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CCD Procurement. Schedule driven Review off-the shelf availability Specific mode of operation – match requirements ? Review test, characterisation and calibration requirements. Schedule. 2007 launch is the goal (match Kepler and be available for launch in the Herschel/Planck context)

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CCD Procurement

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ccd procurement
CCD Procurement
  • Schedule driven
  • Review off-the shelf availability
  • Specific mode of operation – match requirements ?
  • Review test, characterisation and calibration requirements
  • 2007 launch is the goal (match Kepler and be available for launch in the Herschel/Planck context)
  • For the AIV campaign, need focal camera ready in 2005 (details to be evaluated with system study, e.g. need dates, serial or parallel, calibration)
  • CCDs are the long-lead item to ensure delivery of chips for camera testing in 2004
e2v devices
E2V Devices
  • CCD 42 family – used in Megacam, COROT
  • Set of common photo-lithographic mask components can be used to make a device 2048 w x (nx256) h
  • Can be used with shielded store section in framestore mode for minimal image smear & fast image readout
  • Back-illuminated, uniform response, switchable gain stage
  • Note the E2V design team is already loaded up with new projects
area vs speed trades
Area vs Speed Trades
  • Large CCD covers more target stars per observation, but serial read out increases frame period
  • For fixed CCD full-well, longer frame time implies saturation at fainter magnitude
  • Serial output register becomes bottleneck – speed of amplifier (<3MHz)
  • Row binning is ”instantaneous” and serial register can accommodate ~3 – 4 image pixels
  • Two ampliers possible – doubles video electronics resources, CCD window reconstitution at middle
ccd42 c0
  • Largest device accommodated on Si wafer
  • 3072 x 2048 image pixels.
  • 6 CCDs cover field of view efficiently
  • All other parameters identical with CCD42-80
modes of operation
Modes of Operation
  • Frame transfer, 4 (3?) rows binned to output, serial register runs 2.5MHz to one amplifier => 0.75 sec
  • Full well implies ~13 M electrons /star/sec mv ~7.7 (assuming m =11 ~6e5, but maybe 1 mag gain via. throughput estimate?)
  • To enhance brightness limit reduce accumulation time. Requirement of mv=5 implies reduce by >10
  • Either reduce height of the selected area in a CCD to 300 rows or 0.23º x 1.6 º in one CCD
  • Or use a timed accumulation and low duty cycle in one CCD (5% live time)
  • Needs careful management for cross-talk
  • Item Goal Spec Performance
  • Field View 6º dia. 2.5º dia 4.75 º x 4.75 º
  • Brightest star mv = 3 mv = 5 mv = 5 (7.7)
  • Faintest Star 15 15 14.8
  • Dyn. Range 6 6 9.8 (7.1)
  • * Asteroseismology requirements (check also PF)
other items
Other items
  • Improved yield and uniformity if relax the short wavelength QE requirement
  • Noise – limited by design for high dynamic range (~15-20 electrons rms), run in low gain?
  • E2V rely on standard silicon, so do not push for higher resistivity and enhanced red response
  • Cosmetics - drive yield . Design the software to allow to ignore 1 pixel out of any star window – relaxed cosmetic spec. follows
  • Radiation damage, speed vs. electronics………..
testing task overview
Testing Task Overview
  • Three separate areas of testing to be considered vis a vis industry procurement
  • Acceptance test against specifications
  • Radiation damage assessment
  • Test in support of algorithms, calibration, cosmic rays, photometric test bench etc..
performance verification
Performance verification
  • Does the representative prototype device meet our requirements? - Which are critical items?
  • Explore the yield of further devices to gain handle on unit cost
  • Measure several devices to gauge dispersion
  • Engineering devices to test out bread-board electronics
  • What can be done with CCD42-80? How many devices? Any front-illuminated from prototypes?
batch acceptance
Batch Acceptance
  • From the Flight Model batch verify the CCDs meet specifications
  • E2V can (and have – Megacam ?) perform this, but a testing bottleneck
  • Leave to industry camera team – efficient use of time and resources
  • “Eddicam” consortium – adds a possible delay between E2V and camera team at industry that may not be viable ?
  • Representative sampling ?
radiation damage
Radiation damage
  • Eddington is likely a benign application w.r.t. radiation damage of charge transfer – image field is repetitive and unchanging, only stability is needed
  • Operate at as low a temperature as possible
  • Small change in apparent centroid, some loss of S:N
  • Take a representative CCD42 device, and test in Eddicam mode of operation and signal levels after representative dose
  • Bad pixel generation ?
  • Test performance in the modes of operation
  • Effects of long duration photometry (cosmic rays, flickering pixels, chosen on-board algorithms etc.)
  • Different requirements of test bench?
  • Can be CCD42-80 ?
  • On-ground calibration
  • Prepare for in-flight calibration
  • End-to-end test ?
  • Decoupling from industry effort is efficient