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C O Justice - One of the best experts on this subject based on the ideXlab platform.
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land remote sensing and global environmental change nasa s earth observing system and the science of aster and MODIS
2011Co-Authors: Bhaskar Ramachandran, C O Justice, Michael J AbramsAbstract:Prologue.- Acknowledgements.- Part I: The Earth Observing System and the Evolution of ASTER and MODIS.- Evolution of NASA's Earth Observing System (EOS) and Development of the Moderate-resolution Imaging Spectroradiometer (MODIS) and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Instruments.- Philosophy and Architecture of the EOS Data and Information System (EOSDIS) .- Lessons Learned from the EOSDIS Engineering Experience.- Part II: ASTER and MODIS: Instrument Design, Radiometry and Geometry.- Terra ASTER Instrument Design and Geometry.- ASTER VNIR and SWIR Radiometric Calibration and Atmospheric Correction.- ASTER TIR Radiometric Calibration and Atmospheric Correction.- Terra and Aqua MODIS Design, Radiometry and Geometry in Support of Land Remote Sensing.- Part III: ASTER and MODIS: Data Systems.- ASTER and MODIS Land Data Management at the Land Processes and National Snow and Ice Data Centers.- An Overview of the EOS Data Distribution Systems.- The Language of EOS Data: Hierarchical Data Format.- Part IV: ASTER Science and Applications.- The ASTER Data System: An Overview of the Data Products in Japan and US.- ASTER Applications in Volcanology.- Issues affecting geological mapping with ASTER Data: A Case Study of the Mt Fitton Area, South Australia.- ASTER Data Use in Mining Applications.- ASTER Imaging and Analysis of Glacier Hazards.- ASTER Application in Urban Heat Balance Analysis: A Case Study of Nagoya.- Monitoring Urban Change with ASTER Data.- Estimation of methane emission from west Siberian lowland with sub-pixel land cover characterization between MODIS and ASTER.- ASTER Stereoscopic Data and Digital Elevation Models.- Using ASTER Stereo Images to Quantify Surface Roughness.- Technoscientific Diplomacy: The Practice of International Politics in the ASTER Collaboration.- Part V: MODIS Science and Applications.- MODIS Land Data Products: Generation, Quality Assurance and Validation.- MODIS Directional Surface Reflectance Product: Method, Error Estimates and Validation.- Aqua and Terra MODIS Albedo and Reflectance Anisotropy Products.- MODIS Land Surface Temperature and Emissivity.- MODIS Vegetation Indices.- Leaf Area Index and Fraction of Absorbed PAR Products from Terra and Aqua MODIS Sensors: Analysis, Validation and Refinement.- MODIS-Derived Terrestrial Primary Production.- MODIS-Derived Global Fire Products.- MODIS Snow and Ice Products, and their Assessment and Applications.- Characterizing Global Land Cover Type and Seasonal Land Cover Dynamics at Moderate Spatial Resolution Using MODIS.- MODIS Vegetative Cover Conversion and Vegetation Continuous Fields.- Multi-Sensor Global Retrievals of Evapotranspiration for Climate Studies Using the Surface Energy Budget System.- Part VI: The Future of Land Remote Sensing.- The Evolution of U.S. Moderate Resolution Optical Land Remote Sensing from AVHRR to VIIRS.- The Future of Landsat-Class Remote Sensing.- International Coordination of Satellite Land Observations: Integrated Observations of the Land.- Index.
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the collection 5 MODIS burned area product global evaluation by comparison with the MODIS active fire product
Remote Sensing of Environment, 2008Co-Authors: David P Roy, Luigi Boschetti, C O JusticeAbstract:Abstract The results of the first consecutive 12 months of the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) global burned area product are presented. Total annual and monthly area burned statistics and missing data statistics are reported at global and continental scale and with respect to different land cover classes. Globally the total area burned labeled by the MODIS burned area product is 3.66 × 10 6 km 2 for July 2001 to June 2002 while the MODIS active fire product detected for the same period a total of 2.78 × 10 6 km 2 , i.e., 24% less than the area labeled by the burned area product. A spatio-temporal correlation analysis of the two MODIS fire products stratified globally for pre-fire leaf area index (LAI) and percent tree cover ranges indicate that for low percent tree cover and LAI, the MODIS burned area product defines a greater proportion of the landscape as burned than the active fire product; and with increasing tree cover (> 60%) and LAI (> 5) the MODIS active fire product defines a relatively greater proportion. This pattern is generally observed in product comparisons stratified with respect to land cover. Globally, the burned area product reports a smaller amount of area burned than the active fire product in croplands and evergreen forest and deciduous needleleaf forest classes, comparable areas for mixed and deciduous broadleaf forest classes, and a greater amount of area burned for the non-forest classes. The reasons for these product differences are discussed in terms of environmental spatio-temporal fire characteristics and remote sensing factors, and highlight the planning needs for MODIS burned area product validation.
