Science.gov

Sample records for aqua modis reflectance

  1. On-Orbit Calibration and Performance of Aqua MODIS Reflective Solar Bands

    NASA Technical Reports Server (NTRS)

    Xiong, Xiaoxiong; Sun, Junqiang; Xie, Xiaobo; Barnes, William; Salomonson, Vincent

    2009-01-01

    Aqua MODIS has successfully operated on-orbit for more than 6 years since its launch in May 2002, continuously making global observations and improving studies of changes in the Earth's climate and environment. 20 of the 36 MODIS spectral bands, covering wavelengths from 0.41 to 2.2 microns, are the reflective solar bands (RSB). They are calibrated on-orbit using an on-board solar diffuser (SD) and a solar diffuser stability monitor (SDSM). In addition, regularly scheduled lunar observations are made to track the RSB calibration stability. This paper presents Aqua MODIS RSB on-orbit calibration and characterization activities, methodologies, and performance. Included in this study are characterizations of detector signal-to-noise ratio (SNR), short-term stability, and long-term response change. Spectral wavelength dependent degradation of the SD bidirectional reflectance factor (BRF) and scan mirror reflectance, which also varies with angle of incidence (AOI), are examined. On-orbit results show that Aqua MODIS onboard calibrators have performed well, enabling accurate calibration coefficients to be derived and updated for the Level 1B (L1B) production and assuring high quality science data products to be continuously generated and distributed. Since launch, the short-term response, on a scan-by-scan basis, has remained extremely stable for most RSB detectors. With the exception of band 6, there have been no new RSB noisy or inoperable detectors. Like its predecessor, Terra MODIS, launched in December 1999, the Aqua MODIS visible (VIS) spectral bands have experienced relatively large changes, with an annual response decrease (mirror side 1) of 3.6% for band 8 at 0.412 microns, 2.3% for band 9 at 0.443 microns, 1.6% for band 3 at 0.469 microns, and 1.2% for band 10 at 0.488 microns. For other RSB bands with wavelengths greater than 0.5 microns, the annual response changes are typically less than 0.5%. In general, Aqua MODIS optics degradation is smaller than Terra

  2. Global space-based inter-calibration system reflective solar calibration reference: from Aqua MODIS to S-NPP VIIRS

    NASA Astrophysics Data System (ADS)

    Xiong, Xiaoxiong; Angal, Amit; Butler, James; Cao, Changyong; Doelling, David; Wu, Aisheng; Wu, Xiangqian

    2016-05-01

    The MODIS has successfully operated on-board the NASA's EOS Terra and Aqua spacecraft for more than 16 and 14 years, respectively. MODIS instrument was designed with stringent calibration requirements and comprehensive on-board calibration capability. In the reflective solar spectral region, Aqua MODIS has performed better than Terra MODIS and, therefore, has been chosen by the Global Space-based Inter- Calibration System (GSICS) operational community as the calibration reference sensor in cross-sensor calibration and calibration inter-comparisons. For the same reason, it has also been used by a number of earth-observing sensors as their calibration reference. Considering that Aqua MODIS has already operated for nearly 14 years, it is essential to transfer its calibration to a follow-on reference sensor with a similar calibration capability and stable performance. The VIIRS is a follow-on instrument to MODIS and has many similar design features as MODIS, including their on-board calibrators (OBC). As a result, VIIRS is an ideal candidate to replace MODIS to serve as the future GSICS reference sensor. Since launch, the S-NPP VIIRS has already operated for more than 4 years and its overall performance has been extensively characterized and demonstrated to meet its overall design requirements. This paper provides an overview of Aqua MODIS and S-NPP VIIRS reflective solar bands (RSB) calibration methodologies and strategies, traceability, and their on-orbit performance. It describes and illustrates different methods and approaches that can be used to facilitate the calibration reference transfer, including the use of desert and Antarctic sites, deep convective clouds (DCC), and the lunar observations.

  3. On-orbit performance and calibration improvements for the reflective solar bands of Terra and Aqua MODIS

    NASA Astrophysics Data System (ADS)

    Angal, Amit; Xiong, Xiaoxiong (Jack); Wu, Aisheng; Chen, Hongda; Geng, Xu; Link, Daniel; Li, Yonghong; Wald, Andrew; Brinkmann, Jake

    2016-05-01

    Moderate Resolution Imaging Spectroradiometer (MODIS) is the keystone instrument for NASA's EOS Terra and Aqua missions, designed to extend and improve heritage sensor measurements and data records of the land, oceans and atmosphere. The reflective solar bands (RSB) of MODIS covering wavelengths from 0.41 μm to 2.2 μm, are calibrated on-orbit using a solar diffuser (SD), with its on-orbit bi-directional reflectance factor (BRF) changes tracked using a solar diffuser stability monitor (SDSM). MODIS is a scanning radiometer using a two-sided paddle-wheel mirror to collect earth view (EV) data over a range of +/-55° off instrument nadir. In addition to the solar calibration provided by the SD and SDSM system, lunar observations at nearly constant phase angles are regularly scheduled to monitor the RSB calibration stability. For both Terra and Aqua MODIS, the SD and lunar observations are used together to track the on-orbit changes of RSB response versus scan angle (RVS) as the SD and SV port are viewed at different angles of incidence (AOI) on the scan mirror. The MODIS Level 1B (L1B) Collection 6 (C6) algorithm incorporated several enhancements over its predecessor Collection 5 (C5) algorithm. A notable improvement was the use of the earth-view (EV) response trends from pseudo-invariant desert targets to characterize the on-orbit RVS for select RSB (Terra bands 1-4, 8, 9 and Aqua bands 8, 9) and the time, AOI, and wavelength-dependent uncertainty. The MODIS Characterization Support Team (MCST) has been maintaining and enhancing the C6 algorithm since its first update in November, 2011 for Aqua MODIS, and February, 2012 for Terra MODIS. Several calibration improvements have been incorporated that include extending the EV-based RVS approach to other RSB, additional correction for SD degradation at SWIR wavelengths, and alternative approaches for on-orbit RVS characterization. In addition to the on-orbit performance of the MODIS RSB, this paper also discusses in

  4. Vicarious calibration of Aqua and Terra MODIS

    NASA Astrophysics Data System (ADS)

    Thome, Kurtis J.; Czapla-Myers, Jeffrey S.; Biggar, Stuart F.

    2003-11-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS) is onboard both the Terra and Aqua platforms. An important aspect of the use of MODIS, and other Earth Science Enterprise sensors, has been the characterization and calibration of the sensors and validation of their data products. The Remote Sensing Group at the University of Arizona has been active in this area through the use of ground- based test sites. This paper presents the results from the reflectance-base approach using the Railroad Valley Playa test site in Nevada for both Aqua and Terra MODIS. The key to the approach is the measurement of surface reflectance over a 1-km2 area of the playa and results from this method shows agreement with both MODIS sensors to better than 5%. Early results indicate that while the two sensors both agree with the ground-based measurements to within the uncertainties of the reflectance-based approach, there were significant differences between the Aqua and Terra MODIS for data prior to September 2002. Recent results indicate that this bias, if any, is now within the uncertainties of the reflectance-based method of calibration.

  5. Aqua MODIS 8-Year On-Orbit Operation and Calibration

    NASA Technical Reports Server (NTRS)

    Xiong, Xiaoxiong; Angal, Amit; Madhavan, Sriharsha; Choi, Taeyoung; Dodd, Jennifer; Geng, Xu; Wang, Zhipeng; Toller, Gary; Barnes, William

    2010-01-01

    Launched in May 2002, the NASA EOS Aqua MODIS has successfully operated for more than 8 years. Observations from Aqua MODIS and its predecessor, Terra MODIS, have generated an unprecedented amount of data products and made significant contributions to studies of changes in the Earth s system of land, oceans, and atmosphere. MODIS collects data in 36 spectral bands: 20 reflective solar bands (RSB) and 16 thermal emissive bands (TEB). It has a set of on-board calibrators (OBC), providing sensor on-orbit radiometric, spectral, and spatial calibration and characterization. This paper briefly summarizes Aqua MODIS on-orbit operation and calibration activities and illustrates instrument on-orbit performance from launch to present. Discussions are focused on OBC functions and changes in detector radiometric gains, spectral responses, and spatial registrations. With ongoing calibration effort, Aqua MODIS will continue serving the science community with high quality data products

  6. Summary of Terra and Aqua MODIS Long-Term Performance

    NASA Technical Reports Server (NTRS)

    Xiong, Xiaoxiong (Jack); Wenny, Brian N.; Angal, Amit; Barnes, William; Salomonson, Vincent

    2011-01-01

    Since launch in December 1999, the MODIS ProtoFlight Model (PFM) onboard the Terra spacecraft has successfully operated for more than 11 years. Its Flight Model (FM) onboard the Aqua spacecraft, launched in May 2002, has also successfully operated for over 9 years. MODIS observations are made in 36 spectral bands at three nadir spatial resolutions and are calibrated and characterized regularly by a set of on-board calibrators (OBC). Nearly 40 science products, supporting a variety of land, ocean, and atmospheric applications, are continuously derived from the calibrated reflectances and radiances of each MODIS instrument and widely distributed to the world-wide user community. Following an overview of MODIS instrument operation and calibration activities, this paper provides a summary of both Terra and Aqua MODIS long-term performance. Special considerations that are critical to maintaining MODIS data quality and beneficial for future missions are also discussed.

  7. Status of Terra and Aqua MODIS Instrument Operation and Calibration

    NASA Astrophysics Data System (ADS)

    Xiong, X.; Wenny, B. N.; Sun, J.; Angal, A.; Salomonson, V. V.

    2013-12-01

    Terra and Aqua MODIS have successfully operated for more than 13 and 11 years since their respective launches in 1999 and 2002. Nearly 40 data products, developed for studies of the earth's land, ocean, and atmosphere, have been routinely generated from calibrated and geo-located MODIS observations and widely distributed to the science and user community. MODIS on-orbit calibration is performed by a set of on-board calibrators, which include a solar diffuser for the reflective solar bands calibration and a blackbody for the thermal emissive bands calibration. MODIS on-board calibrators are regularly operated to monitor on-orbit changes in sensor responses and key performance parameters, such as radiometric calibration coefficients. Since launch, extensive instrument calibration and characterization activities have been scheduled and executed by the MODIS Characterization Support Team (MCST). This presentation provides an overview of both Terra and Aqua MODIS instrument status, their on-orbit operation and calibration activities, and overall long-term performance. It reports calibration improvements (algorithms and look-up tables) made in the latest MODIS data collection (C6). Lessons learned from both Terra and Aqua MODIS and their applications to the S-NPP VIIRS on-orbit calibration are also discussed.

  8. Comparison of Reflected Solar Radiance Using Aqua Modis and Airborne Remote Sensing (case : Deep Convective Clouds and Cirrus Clouds)

    NASA Astrophysics Data System (ADS)

    Krisna, T. C.; Ehrlich, A.; Werner, F.; Wendisch, M.

    2015-12-01

    Deep Convective Clouds (DCCs) have key role in the tropical region. Despite they only have small spatial coverage, but they account most of the total precipitation in these region which often make flooding. There are such of aviation accidents caused by strong vertical wind, hailing, icing and lightning inside the clouds. Pollutions caused by biomass burning and land degradation can change the aerosol properties as well as cloud properties, therefore will influence the radiation and formation of the DCCs. Those are the major reasons that better understanding of DCCs formation and life cycle are necessary. Between Sept. 01 - Oct. 14, ACRIDICON (Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Concevtive Clouds Systems) campaign was conducted over Amazonia. It is suitable area to be the site-study due to has strong contrast environtment (pristine and polluted), regular convection activities and stable meteorological condition. In this study we focus on the 2 satellite validation missions designed to fly collocated but in different altitude with A-TRAIN constellation. In order to study DCCs-solar radiation interaction, we use SMART (Spectral Modular Airborne Radiation Measurements System) installed on HALO (High Altitude and Long-Range Research Aircraft) which measures spectral Irradiance (F) and Radiance (I) at the wavelength between 300-2200 nm corresponding to satellite. Due to the limitation in spatial and temporal, airborne measurements only give snapshots of atmosphere condition and DCCs formation, therefore we use multi-satellite data as DCCs have high vertical and horizontal distance, long temporal development and complex form. The comparison of AQUA MODIS and SMART Radiance at 645 nm (non-absorbing) in the clear-sky condition gives strong agreement, but in the multilayer-cloud condition gives worse and results in high underestimation (-86%) in SMART data especially at lower altitude. The bias is caused by interference from clouds

  9. Corrections to the MODIS Aqua Calibration Derived From MODIS Aqua Ocean Color Products

    NASA Technical Reports Server (NTRS)

    Meister, Gerhard; Franz, Bryan Alden

    2013-01-01

    Ocean color products such as, e.g., chlorophyll-a concentration, can be derived from the top-of-atmosphere radiances measured by imaging sensors on earth-orbiting satellites. There are currently three National Aeronautics and Space Administration sensors in orbit capable of providing ocean color products. One of these sensors is the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite, whose ocean color products are currently the most widely used of the three. A recent improvement to the MODIS calibration methodology has used land targets to improve the calibration accuracy. This study evaluates the new calibration methodology and describes further calibration improvements that are built upon the new methodology by including ocean measurements in the form of global temporally averaged water-leaving reflectance measurements. The calibration improvements presented here mainly modify the calibration at the scan edges, taking advantage of the good performance of the land target trending in the center of the scan.

  10. Status of time-dependent response versus scan-angle (RVS) for Terra and Aqua MODIS reflective solar bands

    NASA Astrophysics Data System (ADS)

    Geng, Xu; Angal, Amit; Sun, Junqiang; Chen, Hongda; Wu, Aisheng; Li, Yonghong; Link, Daniel; Xiong, Xiaoxiong

    2014-09-01

    The MODerate resolution Imaging Spectroradiometer (MODIS) has 20 reflective solar bands (RSB), which are calibrated using a solar diffuser (SD) and near-monthly scheduled lunar observations via a space view (SV) port. The sensor responses observed at two different angles of incidence (AOI) from the SD and lunar measurements are used to track the on-orbit RSB gain changes as well as the response versus scan-angle (RVS) changes. The MODIS RSB have experienced wavelength dependent degradation since launch with the larger degradation observed at the shorter wavelengths. In addition to the SD and lunar observations, the MODIS Characterization Support Team (MCST) regularly monitors the response trending at multiple AOI over selected desert sites. In Collection 6 (C6), a new algorithm using the EV measurements from pseudoinvariant desert sites was developed to better characterize the MODIS scan-angle dependence and it led to a significant improvement in the long-term calibration consistency of the MODIS Level 1B (L1B) products. This approach is formulated for all RSB, and its application was recently extended to Terra band 10, leading to a significant improvement in the ocean-color products. This paper discusses the current status and performance of the on-orbit RVS characterization as applied in C6. Also, the various challenges and future improvement strategies associated with trending the EV response for the high-gain ocean bands are discussed.

  11. Status of Aqua MODIS On-orbit Calibration and Characterization

    NASA Technical Reports Server (NTRS)

    Xiong, X.; Barnes, W.; Chiang, K.; Erives, H.; Che, N.; Sun, J.; Isaacman, A.; Salomonson, V.

    2004-01-01

    The MODIS Flight Model 1 (FM1) has been in operation for more than two years since its launch onboard the NASA's Earth Observing System (EOS) Aqua spacecraft on May 4, 2002. The MODIS has 36 spectral bands: 20 reflective solar bands (RSB) with center wavelengths from 0.41 to 2.2 micron and 16 thermal emissive bands (TEB) from 3.7 to 14.5 micron. It provides the science community observations (data products) of the Earth's land, oceans, and atmosphere for a board range of applications. Its primary on-orbit calibration and characterization activities are performed using a solar diffuser (SD) and a solar diffuser stability monitor (SDSM) system for the RSB and a blackbody for the TEB. Another on-board calibrator (OBC) known as the spectro-radiometric calibration assembly (SRCA) is used for the instrument's spatial (TEB and RSB) and spectral (RSB only) characterization. We present in this paper the status of Aqua MODIS calibration and characterization during its first two years of on-orbit operation. Discussions will be focused on the calibration activities executed on-orbit in order to maintain and enhance the instrument's performance and the quality of its Level 1B (L1B) data products. We also provide comparisons between Aqua MODIS and Terra MODIS (launched in December, 1999), including their similarity and difference in response trending and optics degradation. Existing data and results show that Aqua MODIS bands 8 (0.412 micron) and 9 (0.443 micron) have much smaller degradation than Terra MODIS bands 8 and 9. The most noticeable feature shown in the RSB trending is that the mirror side differences in Aqua MODIS are extremely small and stable (<0.1%) while the Terra MODIS RSB trending has shown significant mirror side difference and wavelength dependent degradation. The overall stability of the Aqua MODIS TEB is also better than that of the Terra MODIS during their first two years of on-orbit operation.

  12. Surface Albedo/BRDF Parameters (Terra/Aqua MODIS)

    DOE Data Explorer

    Trishchenko, Alexander

    2008-01-15

    Spatially and temporally complete surface spectral albedo/BRDF products over the ARM SGP area were generated using data from two Moderate Resolution Imaging Spectroradiometer (MODIS) sensors on Terra and Aqua satellites. A landcover-based fitting (LBF) algorithm is developed to derive the BRDF model parameters and albedo product (Luo et al., 2004a). The approach employs a landcover map and multi-day clearsky composites of directional surface reflectance. The landcover map is derived from the Landsat TM 30-meter data set (Trishchenko et al., 2004a), and the surface reflectances are from MODIS 500m-resolution 8-day composite products (MOD09/MYD09). The MOD09/MYD09 data are re-arranged into 10-day intervals for compatibility with other satellite products, such as those from the NOVA/AVHRR and SPOT/VGT sensors. The LBF method increases the success rate of the BRDF fitting process and enables more accurate monitoring of surface temporal changes during periods of rapid spring vegetation green-up and autumn leaf-fall, as well as changes due to agricultural practices and snowcover variations (Luo et al., 2004b, Trishchenko et al., 2004b). Albedo/BRDF products for MODIS on Terra and MODIS on Aqua, as well as for Terra/Aqua combined dataset, are generated at 500m spatial resolution and every 10-day since March 2000 (Terra) and July 2002 (Aqua and combined), respectively. The purpose for the latter product is to obtain a more comprehensive dataset that takes advantages of multi-sensor observations (Trishchenko et al., 2002). To fill data gaps due to cloud presence, various interpolation procedures are applied based on a multi-year observation database and referring to results from other locations with similar landcover property. Special seasonal smoothing procedure is also applied to further remove outliers and artifacts in data series.

  13. Early on-orbit calibration results from Aqua MODIS

    NASA Astrophysics Data System (ADS)

    Xiong, Xiaoxiong; Barnes, William L.

    2003-04-01

    Aqua MODIS, also known as the MODIS Flight Model 1 (FM1), was launched on May 4, 2002. It opened its nadir aperture door (NAD) on June 24, 2002, beginning its Earth observing mission. In this paper, we present early results from Aqua MODIS on-orbit calibration and characterization and assess the instrument's overall performance. MODIS has 36 spectral bands located on four focal plane assemblies (FPAs). Bands 1-19, and 26 with wavelengths from 0.412 to 2.1 microns are the reflective solar bands (RSB) that are calibrated on-orbit by a solar diffuser (SD). The degradation of the SD is tracked using a solar diffuser stability monitor (SDSM). The bands 20-25, and 27-36 with wavelengths from 3.75 to 14.5 microns are the thermal emissive bands (TEB) that are calibrated on-orbit by a blackbody (BB). Early results indicate that the on-orbit performance has been in good agreement with the predications determined from pre-launch measurements. Except for band 21, the low gain fire band, band 6, known to have some inoperable detectors from pre-launch characterization, and one noisy detector in band 36, all of the detectors' noise characterizations are within their specifications. Examples of the sensor's short-term and limited long-term responses in both TEB and RSB will be provided to illustrate the sensor's on-orbit stability. In addition, we will show some of the improvements that Aqua MODIS made over its predecessor, Terra MODIS (Protoflight Model - PFM), such as removal of the optical leak into the long-wave infrared (LWIR) photoconductive (PC) bands and reduction of electronic crosstalk and out-of-band (OOB) thermal leak into the short-wave infrared (SWIR) bands.

  14. Calibration Adjustments to the MODIS Aqua Ocean Color Bands

    NASA Technical Reports Server (NTRS)

    Meister, Gerhard

    2012-01-01

    After the end of the SeaWiFS mission in 2010 and the MERIS mission in 2012, the ocean color products of the MODIS on Aqua are the only remaining source to continue the ocean color climate data record until the VIIRS ocean color products become operational (expected for summer 2013). The MODIS on Aqua is well beyond its expected lifetime, and the calibration accuracy of the short wavelengths (412nm and 443nm) has deteriorated in recent years_ Initially, SeaWiFS data were used to improve the MODIS Aqua calibration, but this solution was not applicable after the end of the SeaWiFS mission_ In 2012, a new calibration methodology was applied by the MODIS calibration and support team using desert sites to improve the degradation trending_ This presentation presents further improvements to this new approach. The 2012 reprocessing of the MODIS Aqua ocean color products is based on the new methodology.

  15. Cross-calibration of the Oceansat-2 Ocean Colour Monitor (OCM) with Terra and Aqua MODIS

    NASA Astrophysics Data System (ADS)

    Angal, Amit; Brinkmann, Jake; Kumar, A. Senthil; Xiong, Xiaoxiong

    2016-05-01

    The Ocean Colour Monitor (OCM) sensor on-board the Oceansat-2 spacecraft has been operational since its launch in September, 2009. The Oceansat 2 OCM primary design goal is to provide continuity to Oceansat-1 OCM to obtain information regarding various ocean-colour variables. OCM acquires Earth scene measurements in eight multi-spectral bands in the range from 402 to 885 nm. The MODIS sensor on the Terra and Aqua spacecraft has been successfully operating for over a decade collecting measurements of the earth's land, ocean surface and atmosphere. The MODIS spectral bands, designed for land and ocean applications, cover the spectral range from 412 to 869 nm. This study focuses on comparing the radiometric calibration stability of OCM using near-simultaneous TOA measurements with Terra and Aqua MODIS acquired over the Libya 4 target. Same-day scene-pairs from all three sensors (OCM, Terra and Aqua MODIS) between August, 2014 and September, 2015 were chosen for this analysis. On a given day, the OCM overpass is approximately an hour after the Terra overpass and an hour before the Aqua overpass. Due to the orbital differences between Terra and Aqua, MODIS images the Libya 4 site at different scan-angles on a given day. Some of the high-gain ocean bands for MODIS tend to saturate while viewing the bright Libya 4 target, but bands 8-10 (412 nm - 486 nm) provide an unsaturated response and are used for comparison with the spectrally similar OCM bands. All the standard corrections such as bidirectional reflectance factor (BRDF), relative spectral response mismatch, and impact for atmospheric water-vapor are applied to obtain the reflectance differences between OCM and the two MODIS instruments. Furthermore, OCM is used as a transfer radiometer to obtain the calibration differences between Terra and Aqua MODIS reflective solar bands.

  16. Retrieval of Aerosol Properties from MODIS Terra, MODIS Aqua, and VIIRS SNPP: Calibration Focus

    NASA Technical Reports Server (NTRS)

    Levy, Robert C.; Mattoo, Shana; Sawyer, Virginia; Kleidman, Richard; Patadia, Falguni; Zhou, Yaping; Gupta, Pawan; Shi, Yingxi; Remer, Lorraine; Holz, Robert

    2016-01-01

    MODIS-DT Collection 6 - Aqua/Terra level 2, 3; entire record processed - "Trending" issues reduced - Still a 15% or 0.02 Terra vs Aqua offset. - Terra/Aqua convergence improved with C6+, but bias remains. - Other calibration efforts yield mixed results. VIIRS-­-DT in development - VIIRS is similar, yet different then MODIS - With 50% wider swath, VIIRS has daily coverage - Ensures algorithm consistency with MODIS. - Currently: 20% NPP vs Aqua offset over ocean. - Only small bias (%) over land (2012-­-2016) - Can VIIRS/MODIS create aerosol CDR? Calibration for MODIS - VIIRS continues to fundamentally important. It's not just Terra, or just Aqua, or just NPP-­-VIIRS, I really want to push synergistic calibration.

  17. MODIS solar reflective calibration traceability

    NASA Astrophysics Data System (ADS)

    Xiong, Xiaoxiong; Butler, Jim

    2009-08-01

    Long-term climate data records often consist of observations made by multiple sensors. It is, therefore, extremely important to have instrument overlap, to be able to track instrument stability, to quantify measurement uncertainties, and to establish an absolute measurement scale traceable to the International System of Units (SI). The Moderate Resolution Imaging Spectroradiometer (MODIS) is a key instrument for both the Terra and Aqua missions, which were launched in December 1999 and May 2002, respectively. It has 20 reflective solar bands (RSB) with wavelengths from 0.41 to 2.2μm and observes the Earth at three nadir spatial resolutions: 0.25km, 0.5km, and 1km. MODIS RSB on-orbit calibration is reflectance based with reference to the bi-directional reflectance factor (BRF) of its on-board solar diffuser (SD). The SD BRF characterization was made pre-launch by the instrument vendor using reference samples traceable directly to the National Institute of Standards and Technology (NIST). On-orbit SD reflectance degradation is tracked by an on-board solar diffuser stability monitor (SDSM). This paper provides details of this calibration chain, from pre-launch to on-orbit operation, and associated uncertainty assessments. Using MODIS as an example, this paper also discusses challenges and key design requirements for future missions developed for accurate climate studies.

  18. MODIS Solar Reflective Calibration Traceability

    NASA Technical Reports Server (NTRS)

    Xiong, Xiaoxiong; Butler, Jim

    2009-01-01

    Long-term climate data records often consist of observations made by multiple sensors. It is, therefore, extremely important to have instrument overlap, to be able to track instrument stability, to quantify, measurement uncertainties, and to establish absolute scale traceable to the International System of Units (SI). The Moderate Resolution Imaging Spectroradiometer (MODIS) is a key instrument for both the Terra and Aqua missions, which were launched in December 1999 and May 2002, respectively. It has 20 reflective solar bands (RSB) with wavelengths from 0.41 to 2.2 micrometers and observes the Earth at three nadir spatial resolutions: 0.25km, 0.5km, and 1km. MODIS RSB on-orbit calibration is reflectance based with reference to the bidirectional reflectance factor (BRF) of its on-board solar diffuser (SD). The SD BRF characterization was made pre-launch by the instrument vendor using reference samples traceable directly to the National Institute of Standards and Technology (NIST). On-orbit SD reflectance degradation is tracked by an on-board solar diffuser monitor (SDSM). This paper provides details of this calibration chain, from prelaunch to on-orbit operation, and associated uncertainty assessments. Using MODIS as an example, this paper also discusses challenges and key design requirements for future missions developed for accurate climate studies.

  19. Synergism of MODIS Aerosol Remote Sensing from Terra and Aqua

    NASA Technical Reports Server (NTRS)

    Ichoku, Charles; Kaufman, Yoram J.; Remer, Lorraine A.

    2003-01-01

    The MODerate-resolution Imaging Spectro-radiometer (MODIS) sensors, aboard the Earth Observing System (EOS) Terra and Aqua satellites, are showing excellent competence at measuring the global distribution and properties of aerosols. Terra and Aqua were launched on December 18, 1999 and May 4, 2002 respectively, with daytime equator crossing times of approximately 10:30 am and 1:30 pm respectively. Several aerosol parameters are retrieved at 10-km spatial resolution from MODIS daytime data over land and ocean surfaces. The parameters retrieved include: aerosol optical thickness (AOT) at 0.47, 0.55 and 0.66 micron wavelengths over land, and at 0.47, 0.55, 0.66, 0.87, 1.2, 1.6, and 2.1 microns over ocean; Angstrom exponent over land and ocean; and effective radii, and the proportion of AOT contributed by the small mode aerosols over ocean. Since the beginning of its operation, the quality of Terra-MODIS aerosol products (especially AOT) have been evaluated periodically by cross-correlation with equivalent data sets acquired by ground-based (and occasionally also airborne) sunphotometers, particularly those coordinated within the framework of the AErosol Robotic NETwork (AERONET). Terra-MODIS AOT data have been found to meet or exceed pre-launch accuracy expectations, and have been applied to various studies dealing with local, regional, and global aerosol monitoring. The results of these Terra-MODIS aerosol data validation efforts and studies have been reported in several scientific papers and conferences. Although Aqua-MODIS is still young, it is already yielding formidable aerosol data products, which are also subjected to careful periodic evaluation similar to that implemented for the Terra-MODIS products. This paper presents results of validation of Aqua-MODIS aerosol products with AERONET, as well as comparative evaluation against corresponding Terra-MODIS data. In addition, we show interesting independent and synergistic applications of MODIS aerosol data from

  20. Assessment of MODIS Reflected Solar Calibration Uncertainty

    NASA Technical Reports Server (NTRS)

    Xiong, Xiaoxiong; Sun, Junqiang; Butler, James

    2011-01-01

    Determination of the calibration accuracy and traceability of a remote sensing instrument is a driving issue in the use of satellite data for calibration inter-comparisons and studying climate change. The Terra and Aqua MODerate Resolution Imaging Spectroradiometer (MODIS) instruments have successfully operated for more than 11 and 9 years, respectively. Twenty of the thirty six MODIS spectral bands are in the reflected solar region with center wavelengths ranging from 0.41 to 2.2 microns. MODIS reflective solar band (RSB) on-orbit calibration is reflectance based through the use of an on-board solar diffuser (SO). The calibration uncertainty requirements are +/-2.0% for the RSB reflectance factors at sensor specified typical scene reflectances or radiances. The SO bi-directional reflectance factor (BRF) was characterized pre-launch and its on-orbit changes are tracked by an on-board solar diffuser stability monitor (SDSM). This paper provides an assessment of MODIS RSB on-orbit calibration traceability and uncertainty for its Level 1B (L1B) reflectance factors. It examines in details each of the uncertainty contributors, including those from pre-launch measurements as well as on-orbit observations. Common challenging issues and differences due to individual sensors' specific characteristics and on-orbit performance are also discussed in this paper. Guidance and recommendations are presented, based on lessons from MODIS RSB calibration uncertainty assessment, for the development of future instrument calibration and validation plans.

  1. Assessment of MODIS Scan Mirror Reflectance Changes On-Orbit

    NASA Technical Reports Server (NTRS)

    Xiong, Xiaoxiong; Wu, A.; Angal, A.

    2008-01-01

    Since launch, the NASA EOS Terra and Aqua MODIS have operated successfully for more than 8 and 6 years, respectively. MODIS collects data using a two-sided scan mirror over a large scan angular range. The scan mirror is made of a polished, nickel-plated beryllium base coated with high purity silver, which is then over-coated with the Denton proprietary silicon monoxide and silicon dioxide mixture. The scan mirror's reflectance was characterized pre-launch using its witness samples, and the response versus scan angle was measured at the sensor system level. In this study, we present an assessment of MODIS scan mirror on-orbit degradation by examining changes of spectral band response over each sensor's mission lifetime. Results show that the scan mirror's optical properties for both Terra and Aqua MODIS have experienced significant degradation since launch in the VIS spectral region, which is mirror side dependent as well as scan angle dependent. In general, the mirror degradation is more severe for Terra MODIS than Aqua MODIS, especially during recent years. For Terra MODIS, the degradation rate is noticeably different between the mirror sides. On the other hand, there has been little mirror side dependent difference for Aqua MODIS.

  2. An Overview of Lunar Calibration and Characterization for the EOS Terra and Aqua MODIS

    NASA Technical Reports Server (NTRS)

    Xiong, X.; Salomonson, V. V.; Sun, J.; Chiang, K.; Xiong, S.; Humphries, S.; Barnes, W.; Guenther, B.

    2004-01-01

    The Moon can be used as a stable source for Earth-observing sensors on-orbit radiometric and spatial stability monitoring in the VIS and NIR spectral regions. It can also serve as a calibration transfer vehicle among multiple sensors. Nearly identical copies of the Moderate Resolution Imaging Spectroradiometer (MODE) have been operating on-board the NASA's Earth Observing System (EOS) Terra and Aqua satellites since their launches in December 1999 and May 2002, respectively. Terra and Aqua MODIS each make observations in 36 spectral bands covering the spectral range from 0.41 to 14.5 microns and are calibrated on-orbit by a set of on-board calibrations (OBCs) including: 1) a solar diffuser (SD), 2) a solar diffuser stability monitor (SDSM), 3) a blackbody (BB), and 4) a spectro-radiometric calibration assembly (SRCA). In addition to fully utilizing the OBCs, the Moon has been used extensively by both Terra and Aqua MODIS to support their on-orbit calibration and characterization. A 4 This paper provides an overview of applications of lunar calibration and characterization from the MODIS perspective, including monitoring radiometric calibration stability for the reflective solar bands (RSBs), tracking changes of the sensors response versus scan-angle (RVS), examining the sensors spatial performance , and characterizing optical leaks and electronic crosstalk among different spectral bands and detectors. On-orbit calibration consistency between the two MODIS instruments is also addressed. Based on the existing on-orbit time series of the Terra and Aqua MODIS lunar observations, the radiometric difference between the two sensors is less than +/-1% for the RSBs. This method provides a powerful means of performing calibration comparisons among Earth-observing sensors and assures consistent data and science products for the long-term studies of climate and environmental changes.

  3. Multispectral Cloud Retrievals from MODIS on Terra and Aqua

    NASA Technical Reports Server (NTRS)

    King, Michael D.; Platnick, Steven; Ackerman, Steven A.; Menzel, W. Paul; Gray, Mark A.; Moody, Eric G.

    2002-01-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS) was developed by NASA and launched onboard the Terra spacecraft on December 18, 1999 and the Aqua spacecraft on April 26, 2002. MODIS scans a swath width sufficient to provide nearly complete global coverage every two days from each polar-orbiting, sun-synchronous, platform at an altitude of 705 km, and provides images in 36 spectral bands between 0.415 and 14.235 microns with spatial resolutions of 250 m (2 bands), 500 m (5 bands) and 1000 m (29 bands). In this paper we will describe the various methods being used for the remote sensing of cloud properties using MODIS data, focusing primarily on the MODIS cloud mask used to distinguish clouds, clear sky, heavy aerosol, and shadows on the ground, and on the remote sensing of cloud optical properties, especially cloud optical thickness and effective radius of water drops and ice crystals. Additional properties of clouds derived from multispectral thermal infrared measurements, especially cloud top pressure and emissivity, will also be described. Results will be presented of MODIS cloud properties both over the land and over the ocean, showing the consistency in cloud retrievals over various ecosystems used in the retrievals. The implications of this new observing system on global analysis of the Earth's environment will be discussed.

