1. 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 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. Page 3 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 Visible/Infrared Imager Radiometer Suite (VIIRS)

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

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

6. 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 On-orbit Operation and Calibration

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 o SC roll maneuvers –Observed through SV port o Sector rotation (data in EV sector – more frames than SV sector) 7

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

9. RSB Lunar Calibration Integrated lunar irradiance (or radiance) –B: Band; M: HAM side; G: Gain stage; d: Detector; s: Sub-frame –dn: Background subtracted response –c 0, c 1, and c 2 : calibration coefficients Relative lunar F-factor –Lunar model (ROLO) predication provided by Tom Stone (USGS) Multiple scans of I1 lunar images (Jan 4, 2012 ) Page 9 SD F-factor

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

12. Changes in Spectral Band Response 12 Little change for HAM side and AOI dependence Large changes in NIR/SWIR response Noticeable SD and Lunar calibration difference in VIS (M1-M3) Lunar gains normalized to 4/2/2012 0. , 0.44 , 0.49  Curves: SD Cal Symbols: Lunar Cal

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

14. Yaw Maneuvers: Results and Applications 14 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 Ratio of Pre-launch LUT to Yaw Results (SD screen transmission x BRF) No PL results SDSM Sun view screen transmission: Fine structure

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

16. DNB: Many New Applications 16 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. VIIRS DNB radiance time series before and after the power outage (6/29) shows that most of the power was restored in three days. VIIRS DNB of the Washington/Baltimore area on June 26 th (top)and June 30 th. The suburbs west of DC and Baltimore, in particular show dark areas. ROI: (101 by 71 pixels) ~ 64 km × 64 km Blue: mostly clear sky Red: Cloudy 06/30 06/23 06/29 07/02 07/06 From GSICS presentation (Cao and Xiong)

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

18. Summary 18 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.