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validation of the MODIS active fire product over southern africa with aster data
International Journal of Remote Sensing, 2005Co-Authors: Jeffrey T Morisette, Louis Giglio, Ivan Csiszar, C O JusticeAbstract:This paper describes the use of high‐spatial‐resolution ASTER data to determine the accuracy of the moderate‐resolution MODIS active fire product. Our main objective was to develop a methodology to use ASTER data for quantitative evaluation of the MODIS active fire product and to apply it to fires in southern Africa during the 2001 burning season. We utilize 18 ASTER scenes distributed throughout the Southern Africa region covering the time period 5 August 2001 to 6 October 2001. The MODIS fire product is characterized through the use of logistic regression models to establish a relationship between the binary MODIS ‘fire’/‘no fire’ product and summary statistics derived from ASTER data over the coincident MODIS pixel. Probabilities of detection are determined as a function of the total number of ASTER fires and Moran's I, a measure of the spatial heterogeneity of fires within the MODIS pixel. The statistical analysis is done for versions 3 and 4 of the MODIS fire‐detection algorithm. It is shown that the...
Jianglong Zhang - One of the best experts on this subject based on the ideXlab platform.
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an analysis of the collection 5 MODIS over ocean aerosol optical depth product for its implication in aerosol assimilation
Atmospheric Chemistry and Physics, 2010Co-Authors: Jianglong Zhang, Jeffrey S Reid, E J Hyer, C A CurtisAbstract:Abstract. As an update to our previous use of the collection 4 Moderate Resolution Imaging Spectroradiometer (MODIS) over-ocean aerosol optical depth (AOD) data, we examined ten years of Terra and eight years of Aqua collection 5 data for its potential usage in aerosol assimilation. Uncertainties in the over-ocean MODIS AOD were studied as functions of observing conditions, such as surface characteristics, aerosol optical properties, and cloud artifacts. Empirical corrections and quality assurance procedures were developed and compared to collection 4 data. After applying these procedures, the Root-Mean-Square-Error (RMSE) in the MODIS Terra and Aqua AOD are reduced by 30% and 10–20%, respectively, with respect to AERONET data. Ten years of Terra and eight years of Aqua quality-assured level 3 MODIS over-ocean aerosol products were produced. The newly developed MODIS over-ocean aerosol products will be used in operational aerosol assimilation and aerosol climatology studies, as well as other research based on MODIS products.
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MODIS aerosol product analysis for data assimilation assessment of over ocean level 2 aerosol optical thickness retrievals
Journal of Geophysical Research, 2006Co-Authors: Jianglong Zhang, J G ReidAbstract:[1] Currently, the Moderate-resolution Imaging Spectroradiometers (MODIS) level II aerosol product (MOD04/MYD04) is the best aerosol optical depth product suitable for near-real-time aerosol data assimilation. However, a careful analysis of biases and error variances in MOD04/MYD04 aerosol optical depth product is necessary before implementing the MODIS aerosol product in aerosol forecasting applications. Using 1 year's worth of Sun photometer and MOD04/MYD04 aerosol optical depth (τ) data over global oceans, we studied the major biases in MODIS aerosol over-ocean product due to wind speed, cloud contamination, and aerosol microphysical properties. For τ less than 0.6, we found similar uncertainties in the mean MOD04/MYD04 τ as suggested by the MODIS aerosol group, while biases are nonlinear for τ larger than 0.6. We showed that uncertainties in MOD04/MYD04 data can be reduced, and the correlation between MODIS and Sun photometer τ can be improved by reducing the systematic biases in MOD04/MYD04 data through empirical corrections and quality assurance procedures. By removing noise and outliers and ensuring that only the highest-quality data were included, we created a modified aerosol optical depth product that removes most massive outliers and ultimately reduced the absolute error (MODIS–Sun photometer) in MODIS τ at 0.55 μm (τ0.55) by 10–20%. Averaged over 1 year's worth of Terra MODIS aerosol product over global oceans, we found a 12% reduction in MODIS τ0.55 with extremes of 30% over the southern midlatitudes and the North Pacific due to a reduction in cloud contamination. This modified aerosol optical depth product will be used operationally.