  4. Assessment of the Visible Channel Calibrations of the TRMM VIRS and MODIS on Aqua and Terra

    NASA Technical Reports Server (NTRS)

    Minnis, Patrick; Doelling, David R.; Nguyen, Louis; Miller, Walter F.; Chakrapani, Venketesan

    2007-01-01

    Several recent research satellites carry self-calibrating multispectral imagers that can be used for calibrating operational imagers lacking complete self-calibrating capabilities. In particular, the visible (VIS, 0.65 m) channels on operational meteorological satellites are generally calibrated before launch, but require vicarious calibration techniques to monitor the gains and offsets once they are in orbit. To ensure that the self-calibrating instruments are performing as expected, this paper examines the consistencies between the VIS channel (channel 1) reflectances of the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on the Terra and Aqua satellites and the Version 5a and 6 reflectances of the Visible Infrared Scanner (VIRS) on the Tropical Rainfall Measuring Mission using a variety of techniques. These include comparisons of Terra and Aqua VIS radiances with coincident broadband shortwave radiances from the well-calibrated Clouds and the Earth s Radiant Energy System (CERES), time series of deep convective cloud (DCC) albedos, and ray-matching intercalibrations between each of the three satellites. Time series of matched Terra and VIRS data, Aqua and VIRS data, and DCC reflected fluxes reveal that an older version (Version 5a, ending in early 2004) of the VIRS calibration produced a highly stable record, while the latest version (Version 6) appears to overestimate the sensor gain change by approx.1%/y as the result of a manually induced gain adjustment. Comparisons with the CERES shortwave radiances unearthed a sudden change in the Terra MODIS calibration that caused a 1.17% decrease in the gain on 19 November 2003 that can be easily reversed. After correction for these manual adjustments, the trends in the VIRS and Terra channels are no greater than 0.1%/y. Although the results were more ambiguous, no statistically significant trends were found in the Aqua MODIS channel-1 gain. The Aqua radiances are 1% greater, on average, than their

  5. Overview of Aqua MODIS 10-year On-orbit Calibration and Performance

    NASA Technical Reports Server (NTRS)

    Xiong, X.; Wenny, B.; Sun, J.; Wu, A.; Chen, H.; Angal, A.; Choi, T.; Madhavan, S.; Geng, X.; Link, D.; Toller, G.; Barnes, W.; Salomonson, V.

    2012-01-01

    Since launch in May 2002, Aqua MODIS has successfully operated for nearly 10 years, continuously collecting global datasets for scientific studies of key parameters of the earth's land, ocean, and atmospheric properties and their changes over time. The quality of these geophysical parameters relies on the input quality of sensor calibrated radiances. MODIS observations are made in 36 spectral bands with wavelengths ranging from visible (VIS) to longwave infrared (LWIR). Its reflective solar bands (RSB) are calibrated using data collected from its on-board solar diffuser and regularly scheduled lunar views. The thermal emissive bands (TEB) are calibrated using an on-board blackbody (BB). The changes in the sensor's spectral and spatial characteristics are monitored by an on-board spectroradiometric calibration assembly (SRCA). This paper presents an overview of Aqua MODIS 10-year on-orbit operation and calibration activities, from launch to present, and summarizes its on-orbit radiometric, spectral, and spatial calibration and characterization performance. In addition, it will illustrate and discuss on-orbit changes in sensor characteristics and corrections applied to continuously maintain the sensor level 1B (L1B) data quality, as well as lessons learned that could benefit future calibration efforts.

  6. A Comparison of Cirrus Clouds Retrieved From POLDER-3/PARASOL and MODIS/Aqua

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Yang, P.; Riedi, J.; Kattawar, G.

    2007-12-01

    MODIS on board Aqua and POLDER-3 on board PARASOL are two key instruments in the A-Train constellation of satellites. MODIS has 36 spectral bands with wavelength ranging from 0.41 to 14.5 μm, but makes measurement at only one direction without information about polarization. POLDER performs multidirectional measurements, of both reflectance and polarization, at nine spectral channels (from 443 to 1020 nm). The two instruments offer different, and somehow complementary, advantages for the remote sensing of microphysical and optical properties of cirrus clouds. In this study, a comparison of cirrus clouds retrieved from the two instruments is made to obtain understanding of the possibility, advantages and limitations of synergetic retrieval. First, the comparison is made between the single scattering properties of "Inhomogeneous Hexagonal Monocrystals" (IHM) used in POLDER retrieval algorithm and the ice-crystal ensemble model used for MODIS. Substantial differences are found in the scattering phase matrix. Co-located cloud mask and cloud top height retrievals are compared, with the emphasis on high and thin cirrus clouds. The optical thicknesses of cirrus clouds retrieved by POLDER are compared with those by MODIS, with and without the constraint that the cloud effective particle size retrieved by MODIS must be similar to that of IHM.

  7. NPP VIIRS and Aqua MODIS RSB comparison using observations from simultaneous nadir overpasses (SNO)

    NASA Astrophysics Data System (ADS)

    Wu, Aisheng; Xiong, Xiaoxiong

    2012-09-01

    Suomi NPP (National Polar-orbiting Partnership) satellite (http://npp.gsfc.nasa.gov/viirs.html) began to daily collect global data following its successful launch on October 28, 2011. The Visible Infrared Imaging Radiometer Suite (VIIRS) is a key NPP sensor. Similar to the design of the OLS, SeaWiFS and MODIS instruments, VIIRS has on-board calibration components including a solar diffuser (SD) and a solar diffuser stability monitor (SDSM) for the reflective solar bands (RSB), a V-groove blackbody for the thermal emissive bands (TEB), and a space view (SV) port for background subtraction. Immediately after the VIIRS nadir door's opening on November 21, 2011, anomalously large degradation in the SD response was identified in the near-IR wavelength region, which was unexpected as decreases in the SD reflectance usually occur gradually in the blue (~0.4 μm) wavelength region based on past experience. In this study, we use a well-calibrated Aqua MODIS as reference to track and evaluate VIIRS RSB stability and performance. Reflectances observed by both sensors from simultaneous nadir overpasses (SNO) are used to determine VIIRS to MODIS reflectance ratios for their spectral matching bands. Results of this study provide an immediate post-launch assessment, independent validation of the anomalous degradation observed in SD measurements at near-IR wavelengths and initial analysis of calibration stability and consistency.

  8. NPP VIIRS and Aqua MODIS RSB Comparison Using Observations from Simultaneous Nadir Overpasses (SNO)

    NASA Technical Reports Server (NTRS)

    Xiong, X.; Wu, A.

    2012-01-01

    Suomi NPP (National Polar-orbiting Partnership) satellite (http://npp.gsfc.nasa.gov/viirs.html) began to daily collect global data following its successful launch on October 28, 2011. The Visible Infrared Imaging Radiometer Suite (VIIRS) is a key NPP sensor. Similar to the design of the OLS, SeaWiFS and MODIS instruments, VIIRS has on-board calibration components including a solar diffuser (SD) and a solar diffuser stability monitor (SDSM) for the reflective solar bands (RSB), a V-groove blackbody for the thermal emissive bands (TEB), and a space view (SV) port for background subtraction. Immediately after the VIIRS nadir door s opening on November 21, 2011, anomalously large degradation in the SD response was identified in the near-IR wavelength region, which was unexpected as decreases in the SD reflectance usually occur gradually in the blue (0.4 m) wavelength region based on past experience. In this study, we use a well-calibrated Aqua MODIS as reference to track and evaluate VIIRS RSB stability and performance. Reflectances observed by both sensors from simultaneous nadir overpasses (SNO) are used to determine VIIRS to MODIS reflectance ratios for their spectral matching bands. Results of this study provide an immediate post-launch assessment, independent validation of the anomalous degradation observed in SD measurements at near-IR wavelengths and initial analysis of calibration stability and consistency.

  9. Spatial and Temporal Distribution of Clouds Observed by MODIS Onboard the Terra and Aqua Satellites

    NASA Technical Reports Server (NTRS)

    King, Michael D.; Platnick, Steven; Menzel, W. Paul; Ackerman, Steven A.; Hubanks, Paul A.

    2012-01-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS) was developed by NASA and launched aboard the Terra spacecraft on December 18, 1999 and Aqua spacecraft on May 4, 2002. A comprehensive set of remote sensing algorithms for the retrieval of cloud physical and optical properties have enabled over twelve years of continuous observations of cloud properties from Terra and over nine years from Aqua. The archived products from these algorithms include 1 km pixel-level (Level-2) and global gridded Level-3 products. In addition to an extensive cloud mask, products include cloud-top properties (temperature, pressure, effective emissivity), cloud thermodynamic phase, cloud optical and microphysical parameters (optical thickness, effective particle radius, water path), as well as derived statistics. Results include the latitudinal distribution of cloud optical and radiative properties for both liquid water and ice clouds, as well as latitudinal distributions of cloud top pressure and cloud top temperature. MODIS finds the cloud fraction, as derived by the cloud mask, is nearly identical during the day and night, with only modest diurnal variation. Globally, the cloud fraction derived by the MODIS cloud mask is approx.67%, with somewhat more clouds over land during the afternoon and less clouds over ocean in the afternoon, with very little difference in global cloud cover between Terra and Aqua. Overall, cloud fraction over land is approx.55%, with a distinctive seasonal cycle, whereas the ocean cloudiness is much higher, around 72%, with much reduced seasonal variation. Cloud top pressure and temperature have distinct spatial and temporal patterns, and clearly reflect our understanding of the global cloud distribution. High clouds are especially prevalent over the northern hemisphere continents between 30 and 50 . Aqua and Terra have comparable zonal cloud top pressures, with Aqua having somewhat higher clouds (cloud top pressures lower by 100 hPa) over land due to

  10. Terra and Aqua MODIS Thermal Emissive Bands On-Orbit Calibration and Performance

    NASA Technical Reports Server (NTRS)

    Xiong, Xiaoxiong; Wu, Aisheng; Wenny, Brian N.; Madhavan, Sriharsha; Wang, Zhipeng; Li, Yonghong; Chen, Na; Barnes, William L.; Salomonson, Vincent V.

    2015-01-01

    Since launch, the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on the Terra and Aqua spacecraft have operated successfully for more than 14 and 12 years, respectively. A key instrument for National Aeronautics and Space Administration Earth Observing System missions, MODIS was designed to make continuous observations for studies of Earth's land, ocean, and atmospheric properties and to extend existing data records from heritage Earth observing sensors. The 16 thermal emissive bands (TEBs) (3.75-14.24 micrometers) are calibrated on orbit using a temperature controlled blackbody (BB). Both Terra and Aqua MODIS BBs have displayed minimal drift over the mission lifetime, and the seasonal variations of the BB temperature are extremely small in Aqua MODIS. The long-term gain and noise equivalent difference in temperature performance of the 160 TEB detectors on both MODIS instruments have been well behaved and generally very stable. Small but noticeable variations of Aqua MODIS bands 33-36 (13.34-14.24 micrometer) response in recent years are primarily due to loss of temperature control margin of its passive cryoradiative cooler. As a result, fixed calibration coefficients, previously used by bands when the BB temperature is above their saturation temperatures, are replaced by the focal-plane-temperature-dependent calibration coefficients. This paper presents an overview of the MODIS TEB calibration, the on-orbit performance, and the challenging issues likely to impact the instruments as they continue operating well past their designed lifetime of six years.

  11. Status of Aqua MODIS Instrument On-Orbit Operation and Calibration

    NASA Technical Reports Server (NTRS)

    Xiong, Jack; Angal, Amit; Madhaven, Sri; Choi, Jason; Wenny, Brian; Sun, Junqiang; Wu, Aisheng; Chen, Hongda; Salomonson, Vincent; Barnes, William

    2011-01-01

    The Aqua MOderate resolution Imaging Spectroradiometer (MODIS) has successfully operated for nearly a decade, since its launch in May 2002. MODIS was developed and designed with improvements over its heritage sensors in terms of its overall spectral, spatial, and temporal characteristics, and with more stringent calibration requirements. MODIS carries a set of on-board calibrators that can be used to track and monitor its on-orbit radiometric, spectral, and spatial performance. Since launch, extensive instrument calibration and characterization activities have been scheduled and executed by the MODIS Characterization Support Team (MCST). These efforts are made to assure the quality of instrument calibration and L 1B data products, as well as support all science disciplines (land, ocean, and atmospheric) for continuous improvements of science data product quality. MODIS observations from both Terra and Aqua have significantly contributed to the science and user community over a wide range of research activities and applications. This paper provides an overview of Aqua MODIS on-orbit operation and calibration activities, instrument health status, and on-board calibrators (OBC) performance. On-orbit changes of key sensor parameters, such as spectral band radiometric responses, center wavelengths, and bandwidth, are illustrated and compared with those derived from its predecessor, Terra MODIS. Lessons and challenges identified from Aqua MODIS performance are also discussed in this paper. These lessons are not only critical to future improvements of Aqua MODIS on-orbit operation and calibration but also beneficial to its follow-on instrument, the Visible Infrared Imager Radiometer Suite (VIIRS) to be launched on NPOESS Preparatory Project (NPP) spacecraft.

  12. Lidar Ratios for Dust Aerosols Derived From Retrievals of CALIPSO Visible Extinction Profiles Constrained by Optical Depths from MODIS-Aqua and CALIPSO/CloudSat Ocean Surface Reflectance Measurements

    NASA Technical Reports Server (NTRS)

    Young, Stuart A.; Josset, Damien B.; Vaughan, Mark A.

    2010-01-01

    CALIPSO's (Cloud Aerosol Lidar Infrared Pathfinder Satellite Observations) analysis algorithms generally require the use of tabulated values of the lidar ratio in order to retrieve aerosol extinction and optical depth from measured profiles of attenuated backscatter. However, for any given time or location, the lidar ratio for a given aerosol type can differ from the tabulated value. To gain some insight as to the extent of the variability, we here calculate the lidar ratio for dust aerosols using aerosol optical depth constraints from two sources. Daytime measurements are constrained using Level 2, Collection 5, 550-nm aerosol optical depth measurements made over the ocean by the MODIS (Moderate Resolution Imaging Spectroradiometer) on board the Aqua satellite, which flies in formation with CALIPSO. We also retrieve lidar ratios from night-time profiles constrained by aerosol column optical depths obtained by analysis of CALIPSO and CloudSat backscatter signals from the ocean surface.

  13. On-orbit noise characterization of MODIS reflective solar bands

    NASA Astrophysics Data System (ADS)

    Angal, Amit; Xiong, Xiaoxiong; Sun, Junqiang; Geng, Xu

    2015-01-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS), launched on the Terra and Aqua spacecrafts, was designed to collect complementary and comprehensive measurements of the Earth's properties on a global scale. The 20 reflective solar bands (RSBs), covering a wavelength range from 0.41 to 2.1 μm, are calibrated on-orbit using regularly scheduled solar diffuser (SD) observations. Although primarily used for on-orbit gain derivation, the SD observations also facilitate the characterization of the detector signal-to-noise ratio (SNR). In addition to the calibration requirement of 2% for the reflectance factors and 5% for the radiances, the required SNRs are also specified for all RSB at their typical scene radiances. A methodology to characterize the on-orbit SNR for the MODIS RSB is presented. Overall performance shows that a majority of the RSB continue to meet the specification, therefore performing well. A temporal decrease in the SNR, observed in the short-wavelength bands, is attributed primarily to the decrease in their detector responses. With the exception of the inoperable and noisy detectors in band 6 identified prelaunch, the detectors of Aqua MODIS RSB perform better than Terra MODIS. The approach formulated for on-orbit SNR characterization can also be used by other sensors that use on-board SDs for their on-orbit calibration (e.g., Suomi National Polar-Orbiting Partnership [SNPP]-Visible Infrared Imaging Radiometer Suite).

  14. On-Orbit Noise Characterization of MODIS Reflective Solar Bands

    NASA Technical Reports Server (NTRS)

    Angal, Amit; Xiong, Xiaoxiong; Sun, Junqiang; Geng, Xu

    2015-01-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS), launched on the Terra and Aqua spacecrafts, was designed to collect complementary and comprehensive measurements of the Earth's properties on a global scale. The 20 reflective solar bands (RSBs), covering a wavelength range from 0.41 to 2.1 micrometers, are calibrated on-orbit using regularly scheduled solar diffuser (SD) observations. Although primarily used for on-orbit gain derivation, the SD observations also facilitate the characterization of the detector signal-to-noise ratio (SNR). In addition to the calibration requirement of 2% for the reflectance factors and 5% for the radiances, the required SNRs are also specified for all RSB at their typical scene radiances. A methodology to characterize the on-orbit SNR for the MODIS RSB is presented. Overall performance shows that a majority of the RSB continue to meet the specification, therefore performing well. A temporal decrease in the SNR, observed in the short-wavelength bands, is attributed primarily to the decrease in their detector responses. With the exception of the inoperable and noisy detectors in band 6 identified prelaunch, the detectors of AquaMODIS RSB perform better than TerraMODIS. The approach formulated for on-orbit SNR characterization can also be used by other sensors that use on-board SDs for their on-orbit calibration (e.g., Suomi National Polar-Orbiting Partnership [SNPP]-Visible Infrared Imaging Radiometer Suite).

  15. Terra and Aqua MODIS Design, Radiometry, and Geometry in Support of Land Remote Sensing

    NASA Technical Reports Server (NTRS)

    Xiong, Xiaoxiong; Wolfe, Robert; Barnes, William; Guenther, Bruce; Vermote, Eric; Saleous, Nazmi; Salomonson, Vincent

    2011-01-01

    The NASA Earth Observing System (EOS) mission includes the construction and launch of two nearly identical Moderate Resolution Imaging Spectroradiometer (MODIS) instruments. The MODIS proto-flight model (PFM) is onboard the EOS Terra satellite (formerly EOS AM-1) launched on December 18, 1999 and hereafter referred to as Terra MODIS. Flight model-1 (FM1) is onboard the EOS Aqua satellite (formerly EOS PM-1) launched on May 04, 2002 and referred to as Aqua MODIS. MODIS was developed based on the science community s desire to collect multiyear continuous datasets for monitoring changes in the Earth s land, oceans and atmosphere, and the human contributions to these changes. It was designed to measure discrete spectral bands, which includes many used by a number of heritage sensors, and thus extends the heritage datasets to better understand both long- and short-term changes in the global environment (Barnes and Salomonson 1993; Salomonson et al. 2002; Barnes et al. 2002). The MODIS development, launch, and operation were managed by NASA/Goddard Space Flight Center (GSFC), Greenbelt, Maryland. The sensors were designed, built, and tested by Raytheon/ Santa Barbara Remote Sensing (SBRS), Goleta, California. Each MODIS instrument offers 36 spectral bands, which span the spectral region from the visible (0.41 m) to long-wave infrared (14.4 m). MODIS collects data at three different nadir spatial resolutions: 0.25, 0.5, and 1 km. Key design specifications, such as spectral bandwidths, typical scene radiances, required signal-to-noise ratios (SNR) or noise equivalent temperature differences (NEDT), and primary applications of each MODIS spectral band are summarized in Table 7.1. These parameters were the basis for the MODIS design. More details on the evolution of the NASA EOS and development of the MODIS instruments are provided in Chap. 1. This chapter focuses on the MODIS sensor design, radiometry, and geometry as they apply to land remote sensing. With near

  16. Seasonal and Diurnal Tropical Forest Greenness Observed and Modeled Using MODIS Terra and Aqua Sensors

    NASA Astrophysics Data System (ADS)

    Huete, A. R.; Davies, K.; Restrepo-Coupe, N.; Ratana, P.; Sun, Q.; Saleska, S. R.; Schaaf, C.

    2014-12-01

    Recent studies on satellite measures of Amazon forest greening suggest that observed seasonalities are optical artefacts resulting from shifting sun- sensor view geometries between solstice and equinox periods. The degree and extent of sun geometry influences on satellite observations have important implications on the utility of multi-sensor time series for generating accurate long-term data records. Here we investigate sun angle interactions on tropical forest greening using Terra- and Aqua-MODIS, and combined Terra-Aqua Nadir BRDF Adjusted Reflectance (NBAR) vegetation index (VI) time series, with distinct seasonal and daily sun angle conditions for 10:30 a.m., 1:30 p.m. overpasses, and local solar noon times, respectively. This was compared with modeled, sun angle corrected data from the MODIS MCD43A1 product for fixed sun angles. The interactions between sun angle and forest greening were analyzed along an equatorial forest transect of constant sun-earth geometry but variable annual rainfall and dry season length, as well as a latitudinal transect ranging from equatorial to dry southern forests. In equatorial forests, seasonality in sun angle geometry was synchronous with drought seasonality and resulted in broad scale, forest greening consistent with the duration of the dry season and light availability. The sun angle corrected data showed a reduction in the magnitude of seasonal greening, but also revealed an extended greening period well beyond the equinox. On the other hand, across the latitudinal gradient there were shifts in the start and duration of the dry season that resulted in greening patterns that were asynchronous with sun angle geometries. Sun angle influences became significant and were more pronounced at greater latitudes, demonstrating need to normalize cross-sensor satellite data for sun geometry effects, especially with the recent and upcoming launches of new satellite systems.

  17. Analog and digital saturation in the MODIS reflective solar bands

    NASA Astrophysics Data System (ADS)

    Madhavan, S.; Angal, A.; Dodd, J.; Sun, J.; Xiong, X.

    2012-09-01

    The MODIS instrument on the Terra and Aqua spacecrafts is a 12 bit sensor with an analog-to-digital (A/D) range of 0 to 4095 DN. Each sensor system is limited by a range at the low and high ends of the dynamic scale. At the low end, quantization noise is the limiting factor whereas at the high end the maximum value is limited by the capability of the amplifier, 4095 in the case of MODIS. However, in both Terra and Aqua MODIS certain detectors in the Reflective Solar Bands (RSB) tend to pre-saturate at a value lower than 4095. This paper serves as a comprehensive report on the algorithms developed to characterize the pre-saturation limit in the RSB. The paper also provides the digital and pre-saturation (analog saturation) limits for the RSB that are currently being used in the Level 1B (L1B) products. The digital and analog saturation limits are well characterized using the Level 1A (L1A) raw Earth-View (EV) data and through the on-board Electronic Calibration (E-CAL). Also, in this paper an analysis is done to study the sensors dynamic range due to the long term changes in the instrument response. In summary, the algorithms and results reported in this paper are important as the radiometric accuracy / uncertainty for instruments such as MODIS, VIIRS (NPP) tends to be coupled to pre-saturation.

  18. Two MODIS Aerosol Products Over Ocean on the Terra and Aqua CERES SSF Datasets

    NASA Technical Reports Server (NTRS)

    Ignatov, Alexander; Minnis, Patrick; Loeb, Norman; Wielicki, Bruce; Miller, Walter; Sun-Mack, Sunny; Tanre, Didier; Remer, Lorraine; Laszlo, Istvan; Geier, Erika

    2004-01-01

    Over ocean, two aerosol products are reported on the Terra and Aqua CERES SSFs. Both are derived from MODIS, but using different sampling and aerosol algorithms. This study briefly summarizes these products, and compares using 2 weeks of global Terra data from 15-21 December 2000, and 1-7 June 2001.

  19. On-Orbit Noise Characterization for MODIS Reflective Solar Bands

    NASA Technical Reports Server (NTRS)

    Xiong, X.; Xie, X.; Angal, A.

    2008-01-01

    Since launch, the Moderate Resolution Imaging Spectroradiometer (MODIS) has operated successfully on-board the NASA Earth Observing System (EOS) Terra and EOS Aqua spacecraft. MODIS is a passive cross-track scanning radiometer that makes observations in 36 spectral bands with spectral wavelengths from visible (VIS) to long-wave infrared. MODIS bands 1-19 and 26 are the reflective solar bands (RSB) with wavelengths from 0.41 to 2.2 micrometers. They are calibrated on-orbit using an on-board solar diffuser (SD) and a SD stability monitor (SDSM) system. For MODIS RSB, the level 1B calibration algorithm produces top of the atmosphere reflectance factors and radiances for every pixel of the Earth view. The sensor radiometric calibration accuracy, specified at each spectral band's typical scene radiance, is 2% for the RSB reflectance factors and 5% for the RSB radiances. Also specified at the typical scene radiance is the detector signal-to-noise ratio (SNR), a key sensor performance parameter that directly impacts its radiometric calibration accuracy and stability, as well as the image quality. This paper describes an on-orbit SNR characterization approach developed to evaluate and track MODIS RSB detector performance. In order to perform on-orbit SNR characterization, MODIS RSB detector responses to the solar illumination reflected from the SD panel must be corrected for factors due to variations of the solar angles and the SD bi-directional reflectance factor. This approach enables RSB SNR characterization to be performed at different response levels for each detector. On-orbit results show that both Terra and Aqua MODIS RSB detectors have performed well since launch. Except for a few noisy or inoperable detectors which were identified pre-launch, most RSB detectors continue to meet the SNR design requirements and are able to maintain satisfactory short-term stability. A comparison of on-orbit noise characterization results with results derived from pre

  20. Validation of MODIS Terra and Aqua Ice Surface Temperatures at Summit, Greenland

    NASA Astrophysics Data System (ADS)

    Hall, D. K.; Shuman, C. A.; Xiong, X.; Wenny, B. N.; DiGirolamo, N. E.

    2014-12-01

    Ice-surface temperature (IST) is used in many studies, for example for validation of model output and for detection of leads and thin ice in sea ice. The MODerate-resolution Imaging Spectroradiometer (MODIS) instruments on the Terra and Aqua satellites are useful for mapping IST of sea ice and the Greenland ice sheet (Hall et al., 2012), and validation of the ISTs derived from MODIS has been an ongoing effort (e.g., Koenig & Hall, 2010; Shuman et al., 2014). Recent results call into question the calibration of the MODIS-derived ISTs at very cold temperatures that are characteristic of the Greenland ice sheet high interior during winter (Shuman et al., 2014). In the present work, we investigate the calibration of MODIS IR bands 31 (10.780 - 11.280 µm) and 32 (11.770 - 12.270 µm) under very cold conditions. MODIS IR bands are calibrated using a quadratic algorithm. In Collection 6 (C6), the offset and nonlinear calibration coefficients are computed from data collected during the blackbody cool-down vs the warm-up data used in Collection 5 (C5). To improve the calibration accuracy for low-temperature scenes, the offset terms are set to 0. In general, Aqua MODIS bands 31 and 32 perform better than Terra MODIS bands 31 and 32. One of the reasons is that the Aqua bands have a lower saturation temperature (~340 K) than the Terra (~380 K) bands, and lower saturation or smaller dynamic range means better resolution. As compared to ~2-m NOAA air temperatures (TA) at Summit, Greenland, Shuman et al. (2014) show a small (~0.5°C) offset in Terra MODIS-derived IST vs TA near 0°C, and an increasingly larger offset (up to ~5°C) as TA drops to -60°C. To investigate this further, we compare Terra and Aqua C5 and C6 ISTs with TA data from Summit. This work will document the calibration of bands 31 and 32 at very low temperatures in C5 and C6. Hall, D.K., et al., 2012: Satellite-Derived Climate-Quality Data Record of the Clear-Sky Surface Temperature of the Greenland Ice Sheet

  1. Using the Moon to Track MODIS Reflective Solar Bands Calibration Stability

    NASA Technical Reports Server (NTRS)

    Xiong, Xiaoxiong; Geng, Xu; Angal, Amit; Sun, Junqiang; Barnes, William

    2011-01-01

    MODIS has 20 reflective solar bands (RSB) in the visible (VIS), near infrared (NIR), and short-wave infrared (SWIR) spectral regions. In addition to instrument on-board calibrators (OBC), lunar observations have been used by both Terra and Aqua MODIS to track their reflective solar bands (RSB) on-orbit calibration stability. On a near monthly basis, lunar observations are scheduled and implemented for each instrument at nearly the same lunar phase angles. A time series of normalized detector responses to the Moon is used to monitor its on-orbit calibration stability. The normalization is applied to correct the differences of lunar viewing geometries and the Sun-Moon-Sensor distances among different lunar observations. Initially, the lunar calibration stability monitoring was only applied to MODIS bands (1-4 and 8-12) that do not saturate while viewing the Moon. As the mission continued, we extended the lunar calibration stability monitoring to other RSB bands (bands 13-16) that contain saturated pixels. For these bands, the calibration stability is monitored by referencing their non-saturated pixels to the matched pixels in a non-saturation band. In this paper, we describe this relative approach and apply it to MODIS regularly scheduled lunar observations. We present lunar trending results for both Terra and Aqua MODIS over their entire missions. Also discussed in the paper are the advantages and limitations of this approach and its potential applications to other earth-observing sensors. Keywords: Terra, Aqua, MODIS, sensor, Moon, calibration, stability

  2. Spatial and Temporal Distribution of Clouds as Observed by MODIS Onboard the Terra and Aqua Satellites

    NASA Technical Reports Server (NTRS)

    King, Michael D.; Platnick, Steven; Menzel, Paul; Ackerman, Steven A.

    2006-01-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS) was developed by NASA and launched onboard the Terra spacecraft on December 18,1999 and Aqua spacecraft on May 4, 2002. It achieved its final orbit and began Earth observations on February 24,2000 for Terra and June 24,2002 for Aqua. A comprehensive set of remote sensing algorithms for cloud masking and the retrieval of cloud physical and optical properties has been developed by members of the MODIS atmosphere science team. The archived products from these algorithms have applications in climate change studies, climate modeling, numerical weather prediction, and fundamental atmospheric research. In addition to an extensive cloud mask, products include cloud-top properties (temperature, pressure, effective emissivity), cloud thermodynamic phase, cloud optical and microphysical parameters (optical thickness, effective particle radius, water path), as well as derived statistics. Over the last year, extensive improvements and enhancements in the global cloud products have been implemented, and reprocessing of all MODIS data on Terra has commenced since first light in February 2000. In the cloud mask algorithm, the most extensive improvements were in distinguishing clouds at nighttime, including the challenging polar darkness regions of the world. Additional improvements have been made to properly distinguish sunglint from clouds in the tropical ocean regions, and to improve the identification of clouds from snow during daytime in Polar Regions. We will show global monthly mean cloud fraction for both Terra and Aqua, and show how similar the global daytime cloud fraction is from these morning and afternoon orbits, respectively. We will also show the zonal distribution of cloud fraction over land and ocean regions for both Terra and Aqua, and show the time series of global cloud fraction from July 2002 through June 2006.

  3. Assessment of diverse algorithms applied on MODIS Aqua and Terra data over land surfaces in Europe

    NASA Astrophysics Data System (ADS)

    Glantz, P.; Tesche, M.

    2012-04-01

    Beside an increase of greenhouse gases (e.g., carbon dioxide, methane and nitrous oxide) human activities (for instance fossil fuel and biomass burning) have lead to perturbation of the atmospheric content of aerosol particles. Aerosols exhibits high spatial and temporal variability in the atmosphere. Therefore, aerosol investigation for climate research and environmental control require the identification of source regions, their strength and aerosol type, which can be retrieved based on space-borne observations. The aim of the present study is to validate and evaluate AOT (aerosol optical thickness) and Ångström exponent, obtained with the SAER (Satellite AErosol Retrieval) algorithm for MODIS (MODerate resolution Imaging Spectroradiometer) Aqua and Terra calibrated level 1 data (1 km horizontal resolution at ground), against AERONET (AErosol RObotic NETwork) observations and MODIS Collection 5 (c005) standard product retrievals (10 km), respectively, over land surfaces in Europe for the seasons; early spring (period 1), mid spring (period 2) and summer (period 3). For several of the cases analyzed here the Aqua and Terra satellites passed the investigation area twice during a day. Thus, beside a variation in the sun elevation the satellite aerosol retrievals have also on a daily basis been performed with a significant variation in the satellite-viewing geometry. An inter-comparison of the two algorithms has also been performed. The validation with AERONET shows that the MODIS c005 retrieved AOT is, for the wavelengths 0.469 and 0.500 nm, on the whole within the expected uncertainty for one standard deviation of the MODIS retrievals over Europe (Δτ = ±0.05 ± 0.15τ). The SAER estimated AOT for the wavelength 0.443 nm also agree reasonable well with AERONET. Thus, the majority of the SAER AOT values are within the MODIS expected uncertainty range, although somewhat larger RMSD (root mean square deviation) occurs compared to the results obtained with the

  4. Spatial and Temporal Distribution of Tropospheric Clouds Observed by MODIS Onboard the Terra and Aqua Satellites

    NASA Technical Reports Server (NTRS)

    King, Michael D.

    2005-01-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS) was developed by NASA and launched onboard the Terra spacecraft on December 18, 1999 and Aqua spacecraft on May 4, 2002. It achieved its final orbit and began Earth observations on February 24, 2000 for Terra and June 24, 2002 for Aqua. A comprehensive set of remote sensing algorithms for cloud masking and the retrieval of cloud physical and optical properties has been developed by members of the MODIS atmosphere science team. The archived products from these algorithms have applications in climate change studies, climate modeling, numerical weather prediction, as well as fundamental atmospheric research. In addition to an extensive cloud mask, products include cloud-top properties (temperature, pressure, effective emissivity), cloud thermodynamic phase, cloud optical and microphysical parameters (optical thickness, effective particle radius, water path), as well as derived statistics. We will describe the various cloud properties being analyzed on a global basis from both Terra and Aqua. These include the latitudinal distribution of cloud optical and radiative properties of both liquid water and ice clouds, as well as joint histograms of cloud optical thickness and effective radius for selected geographical locations around the world.

  5. Spatial and Temporal Distribution of Tropospheric Clouds Observed by MODIS Onboard the Terra and Aqua Satellites

    NASA Technical Reports Server (NTRS)

    King, Michael D.; Platnick, Steven

    2005-01-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS) was developed by NASA and launched onboard the Terra spacecraft on December 18,1999 and Aqua spacecraft on May 4, 2002. It achieved its final orbit and began Earth observations on February 24, 2000 for Terra and June 24, 2002 for Aqua. A comprehensive set of remote sensing algorithms for cloud masking and the retrieval of cloud physical and optical properties has been developed by members of the MODIS atmosphere science team. The archived products from these algorithms have applications in climate change studies, climate modeling, numerical weather prediction, as well as fundamental atmospheric research. In addition to an extensive cloud mask, products include cloud-top properties (temperature, pressure, effective emissivity), cloud thermodynamic phase, cloud optical and microphysical parameters (optical thickness, effective particle radius, water path), as well as derived statistics. We will describe the various cloud properties being analyzed on a global basis from both Terra and Aqua. These include the latitudinal distribution of cloud optical and radiative properties of both liquid water and ice clouds, as well as joint histograms of cloud optical thickness and effective radius for selected geographical locations around the world.

  6. Consistency of Global Modis Aerosol Optical Depths over Ocean on Terra and Aqua Ceres SSF Datasets

    NASA Technical Reports Server (NTRS)

    Ignatov, Alexander; Minnis, Patrick; Miller, Walter F.; Wielicki, Bruce A.; Remer, Lorraine

    2006-01-01

    Aerosol retrievals over ocean from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Terra and Aqua platforms are available from the Clouds and the Earth's Radiant Energy System (CERES) Single Scanner Footprint (SSF) datasets generated at NASA Langley Research Center (LaRC). Two aerosol products are reported side-by-side. The primary M product is generated by sub-setting and remapping the multi-spectral (0.47-2.1 micrometer) MODIS produced oceanic aerosol (MOD04/MYD04 for Terra/Aqua) onto CERES footprints. M*D04 processing uses cloud screening and aerosol algorithms developed by the MODIS science team. The secondary AVHRR-like A product is generated in only two MODIS bands 1 and 6 (on Aqua, bands 1 and 7). The A processing uses the CERES cloud screening algorithm, and NOAA/NESDIS glint identification, and single-channel aerosol retrieval algorithms. The M and A products have been documented elsewhere and preliminarily compared using 2 weeks of global Terra CERES SSF Edition 1A data in which the M product was based on MOD04 collection 3. In this study, the comparisons between the M and A aerosol optical depths (AOD) in MODIS band 1 (0.64 micrometers), tau(sub 1M) and tau(sub 1A) are re-examined using 9 days of global CERES SSF Terra Edition 2A and Aqua Edition 1B data from 13 - 21 October 2002, and extended to include cross-platform comparisons. The M and A products on the new CERES SSF release are generated using the same aerosol algorithms as before, but with different preprocessing and sampling procedures, lending themselves to a simple sensitivity check to non-aerosol factors. Both tau(sub 1M) and tau(sub 1A) generally compare well across platforms. However, the M product shows some differences, which increase with ambient cloud amount and towards the solar side of the orbit. Three types of comparisons conducted in this study - cross-platform, cross-product, and cross-release confirm the previously made observation that the major area for

  7. MODIS Cloud Products Derived from Terra and Aqua During CRYSTAL-FACE

    NASA Technical Reports Server (NTRS)

    King, Michael D.; Platnick, S.; Riedi, J. C.; Ackerman, S. A.; Menzel, W. P.

