AgCam Calibration Test Results

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AgCam Calibration Test Results

• Xiaodong Zhang

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Calibration Tests

• Spectral
• Radiometric
• Flat Field
• Focus
• Thermal Effects
• First light

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Spectral Calibration
Collimator
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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 gt noise

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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

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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!!!

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Spectral Calibration Preliminary Results
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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

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Spectral Calibration to do

• Correct for spectral intensity of the incident
  light source

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Radiometric Calibration

• Integrating sphere with 30 opening and 12 bulbs
• Due to saturation, only 6 bulbs were used

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Radiometric Calibration Preliminary results and
conclusions
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Radiometric Calibration Preliminary results and
conclusions
Lens center
CCD array center
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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

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Thermal Effect

• Temperature-controllable chamber
• Integrating hemisphere with 20 opening
• T 18?C (site room temp), 30C (normal temp at
  ISS), and 35C (hot day at ISS)

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Thermal Effects preliminary results

• The red camera is hotter than the NIR
• The camera temperatures are always 10C 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 18C, the camera temperatures increased to
  32C during 4 hours.

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Thermal Effects Preliminary conclusions

• Dont not operate the camera more than 1 hour.

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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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