advanced concepts & science payloads office eddicam/est meetingpage 1 ccd procurement schedule...
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Advanced Concepts & Science Payloads Office
Eddicam/EST Meeting Page 1
CCD Procurement
• Schedule driven• Review off-the shelf availability• Specific mode of operation – match requirements ?• Review test, characterisation and calibration requirements
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Schedule
• 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
Advanced Concepts & Science Payloads Office
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Schedule (ii)
Advanced Concepts & Science Payloads Office
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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
Advanced Concepts & Science Payloads Office
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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
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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
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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
Advanced Concepts & Science Payloads Office
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Modes (contd.)
Advanced Concepts & Science Payloads Office
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Specification
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)
Advanced Concepts & Science Payloads Office
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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………..
Advanced Concepts & Science Payloads Office
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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..
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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?
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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 ?
Advanced Concepts & Science Payloads Office
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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 ?
Advanced Concepts & Science Payloads Office
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Science
• 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
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