D Tanre - One of the best experts on this subject based on the ideXlab platform.
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the MODIS aerosol algorithm products and validation
Journal of the Atmospheric Sciences, 2005Co-Authors: Y J Kaufman, Richard G Kleidman, D Tanre, Charles Ichoku, Shana Mattoo, Robert C Levy, J V Martins, Rongrong Li, E. VermoteAbstract:The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard both NASA’s Terra and Aqua satellites is making near-global daily observations of the earth in a wide spectral range (0.41–15 m). These measurements are used to derive spectral aerosol optical thickness and aerosol size parameters over both land and ocean. The aerosol products available over land include aerosol optical thickness at three visible wavelengths, a measure of the fraction of aerosol optical thickness attributed to the fine mode, and several derived parameters including reflected spectral solar flux at the top of the atmosphere. Over the ocean, the aerosol optical thickness is provided in seven wavelengths from 0.47 to 2.13 m. In addition, quantitative aerosol size information includes effective radius of the aerosol and quantitative fraction of optical thickness attributed to the fine mode. Spectral irradiance contributed by the aerosol, mass concentration, and number of cloud condensation nuclei round out the list of available aerosol products over the ocean. The spectral optical thickness and effective radius of the aerosol over the ocean are validated by comparison with two years of Aerosol Robotic Network (AERONET) data gleaned from 132 AERONET stations. Eight thousand MODIS aerosol retrievals collocated with AERONET measurements confirm that one standard deviation of MODIS optical thickness retrievals fall within the predicted uncertainty of 0.03 0.05 over ocean and 0.05 0.15 over land. Two hundred and seventy-one MODIS aerosol retrievals collocated with AERONET inversions at island and coastal sites suggest that one standard deviation of MODIS effective radius retrievals falls within reff 0.11 m. The accuracy of the MODIS retrievals suggests that the product can be used to help narrow the uncertainties associated with aerosol radiative forcing of global climate.
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validation of MODIS aerosol retrieval over ocean
Geophysical Research Letters, 2002Co-Authors: D Tanre, Oleg Dubovik, Y J Kaufman, A. Smirnov, Charles Ichoku, Shana Mattoo, Robert C Levy, J V MartinsAbstract:[1] The MODerate resolution Imaging Spectroradiometer (MODIS) algorithm for determining aerosol characteristics over ocean is performing within expected accuracy. A two-month data set of MODIS retrievals co-located with observations from the AErosol RObotic NETwork (AERONET) ground-based sunphotometer network provides the necessary validation. Spectral radiation measured by MODIS (in the range 550–2100 nm) is used to retrieve the aerosol optical thickness, effective particle radius and ratio between the submicron and micron size particles. MODIS-retrieved aerosol optical thickness at 660 nm and 870 nm fall within the expected uncertainty, with the ensemble average at 660 nm differing by only 2% from the AERONET observations and having virtually no offset. Roughly seventy percent of MODIS retrievals of aerosol effective radius for optical thickness greater than 0.15 agree with AERONET retrievals to within ±0.10 μm.
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retrieval of aerosol optical thickness and size distribution over ocean from the MODIS airborne simulator during tarfox
Journal of Geophysical Research, 1999Co-Authors: D Tanre, Y J Kaufman, Shana Mattoo, J M Livingston, Lorraine A Remer, Peter V Hobbs, P B Russell, A. SmirnovAbstract:Radiation and in-situ measurements collected during the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) are used to test the method for remote sensing of aerosol properties and loading from the MODIS instrument. MODIS, a Moderate Resolution Imaging Spectroradiometer, will be launched in 1999 aboard the first EOS (Earth Observing System). Following the MODIS procedure [Tanre et al., 1997], the spectral radiance at the top of the atmosphere (TOA) measured over the ocean in a wide spectral range (0.55-2.13 μm) is used to derive the aerosol optical thickness (proportional to the aerosol total loading) and the aerosol size distribution (integrated over the vertical column) of the ambient (undisturbed) aerosol by comparing measured radiances with values in look-up table (LUT). The LUT includes the gas-phase oxidation accumulation mode, cloud-phase accumulation mode, and a coarse mode that represents maritime particles (salt) and dust. In each inversion, one accumulation and one coarse mode can be retrieved. The inversion retrieves the ratio of the contribution to the optical thicknesses of the two particle modes and the mean particle size that best fits the measurements. This algorithm is successfully applied to the data sets acquired during TARFOX. The MODIS airborne simulator (MAS) aboard the NASA ER-2 aircraft flew several times during the experiment above the University of Washington C-131A research aircraft on which the six-channel Ames Airborne Tracking Sun Photometer (AATS-6) was mounted. It flew also above surface-based Sun photometers. Optical thicknesses (at λ = 550 nm) as well as the spectral dependence from the various data sets compare very well.
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remote sensing of aerosol properties over oceans using the MODIS eos spectral radiances
Journal of Geophysical Research, 1997Co-Authors: D Tanre, Y J Kaufman, M Herman, Shana MattooAbstract:Spectral radiances measured at the top of the atmosphere in a wide spectral range (0.55–2.13 μm) are used to monitor the aerosol optical thickness and the aerosol size distribution (integrated on the vertical column) of the ambient (undisturbed) aerosol over the oceans. Even for the moderate resolution imaging spectrometer (MODIS) wide spectral range, only three parameters that describe the aerosol loading and size distribution can be retrieved. These three parameters are not always unique. For instance, the spectral radiance of an aerosol with a bilognormal size distribution can be simulated very well with a single lognormal aerosol with an appropriate mean radius and width of distribution. Preassumptions on the general structure of the size distribution are therefore required in the inversion of MODIS data. The retrieval of the aerosol properties is performed using lookup table computations. The volume size distribution in the lookup table is described with two lognormal modes: a single mode to describe the accumulation mode particles (radius 1.0 μm). Note that two accumulation modes may be present, one dominated by gas phase processes and a second dominated by cloud phase processes. The coarse mode can also be split into several partially overlapping modes describing maritime salt particles and dust. The aerosol parameters we expect to retrieve are η, the fractional contribution of the accumulation mode to scattering; τ, the spectral optical thickness; and rm, the mean particle size of the dominant mode. Additional radiative quantities such as asymmetry parameter and effective radius are derived subsequently. The impact of the surface conditions, wind speed and chlorophyll content on the retrieval is estimated, the impact of potential sources of error like the calibration of the instrument is also tested. The algorithm has been applied successfully to actual data sets provided by the Thematic Mapper on Landsat 5 and by the MODIS airborne simulator on the ER-2 and tested against ground and airborne measurements. A first estimate of the general accuracy is Δτ = ±0.05±0.05τ (at 550 nm), Δrm = 0.3rm, Δη = ±0.25.
Y J Kaufman - One of the best experts on this subject based on the ideXlab platform.
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the MODIS aerosol algorithm products and validation
Journal of the Atmospheric Sciences, 2005Co-Authors: Y J Kaufman, Richard G Kleidman, D Tanre, Charles Ichoku, Shana Mattoo, Robert C Levy, J V Martins, Rongrong Li, E. VermoteAbstract:The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard both NASA’s Terra and Aqua satellites is making near-global daily observations of the earth in a wide spectral range (0.41–15 m). These measurements are used to derive spectral aerosol optical thickness and aerosol size parameters over both land and ocean. The aerosol products available over land include aerosol optical thickness at three visible wavelengths, a measure of the fraction of aerosol optical thickness attributed to the fine mode, and several derived parameters including reflected spectral solar flux at the top of the atmosphere. Over the ocean, the aerosol optical thickness is provided in seven wavelengths from 0.47 to 2.13 m. In addition, quantitative aerosol size information includes effective radius of the aerosol and quantitative fraction of optical thickness attributed to the fine mode. Spectral irradiance contributed by the aerosol, mass concentration, and number of cloud condensation nuclei round out the list of available aerosol products over the ocean. The spectral optical thickness and effective radius of the aerosol over the ocean are validated by comparison with two years of Aerosol Robotic Network (AERONET) data gleaned from 132 AERONET stations. Eight thousand MODIS aerosol retrievals collocated with AERONET measurements confirm that one standard deviation of MODIS optical thickness retrievals fall within the predicted uncertainty of 0.03 0.05 over ocean and 0.05 0.15 over land. Two hundred and seventy-one MODIS aerosol retrievals collocated with AERONET inversions at island and coastal sites suggest that one standard deviation of MODIS effective radius retrievals falls within reff 0.11 m. The accuracy of the MODIS retrievals suggests that the product can be used to help narrow the uncertainties associated with aerosol radiative forcing of global climate.