    2003-01-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS), developed as part of the Earth Observing System (EOS) and launched on Terra in December 1999 and Aqua in May 2002, is designed to meet the scientific needs for satellite remote sensing of clouds, aerosols, water vapor, and land and ocean surface properties. During the CRYSTAL-FACE experiment, numerous aircraft coordinated both in situ and remote sensing observations with the Terra and Aqua spacecraft. In this paper we will emphasize the optical, microphysical, and physical properties of both liquid water and ice clouds obtained from an analysis of the satellite observations over Florida and the Gulf of Mexico during July 2002. We will present the frequency distribution of liquid water and ice cloud microphysical properties throughout the region, separating the results over land and ocean. Probability distributions of effective radius and cloud optical thickness will also be shown.

  8. Urban vegetation land covers change detection using multi-temporal MODIS Terra/Aqua data

    NASA Astrophysics Data System (ADS)

    Zoran, Maria A.; Savastru, Roxana S.; Savastru, Dan M.; Dida, Adrian I.; Ionescu, Ovidiu M.

    2013-10-01

    Urban vegetation land cover change is a direct measure of quantitative increase or decrease in sources of urban pollution and the dimension of extreme climate events and changes that determine environment quality. Spatio- temporal monitoring of urban vegetation land cover changes is a very important task for establishing the links between policy decisions, regulatory actions and subsequent land use activities. Former studies incorporating two-date change detection using Landsat TM/ETM data had limited performance for urban biophysically complex systems applications. In this paper, we describe recent results using data from NASA's Moderate Resolution Imaging Spectroradiometer and NOAA/AVHRR satellite to study urban vegetation land cover dynamics. This study explored the use of time-series MODIS Terra/Aqua Normalized Difference Vegetation Index (NDVI) and Leaf Area Index (LAI), data to provide change detection information for metropolitan area of Bucharest in Romania. Training and validation are based on a reference dataset collected from IKONOS high resolution remote sensing data. The mean detection accuracy for period 2002- 2012 was assessed to be of 89%, with a reasonable balance between change commission errors (21.7%), change omission errors (28.5%), and Kappa coefficient of 0.69. Annual change detection rates across the urban/periurban areas over the study period (2002-2012) were estimated at 0.78% per annum in the range of 0.45% (2002) to 0.75% (2012).Vegetation dynamics in urban areas at seasonal and longer timescales reflect large-scale interactions between the terrestrial biosphere and the climate system.

  9. Evaluation of monthwise and overall trends of AOD over Indian cities using MODIS Aqua and Terra retrievals

    NASA Astrophysics Data System (ADS)

    Banerjee, Subhasis; Ghosh, Sanjay

    2016-07-01

    Atmospheric aerosols have been shown to have profound impact on climate system and human health. Regular and systematic monitoring of ambient air is thus necessary in order to asses its impact. There are several ground based stations worldwide employed in this service but still their numbers are inadequate and it is even almost impossible to have such stations at difficult geographical terrains and take measurement throughout the year. Aerosol optical depth or AOD, which is a measure of extinction of incoming solar radiation, serves as proxy to atmospheric aerosol loading. Various sensors onboard different satellites take routine measurement of AOD throughout the year. Satellite based AOD is used in many studies due to their wide coverage and availability for a longer time period. Satellite measures reflected solar radiation at the top of the atmosphere. Column integrated value of aerosol are routinely estimated from those measurements using suitable inversion algorithms. MODIS instrument onboard Aqua and Terra satellites of Earth Observing System takes routine measurement in wide spectral range. We used those data to evaluate trend of AOD over almost fifty Indian cities having population more than a million. The cities we have chosen spread over almost entire length and breadth of the country. Few such studies have already been conducted using MODIS data. They typically used level 3 data. Since Level 3 data comes in 1x 1 degree gridded form they provide average value over a vast geographical region. We used level 2 dataset to enable us taking smaller region(1/2 x 1/2 degree here) centering the region of our interest . We used seasonal Mann-Kendall (M-K) statistics coupled with Sen's non-parametric slope estimation procedure to estimate monthwise and overall(i.e., yearly trend taking seasonality into account) AOD trend. We used median AOD for each month of every year to discard very high AOD's which we often get due to cloud contamination. Seasonal M-K test takes

  10. Evaluation of Terra and Aqua MODIS thermal emissive band response versus scan angle

    NASA Astrophysics Data System (ADS)

    Wenny, B. N.; Wu, A.; Madhavan, S.; Xiong, X.

    2014-10-01

    Terra and Aqua MODIS have operated near-continuously for over 14 and 12 years, respectively, and are key instruments for NASA's Earth Observing System. Observations from the 16 thermal emissive bands (TEB), covering wavelengths from 3.5 to 14.4 μm with a nadir spatial resolution of 1 km are used to regularly generate a variety of atmosphere, ocean and land science products. The TEB detectors are calibrated using scan-by-scan observations of an on-board blackbody (BB). The current response versus scan angle (RVS) of the scan mirror was derived using a spacecraft deep-space pitch maneuver for Terra MODIS and characterized during prelaunch for Aqua MODIS. Earth view (EV) data over the complete range of angles of incidence (AOI) can be used to evaluate the on-orbit performance of the TEB RVS over the mission lifetime. Three approaches for tracking the TEB RVS on-orbit using EV observations are formulated. The first approach uses the multiple daily observations of Dome C BT at different AOI and their trend relative to coincident measurements from a ground temperature sensor. The second approach uses brightness temperatures (BT) retrieved over the cloud-free ocean to derive the trends at 13 AOI over the mission lifetime. The third approach tracks the dn response (normalized to the BB AOI) across the full swath width for Antarctic granules with the Dome C site at nadir. The viability of the three approaches is assessed and the long-term stability of the TEB RVS for both MODIS instruments is determined.

  11. Fractional Snowcover Estimates from Earth Observing System (EOS) Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS)

    NASA Technical Reports Server (NTRS)

    Salomonson, Vincent V.

    2002-01-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS) on the NASA Earth Observing System (EOS) Terra and Aqua missions has shown considerable capability for mapping snowcover. The typical approach that has used, along with other criteria, the Normalized Snow Difference Index (NDSI) that takes the difference between 500 meter observations at 1.64 micrometers (MODIS band 6) and 0.555 micrometers (MODIS band 4) over the sum of these observations to determine whether MODIS pixels are snowcovered or not in mapping the extent of snowcover. For many hydrological and climate studies using remote sensing of snowcover, it is desirable to assess if the MODIS snowcover observations could not be enhanced by providing the fraction of snowcover in each MODIS observation (pixel). Pursuant to this objective studies have been conducted to assess whether there is sufficient "signal%o in the NDSI parameter to provide useful estimates of fractional snowcover in each MODIS 500 meter pixel. To accomplish this objective high spatial resolution (30 meter) Landsat snowcover observations were used and co-registered with MODIS 500 meter pixels. The NDSI approach was used to assess whether a Landsat pixel was or was not snowcovered. Then the number of snowcovered Landsat pixels within a MODIS pixel was used to determine the fraction of snowcover within each MODIS pixel. The e results were then used to develop statistical relationships between the NDSI value for each 500 meter MODIS pixel and the fraction of snowcover in the MODIS pixel. Such studies were conducted for three widely different areas covered by Landsat scenes in Alaska, Russia, and the Quebec Province in Canada. The statistical relationships indicate that a 10 percent accuracy can be attained. The variability in the statistical relationship for the three areas was found to be remarkably similar (-0.02 for mean error and less than 0.01 for mean absolute error and standard deviation). Independent tests of the relationships were

  12. Surface circulation patterns in the Gulf of California derived from MODIS Aqua 250 m

    NASA Astrophysics Data System (ADS)

    Martínez-Flores, G.; Salinas-González, F.; Gutiérrez de Velasco-Sanromán, G.; Godínez-Orta, L.

    2009-04-01

    The Gulf of California (GC) is a marginal elongated and semi-enclosed sea located at northwest of Mexico, between the Peninsula of Baja California and the mainland Mexico. The considered area average 150 km in width and 1500 km in length, from the mouth of the Colorado River to Cabo Corrientes, Jalisco. It has a maximum depth of 3600 m at the southern inlet and the northern region average 200 m in deep. The study of superficial circulation patterns in the GC is of interest because its relevance to the mechanisms of transport for distribution of a variety of materials -plankton, contaminants, microalgae, etc.- and its association with areas of sedimentary deposits, zones where there is a higher probability for fishing or related to the presence of certain species of marine life. Recent studies explain the circulation of the GC as a result of the Pacific Ocean's forcing, wind, heat fluxes on the sea surface and the interaction between the flow produced by these agents and bathymetry. The objective of this work was to obtain evidence of the patterns of surface circulation using a spatial resolution of 250 m over a period of two to seven days (depending on cloud cover), which offered images from the MODIS Level 1B. This essay is an attempt to contribute with more information to the understanding of the regional dynamics of the GC and its local influence on the zones bordering the coast. Thus, MODIS Aqua 250 m data was used, to which algorithms were applied in order to enhance the contrast of reflectance levels of these bands (0.620-0.670 and 0.841-0.876 µm) within the marine environment. The results are associated with suspended particulate matter (SPM), which we used as tracers of the surface circulation, using a sequence of images from January 2004 to December 2008. Algorithms for dust and cloud detection were used and incorporated with thermal band images, in which zones of terrigenous contribution by eolian transport were identified. Furthermore, pluvial

  13. Response versus scan-angle corrections for MODIS reflective solar bands using deep convective clouds

    NASA Astrophysics Data System (ADS)

    Bhatt, Rajendra; Angal, Amit; Doelling, David R.; Xiong, Xiaoxiong; Wu, Aisheng; Haney, Conor O.; Scarino, Benjamin R.; Gopalan, Arun

    2016-05-01

    The absolute radiometric calibration of the reflective solar bands (RSBs) of Aqua- and Terra-MODIS is performed using on-board calibrators. A solar diffuser (SD) panel along with a solar diffuser stability monitor (SDSM) system, which tracks the degradation of the SD over time, provides the baseline for calibrating the MODIS sensors. MODIS also views the moon and deep space through its space view (SV) port for lunar-based calibration and computing the background, respectively. The MODIS instrument views the Earth's surface using a two-sided scan mirror, whose reflectance is a function of the angle of incidence (AOI) and is described by response versus scan-angle (RVS). The RVS for both MODIS instruments was characterized prior to launch. MODIS also views the SD and the moon at two different AOIs. There is sufficient evidence that the RVS is changing on orbit over time and as a function of wavelength. The SD and lunar observation scans can only track the RVS variation at two AOIs. Consequently, the MODIS Characterization Support Team (MCST) developed enhanced approaches that supplement the onboard calibrator measurements with responses from the pseudo-invariant desert sites. This approach has been implemented in Level 1B (L1B) Collection 6 (C6) for select short-wavelength bands. This paper presents an alternative approach of characterizing the mirror RVS to derive the time-dependent RVS correction factors for MODIS RSBs using tropical deep convective cloud (DCC) targets. An initial assessment of the DCC response from Aqua-MODIS band 1 C6 data indicates evidence of RVS artifacts, which are not uniform across the scans and are more prevalent at the beginning of the earth-view scan.

  14. Characterization of MODIS mirror side difference in the reflective solar spectral region

    NASA Astrophysics Data System (ADS)

    Geng, X.; Angal, A.; Sun, J.; Wu, A.; Choi, T.; Xiong, X.

    2011-10-01

    The MODIS instruments onboard the Terra and Aqua spacecraft, launched in December 1999 and May 2002, respectively, have successfully operated through the present time. MODIS collects the Earth view (EV) data via a twosided paddle wheel scan mirror at angles of incidence (AOI) from 10.5 to 65.5 degrees. Reflective properties between the two mirror sides are not identical with large differences seen in Terra MODIS reflective solar bands (RSB). This paper describes a methodology to calculate and monitor MODIS RSB mirror side differences using EV observations. The longterm trends of response differences between two mirror sides are evaluated using different EV targets. Results show that the on-orbit changes in the properties of the scan mirror are wavelength and AOI dependent with large mirror side differences observed at shorter wavelengths in larger AOI. Starting from 2005, the mirror side difference has gradually exhibited a seasonally dependent feature in Terra MODIS visible spectral bands, which is mainly due to the changes in the scan mirror polarization property. In addition to fully characterizing on-orbit changes of the MODIS scan mirror properties, results and discussions provided in this paper will help clarify their impacts on the Level 1B data products and support future efforts to maintain MODIS data quality.

  15. The NASA Earth Observing System (EOS) Terra and Aqua Mission Moderate Resolution Imaging Spectroradiometer (MODIS: Science and Applications

    NASA Technical Reports Server (NTRS)

    Salomnson, Vincent V.

    2003-01-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS) on the Earth Observing System (EOS) Terra Mission began to produce data in February 2000. The EOS Aqua mission was launched successfully May 4,2002 with another MODIS on it and "first light" observations occurred on June 24,2002. The Terra MODIS is in a sun-synchronous orbit going north to south in the daylight portion of the orbit crossing the equator at about 1030 hours local time. The Aqua spacecraft operates in a sun-synchronous orbit going south to north in the daylight portion of the orbit crossing the equator at approximately 1330 hours local time. The spacecraft, instrument, and data systems for both MODIS instruments are performing well and are producing a wide variety of data products useful for scientific and applications studies in relatively consistent fashion extending from November 2000 to the present. Within the approximately 40 MODIS data products, several are new and represent powerful and exciting capabilities such the ability to provide observations over the globe of fire occurrences, microphysical properties of clouds and sun-stimulated fluorescence from phytoplankton in the surface waters of the ocean. The remainder of the MODIS products exceeds or, at a minimum, matches the capabilities of products from heritage sensors such as, for example, the Advanced Very High Resolution Radiometer (AVHRR). Efforts are underway to provide data sets for the greater Earth science community and to improve access to these products at the various Distributed Active Archive Centers (DAAC's) or through Direct Broadcast (DB) stations.

  16. Progress on alternative method of the on-orbit RVS characterization for MODIS reflective solar bands

    NASA Astrophysics Data System (ADS)

    Chen, H.; Xiong, X.; Angal, A.; Geng, X.; Wu, A.

    2014-09-01

    MODIS Reflective Solar Bands (RSB) are calibrated on-orbit using its onboard calibrators, including a Solar Diffuser (SD), a Solar Diffuser Stability Monitor (SDSM), and a Spectroradiometric Calibration Assembly (SRCA). A Space View (SV) port is used to provide a background reference, and also facilitate near monthly lunar observations via a spacecraft roll. In every scan, the earth's surface, SV and onboard calibrators are viewed via a two sided scan mirror, whose reflectance depends on the angles of the incidence (AOI) as well as the wavelength of the incident light. Response versus Scan angle (RVS) is defined as a dependence function of the scan mirror's reflectance over AOI. An initial RVS for each RSB was measured prelaunch for both Terra and Aqua MODIS. Algorithms have been developed to track the on-orbit RVS variation using the measurements from the onboard calibrators, supplemented with the Earth View (EV) response from pseudo-invariant desert targets obtained at different AOI. The current approach, as implemented in Collection 6 (C6), uses EV responses from the Libyan desert sites to track the on-orbit RVS change. It strongly depends on the long-term temporal stability of the desert sites. As an effort to validate and, if necessary, to improve MODIS RSB RVS characterization for future applications, the MODIS Characterization Support Team (MCST) has developed and tested an alternative approach to monitor the on-orbit RVS change, using a response from a single desert site. The purpose of using data from one site is to avoid the impact of possible differences in the long-term temporal stability among multiple sites on the calculation of the on-orbit RVS. This paper updates recent progress in the formulation of the alternative RVS approach. Comprehensive comparisons were also performed with current C6 RVS results for both Terra and Aqua MODIS. Results demonstrate that this alternative method provides a supplemental means to track the on-orbit RVS for MODIS RSB.

  17. Effect of MODIS Terra Radiometric Calibration Improvements on Collection 6 Deep Blue Aerosol Products: Validation and Terra/Aqua Consistency

    NASA Technical Reports Server (NTRS)

    Sayer, A. M.; Hsu, N. C.; Bettenhausen, C.; Jeong, M.-J.; Meister, G.

    2015-01-01

    The Deep Blue (DB) algorithm's primary data product is midvisible aerosol optical depth (AOD). DB applied to Moderate Resolution Imaging Spectroradiometer (MODIS) measurements provides a data record since early 2000 for MODIS Terra and mid-2002 for MODIS Aqua. In the previous data version (Collection 5, C5), DB production from Terra was halted in 2007 due to sensor degradation; the new Collection 6 (C6) has both improved science algorithms and sensor radiometric calibration. This includes additional calibration corrections developed by the Ocean Biology Processing Group to address MODIS Terra's gain, polarization sensitivity, and detector response versus scan angle, meaning DB can now be applied to the whole Terra record. Through validation with Aerosol Robotic Network (AERONET) data, it is shown that the C6 DB Terra AOD quality is stable throughout the mission to date. Compared to the C5 calibration, in recent years the RMS error compared to AERONET is smaller by approximately 0.04 over bright (e.g., desert) and approximately 0.01-0.02 over darker (e.g., vegetated) land surfaces, and the fraction of points in agreement with AERONET within expected retrieval uncertainty higher by approximately 10% and approximately 5%, respectively. Comparisons to the Aqua C6 time series reveal a high level of correspondence between the two MODIS DB data records, with a small positive (Terra-Aqua) average AOD offset <0.01. The analysis demonstrates both the efficacy of the new radiometric calibration efforts and that the C6 MODIS Terra DB AOD data remain stable (to better than 0.01 AOD) throughout the mission to date, suitable for quantitative scientific analyses.

  18. Effect of MODIS Terra radiometric calibration improvements on Collection 6 Deep Blue aerosol products: Validation and Terra/Aqua consistency

    NASA Astrophysics Data System (ADS)

    Sayer, A. M.; Hsu, N. C.; Bettenhausen, C.; Jeong, M.-J.; Meister, G.

    2015-12-01

    The Deep Blue (DB) algorithm's primary data product is midvisible aerosol optical depth (AOD). DB applied to Moderate Resolution Imaging Spectroradiometer (MODIS) measurements provides a data record since early 2000 for MODIS Terra and mid-2002 for MODIS Aqua. In the previous data version (Collection 5, C5), DB production from Terra was halted in 2007 due to sensor degradation; the new Collection 6 (C6) has both improved science algorithms and sensor radiometric calibration. This includes additional calibration corrections developed by the Ocean Biology Processing Group to address MODIS Terra's gain, polarization sensitivity, and detector response versus scan angle, meaning DB can now be applied to the whole Terra record. Through validation with Aerosol Robotic Network (AERONET) data, it is shown that the C6 DB Terra AOD quality is stable throughout the mission to date. Compared to the C5 calibration, in recent years the RMS error compared to AERONET is smaller by ˜0.04 over bright (e.g., desert) and ˜0.01-0.02 over darker (e.g., vegetated) land surfaces, and the fraction of points in agreement with AERONET within expected retrieval uncertainty higher by ˜10% and ˜5%, respectively. Comparisons to the Aqua C6 time series reveal a high level of correspondence between the two MODIS DB data records, with a small positive (Terra-Aqua) average AOD offset <0.01. The analysis demonstrates both the efficacy of the new radiometric calibration efforts and that the C6 MODIS Terra DB AOD data remain stable (to better than 0.01 AOD) throughout the mission to date, suitable for quantitative scientific analyses.

  19. The Characterization of Deep Convective Cloud Albedo as a Calibration Target Using MODIS Reflectances

    NASA Technical Reports Server (NTRS)

    Doelling, David R.; Hong, Gang; Morstad, Daniel; Bhatt, Rajendra; Gopalan, Arun; Xiong, Jack

    2010-01-01

    There are over 25 years of historical satellite data available to climate analysis. The historical satellite data needs to be well calibrated, especially in the visible, where there is no onboard calibration on operational satellites. The key to the vicarious calibration of historical satellites relies on invariant targets, such as the moon, Dome C, and deserts. Deep convective clouds (DCC) also show promise of being a stable invariant or predictable target viewable by all satellites, since they behave as solar diffusers. However DCC have not been well characterized for calibration. Ten years of well-calibrated MODIS is now available. DCC can easily be identified using IR thresholds, where the IR calibration can be traced to the onboard black-bodies. The natural variability of DCC albedo will be analyzed geographically and seasonally, especially difference of convection initiated over land or ocean. Functionality between particle size and ozone absorption with DCC albedo will be examined. Although DCC clouds are nearly Lambertion, the angular distribution of reflectances will be sampled and compared with theoretical models. Both Aqua and Terra MODIS DCC angular models will be compared for consistency. Normalizing angular geostationary DCC reflectances, which were calibrated against MODIS, with SCIAMACHY spectral reflectances and comparing them to MODIS DCC reflectances will inspect the usage of DCC albedos as an absolute calibration target.

  20. Use of spaceborne lidar for the evaluation of thin cirrus contamination and screening in the Aqua MODIS Collection 5 aerosol products

    NASA Astrophysics Data System (ADS)

    Huang, Jingfeng; Hsu, N. Christina; Tsay, Si-Chee; Liu, Zhaoyan; Jeong, Myeong-Jae; Hansell, Richard A.; Lee, Jaehwa

    2013-06-01

    Cloud contamination from subvisual thin cirrus clouds is still a challenging issue for operational satellite aerosol retrievals. In the A-Train constellation, concurrent high-sensitivity cirrus observations from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) provide us with an unprecedented opportunity to examine the susceptibility of the Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol retrievals to thin cirrus contamination and to evaluate the robustness of various cirrus screening techniques. Quantitative evaluations indicate that the current cirrus screening schemes in the MODIS Dark Target and Deep Blue Collection 5 aerosol retrievals can effectively remove most cirrus signals while some residual thin cirrus signals still exist with strong spatial and seasonal variability. Results also show significant linkage between thin cirrus occurrence frequency and the susceptibility of aerosol retrievals to thin cirrus contamination. Using the CALIPSO cirrus observations as a reference, we also examined the effectiveness and robustness of eight MODIS-derived cirrus screening parameters. These parameters include apparent reflectance at 1.38 µm (R1.38), cirrus reflectance at 0.66 µm (CR0.66), CR0.66 cirrus flag (CF), reflectance ratio between 1.38 µm and 0.66 µm (RR1.38/0.66), reflectance ratio between 1.38 µm and 1.24 µm (RR1.38/1.24), brightness temperature difference between 8.6 µm and 11 µm (BTD8.6-11), brightness temperature difference between 11 µm and 12 µm (BTD11-12), and cloud phase infrared approach (CPIR). Among these parameters, RR1.38/0.66 achieves the best overall performance, followed by the BTD11-12. Results from several test cases suggest that the cirrus screening schemes in the operational MODIS aerosol retrieval algorithms can be further improved to reduce thin cirrus contamination.

  1. Tracking daily land surface albedo and reflectance anisotropy with moderate-resolution imaging spectroradiometer (MODIS)

    NASA Astrophysics Data System (ADS)

    Shuai, Yanmin

    A new algorithm provides daily values of land surface albedo and angular reflectance at a 500-m spatial resolution using data from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments currently in orbit on NASA's Terra and Aqua satellite platforms. To overcome the day-to-day variance in observed surface reflectance induced by differences in view and solar illumination angles, the algorithm uses the RossThickLiSparse-Reciprocal bidirectional reflectance model, which is fitted to all MODIS observations of a 500-m resolution cell acquired during a 16-day moving window. Individual observations are weighted by their quality, observation coverage, and proximity to the production date of interest. Product quality is measured by (1) the root mean square error (RMSE) of observations against the best model fit; and (2) the ability of the angular sampling pattern of the observations at hand to determine reflectance model parameters accurately. A regional analysis of model fits to data from selected MODIS data tiles establishes the bounds of these quality measures for application in the daily algorithm. The algorithm, which is now available to users of direct broadcast satellite data from MODIS, allows daily monitoring of rapid surface radiation and land surface change phenomena such as crop development and forest foliage cycles. In two demonstrations, the daily algorithm captured rapid change in plant phenology. The growth phases of a winter wheat crop, as monitored at the Yucheng agricultural research station in Yucheng, China, matched MODIS daily multispectral reflectance data very well, especially during the flowering and heading stages. The daily algorithm also captured the daily change in autumn leaf color in New England, documenting the ability of the algorithm to work well over large regions with varying degrees of cloud cover and atmospheric conditions. Daily surface albedos measured using ground-based instruments on towers at the agricultural and

  2. Spatial and Temporal Characteristics of Aerosols from Collection 6 Aqua and Terra MODIS e-Deep Blue Products

    NASA Astrophysics Data System (ADS)

    Bettenhausen, C.; Hsu, N. Y. C.; Sayer, A. M.; Lee, J.; Carletta, N.

    2015-12-01

    Aerosols continue to attract a significant amount of attention from researchers worldwide due to their extensive effects on Earth's climate, ecology, public health, and even energy production. In order to truly understand these effects, a long, stable, and well-calibrated data record is required. Since 2000 and 2002, the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments aboard the Terra and Aqua satellites together with the e-Deep Blue aerosol retrieval algorithm have been providing such a data record. After a multi-year development effort, the production of both Aqua and Terra MODIS Collection 6 (C6) atmosphere products successfully completed earlier this year and the data was released to the public shortly thereafter. The C6 Deep Blue products (now enhanced Deep Blue or e-Deep Blue) have been significantly improved over the previous Collection 5.1 version. In this poster we provide an overview of the latest C6 e-Deep Blue products and the improvements implemented since the previous collection including coverage over dark surfaces and updates to the Terra calibration. Validation results utilizing Aerosol Robotic Network (AERONET) data are also summarized. We then use the C6 e-Deep Blue products from both Aqua and Terra to explore the spatial characteristics in addition to the seasonal and inter-annual variability of aerosols on both regional and global scales. We also use this as an opportunity to compare these results and investigate any differences found between the two instruments.

  3. Modeling and Mapping Oyster Norovirus Outbreak Risks in Gulf of Mexico Using NASA MODIS Aqua Data

    NASA Astrophysics Data System (ADS)

    Deng, Z.; Wang, J.

    2015-12-01

    Norovirus is a highly infectious virus and the leading cause of foodborne disease outbreaks such as oyster norovirus outbreaks. Currently, there is no vaccine to prevent norovirus infection and no drug to treat it. This paper presents an integrated modeling and mapping framework for predicting the risk of norovirus outbreaks in oyster harvesting waters in the Northern Gulf of Mexico coast. The framework involves (1) the construction of three novel remote sensing algorithms for the retrieval of sea surface salinity, sea surface temperature, and gage height (tide level) using NASA MODIS Aqua data; (2) the development of probability-based Artificial Neural Network (ANN) model for the prediction of oyster norovirus outbreak risk, and (3) the application of the Local Indicators of Spatial Association (LISA) for mapping norovirus outbreak risks in oyster harvesting areas in the Northern Gulf of Mexico using the remotely sensed NASA data, retrieved data from the three remote sensing algorithms, and the ANN model predictions. The three remote sensing algorithms are able to correctly retrieve 94.1% of sea surface salinity, 94.0% of sea surface temperature, and 77.8% of gage height observed along the US coast, including the Pacific coast, the Gulf of Mexico coast, and the Atlantic coast. The gage height, temperature, and salinity are the three most important explanatory variables of the ANN model in terms of spatially distributed input variables. The ANN model is capable of hindcasting/predicting all oyster norovirus outbreaks occurred in oyster growing areas along the Gulf of Mexico coast where environmental data are available. The integrated modeling and mapping framework makes it possible to map daily risks of norovirus outbreaks in all oyster harvesting waters and particularly the oyster growing areas where no in-situ environmental data are available, greatly improving the safety of seafood and reducing outbreaks of foodborne disease.

  4. Monitoring ice break-up on the Mackenzie River, Canada, from MODIS Aqua and Terra observations

    NASA Astrophysics Data System (ADS)

    Muhammad, P.; Duguay, C. R.; Kang, K.

    2013-12-01

    Monitoring the response of river ice phenology to variability and changes in high-latitude climate conditions is critical for improving our understanding of northern hydrology and related impacts on geochemical and biological processes. Shorter ice cover duration, thinner ice, and earlier break-up also influence the winter road season, thereby influencing industrial development and the delivery of goods to northern communities. Increased upstream temperatures over the Mackenzie River Basin have caused shorter ice cover seasons, consequently changing the timing and severity of river ice flow in this high-latitude region. This study involves the analysis of Moderate Resolution Imaging Spectroradiometer (MODIS) Level 3 500-m snow products (Aqua and Terra), complemented with 250-m Level 1b data, to monitor ice cover during the break-up period on the Mackenzie River over the 2001-2013 period. Results from the analysis of 10 ice seasons (2003-2012) show that first day ice-off was observed between day of year (DY) 115-125 and ended between DY 145-155, resulting in average melt durations of about 30-40 days. Additional ice-on and ice-off days observed during 2003-2012 resulted from northern flowing entrained river ice that extended the break-up season until DY 155-163. Floating ice flowing northbound could therefore generate multiple periods of ice-cover and ice-free days at the same geographic location. During the ice break-up seasons from 2003-2012, ice melt was initiated by in situ melt over drainage basin (thermodynamic), especially between 61-62o N. However, ice break-up above the 62o N was more dynamically driven. In addition, ice jams were found to be largely controlled by river morphology.

  5. MODIS-Aqua detects Noctiluca scintillans and hotspots in the central Arabian Sea.

    PubMed

    Dwivedi, R; Priyaja, P; Rafeeq, M; Sudhakar, M

    2016-01-01

    Northern Arabian Sea is considered as an ecologically sensitive area as it experiences a massive upwelling and long-lasting algal bloom, Noctiluca scintillans (green tide) during summer and spring-winter, respectively. Diatom bloom is also found to be co-located with N. scintillans and both have an impact on ecology of the basin. In-house technique of detecting species of these blooms from Moderate Resolution Imaging Spectroradiometer (MODIS)-Aqua data was used to generate a time-series of images revealing their spatial distribution. A study of spatial-temporal variability of these blooms using satellite data expressed a cyclic pattern of their spread over a period of 13 years. An average distribution of the blooms for January-March period revealed a peak in 2015 and minimum in 2013. Subsequently, a time-series of phytoplankton species images were generated for these 2 years to study their inter-annual variability and the associated factors. Species images during active phase of the bloom (February) in 2015 indicated development of N. scintillans and diatom in the central Arabian Sea also, up to 12° N. This observation was substantiated with relevant oceanic parameters measured from the ship as well as satellite data and the same is highlight of the paper. While oxygen depletion and release of ammonia associated with N. scintillans are detrimental for waters on the western side; it is relatively less extreme and supports the entire food chain on the eastern side. In view of these contrasting eco-sensitive events, it is a matter of concern to identify biologically active persistent areas, hot spots, in order to study their ecology in detail. An ecological index, persistence of the bloom, was derived from the time-series of species images and it is another highlight of our study. PMID:26690080

  6. Relative spectral response corrected calibration inter-comparison of S-NPP VIIRS and Aqua MODIS thermal emissive bands

    NASA Astrophysics Data System (ADS)

    Efremova, Boryana; Wu, Aisheng; Xiong, Xiaoxiong

    2014-09-01

    The S-NPP Visible Infrared Imaging Radiometer Suite (VIIRS) instrument is built with strong heritage from EOS MODIS, and has very similar thermal emissive bands (TEB) calibration algorithm and on-board calibrating source - a V-grooved blackbody. The calibration of the two instruments can be assessed by comparing the brightness temperatures retrieved from VIIRS and Aqua MODIS simultaneous nadir observations (SNO) from their spectrally matched TEB. However, even though the VIIRS and MODIS bands are similar there are still relative spectral response (RSR) differences and thus some differences in the retrieved brightness temperatures are expected. The differences depend on both the type and the temperature of the observed scene, and contribute to the bias and the scatter of the comparison. In this paper we use S-NPP Cross-track Infrared Sounder (CrIS) data taken simultaneously with the VIIRS data to derive a correction for the slightly different spectral coverage of VIIRS and MODIS TEB bands. An attempt to correct for RSR differences is also made using MODTRAN models, computed with physical parameters appropriate for each scene, and compared to the value derived from actual CrIS spectra. After applying the CrIS-based correction for RSR differences we see an excellent agreement between the VIIRS and Aqua MODIS measurements in the studied band pairs M13-B23, M15-B31, and M16- B32. The agreement is better than the VIIRS uncertainty at cold scenes, and improves with increasing scene temperature up to about 290K.

  7. Time-Dependent Response Versus Scan Angle for MODIS Reflective Solar Bands

    NASA Technical Reports Server (NTRS)

    Sun, Junqiang; Xiong, Xiaoxiong; Angal, Amit; Chen, Hongda; Wu, Aisheng; Geng, Xu

    2014-01-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS) instruments currently operate onboard the National Aeronautics and Space Administration (NASA's) Terra and Aqua spacecraft, launched on December 18, 1999 and May 4, 2002, respectively. MODIS has 36 spectral bands, among which 20 are reflective solar bands (RSBs) covering a spectral range from 0.412 to 2.13 µm. The RSBs are calibrated on orbit using a solar diffuser (SD) and an SD stability monitor and with additional measurements from lunar observations via a space view (SV) port. Selected pseudo-invariant desert sites are also used to track the RSB on-orbit gain change, particularly for short-wavelength bands. MODIS views the Earth surface, SV, and the onboard calibrators using a two-sided scan mirror. The response versus scan angle (RVS) of the scan mirror was characterized prior to launch, and its changes are tracked using observations made at different angles of incidence from onboard SD, lunar, and Earth view (EV) measurements. These observations show that the optical properties of the scan mirror have experienced large wavelength-dependent degradation in both the visible and near infrared spectral regions. Algorithms have been developed to track the on-orbit RVS change using the calibrators and the selected desert sites. These algorithms have been applied to both Terra and Aqua MODIS Level 1B (L1B) to improve the EV data accuracy since L1B Collection 4, refined in Collection 5, and further improved in the latest Collection 6 (C6). In C6, two approaches have been used to derive the time-dependent RVS for MODIS RSB. The first approach relies on data collected from sensor onboard calibrators and mirror side ratios from EV observations. The second approach uses onboard calibrators and EV response trending from selected desert sites. This approach is mainly used for the bands with much larger changes in their time-dependent RVS, such as the Terra MODIS bands 1-4, 8, and 9 and the Aqua MODIS bands 8- and 9

  8. MODIS On-orbit Spectral Calibration for the Reflective Solar Bands

    NASA Technical Reports Server (NTRS)

    Xiong, X.; Che, N.; Barnes, W.

    2004-01-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS) makes observations in 36 spectral bands with wavelengths from 0.41 to 14.5 microns. The bands with center wavelengths below 2.2 microns are referred as the reflective solar bands (RSB) with their radiometric calibration performed by a solar diffuser (SD) and a solar diffuser stability monitor (SDSM). This paper focuses on the MODIS spectral calibration performed by its unique on-board calibrator (OBC): the Spectro-Radiometric Calibration Assembly (SRCA). When operated in the spectral mode, the SRCA acts as a monochromator with internal spherical integration source (SIS) that measures the spectral responses for all the reflective solar bands. A wavelength calibrator, a didymium filter with known spectral profile, is utilized to calibrate the wavelength scale for the grating positions during each SRCA spectral calibration activity. The capability of self-wavelength calibration allows the SRCA to track the center wavelength shifts and to monitor the spectral response changes throughout the instruments lifetime. The MODIS spectral calibration, same for both Terra and Aqua missions, is performed every three months on-orbit. An overview of MODIS spectral characterization approach and a summary of the on-orbit results will be presented in this paper.

  9. The regime of aerosol optical depth over Central Asia based on MODIS Aqua Deep Blue data

    NASA Astrophysics Data System (ADS)

    Floutsi, Athina; KorrasCarraca, Marios; Matsoukas, Christos; Biskos, George

    2015-04-01

    Atmospheric aerosols, both natural and anthropogenic, can affect the regional and global climate through their direct, indirect, and semi-direct effects on the radiative energy budget of the Earth-atmosphere system. To quantify these effects it is therefore important to determine the aerosol load, and an effective way to do that is by measuring the aerosol optical depth (AOD). In this study we investigate the spatial and temporal variability of the AOD over the climatically sensitive region of Central Asia (36° N - 50° N, 46° E - 75° E), which has significant sources of both natural and anthropogenic particles. The primary source of anthropogenic particles is fossil fuel combustion occurring mainly at oil refineries in the Caspian Sea basin. Natural particles originate mostly from the two deserts in the region (namely Kara-Kum and Kyzyl-Kum), where persistent dust activity is observed. Another source is the Aral Sea region, which due to its phenomenal desertification also drives an intense salt and dust transport from the exposed sea-bed to the surrounding regions. This transport is of particular interest because of health-hazardous materials contained in the Aral Sea sea-bed. For our analysis we use Level-3 daily MODIS - Aqua Dark Target - Deep Blue combined product, from the latest MODIS collection (006), available in 1° x 1° resolution (about 100 km x 100 km) over the period 2002-2014.Our first results indicate a significant spatial variability of the aerosol load over the study region. The data also show a clear seasonal cycle, with large aerosol load being associated with strong dust activity during spring and summer (AOD up to 0.5), and low during autumn and winter (AOD up to 0.4). In spring and summer significant aerosol load is observed in the Garabogazköl basin, Northeast and South-southeast Caspian Sea (offshore North Iran and Azerbaijan), as well as southwest of the Aral Sea. In the later region, the high AOD values can be explained by export of

  10. Aerosol optical depth over central north Asia based on MODIS-Aqua data

    NASA Astrophysics Data System (ADS)

    Avgousta Foutsi, Athina; Korras Carraca, Marios Bruno; Matsoukas, Christos; Biskos, George

    2016-04-01

    Atmospheric aerosols, both natural and anthropogenic, can affect the regional and global climate through their direct, indirect, and semi-direct effects on the radiative energy budget of the Earth-atmosphere system. To quantify these effects it is important to determine the aerosol load, and an effective way to do that is by measuring the aerosol optical depth (AOD). The central Asia region (mainly the Caspian and Aral sea basins), the arid and semi-arid regions of Western China as well as Siberia are of great interest due to the significant natural sources of mineral aerosols originating from local deserts and biomass burning from wildfires in boreal forests. What is of particular interest in the region is the phenomenal shrinking and desertification of the Aral Sea that drives an intense salt and dust transport from the exposed sea-bed to the surrounding regions with important implications in regional air quality. Anthropogenic particles are also observed due to fossil-fuel combustion occurring mainly at oil refineries in the Caspian Sea basin. Here we investigate the spatial and temporal variability of the AOD at 550 nm over central Asia, Siberia and western China, in the region located between 35° N - 65° N and 45° E - 110° E. For our analysis we use Level-3 daily MODIS - Aqua Dark Target - Deep Blue combined product, from the latest collection (006), available in a 1°×1° resolution (ca. 100 km × 100 km) over the period 2002-2014. Our results indicate a significant spatial variability of the aerosol load over the study region. The highest AODs are observed over the Aral Sea year-round, with extreme values reaching 2.1 during July. In the rest of our study region a clear seasonal cycle with highest AOD values (up to 1.2 over the Taklamakan Desert) during spring and summer is observed. The arid parts of central north Asia are characterized by larger aerosol loads during spring, lower but still high AOD in summer and much lower values in autumn and spring

  11. Degradation of MODIS Optics and its Reflective Solar Bands Calibration

    NASA Technical Reports Server (NTRS)

    Xiong, X.; Sun, J.; Esposito, J.; Pan, C.; Xiong, S.; Guenther, B.; Barnes, W. L.; Degnan, John (Technical Monitor)

    2001-01-01

    The MODerate Resolution Imaging Spectroradiometer (MODIS) has 36 spectral bands with wavelength ranging from 0.41 micron to 14.5 micron and spatial resolution between 0.25, 0.5, and 1.0 km at Nadir. Its ProtoFlight Model (PFM) on the NASA EOS Terra spacecraft has been providing global coverage of the Land, Ocean, and Atmosphere for the science community since the instrument opened its Nadir door on 24 February 2000. The MODIS optical system consists of a 2-sided paddle wheel scan mirror, a fold mirror, a primary mirror, and other aft optics. The sensor's 20 reflective solar bands from 0.41 to 2.1 micron are calibrated on-orbit by a solar diffuser (SD) and a solar diffuser stability monitor (SDSM). In addition to SD, degradation of the MODIS optics in the reflective solar bands has been observed, including variations in degradation between the two sides of the MODIS scan mirror. During MODIS first year of on-orbit operation, the overall degradations at the shortest wavelength (0.41 micron) are about 3% for SD, and in excess of 10% for the MODIS system. In this paper, we will present our degradation analysis results and discuss their impact on the reflective solar bands' on-orbit calibration.

  12. An Assessment of Diurnal and Seasonal Cloud Cover Changes Over the Hawaiian Islands Using Terra and Aqua MODIS

    NASA Astrophysics Data System (ADS)

    Barnes, M.; Miura, T.; Giambelluca, T. W.; Chen, Q.

    2012-12-01

    To date, there has not yet been a spatial and temporal analysis of cloud cover over the Hawaiian Islands using high spatial resolution data. An understanding of patterns in cloud cover is essential to analyzing and understanding atmospheric and hydrologic processes, including evapotranspiration. The MODIS instruments aboard the Terra and Aqua satellites provide observations with the high spatial resolution necessary to determine patterns of cloud cover over the Hawaiian Islands. The objective of this study was to determine how spatial patterns of cloudiness change diurnally and seasonally over the Hawaiian Islands using high resolution cloud cover data generated from the Terra and Aqua MODIS satellite sensors. The MODIS cloud mask products (MOD35 and MYD35) were obtained for the entire MODIS time series over the major Hawaiian Islands. Monthly statistics including mean cloud cover probability at the daytime and nighttime overpasses for each instrument were generated from the daily MOD35 and MYD35 cloudiness time series. The derived monthly statistics for January and June (the wet and dry season, respectively) were analyzed for diurnal (morning vs. afternoon and late evening vs. early morning) changes in total amount and spatial patterns of cloudiness. They were also compared to analyze seasonal changes in cloudiness. Cloud probability generally increased with elevation until the elevation of the inversion layer. The lowest cloud cover probability was observed above the inversion layer on the islands of Maui and Hawaii. This elevational gradient varied in relation to the facings of slopes; cloud cover probability was higher on the windward (northeastern) sides than on the leeward (southwestern) sides of the mountains. Both morning and afternoon observations indicate that the Hawaiian Islands were cloudier in June than in January. This is the opposite of what we might expect as January is in the wet season and June is in the dry season. Both late evening and early

  13. Land Surface Albedo from MERIS Reflectances Using MODIS Directional Factors

    NASA Technical Reports Server (NTRS)

    Schaaf, Crystal L. B.; Gao, Feng; Strahler, Alan H.

    2004-01-01

    MERIS Level 2 surface reflectance products are now available to the scientific community. This paper demonstrates the production of MERIS-derived surface albedo and Nadir Bidirectional Reflectance Distribution Function (BRDF) adjusted reflectances by coupling the MERIS data with MODIS BRDF products. Initial efforts rely on the specification of surface anisotropy as provided by the global MODIS BRDF product for a first guess of the shape of the BRDF and then make use all of the coincidently available, partially atmospherically corrected, cloud cleared, MERIS observations to generate MERIS-derived BRDF and surface albedo quantities for each location. Comparisons between MODIS (aerosol-corrected) and MERIS (not-yet aerosol-corrected) surface values from April and May 2003 are also presented for case studies in Spain and California as well as preliminary comparisons with field data from the Devil's Rock Surfrad/BSRN site.

  14. Radiance validation of the solar reflective bands of MODIS

    NASA Astrophysics Data System (ADS)

    Thome, K.

    The Moderate Resolution Imaging Spectroradiometer (MODIS) is a key sensor onboard NASA's Terra platform launched in 1999. An important aspect of the use of MODIS, and other Terra sensors, has been the characterization and calibration of the sensors and validation of their data products. The Remote Sensing Group at the University of Arizona has been active in this area through the use of ground-based test sites for the radiance validation of MODIS. This paper presents the results from this work using the Railroad Valley Playa test site in Nevada. The paper describes the test site that is now used in the radiance validation and calibration of at least 10 current airborne and satellite based sensors. Two methods are described for the- radiance validation of MODIS. The first relies on ground-based measurements of atmospheric and surface parameters to predict the at -sensor radiance of MODIS. The key to the approach is the measurement of surface reflectance over a 1 km' area of- the playa and results from this method show agreement with MODIS to better than 7%. The second method is a cross-comparison approach to other sensors with footprint sizes and sensor geometries that differ from MODIS. This calibration takes into account the changes in solar zenith and sensor view angle due to any time separation between the sensors as well as spectral differences between the sensors. Early results show that MODIS and ETM+ agree to better than 5% in the solar reflective for bands not affected by atmospheric absorption. The comparisons have also been used to indicate differences in excess of the calibration uncertainties of several other sensors. The paper concludes with an accuracy assessment of the two approaches indicating that cross-comparisons with precision better than 3% can be achieved.

  15. Characterization of turbidity in Florida's Lake Okeechobee and Caloosahatchee and St. Lucie estuaries using MODIS-Aqua measurements.

    PubMed

    Wang, Menghua; Nim, Carl J; Son, Seunghyun; Shi, Wei

    2012-10-15

    This paper describes the use of ocean color remote sensing data from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Aqua satellite to characterize turbidity in Lake Okeechobee and its primary drainage basins, the Caloosahatchee and St. Lucie estuaries from 2002 to 2010. Drainage modification and agricultural development in southern Florida transport sediments and nutrients from watershed agricultural areas to Lake Okeechobee. As a result of development around Lake Okeechobee and the estuaries that are connected to Lake Okeechobee, estuarine conditions have also been adversely impacted, resulting in salinity and nutrient fluctuations. The measurement of water turbidity in lacustrine and estuarine ecosystems allows researchers to understand important factors such as light limitation and the potential release of nutrients from re-suspended sediments. Based on a strong correlation between water turbidity and normalized water-leaving radiance at the near-infrared (NIR) band (nL(w)(869)), a new satellite water turbidity algorithm has been developed for Lake Okeechobee. This study has shown important applications with satellite-measured nL(w)(869) data for water quality monitoring and measurements for turbid inland lakes. MODIS-Aqua-measured water property data are derived using the shortwave infrared (SWIR)-based atmospheric correction algorithm in order to remotely obtain synoptic turbidity data in Lake Okeechobee and normalized water-leaving radiance using the red band (nL(w)(645)) in the Caloosahatchee and St. Lucie estuaries. We found varied, but distinct seasonal, spatial, and event driven turbidity trends in Lake Okeechobee and the Caloosahatchee and St. Lucie estuary regions. Wind waves and hurricanes have the largest influence on turbidity trends in Lake Okeechobee, while tides, currents, wind waves, and hurricanes influence the Caloosahatchee and St. Lucie estuarine areas. PMID:22858282

  16. Ocean Color Data at the Goddard Earth Sciences (GES) DAAC: CZCS, SeaWiFS, OCTS, MODIS-Terra, MODIS-Aqua

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Goddard Earth Sciences Distributed Active Archive Center (DAAC) is the designated archive for all of the ocean color data produced by NASA satellite missions. The DAAC is a long-term, high volume, secure repository for many different kinds of environmental data. With respect to ocean color, the Goddard DAAC holds all the data obtained during the eight-year mission of the Coastal Zone Color Scanner (CZCS). The DAAC is currently receiving data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), and the MODIS-Terra instrument. The DAAC recently received reformatted data from the Ocean Color and Temperature Scanner (OCTS) and will also archive MODIS-Aqua Ocean products. In addition to its archive and distribution services, the Goddard DAAC strives to improve data access, ease-of-use, and data applicability for a broad spectrum of customers. The DAAC's data support teams practice dual roles, both insuring the integrity of the DAAC data archive and serving the user community with answers to user inquiries, online and print documentation, and customized data services.

  17. Trend Analysis of global AOT based on various Polar Orbiting Satellite Observations: MODIS (Terra), MISR (Terra), SeaWiFS (OrbView-2), and MODIS (Aqua)

    NASA Astrophysics Data System (ADS)

    Yoon, J.; Vountas, M.; von Hoyningen-Huene, W.; Chang, D. Y.; Burrows, J. P.

    2012-04-01

    Many studies have investigated temporal trends of cloud-free AOTs derived from polar orbiting satellite observations since aerosol retrieval accuracy has been improved substantially. However, only few studies have discussed the fundamental limitation of incomplete sampling originated from frequent cloud disturbance and restricted temporal coverage. Furthermore, the AOT trends derived from various polar orbiting satellite observations are hardly comparable due to different sensor calibration, retrieval accuracy, and cloud screening. Therefore, the present paper integrates various analyses of AOT trends derived from multiple observations (i.e. MODIS-Terra (MOD) from 2000/03 to 2009/12, MISR-Terra (MIS) from 2000/03 to 2010/12, SeaWiFS-OrbView-2 (SEA) from 1998/01 to 2007/12, and MODIS-Aqua (MYD) from 2003/01 to 2008/12) using a weighted least squares regression in order to minimize the above mentioned issues. With high statistical confidence, the weighted trends of MOD AOT (550 nm), MIS AOT (558 nm), SEA AOT (510 nm), and MYD AOT (550 nm) over OECD Europe showed a significant decrease (-0.00274±0.00126, -0.00303±0.00169, -0.00077±0.00044, and -0.00530±0.00304 per year respectively) while increasing over East Asia (+0.00727±0.00385, +0.00673±0.00401, +0.00342±0.00171, and +0.01939±0.00986 per year respectively).

  18. CERES Single Satellite Footprint, TOA and Surface Fluxes, Clouds (SSF) data in HDF (CER_SSF_Aqua-FM3-MODIS_Edition2A)

    NASA Technical Reports Server (NTRS)

    Wielicki, Bruce A. (Principal Investigator)

    The Single Scanner Footprint TOA/Surface Fluxes and Clouds (SSF) product contains one hour of instantaneous Clouds and the Earth's Radiant Energy System (CERES) data for a single scanner instrument. The SSF combines instantaneous CERES data with scene information from a higher-resolution imager such as Visible/Infrared Scanner (VIRS) on TRMM or Moderate-Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua. Scene identification and cloud properties are defined at the higher imager resolution and these data are averaged over the larger CERES footprint. For each CERES footprint, the SSF contains the number of cloud layers and for each layer the cloud amount, height, temperature, pressure, optical depth, emissivity, ice and liquid water path, and water particle size. The SSF also contains the CERES filtered radiances for the total, shortwave (SW), and window (WN) channels and the unfiltered SW, longwave (LW), and WN radiances. The SW, LW, and WN radiances at spacecraft altitude are converted to Top-of-the-Atmosphere (TOA) fluxes based on the imager defined scene. These TOA fluxes are used to estimate surface fluxes. Only footprints with adequate imager coverage are included on CER_SSF_TRMM-PFM-VIRS_Subset_Edition1the SSF which is much less than the full set of footprints on the CERES ES-8 product. The following CERES SSF data sets are currently available: CER_SSF_TRMM-PFM-VIRS_Edition1 CER_SSF_TRMM-PFM-VIRS_Subset_Edition1 CER_SSF_TRMM-PFM-VIRS_Edition2A CER_SSF_TRMM-SIM-VIRS_Edition2_VIRSonly CER_SSF_TRMM-PFM-VIRS_Edition2A-TransOps CER_SSF_TRMM-PFM-VIRS_Edition2B-TransOps CER_SSF_TRMM-PFM-VIRS_Edition2B CER_SSF_Terra-FM1-MODIS_Edition1A CER_SSF_Terra-FM1-MODIS_Edition1A CER_SSF_Terra-FM1-MODIS_Edition2A CER_SSF_Terra-FM2-MODIS_Edition2A CER_SSF_Terra-FM1-MODIS_Edition2B CER_SSF_Terra-FM2-MODIS_Edition2B CER_SSF_Aqua-FM4-MODIS_Beta1 CER_SSF_Aqua-FM3-MODIS_Beta2 CER_SSF_Aqua-FM4-MODIS_Beta2. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1998-01-01; Stop

  19. CERES Single Satellite Footprint, TOA and Surface Fluxes, Clouds (SSF) data in HDF (CER_SSF_Aqua-FM4-MODIS_Edition2A)

    NASA Technical Reports Server (NTRS)

    Wielicki, Bruce A. (Principal Investigator)

    The Single Scanner Footprint TOA/Surface Fluxes and Clouds (SSF) product contains one hour of instantaneous Clouds and the Earth's Radiant Energy System (CERES) data for a single scanner instrument. The SSF combines instantaneous CERES data with scene information from a higher-resolution imager such as Visible/Infrared Scanner (VIRS) on TRMM or Moderate-Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua. Scene identification and cloud properties are defined at the higher imager resolution and these data are averaged over the larger CERES footprint. For each CERES footprint, the SSF contains the number of cloud layers and for each layer the cloud amount, height, temperature, pressure, optical depth, emissivity, ice and liquid water path, and water particle size. The SSF also contains the CERES filtered radiances for the total, shortwave (SW), and window (WN) channels and the unfiltered SW, longwave (LW), and WN radiances. The SW, LW, and WN radiances at spacecraft altitude are converted to Top-of-the-Atmosphere (TOA) fluxes based on the imager defined scene. These TOA fluxes are used to estimate surface fluxes. Only footprints with adequate imager coverage are included on CER_SSF_TRMM-PFM-VIRS_Subset_Edition1the SSF which is much less than the full set of footprints on the CERES ES-8 product. The following CERES SSF data sets are currently available: CER_SSF_TRMM-PFM-VIRS_Edition1 CER_SSF_TRMM-PFM-VIRS_Subset_Edition1 CER_SSF_TRMM-PFM-VIRS_Edition2A CER_SSF_TRMM-SIM-VIRS_Edition2_VIRSonly CER_SSF_TRMM-PFM-VIRS_Edition2A-TransOps CER_SSF_TRMM-PFM-VIRS_Edition2B-TransOps CER_SSF_TRMM-PFM-VIRS_Edition2B CER_SSF_Terra-FM1-MODIS_Edition1A CER_SSF_Terra-FM1-MODIS_Edition1A CER_SSF_Terra-FM1-MODIS_Edition2A CER_SSF_Terra-FM2-MODIS_Edition2A CER_SSF_Terra-FM1-MODIS_Edition2B CER_SSF_Terra-FM2-MODIS_Edition2B CER_SSF_Aqua-FM4-MODIS_Beta1 CER_SSF_Aqua-FM3-MODIS_Beta2 CER_SSF_Aqua-FM4-MODIS_Beta2. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1998-01-01; Stop

  20. CERES Single Satellite Footprint, TOA and Surface Fluxes, Clouds (SSF) data in HDF (CER_SSF_Aqua-FM4-MODIS_Ed2A-NoSW)

    NASA Technical Reports Server (NTRS)

    Wielicki, Bruce A. (Principal Investigator)

    The Single Scanner Footprint TOA/Surface Fluxes and Clouds (SSF) product contains one hour of instantaneous Clouds and the Earth's Radiant Energy System (CERES) data for a single scanner instrument. The SSF combines instantaneous CERES data with scene information from a higher-resolution imager such as Visible/Infrared Scanner (VIRS) on TRMM or Moderate-Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua. Scene identification and cloud properties are defined at the higher imager resolution and these data are averaged over the larger CERES footprint. For each CERES footprint, the SSF contains the number of cloud layers and for each layer the cloud amount, height, temperature, pressure, optical depth, emissivity, ice and liquid water path, and water particle size. The SSF also contains the CERES filtered radiances for the total, shortwave (SW), and window (WN) channels and the unfiltered SW, longwave (LW), and WN radiances. The SW, LW, and WN radiances at spacecraft altitude are converted to Top-of-the-Atmosphere (TOA) fluxes based on the imager defined scene. These TOA fluxes are used to estimate surface fluxes. Only footprints with adequate imager coverage are included on CER_SSF_TRMM-PFM-VIRS_Subset_Edition1the SSF which is much less than the full set of footprints on the CERES ES-8 product. The following CERES SSF data sets are currently available: CER_SSF_TRMM-PFM-VIRS_Edition1 CER_SSF_TRMM-PFM-VIRS_Subset_Edition1 CER_SSF_TRMM-PFM-VIRS_Edition2A CER_SSF_TRMM-SIM-VIRS_Edition2_VIRSonly CER_SSF_TRMM-PFM-VIRS_Edition2A-TransOps CER_SSF_TRMM-PFM-VIRS_Edition2B-TransOps CER_SSF_TRMM-PFM-VIRS_Edition2B CER_SSF_Terra-FM1-MODIS_Edition1A CER_SSF_Terra-FM1-MODIS_Edition1A CER_SSF_Terra-FM1-MODIS_Edition2A CER_SSF_Terra-FM2-MODIS_Edition2A CER_SSF_Terra-FM1-MODIS_Edition2B CER_SSF_Terra-FM2-MODIS_Edition2B CER_SSF_Aqua-FM4-MODIS_Beta1 CER_SSF_Aqua-FM3-MODIS_Beta2 CER_SSF_Aqua-FM4-MODIS_Beta2. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1998-01-01; Stop

  1. CERES Single Scanner Satellite Footprint, TOA, Surface Fluxes and Clouds (SSF) data in HDF (CER_SSF_Aqua-FM4-MODIS_Edition1B)

    NASA Technical Reports Server (NTRS)

    Wielicki, Bruce A. (Principal Investigator)

    The Single Scanner Footprint TOA/Surface Fluxes and Clouds (SSF) product contains one hour of instantaneous Clouds and the Earth's Radiant Energy System (CERES) data for a single scanner instrument. The SSF combines instantaneous CERES data with scene information from a higher-resolution imager such as Visible/Infrared Scanner (VIRS) on TRMM or Moderate-Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua. Scene identification and cloud properties are defined at the higher imager resolution and these data are averaged over the larger CERES footprint. For each CERES footprint, the SSF contains the number of cloud layers and for each layer the cloud amount, height, temperature, pressure, optical depth, emissivity, ice and liquid water path, and water particle size. The SSF also contains the CERES filtered radiances for the total, shortwave (SW), and window (WN) channels and the unfiltered SW, longwave (LW), and WN radiances. The SW, LW, and WN radiances at spacecraft altitude are converted to Top-of-the-Atmosphere (TOA) fluxes based on the imager defined scene. These TOA fluxes are used to estimate surface fluxes. Only footprints with adequate imager coverage are included on CER_SSF_TRMM-PFM-VIRS_Subset_Edition1the SSF which is much less than the full set of footprints on the CERES ES-8 product. The following CERES SSF data sets are currently available: CER_SSF_TRMM-PFM-VIRS_Edition1 CER_SSF_TRMM-PFM-VIRS_Subset_Edition1 CER_SSF_TRMM-PFM-VIRS_Edition2A CER_SSF_TRMM-SIM-VIRS_Edition2_VIRSonly CER_SSF_TRMM-PFM-VIRS_Edition2A-TransOps CER_SSF_TRMM-PFM-VIRS_Edition2B-TransOps CER_SSF_TRMM-PFM-VIRS_Edition2B CER_SSF_Terra-FM1-MODIS_Edition1A CER_SSF_Terra-FM1-MODIS_Edition1A CER_SSF_Terra-FM1-MODIS_Edition2A CER_SSF_Terra-FM2-MODIS_Edition2A CER_SSF_Terra-FM1-MODIS_Edition2B CER_SSF_Terra-FM2-MODIS_Edition2B CER_SSF_Aqua-FM4-MODIS_Beta1 CER_SSF_Aqua-FM3-MODIS_Beta2 CER_SSF_Aqua-FM4-MODIS_Beta2. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1998-01-01; Stop

  2. CERES Single Scanner Satellite Footprint, TOA, Surface Fluxes and Clouds (SSF) data in HDF (CER_SSF_Aqua-FM3-MODIS_Edition1B)

    NASA Technical Reports Server (NTRS)

    Wielicki, Bruce A. (Principal Investigator)

    The Single Scanner Footprint TOA/Surface Fluxes and Clouds (SSF) product contains one hour of instantaneous Clouds and the Earth's Radiant Energy System (CERES) data for a single scanner instrument. The SSF combines instantaneous CERES data with scene information from a higher-resolution imager such as Visible/Infrared Scanner (VIRS) on TRMM or Moderate-Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua. Scene identification and cloud properties are defined at the higher imager resolution and these data are averaged over the larger CERES footprint. For each CERES footprint, the SSF contains the number of cloud layers and for each layer the cloud amount, height, temperature, pressure, optical depth, emissivity, ice and liquid water path, and water particle size. The SSF also contains the CERES filtered radiances for the total, shortwave (SW), and window (WN) channels and the unfiltered SW, longwave (LW), and WN radiances. The SW, LW, and WN radiances at spacecraft altitude are converted to Top-of-the-Atmosphere (TOA) fluxes based on the imager defined scene. These TOA fluxes are used to estimate surface fluxes. Only footprints with adequate imager coverage are included on CER_SSF_TRMM-PFM-VIRS_Subset_Edition1the SSF which is much less than the full set of footprints on the CERES ES-8 product. The following CERES SSF data sets are currently available: CER_SSF_TRMM-PFM-VIRS_Edition1 CER_SSF_TRMM-PFM-VIRS_Subset_Edition1 CER_SSF_TRMM-PFM-VIRS_Edition2A CER_SSF_TRMM-SIM-VIRS_Edition2_VIRSonly CER_SSF_TRMM-PFM-VIRS_Edition2A-TransOps CER_SSF_TRMM-PFM-VIRS_Edition2B-TransOps CER_SSF_TRMM-PFM-VIRS_Edition2B CER_SSF_Terra-FM1-MODIS_Edition1A CER_SSF_Terra-FM1-MODIS_Edition1A CER_SSF_Terra-FM1-MODIS_Edition2A CER_SSF_Terra-FM2-MODIS_Edition2A CER_SSF_Terra-FM1-MODIS_Edition2B CER_SSF_Terra-FM2-MODIS_Edition2B CER_SSF_Aqua-FM4-MODIS_Beta1 CER_SSF_Aqua-FM3-MODIS_Beta2 CER_SSF_Aqua-FM4-MODIS_Beta2. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1998-01-01; Stop

  3. Daily Operational MODIS BRDF, Albedo and Nadir Reflectance Products (V006)

    NASA Astrophysics Data System (ADS)

    Schaaf, C.; Wang, Z.; Shuai, Y.; Strahler, A. H.

    2012-12-01

    The operational surface Bidirectional Reflectance Distribution Function (BRDF) and Albedo product (MCD43) has been produced for more than a decade from the MODerate resolution Imaging Spectroradiometer (MODIS) sensors aboard NASA's Terra and Aqua satellites. The Collection V005 operational product, reprocessed for the entire record, provides BRDF models, surface albedo quantities, and Nadir BRDF-Adjusted Reflectances (NBAR) globally on a 500m grid in a sinusoidal projection every 8 days (based on a 16 day window). As surface albedo is an essential climate variable (ECV), the accurate global estimations of terrestrial albedo provided by this product are used by numerous climate and biogeochemical modeling efforts. Of equal utility, the NBAR values are used as the primary inputs to the MODIS Land Cover product and (in the form of NBAR vegetation indices) are used for a variety of vegetation monitoring and phenological studies. Furthermore, the retrieved BRDF model parameters are increasingly being used to provide estimates of vegetation canopy variability and clumping. In the Collection V006 reprocessing effort, the standard global MODIS BRDF/Albedo product will finally be produced as a daily product (based on a 16 day moving window). The daily algorithm will rely on rolling multi-date directional surface reflectances to establish a general surface reflectance anisotropy model of the surface, while emphasizing the daily observation in an attempt to capture rapidly changing surface conditions. In order to improve retrievals over high latitudes and better capture snow covered and dormant vegetation conditions, more surface reflectances per day will be used in V006. Furthermore, the backup database (used to produce poorer quality magnitude inversions when high quality full retrievals are not possible) will now be continuously updated from the latest high quality full inversion for improved accuracy. The availability of daily V006 BRDF/albedo products will allow more

  4. Seasonal nitrate algorithms for nitrate retrieval using OCEANSAT-2 and MODIS-AQUA satellite data.

    PubMed

    Durairaj, Poornima; Sarangi, Ranjit Kumar; Ramalingam, Shanthi; Thirunavukarassu, Thangaradjou; Chauhan, Prakash

    2015-04-01

    In situ datasets of nitrate, sea surface temperature (SST), and chlorophyll a (chl a) collected during the monthly coastal samplings and organized cruises along the Tamilnadu and Andhra Pradesh coast between 2009 and 2013 were used to develop seasonal nitrate algorithms. The nitrate algorithms have been built up based on the three-dimensional regressions between SST, chl a, and nitrate in situ data using linear, Gaussian, Lorentzian, and paraboloid function fittings. Among these four functions, paraboloid was found to be better with the highest co-efficient of determination (postmonsoon: R2=0.711, n=357; summer: R2=0.635, n=302; premonsoon: R2=0.829, n=249; and monsoon: R2=0.692, n=272) for all seasons. Based on these fittings, seasonal nitrate images were generated using the concurrent satellite data of SST from Moderate Resolution Imaging Spectroradiometer (MODIS) and chlorophyll (chl) from Ocean Color Monitor (OCM-2) and MODIS. The best retrieval of modeled nitrate (R2=0.527, root mean square error (RMSE)=3.72, and mean normalized bias (MNB)=0.821) was observed for the postmonsoon season due to the better retrieval of both SST MODIS (28 February 2012, R2=0.651, RMSE=2.037, and MNB=0.068) and chl OCM-2 (R2=0.534, RMSE=0.317, and MNB=0.27). Present results confirm that the chl OCM-2 and SST MODIS retrieve nitrate well than the MODIS-derived chl and SST largely due to the better retrieval of chl by OCM-2 than MODIS. PMID:25762424

  5. Quality Assessment of Landsat Surface Reflectance Products Using MODIS Data

    NASA Technical Reports Server (NTRS)

    Feng, Min; Huang, Chengquan; Channan, Saurabh; Vermote, Eric; Masek, Jeffrey G.; Townshend, John R.

    2012-01-01

    Surface reflectance adjusted for atmospheric effects is a primary input for land cover change detection and for developing many higher level surface geophysical parameters. With the development of automated atmospheric correction algorithms, it is now feasible to produce large quantities of surface reflectance products using Landsat images. Validation of these products requires in situ measurements, which either do not exist or are difficult to obtain for most Landsat images. The surface reflectance products derived using data acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS), however, have been validated more comprehensively. Because the MODIS on the Terra platform and the Landsat 7 are only half an hour apart following the same orbit, and each of the 6 Landsat spectral bands overlaps with a MODIS band, good agreements between MODIS and Landsat surface reflectance values can be considered indicators of the reliability of the Landsat products, while disagreements may suggest potential quality problems that need to be further investigated. Here we develop a system called Landsat-MODIS Consistency Checking System (LMCCS). This system automatically matches Landsat data with MODIS observations acquired on the same date over the same locations and uses them to calculate a set of agreement metrics. To maximize its portability, Java and open-source libraries were used in developing this system, and object-oriented programming (OOP) principles were followed to make it more flexible for future expansion. As a highly automated system designed to run as a stand-alone package or as a component of other Landsat data processing systems, this system can be used to assess the quality of essentially every Landsat surface reflectance image where spatially and temporally matching MODIS data are available. The effectiveness of this system was demonstrated using it to assess preliminary surface reflectance products derived using the Global Land Survey (GLS) Landsat

  6. Quality assessment of Landsat surface reflectance products using MODIS data

    NASA Astrophysics Data System (ADS)

    Feng, Min; Huang, Chengquan; Channan, Saurabh; Vermote, Eric F.; Masek, Jeffrey G.; Townshend, John R.

    2012-01-01

    Surface reflectance adjusted for atmospheric effects is a primary input for land cover change detection and for developing many higher level surface geophysical parameters. With the development of automated atmospheric correction algorithms, it is now feasible to produce large quantities of surface reflectance products using Landsat images. Validation of these products requires in situ measurements, which either do not exist or are difficult to obtain for most Landsat images. The surface reflectance products derived using data acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS), however, have been validated more comprehensively. Because the MODIS on the Terra platform and the Landsat 7 are only half an hour apart following the same orbit, and each of the 6 Landsat spectral bands overlaps with a MODIS band, good agreements between MODIS and Landsat surface reflectance values can be considered indicators of the reliability of the Landsat products, while disagreements may suggest potential quality problems that need to be further investigated. Here we develop a system called Landsat-MODIS Consistency Checking System (LMCCS). This system automatically matches Landsat data with MODIS observations acquired on the same date over the same locations and uses them to calculate a set of agreement metrics. To maximize its portability, Java and open-source libraries were used in developing this system, and object-oriented programming (OOP) principles were followed to make it more flexible for future expansion. As a highly automated system designed to run as a stand-alone package or as a component of other Landsat data processing systems, this system can be used to assess the quality of essentially every Landsat surface reflectance image where spatially and temporally matching MODIS data are available. The effectiveness of this system was demonstrated using it to assess preliminary surface reflectance products derived using the Global Land Survey (GLS) Landsat

  7. The Global Impact of Clouds on the Production of MODIS Bidirectional Reflectance Model-based Composites for Terrestrial Monitoring

    NASA Technical Reports Server (NTRS)

    Roy, D. P.; Lewis, P.; Schaaf, C. B.; Devadiga, S.; Boschetti, L.

    2006-01-01

    A global data set of cloud occurrence probability derived from Moderate Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua gridded daily data is analyzed to investigate the probability of obtaining at least a minimum number of cloud-free observations within various compositing periods. The probabilities derived from Terra and Aqua, with morning and afternoon overpass times, respectively, are similar and increase with compositing period. Compositing both Terra and Aqua observations results is considerably higher probabilities of obtaining a sufficient number of observations for bidirectional reflectance model-based compositing. Given that the only alternative is obtaining sufficient samples to extend the observation period, which can cause significant problems when the surface state changes, it is concluded that using data from the two MODIS sensors provides the most effective way of generating composited products. Findings with respect to the availability of cloud free composites when n-day composites are generated on a temporally overlapping daily rolling basis, i.e., every day, rather than every n-days, are also discussed for regional and global applications.

  8. Constraining canopy biophysical simulations with daily MODIS reflectance data ensuring pixel-target adequacy

    NASA Astrophysics Data System (ADS)

    Drewry, D.; Duveiller, G.

