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COROT WEEK Liège 4-7/12/2002.

COROT WEEK Liège 4-7/12/2002. (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

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COROT WEEK Liège 4-7/12/2002.

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  1. COROT WEEK Liège 4-7/12/2002. (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. CorotWeek 3, Liège 4-7/12/2002

  2. 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 2003. Test of the CCD mechanical models: ---> Delivery for the MIQ Camera in December 2003. Bench dedicated to scientist for photometric experiment: ---> From May 2003. CorotWeek 3, Liège 4-7/12/2002

  3. 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). CCD information ???? Happiest flying mascot!!! CorotWeek 3, Liège 4-7/12/2002

  4. Working point (1) • Optimize 3 bias voltages VOD, VRD, VOG • Measurement of the video signal for different values of the bias voltages: • Same working range for the 3 CCDs FM: CorotWeek 3, Liège 4-7/12/2002

  5. 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-. Sensibility is given in e-/mv. CorotWeek 3, Liège 4-7/12/2002

  6. Dark at –40°C • Dark mean value: Spec: < 0.5e-/px/s at –40°C • No cosmetic (all pixels < 100e-/px/s) Histogram of the mean value of 32*32 pixels windows over the CCD Mean value 80% of windows CorotWeek 3, Liège 4-7/12/2002

  7. PRNU (Pixel response Non Uniformity)(1) Obtained with flat illumination l= 420nm, Dl = 10nm l= 950nm, Dl = 10nm l= 700nm, Dl = 10nm Give the uniformity of the thickness ---> Fringing Pattern Give the uniformity of the physical characteristics ---> High homogeneity Give the uniformity of the state surface and AR coating ---> Surface Pattern CorotWeek 3, Liège 4-7/12/2002

  8. PRNU (Pixel response Non Uniformity)(2) • 64*64 windows of 32*32 pixels (no side effects by removing pixels). • In each window (i,j), we calculate • - the mean value mi,j • - the standard deviation si,j • Global PRNU = dispersion of the mean values of the windows, standard deviation of the mi,j. The Global PRNU is not a relevant parameter. • Local PRNU = dispersion of the pixels values inside each window, mean value of the si,j. CorotWeek 3, Liège 4-7/12/2002

  9. 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: s GT is the gain of the complete video chain (e-/ADU) 1 ADU of the ADC = 76.3mV Results at –40°C: CorotWeek 3, Liège 4-7/12/2002

  10. 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. CorotWeek 3, Liège 4-7/12/2002

  11. Image pixel Saturation Full Well Capacity in Flat Field E2V data: 2 groups of CCDs - 3 CCDs with a FWC < 90ke- - 7 CCDs with a FWC > 100ke- CorotWeek 3, Liège 4-7/12/2002

  12. Left output Right output Full Well Capacity with a PSF 2 sizes of PSF 3 positions on the CCD F = 20 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 F = 50 pixels CorotWeek 3, Liège 4-7/12/2002

  13. 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 (aG ~ -4000ppm/K) Temperature Coefficient of Quantum Efficiency aR = temperature coefficient of the CCD response aG = temperature coefficient of the CCD gain aQ = temperature coefficient of the quantum efficiency But the temperature coefficient of the CCD response is about 1500ppm/K CorotWeek 3, Liège 4-7/12/2002

  14. 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 4-7/12/2002

  15. 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 <0.5e-/s ---> 3 to 10e-/s Rapid evolution with the temperature gives strong constraint on the CCD operational temperature ---> Under -40°C. No possible recovering on board… Aïe!! Defect are less than 1/10000 pixels. CorotWeek 3, Liège 4-7/12/2002

  16. Selection of the flight models • 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. Could avoid random choice if more than 4 CCDs are still alive after the test campaign!!! CorotWeek 3, Liège 4-7/12/2002

  17. 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 CCD parameters CorotWeek 3, Liège 4-7/12/2002

  18. Map of the dark noise • Dark noise is due to the poissonian statistic of the dark current : Value of the dark current Mask for photometry Psf Here each pixel indicates the max value in the 32*32 pixels windows We obtain an image, each pixel indicates the dark noise at that position CorotWeek 3, Liège 4-7/12/2002

  19. 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 Flat fields Convolution with the PSF 350-550 nm Computation of the jitter noise sum 550-750 nm Each pixel indicates the max value of the jitter noise inside the 32*32 pixels windows 750-950 nm CorotWeek 3, Liège 4-7/12/2002

  20. Photon noise Specification (1/10 photon noise) Dark noise Jitter noise Jitter and dark noise • On the curve we plot : • Photon noise versus the star magnitude. • Noise specification. • Average Value of the jitter and dark noises. Jitter noise Average ~ 7.5 ppm Unit : ppm Dark noise Average ~ 11 e- Average value calculated over all the CCD surface CorotWeek 3, Liège 4-7/12/2002 Unit : e-

  21. Photon noise Specification (1/10 photon noise) Dark noise Jitter noise Jitter and dark noise Jitter noise Average ~ 7.5 ppm Unit : ppm Jitter default Dark noise Average ~ 11 e- Unit : e- CorotWeek 3, Liège 4-7/12/2002

  22. Other parameters • Variation of global CCD response with temperature (Gain and quantum efficiency) • Coefficient ~ 1500 ppm/K => Variation of about 10 ppm (with T=5.10-3K) • Quantum efficiency • Values (E2V data): • Pixel capacity • Values (E2V data) CorotWeek 3, Liège 4-7/12/2002

  23. For seismology : Pixel capacity Quantum efficiency Temperature coefficient Jitter noise map For exoplanets : Dark noise (strong defects, will evolve with radiations!) Jitter noise map (strong defects) Quantum efficiency Pixel capacity Temperature coefficient Parameters priority CorotWeek 3, Liège 4-7/12/2002

  24. CCD quality • All important parameters on the same diagram • Compare CCDs between them => Example of 2 CCDs (seismology PSF) : Best CCD CorotWeek 3, Liège 4-7/12/2002

  25. Conclusion • Methods are developed to sort the CCDs • Now : • Applied these methods on the bench data • Choose 2 CCDs for each scientific program CorotWeek 3, Liège 4-7/12/2002

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