Blanco Telescope and DECam Alistair Walker ACTR meeting 22 March 2013

4 slides from DES Directors Review this week To date (7.5 months) DECam has proved to be mature and reliable; DES-SV and Community observations have had outstanding on-sky time fraction for a new instrument. Telescope tracking/guiding issues resulting in degraded image quality have been fixed, after effort on several fronts. The focus of effort now turns to improving the thermal behavior of telescope and dome, and to understand the telescope opto-mechanical properties. CCD performance meets the specifications, but work will continue on both device characteristics and pipeline calibrations with a goal of reducing photometric errors from 2% to ~0.5% (see parallel session talks) SISPI – and friends – very mature, see 6997 DES Dirs Review, Mar 20-21, 2013

Down time In the last 30 nights of scheduled observing: 260 night-time hours 11 hours lost, ~ 8 hours telescope, ~ 3 hours DECam 4.5 hours in 2 events (both involving re-booting multiple computers) This is 4%. DES Dirs Review, Mar 20-21, 2013

Image Quality - Opto-mechanics Is the Active Optics System working optimally? Why does the present hexapod LUT behave anomalously in the South-East? Why do the BCams not agree well with the Donut analysis? How much hysteresis is there? How important is it to have a primary mirror supports LUT that varies with sky position? These questions bear directly on the delivered image quality They also bear on the pointing accuracy and the observing efficiency Need the Michael plot, look at the IQ table DES Dirs Review, Mar 20-21, 2013

Image Quality – Telescope & Facility See CFIP Blanco Environmental Control System Report, DES-doc 4337 Almost all the short-term recommendations have been implemented A longer-term recommendation, better control of the daytime dome temperature, is in the planning phase The primary mirror daytime cold-air blower was off-line during much of the SV period The hydraulic oil cooler is still off-line DES Dirs Review, Mar 20-21, 2013

Possible Major Upgrades The installation of an air handling unit (or units) in the dome plus installation of a new set of 2.5 inch pipes from the outside-dome chiller is presently being estimated. Cost is likely to be of the order of $50K. It is likely that funds will only become available in FY14, that is a discussion that will take place when we know the costs (end of March). The replacement of the Blanco primary axial support transducers (33) is about to be estimated. Assuming we do this project, it is likely to be both quite expensive and manpower-intensive, and require telescope down time, thus it’s difficult to contemplate doing this before the 2014A semester.

March Replace Tachometer Oil Seal (Patricio) Telescope tracking adjustment (German, Michael) Guider tests (Alistair) Skymap to build a primary mirror support LUT (Alistair) Exposure to exposure efficiency tests (Alistair) Check dome positioning (Alistair, Omar) Test suite of observations (Alistair)

April Oil scrapers? (Freddy) Install PF cage covers (Freddy) Install mask on the g filter (Patricio) Another set of all-sky measurements with the laser system + bigger CCD camera, and Bcams (Roberto, Freddy, Tim) Test suite of observations (Tim)

May Hydraulic oil cooler (Esteban, Edison) Sequence code changes? (Juan Estrada) Install better pointing model (if not before, German, Rolo) Test suite of observations (Alistair)

June Test suite of observations (Alistair) F/8 work (Tim et al.)

July Warm up DECam (Telops, Alistair) Install replacement LN2 pump (Herman Cease, Freddy, Telops) Fix leaks, general maintenance of LN2 system (ditto) Install masks on the other 5 filters (Freddy, +?) Disable remaining fan sensor, replace two fans (Terri Shaw, Lee Groves, Telops) Rewire remote crate switch, check grounding (Steve Chappa)

On-going activities, plus work not assigned to a particular time slot yet Tune the daytime mirror cooler algorithm (Alistair, Edison) Install remaining temperature sensors (Edison) Plumb second NESLAB (Telops) Plumb second roughing pump in Cass cage (Telops) Plumb second air compressor (Telops) Telemetry for LN2 hoses vacuum jackets (Marco) External photodiode bright-light sensors (Marco) Backup generator for pumps (Marco) Install accelerometer on PF cage (Michael)