    2013-12-01

    Aqua platforms. As a whiskbroom imaging instrument, MODIS has a complex viewing geometry which affects its spatial response, i.e. the way the electromagnetic radiation reflected from the surface is ultimately encoded in the remotely-sensed image. A model of this spatial response is used here to ensure that the footprint of the satellite observations matches adequately with the coupled model simulations of the target fields. The relationship between the purity of the remote sensing observation, with respect to the target field, and the quality of the biophysical variable inversion is also investigated.

  9. Comparison of C5 and C6 Aqua-MODIS Dark Target Aerosol Validation

    NASA Technical Reports Server (NTRS)

    Munchak, Leigh A.; Levy, Robert C.; Mattoo, Shana

    2014-01-01

    We compare C5 and C6 validation to compare the C6 10 km aerosol product against the well validated and trusted aerosol product on global and regional scales. Only the 10 km aerosol product is evaluated in this study, validation of the new C6 3 km aerosol product still needs to be performed. Not all of the time series has processed yet for C5 or C6, and the years processed for the 2 products is not exactly the same (this work is preliminary!). To reduce the impact of outlier observations, MODIS is spatially averaged within 27.5 km of the AERONET site, and AERONET is temporatally averaged within 30 minutes of the MODIS overpass time. Only high quality (QA = 3 over land, QA greater than 0 over ocean) pixels are included in the mean.

  10. Climatology and trends of aerosol optical depth over the Mediterranean basin during the last 12years (2002-2014) based on Collection 006 MODIS-Aqua data.

    PubMed

    Floutsi, A A; Korras-Carraca, M B; Matsoukas, C; Hatzianastassiou, N; Biskos, G

    2016-05-01

    The Mediterranean basin is a region of particular interest for studying atmospheric aerosols due to the large variety of air masses it receives, and its sensitivity to climate change. In this study we use the newest collection (C006) of aerosol optical depth from MODIS-Aqua, from which we also derived the fine-mode fraction and Ångström exponent over the last 12years (i.e., from 2002 to 2014), providing the longest analyzed dataset for this region. The long-term regional optical depth average is 0.20±0.05, with the indicated uncertainty reflecting the inter-annual variability. Overall, the aerosol optical depth exhibits a south-to-north decreasing gradient and an average decreasing trend of 0.0030 per year (19% total decrease over the study period). The correlation between the reported AOD observations with measurements from the ground AERONET stations is high (R=0.76-0.80 depending on the wavelength), with the MODIS-Aqua data being slightly overestimated. Both fine-fraction and Ångström exponent data highlight the dominance of anthropogenic aerosols over the northern, and of desert aerosols over the southern part of the region. Clear intrusions of desert dust over the Eastern Mediterranean are observed principally in spring, and in some cases in winter. Dust intrusions dominate the Western Mediterranean in the summer (and sometimes in autumn), whereas anthropogenic aerosols dominate the sub-region of the Black Sea in all seasons but especially during summer. Fine-mode optical depth is found to decrease over almost all areas of the study region during the 12-year period, marking the decreasing contribution of anthropogenic particulate matter emissions over the study area. Coarse-mode aerosol load also exhibits an overall decreasing trend. However, its decrease is smaller than that of fine aerosols and not as uniformly distributed, underlining that the overall decrease in the region arises mainly from reduced anthropogenic emissions. PMID:26878641

  11. Understanding Differences Between Co-Incident CloudSat, Aqua/MODIS and NOAA18 MHS Ice water Path Retrievals Over the Tropical Oceans

    NASA Technical Reports Server (NTRS)

    Pittman, Jasna; Robertson, Franklin; Blankenship, Clay

    2008-01-01

    Accurate measurement of the physical and radiative properties of clouds and their representation in climate models continues to be a challe nge. Model parameterizations are still subject to a large number of t unable parameters; furthermore, accurate and representative in situ o bservations are very sparse, and satellite observations historically have significant quantitative uncertainties, particularly with respect to particle size distribution (PSD) and cloud phase. Ice Water Path (IWP), or amount of ice present in a cloud column, is an important cl oud property to accurately quantify, because it is an integral measur e of the microphysical properties of clouds and the cloud feedback pr ocesses in the climate system. This paper investigates near co-incident retrievals of IWP over tropical oceans using three diverse measurem ent systems: radar from CloudSat, Vis/IR from Aqua/MODIS, and microwa ve from NOAA-18IMHS. CloudSat 94 GHz radar measurements provide high resolution vertical and along-orbit structure of cloud reflectivity a nd enable IWP (and IWC) retrievals. Overlapping MODIS measurements of cloud optical thickness and phase allow estimates of IWP when cloud tops are identified as being ice. Periodically, NOAA18 becomes co-inci dent in space I time to enable comparison of A-Train measurements to IWP inferred from the 157 and 89 GHz channel radiances. This latter m easurement is effective only for thick convective anvil systems. We s tratify these co-incident data (less than 4 minutes separation) into cirrus only, cirrus overlying liquid water clouds, and precipitating d eep convective clouds. Substantial biases in IWP and ice effective ra dius are found. Systematic differences in these retrievals are consid ered in light of the uncertainties in a priori assumptions ofPSDs, sp ectral sensitivity and algorithm strategies, which have a direct impact on the IWP product.

  12. Analysis of the influence of river discharge and wind on the Ebro turbid plume using MODIS-Aqua and MODIS-Terra data

    NASA Astrophysics Data System (ADS)

    Fernández-Nóvoa, D.; Mendes, R.; deCastro, M.; Dias, J. M.; Sánchez-Arcilla, A.; Gómez-Gesteira, M.

    2015-02-01

    The turbid plume formed at many river mouths influences the adjacent coastal area because it transports sediments, nutrients, and pollutants. The effects of the main forcings affecting the Ebro turbid plume were analyzed using data obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor onboard the Aqua and Terra satellites over the period 2003-2011. Composite images were obtained for days under certain river discharge conditions (different flow regimes) and different types of wind (alongshore and cross-shore winds) in order to obtain a representative plume pattern for each situation. River discharge was the main driver of the Ebro River plume, followed by wind as the secondary force and regional oceanic circulation as the third one. Turbid plume extension increased monotonically with increased river discharge. Under high river discharge conditions (> 355 m3 s- 1), wind distributed the plume in the dominant wind direction. Seaward winds (mistral) produced the largest extension of the plume (1893 km2), whereas southern alongshore winds produced the smallest one (1325 km2). Northern alongshore winds induced the highest mean turbid value of the plume, and southern alongshore winds induced the lowest one. Regardless of the wind condition, more than 70% of the plume extension was located south of the river mouth influenced by the regional oceanic circulation.

  13. A surface reflectance scheme for retrieving aerosol optical depth over urban surfaces in MODIS Dark Target retrieval algorithm

    NASA Astrophysics Data System (ADS)

    Gupta, Pawan; Levy, Robert C.; Mattoo, Shana; Remer, Lorraine A.; Munchak, Leigh A.

    2016-07-01

    The MODerate resolution Imaging Spectroradiometer (MODIS) instruments, aboard the two Earth Observing System (EOS) satellites Terra and Aqua, provide aerosol information with nearly daily global coverage at moderate spatial resolution (10 and 3 km). Almost 15 years of aerosol data records are now available from MODIS that can be used for various climate and air-quality applications. However, the application of MODIS aerosol products for air-quality concerns is limited by a reduction in retrieval accuracy over urban surfaces. This is largely because the urban surface reflectance behaves differently than that assumed for natural surfaces. In this study, we address the inaccuracies produced by the MODIS Dark Target (MDT) algorithm aerosol optical depth (AOD) retrievals over urban areas and suggest improvements by modifying the surface reflectance scheme in the algorithm. By integrating MODIS Land Surface Reflectance and Land Cover Type information into the aerosol surface parameterization scheme for urban areas, much of the issues associated with the standard algorithm have been mitigated for our test region, the continental United States (CONUS). The new surface scheme takes into account the change in underlying surface type and is only applied for MODIS pixels with urban percentage (UP) larger than 20 %. Over the urban areas where the new scheme has been applied (UP > 20 %), the number of AOD retrievals falling within expected error (EE %) has increased by 20 %, and the strong positive bias against ground-based sun photometry has been eliminated. However, we note that the new retrieval introduces a small negative bias for AOD values less than 0.1 due to the ultra-sensitivity of the AOD retrieval to the surface parameterization under low atmospheric aerosol loadings. Global application of the new urban surface parameterization appears promising, but further research and analysis are required before global implementation.

  14. Spatial and Temporal Distribution of Tropospheric Clouds and Aerosols Observed by MODIS Onboard the Terra and Aqua Satellites

    NASA Technical Reports Server (NTRS)

    King, Michael D.; Platnick, Steven; Menzel, W. Paul; Ackerman, Steven A.; Remer, Lorraine A.

    2006-01-01

    Remote sensing of cloud and aerosol optical properties is routinely obtained using the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Terra and Aqua satellites. Instruments that are being used to enhance our ability to characterize the global distribution of cloud and aerosol properties include well-calibrated multispectral radiometers that measure in the visible, near-infrared, and thermal infrared. The availability of thermal channels to enhance detection of cloud when estimating aerosol properties is an important improvement. In this paper, we describe the radiative properties of clouds as currently determined from satellites (cloud fraction, optical thickness, cloud top pressure, and cloud particle effective radius) and highlight the global/regional cloud microphysical properties currently available for assessing climate variability and forcing. These include the latitudinal distribution of cloud optical and radiative properties of both liquid water and ice clouds, as well as joint histograms of cloud optical thickness and effective particle radius for selected geographical locations around the world. In addition, we will illustrate the radiative and microphysical properties of aerosol particles (in cloud free regions) that are currently available from space-based observations, and show the latitudinal distribution of aerosol optical properties over both land and ocean surfaces.

  15. Contrail radiative forcing over the Northern Hemisphere from 2006 Aqua MODIS data

    NASA Astrophysics Data System (ADS)

    Spangenberg, Douglas A.; Minnis, Patrick; Bedka, Sarah T.; Palikonda, Rabindra; Duda, David P.; Rose, Fred G.

