1. VI-5475(SamCalValNotes) 1 SAM (Sun and Aureole Measurement) Calibration Prepared for MODIS/VIIRS Science Team Meeting Dennis Villanucci, Andrew LePage John DeVore, A.T. Stair January 2010 Please open in “Notes” mode to see the notes.

2. VI-5475(SamCalValNotes) 2 1. Introduction SAM radiance measurements - Solar disk and aureole profiles  At 670 +/- 5 nm - Lab calibration NIST traceable - Field verification using AERONET for low ODs - Radiometric accuracy:  Disk radiance <1%, if OD<~0.6  Disk radiance <~10%, otherwise  Aureole radiance ~15% - Aureole profile precision (gradient):  Pixel-to-Pixel Stnd Dev <0.5%

3. VI-5475(SamCalValNotes) 3 2. SAM Lab Calibration NIST Standard Practice ParameterSolar Disk Camera Aureole Camera Multiple Exposures: Duration Relative to 40 ms standard Radiometric (NIST Traceable Sphere (Absolute: 2%) Absolute: <1% for ODs <~0.6 (AERONET ref); Otherwise <~10% Absolute: ~15% Flat-FieldNot NeededSee Panel 4 Linearity (Radiance) See Panel 5 Temperature Drift -6ºC to 44ºCNot Needed Internal Scattering Not NeededEnd-to-end, optics in place Neutral Density Filter Independent Measurement Not Applicable Pixel Scale (deg/pixel) Lab Measurement

4. VI-5475(SamCalValNotes) 4 3. SAM/AERONET Radiance Statistics RMS difference < 0.7% (~1000 values)

5. VI-5475(SamCalValNotes) 5 4. Flat Fielding (Aureole Camera)

6. VI-5475(SamCalValNotes) 6 5. Linearity (Typical Camera)

7. VI-5475(SamCalValNotes) 7 6. Aureole FPA Trace Definitions

8. VI-5475(SamCalValNotes) 8 7. Typical Uniform Cloud Data Traces Demonstrates precision of profile

9. VI-5475(SamCalValNotes) 9 8. Radial Average, Std Dev of Traces Demonstrates precision of profile

10. VI-5475(SamCalValNotes) 10 9. Non-uniform Cloud Example Cloud non-unformity is detectable

11. VI-5475(SamCalValNotes) 11 10. Moderately Thick Cloud Example Demonstrates accuracy (2 cameras) and precision of profile (gradient)

12. VI-5475(SamCalValNotes) 12 11. Field Calibration Verification For absolute radiometric calibration of cameras; verified for solar disk radiance with thousands of measurements next to AERONET sensors For flat fielding of aureole pixel-to-pixel response, e.g. “gradient” correction; verified with hundreds of measurements of uniform clouds

13. VI-5475(SamCalValNotes) 13 SAM-AERONET Comparison QuantityAERONETSAM ScattererAerosols Clouds (and aerosols) Size range (radius) ~ 0.1 – ~ 1  m~ 2.5 – ~ 25  m OD range (high precision) 0 to ~ 1 0 to ~ 5 (ice) 0 to ~ 10 (water) Minimum aureole angle from disk edge ~ 2.25º~ 0.25º Measurement sampling ~ 10 min (typical) ~ 12 sec (adjustable) Field of View or Regard ~ 120º (Scan FOR) +/- ~ 8º (FOV) and ~ 6º to 50º Pixel IFOV1.2º 0.015º (1024 x 1280) OD measurement accuracy (absolute) 0.01 to 0.02< ~ 0.03 OD measurement precision (relative) < 0.005

14. VI-5475(SamCalValNotes) 14 SAM Applications Climate (cloud) monitoring Cloud physics research Satellite algorithm cal/val Circumsolar radiation Dennis Villanucci 781-272-1220 villa@visidyne.com Andrew LePage 781-272-1220 lepage@visidyne.com Contacts: