1. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 The NPP/NPOESS VIIRS SST Mission Peter J. Minnett & Robert H. Evans Rosenstiel School of Marine & Atmospheric Science University of Miami, FL Sid Jackson & Justin Diehl Northrop Grumman Space Technology Redondo Beach, CA

2. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 Outline Background VIIRS – Visible/Infrared Imager/Radiometer Suite SST retrievals Cal/Val approach All information is from publicly accessible sources.

3. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 What is the NPOESS Mission? Provide a national, operational, polar- orbiting environmental capability Achieve National Performance Review savings by converging DoD and NOAA polar satellite programs Incorporate new technologies from NASA and others Incorporate, where appropriate, International Cooperation (EUMETSAT) Local Equatorial Crossing Time 0530 1330 0930 METOP NPOESS

4. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 What is NPP? NPP is a joint program of NASA and the Integrated Program Office (IPO), the tri-agency activity that is responsible for NPOESS NPP is a “bridging mission” that provides for the continuation of measurement series initiated with EOS Terra & Aqua for NASA’s global change research – Climate change – Global carbon cycle – Global water cycle NPP provides risk reduction for the National Polar-Orbiting Operational Environmental Satellite System (NPOESS) which will continue these measurements into the indefinite future

5. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 VIIRS The Visible/Infrared Imager/Radiometer Suite collects visible/infrared imagery and radiometric data. Applications include atmospheric clouds, earth radiation budget, clear-air land/water surfaces, sea surface temperature, ocean color, and low light visible imagery. Primary instrument for satisfying 22 Environmental Data Records (EDRs) and 2 Key Performance Parameters (KPPs). Multiple VIS and IR channels between 0.3 and 14 μ m Imagery Spatial Resolution: ~400m @ NADIR / 800m @ EOS

6. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 Major VIIRS Objectives High resolution imagery with near constant resolution across scan Increased accuracy/resolution of sea surface measurements Disaster monitoring (Volcanic ash, Suspended Matter, Floods, Fires, …) Increased accuracy/resolution of aerosols and cloud properties Climate relevant accuracies

7. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 VIIRS Components Spectral Bands: – Visible/Near IR: 9 plus Day/Night Band – Mid-Wave IR: 8 – Long-Wave IR: 4 Imaging Optics: 18.4 cm Aperture, 114 cm Focal Length Band-to-Band Registration (All Bands, Entire Scan) > 80% per Axis Orbital Average Power: 240 W Mass: 275 Kg

8. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 VIIRS innovations Rotating telescope primary optics Two-sided “Half-Angle Mirror” (HAM) Multiple detectors (16) per spectral band On-board pixel aggregation

9. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009

10. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009

11. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 Risk reduction by using components derived from heritage instruments: Rotating Telescope from SeaWiFS Black-body from MODIS Multiple Focal Plane Arrays and Multiple Detector Assemblies from MODIS Risk reduction by using components derived from heritage instruments: Rotating Telescope from SeaWiFS Black-body from MODIS Multiple Focal Plane Arrays and Multiple Detector Assemblies from MODIS

12. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009

13. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 Telescope / HAM Synchronization Angles Note – successive rotations of the Rotating Telescope Assembly use alternate sides of the HAM

14. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 VIIRS Bands Spectral bands are a subset of MODIS bands

15. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 VIIRS SST Bands GSD = Ground sampling distance Spectral bands are a subset of MODIS bands

16. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 Pixel Aggregation Each “pixel” has three rectangular detectors in the scan direction Detectors have a 3x1 aspect ratio These are aggregated in threes, then twos, then no aggregation, across the scan. This is an attempt to provide near uniform spatial resolution across the swath.

17. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009

18. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 VIIRS SST Uncertainty Predictions The sources of error the VIIRS SSTs fall into two categories: – associated with imperfections in the instrument – arise from imperfections in the atmospheric correction algorithm. The instrumental effects include: – The inherent noise in the detectors, the Noise Equivalent Temperature Difference (NEΔT) – Band-to-band registration (BBR) – Modulation Transfer Function (MTF) – Calibration errors, such as imperfections in the knowledge of the emissivity and surface temperature of the on-board black body target, and of stray radiation falling on the detectors.

19. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 VIIRS Synthetic Data VIIRS Synthetic Data for SST accuracy prediction based on: – MODIS Match-Up Data Bases – MODIS radiance granules adjusted to match VIIRS performance – AVHRR scenes adjusted to match VIIRS performance – RTE simulations using a global snapshot of surface temperature at 2.5 o x 2.5 o resolution supplied by NCEP, with matching atmospheric profiles. There are 26,590 samples in the simulation. – RTE simulations using a set of 299 global observations of skin SST with radiosonde atmospheric profiles and coincident satellite passes plus 6 standard atmosphere profiles and surface temperatures

20. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 Band-to-band mis-registration error Baseline daytime VIIRS split window algorithm. Based on a study of AVHRR test scenes. The misregistration has significant impact on the retrieval precision when the measurement noise is small.

21. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 VIIRS 11 μ m Brightness Temperature Uncertainties

22. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 VIIRS SST Band Instrumental Uncertainties

23. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 SST retrievals Primary KPP SST is a skin SST. Additional Environmental Data Record is a bulk SST, and the plan is to use a model to derive the bulk SST from the skin SST.

24. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 VIIRS Daytime SST Retrieval Equation where a 0, a 1, a 2, a 3 are coefficients derived by regression analysis, T 11 is the measured brightness temperature at 11 µm (VIIRS band M15), T 12 is the measured brightness temperature at 12 µm (VIIRS band M16), RSST is a modeled, first guess SST, and z is the sensor zenith angle. – Two set of monthly coefficients are determined for T 11 – T 12 ≤ 0.8K (temperate to polar) T 11 – T 12 > 0.8K (equatorial to temperate) In alignment with heritage sensors.

25. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 VIIRS Night-time SST Retrieval Equation where a 0, a 1, a 2, a 3 are coefficients derived by regression analysis (different from daytime algorithm), T 3.7 is the measured brightness temperature at 3.7 µm (VIIRS band M12), T 12 is the measured brightness temperature at 12 µm (VIIRS band M16), RSST is a modeled, first guess SST, and z is the sensor zenith angle. Diverges from heritage sensors.

26. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 SST Atmospheric Correction Algorithm Uncertainties

27. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 SST retrieval errors at Nadir

28. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 SST retrieval errors at Edge of Swath

29. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 SST validation using ship-board radiometers Radiometers installed on ships for the validation of MODIS skin SSTs. Top: the ISAR mounted above the bridge of the M/V Jingu Maru. Middle: CIRIMS mounted above the bridge of the NOAA S Ronald H. Brown. Bottom: M-AERI mounted on an upper deck of the Explorer of the Seas.

30. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 SST Validation Using Buoys

31. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 Current status NPP VIIRS is currently undergoing thermal-vacuum testing. Thus far no critical problems. Barring unexpected “features” in the data stream, VIIRS could be a good infrared radiometer. SST retrievals are expected to be on a par with heritage instruments (but probably will not match MODIS). Use of ship-based radiometers for SST validation with traceability to National Standards will mean VIIRS could contribute to SST ECV CDR.

32. GHRSST –X Science Team Meeting Santa Rosa, California, USA 1-5 June 2009 Useful references http://www.ipo.noaa.gov/ http://npoess.noaa.gov/index.php http://cimss.ssec.wisc.edu/itwg/itsc/itsc13/session10/Puschell %20VIIRS%20Sensor%20Performance%20ITSC%20FINAL. pdf Lee, T. F., S. D. Miller, C. Schueler, and S. Miller, 2006: NASA MODIS Previews NPOESS VIIRS Capabilities. Weather and Forecasting, 21, 649-655.