    2013-02-01

    Abstract Radiative forcing due to linear-shaped jet contrails is calculated over the Northern Hemisphere for four seasonal months using 2006 <span class="hlt">Aqua</span> Moderate-resolution Imaging Spectroradiometer cloud and contrail property retrieval data in a radiative transfer model. The 4 month mean shortwave, longwave, and net radiative forcings normalized to 100% contrail cover are -5.7, 14.2, and 8.5 Wm-2. Mean total net forcing over the northern half of the globe varies from 9.1 mW m-2 during October to 12.1 mW m-2 in January and is only representative at 01:30 and 13:30 LT in nonpolar regions. In some dense flight traffic corridors, the mean net forcing approaches 80 mW m-2. Scaling the 4 month average of 10.6 mW m-2 to the Southern Hemisphere air traffic yields global mean net forcing of 5.7 mW m-2, which is smaller than most model estimates. Nighttime net forcing is 3.6 times greater than during daytime, when net forcing is greatest over low clouds. Effects from contrail cirrus clouds that evolve from linear contrails are not considered in these results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070017450','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070017450"><span id="translatedtitle">A New Algorithm for Retrieving Aerosol Properties Over Land from <span class="hlt">MODIS</span> Spectral <span class="hlt">Reflectance</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Levy, Robert C.; Remer, Lorraine A.; Mattoo, Shana; Vermote, Eric F.; Kaufman, Yoram J.</p> <p>2006-01-01</p> <p>Since first light in early 2000, operational global quantitative retrievals of aerosol properties over land have been made from <span class="hlt">MODIS</span> observed spectral <span class="hlt">reflectance</span>. These products have been continuously evaluated and validated, and opportunities for improvements have been noted. We have replaced the original algorithm by improving surface <span class="hlt">reflectance</span> assumptions, the aerosol model optical properties and the radiative transfer code used to create the lookup tables. The new algorithm (known as Version 5.2 or V5.2) performs a simultaneous inversion of two visible (0.47 and 0.66 micron) and one shortwave-IR (2.12 micron) channel, making use of the coarse aerosol information content contained in the 2.12 micron channel. Inversion of the three channels yields three nearly independent parameters, the aerosol optical depth (tau) at 0.55 micron, the non-dust or fine weighting (eta) and the surface <span class="hlt">reflectance</span> at 2.12 micron. Finally, retrievals of small magnitude negative tau values (down to -0.05) are considered valid, thus normalizing the statistics of tau in near zero tau conditions. On a 'test bed' of 6300 granules from Terra and <span class="hlt">Aqua</span>, the products from V5.2 show marked improvement over those from the previous versions, including much improved retrievals of tau, where the <span class="hlt">MODIS</span>/AERONET tau (at 0.55 micron) regression has an equation of: y = 1.01+0.03, R = 0.90. Mean tau for the test bed is reduced from 0.28 to 0.21.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003AGUFM.H32B0562G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003AGUFM.H32B0562G"><span id="translatedtitle">Exploring the feasibility of using the <span class="hlt">MODIS</span> 1 km by 1 km cloud mask product to generate a lower resolution product suitable for use with other instruments (e.g AIRS) on the EOS-<span class="hlt">Aqua</span> satellite.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gopalan, A.; Leptoukh, G.; Savtchenko, A.; Ouzounov, D.</p> <p>2003-12-01</p> <p>The <span class="hlt">MODIS</span> Level-2 Cloud Mask Products MOD35_L2 (<span class="hlt">MODIS</span> -TERRA) and MYD35_L2 (<span class="hlt">MODIS-AQUA</span>) are available globally day and night at a pixel resolution of 1 km by 1 km. The cloud mask is based on a series of spectral cloud detection tests and estimates the probability of a pixel being clear with varying degrees of confidence (Platnick et al). We attempt to explore the possibility of adapting the <span class="hlt">MODIS</span> Cloud Mask Product to other instruments on the Terra and <span class="hlt">Aqua</span> Satellites that have a coarser pixel resolution as compared to the <span class="hlt">MODIS</span> pixel. From a data center (e.g. GES-DAAC) perspective, this could potentially have a positive impact on the distribution system and better serve end users who require a lower resolution cloud mask product for their applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ISPAr41B7..219F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ISPAr41B7..219F"><span id="translatedtitle">Global Land Cover Classification Using <span class="hlt">Modis</span> Surface <span class="hlt">Reflectance</span> Prosucts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fukue, Kiyonari; Shimoda, Haruhisa</p> <p>2016-06-01</p> <p>The objective of this study is to develop high accuracy land cover classification algorithm for Global scale by using multi-temporal <span class="hlt">MODIS</span> land <span class="hlt">reflectance</span> products. In this study, time-domain co-occurrence matrix was introduced as a classification feature which provides time-series signature of land covers. Further, the non-parametric minimum distance classifier was introduced for timedomain co-occurrence matrix, which performs multi-dimensional pattern matching for time-domain co-occurrence matrices of a classification target pixel and each classification classes. The global land cover classification experiments have been conducted by applying the proposed classification method using 46 multi-temporal(in one year) SR(Surface <span class="hlt">Reflectance</span>) and NBAR(Nadir BRDF-Adjusted <span class="hlt">Reflectance</span>) products, respectively. IGBP 17 land cover categories were used in our classification experiments. As the results, SR and NBAR products showed similar classification accuracy of 99%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120015718','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120015718"><span id="translatedtitle">Accuracy Assessment of <span class="hlt">Aqua-MODIS</span> Aerosol Optical Depth Over Coastal Regions: Importance of Quality Flag and Sea Surface Wind Speed</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Anderson, J. C.; Wang, J.; Zeng, J.; Petrenko, M.; Leptoukh, G. G.; Ichoku, C.</p> <p>2012-01-01</p> <p>Coastal regions around the globe are a major source for anthropogenic aerosols in the atmosphere, but the underlying surface characteristics are not favorable for the Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) algorithms designed for retrieval of aerosols over dark land or open-ocean surfaces. Using data collected from 62 coastal stations worldwide from the Aerosol Robotic Network (AERONET) from approximately 2002-2010, accuracy assessments are made for coastal aerosol optical depth (AOD) retrieved from <span class="hlt">MODIS</span> aboard <span class="hlt">Aqua</span> satellite. It is found that coastal AODs (at 550 nm) characterized respectively by the <span class="hlt">MODIS</span> Dark Land (hereafter Land) surface algorithm, the Open-Ocean (hereafter Ocean) algorithm, and AERONET all exhibit a log-normal distribution. After filtering by quality flags, the <span class="hlt">MODIS</span> AODs respectively retrieved from the Land and Ocean algorithms are highly correlated with AERONET (with R(sup 2) is approximately equal to 0.8), but only the Land algorithm AODs fall within the expected error envelope greater than 66% of the time. Furthermore, the <span class="hlt">MODIS</span> AODs from the Land algorithm, Ocean algorithm, and combined Land and Ocean product show statistically significant discrepancies from their respective counterparts from AERONET in terms of mean, probability density function, and cumulative density function, which suggest a need for future improvement in retrieval algorithms. Without filtering with quality flag, the <span class="hlt">MODIS</span> Land and Ocean AOD dataset can be degraded by 30-50% in terms of mean bias. Overall, the <span class="hlt">MODIS</span> Ocean algorithm overestimates the AERONET coastal AOD by 0.021 for AOD less than 0.25 and underestimates it by 0.029 for AOD greater than 0.25. This dichotomy is shown to be related to the ocean surface wind speed and cloud contamination effects on the satellite aerosol retrieval. The Modern Era Retrospective-Analysis for Research and Applications (MERRA) reveals that wind speeds over the global coastal region 25 (with a mean and median</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JARS...10.4004C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JARS...10.4004C&link_type=ABSTRACT"><span id="translatedtitle">Alternative method of on-orbit response-versus-scan-angle characterization for <span class="hlt">MODIS</span> <span class="hlt">reflective</span> solar bands</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Hongda; Xiong, Xiaoxiong; Angal, Amit; Geng, Xu; Wu, Aisheng</p> <p>2016-04-01</p> <p>The moderate resolution imaging spectroradiometer (<span class="hlt">MODIS</span>) has 20 <span class="hlt">reflective</span> solar bands (RSB), covering a spectral range from 0.41 to 2.2 μm, which are calibrated on-orbit using its onboard calibrators, which include a solar diffuser, a solar diffuser stability monitor, and a spectroradiometric calibration assembly. A space view (SV) port is used to provide a background reference and also facilitates near-monthly lunar observations through a spacecraft roll. In every scan, the Earth's surface, SV, and onboard calibrators are viewed via a two-sided scan mirror, the <span class="hlt">reflectance</span> of which depends on the angle of incidence (AOI) as well as the wavelength of the incident light. Response-versus-scan-angle (RVS) is defined as a dependence function of the scan mirror's <span class="hlt">reflectance</span> over AOI. An initial RVS for each RSB was measured prelaunch for both Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span>. Algorithms have been developed to track the on-orbit RVS variation using the measurements from the onboard calibrators, supplemented with the earth view (EV) trends from pseudoinvariant desert targets obtained at different AOI. Since the mission beginning, the <span class="hlt">MODIS</span> characterization support team (MCST) has dedicated efforts in evaluating approaches of characterizing the on-orbit RVS. A majority of the approaches focused on fitting the data at each AOI over time and then deriving the relative change at different AOI. The current version of the on-orbit RVS algorithm, as implemented in the collection 6 (C6) level-1B (L1B), is also based on the above rationale. It utilizes the EV response trends from the pseudoinvariant Libyan desert targets to supplement the gain derived from the onboard calibrators. The primary limitation of this approach is the assumption of the temporal stability of these desert sites. Consequently, MCST developed an approach that derives the on-orbit RVS change using measurements from a single desert site, combined with the on-orbit lunar measurements. In addition, the EV and onboard</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_5 --> <div id="page_6" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="101"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20160008400&hterms=methods&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dmethods','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20160008400&hterms=methods&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dmethods"><span id="translatedtitle">Alternative Method of On-Orbit Response-Versus-Scan-Angle Characterization for <span class="hlt">MODIS</span> <span class="hlt">Reflective</span> Solar Bands</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chen, Hongda; Xiong, Xiaoxiong; Angal, Amit; Geng, Xu; Wu, Aisheng</p> <p>2016-01-01</p> <p>The moderate resolution imaging spectroradiometer (<span class="hlt">MODIS</span>) has 20 <span class="hlt">reflective</span> solar bands (RSB), covering a spectral range from 0.41 to 2.2 microns, which are calibrated on-orbit using its onboard calibrators, which include a solar diffuser, a solar diffuser stability monitor, and a spectroradiometric calibration assembly. A space view (SV) port is used to provide a background reference and also facilitates near-monthly lunar observations through a spacecraft roll. In every scan, the Earth's surface, SV, and onboard calibrators are viewed via a two-sided scan mirror, the <span class="hlt">reflectance</span> of which depends on the angle of incidence (AOI) as well as the wavelength of the incident light. Response-versus-scan-angle (RVS) is defined as a dependence function of the scan mirror's <span class="hlt">reflectance</span> over AOI. An initial RVS for each RSB was measured prelaunch for both Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span>. Algorithms have been developed to track the on-orbit RVS variation using the measurements from the onboard calibrators, supplemented with the earth view (EV) trends from pseudoinvariant desert targets obtained at different AOI. Since the mission beginning, the <span class="hlt">MODIS</span> characterization support team (MCST) has dedicated efforts in evaluating approaches of characterizing the on-orbit RVS. A majority of the approaches focused on fitting the data at each AOI over time and then deriving the relative change at different AOI. The current version of the on-orbit RVS algorithm, as implemented in the collection 6 (C6) level-1B (L1B), is also based on the above rationale. It utilizes the EV response trends from the pseudoinvariant Libyan desert targets to supplement the gain derived from the onboard calibrators. The primary limitation of this approach is the assumption of the temporal stability of these desert sites. Consequently, MCST developed an approach that derives the on-orbit RVS change using measurements from a single desert site, combined with the on-orbit lunar measurements. In addition, the EV and onboard</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUSM.B51A..02D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUSM.B51A..02D"><span id="translatedtitle">Constraining canopy biophysical simulations with <span class="hlt">MODIS</span> <span class="hlt">reflectance</span> data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Drewry, D. T.; Duveiller, G.</p> <p>2013-05-01</p> <p>Modern vegetation models incorporate ecophysiological details that allow for accurate estimates of carbon dioxide uptake, water use and energy exchange, but require knowledge of dynamic structural and biochemical traits. Variations in these traits are controlled by genetic factors as well as growth stage and nutrient and moisture availability, making them difficult to predict and prone to significant error. Here we explore the use of <span class="hlt">MODIS</span> optical <span class="hlt">reflectance</span> data for constraining key canopy- and leaf-level traits required by forward biophysical models. A multi-objective optimization algorithm is used to invert the PROSAIL canopy radiation transfer model, which accounts for the effects of leaf-level optical properties, foliage distribution and orientation on canopy <span class="hlt">reflectance</span> across the optical range. Inversions are conducted for several growing seasons for both soybean and maize at several sites in the Central US agro-ecosystem. These inversions provide estimates of seasonal variations, and associated uncertainty, of variables such as leaf area index (LAI) that are then used as inputs into the MLCan biophysical model to conduct forward simulations. MLCan characterizes the ecophysiological functioning of a plant canopy at a half-hourly timestep, and has been rigorously validated for both C3 and C4 crops against observations of canopy CO2 uptake, evapotranspiration and sensible heat exchange across a wide range of meteorological conditions. The inversion-derived canopy properties are used to examine the ability of <span class="hlt">MODIS</span> data to characterize seasonal variations in canopy properties in the context of a detailed forward canopy biophysical model, and the uncertainty induced in forward model estimates as a function of the uncertainty in the inverted parameters. Special care is made to ensure that the satellite observations match adequately, in both time and space, with the coupled model simulations. To do so, daily <span class="hlt">MODIS</span> observations are used and a validated model of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012ACPD...1211733Z&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012ACPD...1211733Z&link_type=ABSTRACT"><span id="translatedtitle">A better understanding of cloud optical thickness derived from the passive sensors <span class="hlt">MODIS/AQUA</span> and POLDER/PARASOL in the A-train constellation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zeng, S.; Cornet, C.; Parol, F.; Riedi, J.; Thieuleux, F.</p> <p>2012-05-01</p> <p>Cloud optical thickness (COT) is one of the most important parameter for the characterization of cloud in the Earth radiative budget. Its retrieval strongly depends on instrument characteristics and on many cloud and environment factors. Using coincident observations from POLDER/PARASOL and <span class="hlt">MODIS/AQUA</span> in the A-train constellation, geographical distributions and seasonal changes of COT are presented, in good agreement with general cloud climatology characteristics. Retrieval uncertainties mainly associated to sensor spatial resolution, cloud inhomogeneity and microphysical assumptions are also discussed. Comparisons of COT derived from POLDER and <span class="hlt">MODIS</span> illustrate that as the primary factor, the sensor spatial resolution impacts COT retrievals and statistics through both cloud detection and sub-pixel cloud inhomogeneity sensitivity. The uncertainties associated to cloud microphysics assumptions, namely cloud phase, particle size and shape, also impact significantly COT retrievals. For clouds with unambiguous cloud phase, strong correlations exist between the two COTs, with <span class="hlt">MODIS</span> values comparable to POLDER ones for liquid clouds and <span class="hlt">MODIS</span> values larger than POLDER ones for ice clouds. The large differences observed in ice phase cases are due to the use of different microphysical models in the two retrieval schemes. In cases when the two sensors disagree on cloud phase decision, COT retrieved assuming liquid phase are systematically larger. The angular biases related to specific observation geometries are also quantified and discussed in particular based on POLDER observations. Those exhibit a clear increase of COT with decreasing sun elevation and a decrease of COT in forward scattering directions due to sub-pixel inhomogeneities and shadowing effects, this especially for lower sun. It also demonstrates unrealistic COT variations in the rainbow and backward directions due to inappropriate cloud optical properties representation and an important increase of COT in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4554528','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4554528"><span id="translatedtitle">Spatio-Temporal Variations in the Associations between Hourly PM2.5 and Aerosol Optical Depth (AOD) from <span class="hlt">MODIS</span> Sensors on Terra and <span class="hlt">Aqua</span>*</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kim, Minho; Zhang, Xingyou; Holt, James B.; Liu, Yang</p> <p>2015-01-01</p> <p>Recent studies have explored the relationship between aerosol optical depth (AOD) measurements by satellite sensors and concentrations of particulate matter with aerodynamic diameters less than 2.5 μm (PM2.5). However, relatively little is known about spatial and temporal patterns in this relationship across the contiguous United States. In this study, we investigated the relationship between US Environmental Protection Agency estimates of PM2.5 concentrations and Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) AOD measurements provided by two NASA satellites (Terra and <span class="hlt">Aqua</span>) across the contiguous United States during 2005. We found that the combined use of both satellite sensors provided more AOD coverage than the use of either satellite sensor alone, that the correlation between AOD measurements and PM2.5 concentrations varied substantially by geographic location, and that this correlation was stronger in the summer and fall than that in the winter and spring. PMID:26336576</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20120010478&hterms=snow&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dsnow','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20120010478&hterms=snow&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dsnow"><span id="translatedtitle">An Algorithm for the Retrieval of 30-m Snow-Free Albedo from Landsat Surface <span class="hlt">Reflectance</span> and <span class="hlt">MODIS</span> BRDF</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Shuai, Yanmin; Masek, Jeffrey G.; Gao, Feng; Schaaf, Crystal B.</p> <p>2011-01-01</p> <p>We present a new methodology to generate 30-m resolution land surface albedo using Landsat surface <span class="hlt">reflectance</span> and anisotropy information from concurrent <span class="hlt">MODIS</span> 500-m observations. Albedo information at fine spatial resolution is particularly useful for quantifying climate impacts associated with land use change and ecosystem disturbance. The derived white-sky and black-sky spectral albedos maybe used to estimate actual spectral albedos by taking into account the proportion of direct and diffuse solar radiation arriving at the ground. A further spectral-to-broadband conversion based on extensive radiative transfer simulations is applied to produce the broadband albedos at visible, near infrared, and shortwave regimes. The accuracy of this approach has been evaluated using 270 Landsat scenes covering six field stations supported by the SURFace RADiation Budget Network (SURFRAD) and Atmospheric Radiation Measurement Southern Great Plains (ARM/SGP) network. Comparison with field measurements shows that Landsat 30-m snow-free shortwave albedos from all seasons generally achieve an absolute accuracy of +/-0.02 - 0.05 for these validation sites during available clear days in 2003-2005,with a root mean square error less than 0.03 and a bias less than 0.02. This level of accuracy has been regarded as sufficient for driving global and regional climate models. The Landsat-based retrievals have also been compared to the operational 16-day <span class="hlt">MODIS</span> albedo produced every 8-days from <span class="hlt">MODIS</span> on Terra and <span class="hlt">Aqua</span> (MCD43A). The Landsat albedo provides more detailed landscape texture, and achieves better agreement (correlation and dynamic range) with in-situ data at the validation stations, particularly when the stations include a heterogeneous mix of surface covers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008SPIE.7081E..0AC','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008SPIE.7081E..0AC"><span id="translatedtitle">On-orbit <span class="hlt">aqua</span> <span class="hlt">MODIS</span> modulation transfer function trending in along-scan from the Spectro-Radiometric Calibration Assembly</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Choi, Taeyoung; Che, Nianzeng; Xiong, Xiaoxiong</p> <p>2008-08-01</p> <p>The Spectro-Radiometric Calibration Assembly (SRCA) is one of the on-board calibrators for the <span class="hlt">MODIS</span> instrument. The SRCA is operated in three modes: spectral, spatial, and radiometric. The spatial mode is used to track the changes in band-to-band registration both along-scan (band and detector) and along-track (band) and the MTF in the along-scan direction for all 36 <span class="hlt">MODIS</span> bands over the <span class="hlt">MODIS</span> lifetime. In the SRCA spatial mode, a rectangular knife-edge reticle, located at the focus of the SRCA collimator, is imaged onto four <span class="hlt">MODIS</span> Focal Plane Assemblies (FPA). The reticle is illuminated by a spherical integration sphere and a glow-bar so that all bands can have an appropriate signal level. When the <span class="hlt">MODIS</span> scan mirror rotates, the illuminated knife-edge scans across the bands/detectors. In addition, there are five electronic phase-delays so that the sampling spacing is reduced to 1/5 of the detector size, which results in dense data points. After combining detector responses from all phase-delays, a combined bell-shaped response profile is formed. The derivative of the detector response to the knife-edge is the Line Spread Function (LSF). In the frequency domain, the Modulation Transfer Functions (MTF) are calculated from the normalized Fourier transform of the LSF. The MTF results from the SRCA are validated by the pre-launch results from the Integrated Alignment Collimator (IAC) and a SRCA collection performed in the Thermal Vacuum (TV). The six-year plus on-orbit MTF trending results show very stable responses in the VIS and NIR FPAs, and meet the design specifications. Although there are noticeable MTF degradations over the instrument lifetime in bands 1 and 2, they are negligible with the large specification margins. In addition, a similar relationship is found between the band locations in the VIS and NIR FPAs versus MTF values.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.youtube.com/watch?v=P0uVV40Y2Pc','SCIGOVIMAGE-NASA'); return false;" href="http://www.youtube.com/watch?v=P0uVV40Y2Pc"><span id="translatedtitle"><span class="hlt">Aqua</span> satellite orbiting the Earth</span></a></p> <p><a target="_blank" href="http://www.nasa.gov/multimedia/videogallery/index.html">NASA Video Gallery</a></p> <p></p> <p></p> <p>This animation shows the <span class="hlt">Aqua</span> satellite orbiting the Earth on August 27, 2005 by revealing <span class="hlt">MODIS</span> true-color imagery for that day. This animation is on a cartesian map projection, so the satellite w...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=328370','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=328370"><span id="translatedtitle">Compositing <span class="hlt">MODIS</span> Terra and <span class="hlt">Aqua</span> 250m daily surface <span class="hlt">reflectance</span> data sets for vegetation monitoring</span></a></p> <p><a target="_blank" href="http://www.ars.usda.gov/services/TekTran.htm">Technology Transfer Automated Retrieval System (TEKTRAN)</a></p> <p></p> <p></p> <p>Remote sensing based vegetation Indices have been proven valuable in providing a spatially complete view of crop’s vegetation condition, which also manifests the impact of the disastrous events such as massive flood and drought. VegScape, a web GIS application for crop vegetation condition monitorin...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15..705G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15..705G"><span id="translatedtitle">Inter-annual variability of aerosol optical depth over the tropical Atlantic Ocean based on <span class="hlt">MODIS-Aqua</span> observations over the period 2002-2012</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gkikas, Antonis; Hatzianastassiou, Nikolaos</p> <p>2013-04-01</p> <p>The tropical Atlantic Ocean is affected by dust and biomass burning aerosol loads transported from the western parts of the Saharan desert and the sub-Sahel regions, respectively. The spatial and temporal patterns of this transport are determined by the aerosol emission rates, their deposition (wet and dry), by the latitudinal shift of the Intertropical Convergence Zone (ITCZ) and the prevailing wind fields. More specifically, in summer, Saharan dust aerosols are transported towards the Atlantic Ocean, even reaching the Gulf of Mexico, while in winter the Atlantic Ocean transport takes place in more southern latitudes, near the equator, sometimes reaching the northern parts of South America. In the later case, dust is mixed with biomass burning aerosols originating from agricultural activities in the sub-Sahel, associated with prevailing north-easterly airflow (Harmattan winds). Satellite observations are the appropriate tool for describing this African aerosol export, which is important to atmospheric, oceanic and climate processes, offering the advantage of complete spatial coverage. In the present study, we use satellite measurements of aerosol optical depth at 550nm (AOD550nm), on a daily and monthly basis, derived from <span class="hlt">MODIS-Aqua</span> platform, at 1ox1o spatial resolution (Level 3), for the period 2002-2012. The primary objective is to determine the pixel-level and regional mean anomalies of AOD550nm over the entire study period. The regime of the anomalies of African export is interpreted in relation to the aerosol source areas, precipitation, wind patterns and temporal variability of the North Atlantic Oscillation Index (NAOI). In order to ensure availability of AOD over the Sahara desert, <span class="hlt">MODIS-Aqua</span> Deep Blue products are also used. As for precipitation, Global Precipitation Climatology Project (GPCP) data at 2.5ox2.5o are used. The wind fields are taken from the National Center for Environmental Prediction (NCEP). Apart from the regime of African aerosol export</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110023376','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110023376"><span id="translatedtitle"><span class="hlt">MODIS</span> Radiometric Calibration and Uncertainty Assessment</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Xiong, Xiaoxiong; Chiang, Vincent; Sun, Junqiang; Wu, Aisheng</p> <p>2011-01-01</p> <p>Since launch, Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> have collected more than II and 9 years of datasets for comprehensive studies of the Earth's land, ocean, and atmospheric properties. <span class="hlt">MODIS</span> observations are made in 36 spectral bands: 20 <span class="hlt">reflective</span> solar bands (RSB) and 16 thermal emissive bands (TEB). Compared to its heritage sensors, <span class="hlt">MODIS</span> was developed with very stringent calibration and uncertainty requirements. As a result, <span class="hlt">MODIS</span> was designed and built with a set of state of the art on-board calibrators (OBC), which allow key sensor performance parameters and on-orbit calibration coefficients to be monitored and updated if necessary. In terms of its calibration traceability, <span class="hlt">MODIS</span> RSB calibration is <span class="hlt">reflectance</span> based using an on-board solar diffuser (SD) and the TEB calibration is radiance based using an on-board blackbody (BB). In addition to on-orbit calibration coefficients derived from its OBC, calibration parameters determined from sensor pre-launch calibration and characterization are used in both the RSB and TEB calibration and retrieval algorithms. This paper provides a brief description of <span class="hlt">MODIS</span> calibration methodologies and discusses details of its on-orbit calibration uncertainties. It assesses uncertainty contributions from individual components and differences between Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> due to their design characteristics and on-orbit periormance. Also discussed in this paper is the use of <span class="hlt">MODIS</span> LIB uncertainty index CUI) product.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140013366','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140013366"><span id="translatedtitle">Multitemporal Cross-Calibration of the Terra <span class="hlt">MODIS</span> and Landsat 7 ETM+ <span class="hlt">Reflective</span> Solar Bands</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Angal, Amit; Xiong, Xiaoxiong; Wu, Aisheng; Changler, Gyanesh; Choi, Taeyoyung</p> <p>2013-01-01</p> <p>In recent years, there has been a significant increase in the use of remotely sensed data to address global issues. With the open data policy, the data from the Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) and Enhanced Thematic Mapper Plus (ETM+) sensors have become a critical component of numerous applications. These two sensors have been operational for more than a decade, providing a rich archive of multispectral imagery for analysis of mutitemporal remote sensing data. This paper focuses on evaluating the radiometric calibration agreement between <span class="hlt">MODIS</span> and ETM+ using the near-simultaneous and cloud-free image pairs over an African pseudo-invariant calibration site, Libya 4. To account for the combined uncertainties in the top-of-atmosphere (TOA) <span class="hlt">reflectance</span> due to surface and atmospheric bidirectional <span class="hlt">reflectance</span> distribution function (BRDF), a semiempirical BRDF model was adopted to normalize the TOA <span class="hlt">reflectance</span> to the same illumination and viewing geometry. In addition, the spectra from the Earth Observing-1 (EO-1) Hyperion were used to compute spectral corrections between the corresponding <span class="hlt">MODIS</span> and ETM+ spectral bands. As EO-1 Hyperion scenes were not available for all <span class="hlt">MODIS</span> and ETM+ data pairs, MODerate resolution atmospheric TRANsmission (MODTRAN) 5.0 simulations were also used to adjust for differences due to the presence or lack of absorption features in some of the bands. A <span class="hlt">MODIS</span> split-window algorithm provides the atmospheric water vapor column abundance during the overpasses for the MODTRAN simulations. Additionally, the column atmospheric water vapor content during the overpass was retrieved using the <span class="hlt">MODIS</span> precipitable water vapor product. After performing these adjustments, the radiometric cross-calibration of the two sensors was consistent to within 7%. Some drifts in the response of the bands are evident, with <span class="hlt">MODIS</span> band 3 being the largest of about 6% over 10 years, a change that will be corrected in Collection 6 <span class="hlt">MODIS</span> processing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006SPIE.6296E..12D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006SPIE.6296E..12D"><span id="translatedtitle">Validation of large-footprint <span class="hlt">reflectance</span>-based calibration using coincident <span class="hlt">MODIS</span> and ASTER data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>D'Amico, J.; Thome, K.; Czapla-Myers, J.</p> <p>2006-08-01</p> <p>The Remote Sensing Group at the University of Arizona has been using <span class="hlt">reflectance</span>-based vicarious calibration of earth-observing satellites since the 1980s. Among the sensors characterized by the group are the Advanced Spaceborne Thermal Emission and <span class="hlt">Reflection</span> Radiometer (ASTER) and the MODerate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) that are both on NASA's Terra platform. The spatial resolution of <span class="hlt">MODIS</span> requires that the group use a large-sized site such as Railroad Valley Playa, Nevada as a test site. In addition, the large footprint size of <span class="hlt">MODIS</span> forced a modification to the ground-sampling scheme for the surface <span class="hlt">reflectance</span> retrieval. This work examines the impact of the new sampling scheme through coincident ASTER and <span class="hlt">MODIS</span> imagery making use of the higher resolution spatial resolution of ASTER. ASTER and <span class="hlt">MODIS</span> imagery were obtained for dates on which both sensors imaged the Railroad Valley test site and ground-based data were collected at the site. The results of the comparison between the sensors shows differences in the radiometric calibration that exceed the accuracy requirements of the sensors, but that the sampling strategy for large-footprint sensors produces <span class="hlt">reflectance</span>-based results at the same 3% level of accuracy as that for small-footprint sensors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130014484','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130014484"><span id="translatedtitle">Comparison Between NPP-VIIRS Aerosol Data Products and the <span class="hlt">MODIS</span> <span class="hlt">AQUA</span> Deep Blue Collection 6 Dataset Over Land</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sayer, Andrew M.; Hsu, N. C.; Bettenhausen, C.; Lee, J.; Kondragunta, S.</p> <p>2013-01-01</p> <p>Aerosols are small particles suspended in the atmosphere and have a variety of natural and man-made sources. Knowledge of aerosol optical depth (AOD), which is a measure of the amount of aerosol in the atmosphere, and its change over time, is important for multiple reasons. These include climate change, air quality (pollution) monitoring, monitoring hazards such as dust storms and volcanic ash, monitoring smoke from biomass burning, determining potential energy yields from solar plants, determining visibility at sea, estimating fertilization of oceans and rainforests by transported mineral dust, understanding changes in weather brought upon by the interaction of aerosols and clouds, and more. The Suomi-NPP satellite was launched late in 2011. The Visible Infrared Imaging Radiometer Suite (VIIRS) aboard Suomi-NPP is being used, among other things, to determine AOD. This study compares the VIIRS dataset to ground-based measurements of AOD, along with a state-of-the-art satellite AOD dataset (the new version of the Moderate Resolution Imaging Spectrometer Deep Blue algorithm) to assess its reliability. The Suomi-NPP satellite was launched late in 2011, carrying several instruments designed to continue the biogeophysical data records of current and previous satellite sensors. The Visible Infrared Imaging Radiometer Suite (VIIRS) aboard Suomi-NPP is being used, among other things, to determine aerosol optical depth (AOD), and related activities since launch have been focused towards validating and understanding this new dataset through comparisons with other satellite and ground-based products. The operational VIIRS AOD product is compared over land with AOD derived from Moderate Resolution Imaging Spectrometer (<span class="hlt">MODIS</span>) observations using the Deep Blue (DB) algorithm from the forthcoming Collection 6 of <span class="hlt">MODIS</span> data</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110008491','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110008491"><span id="translatedtitle">Biomass Burning Aerosol Absorption Measurements with <span class="hlt">MODIS</span> Using the Critical <span class="hlt">Reflectance</span> Method</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zhu, Li; Martins, Vanderlei J.; Remer, Lorraine A.</p> <p>2010-01-01</p> <p>This research uses the critical <span class="hlt">reflectance</span> technique, a space-based remote sensing method, to measure the spatial distribution of aerosol absorption properties over land. Choosing two regions dominated by biomass burning aerosols, a series of sensitivity studies were undertaken to analyze the potential limitations of this method for the type of aerosol to be encountered in the selected study areas, and to show that the retrieved results are relatively insensitive to uncertainties in the assumptions used in the retrieval of smoke aerosol. The critical <span class="hlt">reflectance</span> technique is then applied to Moderate Resolution Imaging Spectrometer (<span class="hlt">MODIS</span>) data to retrieve the spectral aerosol single scattering albedo (SSA) in South African and South American 35 biomass burning events. The retrieved results were validated with collocated Aerosol Robotic Network (AERONET) retrievals. One standard deviation of mean <span class="hlt">MODIS</span> retrievals match AERONET products to within 0.03, the magnitude of the AERONET uncertainty. The overlap of the two retrievals increases to 88%, allowing for measurement variance in the <span class="hlt">MODIS</span> retrievals as well. The ensemble average of <span class="hlt">MODIS</span>-derived SSA for the Amazon forest station is 0.92 at 670 nm, and 0.84-0.89 for the southern African savanna stations. The critical <span class="hlt">reflectance</span> technique allows evaluation of the spatial variability of SSA, and shows that SSA in South America exhibits higher spatial variation than in South Africa. The accuracy of the retrieved aerosol SSA from <span class="hlt">MODIS</span> data indicates that this product can help to better understand 44 how aerosols affect the regional and global climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/22473302','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22473302"><span id="translatedtitle">Variation of <span class="hlt">MODIS</span> <span class="hlt">reflectance</span> and vegetation indices with viewing geometry and soybean development.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Breunig, Fábio M; Galvão, Lênio S; Formaggio, Antônio R; Epiphanio, José C N</p> <p>2012-06-01</p> <p>Directional effects introduce a variability in <span class="hlt">reflectance</span> and vegetation index determination, especially when large field-of-view sensors are used (e.g., Moderate Resolution Imaging Spectroradiometer - <span class="hlt">MODIS</span>). In this study, we evaluated directional effects on <span class="hlt">MODIS</span> <span class="hlt">reflectance</span> and four vegetation indices (Normalized Difference Vegetation Index - NDVI; Enhanced Vegetation Index - EVI; Normalized Difference Water Index - NDWI(1640) and NDWI(2120)) with the soybean development in two growing seasons (2004-2005 and 2005-2006). To keep the reproductive stage for a given cultivar as a constant factor while varying viewing geometry, pairs of images obtained in close dates and opposite view angles were analyzed. By using a non-parametric statistics with bootstrapping and by normalizing these indices for angular differences among viewing directions, their sensitivities to directional effects were studied. Results showed that the variation in <span class="hlt">MODIS</span> <span class="hlt">reflectance</span> between consecutive phenological stages was generally smaller than that resultant from viewing geometry for closed canopies. The contrary was observed for incomplete canopies. The <span class="hlt">reflectance</span> of the first seven <span class="hlt">MODIS</span> bands was higher in the backscattering. Except for the EVI, the other vegetation indices had larger values in the forward scattering direction. Directional effects decreased with canopy closure. The NDVI was lesser affected by directional effects than the other indices, presenting the smallest differences between viewing directions for fixed phenological stages. PMID:22473302</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140010301','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140010301"><span id="translatedtitle">The Normalization of Surface Anisotropy Effects Present in SEVIRI <span class="hlt">Reflectances</span> by Using the <span class="hlt">MODIS</span> BRDF Method</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Proud, Simon Richard; Zhang, Qingling; Schaaf, Crystal; Fensholt, Rasmus; Rasmussen, Mads Olander; Shisanya, Chris; Mutero, Wycliffe; Mbow, Cheikh; Anyamba, Assaf; Pak, Ed; Sandholt, Inge</p> <p>2014-01-01</p> <p>A modified version of the MODerate resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) bidirectional <span class="hlt">reflectance</span> distribution function (BRDF) algorithm is presented for use in the angular normalization of surface <span class="hlt">reflectance</span> data gathered by the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) aboard the geostationary Meteosat Second Generation (MSG) satellites. We present early and provisional daily nadir BRDFadjusted <span class="hlt">reflectance</span> (NBAR) data in the visible and near-infrared MSG channels. These utilize the high temporal resolution of MSG to produce BRDF retrievals with a greatly reduced acquisition period than the comparable <span class="hlt">MODIS</span> products while, at the same time, removing many of the angular perturbations present within the original MSG data. The NBAR data are validated against <span class="hlt">reflectance</span> data from the <span class="hlt">MODIS</span> instrument and in situ data gathered at a field location in Africa throughout 2008. It is found that the MSG retrievals are stable and are of high-quality across much of the SEVIRI disk while maintaining a higher temporal resolution than the <span class="hlt">MODIS</span> BRDF products. However, a number of circumstances are discovered whereby the BRDF model is unable to function correctly with the SEVIRI observations-primarily because of an insufficient spread of angular data due to the fixed sensor location or localized cloud contamination.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150019885','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150019885"><span id="translatedtitle"><span class="hlt">MODIS</span> Instrument Operation and Calibration Improvements</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Xiong, X.; Angal, A.; Madhavan, S.; Link, D.; Geng, X.; Wenny, B.; Wu, A.; Chen, H.; Salomonson, V.</p> <p>2014-01-01</p> <p>Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> have successfully operated for over 14 and 12 years since their respective launches in 1999 and 2002. The <span class="hlt">MODIS</span> on-orbit calibration is performed using a set of on-board calibrators, which include a solar diffuser for calibrating the <span class="hlt">reflective</span> solar bands (RSB) and a blackbody for the thermal emissive bands (TEB). On-orbit changes in the sensor responses as well as key performance parameters are monitored using the measurements of these on-board calibrators. This paper provides an overview of <span class="hlt">MODIS</span> on-orbit operation and calibration activities, and instrument long-term performance. It presents a brief summary of the calibration enhancements made in the latest <span class="hlt">MODIS</span> data collection 6 (C6). Future improvements in the <span class="hlt">MODIS</span> calibration and their potential applications to the S-NPP VIIRS are also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.H34A..07M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.H34A..07M"><span id="translatedtitle">Detection of Harmful Algal Blooms in the Optically Complex Coastal Waters of the Kuwait Bay using <span class="hlt">Aqua-MODIS</span> data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Manche, C. J.; Sultan, M.; Uddin, S.; Al-Dousari, A.; Chouinard, K.</p> <p>2013-12-01</p> <p>In the optically complex coastal marine waters of the Kuwait Bay, the propagation of Harmful Algal Blooms (HABs) has become a severe issue over the last decade affecting aquaculture a primary component of the Kuwaiti economy. Although several remote sensing based methods of algal bloom detection exist today, few may accurately detect the concentration and identify the type of HABs in Case II waters. The purpose of this study is: (1) assessment of the method that best detects and identifies algal blooms in general and HABs in particular, in the Kuwait Bay, and (2) identification of the factors controlling the occurrence of HABs. Fluorescence Line Height (FLH), Empirical, Bio-Optical, and Operational Methods as well as Ocean Colour 3 Band Ratio (OC3M), Garver-Siegel-Maritorena Model (GSM), and General Inherent Optical Property (GIOP) Chlorophyll-a (Chl-a) algorithms were applied to Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) images acquired (07/2002 to 07/2012) over the Kuwait Bay and areas as far east as Shatt Al-Arab and as far south as N. 29.284 (Lat.), E. 50.047 (Long.) decimal degrees. In-situ data (bloom days: 50; sampling locations: 64) collected (09/1999 to 07/2011) from the Kuwait Bay was provided by the Kuwait Institute for Scientific Research and was used to test the reliability of the satellite-based inferences. Tasks accomplished and findings reached include: (1) comparison of in situ to estimated OC3M, GSM, and GIOP chlorophyll concentrations over the sampling locations for the time period 2002 to 2009 showed that OC3M outperformed the two other techniques in predicting the observed distribution and in replicating the measured concentration of the in-situ Chl-a data; (2) applying the OC3M algorithm to a total of 4039 scenes and using threshold values of 3, 4, and 5 mg/m3 Chl-a concentrations we inferred 371, 202, and 124 occurrences in the Kuwait Bay that met their respective threshold; (3) applying the operational method we successfully</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.B54C..04D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.B54C..04D"><span id="translatedtitle">Validating the simulation of optical <span class="hlt">reflectance</span> by a vertically resolved canopy biophysics model with <span class="hlt">MODIS</span> daily observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Drewry, D. T.; Duveiller, G.</p> <p>2012-12-01</p> <p>Agricultural modeling and yield forecasting are complicated by seasonal variability in traits controlled by factors such as growth stage, nutrient availability and moisture status. While a new generation of vegetation models incorporate ecophysiological details that allow for accurate estimates of carbon uptake, water use and energy exchange, these increases in process-level detail have resulted in the requirement to estimate a broader set of model parameters. Constraining uncertainties in model estimates of productivity and water use requires periodic updates as the structural and physiological status of the vegetation varies over the growing season. Here we explore the utilization of remote sensing <span class="hlt">reflectance</span> observations in the optical domain collected from the <span class="hlt">MODIS</span> sensors onboard the Terra and <span class="hlt">Aqua</span> satellites for constraining key canopy states and reducing the uncertainty in modeled CO2, water and energy exchange with the atmosphere. At the core of this approach is a vertically discretized model (MLCan) that characterizes the ecophysiological functioning of a plant canopy and its biophysical coupling to the ambient environment at a half-hourly timestep. Above-ground vegetation is partially controlled by a root system model that simulates moisture uptake in a multi-layer soil system. MLCan has been rigorously validated for both C3 and C4 crops against field- and leaf-scale observations of canopy CO2 uptake, evapotranspiration and sensible heat exchange across a wide range of meteorological conditions in both ambient and elevated CO2 environments. A widely utilized radiation transfer model (PROSAIL) that accounts for the effects of leaf-level optical properties and foliage distribution and orientation on canopy <span class="hlt">reflectance</span> is coupled to MLCan. This coupling provides the capability of expanding the spectral resolution of the model to nm-scale over the optical range. The coupled model will provide a system for testing the links between plant canopy biochemical</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011lrsg.book..533V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011lrsg.book..533V"><span id="translatedtitle"><span class="hlt">MODIS</span> Directional Surface <span class="hlt">Reflectance</span> Product: Method, Error Estimates and Validation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vermote, Eric; Kotchenova, Svetlana</p> <p></p> <p>The surface bidirectional <span class="hlt">reflectance</span> factor (BRF) is the ratio between <span class="hlt">reflected</span> radiance measured in specific observation geometry (zenith and azimuth) within an infinitely small solid angle and irradiance incident on the surface from a direct source of illumination (zenith and azimuth). The BRF is determined from satellite observations through an atmospheric correction (AC) process. When properly retrieved, the surface BRF is fully decoupled from an atmospheric signal, and thus represents the value as measured by an ideal sensor held at the same view geometry and located just above the Earth's surface assuming an absence of atmosphere.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_6 --> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140010322','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140010322"><span id="translatedtitle">Daily <span class="hlt">MODIS</span> 500 m <span class="hlt">Reflectance</span> Anisotropy Direct Broadcast (DB) Products for Monitoring Vegetation Phenology Dynamics</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Shuai, Yanmin; Schaaf, Crystal; Zhang, Xiaoyang; Strahler, Alan; Roy, David; Morisette, Jeffrey; Wang, Zhuosen; Nightingale, Joanne; Nickeson, Jaime; Richardson, Andrew D.; Xie, Donghui; Wang, Jindi; Li, Xiaowen; Strabala, Kathleen; Davies, James E.