advanced concepts & science payloads office eddicam/est meetingpage 1 ccd procurement schedule...

Advanced Concepts & Science Payloads Office

Eddicam/EST Meeting

CCD Procurement

• Schedule driven• Review off-the shelf availability• Specific mode of operation – match requirements ?• Review test, characterisation and calibration requirements


Eddicam/EST Meeting

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


Eddicam/EST Meeting

Schedule (ii)


Eddicam/EST Meeting

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


Eddicam/EST Meeting

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


Eddicam/EST Meeting

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


Eddicam/EST Meeting

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


Eddicam/EST Meeting

Modes (contd.)


Eddicam/EST Meeting

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)


Eddicam/EST Meeting

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………..


Eddicam/EST Meeting

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..


Eddicam/EST Meeting

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?


Eddicam/EST Meeting

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 ?


Eddicam/EST Meeting

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 ?


Eddicam/EST Meeting

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

advanced concepts & science payloads office eddicam/est meetingpage 1 ccd procurement schedule...

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