Dark Energy Camera (DECam)

1
Dark Energy Camera (DECam)

• Progress
• Schedule
• Plans

2
Progress Decisions(?)

• Cooling
• Del is looking at a new N2 design, avoids
  possible vibrations from pulse tubes, but need to
  understand space issues
• Optics
• 2.1 deg FOV decided at Dec. Meeting
• Optical Designer from NOAO is evaluating the
  designs
• expect a report in 2-3 weeks
• Cost estimate
• 0.5M for glass,1 year
• 0.5M for assembly, 6month
• French is in contact with Designer and has more
  details

3
Default Prime Optics 2.1df Deg, 3.46 sq. deg.

• aspherical surfaces
• 4 elements flat window
• d1 900mm
• focal plane 440 mm diameter
• length 1555 mm

22 (566mm)
Filters
4
Progress Cont.

• Optics Cont.
• Greg did FEA of components
• sags small except for window
• need to discuss results with optical designer
• window needs to be thicker

5
CCDs

• LBL/SNAP type CCDs
• Good Qe in infrared
• 10.5 micron pixels, 3.5k x 3.5k and 4 RO
  channels/CCD, 4-side abuttable
• LBL/SNAP CCDs with larger pixels We are
  pursuing this one (William)
• keep package size same as SNAP (overlap
  development)
• set pixel size to match our needs (15microns)
• E2V CCDs -
• low Qe in infrared might be improved to match
  LBL
• 15 micron pixels, 2kx4k, 2 RO channels/CCD ,
  3-side abuttable
• Delivery estimate complete 2 years ARO and we
  cant order until Oct. 05
• cost 60k/CCD 70? 4.2M one PO

6
LBL CCD Details

• Jim Fast and William visited LBL a couple weeks
  ago
• CCD status and options
• packaging issues
• CRIC chip (signal processing inside the dewar)
• They put together a WBS cost and schedule
• and included 1st labor estimates
• Summary
• Delivery estimate CCDs unpackaged in 1 yr
• 1 yr to package and test
• Cost 1M 1M labor?
• cost spread out, prod. order 350k (Jims talk)
• LBL and E2V both 2 year delivery LBL route
  is cheaper
• need to follow up on packaging issues and keep
  E2V option open

7
LBL CCD acquisition and packaging schedule

• Total cost is 1.1M for MS (no labor or
  overhead)
• Includes CCDs, CRIC Chips, hybrids (each could be
  critical path)

8
Guiding

• Can put guide CCDs on focal plane or have pickoff
  prisms that direct light to external guide
  cameras
• seems cleaner to have them on focal plane this
  is what we are pursuing
• We need area of 50 arcmin2 to have at least one
  star in guiders (Joe Mohr)
• Tim Abbott update rate for guide drivers is 2
  sec. and no min. step size
• Once shutter is open
• accumulate image on full guider area
• readout CCDs
• pick the guide star (software)
• tell the guiding software which pixel subset to
  readout and follow
• LBL has developed guide CCDs, LICK observatory
  is packaging them
• 24 um pixels (0.44) 470 x 1264 - 31
  arcmin2/CCD
• Need to find out more about these chips readout
  time etc.
• Note LBL/SNAP CCDs have a reset function
  could be used to zero the image CCDs after a
  guide star is identified

9
Focus

• Tim Abbott What Blanco has now
• Focus is automatically adjusted for temp drift
  with each exposure
• Typically additional adjustment by observers 2-3
  times/night, takes 5 min to take images and make
  the adjustment
• Would be advantageous to have fast automatic
  focus built in
• ESO Omegacam and SDSS have CCDs in dewar above
  and below the focal plane seems like we should
  do this too
• Range of motion required 2cm (current mosaic has
  4cm)
• Could use same CCDs as for guiding
• Longer integration time one CCD above and one
  below should have a star in each one

10
Focal plane
Use SNAP sized CCDs for main image Guide CCDs
need 2 LBL/LICK CCDs have 2 more for
redundancy (avoid single point failure) Focus
CCDs use same chips as guider one CCD below and
one above best focus plus 2 more for
redundancy 8 guide/focus CCDs
11
Focal plane layout with E2V CCDs

• 66 CCDs (CCD44-82)
• 4096 x 2048, 2 RO channels/CCD
• 15 micron pixels
• 3 side abuttable , no (GR)
• 68 of circle is active
• 66 CCDs

12
Over Project Schedule

• Production CCD order Oct. 05 (FY06)
• Focal plane assembly complete July 07
• Full system testing complete Feb. 08

13
End Game

• Ship to Chile in Feb. 08
• commission 5 months?
• First useful data Oct. 08

14
Whats missing?

• Shutter Iris or rollers?
• Filters diameter 550 mm much bigger than
  usual
• need to talk to some vendors
• DA CRIC MONSOON, number of crates etc
• ??
• ??
• Plan for preparation of PAC proposal
• 1st full draft by mid Feb.
• Review and rewrite 2wks
• Turn in March 8th

15
Mayall Mosaic Camera and electronics
16
Blanco with 4 element ADC corrector (used with
Mosaic)
Primary cage rotates such that secondary mirror
can be used without removing camera
F/8 secondary
17
Terebizh2.12 Deg FOV, 3.46 sq. deg.

• spherical surfaces
• 5 elements curved window
• d1 900mm
• focal plane 427 mm diameter
• length 1744 mm

22 (570mm)