</p> <p>2013-01-01</p> <p>Land surface vegetation phenology is an efficient bio-indicator for monitoring ecosystem variation in response to changes in climatic factors. The primary objective of the current article is to examine the utility of the daily <span class="hlt">MODIS</span> 500 m <span class="hlt">reflectance</span> anisotropy direct broadcast (DB) product for monitoring the evolution of vegetation phenological trends over selected crop, orchard, and forest regions. Although numerous model-fitted satellite data have been widely used to assess the spatio-temporal distribution of land surface phenological patterns to understand phenological process and phenomena, current efforts to investigate the details of phenological trends, especially for natural phenological variations that occur on short time scales, are less well served by remote sensing challenges and lack of anisotropy correction in satellite data sources. The daily <span class="hlt">MODIS</span> 500 m <span class="hlt">reflectance</span> anisotropy product is employed to retrieve daily vegetation indices (VI) of a 1 year period for an almond orchard in California and for a winter wheat field in northeast China, as well as a 2 year period for a deciduous forest region in New Hampshire, USA. Compared with the ground records from these regions, the VI trajectories derived from the cloud-free and atmospherically corrected <span class="hlt">MODIS</span> Nadir BRDF (bidirectional <span class="hlt">reflectance</span> distribution function) adjusted <span class="hlt">reflectance</span> (NBAR) capture not only the detailed footprint and principal attributes of the phenological events (such as flowering and blooming) but also the substantial inter-annual variability. This study demonstrates the utility of the daily 500 m <span class="hlt">MODIS</span> <span class="hlt">reflectance</span> anisotropy DB product to provide daily VI for monitoring and detecting changes of the natural vegetation phenology as exemplified by study regions comprising winter wheat, almond trees, and deciduous forest.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25781509','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25781509"><span id="translatedtitle">Evaluation and intercomparison of <span class="hlt">MODIS</span> and GEOV1 global leaf area index products over four sites in North China.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, Zhenwang; Tang, Huan; Zhang, Baohui; Yang, Guixia; Xin, Xiaoping</p> <p>2015-01-01</p> <p>This study investigated the performances of the Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) and GEOLAND2 Version 1 (GEOV1) Leaf Area Index (LAI) products using ground measurements and LAI reference maps over four sites in North China for 2011-2013. The Terra + <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> and Terra <span class="hlt">MODIS</span> LAI retrieved by the main algorithm and GEOV1 LAI within the valid range were evaluated and intercompared using LAI reference maps to assess their uncertainty and seasonal variability The results showed that GEOV1 LAI is the most similar product with the LAI reference maps (R2 = 0.78 and RMSE = 0.59). The <span class="hlt">MODIS</span> products performed well for biomes with low LAI values, but considerable uncertainty arose when the LAI was larger than 3. Terra + <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> (R2 = 0.72 and RMSE = 0.68) was slightly more accurate than Terra <span class="hlt">MODIS</span> (R2 = 0.57 and RMSE = 0.90) for producing slightly more successful observations. Both <span class="hlt">MODIS</span> and GEOV1 products effectively followed the seasonal trajectory of the reference maps, and GEOV1 exhibited a smoother seasonal trajectory than <span class="hlt">MODIS</span>. <span class="hlt">MODIS</span> anomalies mainly occurred during summer and likely occurred because of surface <span class="hlt">reflectance</span> uncertainty, shorter temporal resolutions and inconsistency between simulated and <span class="hlt">MODIS</span> surface <span class="hlt">reflectances</span>. This study suggests that further improvements of the <span class="hlt">MODIS</span> LAI products should focus on finer algorithm inputs and improved seasonal variation modeling of <span class="hlt">MODIS</span> observations. Future field work considering finer biome maps and better generation of LAI reference maps is still needed. PMID:25781509</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4435130','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4435130"><span id="translatedtitle">Evaluation and Intercomparison of <span class="hlt">MODIS</span> and GEOV1 Global Leaf Area Index Products over Four Sites in North China</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Li, Zhenwang; Tang, Huan; Zhang, Baohui; Yang, Guixia; Xin, Xiaoping</p> <p>2015-01-01</p> <p>This study investigated the performances of the Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) and GEOLAND2 Version 1 (GEOV1) Leaf Area Index (LAI) products using ground measurements and LAI reference maps over four sites in North China for 2011–2013. The Terra + <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> and Terra <span class="hlt">MODIS</span> LAI retrieved by the main algorithm and GEOV1 LAI within the valid range were evaluated and intercompared using LAI reference maps to assess their uncertainty and seasonal variability The results showed that GEOV1 LAI is the most similar product with the LAI reference maps (R2 = 0.78 and RMSE = 0.59). The <span class="hlt">MODIS</span> products performed well for biomes with low LAI values, but considerable uncertainty arose when the LAI was larger than 3. Terra + <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> (R2 = 0.72 and RMSE = 0.68) was slightly more accurate than Terra <span class="hlt">MODIS</span> (R2 = 0.57 and RMSE = 0.90) for producing slightly more successful observations. Both <span class="hlt">MODIS</span> and GEOV1 products effectively followed the seasonal trajectory of the reference maps, and GEOV1 exhibited a smoother seasonal trajectory than <span class="hlt">MODIS</span>. <span class="hlt">MODIS</span> anomalies mainly occurred during summer and likely occurred because of surface <span class="hlt">reflectance</span> uncertainty, shorter temporal resolutions and inconsistency between simulated and <span class="hlt">MODIS</span> surface <span class="hlt">reflectances</span>. This study suggests that further improvements of the <span class="hlt">MODIS</span> LAI products should focus on finer algorithm inputs and improved seasonal variation modeling of <span class="hlt">MODIS</span> observations. Future field work considering finer biome maps and better generation of LAI reference maps is still needed. PMID:25781509</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1715789K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1715789K"><span id="translatedtitle">The regime of aerosol asymmetry parameter and Angstrom exponent over Europe, Mediterranean and Middle East based on <span class="hlt">MODIS</span> satellite data. Intercomparison of <span class="hlt">MODIS-Aqua</span> C051 and C006 retrievals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Korras-Carraca, Marios Bruno; Hatzianastassiou, Nikolaos; Matsoukas, Christos; Gkikas, Antonis; Papadimas, Christos; Sayers, Andy</p> <p>2015-04-01</p> <p>Atmospheric aerosols, both natural and anthropogenic, can cause climate change through their direct, indirect, and semi-direct effects on the radiative energy budget of the Earth-atmosphere system. In the present work, we study two of the most important optical properties of aerosols, the asymmetry parameter (gaer) and the Angstrom exponent (α). Both gaer and α are related with aerosol size, which is a very important parameter for climate and human health. The study region comprises North Africa, the Arabian peninsula, Europe, and the Mediterranean basin. These areas are of great interest, because of the variety of aerosol types they host, both anthropogenic and natural. Urban, industrial or biomass-burning aerosols are usually fine, while desert dust or sea-salt are basically coarse, making thus possible the establishment of a relationship between the type and the size of aerosols. Using satellite data from the collection 051 of <span class="hlt">MODIS</span> (MODerate resolution Imaging Spectroradiometer, <span class="hlt">Aqua</span>), we investigate the spatio-temporal characteristics of the asymmetry parameter and Angstrom exponent. We generally find significant spatial variability, with larger gaer values over regions dominated by larger size particles, e.g. outside the Atlantic coasts of north-western Africa, where desert-dust outflow is taking place. The gaer values tend to decrease with increasing wavelength, especially over areas dominated by small particulates. The intra-annual variability is found to be small in desert-dust areas, with maximum values during summer, while in all other areas larger values are reported during the cold season and smaller during the warm. Significant intra-annual and inter-annual variability is observed around the Black Sea. However, the inter-annual trends of gaer are found to be generally small. The geographical distributions for α (given for the pair of wavelengths 550-865 nm) affirm the conclusions drawn from the asymmetry parameter as regards the aerosol size over</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1812221C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1812221C"><span id="translatedtitle">On the assimilation of <span class="hlt">MODIS</span> <span class="hlt">reflectance</span> into a detailed snowpack model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Charrois, Luc; Dumont, Marie; Cosme, Emmanuel; Lafaysse, Matthieu; Morin, Samuel; Libois, Quentin; Picard, Ghislain</p> <p>2016-04-01</p> <p>One of the major sources of uncertainty in detailed snowpack simulations lies in the quality of meteorological forcings. The limited spatial resolution of common reanalysis and forecast data used as inputs for snowpack models usually makes it difficult to simulate the local horizontal heterogeneity of snowpack physical properties, especially in mountainous areas. Using satellite data to incorporate snowpack state observations into the simulations appears as an alluring way to improve the snow simulations, to account for spatial variability and to mitigate the impact of meteorological forcings uncertainties. This work presents an original study of the impact of the assimilation of visible and near-infrared <span class="hlt">reflectances</span> into the detailed snowpack model SURFEX/ISBA-Crocus. We performed ensemble simulations by perturbing the atmospheric forcing consistently with its estimated uncertainty. In a first step, we performed assimilation experiments with synthetic imager (<span class="hlt">MODIS</span> like) observations and a particle filter. The experiments were carried out at Col du Lautaret area (2100 m altitude, French Alps) over 5 hydrologic seasons. They provide a good insight about the potential and limitations of assimilating imager data to improve the representation of the snowpack. In particular, they demonstrate the significance of the temporal distribution of the observation to assimilate. In a second step, we assimilated actual <span class="hlt">MODIS</span> data and evaluated the impact of the assimilation using snow measurements acquired during one winter season at Col du Lautaret. These real experiments enlighten the need for a relevant screening method for <span class="hlt">MODIS</span> <span class="hlt">reflectances</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.usgs.gov/of/2010/1055/','USGSPUBS'); return false;" href="http://pubs.usgs.gov/of/2010/1055/"><span id="translatedtitle">e<span class="hlt">MODIS</span>: A User-Friendly Data Source</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Jenkerson, Calli; Maiersperger, Thomas; Schmidt, Gail</p> <p>2010-01-01</p> <p>The U.S. Geological Survey's (USGS) Earth Resources Observation and Science (EROS) Center is generating a suite of products called 'e<span class="hlt">MODIS</span>' based on Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) data acquired by the National Aeronautics and Space Administration's (NASA) Earth Observing System (EOS). With a more frequent repeat cycle than Landsat and higher spatial resolutions than the Advanced Very High Resolution Spectroradiometer (AVHRR), <span class="hlt">MODIS</span> is well suited for vegetation studies. For operational monitoring, however, the benefits of <span class="hlt">MODIS</span> are counteracted by usability issues with the standard map projection, file format, composite interval, high-latitude 'bow-tie' effects, and production latency. e<span class="hlt">MODIS</span> responds to a community-specific need for alternatively packaged <span class="hlt">MODIS</span> data, addressing each of these factors for real-time monitoring and historical trend analysis. e<span class="hlt">MODIS</span> processes calibrated radiance data (level-1B) acquired by the <span class="hlt">MODIS</span> sensors on the EOS Terra and <span class="hlt">Aqua</span> satellites by combining <span class="hlt">MODIS</span> Land Science Collection 5 Atmospherically Corrected Surface <span class="hlt">Reflectance</span> production code and USGS EROS <span class="hlt">MODIS</span> Direct Broadcast System (DBS) software to create surface <span class="hlt">reflectance</span> and Normalized Difference Vegetation Index (NDVI) products. e<span class="hlt">MODIS</span> is produced over the continental United States and over Alaska extending into Canada to cover the Yukon River Basin. The 250-meter (m), 500-m, and 1,000-m products are delivered in Geostationary Earth Orbit Tagged Image File Format (Geo- TIFF) and composited in 7-day intervals. e<span class="hlt">MODIS</span> composites are projected to non-Sinusoidal mapping grids that best suit the geography in their areas of application (see e<span class="hlt">MODIS</span> Product Description below). For e<span class="hlt">MODIS</span> products generated over the continental United States (e<span class="hlt">MODIS</span> CONUS), the Terra (from 2000) and <span class="hlt">Aqua</span> (from 2002) records are available and continue through present time. e<span class="hlt">MODIS</span> CONUS also is generated in an expedited process that delivers a 7-day rolling composite</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A33E0223X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A33E0223X"><span id="translatedtitle">Status of <span class="hlt">MODIS</span> Instruments and Future Calibration Improvements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiong, X.; Angal, A.; Wu, A.; Salomonson, V. V.</p> <p>2015-12-01</p> <p><span class="hlt">MODIS</span> is one of the key instruments currently operated on two major missions for the NASA's Earth Observing System (EOS) program: Terra and <span class="hlt">Aqua</span> launched in 1999 and 2002, respectively. Nearly 40 data products have been routinely generated from both Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> observations and widely distributed to the science community and users worldwide for their studies of the earth's system and changes in its geophysical properties. To date, each <span class="hlt">MODIS</span> instrument operation remains nominal and its on-board calibrators (OBC) continue to function satisfactorily. On a regular basis, <span class="hlt">MODIS</span> <span class="hlt">reflective</span> solar bands (RSB) calibration is performed by a solar diffuser (SD) and a solar diffuser stability monitor (SDSM). For the thermal emissive bands (TEB), an on-board blackbody (BB) provides a scan-by-scan calibration reference. Since launch, extensive calibration and characterization activities have been scheduled and implemented by the <span class="hlt">MODIS</span> Characterization Support Team (MCST) to produce and update calibration look-up tables (LUT). This presentation provides an overview of both Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> instrument status, their on-orbit operation and calibration activities, and radiometric, spectral, and spatial performance. It describes calibration changes (algorithms and look-up tables) made for the <span class="hlt">MODIS</span> Level 1B (L1B) data collection 6 (C6) and discusses remaining challenging issues and ongoing effort for future improvements. As expected, lessons from both Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> have benefitted and will continue to help the S-NPP and JPSS VIIRS instruments in terms of on-orbit operation strategies and calibration enhancements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A14C..05V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A14C..05V"><span id="translatedtitle">Transitioning <span class="hlt">MODIS</span> to VIIRS observations for Land: Surface <span class="hlt">Reflectance</span> results, Status and Long-term Prospective</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vermote, E.</p> <p>2015-12-01</p> <p>Surface <span class="hlt">reflectance</span> is one of the key products from VIIRS and as with <span class="hlt">MODIS</span>, is used in developing several higher-order land products. The VIIRS Surface <span class="hlt">Reflectance</span> (SR) IP is based on the heritage <span class="hlt">MODIS</span> Collection 5 product (Vermote et al. 2002). The quality and character of surface <span class="hlt">reflectance</span> depends on the accuracy of the VIIRS Cloud Mask (VCM) and aerosol algorithms and of course on the adequate calibration of the sensor. Early evaluation of the VIIRS SR product in the context of the maturity of the operational processing system known as the Interface Data Processing System (IDPS), has been a major focus of work to-date, but is now evolving into the development of a VIIRS suite of Climate Data Records produced by the NASA Land Science Investigator Processing System (SIPS). We will present the calibration performance and the role of the surface <span class="hlt">reflectance</span> in calibration monitoring, the performance of the cloud mask with a focus on vegetation monitoring (no snow conditions), the performance of the aerosol input used in the atmospheric correction with quantitative results of the performance of the SR product over AERONET sites. Based on those elements and further assessment, we will address the readiness of the SR product for the production of higher-order land products such as Vegetation Indices, Albedo and LAI/FPAR, the its application to agricultural monitoring and in particular the integration of VIIRS data into the global agricultural monitoring (GLAM) system developed at UMd. Finally from the lessons learned, we will articulate a set of critical recommendations to ensure consistency and continuity of the JPSS mission with the <span class="hlt">MODIS</span> data record.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.B41C0387S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.B41C0387S"><span id="translatedtitle">Collection 5 <span class="hlt">MODIS</span> LAI/FPAR Products</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Samanta, A.; Ganguly, S.; Schull, M. A.; Shabanov, N. V.; Knyazikhin, Y.; Myneni, R. B.</p> <p>2008-12-01</p> <p><span class="hlt">MODIS</span> LAI algorithm was substantially refined for the Collection 5 reprocessing to optimally use suite of <span class="hlt">MODIS</span> observations from Terra and <span class="hlt">Aqua</span> sensors. Refinements are based on advancements in RT theory, analysis of former versions of global time series of LAI product and product validation with field measurements. The Look-up-tables were regenerated for all vegetation types based on a new Stochastic RT model. The Collection 5 suite of LAI/FPAR products possesses higher quality retrievals than previous versions. The following 1-km products are operationally generated at NASA Science Computing Facilities (SCF): 8-day Terra and <span class="hlt">Aqua</span> products, 8-days Combined Terra and <span class="hlt">Aqua</span> product, and 4-day Combined Terra and <span class="hlt">Aqua</span> product. In addition, monthly Collection 5 Terra products are processed and archived at the Boston University (BU) SCF. In this study, we analyzed Collection 5 LAI/FPAR products over a range of spatial scales: Global, North American continent (single composite during the growing season), at scale of <span class="hlt">MODIS</span> tile (annual time series for three <span class="hlt">MODIS</span> tiles), and at the scale of validation sites (annual time series for three sites). For analysis we used Collection 5 BU monthly Terra products. The LAI retrieval algorithm consists of two parts: main (Radiative Transfer based) and back-up (empirical). The BU monthly compositing scheme consists of 3 main steps: 1) selection of data from 8-day MOD15A2 product; 2) assembling tile data into global map based on a global land cover; and 3) degrading from 1km resolution to 4km resolution. We focused on the following: 1) Enhancement in the number of high quality retrievals in Collection 5; 2) Utility of the product to improve retrievals under atmospheric contamination of surface <span class="hlt">reflectance</span> (clouds, aerosols) and for dense vegetation under saturation of surface <span class="hlt">reflectance</span>; 3) Utility of the product to improve temporal resolution of retrievals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998SPIE.3439..257P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998SPIE.3439..257P"><span id="translatedtitle">Bidirectional <span class="hlt">reflectance</span> factor (BRF) characterization of the <span class="hlt">MODIS</span> flight solar diffuser</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pavlov, Milutin M.; Byers, Michael L.; Walker, Joe A., Jr.</p> <p>1998-10-01</p> <p>The Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) will be one of the primary instruments observing the earth on the Earth Observing System (EOS) scheduled for launch in late 1999. The solar diffuser BRF characterization is required for <span class="hlt">MODIS</span> on-orbit <span class="hlt">reflectance</span> calibration. The system <span class="hlt">reflectance</span> calibration accuracy requirement is 2 percent covering a spectral region of 400 to 2300 nm. An internal flow down specification of 1 percent was allotted to characterization of the BRF. The SBRS scattering goniometer will be described. The source is a quartz-halogen lamp. Multiple field stops, aperture stops, and baffle masks were experimentally optimized to reduce scattered light to acceptable levels. In addition the room was made 'light tight'. Glan Thompson and Wollaston polarizers were used in the illuminating and viewing arms, respectively. Three sets of detectors were used to cover the 400 to 2300 nm range: PMT, Ge, and PbS. The rotary and translation stages used to move the solar diffuser, polarizers, optical filters, and detectors being computer controlled, which permitted measurements to be made remotely. This scattering goniometer is a relative device, so the flight solar diffuser is characterized by measuring it relative to a diffuser which was characterized by NIST. The transfer to the NIST standard was done before and after solar diffuser characterization. BRF measurements were made at five wavelengths and nine illumination angles with one out-of-plane observation angle. Multiple BRF measurements were made to determine repeatability and spatial uniformity. Measured BRF data will be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040035547&hterms=aerosols+desert&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Daerosols%2Bdesert','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040035547&hterms=aerosols+desert&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Daerosols%2Bdesert"><span id="translatedtitle"><span class="hlt">MODIS</span> Retrieval of Dust Aerosol</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Remer, Lorraine A.; Kaufman, Yoram J.; Tanre, Didier</p> <p>2003-01-01</p> <p>The MODerate resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) currently aboard both the Terra and <span class="hlt">Aqua</span> satellites produces a suite of products designed to characterize global aerosol distribution, optical thickness and particle size. Never before has a space-borne instrument been able to provide such detailed information, operationally, on a nearly global basis every day. The three years of Terra-<span class="hlt">MODIS</span> data have been validated by comparing with co-located AERONET observations of aerosol optical thickness and derivations of aerosol size parameters. Some 8000 comparison points located at 133 AERONET sites around the globe show that the <span class="hlt">MODIS</span> aerosol optical thickness retrievals are accurate to within the pre-launch expectations. However, the validation in regions dominated by desert dust is less accurate than in regions dominated by fine mode aerosol or background marine sea salt. The discrepancy is most apparent in retrievals of aerosol size parameters over ocean. In dust situations, the <span class="hlt">MODIS</span> algorithm tends to under predict particle size because the <span class="hlt">reflectances</span> at top of atmosphere measured by <span class="hlt">MODIS</span> exhibit the stronger spectral signature expected by smaller particles. This pattern is consistent with the angular and spectral signature of non-spherical particles. All possible aerosol models in the <span class="hlt">MODIS</span> Look-Up Tables were constructed from Mie theory, assuming a spherical shape. Using a combination of <span class="hlt">MODIS</span> and AERONET observations, in regimes dominated by desert dust, we construct phase functions, empirically, with no assumption of particle shape. These new phase functions are introduced into the <span class="hlt">MODIS</span> algorithm, in lieu of the original options for large dust-like particles. The results will be analyzed and examined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..1111496C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1111496C"><span id="translatedtitle">Actual evapotranspiration estimation in a Mediterranean mountain region by means of Landsat-5 TM and TERRA/<span class="hlt">AQUA</span> <span class="hlt">MODIS</span> imagery and Sap Flow measurements in Pinus sylvestris forest stands.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cristóbal, J.; Poyatos, R.; Ninyerola, M.; Pons, X.; Llorens, P.</p> <p>2009-04-01</p> <p>Evapotranspiration monitoring has important implications on global and regional climate modelling, as well as in the knowledge of the hydrological cycle and in the assessment of environmental stress that affects forest and agricultural ecosystems. An increase of evapotranspiration while precipitation remains constant, or is reduced, could decrease water availability for natural and agricultural systems and human needs. Consequently, water balance methods, as the evapotranspiration modelling, have been widely used to estimate crop and forest water needs, as well as the global change effects. Nowadays, radiometric measurements provided by Remote Sensing and GIS analysis are the technologies used to compute evapotranspiration at regional scales in a feasible way. Currently, the 38% of Catalonia (NE of the Iberian Peninsula) is covered by forests, and one of the most important forest species is Scots Pine (Pinus sylvestris) which represents the 18.4% of the area occupied by forests. The aim of this work is to model actual evapotranspiration in Pinus sylvestris forest stands, in a Mediterranean mountain region, using remote sensing data, and compare it with stand-scale sap flow measurements measured in the Vallcebre research area (42° 12' N, 1° 49' E), in the Eastern Pyrenees. To perform this study a set of 30 cloud-free TERRA-<span class="hlt">MODIS</span> images and 10 Landsat-5 TM images of path 198 and rows 31 and 32 from June 2003 to January 2005 have been selected to perform evapotranspiration modelling in Pinus sylvestris forest stands. TERRA/<span class="hlt">AQUA</span> <span class="hlt">MODIS</span> images have been downloaded by means of the EOS Gateway. We have selected two different types of products which contain the remote sensing data we have used to model daily evapotranspiration, daily LST product and daily calibrated <span class="hlt">reflectances</span> product. Landsat-5 TM images have been corrected by means of conventional techniques based on first order polynomials taking into account the effect of land surface relief using a Digital</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040031528&hterms=Siri&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DSiri','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040031528&hterms=Siri&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DSiri"><span id="translatedtitle">Accessing and Understanding <span class="hlt">MODIS</span> Data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Leptoukh, Gregory; Jenkerson, Calli B.; Jodha, Siri</p> <p>2003-01-01</p> <p>The National Aeronautics and Space Administration (NASA) launched the Terra satellite in December 1999, as part of the Earth Science Enterprise promotion of interdisciplinary studies of the integrated Earth system. <span class="hlt">Aqua</span>, the second satellite from the series of EOS constellation, was launched in May 2002. Both satellites carry the MODerate resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) instrument. <span class="hlt">MODIS</span> data are processed at the Goddard Space Flight Center, Greenbelt, MD, and then archived and distributed by the Distributed Active Archive Centers (DAACs). Data products from the <span class="hlt">MODIS</span> sensors present new challenges to remote sensing scientists due to specialized production level, data format, and map projection. <span class="hlt">MODIS</span> data are distributed as calibrated radiances and as higher level products such as: surface <span class="hlt">reflectance</span>, water-leaving radiances, ocean color and sea surface temperature, land surface kinetic temperature, vegetation indices, leaf area index, land cover, snow cover, sea ice extent, cloud mask, atmospheric profiles, aerosol properties, and many other geophysical parameters. <span class="hlt">MODIS</span> data are stored in HDF- EOS format in both swath format and in several different map projections. This tutorial guides users through data set characteristics as well as search and order interfaces, data unpacking, data subsetting, and potential applications of the data. A CD-ROM with sample data sets, and software tools for working with the data will be provided to the course participants.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007SPIE.6677E..0OX','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007SPIE.6677E..0OX"><span id="translatedtitle">Characterization of <span class="hlt">MODIS</span> solar diffuser on-orbit degradation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiong, X.; Xie, X.; Angal, A.; Choi, J.; Sun, J.; Barnes, W. L.</p> <p>2007-09-01</p> <p><span class="hlt">MODIS</span> has 20 <span class="hlt">reflective</span> solar bands (RSB) that are calibrated on-orbit using a solar diffuser (SD) and a solar diffuser stability monitor (SDSM). The <span class="hlt">MODIS</span> SD bi-directional <span class="hlt">reflectance</span> 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 <span class="hlt">reflected</span> 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 <span class="hlt">MODIS</span> has operated for more than seven years and <span class="hlt">Aqua</span> for over five years. The SD panel on each <span class="hlt">MODIS</span> instrument has experienced noticeable degradation with the largest changes observed in the VIS spectral region. This paper provides a brief description of <span class="hlt">MODIS</span> RSB calibration methodology and SD/SDSM operational activities, and illustrates the SD on-orbit degradation results for both Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span>. It also discusses the impact on the SD degradation due to sensor operational activities and SD solar exposure time. <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> 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 <span class="hlt">MODIS</span>, 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 <span class="hlt">MODIS</span> SD degradation rates were very similar to <span class="hlt">Aqua</span> <span class="hlt">MODIS</span>. Since then its SD has experienced much faster degradation rates due to more frequent solar exposure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120015385','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120015385"><span id="translatedtitle"><span class="hlt">MODIS</span> On-Orbit Calibration and Lessons Learned</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Xiong, Jack</p> <p>2012-01-01</p> <p>The Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) is a key instrument for NASA's Earth Observing System (EOS) Terra and <span class="hlt">Aqua</span> missions. Since launch, Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> have successfully operated for more than 12 and 10 years, respectively, and generated an unprecedented amount of data products for the science and user community over a wide range of applications. <span class="hlt">MODIS</span> was developed with improved design and stringent calibration requirements over its heritage sensors in order . to extend and enhance their long-term data records. Its follow-on instrument, the Visible/Infrared Imager Radiometer Suite (VIIRS), was launched on-board the Suomi National Polar-orbiting Partnership (NPP) spacecraft October 28, 2011. <span class="hlt">MODIS</span> collects data in 36 spectral bands, covering wavelengths from 0.41 to 14.S!Jlll, and at 250m, SOOm, and lkm spatial resolutions (nadir). <span class="hlt">MODIS</span> on-orbit calibration is provided by a set of onboard calibrators (OBC), including a solar diffuser (SO), a solar diffuser stability monitor (SDSM), a blackbody (BB), and a spectroradiometric calibration assembly (SRCA). In addition to the onboard calibrators, regular lunar observations are made by both Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> to track their calibration stability in the <span class="hlt">reflective</span> solar region. This tutorial session provides an overview of <span class="hlt">MODIS</span> on-orbit calibration and characterization methodologies. It discusses challenging issues and lessons learned from sensor design, operation, calibration, and inter-comparisons. Examples of instrument on-orbit performance are illustrated with a focus on the improvements made based on various lessons learned. It is expected that <span class="hlt">MODIS</span> experience and lessons will continue to provide valuable information for future earth observing missions/sensors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012SPIE.8528E..09X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012SPIE.8528E..09X"><span id="translatedtitle">Comparison of <span class="hlt">MODIS</span> and VIIRS solar diffuser stability monitor performance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiong, Xiaoxiong; Fulbright, Jon; Angal, Amit; Sun, Junqiang; Wang, Zhipeng</p> <p>2012-11-01</p> <p>Launched in December 1999 and May 2002, Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> have successfully operated for more than 12 and 10 years, respectively. <span class="hlt">MODIS</span> <span class="hlt">reflective</span> solar bands (RSB) are calibrated on-orbit by a solar diffuser (SD). Its on-orbit degradation, or the change in its bi-directional <span class="hlt">reflectance</span> factor (BRF), is tracked by a solar diffuser stability monitor (SDSM). The <span class="hlt">MODIS</span> SDSM makes alternate observations of direct sunlight through an attenuation screen (Sun view) and of sunlight <span class="hlt">reflected</span> diffusely off the SD (SD view) during each SDSM calibration event. The <span class="hlt">MODIS</span> SDSM has 9 detectors, covering wavelengths from 0.41 to 0.94 μm. Due to a design error in <span class="hlt">MODIS</span> SDSM sub-system (identified post-launch), relatively large ripples were noticed in its Sun view responses. As a result, an alternative approach was developed by the <span class="hlt">MODIS</span> calibration team to minimize the uncertainty in determining the SD on-orbit degradation. The first VIIRS, on-board the Suomi NPP spacecraft, was successfully launched in October 2011. It carries a <span class="hlt">MODIS</span>-like SD and SDSM system for its RSB on-orbit calibration. Its design was improved based on lessons learned from <span class="hlt">MODIS</span>. Operationally, the VIIRS SDSM is used more frequently than <span class="hlt">MODIS</span>. VIIRS SDSM collects data using 8 individual detectors, covering a similar wavelength range as <span class="hlt">MODIS</span>. This paper provides an overview of <span class="hlt">MODIS</span> and VIIRS SDSM design features, their on-orbit operations, and calibration strategies. It illustrates their on-orbit performance in terms of on-orbit changes in SDSM detector on-orbit responses and on-orbit degradations of their SD. Results show that on-orbit changes of both <span class="hlt">MODIS</span> and VIIRS SD BRF and SDSM response have similar wavelength dependency: the SD degradation is faster at shorter visible wavelengths while the decrease of SDSM detector responses (gains) is greater at longer near-infrared wavelengths.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110020728','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110020728"><span id="translatedtitle"><span class="hlt">MODIS</span> On-orbit Calibration Uncertainty Assessment</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chiang, Vincent; Sun, Junqiang; Wu, Aisheng</p> <p>2011-01-01</p> <p><span class="hlt">MODIS</span> has 20 <span class="hlt">reflective</span> solar bands (RSB) and 16 thermal emissive bands (TEB). Compared to its heritage sensors, <span class="hlt">MODIS</span> was developed with very stringent calibration uncertainty requirements. As a result, <span class="hlt">MODIS</span> was designed and built with a set of on-board calibrators (OBC), which allow key sensor performance parameters and on-orbit calibration coefficients to be monitored and updated. In terms of its calibration traceability, <span class="hlt">MODIS</span> RSB calibration is <span class="hlt">reflectance</span> based using an on-board solar diffuser (SD) and the TEB calibration is radiance based using an on-board blackbody (BB). In addition to on-orbit calibration coefficients derived from its OBC, calibration parameters determined from sensor pre-launch calibration and characterization are used in both the RSB and TEB calibration and retrieval algorithms. This paper provides a brief description of <span class="hlt">MODIS</span> calibration methodologies and an in-depth analysis of its on-orbit calibration uncertainties. Also discussed in this paper are uncertainty contributions from individual components and differences due to Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> instrument characteristics and on-orbit performance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014IJAEO..33..243P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014IJAEO..33..243P"><span id="translatedtitle">Automatic and improved radiometric correction of Landsat imagery using reference values from <span class="hlt">MODIS</span> surface <span class="hlt">reflectance</span> images</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pons, X.; Pesquer, L.; Cristóbal, J.; González-Guerrero, O.</p> <p>2014-12-01</p> <p>Radiometric correction is a prerequisite for generating high-quality scientific data, making it possible to discriminate between product artefacts and real changes in Earth processes as well as accurately produce land cover maps and detect changes. This work contributes to the automatic generation of surface <span class="hlt">reflectance</span> products for Landsat satellite series. Surface <span class="hlt">reflectances</span> are generated by a new approach developed from a previous simplified radiometric (atmospheric + topographic) correction model. The proposed model keeps the core of the old model (incidence angles and cast-shadows through a digital elevation model [DEM], Earth-Sun distance, etc.) and adds new characteristics to enhance and automatize ground <span class="hlt">reflectance</span> retrieval. The new model includes the following new features: (1) A fitting model based on reference values from pseudoinvariant areas that have been automatically extracted from existing <span class="hlt">reflectance</span> products (Terra <span class="hlt">MODIS</span> MOD09GA) that were selected also automatically by applying quality criteria that include a geostatistical pattern model. This guarantees the consistency of the internal and external series, making it unnecessary to provide extra atmospheric data for the acquisition date and time, dark objects or dense vegetation. (2) A spatial model for atmospheric optical depth that uses detailed DEM and MODTRAN simulations. (3) It is designed so that large time-series of images can be processed automatically to produce consistent Landsat surface <span class="hlt">reflectance</span> time-series. (4) The approach can handle most images, acquired now or in the past, regardless of the processing system, with the exception of those with extremely high cloud coverage. The new methodology has been successfully applied to a series of near 300 images of the same area including MSS, TM and ETM+ imagery as well as to different formats and processing systems (LPGS and NLAPS from the USGS; CEOS from ESA) for different degrees of cloud coverage (up to 60%) and SLC</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUSM.H34C..04P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUSM.H34C..04P"><span id="translatedtitle">Radiative Forcing of Dust in Mountain Snow from <span class="hlt">MODIS</span> surface <span class="hlt">reflectance</span> data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Painter, T. H.</p> <p>2009-05-01</p> <p>Here I present an algorithm that retrieves the radiative forcing by desert dust in mountain snow cover from surface <span class="hlt">reflectance</span> data from NASA Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>). Dust emitted from natural and disturbed lands frequently deposits to mountain snow cover through dry and wet deposition, particularly in spring when synoptic scale storms entrain material from recently dried surfaces. Dust decreases snow spectral albedo, primarily in the visible wavelengths where the imaginary parts of the complex refractive indices of dust and ice have the greatest contrast. This surface radiative forcing accelerates melt and contributes to the snow-albedo feedback. In the Rocky Mountains of Colorado, this has been shown to shorten the duration of snow cover by approximately a month. The algorithm presented here, <span class="hlt">MODIS</span> Dust Radiative Forcing in Snow (MOD-DRFS), determines the per pixel radiative forcing by dust in snow from a coupled radiative transfer model that infers the <span class="hlt">reflectance</span> difference between clean snow spectra and dust- laden snow spectra according to a grain size matching in the near infrared and shortwave infrared wavelengths that are not affected by dust absorption. The spectral residuals are splined to a high spectral resolution and convolved with the at surface spectral irradiance modulated by local topography, and subsequently integrated to the instantaneous surface radiative forcing. I demonstrate the model with retrievals in the Zagros Mountains, Iran and the San Juan Mountains, Colorado, USA. Preliminary validation of the model with in situ detailed pyranometer measurements in the San Juan Mountains indicates that the model has uncertainties of < 7 W/m2.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009EGUGA..1111496C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009EGUGA..1111496C&link_type=ABSTRACT"><span id="translatedtitle">Actual evapotranspiration estimation in a Mediterranean mountain region by means of Landsat-5 TM and TERRA/<span class="hlt">AQUA</span> <span class="hlt">MODIS</span> imagery and Sap Flow measurements in Pinus sylvestris forest stands.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cristóbal, J.; Poyatos, R.; Ninyerola, M.; Pons, X.; Llorens, P.</p> <p>2009-04-01</p> <p>Evapotranspiration monitoring has important implications on global and regional climate modelling, as well as in the knowledge of the hydrological cycle and in the assessment of environmental stress that affects forest and agricultural ecosystems. An increase of evapotranspiration while precipitation remains constant, or is reduced, could decrease water availability for natural and agricultural systems and human needs. Consequently, water balance methods, as the evapotranspiration modelling, have been widely used to estimate crop and forest water needs, as well as the global change effects. Nowadays, radiometric measurements provided by Remote Sensing and GIS analysis are the technologies used to compute evapotranspiration at regional scales in a feasible way. Currently, the 38% of Catalonia (NE of the Iberian Peninsula) is covered by forests, and one of the most important forest species is Scots Pine (Pinus sylvestris) which represents the 18.4% of the area occupied by forests. The aim of this work is to model actual evapotranspiration in Pinus sylvestris forest stands, in a Mediterranean mountain region, using remote sensing data, and compare it with stand-scale sap flow measurements measured in the Vallcebre research area (42° 12' N, 1° 49' E), in the Eastern Pyrenees. To perform this study a set of 30 cloud-free TERRA-<span class="hlt">MODIS</span> images and 10 Landsat-5 TM images of path 198 and rows 31 and 32 from June 2003 to January 2005 have been selected to perform evapotranspiration modelling in Pinus sylvestris forest stands. TERRA/<span class="hlt">AQUA</span> <span class="hlt">MODIS</span> images have been downloaded by means of the EOS Gateway. We have selected two different types of products which contain the remote sensing data we have used to model daily evapotranspiration, daily LST product and daily calibrated <span class="hlt">reflectances</span> product. Landsat-5 TM images have been corrected by means of conventional techniques based on first order polynomials taking into account the effect of land surface relief using a Digital</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A21F3096B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A21F3096B"><span id="translatedtitle">In-Depth Evaluation of <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> Collection 6 AOD Parameters Over the Contintinental U.S. Via Comparison to Both Ground-Truth and Modeled Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Belle, J. H.; Liu, Y.</p> <p>2014-12-01</p> <p>We evaluated all four <span class="hlt">MODIS</span> Collection 6 aerosol AOD parameters: 10 km Dark-Target, 3 km Dark-Target, 10 km Deep-Blue, and 10 km merged Dark-Target and Deep-Blue over the continental U.S. for the years 2011-2013 using AERONET observations. General results of this evaluation are illustrated in the attached figure, which includes data from 84 permanent AERONET sites and 64 DRAGON sites. There are indications of positive retrieval error in the AOD over the continental U.S. for Dark-Target and merged AOD parameters, such that slopes are greater than one, and the percentage of observations above the error envelope (EE, ±(0.05 + 0.15*AERONET AOD) is greater than the percentage below. In contrast, Deep-Blue has a large number of values within the error envelope. However, the correlation with ground observations is poor (r=0.73), the bias is relatively high (0.03) and the slope is below 1 (0.77). While coverage for Deep-Blue retrievals has been improved in Collection 6, the 10 km merged parameter, while partially dependent on Deep-Blue retrievals, performs poorly with regards to coverage, particularly for lower confidence values. For this parameter, an average of only 40.2% of pixels in a valid AERONET-<span class="hlt">MODIS</span> collocation has any retrieved values. This is in comparison to 72.9% of Deep-Blue pixels and 59.5% of Dark-Target pixels in the same 10 km product. Correlation coefficients between <span class="hlt">MODIS</span> and AERONET AOD over the Western U.S. are significantly lower (between 0.67 and 0.71) than those in the East, (between 0.84 and 0.93). However, Dark-Target and merged AOD parameters from the West do not show overall positive retrieval errors, and have regression slopes against AERONET observations between 0.98 and 1.02. <span class="hlt">MODIS</span> aerosol products are further combined with information from the <span class="hlt">MODIS</span> 16-day gridded NDVI (Normalized Difference Vegetation Index) product, Global Multi-resolution Terrain Elevation Data (GMTED2010), and the National Land Cover Database (NLCD) to elucidate ground</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110015244','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110015244"><span id="translatedtitle">Using Lunar Observations to Assess Terra <span class="hlt">MODIS</span> Thermal Emissive Bands Calibration</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Xiong, Xiaoxiong; Chen, Hongda</p> <p>2010-01-01</p> <p><span class="hlt">MODIS</span> collects data in both the <span class="hlt">reflected</span> solar and thermal emissive regions using 36 spectral bands. The center wavelengths of these bands cover the3.7 to 14.24 micron region. In addition to using its on-board calibrators (OBC), which include a full aperture solar diffuser (SD) and a blackbody (BB), lunar observations have been scheduled on a regular basis to support both Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> on-orbit calibration and characterization. This paper provides an overview of <span class="hlt">MODIS</span> lunar observations and their applications for the <span class="hlt">reflective</span> solar bands (RSB) and thermal emissive bands (TEB) with an emphasis on potential calibration improvements of <span class="hlt">MODIS</span> band 21 at 3.96 microns. This spectral band has detectors set with low gains to enable fire detection. Methodologies are proposed and examined on the use of lunar observations for the band 21 calibration. Also presented in this paper are preliminary results derived from Terra <span class="hlt">MODIS</span> lunar observations and remaining challenging issues.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3673426','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3673426"><span id="translatedtitle">Inter-Comparison of ASTER and <span class="hlt">MODIS</span> Surface <span class="hlt">Reflectance</span> and Vegetation Index Products for Synergistic Applications to Natural Resource Monitoring</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Miura, Tomoaki; Yoshioka, Hiroki; Fujiwara, Kayo; Yamamoto, Hirokazu</p> <p>2008-01-01</p> <p>Synergistic applications of multi-resolution satellite data have been of a great interest among user communities for the development of an improved and more effective operational monitoring system of natural resources, including vegetation and soil. In this study, we conducted an inter-comparison of two remote sensing products, namely, visible/near-infrared surface <span class="hlt">reflectances</span> and spectral vegetation indices (VIs), from the high resolution Advanced Thermal Emission and <span class="hlt">Reflection</span> Radiometer (ASTER) (15 m) and lower resolution Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) (250 m – 500 m) sensors onboard the Terra platform. Our analysis was aimed at understanding the degree of radiometric compatibility between the two sensors' products due to sensor spectral bandpasses and product generation algorithms. Multiple pairs of ASTER and <span class="hlt">MODIS</span> standard surface <span class="hlt">reflectance</span> products were obtained at randomly-selected, globally-distributed locations, from which two types of VIs were computed: the normalized difference vegetation index and the enhanced vegetation indices with and without a blue band. Our results showed that these surface <span class="hlt">reflectance</span> products and the derived VIs compared well between the two sensors at a global scale, but subject to systematic differences, of which magnitudes varied among scene pairs. An independent assessment of the accuracy of ASTER and <span class="hlt">MODIS</span> standard products, in which “in-house” surface <span class="hlt">reflectances</span> were obtained using in situ Aeronet atmospheric data for comparison, suggested that the performance of the ASTER atmospheric correction algorithm may be variable, reducing overall quality of its standard <span class="hlt">reflectance</span> product. Atmospheric aerosols, which were not corrected for in the ASTER algorithm, were found not to impact the quality of the derived <span class="hlt">reflectances</span>. Further investigation is needed to identify the sources of inconsistent atmospheric correction results associated with the ASTER algorithm, including additional quality</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120010372','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120010372"><span id="translatedtitle">Evaluation of Detector-to-Detector and Mirror Side Differences for Terra <span class="hlt">MODIS</span> <span class="hlt">Reflective</span> Solar Bands Using Simultaneous MISR Observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wu, Aisheng; Xiong, Xiaoxiong; Angal, A.; Barnes, W.