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VIIRS Reflective Solar On-orbit Calibration and Performance Jack Xiong and Jim Butler Code 618.0, NASA/GSFC, Greenbelt,

VIIRS Reflective Solar On-orbit Calibration and Performance Jack Xiong and Jim Butler Code 618.0, NASA/GSFC, Greenbelt, MD 20771. CLARREO SDT Meeting, NASA LaRC , April 16-18, 2013. Contributors: Jon Fulbright, Ning Lei, Jeff McIntire, and Junqiang Sun

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VIIRS Reflective Solar On-orbit Calibration and Performance Jack Xiong and Jim Butler Code 618.0, NASA/GSFC, Greenbelt,

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  1. VIIRS Reflective Solar On-orbit Calibration and PerformanceJack Xiong and Jim ButlerCode 618.0, NASA/GSFC, Greenbelt, MD 20771 CLARREO SDT Meeting, NASA LaRC, April 16-18, 2013 Contributors: Jon Fulbright, Ning Lei, Jeff McIntire, and Junqiang Sun VIIRS Characterization Support Team (VCST)

  2. Outline • VIIRS and On-board Calibrators (OBC) • On-orbit Operation and Calibration • On-orbit Performance (reflective solar bands only) • Summary Page 2

  3. Visible/Infrared Imager Radiometer Suite (VIIRS) • Description • Purpose: Global observations of land, ocean, & atmosphere parameters at high temporal resolution (~ daily) • Predecessor Instruments: AVHRR, OLS, SeaWiFS, MODIS • Spectral range: 22 bands between 0.4 µm and 12.5 µm • Spatial resolution: 375 and 750 m • Swath Width: 3000 km • Key Features • MODIS-like on-board calibrators • 16 moderate (radiometric), 5 imaging, and 1 day/night bands • Dual gains (7 bands) • VIS/NIR, SMIR, and LWIR focal plane assemblies (FPA) • Pixel aggregations and bowtie deletion Page 3

  4. VIIRS and MODIS Spectral Bands 1 DNB 14 RSB (0.4-2.3 mm) Dual gains: M1-M4, M6, M7 M12 7 TEB Page 4

  5. VIIRS On-board Calibrators Blackbody Solar Diffuser Rotating Telescope Aft Optics and HAM MODIS heritage OBC Improved SD/SDSM system Solar Diffuser Stability Monitor Reflective Solar Bands Calibration Using SD and SDSM Page 5

  6. On-orbit Operation and Calibration • Key Events (operation/calibration activities) • Launch: 10/28/11 • Instrument turn-on: 11/8/11 • Nadir door open: 11/21/11 (first image from VIS/NIR) • RTA stow (4 times): 12/9/11 – 1/2/12 • Cryo-cooler door open: 1/18/12 (observations from all bands) • Roll maneuvers: started from 1/4/12 (nearly monthly, 12 since launch) • Yaw maneuvers; 2/15/12 – 2/16/12 (SD/SDSM screen transmission) • Pitch maneuvers: 2/20/12 (TEB response versus scan angle) • BB warm-up/cool-down: started from 2/6/12 (quarterly, 5 since launch) • Routine SD/SDSM calibration (RSB calibration) Page 6

  7. Reflective Solar Bands On-orbit Calibration • Solar Calibration • SD calibration performed each orbit (no SD door) • SDSM currently operated on a daily basis • Yaw maneuvers (performed at mission beginning) • Lunar Calibration • Regularly scheduled at nearly the same phase angle • SC roll maneuvers • Observed through SV port • Sector rotation (data in EV sector – more frames than SV sector) 7

  8. RSB Solar Calibration – SD/SDSM RSB Calibration F and H Factors • 1/F: Detector Gain; • H-Factor: SD Degradation The dn and dc are VIIRS and SDSM detector “corrected” responses Page 8

  9. RSB Lunar Calibration Multiple scans of I1 lunar images (Jan 4, 2012 ) • Integrated lunar irradiance (or radiance) • B: Band; M: HAM side; G: Gain stage; d: Detector; s: Sub-frame • dn: Background subtracted response • c0, c1, and c2: calibration coefficients • Relative lunar F-factor • Lunar model (ROLO) predication provided by Tom Stone (USGS) SD F-factor Page 9

  10. On-orbit Performance • SD Degradation • Similar to MODIS with much faster degradation rate • Changes in Spectral Band Response • Larger at NIR/SWIR (due to RTA mirrors contamination) • SNR performance (continue to meet the requirements) • Yaw Maneuvers • Changes in Relative Spectral Response (RSR) • Modulated RSR 10

  11. SD On-orbit Degradation VIIRS SD Degradation Trend (H-Factor) MODIS & VIIRS SD Degradation (as a function wavelength) S-NPP VIIRS: 1.5 Yr Aqua MODIS: 11 Yr Terra MODIS: 13 Yr* VIIRS has no SD door: large degradation in SD BRF * Terra MODIS SD door fixed at open since July 2003 11

  12. Changes in Spectral Band Response Curves: SD Cal Symbols: Lunar Cal Lunar gains normalized to 4/2/2012 0.41m, 0.44m, 0.49m Little change for HAM side and AOI dependence Large changes in NIR/SWIR response Noticeable SD and Lunar calibration difference in VIS (M1-M3) 12

  13. On-orbit SNR Performance Large degradation in M7/I2, M8, M9 Continue to meet the requirements (large pre-launch design/performance margins) SNR*: normalized to specified values; SNR*>1: performance better than specification 13

  14. Yaw Maneuvers: Results and Applications SDSM Sun view screen transmission: Fine structure Ratio of Pre-launch LUT to Yaw Results (SD screen transmission x BRF) SDSM Sun view screen transmission function derived from yaw maneuvers has been used in SDR calibration The LUT for SD screen transmission x BRF derived from yaw maneuvers has also been applied recently to SDR calibration No PL results 14

  15. Changes in Relative Spectral Response Mirror Degradation has impact on sensor relative spectral response and radiometric calibration quality l dependent optics degradation Modulated Sensor RSR Modulate RSR has recently applied to SDR Calibration and Data Production 15

  16. DNB: Many New Applications • The Day/Night Band has been used to detect a major power outage in the Washington, DC on the night of the Direcho storm on June 29, 2012. • An analysis of the data after the storm showed that most areas had power restored within 3 days. Blue: mostly clear sky Red: Cloudy ROI: (101 by 71 pixels) ~ 64 km × 64 km 07/06 06/29 07/02 06/23 06/30 VIIRS DNB of the Washington/Baltimore area on June 26th (top)and June 30th. The suburbs west of DC and Baltimore, in particular show dark areas. VIIRS DNB radiance time series before and after the power outage (6/29) shows that most of the power was restored in three days. From GSICS presentation (Cao and Xiong) 16

  17. Changes in Relative Spectral Response Impact of up to 5% DNB RSR Modulated RSR is currently used in SDR calibration and production 17

  18. Summary • VIIRS continues to operate and calibrate satisfactorily (as planned and expected) • On-orbit changes in sensor response are accurately tracked by the on-board calibrators (enabling frequent LUT updates) • Overall VIIRS on-orbit performance meets the design requirements (such as SNR) • Results derived from calibration maneuvers have been used to evaluate and improve sensor on-orbit calibration • The modulated RSR functions been developed and applied to sensor SDR calibration and data production. 18

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