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AgCam Calibration Test Results

AgCam Calibration Test Results. Xiaodong Zhang. Calibration Tests. Spectral Radiometric Flat Field Focus Thermal Effects First light. NIR Camera. Red Camera. Spectral Calibration Configuration. MONOCHROMETER. AgCam. LIGHT SOURCES. 100W Tungsten Halogen bulb. CHOPPER.

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AgCam Calibration Test Results

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  1. AgCam Calibration Test Results Xiaodong Zhang

  2. Calibration Tests • Spectral • Radiometric • Flat Field • Focus • Thermal Effects • First light

  3. NIR Camera Red Camera Spectral Calibration Configuration MONOCHROMETER AgCam LIGHT SOURCES 100W Tungsten Halogen bulb CHOPPER FILTER WHEEL M3 M2 M1 M4 PDC Spectral Calibration Collimator

  4. Spectral Calibration – Quick Run • Approximately determine the spectral band pass of the AgCam system • Every 5 nm from 330 nm to 1200 nm • 7 nm FWHM (bandwidth) • Integration time 400 s for both cameras • Visually check if signal > noise

  5. Quick Run – Results • Spectral response 600 nm – 700 nm for the red camera and 780 nm – 900 nm for the NIR camera • The responses of the AgCam optical system are below noise level for photons at wavelengths below 500 nm and above 950 nm

  6. Spectral Calibration – Slow Run • Every 2 nm from 550 – 750 nm for the Red and from 750 – 950 nm for the NIR • Integration time 300 s for the Red and 400 s for the NIR • 5 incident angles (far left, mid left, nadir, mid right, far right) • Reference spectra taken before and after the run for each angle • 50 seconds per wavelength x 200 wavelengths x 2 cameras x 5 angles = very very very slow!!!

  7. Spectral Calibration – Preliminary Results

  8. CCD NIR Beamsplitter CCD Red Spectral Calibration – preliminary conclusions • Meets the requirement • Different spectral responses for different incident angles (true for almost all flat filters, because travel distance of photons across the flat filter varies with incident angles) • Non-symmetrical w.r.t. the optical axis (because long axis of the beam-splitter aligns with the CCD array

  9. Spectral Calibration – to do • Correct for spectral intensity of the incident light source

  10. Radiometric Calibration • Integrating sphere with 30” opening and 12 bulbs • Due to saturation, only 6 bulbs were used

  11. Radiometric Calibration – Preliminary results and conclusions 23 8

  12. CCD center Vignett effect, which need s to be corrrected Radiometric Calibration – Preliminary results and conclusions Lens center CCD array center

  13. Radiometric Calibration – to do • Quantify the radiometric response in terms of radiance per digital count, using • Calibrated radiometric outputs of the integrating sphere • Spectral responses of the AgCam system • Pixel by pixel

  14. Thermal Effect • Temperature-controllable chamber • Integrating hemisphere with 20” opening • T = 18C (site room temp), 30°C (normal temp at ISS), and 35°C (hot day at ISS)

  15. Thermal Effects – preliminary results • The red camera is hotter than the NIR • The camera temperatures are always ~10°C higher than ambient • The camera temperatures increased rapidly during the 1st hour of operation (At the ambient temperature of 35C, they reached ~46C in about 50 minutes ) • At 18°C, the camera temperatures increased to 32°C during 4 hours.

  16. Thermal Effects – Preliminary conclusions • Don’t not operate the camera more than 1 hour.

  17. Taking Pictures • AgCam mounted to 12” machine shop rotary indexing table • Battery-operated drill drove the table at ~1 deg/s rotation of the camera

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