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NASA Report to the 10 th Meeting of the GSICS Executive Panel. James J. Butler NASA Goddard Space Flight Center Code 614.4 Greenbelt, MD 20771 USA Phone: 301-614-5942 E-mail: James.J.Butler@nasa.gov Global Space-based Inter-Calibration System 10 th Session of the Executive Panel
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NASA Report to the 10th Meeting of the GSICS Executive Panel James J. Butler NASA Goddard Space Flight Center Code 614.4 Greenbelt, MD 20771 USA Phone: 301-614-5942 E-mail: James.J.Butler@nasa.gov Global Space-based Inter-Calibration System 10th Session of the Executive Panel World Meteorological Organization Geneva, Switzerland June 6-8, 2011
Acknowledgements • The following colleagues have directly contributed to this presentation: • Jack Xiong-NASA GSFC • Dave Doelling, Dave Young, and Bruce Wielicki-NASA LaRC • Dave Tobin-U of Wisconsin • Denis Elliot-NASA JPL
Agenda • Instrument/Mission Status: • MODIS • AIRS • CLARREO • Intercalibration Activities: • MODIS/GOES by NASA Langley • MODIS/AVHRR by NASA Goddard • AIRS/IASI by NASA Jet Propulsion Laboratory • AIRS/IASI; AIRS/GEO; AIRS/MODIS; & IASI/MODIS by the University of Wisconsin
MODIS Instrument Status • Both Terra and Aqua MODIS continue to operate normally • ΔT’s of instrument and warm FPA < 3.5K for MODIS Terra (11+ years) and <2K for Aqua MODIS (9+ years) • Gradual decrease in MODIS Aqua cooler margin has led to ≤0.03K orbit-to-orbit and seasonal variation in cold FPA T. No negative impact on data products. • On-board bb calibrators are stable. MODIS Terra SD continues to degrade with door open but is accurately monitored. • Calibration status • Radiometric • MODIS Terra: 45 noisy detectors (35 at launch) and no inoperable detectors • MODIS Aqua: 6 noisy detectors (3 at launch) and 15 inoperable detectors (13 in 1640nm band) • Spectral • Center λ Δ’s < 0.5 and 1.0 nm for most bands • Spatial • On-orbit BBR stable for MODIS Terra and Aqua • Large BBR offsets in MODIS Aqua between cold and warm FPA band pairs known since pre-launch • Excellent geolocation accuracy and stability • MODIS Terra: currently 43m along track and 44m along scan • MODIS Aqua: currently 47m along track and 45m along scan
MODIS Future Instrument Efforts • Monitoring changes in visible spectral band/detector responsivity • Mirror side, λ, polarization, and AOI dependent • Largest impacts for 412, 443, and 469nm bands • Monitoring BRDF degradation of MODIS Terra solar diffuser • Monitoring MODIS Aqua BBR product impact from 858 and 2130nm bands • Monitoring MODIS Terra TEB calibration quality over cold targets • Ensuring continued calibration consistency between MODIS Terra and Aqua by accounting for scene dependent offsets and trends Newly proposed collection 6 look-up tables will address many of these issues
MODIS L1B Process/Reprocessing Status (Collections) • Terra MODIS First Light on February 24, 2000 • C2 data processing started in March, 2000 • C3 reprocessing started in May 2001 • C4 reprocessing started in January 2003 • C5 reprocessing started in March, 2005 • C6 reprocessing to be started in Fall 2011 • Aqua MODIS First Light on June 24, 2002 • C3 data processing started in June 2002 • C4 reprocessing started in November 2002 • C5 reprocessing started in July 2005 • C6 reprocessing to be started in Fall 2011 A consistent set of LUTs is developed for each reprocessing
MODIS Code and LUT Changes in L1B C6 • Response versus Scan Angle (RVS) • New algorithm (added EV long-term trending; used a quartic function for RVS instead of a quadratic one in C5 • Changes in code and LUT • L1B Uncertainty Index • New algorithm (updated with on-orbit performance parameters) • Changes in code and LUT • Inoperable Detector Output • No longer interpolating the values of inoperable detectors from adjacent good detectors • Changes in code • Noisy/Inoperable Detector Flag • Sub-frame index added • Changes in code and LUT
AIRS Status • The Aqua spacecraft and the AIRS instrument are both in excellent health • A few channels (about 6%) have degraded noise performance due to radiation dosage over the mission—but all are still functional • The upcoming V6 release of the AIRS science software • Leaves radiometric calibration unchanged • Improves spectral calibration • New L1C software will be available that can • clean spectra (by replacing dead or noisy channels and by filling in the small inter-module gaps) • resample spectra to a fixed frequency grid
CLARREO Status • Background history • November 2010: successful Mission Concept Review (MCR), preparation for Phase A • January 2011: Science Definition Team (SDT) selected • February 2011: FY12 budget cut impact to proposed climate initiative • Directed not to proceed with CLARREO Phase A and mission procurement funding deleted from FY12 to FY15 • Directed to develop extended pre-Phase A plan for FY12 to FY16. Plan delivered to NASA HQ focusing on science and risk reduction. • According to the NRC, CLARREO science objectives are still a high priority for Earth Science. Improving remote sensing accuracy is a central goal of CEOS, GCOS, and GSICS. • CLARREO SDT goal to deliver on proposed research and continue to publish in the peer-reviewed literature. • Risk reduction for future benchmark radiance measuring missions • Extend the climate benchmark science: OSSEs, fingerprinting, intercalibration • International partnerships are more important than ever.
