CorotWeek 3, Liège 4-7/12/20021 (working on Saturday!!!) The CCD flight models Miss Pernelle Bernardi Mr Vincent Lapeyrere Mr Tristan Buey and the CCD team at work From Meudon : Régis Schmidt, Bertrand le Ruyet, Jêrome Parisot, Didier Tiphène From CNES : Olivier Gilard, Guy Rolland (for irradiation test) Funding by CNES. COROT WEEK Liège 4-7/12/2002.

CorotWeek 3, Liège 4-7/12/20022 What’s up?? PAST. Test of electrical model on 4 chips are finished: ---> Constraints for flight electronic readout and processing. Irradiation test are finished: ---> Performances for the end of life. Present and future. Test and calibration of the 10 CCDs flight models: ---> Selection for the flight camera. ---> Delivery of the CCDs in March Test of the CCD mechanical models: ---> Delivery for the MIQ Camera in December Bench dedicated to scientist for photometric experiment: ---> From May 2003.

CorotWeek 3, Liège 4-7/12/20023 Results on the flight models 2 CCDs flight models have already been tested on the bench. A third one is under test at that time. We test one CCD every 3 weeks. High homogenety between the CCDs (7 EM and 2 FM). We have about 20Go of raw images per CCD and 1Go of reduced images. 2 steps to reach the performances of the CCDs: * Measurements of the characteristics on the bench. Working point, Dark current, PRNU, Gain, Coeff Temp, Saturation… * Software models (expected system performances and CCD characteristics). Happiest flying mascot!!! ???? CCD information

CorotWeek 3, Liège 4-7/12/20024 Working point (1) Optimize 3 bias voltages V OD, V RD, V OG Measurement of the video signal for different values of the bias voltages: Same working range for the 3 CCDs FM: CCD N°V OD V RD V OG  0.2 V13.2  0.2 V-1.9  0.2 V  0.2 V13.2  0.2 V-1.9  0.2 V  0.2 V13.2  0.2 V-1.9  0.2 V

CorotWeek 3, Liège 4-7/12/20025 Working point (2) Sensitivity of the video signal to the bias voltages : static measurement, in dynamic it will depend on the frequency and some compensations exist. About same order at worst frequency (100kHz, readout frequency). Higher sensitivities = 4e - /mV Specification for the electronics: 1mV peak to peak ---> equivalent noise of few e -. CCD N°V OD V RD V OG Sensibility is given in e - /mv.

CorotWeek 3, Liège 4-7/12/20026 Dark at –40°C Dark mean value: Spec: < 0.5e - /px/s at –40°C No cosmetic (all pixels < 100e - /px/s) CCD N°Mean value (e - /px/s)Local max (e - /px/s)80% of windows< Histogram of the mean value of 32*32 pixels windows over the CCD Mean value 80% of windows

CorotWeek 3, Liège 4-7/12/20027 PRNU (Pixel response Non Uniformity) (1) = 420nm,  = 10nm = 700nm,  = 10nm = 950nm,  = 10nm Obtained with flat illumination Give the uniformity of the state surface and AR coating ---> Surface Pattern Give the uniformity of the physical characteristics ---> High homogeneity Give the uniformity of the thickness ---> Fringing Pattern

CorotWeek 3, Liège 4-7/12/20028 PRNU (Pixel response Non Uniformity) (2) Global PRNU = dispersion of the mean values of the windows, standard deviation of the m i,j. The Global PRNU is not a relevant parameter. Local PRNU = dispersion of the pixels values inside each window, mean value of the  i,j. 64*64 windows of 32*32 pixels (no side effects by removing pixels). In each window (i,j), we calculate - the mean value m i,j - the standard deviation  i,j

CorotWeek 3, Liège 4-7/12/20029 CCD Gain (µV/e - ) The CCD is illuminated with white LEDs at several time flashes Calculation of the mean value: m the variance of the difference of 2 images with the same flash:  G T is the gain of the complete video chain (e - /ADU) CCD N°Left sideRight side Results at –40°C: 1 ADU of the ADC = 76.3  V

CorotWeek 3, Liège 4-7/12/ CCD Gain versus temperature Global gain (e - /ADU) measured at different temperatures from –45°C to 30°C The electronics gain is constant  the variation of the global gain is the same than the variation of CCD gain. CCD N° Temperature coefficient of the CCD Gain (ppm/K)

CorotWeek 3, Liège 4-7/12/ Full Well Capacity in Flat Field Image pixel Saturation CCD N°FWC (ke - ) E2V data: 2 groups of CCDs - 3 CCDs with a FWC < 90ke CCDs with a FWC > 100ke -

CorotWeek 3, Liège 4-7/12/ Full Well Capacity with a PSF Right output Left output 2 sizes of PSF 3 positions on the CCD  = 20 pixels  = 50 pixels First results: * Saturation occurs at lower values when the PSF is far from the output. * Depends on the PSF size. Traps? Results soon… in CorotWeek4

