National Aeronautics and Space Administration Lessons Learned from EO-1 Calibration Activities Advanced Land Imager (ALI) band misregistration impact on spectral indices Radiometric stability of lunar test sites based on Hyperion observations a,b c a Ungar, Stephen , Ong, Lawrence , and Thome, Kurtis a NASA/Goddard Space Flight Center (GSFC), Greenbelt, MD 20771, USA b Universities Space Research Assoc. (USRA), Columbia, MD 21044, USA c Science Systems and Applications, Inc. (SSAI), Lanham, MD 20706, USA IGARSS 2014 Quebec, Canada July 16,2014 Lets cut to the chase and get directlyCONCLUSIONS! to the bottom line • Push broom observing systems of the ALI variety can not produce inherently (band-to band) co-aligned measurements. This is not a design flaw, but rather a “feature” designed to produce higher SNR. • This “”feature” does not necessarily hamper uses of the data in a variety of applications. However, it does introduce significant uncertainty in determining vegetation indices. • The moon serves as a solar diffuser monitor for several orbiting missions. The EO-1 CalVal Team, in collaboration with EO-1 Operations, is refining strategies to use specific “vicarious calibration sites” on the lunar surface, enhancing use of orbiting imaging spectrometer missions to serve as transfer radiometers for other passive optical missions. Pushbroom Observing System Sensor Chip Array (SCA) “cartoon” Depiction Wavelength -Grids represent the detectors -Spots represent the IFOV centers -Colors represent the wavelengths Cross Track Sample (Pixel) Pushbroom Observing System Pushbroom systems come in two flavors Pushbroom Observing System Areas viewed simultaneously by each band Pushbroom Observing System Areas viewed simultaneously by each band Pushbroom Observing System Areas viewed simultaneously by each band Pushbroom Observing System Areas viewed sequentially by each band Pushbroom Observing System Areas viewed sequentially by each band Pushbroom Observing System Areas viewed sequentially by each band Pushbroom Observing System Areas viewed sequentially by each band Pushbroom Observing System Areas viewed sequentially by each band E S E AdjustingHow ALIAttitude Achieves and Frame Inherent Rate to EnsureBand Band-to-Band-to-Band Coregistration Co-registration • The ground sampling distance (GSD) is a function of the sub-satellite “ground” speed and detector sampling rate. • Pixel “size” is a function of the detector angular field of view (IFOV), integration time, range (distance) to target, and ground “velocity”. • EO-1’s strategy to ensure inherent band-to-band registration for the Advanced Land Imager (ALI) is to: – Align the ALI sensor chip array (SCA) with the ground velocity vector direction by yawing the spacecraft; – Adjust sampling rate, based