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validation of MODIS aerosol retrieval over ocean
Geophysical Research Letters, 2002Co-Authors: D Tanre, Oleg Dubovik, Y J Kaufman, A. Smirnov, Charles Ichoku, Shana Mattoo, Robert C Levy, J V MartinsAbstract:[1] The MODerate resolution Imaging Spectroradiometer (MODIS) algorithm for determining aerosol characteristics over ocean is performing within expected accuracy. A two-month data set of MODIS retrievals co-located with observations from the AErosol RObotic NETwork (AERONET) ground-based sunphotometer network provides the necessary validation. Spectral radiation measured by MODIS (in the range 550–2100 nm) is used to retrieve the aerosol optical thickness, effective particle radius and ratio between the submicron and micron size particles. MODIS-retrieved aerosol optical thickness at 660 nm and 870 nm fall within the expected uncertainty, with the ensemble average at 660 nm differing by only 2% from the AERONET observations and having virtually no offset. Roughly seventy percent of MODIS retrievals of aerosol effective radius for optical thickness greater than 0.15 agree with AERONET retrievals to within ±0.10 μm.
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retrieval of aerosol optical thickness and size distribution over ocean from the MODIS airborne simulator during tarfox
Journal of Geophysical Research, 1999Co-Authors: D Tanre, Y J Kaufman, Shana Mattoo, J M Livingston, Lorraine A Remer, Peter V Hobbs, P B Russell, A. SmirnovAbstract:Radiation and in-situ measurements collected during the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) are used to test the method for remote sensing of aerosol properties and loading from the MODIS instrument. MODIS, a Moderate Resolution Imaging Spectroradiometer, will be launched in 1999 aboard the first EOS (Earth Observing System). Following the MODIS procedure [Tanre et al., 1997], the spectral radiance at the top of the atmosphere (TOA) measured over the ocean in a wide spectral range (0.55-2.13 μm) is used to derive the aerosol optical thickness (proportional to the aerosol total loading) and the aerosol size distribution (integrated over the vertical column) of the ambient (undisturbed) aerosol by comparing measured radiances with values in look-up table (LUT). The LUT includes the gas-phase oxidation accumulation mode, cloud-phase accumulation mode, and a coarse mode that represents maritime particles (salt) and dust. In each inversion, one accumulation and one coarse mode can be retrieved. The inversion retrieves the ratio of the contribution to the optical thicknesses of the two particle modes and the mean particle size that best fits the measurements. This algorithm is successfully applied to the data sets acquired during TARFOX. The MODIS airborne simulator (MAS) aboard the NASA ER-2 aircraft flew several times during the experiment above the University of Washington C-131A research aircraft on which the six-channel Ames Airborne Tracking Sun Photometer (AATS-6) was mounted. It flew also above surface-based Sun photometers. Optical thicknesses (at λ = 550 nm) as well as the spectral dependence from the various data sets compare very well.
