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CIPS Calibration Review Aimee Merkel Bill McClintock

CIPS Calibration Review Aimee Merkel Bill McClintock. CIPS Science Measurement Requirements. CDR Science Requirements Document Summary. CIPS Ground Calibration Summary. Calibration Activities Unit level tests (detector components, assembled detector units, filters, lens systems)

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CIPS Calibration Review Aimee Merkel Bill McClintock

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  1. CIPS Calibration ReviewAimee MerkelBill McClintock

  2. CIPS Science Measurement Requirements CDR Science Requirements Document Summary

  3. CIPS Ground Calibration Summary • Calibration Activities • Unit level tests (detector components, assembled detector units, filters, lens systems) • Camera level tests • Preenvironmental instrument calibrations • Environmental test • Postenvironmental instrument calibrations • Post spacecraft I&T calibrations • Instrument Calibrations • CCD characterization (read noise, dark current ) • TDI (Time Delayed Integration: Nadir Cameras only) • Wavelength Range • Flat Field • Field of View • Linearity • Distortion • Polarization • Off-axis response (Stray and scattered light performance) • Spacecraft I&T calibrations • Absolute sensitivity • Postenvironmental Instrument checks (dark field) • Point Spread Function • Absolute sensitivity • Focus • Out of band rejection • Light leaks • Camera to camera alignment • Camera to reference optical surface (ROS)

  4. Calibration Measurement Summary Requirement Measurement Cameras meet or exceed all performance requirements

  5. Raw Image to Calibrated Image • Process of converting raw image in data numbers (DN) to calibrated image (Level 1A data product) in units of Gary.(1 Gary= 1 x 10-6 Albedo) Subtract stray light Stray (i,j) Correct for non-linearity Nlin Raw Image DN(i,j) Subtract Dark Dark (i,j) Place holder (no evidence of Stray light issues) Account for Sensitivity of Camera. Rinst(I,j,,T,HV)*Fsun Divide out Flat Field FF Account for integration Period ∆t

  6. Dark Image Dependence on CCD Temperature • Offset (set by electronics) • Electrical offset added to image to provide a baseline signal to avoid negative readout. • Applied after analog amplifier but before digitization. Has no non-linearity issues. • Dark Current • Thermal noise that accumulates with image read out time (accumulates over rows). • High Quality CCDs! • Typical characteristics: • Offset: ~90DN • Dark Current: ~0.1 DN/sec or 3.2 e¯/sec Electrical Offset and Dark Current vary differently with temperature.

  7. one orbit Last image one orbit 1st image Last image 1st image CIPS CCD Temperature Ranges CCD Temp only varies by 1ºC over orbit

  8. Dark Image Dependence on CCD Temperature Interpolated over orbit Temperature

  9. Linearity (N)

  10. Camera Flat Field Integrating Sphere used to uniformly illuminate Camera FOV • Variation from Pixel to Pixel due to: • Photocathode variation • Lens System: Cos4 • Flat Field Requirement: 1% Accuracy • Measured: • Relative sensitivity across the 44º FOV~ 1% or better • Repeatability of Flat images to ~ 0.1% • In-flight Image Calibration: • Divide out normalized Flat Field from each image Normalized Flat Field Percentage of Max Signal Camera 0 Flat Field Pixel Pixel

  11. Radiometric Sensitivity of Camera R(i,j) in units of DN/sec/Gary Still need to account for sensitivity dependence on Temperature (T) and High Voltage(HV)…

  12. Correct Camera Sensitivity for T and HV

  13. Calibrated Image Calibrated Image (Albedo) Raw Image Data Number DN

  14. Calibrated Image Calibrated Image in Units of Garys Level 1A data product Processing test up to Level 1A data product successful. Ready for Launch!!!

  15. Post Launch CIPS Calibration Overview • In-Flight Calibration Task List: • Absolute pointing knowledge established by viewing UV stars (0.2˚ knowledge requirement) • Detector characterization • Dark field • Intensifier characterization • Camera to camera alignment (science images) • Absolute sensitivity by viewing UV stars. • Flat Field images and Relative sensitivity over the FOV (‘clear field’ images) • Stray and scattered light performance (shadow images) • Light leaks (shutter test)

  16. Extra Slides EXTRA SLIDES

  17. CCD Acceptance Test • Each flight CCD went through extensive acceptance testing with the flight electronics. At 3 different temperatures (25ºC, -10ºC, -40ºC) analyzed dark field • Number of Hot Pixels • Read Noise Number of electrons introduced (noise) when reading out of device. Effects all pixel values uniformly. • Dark Current Thermal noise that accumulates with image read out time. CIPS CCD has a 17 sec readout time, the dark current accumulates over rows. For example: First row read out has less dark current than the last row read out. Reported as electrons/second • Offset (set by electronics) Signal readout from CCD when not exposed to light. Accommodates temporal shifts in electronics, temperature stability and read noise. Avoids negative readout. • Photon Transfer Checks the full well, offset, gain, linearity of the CCD.

  18. CCD Acceptance Test • Each CCD is 2048 X 2048 pixels. Only • 1360 x 1360 pixels are used. • Dark images are used to characterize the CCDs. CCD 01 in Camera 0 • High Quality CCDs! • Typical characteristics: • Hot Pixels: < 0.07% • Read Noise: ~38 Electrons • Offset: ~90DN • Dark Current: ~0.1 DN/sec or 3.2 e¯/sec Integration Period (s) I&T calibration: Built up instrument Read Noise: ~ 45 Electrons Data Number (DN)

  19. 1447 pixels Camera Field of View • Field of View: • ~44º square for all cameras • Requirement: • Minimum of 44º square 44º = 1426 Pixels

  20. Linearity Linearity measured using the integrating sphere. Integration period incremented until saturation achieved. • Camera Linearity: • Linear ~ 3x103 DN • Completely nonlinear by 104 DN • Requirement: • Measure linearity to 95% full well

  21. Camera Distortion Camera Distortion Measure: Took image of grid in clean room Positioned 10 feet away to fill the 44º FOV Looked at linearity of lines across FOV Requirement: Measure to 1% over the field

  22. Camera Polarization • Linear polarization: • Measured both Perp and Para response using a star source and Glan-Taylor linear polarizer. • Response measured at 21 discrete points on the detector as displayed below. • Polarization: • Max 3% in Corners • Accuracy ~ 1% • Polarization effects are negligible • Requirement: • Less than 10% • 5% Accuracy Percent Polarization

  23. Camera Composite MY SUN MX PX PY

  24. UV Bandpass Ultraviolet Bandpass: 265nm ± 10nm In-band Transmission: 30% Measured Filter Transmission Wavelength (nm)

  25. Near Field Off Axis Response Near Field Off Axis Response Declines ~ 103 in 2 Degrees

  26. Radiometric Calibration Radiometric sensitivity is measured using a NIST-traceable 1-KW quartz-halogen standard lamp and a reflectance screen

  27. Illuminated Screen+Room Blocked Screen Difference Radiometric Calibration Measurement sequence repeated 20 Times at 4 high voltages Signal ~ exponential function of HV SNR varies by ~ 10% for HV> 700 volts

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