DECam & CTIO: CTIO’s preparations, previously Thermal Environment improvements –Dome ventilation doors at telescope level –Dome covered with thermally insulated aluminum panels –Air ventilation around primary mirror and telescope structure –Better thermal management throughout the building, servo- control optimized system.