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remote sensing of aerosol properties over oceans using the MODIS eos spectral radiances
Journal of Geophysical Research, 1997Co-Authors: D Tanre, Y J Kaufman, M Herman, Shana MattooAbstract:Spectral radiances measured at the top of the atmosphere in a wide spectral range (0.55–2.13 μm) are used to monitor the aerosol optical thickness and the aerosol size distribution (integrated on the vertical column) of the ambient (undisturbed) aerosol over the oceans. Even for the moderate resolution imaging spectrometer (MODIS) wide spectral range, only three parameters that describe the aerosol loading and size distribution can be retrieved. These three parameters are not always unique. For instance, the spectral radiance of an aerosol with a bilognormal size distribution can be simulated very well with a single lognormal aerosol with an appropriate mean radius and width of distribution. Preassumptions on the general structure of the size distribution are therefore required in the inversion of MODIS data. The retrieval of the aerosol properties is performed using lookup table computations. The volume size distribution in the lookup table is described with two lognormal modes: a single mode to describe the accumulation mode particles (radius 1.0 μm). Note that two accumulation modes may be present, one dominated by gas phase processes and a second dominated by cloud phase processes. The coarse mode can also be split into several partially overlapping modes describing maritime salt particles and dust. The aerosol parameters we expect to retrieve are η, the fractional contribution of the accumulation mode to scattering; τ, the spectral optical thickness; and rm, the mean particle size of the dominant mode. Additional radiative quantities such as asymmetry parameter and effective radius are derived subsequently. The impact of the surface conditions, wind speed and chlorophyll content on the retrieval is estimated, the impact of potential sources of error like the calibration of the instrument is also tested. The algorithm has been applied successfully to actual data sets provided by the Thematic Mapper on Landsat 5 and by the MODIS airborne simulator on the ER-2 and tested against ground and airborne measurements. A first estimate of the general accuracy is Δτ = ±0.05±0.05τ (at 550 nm), Δrm = 0.3rm, Δη = ±0.25.
Xiaoxiong Xiong - One of the best experts on this subject based on the ideXlab platform.
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validation of MODIS aerosol optical depth product over china using carsnet measurements
Atmospheric Environment, 2011Co-Authors: Yong Xie, Xiaoxiong Xiong, Yan Zhang, Huizheng CheAbstract:Abstract This study evaluates Moderate Resolution Imaging Spectroradiometer (MODIS) Aerosol Optical Depth (AOD) retrievals with ground measurements collected by the China Aerosol Remote Sensing NETwork (CARSNET). In current stage, the MODIS Collection 5 (C5) AODs are retrieved by two distinct algorithms: the Dark Target (DT) and the Deep Blue (DB). The CARSNET AODs are derived with measurements of Cimel Electronique CE-318, the same instrument deployed by the AEROsol Robotic Network (AEROENT). The collocation is performed by matching each MODIS AOD pixel (10 × 10 km 2 ) to CARSNET AOD mean within 7.5 min of satellite overpass. Four-year comparisons (2005–2008) of MODIS/CARSNET at ten sites show the performance of MODIS AOD retrieval is highly dependent on the underlying land surface. The MODIS DT AODs are on average lower than the CARSNET AODs by 6–30% over forest and grassland areas, but can be higher by up to 54% over urban area and 95% over desert-like area. More than 50% of the MODIS DT AODs fall within the expected error envelope over forest and grassland areas. The MODIS DT tends to overestimate for small AOD at urban area. At high vegetated area it underestimates for small AOD and overestimates for large AOD. Generally, its quality reduces with the decreasing AOD value. The MODIS DB is capable of retrieving AOD over desert but with a significant underestimation at CARSNET sites. The best retrieval of the MODIS DB is over grassland area with about 70% retrievals within the expected error. The uncertainties of MODIS AOD retrieval from spatial–temporal collocation and instrument calibration are discussed briefly.
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characterization of MODIS solar diffuser on orbit degradation
Proceedings of SPIE, 2007Co-Authors: Xiaoxiong Xiong, Amit Angal, X Xie, J Choi, Junqiang Sun, W BarnesAbstract:MODIS has 20 reflective solar bands (RSB) that are calibrated on-orbit using a solar diffuser (SD) and a solar diffuser stability monitor (SDSM). The MODIS SD bi-directional reflectance factor (BRF) was characterized pre-launch. Its on-orbit degradation is regularly monitored by the SDSM at wavelengths ranging from 0.41 to 0.94μm. During each SD/SDSM calibration event, the SDSM views alternately the sunlight directly through a fixed attenuation screen and the sunlight diffusely reflected from the SD panel. The time series of SDSM measurements (ratios of the SD view response to the Sun view response) is used to determine the SD BRF degradation at SDSM wavelengths. Since launch Terra MODIS has operated for more than seven years and Aqua for over five years. The SD panel on each MODIS instrument has experienced noticeable degradation with the largest changes observed in the VIS spectral region. This paper provides a brief description of MODIS RSB calibration methodology and SD/SDSM operational activities, and illustrates the SD on-orbit degradation results for both Terra and Aqua MODIS. It also discusses the impact on the SD degradation due to sensor operational activities and SD solar exposure time. Aqua MODIS has been operated under nearly the same condition for more than five years. Its SD annual degradation rate is estimated to be 2.7% at 0.41μm, 1.7% at 0.47μm, and less than 1.0% at wavelengths above 0.53μm. Terra MODIS, on the other hand, has experienced two different SD solar exposure conditions due to an SD door (SDD) operation related anomaly that occurred in May 2003 that had led to a decision to keep the SDD permanently at its "open" position. Prior to this event, Terra MODIS SD degradation rates were very similar to Aqua MODIS. Since then its SD has experienced much faster degradation rates due to more frequent solar exposure.