First CLARREO SDT MeetingMay 17-19, 2011 Hampton, VA Investigating Alternative Approaches: Shortwave Sampling Error From ISS and IRIDIUM IRIDIUM ISS • Research progress highlighted at first face-to-face meeting of the CLARREO Science Definition Team (officially selected in January 2011) • CLARREO science plan developed for Extended Pre-Phase A • Members presented novel findings on climate benchmarking and reference intercalibration approaches, including proposed research for FY’12. • Opportunities identified for collaboration and integration of studies • Studies identified to assist the development of alternative methods of achieving the CLARREO science goals. • Team Members • NASA LaRC, GSFC, HQ, JPL • Imperial College (UK) • University of California – Berkeley • Harvard University • University of Michigan • University of Colorado / LASP • University of Wisconsin – Madison • University of Miami • UMBC • Also attending: NIST, NOAA
MODIS/GOES comparisons: NASA Langley • GSICS GPRC are finalizing GEO visible calibration methods • NASA is the lead on Deep Convective Cloud (DCC) and ray-matching calibration techniques • DCC’s are bright, cold, stable, tropopause level, nearly isotropic targets near the equator and observed by all LEO and GEO satellites • NASA to write an ATBD on DCC calibration in June 2011 and host a web meeting to implement DCC calibration in October 2011 • NASA also recommended that Aqua-MODIS be used as the reference sensor, since it is better characterized and more stable than Terra-MODIS. • Presented both in a web meeting in December 2010 and at the Korea meeting • Aqua-MODIS is easily traceable to NPP VIIRS and follow on missions • NASA presented GEO DCC and GEO/MODIS ray-matching techniques at the Korea meeting • NASA also presented the absolute calibration and stability uncertainty of the Terra and Aqua MODIS instruments
NASA DCC calibration development for GSICS 1.24µm 0.47µm 0.65µm • The NASA DCC baseline calibration model • uses all the DCC indentified pixel level radiances normalized by the CERES DCC BRDF model used to convert radiance to overhead Sun • Validated that Aqua-MODIS is stable within 0.5%/decade for bands < 1µm • The method uncertainty is <2% for GEO and LEO maintained orbits • DCC targets have a 1% inter-annual and seasonal variability for wavelengths < 1µm • Uses SCIAMACHY hyper-spectral DCC radiances to account for band differences using Aqua-MODIS DCC as a reference 0.1%/decade 0.8%/decade 0.1-0.5%/decade
NASA DCC calibration development for GSICS • NASA improving baseline model • Incorporate multi IR DCC temperature thresholds (190-210°K) to take into account the 5% DCC radiance dependency to increase usable DCC population and spatial sampling • Normalize DCC radiance 5% spatial variability especially between land and ocean to allow absolute calibration within GEO sectors • Incorporate band specific BDRFs stratified by T threshold • Validate using Ray-matching and desert calibration Aqua 650nm 200-205K 195-200K 190-195K <190K
Current MODIS Calibration Inter-comparison Studies: NASA GSFC • MODIS and AVHRR Calibration Inter-comparison • AVHRR (starting from N15) and MODIS (Terra and Aqua) • VIS/NIR/SWIR channels • SNO approach • Collaborated with C. Cao (NOAA) • Calibration Inter-comparison over CEOS Endorsed Test Sites • MODIS, AVHRR, ETM+, and Hyperion • Reflective solar spectral bands/channels • Dome C, Libya, and other desert sites (http://calval.cr.usgs.gov/sites_catalog_ceos_sites.php) • Collaborated with C. Cao (NOAA) and G. Chander (USGS) • MODIS, AIRS, and IASI Calibration Inter-comparisons • Thermal emissive bands/channels • SNO approach • Collaborated with C. Moeller (UW) and J. Qu (GMU)