on ground speed, such that an integral number (N) of GSD’s exactly equal the projected ground distance between simultaneously collected bands. Adjusted (ALI) Sampling Rate Fixed (L8/OLI) Sampling Rate ~236 frames/sec Adjusting Attitude and Frame Rate to Ensure Band-to-Band Co-registration Further Considerations • The EO-1 approach uses a fixed value of N which is based on maintaining a GSD equal to the nominal pixel size. However, any integer value of N ensures band-to- band co-registration. • Lowering the value on N leads to under-sampling and decrease in data volume, while increasing N results in oversampling, increased data volume, and possible reduction in SNR. Adjusting Frame Rate to Ensure Band-to-Band Co-registration 2 ROblateo ≡ EO −Earth1 orbital Approximation radius ' 2 2 RE cosθ + h ω ≈ ω + ωE R E ≡ mean Earth radius RE + h ω ' (R + h) h ≡ ΔR E + terrain altitude D = N E f θ ≡ ground target latitude = D ND0 ω ≡ angular orbital velocity ' ω (RE + h) f = ωE ≡ Earth rotational velocity D0 f ≡ EO -1 frame rate ω 'h f = f + h=0 ≡ D0 D0 GSD or pixel size/seperation D0 = 30, N ≈ 23 D ≡ within frame band seperation ≈ ω ' ≈ −3 fh=0 227, 10 N ≡ frames till band coincidence h − f = 227 + ⇒ ∆D ≈ 10 3 ∆h ω’ < 3 10-3 ω 30,000 푎푎푎 ∆ 희 All you need to know about spectral/spatial alignment impact on derived-parameter uncertainty in 10 minutes Steve Ungar – NASA/GSFC Scientist Emeritus HyspIRI Science Symposium – NASA GSFC – May 4, 2010 Synthetic Scene Composition This60 initial characterization of a synthetic scene,50 composed of two landscape components,40 represents a landscape- based30 radiometric parameterization which20 is independent of any specific remotely (%) Reflectance 10 –sensed (pixel-oriented) observation0 strategy. 0,4 0,6 0,8 1,0 This is followed by characterizations of the same scene Wavelengthwhich are (μ m)based on (pixel-oriented)Vegetation observationBright strategies. "Soil" 28 Landscape Reflectance Values Synthetic Scene Scenario .3 .1 .3 .1 .3 .5 .3 .5 .1 .3 .1 .3 .5 .3 .5 .3 .3 .1 .3 .1 .3 .5 .3 .5 .1 .3 .1 .3 .5 .3 .5 .3 VIS Reflectance NIR Reflectance 29 NIR Reflectance (RNIR) .3 .5 .3 .5 Landscape Reflectance Ratios Synthetic Scene Scenario .5 .3 .5 .3 .3 .5 .3 .5 1 5 1 5 .5 .3 .5 .3 5 1 5 1 = VIS Reflectance (RVIS) .3 .1 .3 .1 1 5 1 5 .1 .3 .1 .3 5 1 5 1 .3 .1 .3 .1 RNIR = VI .1 .3 .1 .3 RVIS 30 Pixel Reflectance Values Aligned Bands Scenario .3 .3 .3 .1 .1 .1 .3 .3 .3 .1 .1 .1 .3 .3 .3 .5 .5 .5 .3 .3 .3 .5 .5 .5 .3 .3 .3 .1 .1 .1 .3 .3 .3 .1 .1 .1 .3 .3 .3 .5 .5 .5 .3 .3 .3 .5 .5 .5 .3 .3 .3 .1 .1 .1 .3 .3 .3 .1 .1 .1 .3 .3 .3 .5 .5 .5 .3 .3 .3 .5 .5 .5 .1 .1 .1 .3 .3 .3 .1 .1 .1 .3 .3 .3 .5 ..5 .5 .3 .3 .3 .5 ..5 .5 .3 .3 .3 .1 .1 .1 .3 .3 .3 .1 .1 .1 .3 .3 .3 .5 .5 .5 .3 .3 .3 .5 .5 .5 .3 .3 .3 .1 .1 .1 .3 .3 .3 .1 .1 .1 .3 .3 .3 .5 .5 .5 .3 .3 .3 .5 .5 .5 .3 .3 .3 .3 .3 .3 .1 .1 .1 .3 .3 .3 .1 .1 .1 .3 .3 .3 .5 .5 .5 .3 .3 .3 .5 .5 .5 .3 .3 .3 .1 .1 .1 .3 .3 .3 .1 .1 .1 .3 .3 .3 .5 .5 .5 .3 .3 .3 .5 .5 .5 .3 .3 .3 .1 .1 .1 .3 .3 .3 .1 .1 .1 .3 .3 .3 .5 .5 .5 .3 .3 .3 .5 .5 .5 .1 .1 .1 .3 .3 .3 .1 .1 .1 .3 .3 .3 .5 ..5 .5 .3 .3 .3 .5 ..5 .5 .3 .3 .3 .1 .1 .1 .3 .3 .3 .1 .1 .1 .3 .3 .3 .5 .5 .5 .3 .3 .3 .5 .5 .5 .3 .3 .3 .1 .1 .1 .3 .3 .3 .1 .1 .1 .3 .3 .3 .5 .5 .5 .3 .3 .3 .5 .5 .5 .3 .3 .3 Nominal Position VIS Band Nominal Position NIR Band 31 Pixel Reflectance Values Misaligned Bands Scenario .3 .3 .2 .1 .1 .2 .3 .3 .2 .1 .1 .2 .3 .3 .3 .5 .5 .5 .3 .3 .3 .5 .5 .5 .3 .3 .2 .1 .1 .2 .3 .3 .2 .1 .1 .2 .3 .3 .3 .5 .5 .5 .3 .3 .3 .5 .5 .5 .3 .3 .2 .1 .1 .2 .3 .3 .2 .1 .1 .2 .3 .3 .3 .5 .5 .5 .3 .3 .3 .5 .5 .5 .1 .1 .2 .3 .3 .2 .1 .1 .2 .3 .3 .2 .5 ..5 .5 .3 .3 .3 .5 ..5 .5 .3 .3 .3 .1 .1 .2 .3 .3 .2 .1 .1 .2 .3 .3 .2 .5 .5 .5 .3 .3 .3 .5 .5 .5 .3 .3 .3 .1 .1 .2 .3 .3 .2 .1 .1 .2 .3 .3 .2 .5 .5 .5 .3 .3 .3 .5 .5 .5 .3 .3 .3 .3 .3 .2 .1 .1 .2 .1 .1 .2 .1 .1 .2 .3 .3 .3 .5 .5 .5 .3 .3 .3 .5 .5 .5 .3 .3 .2 .1 .1 .2 .1 .1 .2 .1 .1 .2 .3 .3 .3 .5 .5 .5 .3 .3 .3 .5 .5 .5 .3 .3 .2 .1 .1 .2 .1 .1 .2 .1 .1 .2 .3 .3 .3 .5 .5 .5 .3 .3 .3 .5 .5 .5 .1 .1 .2 .3 .3 .2 .1 .1 .2 .3 .3 .2 .5 ..5 .5 .3 .3 .3 .5 ..5 .5 .3 .3 .3 .1 .1 .2 .3 .3 .2 .1 .1 .2 .3 .3 .2 .5 .5 .5 .3 .3 .3 .5 .5 .5 .3 .3 .3 .1 .1 .2 .3 .3 .2 .1 .1 .2 .3 .3 .2 .5 .5 .5 .3 .3 .3 .5 .5 .5 .3 .3 .3 “Half-pixel” Shift VIS Band Nominal Position NIR Band 32 Results of half pixel misalignment and correction through linear re-sampling Category 1 Category 1 Category 2 Category 2 Scenario Ratio Value Discrepancy Ratio Value Discrepancy VIS and NIR co-aligned 1.00 0% 5.00 0% VIS and NIR misaligned 1.17 +17% 4.17 -17% VIS realigned by resampling 1.13 +13% 3.89 -22% 33 What’sHow we missing can provide from this consistent picture? CalVal across Decadal Missions! As explained in the following slides The Moon can serve as a virtual solar diffuser monitor to validate HyspIRI solar calibration! Well characterized test sites facilitate further validation and transfer of calibration to other Decadal Survey and International Missions ! How EO-1 uses Lunar Images • Lunar Calibration – Calculate Lunar spectral irradiance (EM(λ)) – Compare to the USGS Robotic Lunar Observatory (ROLO) lunar irradiance model • Lunar Calibration Team – Jim Butler – Brian Markham – Lawrence Ong – Kurt Thome – Steve Ungar -- Jack Xiong Typical Lunation EO-1 Lunar Cal/Val (aka Lunar Cycle) USGS Robotic Lunar Observatory ROLO Model Np = Ik Ωp ∑Li,k i=1 π ⋅ Ik Ak = ΩM Ek 1 total lunation takes ~29.5 days Hyperion Lunar Trends Comparison of Hyperion integrated lunar responses with the USGS Robotic Lunar Observatory (ROLO) model for selected bands.