CorotWeek 3, Liège 4-7/12/ Temperature Coefficient of Quantum Efficiency Measure of the flux at: - different wavelengths from 400nm to 950nm - different temperatures from –45°C to –30°C Correction by the temperature coefficient of the CCD gain (  G ~ -4000ppm/K)  R = temperature coefficient of the CCD response  G = temperature coefficient of the CCD gain  Q = temperature coefficient of the quantum efficiency But the temperature coefficient of the CCD response is about 1500ppm/K

CorotWeek 3, Liège 4-7/12/ Results of the irradiation tests (1). 3 chips tested (4210) with protons at 4 different energies (30 to 60Mev). Tested characteristics : Working point. Gain and Full Well Capacity. Dark Current (mean value, defect). Pixel Response Non Uniformity. No transient were visible due to the too high proton flux (more than one impact on a single pixel on each image).

CorotWeek 3, Liège 4-7/12/ Results of the irradiation tests (2). Unless the dark current all the other characteristics of the CCD will not be degraded enough to impact on the system performances. Irradiation will induce in the dark current : Local defect (spatial and temporal). Global evolution 3 to 10e - /s Rapid evolution with the temperature gives strong constraint on the CCD operational temperature ---> Under -40°C. Defect are less than 1/10000 pixels. No possible recovering on board… Aïe!!

CorotWeek 3, Liège 4-7/12/ Selection of the flight models Could avoid random choice if more than 4 CCDs are still alive after the test campaign!!! The aim of this work is to develop methods to : – Determine if all CCDs are able to fly – Find criteria for each program By software models using : –The expected performances of the system (PSF, pointing, thermal stability…). –The characteristics of the CCDs measured on the bench and also at E2V. 4 CCDs have to be selected, the parameters of choice have to be optimized for the asteroseismology et exoplanets.

CorotWeek 3, Liège 4-7/12/ CCD parameters Should be used for sorting : –Dark current Noise White pixels –Pixel response non uniformity Cosmetic defects Function of the wavelength –Gain Function of the temperature –Quantum efficiency Number of electron collected Function of temperature –Pixels capacity Shouldn’t be used : –Non linearity Dominated by the electronic –Transfer efficiency –Read out noise Dominated by the electronic –Irradiation sensitivity

CorotWeek 3, Liège 4-7/12/ Map of the dark noise Dark noise is due to the poissonian statistic of the dark current : Psf Mask for photometry Value of the dark current We obtain an image, each pixel indicates the dark noise at that position Here each pixel indicates the max value in the 32*32 pixels windows

CorotWeek 3, Liège 4-7/12/ Map of the jitter noise 3 different flat fields for 3 different parts of the bandwidth Each flat field is convolved with the corresponding PSF The jitter noise is calculated with the sum of the 3 images nm nm nm Flat fieldsConvolution with the PSF sum Computation of the jitter noise Each pixel indicates the max value of the jitter noise inside the 32*32 pixels windows

CorotWeek 3, Liège 4-7/12/ Jitter and dark noise Average value calculated over all the CCD surface Unit : ppm Unit : e - Photon noise Specification (1/10 photon noise) Dark noise Jitter noise Average ~ 7.5 ppm Dark noise Average ~ 11 e - On the curve we plot : Photon noise versus the star magnitude. Noise specification. Average Value of the jitter and dark noises.

CorotWeek 3, Liège 4-7/12/ Jitter and dark noise Jitter default Unit : ppm Unit : e - Photon noise Specification (1/10 photon noise) Dark noise Jitter noise Average ~ 7.5 ppm Dark noise Average ~ 11 e -

CorotWeek 3, Liège 4-7/12/ Other parameters Variation of global CCD response with temperature (Gain and quantum efficiency) –Coefficient ~ 1500ppm/K => Variation of about 10 ppm (with  T= K) Quantum efficiency –Values (E2V data): Pixel capacity –Values (E2V data)

CorotWeek 3, Liège 4-7/12/ Parameters priority For seismology : 1.Pixel capacity 2.Quantum efficiency 3.Temperature coefficient 4.Jitter noise map For exoplanets : 1.Dark noise (strong defects, will evolve with radiations!) 2.Jitter noise map (strong defects) 3.Quantum efficiency 4.Pixel capacity 5.Temperature coefficient

CorotWeek 3, Liège 4-7/12/ CCD quality All important parameters on the same diagram Compare CCDs between them => Example of 2 CCDs (seismology PSF) : Best CCD

CorotWeek 3, Liège 4-7/12/ Conclusion Methods are developed to sort the CCDs Now : –Applied these methods on the bench data –Choose 2 CCDs for each scientific program