Current Calibration Inter-comparison Studies • Characterization of Spectral, Spatial, and Temporal Differences • MODIS, ETM+, Hyperion, SCIAMACHY • Characterization of site spatial uniformity and temporal stability • Calibration impact due to spectral differences for different surface types and atmospheric conditions • Collaborated with C. Lukashin (NASA/LaRC) and G. Chander (USGS) • Other Activities • Lunar observations (MODIS, SeaWiFS, Hyperion, VIRS lunar observations, ROLO model) • DCC (led by D. Doelling)
AIRS/IASI comparisons: NASA JPL • AIRS/IASI window channel comparison • The mean of AIRS - IASI is less than 50mK • They both differ from ECMWF in the same way, both on average and seasonally
AIRS/IASI comparisons: NASA JPL • AIRS and IASI (band 1 and 2) Obs-Calc (Strow) • AIRS and IASI show the same (obs-calc) bias in many channels. This indicates an error in ECMWF • For some channels the AIRS (obs-calc) is up to 300 mK larger than for IASI. This is where there is room for improvement.
AIRS/IASI comparisons: U. of Wisconsin • “Simultaneous” “Nadir” Overpasses of AIRS and IASI • SNOs based on the intersections of nadir ground tracks of METOP-A and Aqua (i.e. exact SNO locations) • IASI and AIRS FOV selections for each SNO: • Time window: +/- 20 min from SNO time • Spatial window: 60 km from Nadir track intersection point to center of IASI/AIRS FOVs • Resulting in: • ~45 AIRS FOVs, ~16 IASI FOVs per SNO • ~32 SNOs every ~3 days (16 North, 16 South) • 8102 SNOs in this study, covering May 2007 to Nov 2009 Time series of monthly means (1460-1527 cm-1) AIRS - IASI (K) Mean ΔT = 150mK Slope is 0.9 +/- 5.6 (1 sigma) mK/year
AIRS/GEO comparisons: U. of Wisconsin • Collocation in time and space. • Within 30 minutes at geostationary subpoint (GSNO – Geostationary Simultaneous Nadir Observation) • Low Satellite View Angles (< 14) • Spatial smoothing • 100km “running average” mitigates the negative effects of poor spatial and temporal collocation, poor navigation, and spatial resolution differences. • Average radiances, not temperatures. • Compare a common area around the GEO sub-point, not “pixel to pixel” comparisons • “Convolve” AIRS Radiance spectra with GEO Spectral Response Function. • Compare mean scene brightness temperatures (converted from mean scene radiances). 3.9 m +0.5 11 m +0.5 MET-8 FY-2C MET-9 MTSAT GOES-10 GOES-11 GOES-12 MET-8 FY-2C MET-9 MTSAT GOES-10 GOES-11 GOES-12 Most GEO imagers are calibrated within a 1K accuracy spec. However, accuracy for climate is much tighter (~0.1K) and intercal with AIRS can allow retrospective changes to operational calibration to approach those standards.
AIRS/MODIS comparisons: U. of Wisconsin 01-Feb-2003 01-Feb-2003 • For several bands, global mean AIRS-MODIS differences are on the order for a few hundredths of a K over the past 5 years • High spectral resolution provided by AIRS is being used to assess the calibration of broadband sensors MODIS 13.9 μm band 01-Aug-2003 01-Aug-2003 MODIS 13.9 μm band With 0.8 cm-1 SRF shift
IASI/MODIS comparisons: U. of Wisconsin Mean Differences for each band: • 2009 SNOs of IASI with Terra MODIS and Aqua MODIS
Summary • Both MODIS instruments, AIRS, and the Terra and Aqua satellites are in excellent health • MODIS and AIRS attention to on-orbit calibration and resulting high data quality ensure their status as reference instruments for LEO and GEO instrument comparisons • The active CLARREO SDT continues its work to reduce risk for future radiance measuring missions and to advance climate benchmark science • Continued work and growing interest in LEO/GEO instrument intercomparisons within NASA and US research universities • Looking forward to extending instrument intercomparison activities to the VIIRS and CrIS instruments on NPP • Launch date: October 25, 2011 (141 days from 6/6/11)