NASA Report to the 10th Meeting of the GSICS Executive Panel

James J. ButlerNASA Goddard Space Flight Center

Code 614.4Greenbelt, MD 20771 USA

Phone: 301-614-5942E-mail: James.J.Butler@nasa.gov

Global Space-based Inter-Calibration System10th Session of the Executive PanelWorld 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.

• 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

First CLARREO SDT MeetingMay 17-19, 2011 Hampton, VA

ISS IRIDIUM

Investigating Alternative Approaches: Shortwave Sampling Error From ISS and IRIDIUM

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

• 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

0.47µm 0.65µm 1.24µm

0.1%/decade 0.1-0.5%/decade 0.8%/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

200-205KAqua 650nm 195-200K

190-195K <190K

• 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 MODIS Calibration Inter-comparison Studies: NASA GSFC

• 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)

Current Calibration Inter-comparison Studies

• 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/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

AIRS

- IA

SI (K

)

Time series of monthly means (1460-1527 cm-1)

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).

+0.5

+0.5

3.9 m

GOES-10

GOES-11

GOES-12

MET-8MET-9

MTSAT

FY-2C

GOES-10

GOES-11

GOES-12

MET-8MET-9

MTSAT

FY-2C

11 m

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

• 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

01-Feb-2003 01-Aug-2003

01-Feb-2003 01-Aug-2003

MODIS 13.9 μm band

MODIS 13.9 μm bandWith 0.8 cm-1 SRF shift

IASI/MODIS comparisons: U. of Wisconsin

• 2009 SNOs of IASI with Terra MODIS and Aqua MODIS

Mean Differences for each band:

Band No. Center λ (μm)

20 3.785

21 3.960

22 3.960

23 4.056

24 4.472

25 4.545

27 6.752

28 7.334

29 8.518

30 9.737

31 11.017

32 12.032

33 13.359

34 13.675

35 13.907

36 14.192

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)