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MODIS reflective solar bands on orbit lunar calibration
IEEE Transactions on Geoscience and Remote Sensing, 2007Co-Authors: Junqiang Sun, Xiaoxiong Xiong, W Barnes, B GuentherAbstract:The moderate resolution imaging spectroradiometer (MODIS) protoflight model on-board the Terra spacecraft and the MODIS flight model 1 on-board the Aqua spacecraft were launched on December 18, 1999 and May 4, 2002, respectively. They view the moon through the space view (SV) port approximately once a month to monitor the long-term radiometric stability of their reflective solar bands (RSBs). The lunar irradiance observed by MODIS depends on the viewing geometry. Algorithms were developed to select lunar views such that these geometric effects are minimized. In each MODIS lunar observation, the moon can be viewed in multiple scans. The lunar irradiance of a MODIS RSB can be derived from the response of all detectors of a spectral band in one scan which fully covers the moon, from that of one detector in multiple scans or from the response of all detectors in multiple scans. Based on lunar observations, a set of coefficients is defined and derived to trend MODIS system response degradation at the angle of incidence (AOI) of its SV port. It is shown that the degradation is both wavelength and mirror side dependent. Since launch, Terra and Aqua MODIS band 8 (412 nm) mirror side one have degraded 36% and 17%, respectively, at the AOI of the SV. A comparison between the lunar coefficients and those derived from the MODIS on-board solar diffuser (SD) calibrations shows that the response change of the MODIS RSB is both AOI and time dependent. Time-dependent response versus scan angle (RVS) lookup tables derived from lunar views, SD calibration, and Earth-view observations have been used to maintain the quality of the L1B data for both the Terra and Aqua MODIS RSB. The corrections provided by the RVS in the Terra and Aqua MODIS data from the 412-nm band are as large as 14% and 6.2%, respectively.
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MODIS Polarization-Sensitivity Analysis
IEEE Transactions on Geoscience and Remote Sensing, 2007Co-Authors: Junqiang Sun, Xiaoxiong XiongAbstract:The moderate resolution imaging spectroradiometer (MODIS) is one of the primary instruments in the Earth Observing System (EOS). Currently, MODIS instruments are onboard the NASA EOS Terra and Aqua spacecraft launched in December 1999 and May 2002, respectively. The MODIS reflective solar bands (RSBs) are sensitive to the polarization of incident light, particularly for the visible bands. To derive accurate top-of-the-atmosphere radiances, it is essential to know the polarization sensitivity, characterized by a polarization factor and phase angle, of the instruments. From prelaunch polarization sensitivity measurements, the polarization factors and phase angles for all visible and near-infrared bands of both instruments are derived, analyzed, and compared. The polarization factors are wavelength, angle of incidence on the MODIS scan mirror, and detector-dependent. For Terra MODIS, they are also mirrorside-dependent. The 412-nm band has the largest polarization factor, which is about 0.04 for both instruments. The polarization factors of all other bands are either smaller than or close to 0.02, which is the polarization requirement for the MODIS RSB whose wavelengths are longer than 412 nm. The unexpected one-, three-, and four-cycle anomalies observed in the measurements are analyzed. These anomalies are shown to be likely due to the nonuniformity of the light source and the retro-reflected light from the MODIS optical system. Their impacts on the derived polarization parameters are estimated and discussed.
