Impact of Level 1 Radiometric Stability on Level 2 Products and - PowerPoint PPT Presentation

National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California Impact of Level 1 Radiometric Stability on Level 2 Products and Expectations for CrIS on NPOESS NASA Sounder Science Team Meeting T. Pagano, Evan Manning May 4, 2009 1

National Aeronautics and Space Administration Introduction Jet Propulsion Laboratory California Institute of Technology Pasadena, California • AIRS Team has high interest in CrIS for continuing AIRS measurements • Government and Industry teams actively working towards product development. Thanks for your hard work! • NASA to evaluate products from IPO and NOAA • Expect good performance overall with a few exceptions • This talk focuses on impact of low emissivity Internal Calibration Target (ICT) on Level 2 • Small impact (< 0.2K) instability to L2 products • Should be OK for process studies, may affect climate studies 2

National Aeronautics and AIRS, CrIS, and IASI have Similar Space Administration Jet Propulsion Laboratory Features California Institute of Technology Pasadena, California AIRS Aqua AIRS CrIS IASI Spectral Range (cm -1 ) 650-1140 650-1095 645-2760 1210-1610 1210-1750 CrIS 2170-2675 2155-2550 Spectral Resolution 0.625-2.5 (cm -1 ) 0.4-2.1 (Unapodized)* 0.35-0.5 NPOESS Spatial Resolution 14 km 14 km 12 km IFOV 3x3/1.1 ° 3x3/1.1 ° 2x2/1.1 ° Size 0.9 m 3 0.5 m 3 1.7 m 3 IASI Mass 177 kg 165 kg 236 kg Power 256 W 135 W 210 W Orbit Crossing 9:30 METOP Time 1:30 am/pm 1:30 am/pm am/pm *Note: Unapodized Resolution about 3 2X lower than Apodized

National Aeronautics and CrIS Internal Calibration Target Space Administration Jet Propulsion Laboratory (ICT) is Diffuse Cavity Design California Institute of Technology Pasadena, California Old ICT Environmental Model Used in SDR Algorithm Version 2.13 OMA Housing SSM Baffle SSM Baffle, OMA & Frame Housing & IFM IFM Beam Splitter Beam Splitter ICT Cavity Radiate Energy Into Central ( ) ICT Cavity ε BS σ Obscuration ( ) ε surf σ T BS 1.7º ( ) ε eff σ 8.8º T ICT 13.1º A Portion of that Energy Is Reflected 28.7º ( ) ε baffle σ Back to Interferometer T baffle ( ) ε OMA σ T OMA Half angles represent approximate view to external environment From ITT SDR Algorithm (version 2.17)l Updates.ppt 4

National Aeronautics and AIRS On-Board Calibrator Space Administration Jet Propulsion Laboratory Blackbody (OBC) is Wedge Design California Institute of Technology Pasadena, California • OBC Blackbody (OBC) • T = 307.9K • ε > 0.998 • T_precision = 0.01K AIRS Scan Geometry 5

National Aeronautics and Comparison of AIRS and CrIS on-board Space Administration Jet Propulsion Laboratory blackbody “Effective” Emissivities California Institute of Technology Pasadena, California 6

National Aeronautics and Space Administration Uncertainty on Emitted Radiance Treated as Jet Propulsion Laboratory “Effective” Temperature Uncertainty of Background California Institute of Technology Pasadena, California Observed Radiance is sum of Emitted and Reflected Components = ε + − ε L P ( 1 ) L obs ICT ICT BKG Variance on observed radiance from the ICT δ = ε δ + − δε + − ε δ 2 2 2 2 2 2 2 L P ( P L ) ( 1 ) L obs ICT ICT ICT BKG ICT ICT BKG Background is sum over contribution from all elements ∑ ∑ = ε ≡ ε L A P ( T ) A ' P ( T ) BKG i i i i i i i i Variance on background has three components: Area, emissivity and temperature 2 dP ( T ) ∑ ∑ ∑ 2 δ = δ ε + δ ε + ε δ 2 2 2 2 2 2 2 2 2 i L A ' P ( T ) ' A P ( T ) A ' T BKG i i i i i i i i i dT i i i Since it is impossible to differentiate between these, define “effective” temperature error to match observed stability in the laboratory 2 dP ( T ) δ = ε δ 2 2 2 BKG L T BKG _ obs BKG eff _ BKG dT 7

