Stennis Space Center Sensor Characterizations at the Stennis

Stennis Space Center Sensor Characterizations at the Stennis Space Center Inter-Agency Digital Image Acquisition Working Group Meeting Stennis Space Center January 19 -20, 2005

Systems Engineering Approach Stennis Space Center APPLICATIONS RESEARCH TOOLBOX Simulate Systems and Imagery Applications Research Toolbox Instrument Validation Laboratory • • • Define product requirements Define system design Perform parametric trade studies Characterize technology barriers Test algorithms In-Flight Verification & Validation INSTRUMENT VALIDATION LAB Characterize Systems • Baseline performance in controlled environment • Define process for sensor truth set VERIFICATION & VALIDATION Validate Installed Sensors • Validate baseline in-flight • Validate truth set against controlled imagery in-flight • Cross-validate systems 2

Characterizations of Orbimage Orb. View-3 and Digital. Globe Quick. Bird-2 High Spatial Resolution Commercial Image Products Stennis Space Center Orb. View-3 Quick. Bird SSC Characterization Range Orb. View True-color image of SSC acquired on 10/20/03 Quick. Bird True-color image of SSC acquired on 2/17/02 Radiometric Tarps Two 20 X 40 m Edge Targets Total Sky Imager GPS, Spectroradiometer, and Upper Atmosphere Surveys Multifilter Shadowband Radiometer Atmospheric Measurement System Surface Meteorology Stations NASA GSFC AERONET Node Network of Geodetic Targets 3

Reflectance-based Radiometry Measurements Stennis Space Center Goniometer Commercial Satellite Radiosonde Balloon Spectroradiometer Full Sky Imager Integrating Sphere Tarps Sun Photometer Method: Utilize ground reflectance measurements (spectroradiometer) and atmospheric measurements (sun photometer and radiosonde) to determine radiometric accuracy of remote sensing systems. 4

Radiometric Calibration Tarps Stennis Space Center Manufactured by MTL Systems, Inc. • • Four 20 -m x 20 -m tarps with albedo values of approximately 3. 5, 22, 33, and 52% Spectral measurement range: 400– 1050 nm Standard deviation about average albedo less than 1% spatially Peak-to-peak variation in albedo less than 10% within any 100 -nm spectral band Less than 10% variation in albedo values when measuring tarps from 10° to 60° off axis Each side is straight to within ± 6. 0 cm over the 20 -m length Each tarp panel has 60 square witness samples measuring 30. 5 cm by 30. 5 cm Source: JACIE & NASA SSC 5

ASD Field. Spec FR Spectroradiometer Measurements Stennis Space Center • Measurements of several target areas are taken – ~35 -m x 15 -m area of a grassy field – ~30 -m x 20 -m area of a concrete parking lot – Up to four 20 -m x 20 -m radiometric tarps (3. 5%, 22%, 34%, and 52% reflectance) • Measurements are taken along transect lines (grass and concrete) or tarp perimeter – All measurements taken while walking to increase spatial averaging – Periodic Spectralon panel measurements – ASD Field. Spec FR spectroradiometer optimization and dark current measurements taken before and during target measurements. • All data acquired within 30 minutes of satellite overpass 6

Atmospheric Measurements Stennis Space Center • Cloud cover monitoring – Total Sky Imager • Direct solar radiance – Automated Solar Radiometer • Direct, total, and diffuse irradiance – Multi-filter Rotating Shadow-band Radiometer • Vertical profiles of temperature, pressure, and relative humidity – Radiosonde Balloon TSI ASR MFRSR Radiosonde 7

At-Sensor Radiance Prediction Method Stennis Space Center COLLECT GROUND TRUTH DATA RADIOSONDE, TOMS, SENSOR-VIEWING & SOLAR GEOMETRY (P, T, H 2 O, O 3, θV, θS) ATMOSPHERIC GASEOUS PROFILE SUN PHOTOMETER (AEROSOL PROPERTIES) SPECTRORADIOMETER, REFERENCE AND TARGET BRDF, BACKGROUND ALBEDO, SENSOR SPECTRAL RESPONSE AEROSOL ASYMMETRY AND VISIBILITY PROPERTIES TARGET AND BACKGROUND REFLECTANCE Radiative Transfer Input Parameter Setup Software Suite MODTRAN INPUT CHECK AND REVIEW INPUT PARAMETERS MODTRAN VERIFICATION GROUND RADIANCE ESTIMATE FOR REFERENCE PANEL COMPARED TO CALIBRATED ASD RADIANCE NO RADIANCE ESTIMATE AGREES WITH GROUND MEASUREMENTS? YES MODTRAN SENSOR SPECTRAL RESPONSE MODTRAN AT-SENSOR RADIANCE ESTIMATION 8

Spatial Resolution Measurements Stennis Space Center Commercial Satellite Spectroradiometer Edge Target Tarps Method: Utilize edge targets (tarps, SSC concrete edge target, or other manmade features, such as painted runways or buildings) and ground reflectance measurements (spectroradiometer) to determine the edge response of remote sensing systems. 9

Selecting Edge Response Data Stennis Space Center Image area selected for edge response analysis zoom 2 A set of shifted edge response data lines ready for analysis Includes material © Digital. Globe™ Quick. Bird panchromatic image acquired on January 10, 2004 GSD = 60 cm; Edge target tarps oriented for testing in the easting direction 10

IKONOS MTF Measurements Stennis Space Center DN 1000 Measured point Best fit 500 Line Spread Function -15 -5 0 5 Distance / GSD 10 15 1 0. 5 Includes material © Digital. Globe™ FWHM 0 -4 -3 -2 -1 0 -5 1 2 3 4 5 Distance / GSD Selected edge area MTF 1 zoom 2 -10 Nyquist frequency 0. 5 MTF @ Nyquist frequency 0 0 0. 5 1 Normalized spatial frequency 11

Fitting Analytical Functions Stennis Space Center New approach in 2004 (also used in USGS digital camera characterizations): The nonlinear leastsquares optimization with superposition of N sigmoidal functions is conducted seven times for N = 3, 5, 7, 9, 11, 13, and 15. The value of N that provides the best fit is selected to generate final results. Optimized parameters: • a, d • ak, bk, ck, k = 1, …, N All edge positions are on a straight line given by the equation a. Di + bk. Difference in the edge position is introduced by the edge response index (i) multiplied by image GSD (D) and directional coefficient a = tan. With no restrictions placed on values of the optimization parameters, the sigmoidal functions assume a role of general approximation functions (as in neural networks). 12

Geopositional Measurements Stennis Space Center Geodetic Targets Commercial Satellite GPS Instrument Trimble 4000 Method: Utilize geodetic targets and GPS instrumentation to determine the geopositional accuracy of remote sensing systems. 13

Stennis Target Range Stennis Space Center 14

Finding Image Coordinates over SSC Stennis Space Center Step 1 Step 2 Example from February 17, 2002 Quick. Bird pan-merged imagery over SSC Includes material © Digital. Globe. TM Step 3 15