National Aeronautics and 5K Fluctuation in Baffle Temperature Space Administration Jet Propulsion Laboratory Calculated, 0.75K Uncertainty Claimed California Institute of Technology Pasadena, California Realistic Orbital Parameter Variations Results in 0.75 C Uncertainty in Predicted Average Baffle Temperature Knowledge Delta T Between ICT View of Baffle Average and Temperature Sensor Location 2 Beta 12 Hot, EOL Properties Beta 28 Hot, Scanning Mirror EOL Beta 28 Hot, Variable Erath IR Spacecraft Thermal Control Handbook (Case 5) Beta 28Hot, Scanning Mirror, 2-sigma average cold/hot variation (Case 3) 1 Delta Baffle Correction to be applied 0 -1 Delta T (C) -2 Variat ions from t he correct ion profile represent errors -3 -4 Correct ion t o be applied t o t he baffle t emperat ure -5 0 1000 2000 3000 4000 5000 6000 7000 Orbit Time (Second) From ITT SDR Algorithm (version 2.17)l Updates.ppt 8

National Aeronautics and Space Administration 5K “Effective” Background Temperature required to Jet Propulsion Laboratory match observed difference during TVAC testing? California Institute of Technology Pasadena, California CrIS Accuracy Spec CrIS Calculated (JPL). δ T eff_BKG = 5K CrIS Obs: Difference between observed radiance calculated using SDR algorithm and ECT radiance during Radiometric Confidence Test (Jordan memo) CrIS Reported: ICT Radiance Knowledge (Jordan memo) D. Jordan, L. Woody, D. Gregory, R. Hertel, R. Frain, L. Suwinski, CrIS FM1 Tech memo 8231508 – Radiometric Uncertainty and Long Term Radiometric Stability, December 17, 2008 9

National Aeronautics and Broken down and compared to AIRS Space Administration Jet Propulsion Laboratory with comparable uncertainty. California Institute of Technology Pasadena, California Table 1. Comparison of Temperatures, Emissivities and Uncertainties for CrIS and AIRS Parameter CrIS AIRS ICT Temp (K) 287 307.9 ICT Temp Uncty (K) 0.037 0.026 ICT Emis ~0.975 ~0.998 ICT Emis Uncty 0.01 0.004 Bkg Emis 0.95 1 Bkg Emis Uncty 0.05 0 Bkg Temp (K) 284 252.12 Bkg Temp Uncty (K) 5 5 10

National Aeronautics and Sanity check for uncertainty Space Administration Jet Propulsion Laboratory calculation about right California Institute of Technology Pasadena, California CrIS Reflected Energy CrIS ICT Residual (All terms) 10% of Reflected Energy 100% of AIRS Energy Assumed Uncorrected 11

National Aeronautics and Expect 50-200 mK Uncorrected Space Administration Jet Propulsion Laboratory Radiance from CrIS California Institute of Technology Pasadena, California CrIS. Only 5K Error Assumed in Error ( ) dP T δ = − ε δ BKG L ( 1 ) T obs _ BKG ICT eff _ BKG dT AIRS. All Reflected Energy Included in Error δ = − ε L ( 1 ) P ( T ) obs _ BKG OBC eff _ BKG 12

National Aeronautics and AIRS Radiometric Space Administration Jet Propulsion Laboratory Uncertainty Estimate at 265K California Institute of Technology Pasadena, California Based on Pre-Flight Calibration at 265K 0.07K (1 σ Average + 40 mK Other) 13

National Aeronautics and Space Administration Expect Orbital and Seasonal Jet Propulsion Laboratory Dependence to Residual California Institute of Technology Pasadena, California [ ] δ = δ π + φ + π + φ L ( t ) L cos( 2 f t ) cos( 2 f t ) obs _ BKG obs _ BKG _ max 1 1 2 2 δ = L Uncorrect ed Component of Reflected radiance off ICT obs _ BKG _ max = 1 / f 1 orbit , 1 year 1 , 2 φ = Minimum at equator night side, maximum at equator day side 1 φ = Minimum in winter, max in summer 2 14

National Aeronautics and Impact of Radiance Instability on Level 2 Space Administration Jet Propulsion Laboratory Product: Temperature at 100 mb California Institute of Technology Pasadena, California 15

National Aeronautics and Impact of Radiance Instability on Level 2 Space Administration Jet Propulsion Laboratory Product: Surface Air Temperature California Institute of Technology Pasadena, California 16

National Aeronautics and Space Administration Summary and Conclusions Jet Propulsion Laboratory California Institute of Technology Pasadena, California • Internal Calibration Target (ICT) Blackbody on CrIS on NPP does not meet emissivity specifications • View to external baffles will introduce reflected energy contribution to calibration radiance viewed by CrIS • Energy will modulate with instrument temperature • Correction algorithm will be applied. It’s a matter of how well this can be done. • Expect residuals on the order of 50-200 mK • May be OK for process studies, but may affect ability to trend products over time • Will impact Level 2 product temperatures with similar errors unless it can be tuned out using earth observations • Fix to ICT requested for FM2 • Again, Thanks to the CrIS Team for all their efforts. 17