</p> <p>2011-01-01</p> <p>The Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) is one of the five Earth-observing instruments on-board the National Aeronautics and Space Administration (NASA) Earth-Observing System(EOS) Terra spacecraft, launched in December 1999. It has 36 spectral bands with wavelengths ranging from 0.41 to 14.4 mm and collects data at three nadir spatial resolutions: 0.25 km for 2 bands with 40 detectors each, 0.5 km for 5 bands with 20 detectors each and 1 km for the remaining 29 bands with 10 detectors each. <span class="hlt">MODIS</span> bands are located on four separate focal plane assemblies (FPAs) according to their spectral wavelengths and aligned in the cross-track direction. Detectors of each spectral band are aligned in the along-track direction. <span class="hlt">MODIS</span> makes observations using a two-sided paddle-wheel scan mirror. Its on-board calibrators (OBCs) for the <span class="hlt">reflective</span> solar bands (RSBs) include a solar diffuser (SD), a solar diffuser stability monitor (SDSM) and a spectral-radiometric calibration assembly (SRCA). Calibration is performed for each band, detector, sub-sample (for sub-kilometer resolution bands) and mirror side. In this study, a ratio approach is applied to <span class="hlt">MODIS</span> observed Earth scene <span class="hlt">reflectances</span> to track the detector-to-detector and mirror side differences. Simultaneous observed <span class="hlt">reflectances</span> from the Multi-angle Imaging Spectroradiometer (MISR), also onboard the Terra spacecraft, are used with <span class="hlt">MODIS</span> observed <span class="hlt">reflectances</span> in this ratio approach for four closely matched spectral bands. Results show that the detector-to-detector difference between two adjacent detectors within each spectral band is typically less than 0.2% and, depending on the wavelengths, the maximum difference among all detectors varies from 0.5% to 0.8%. The mirror side differences are found to be very small for all bands except for band 3 at 0.44 mm. This is the band with the shortest wavelength among the selected matching bands, showing a time-dependent increase for the mirror side difference. This</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AMT.....8.5237J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AMT.....8.5237J"><span id="translatedtitle">Adaption of the <span class="hlt">MODIS</span> aerosol retrieval algorithm using airborne spectral surface <span class="hlt">reflectance</span> measurements over urban areas: a case study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jäkel, E.; Mey, B.; Levy, R.; Gu, X.; Yu, T.; Li, Z.; Althausen, D.; Heese, B.; Wendisch, M.</p> <p>2015-12-01</p> <p><span class="hlt">MODIS</span> (MOderate-resolution Imaging Spectroradiometer) retrievals of aerosol optical depth (AOD) are biased over urban areas, primarily because the <span class="hlt">reflectance</span> characteristics of urban surfaces are different than that assumed by the retrieval algorithm. Specifically, the operational "dark-target" retrieval is tuned towards vegetated (dark) surfaces and assumes a spectral relationship to estimate the surface <span class="hlt">reflectance</span> in blue and red wavelengths. From airborne measurements of surface <span class="hlt">reflectance</span> over the city of Zhongshan, China, were collected that could replace the assumptions within the <span class="hlt">MODIS</span> retrieval algorithm. The subsequent impact was tested upon two versions of the operational algorithm, Collections 5 and 6 (C5 and C6). AOD retrieval results of the operational and modified algorithms were compared for a specific case study over Zhongshan to show minor differences between them all. However, the Zhongshan-based spectral surface relationship was applied to a much larger urban sample, specifically to the <span class="hlt">MODIS</span> data taken over Beijing between 2010 and 2014. These results were compared directly to ground-based AERONET (AErosol RObotic NETwork) measurements of AOD. A significant reduction of the differences between the AOD retrieved by the modified algorithms and AERONET was found, whereby the mean difference decreased from 0.27±0.14 for the operational C5 and 0.19±0.12 for the operational C6 to 0.10±0.15 and -0.02±0.17 by using the modified C5 and C6 retrievals. Since the modified algorithms assume a higher contribution by the surface to the total measured <span class="hlt">reflectance</span> from <span class="hlt">MODIS</span>, consequently the overestimation of AOD by the operational methods is reduced. Furthermore, the sensitivity of the <span class="hlt">MODIS</span> AOD retrieval with respect to different surface types was investigated. Radiative transfer simulations were performed to model <span class="hlt">reflectances</span> at top of atmosphere for predefined aerosol properties. The <span class="hlt">reflectance</span> data were used as input for the retrieval methods. It</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160006614','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160006614"><span id="translatedtitle">Consistency of CERES Radiances and Fluxes from <span class="hlt">Aqua</span> and Suomi-NPP</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Liang, Lusheng; Miller, Walter; Su, Wenying; Loeb, Norman</p> <p>2015-01-01</p> <p>The Clouds and Earth's Radiant Energy System (CERES) instruments on board Terra, <span class="hlt">Aqua</span>, and Suomi-NPP have been providing data products critical to advancing our understanding of the effects of clouds and aerosols on radiative energy within the Earth-atmosphere system. The CERES instrument consists of a threechannel broadband scanning radiometer. The scanning radiometer measures radiances in shortwave (SW, 0.3-5 micron), window (WN, 8-12 micron), and total (0.3-200 micron) channels. The longwave (LW) component is derived as the difference between total and SW channels. These measured radiances at a given sun-Earthsatellite geometry are converted to outgoing <span class="hlt">reflected</span> solar and emitted thermal TOA radiative fluxes by using CERES scene-type dependent angular distribution models (ADMs). The CERES instruments must remain radiometrically stable and correctly inter-calibrated to accurately capture changes in Earth"s radiation budget from interannual to decadal timescales. This presentation will focus on comparisons between collocated radiance measurements from CERES instruments on <span class="hlt">Aqua</span> and on Suomi-NPP. As we do not have a set of ADMs that is constructed specifically for the CERES instrument on Suomi-NPP, CERES <span class="hlt">Aqua</span> ADMs are used to invert fluxes from radiance measurements on Suomi-NPP. But the CERES <span class="hlt">Aqua</span> footprint size is smaller than the CERES Suomi-NPP footprint size and the scene identifications provided by <span class="hlt">MODIS</span> and VIIRS can also be different from each other. Will using <span class="hlt">Aqua</span> ADMs for Suomi-NPP flux inversion increase the flux uncertainty? We will examine the deseasonalized flux anomaly time series using <span class="hlt">Aqua</span> data alone and using combined <span class="hlt">Aqua</span> and Suomi-NPP data. We will also present a simulation study to assess the Suomi-NPP flux uncertainty from using <span class="hlt">Aqua</span> ADMs for the flux inversion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AMT.....7.4353L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AMT.....7.4353L"><span id="translatedtitle">Scientific impact of <span class="hlt">MODIS</span> C5 calibration degradation and C6+ improvements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lyapustin, A.; Wang, Y.; Xiong, X.; Meister, G.; Platnick, S.; Levy, R.; Franz, B.; Korkin, S.; Hilker, T.; Tucker, J.; Hall, F.; Sellers, P.; Wu, A.; Angal, A.</p> <p>2014-12-01</p> <p>The Collection 6 (C6) <span class="hlt">MODIS</span> (Moderate Resolution Imaging Spectroradiometer) land and atmosphere data sets are scheduled for release in 2014. C6 contains significant revisions of the calibration approach to account for sensor aging. This analysis documents the presence of systematic temporal trends in the visible and near-infrared (500 m) bands of the Collection 5 (C5) <span class="hlt">MODIS</span> Terra and, to lesser extent, in <span class="hlt">MODIS</span> <span class="hlt">Aqua</span> geophysical data sets. Sensor degradation is largest in the blue band (B3) of the <span class="hlt">MODIS</span> sensor on Terra and decreases with wavelength. Calibration degradation causes negative global trends in multiple <span class="hlt">MODIS</span> C5 products including the dark target algorithm's aerosol optical depth over land and Ångström exponent over the ocean, global liquid water and ice cloud optical thickness, as well as surface <span class="hlt">reflectance</span> and vegetation indices, including the normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI). As the C5 production will be maintained for another year in parallel with C6, one objective of this paper is to raise awareness of the calibration-related trends for the broad <span class="hlt">MODIS</span> user community. The new C6 calibration approach removes major calibrations trends in the Level 1B (L1B) data. This paper also introduces an enhanced C6+ calibration of the <span class="hlt">MODIS</span> data set which includes an additional polarization correction (PC) to compensate for the increased polarization sensitivity of <span class="hlt">MODIS</span> Terra since about 2007, as well as detrending and Terra-<span class="hlt">Aqua</span> cross-calibration over quasi-stable desert calibration sites. The PC algorithm, developed by the <span class="hlt">MODIS</span> ocean biology processing group (OBPG), removes residual scan angle, mirror side and seasonal biases from aerosol and surface <span class="hlt">reflectance</span> (SR) records along with spectral distortions of SR. Using the multiangle implementation of atmospheric correction (MAIAC) algorithm over deserts, we have also developed a detrending and cross-calibration method which removes residual decadal trends on</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20160005757&hterms=scientific&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dscientific','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20160005757&hterms=scientific&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dscientific"><span id="translatedtitle">Scientific Impact of <span class="hlt">MODIS</span> C5 Calibration Degradation and C6+ Improvements</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lyapustin, A.; Wang, Y.; Xiong, X.; Meister, G.; Platnick, S.; Levy, R.; Franz, B.; Korkin, S.; Hilker, T.; Tucker, J.; Hall, F.; Sellers, P.; Wu, A.; Angal, A.</p> <p>2014-01-01</p> <p>The Collection 6 (C6) <span class="hlt">MODIS</span> (Moderate Resolution Imaging Spectroradiometer) land and atmosphere data sets are scheduled for release in 2014. C6 contains significant revisions of the calibration approach to account for sensor aging. This analysis documents the presence of systematic temporal trends in the visible and near-infrared (500 m) bands of the Collection 5 (C5) <span class="hlt">MODIS</span> Terra and, to lesser extent, in <span class="hlt">MODIS</span> <span class="hlt">Aqua</span> geophysical data sets. Sensor degradation is largest in the blue band (B3) of the <span class="hlt">MODIS</span> sensor on Terra and decreases with wavelength. Calibration degradation causes negative global trends in multiple <span class="hlt">MODIS</span> C5 products including the dark target algorithm's aerosol optical depth over land and Ångstrom exponent over the ocean, global liquid water and ice cloud optical thickness, as well as surface <span class="hlt">reflectance</span> and vegetation indices, including the normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI). As the C5 production will be maintained for another year in parallel with C6, one objective of this paper is to raise awareness of the calibration-related trends for the broad <span class="hlt">MODIS</span> user community. The new C6 calibration approach removes major calibrations trends in the Level 1B (L1B) data. This paper also introduces an enhanced C6C calibration of the <span class="hlt">MODIS</span> data set which includes an additional polarization correction (PC) to compensate for the increased polarization sensitivity of <span class="hlt">MODIS</span> Terra since about 2007, as well as detrending and Terra- <span class="hlt">Aqua</span> cross-calibration over quasi-stable desert calibration sites. The PC algorithm, developed by the <span class="hlt">MODIS</span> ocean biology processing group (OBPG), removes residual scan angle, mirror side and seasonal biases from aerosol and surface <span class="hlt">reflectance</span> (SR) records along with spectral distortions of SR. Using the multiangle implementation of atmospheric correction (MAIAC) algorithm over deserts, we have also developed a detrending and cross-calibration method which removes residual decadal trends on</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AMTD....7.7281L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AMTD....7.7281L"><span id="translatedtitle">Science impact of <span class="hlt">MODIS</span> C5 calibration degradation and C6+ improvements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lyapustin, A.; Wang, Y.; Xiong, X.; Meister, G.; Platnick, S.; Levy, R.; Franz, B.; Korkin, S.; Hilker, T.; Tucker, J.; Hall, F.; Sellers, P.; Wu, A.; Angal, A.</p> <p>2014-07-01</p> <p>The Collection 6 (C6) <span class="hlt">MODIS</span> land and atmosphere datasets are scheduled for release in 2014. C6 contains significant revisions of the calibration approach to account for sensor aging. This analysis documents the presence of systematic temporal trends in the visible and near-infrared (500 m) bands of the Collection 5 (C5) <span class="hlt">MODIS</span> Terra, and to lesser extent, in <span class="hlt">MODIS</span> <span class="hlt">Aqua</span> geophysical datasets. Sensor degradation is largest in the Blue band (B3) of the <span class="hlt">MODIS</span> sensor on Terra and decreases with wavelength. Calibration degradation causes negative global trends in multiple <span class="hlt">MODIS</span> C5 products including the dark target algorithm's aerosol optical depth over land and Ångström Exponent over the ocean, global liquid water and ice cloud optical thickness, as well as surface <span class="hlt">reflectance</span> and vegetation indices, including the normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI). As the C5 production will be maintained for another year in parallel with C6, one objective of this paper is to raise awareness of the calibration-related trends for the broad <span class="hlt">MODIS</span> user community. The new C6 calibration approach removes major calibrations trends in the Level 1B (L1B) data. This paper also introduces an enhanced C6+ calibration of the <span class="hlt">MODIS</span> dataset which includes an additional polarization correction (PC) to compensate for the increased polarization sensitivity of <span class="hlt">MODIS</span> Terra since about 2007, as well as de-trending and Terra-<span class="hlt">Aqua</span> cross-calibration over quasi-stable desert calibration sites. The PC algorithm, developed by the <span class="hlt">MODIS</span> ocean biology processing group (OBPG), removes residual scan angle, mirror side and seasonal biases from aerosol and surface <span class="hlt">reflectance</span> (SR) records along with spectral distortions of SR. Using the Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm over deserts, we have also developed a de-trending and cross-calibration method which removes residual decadal trends on the order of several tenths of one percent of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110015444','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110015444"><span id="translatedtitle">Impact of Sensor Degradation on the <span class="hlt">MODIS</span> NDVI Time Series</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wang, Dongdong; Morton, Douglas; Masek, Jeffrey; Wu, Aisheng; Nagol, Jyoteshwar; Xiong, Xiaoxiong; Levy, Robert; Vermote, Eric; Wolfe, Robert</p> <p>2011-01-01</p> <p>Time series of satellite data provide unparalleled information on the response of vegetation to climate variability. Detecting subtle changes in vegetation over time requires consistent satellite-based measurements. Here, we evaluated the impact of sensor degradation on trend detection using Collection 5 data from the Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) sensors on the Terra and <span class="hlt">Aqua</span> platforms. For Terra <span class="hlt">MODIS</span>, the impact of blue band (Band 3, 470nm) degradation on simulated surface <span class="hlt">reflectance</span> was most pronounced at near-nadir view angles, leading to a 0.001-0.004/yr decline in Normalized Difference Vegetation Index (NDVI) under a range of simulated aerosol conditions and surface types. Observed trends <span class="hlt">MODIS</span> NDVI over North America were consistent with simulated results, with nearly a threefold difference in negative NDVI trends derived from Terra (17.4%) and <span class="hlt">Aqua</span> (6.7%) <span class="hlt">MODIS</span> sensors during 2002-2010. Planned adjustments to Terra <span class="hlt">MODIS</span> calibration for Collection 6 data reprocessing will largely eliminate this negative bias in NDVI trends over vegetation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140009143','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140009143"><span id="translatedtitle">Impact of Sensor Degradation on the <span class="hlt">MODIS</span> NDVI Time Series</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wang, Dongdong; Morton, Douglas Christopher; Masek, Jeffrey; Wu, Aisheng; Nagol, Jyoteshwar; Xiong, Xiaoxiong; Levy, Robert; Vermote, Eric; Wolfe, Robert</p> <p>2012-01-01</p> <p>Time series of satellite data provide unparalleled information on the response of vegetation to climate variability. Detecting subtle changes in vegetation over time requires consistent satellite-based measurements. Here, the impact of sensor degradation on trend detection was evaluated using Collection 5 data from the Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) sensors on the Terra and <span class="hlt">Aqua</span> platforms. For Terra <span class="hlt">MODIS</span>, the impact of blue band (Band 3, 470 nm) degradation on simulated surface <span class="hlt">reflectance</span> was most pronounced at near-nadir view angles, leading to a 0.001-0.004 yr-1 decline in Normalized Difference Vegetation Index (NDVI) under a range of simulated aerosol conditions and surface types. Observed trends in <span class="hlt">MODIS</span> NDVI over North America were consistentwith simulated results,with nearly a threefold difference in negative NDVI trends derived from Terra (17.4%) and <span class="hlt">Aqua</span> (6.7%) <span class="hlt">MODIS</span> sensors during 2002-2010. Planned adjustments to Terra <span class="hlt">MODIS</span> calibration for Collection 6 data reprocessing will largely eliminate this negative bias in detection of NDVI trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120010660','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120010660"><span id="translatedtitle">Critical <span class="hlt">Reflectance</span> Derived from <span class="hlt">MODIS</span>: Application for the Retrieval of Aerosol Absorption over Desert Regions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wells, Kelley C.; Martins, J. Vanderlei; Remer, Lorraine A.; Kreidenweis, Sonia M.; Stephens, Graeme L.</p> <p>2012-01-01</p> <p>Aerosols are tiny suspended particles in the atmosphere that scatter and absorb sunlight. Smoke particles are aerosols, as are sea salt, particulate pollution and airborne dust. When you look down at the earth from space sometimes you can see vast palls of whitish smoke or brownish dust being transported by winds. The reason that you can see these aerosols is because they are <span class="hlt">reflecting</span> incoming sunlight back to the view in space. The reason for the difference in color between the different types of aerosol is that the particles arc also absorbing sunlight at different wavelengths. Dust appears brownish or reddish because it absorbs light in the blue wavelengths and scatters more reddish light to space, Knowing how much light is scattered versus how much is absorbed, and knowin that as a function of wavelength is essential to being able to quantify the role aerosols play in the energy balance of the earth and in climate change. It is not easy measuring the absorption properties of aerosols when they are suspended in the atmosphere. People have been doing this one substance at a time in the laboratory, but substances mix when they are in the atmosphere and the net absorption effect of all the particles in a column of air is a goal of remote sensing that has not yet been completely successful. In this paper we use a technique based on observing the point at which aerosols change from brightening the surface beneath to darkening it. If aerosols brighten a surface. they must scatter more light to space. If they darken the surface. they must be absorbing more. That cross over point is called the critical <span class="hlt">reflectance</span> and in this paper we show that critical <span class="hlt">reflectance</span> is a monotonic function of the intrinsic absorption properties of the particles. This parameter we call the single scattering albedo. We apply the technique to <span class="hlt">MODIS</span> imagery over the Sahara and Sahel regions to retrieve the single scattering albedo in seven wavelengths, compare these retrievals to ground</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23038327','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23038327"><span id="translatedtitle">Validation of <span class="hlt">MODIS</span>-derived bidirectional <span class="hlt">reflectivity</span> retrieval algorithm in mid-infrared channel with field measurements.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tang, Bo-Hui; Wu, Hua-; Li, Zhao-Liang; Nerry, Françoise</p> <p>2012-07-30</p> <p>This work addressed the validation of the <span class="hlt">MODIS</span>-derived bidirectional <span class="hlt">reflectivity</span> retrieval algorithm in mid-infrared (MIR) channel, proposed by Tang and Li [Int. J. Remote Sens. 29, 4907 (2008)], with ground-measured data, which were collected from a field campaign that took place in June 2004 at the ONERA (Office National d'Etudes et de Recherches Aérospatiales) center of Fauga-Mauzac, on the PIRRENE (Programme Interdisciplinaire de Recherche sur la Radiométrie en Environnement Extérieur) experiment site [Opt. Express 15, 12464 (2007)]. The leaving-surface spectral radiances measured by a BOMEM (MR250 Series) Fourier transform interferometer were used to calculate the ground brightness temperatures with the combination of the inversion of the Planck function and the spectral response functions of <span class="hlt">MODIS</span> channels 22 and 23, and then to estimate the ground brightness temperature without the contribution of the solar direct beam and the bidirectional <span class="hlt">reflectivity</span> by using Tang and Li's proposed algorithm. On the other hand, the simultaneously measured atmospheric profiles were used to obtain the atmospheric parameters and then to calculate the ground brightness temperature without the contribution of the solar direct beam, based on the atmospheric radiative transfer equation in the MIR region. Comparison of those two kinds of brightness temperature obtained by two different methods indicated that the Root Mean Square Error (RMSE) between the brightness temperatures estimated respectively using Tang and Li's algorithm and the atmospheric radiative transfer equation is 1.94 K. In addition, comparison of the hemispherical-directional <span class="hlt">reflectances</span> derived by Tang and Li's algorithm with those obtained from the field measurements showed that the RMSE is 0.011, which indicates that Tang and Li's algorithm is feasible to retrieve the bidirectional <span class="hlt">reflectivity</span> in MIR channel from <span class="hlt">MODIS</span> data. PMID:23038327</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20020006092&hterms=Franco&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D70%26Ntt%3DFranco','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20020006092&hterms=Franco&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D70%26Ntt%3DFranco"><span id="translatedtitle">The <span class="hlt">Aqua</span>-Aura Train</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schoeberl, Mark; Einaudi, Franco (Technical Monitor)</p> <p>2001-01-01</p> <p>This talk will focus on the afternoon constellation of EOS platforms and the scientific benefits that arise from this formation. The afternoon EOS constellation or the "A-train" will provide unprecedented information on clouds and aerosols. At 1:30 PM crossing time EOS-<span class="hlt">Aqua</span> begins the train with the <span class="hlt">MODIS</span>, CERES and AIRS instruments making aerosol, cloud, radiation budget , temperature and water vapor measurements. AMSR-E will also make total column water measurements. Following <span class="hlt">Aqua</span> by one minute, Cloudsat will make active radar precipitation measurements as and PICASSOCENA will make lidar measurements of clouds and aerosols. Fourteen minutes later, EOS-Aura will pass through the same space making upper troposphere water vapor and ice profiles as well as some key trace gases associated with convective processes (MLS and HIRDLS). Additional measurements of aerosols will be made by Aura's OMI instrument.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040171530&hterms=Measuring+instruments&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DMeasuring%2Binstruments','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040171530&hterms=Measuring+instruments&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DMeasuring%2Binstruments"><span id="translatedtitle">Polarization Ray Trace Model of the <span class="hlt">MODIS</span> Instrument</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Waluschka, Eugene; Xiong, Jack; Esaias, Wayne E.; Voss, Kenneth; Souaidia, Nordine; Pellicori, Samuel; Moyer, David; Guenther, Bruce; Barnes, William</p> <p>2004-01-01</p> <p>Sunlight <span class="hlt">reflected</span> from the earth is, to a certain extent, polarized. Radiometers, such as the <span class="hlt">MODIS</span> instrument on board the TERRA and <span class="hlt">AQUA</span> spacecraft, are to a certain extent polarizers. Accurate radiometric measurements must take into account both the polarization state of the scene and the polarization sensitivity of the measuring instrument. The measured polarization characteristics of the <span class="hlt">MODIS</span> instruments are contained in various radiometric models. Continued use of these radiometric math models, over a number of years, have shown where these models can be improved. Currently a <span class="hlt">MODIS</span> polarization ray trace model has been created which models the thin film structure on the optical elements. This approach is described and modeled and measured instrument polarization sensitivity results presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRD..121.6273Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRD..121.6273Z"><span id="translatedtitle">Intercalibration of CERES, <span class="hlt">MODIS</span>, and MISR <span class="hlt">reflected</span> solar radiation and its application to albedo trends</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhan, Yizhe; Davies, Roger</p> <p>2016-06-01</p> <p>Measurements on the Terra satellite by the Cloud and the Earth's Radiant Energy System (CERES), the Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>), and the Multiangle Imaging Spectroradiometer (MISR), between 2001 and 2015 over the polar regions, are analyzed in order to investigate the intercalibration differences between these instruments. Direct comparisons of colocated near-nadir radiances from CERES, <span class="hlt">MODIS</span>, and MISR show relative agreement within 2.4% decade-1. By comparison with the CERES shortwave broadband, <span class="hlt">MODIS</span> Collection 6 is getting brighter, by 1.0 ± 0.7% decade-1 in the red band and 1.4 ± 0.7% decade-1 in the near infrared. MISR's red and near-infrared bands, however, show darkening trends of -1.0 ± 0.6% decade-1 and -1.1 ± 0.6% decade-1, respectively. The CERES/<span class="hlt">MODIS</span> or CERES/MISR visible and near IR radiance ratio is shown to have a significant negative correlation with precipitable water content over the Antarctic Plateau. The intercalibration results successfully correct the differential top-of-atmosphere trends in zonal albedos between CERES and MISR.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020083259','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020083259"><span id="translatedtitle">Relationship Between Surface <span class="hlt">Reflectance</span> in the Visible and Mid-IR used in <span class="hlt">MODIS</span> Aerosol Algorithm-Theory</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kaufman, Yoram J.; Gobron, Nadine; Pinty, Bernard; Widlowski, Jean-Luc; Verstraete, Michel M.; Lau, William K. M. (Technical Monitor)</p> <p>2002-01-01</p> <p>Data from the Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) instrument that flies in polar orbit on the Terra platform, are used to derive the aerosol optical thickness and properties over land and ocean. The relationships between visible <span class="hlt">reflectance</span> (at blue, rho(sub blue), and red, rho(sub red)) and mid-infrared (at 2.1 microns, rho(sub 2.1)) are used in the <span class="hlt">MODIS</span> aerosol retrieval algorithm to derive global distribution of aerosols over the land. These relations have been established from a series of measurements indicating that rho(sub blue) is approximately 0.5 rho(sub red) is approximately 0.25 rho(sub 2.1). Here we use a model to describe the transfer of radiation through a vegetation canopy composed of randomly oriented leaves to assess the theoretical foundations for these relationships. Calculations for a wide range of leaf area indices and vegetation fractions show that rho(sub blue) is consistently about 1/4 of rho(sub 2.1) as used by <span class="hlt">MODIS</span> for the whole range of analyzed cases, except for very dark soils, such as those found in burn scars. For its part, the ratio rho(sub red)/rho(sub 2.1) varies from less than the empirically derived value of 1/2 for dense and dark vegetation, to more than 1/2 for bright mixture of soil and vegetation. This is in agreement with measurements over uniform dense vegetation, but not with measurements over mixed dark scenes. In the later case the discrepancy is probably mitigated by shadows due to uneven canopy and terrain on a large scale. It is concluded that the value of this ratio should ideally be made dependent on the land cover type in the operational processing of <span class="hlt">MODIS</span> data, especially over dense forests.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012SPIE.8510E..0HX','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012SPIE.8510E..0HX"><span id="translatedtitle">On-orbit performance of <span class="hlt">MODIS</span> solar diffuser stability monitor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiong, Xiaoxiong (Jack); Angal, Amit; Choi, Taeyoung; Sun, Junqiang; Johnson, Eric</p> <p>2012-09-01</p> <p><span class="hlt">MODIS</span> <span class="hlt">reflective</span> solar bands (RSB) calibration is provided by an on-board solar diffuser (SD). On-orbit changes in the SD bi-directional <span class="hlt">reflectance</span> factor (BRF) are tracked by a solar diffuser stability monitor (SDSM). The SDSM consists of a solar integration sphere (SIS) with nine detectors covering wavelengths from 0.41 to 0.94 μm. It functions as a ratioing radiometer, making alternate observations of the sunlight through a fixed attenuation screen and the sunlight diffusely <span class="hlt">reflected</span> from the SD during each scheduled SD/SDSM calibration event. Since launch, Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> SD/SDSM systems have been operated regularly to support the RSB on-orbit calibration. This paper provides an overview of <span class="hlt">MODIS</span> SDSM design functions, its operation and calibration strategies, and on-orbit performance. Changes in SDSM detector responses over time and their potential impact on tracking SD on-orbit degradation are examined. Also presented in this paper are lessons learned from <span class="hlt">MODIS</span> SD/SDSM calibration system and improvements made to the VIIRS SD/SDSM system, including preliminary comparisons of <span class="hlt">MODIS</span> and VIIRS SDSM on-orbit performance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20160005180&hterms=orbit&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dorbit','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20160005180&hterms=orbit&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dorbit"><span id="translatedtitle">On-Orbit Performance of <span class="hlt">MODIS</span> Solar Diffuser Stability Monitor</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Xiong, Xiaoxiong; Angal, Amit; Choi, Taeyoung; Sun, Jungiang; Johnson, Eric</p> <p>2014-01-01</p> <p><span class="hlt">MODIS</span> <span class="hlt">reflective</span> solar bands (RSB) calibration is provided by an on-board solar diffuser (SD). On-orbit changes in the SD bi-directional <span class="hlt">reflectance</span> factor (BRF) are tracked by a solar diffuser stability monitor (SDSM). The SDSM consists of a solar integration sphere (SIS) with nine detectors covering wavelengths from 0.41 to 0.94 microns. It functions as a ratioing radiometer, making alternate observations of the sunlight through a fixed attenuation screen and the sunlight diffusely <span class="hlt">reflected</span> from the SD during each scheduled SD/SDSM calibration event. Since launch, Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> SD/SDSM systems have been operated regularly to support the RSB on-orbit calibration. This paper provides an overview of <span class="hlt">MODIS</span> SDSM design functions, its operation and calibration strategies, and on-orbit performance. Changes in SDSM detector responses over time and their potential impact on tracking SD on-orbit degradation are examined. Also presented in this paper are lessons learned from <span class="hlt">MODIS</span> SD/SDSM calibration system and improvements made to the VIIRS SD/SDSM system, including preliminary comparisons of <span class="hlt">MODIS</span> and VIIRS SDSM on-orbit performance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100020136','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100020136"><span id="translatedtitle">Remote Sensing of the Absorption Coefficients and Chlorophyll a Concentration in the U.S. Southern Middle Atlantic Bight from SeaWiFS and <span class="hlt">MODIS-Aqua</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pan, Xiaoju; Mannino, Antonio; Russ, Mary E.; Hooker, Stanford B.</p> <p>2008-01-01</p> <p>At present, satellite remote sensing of coastal water quality and constituent concentration is subject to large errors as compared to the capability of satellite sensors in oceanic waters. In this study, field measurements collected on a series of cruises within U.S. southern Middle Atlantic Bight (SMAB) were applied to improve retrievals of satellite ocean color products in order to examine the factors that regulate the bio-optical properties within the continental shelf waters of the SMAB. The first objective was to develop improvements in satellite retrievals of absorption coefficients of phytoplankton (a(sub ph)), colored dissolved organic matter (CDOM) (a(sub g)), non-pigmented particles (a(sub d)), and non-pigmented particles plus CDOM (a(sub dg)), and chlorophyll a concentration ([Chl_a]). Several algorithms were compared to derive constituent absorption coefficients from remote sensing <span class="hlt">reflectance</span> (R(sub rs)) ratios. The validation match-ups showed that the mean absolute percent differences (MAPD) were typically less than 35%, although higher errors were found for a(sub d) retrievals. Seasonal and spatial variability of satellite-derived absorption coefficients and [Chl_a] was apparent and consistent with field data. CDOM is a major contributor to the bio-optical properties of the SMAB, accounting for 35-70% of total light absorption by particles plus CDOM at 443 nm, as compared to 30-45% for phytoplankton and 0-20% for non-pigmented particles. The overestimation of [Chl_a] from the operational satellite algorithms may be attributed to the strong CDOM absorption in this region. River discharge is important in controlling the bio-optical environment, but cannot explain all of the regional and seasonal variability of biogeochemical constituents in the SMAB.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1713537G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1713537G"><span id="translatedtitle">Intercomparison of <span class="hlt">MODIS-Aqua</span> C051 and C006 Level 3 Deep Blue AOD and Ångström exponent retrievals over the Sahara desert and the Arabian Peninsula during the period 2002-2014</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gkikas, Antonis; Basart, Sara; Korras-Carraca, Marios; Papadimas, Christos; Hatzianastassiou, Nikos; Sayer, Andrew; Hsu, Christina; Baldasano, Jose Maria</p> <p>2015-04-01</p> <p>Dust loads emitted from the arid regions of Northern Africa and the Arabian Peninsula account for the major portion of the global dust aerosol burden. Depending on prevailing atmospheric circulation they can be transported far away from their source areas. Considering the key role of dust aerosols to weather and climate a better description of their spatial and temporal variability it is an issue of great importance. The main target of the present study is to describe aerosols' regime over Northern Africa and Arabian Peninsula using Deep Blue aerosol optical depth (AOD550nm) and Ångström exponent (α412-470nm) measurements. Given the applied changes to the retrieval algorithm, emphasis is also given to the inter-comparison between the data from Collections 051 and 006. The analysis is performed using <span class="hlt">MODIS-Aqua</span> daily Level 3 data at 1°x1° spatial resolution over the period 2002-2014. The study region extends from 20°W to 60°E and from 0° to 40°N. The obtained long-term geographical distributions reveal many similarities between C051 and C006 AOD retrievals. They both indicate a zone of high AODs along the parallel of 15°N, extending from the western coasts of Africa to Chad where the maximum values (~1.3) are recorded. In the Arabian Peninsula, the maximum AODs (up to 0.6) are found in Iraq. On the contrary, more apparent differences between the two collections are found for α412-470nm. It is evident a reduction of C006 retrievals, which is more pronounced across the Sahara desert. In C006, the α412-470nm values over the deserts of Northern Africa and Middle East mostly vary from 0 to 0.6 while higher values (up to 1.5) are observed in sub-sahel regions, west coasts of Saudi Arabia and Iran. During the study period, in both collections, AOD has decreased by up to 93% in N. Africa (northern parts of Algeria) while it has increased by up to 70% in the Middle East (northern parts of Iraq). Reversed tendencies are found for the α412-470nm retrievals. For</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150023337','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150023337"><span id="translatedtitle"><span class="hlt">MODIS</span> and VIIRS Lunar Observations and Applications</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Xiong, Xiaoxiong; Wang, Zhipeng; Sun, Junqiang; Angal, Amit Avinash; Fulbright, Jon; Butler, James</p> <p>2013-01-01</p> <p>Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> have successfully operated for more than 13 and 11 years since their launch in 1999 and 2002, respectively. The VIIRS instrument on-board the S-NPP launched in 2011 has also operated for nearly 2 years. Both <span class="hlt">MODIS</span> and VIIRS make observations in the <span class="hlt">reflective</span> solar and thermal emissive regions and their on-orbit calibration and characterization are provided by a set of on-board calibrators (OBC). In addition, lunar observations have been made on a regular basis to support sensor on-orbit calibration. This paper provides a brief overview of <span class="hlt">MODIS</span> and VIIRS instrument on-orbit calibration and characterization activities. It describes the approaches and strategies developed to schedule and perform on-orbit lunar observations. Specific applications of <span class="hlt">MODIS</span> and VIIRS lunar observations discussed in this paper include radiometric calibration stability monitoring and performance assessment of sensor spatial characterization. Results derived from lunar observations, such as sensor response (or gain) trending and band-to-band registration, are compared with that derived from sensor OBC. The methodologies and applications presented in this paper can also be applied to other earth observing sensors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRG..121..855P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRG..121..855P"><span id="translatedtitle">Retrieval of seasonal dynamics of forest understory <span class="hlt">reflectance</span> from semiarid to boreal forests using <span class="hlt">MODIS</span> BRDF data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pisek, Jan; Chen, Jing M.; Kobayashi, Hideki; Rautiainen, Miina; Schaepman, Michael E.; Karnieli, Arnon; Sprinstin, Michael; Ryu, Youngryel; Nikopensius, Maris; Raabe, Kairi</p> <p>2016-03-01</p> <p>Spatial and temporal patterns of forest background (understory) <span class="hlt">reflectance</span> are crucial for retrieving biophysical parameters of forest canopies (overstory) and subsequently for ecosystem modeling. In this communication, we retrieved seasonal courses of understory normalized difference vegetation index (NDVI) from multiangular Moderate Resolution Imaging Spectroradiometer bidirectional <span class="hlt">reflectance</span> distribution function (<span class="hlt">MODIS</span> BRDF)/albedo data. We compared satellite-based seasonal courses of understory NDVI to understory NDVI values measured in different types of forests distributed along a wide latitudinal gradient (65.12°N-31.35°N). Our results indicated that the retrieval method performs well particularly over open forests of different types. We also demonstrated the limitations of the method for closed canopies, where the understory signal retrieval is much attenuated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020043308','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020043308"><span id="translatedtitle">Theoretical Basis for the Surface Spectral <span class="hlt">Reflectance</span> Relationships Used in the <span class="hlt">MODIS</span> Aerosol Algorithm</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kaufman, Yoram J.; Gobron, Nadine; Pinty, Bernard; Widlowski, Jean-Luc; Verstraete, Michel M.; Lau, William K. M. (Technical Monitor)</p> <p>2001-01-01</p> <p>The analysis of data from the <span class="hlt">MODIS</span> instrument on the Terra platform to derive global distribution of aerosols assumes a set of relationships between the blue, rho (sub blue), the red, rho (sub red), and 2.1 micrometers, rho (sub 2.1), spectral channels. These relations have been established from a series of measurements indicating that rho (sub blue) approximately 0.5 rho (sub red) approximately 0.25 rho (sub 2.1). Here we use a model to describe the transfer of radiation through a vegetation canopy composed of randomly oriented leaves to assess the theoretical foundations for these relationships. The influence of varying fractional vegetation coverage is simulated simply as a linear combination of pure soil and pure vegetation conditions, also known as Independent Pixel Approximation (IPA). Calculations for a wide range of leaf area indices and vegetation fractions show that rho (sub blue) is consistently about 1/4 of rho (sub 2.1) as used by <span class="hlt">MODIS</span> for the whole range of analyzed cases, except for very dark soils, such as those found in burn scars. For its part, the ratio rho (sub red)/rho (sub 2.1) varies from less than the empirically derived value of 1/2 for dense and dark vegetation (rho (sub 2.1) less than 0.1), to more than 1/2 for bright mixture of soil and vegetation. This is in agreement with measurements over uniform dense vegetation, but not with measurements over mixed dark scenes. In the later case, the discrepancy is probably mitigated by shadows due to uneven canopy and terrain on a large scale. It is concluded that the value of this ratio should ideally be made dependent on the land cover type in the operational processing of <span class="hlt">MODIS</span> data, especially over dense forests.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030102194','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030102194"><span id="translatedtitle">The <span class="hlt">MODIS</span> Aerosol Algorithm, Products and Validation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Remer, L. A.; Kaufman, Y. J.; Tanre, D.; Mattoo, S.; Chu, D. A.; Martins, J. V.; Li, R.-R.; Ichoku, C.; Levy, R. C.; Kleidman, R. G.</p> <p>2003-01-01</p> <p>The MODerate resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) aboard both NASA's Terra and <span class="hlt">Aqua</span> satellites is making near global daily observations of the earth in a wide spectral range. 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 <span class="hlt">reflected</span> spectral solar flux at top of atmosphere. Over ocean, the aerosol optical thickness is provided in seven wavelengths from 0.47 microns to 2.13 microns. In addition, quantitative aerosol size information includes effective radius of the aerosol and quantitative fraction of optical thickness attributed to the fine mode. Spectral aerosol flux, 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 AERONET data gleaned from 133 AERONET stations. 8000 <span class="hlt">MODIS</span> aerosol retrievals colocated with AERONET measurements confirm that one-standard deviation of <span class="hlt">MODIS</span> optical thickness retrievals fall within the predicted uncertainty of delta tauapproximately equal to plus or minus 0.03 plus or minus 0.05 tau over ocean and delta tay equal to plus or minus 0.05 plus or minus 0.15 tau over land. 271 <span class="hlt">MODIS</span> aerosol retrievals co-located with AERONET inversions at island and coastal sites suggest that one-standard deviation of <span class="hlt">MODIS</span> effective radius retrievals falls within delta r_eff approximately equal to 0.11 microns. The accuracy of the <span class="hlt">MODIS</span> retrievals suggests that the product can be used to help narrow the uncertainties associated with aerosol radiative forcing of global climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMIN11A1452C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMIN11A1452C"><span id="translatedtitle">Uncertainty analysis of the SPOT 4 VEGETATION and <span class="hlt">MODIS</span> surface <span class="hlt">reflectance</span> products, and its impact on vegetation indices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Czapla-Myers, J.</p> <p>2012-12-01</p> <p>Vegetation indices (VIs) are used to monitor the spatial and temporal variations of global vegetation. They provide essential measurements for climate, phenology, and land cover change detection. VIs are typically determined from surface <span class="hlt">reflectance</span> data that are collected using spaceborne platforms. In order to understand the uncertainty of long-term data records, it is important to understand the uncertainty of the inputs that are used to determine the VIs. The Remote Sensing Group (RSG) at the University of Arizona uses the <span class="hlt">reflectance</span>-based approach to perform the absolute radiometric calibration of airborne and satellite sensors in the solar-<span class="hlt">reflective</span> regime. During a typical field campaign, measurements of the atmosphere and surface are made during a sensor overpass. The surface <span class="hlt">reflectance</span> is measured using a portable spectroradiometer that operates from 400-2500 nm. This work uses in situ data that were obtained at White Sands Missile Range, New Mexico, and Railroad Valley, Nevada. The surface <span class="hlt">reflectance</span> data are compared to those reported by SPOT 4 VEGETATION and both <span class="hlt">MODIS</span> sensors to acquire an understanding of the uncertainty in the VI data product.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SPIE.9639E..11A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SPIE.9639E..11A"><span id="translatedtitle">Cross-calibration of the <span class="hlt">reflective</span> solar bands of Terra <span class="hlt">MODIS</span> and Landsat 7 Enhanced Thematic Mapper plus over PICS using different approaches</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Angal, Amit; Brinkmann, Jake; Mishra, Nischal; Link, Daniel; Xiong, Xiaoxiong J.; Helder, Dennis</p> <p>2015-10-01</p> <p>Both Terra <span class="hlt">MODIS</span> and Landsat 7 (L7) Enhanced Thematic Mapper Plus (ETM+) have been successfully operating for over 15 years to collect valuable measurements of the earth's land, ocean, and atmosphere. The land-viewing bands of both sensors are widely used in several scientific products such as surface <span class="hlt">reflectance</span>, normalized difference vegetation index, enhanced vegetation index etc. A synergistic use of the multi-temporal measurements from both sensors can greatly benefit the science community. Previous effort from the <span class="hlt">MODIS</span> Characterization Support Team (MCST) was focused on comparing the top-of-atmosphere <span class="hlt">reflectance</span> of the two sensors over Libya 4 desert target. Uncertainties caused by the site/atmospheric BRDF, spectral response mismatch, and atmospheric water-vapor were also characterized. In parallel, an absolute calibration approach based on empirical observation was also developed for the Libya 4 site by the South Dakota State University's (SDSU) Image Processing Lab. Observations from Terra <span class="hlt">MODIS</span> and Earth Observing One (EO-1) Hyperion were used to model the Landsat ETM+ TOA <span class="hlt">reflectance</span>. Recently, there has been an update to the <span class="hlt">MODIS</span> calibration algorithm, which has resulted in the newly reprocessed Collection 6 Level 1B calibrated products. Similarly, a calibration update to some ETM+ bands has also resulted in long-term improvements of its calibration accuracy. With these updates, calibration differences between the spectrally matching bands of Terra <span class="hlt">MODIS</span> and L7 ETM+ over the Libya 4 site are evaluated using both approaches.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24287529','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24287529"><span id="translatedtitle">Comparability of red/near-infrared <span class="hlt">reflectance</span> and NDVI based on the spectral response function between <span class="hlt">MODIS</span> and 30 other satellite sensors using rice canopy spectra.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Huang, Weijiao; Huang, Jingfeng; Wang, Xiuzhen; Wang, Fumin; Shi, Jingjing</p> <p>2013-01-01</p> <p>Long-term monitoring of regional and global environment changes often depends on the combined use of multi-source sensor data. The most widely used vegetation index is the normalized difference vegetation index (NDVI), which is a function of the red and near-infrared (NIR) spectral bands. The <span class="hlt">reflectance</span> and NDVI data sets derived from different satellite sensor systems will not be directly comparable due to different spectral response functions (SRF), which has been recognized as one of the most important sources of uncertainty in the multi-sensor data analysis. This study quantified the influence of SRFs on the red and NIR <span class="hlt">reflectances</span> and NDVI derived from 31 Earth observation satellite sensors. For this purpose, spectroradiometric measurements were performed for paddy rice grown under varied nitrogen levels and at different growth stages. The rice canopy <span class="hlt">reflectances</span> were convoluted with the spectral response functions of various satellite instruments to simulate sensor-specific <span class="hlt">reflectances</span> in the red and NIR channels. NDVI values were then calculated using the simulated red and NIR <span class="hlt">reflectances</span>. The results showed that as compared to the Terra <span class="hlt">MODIS</span>, the mean relative percentage difference (RPD) ranged from -12.67% to 36.30% for the red <span class="hlt">reflectance</span>, -8.52% to -0.23% for the NIR <span class="hlt">reflectance</span>, and -9.32% to 3.10% for the NDVI. The mean absolute percentage difference (APD) compared to the Terra <span class="hlt">MODIS</span> ranged from 1.28% to 36.30% for the red <span class="hlt">reflectance</span>, 0.84% to 8.71% for the NIR <span class="hlt">reflectance</span>, and 0.59% to 9.32% for the NDVI. The lowest APD between <span class="hlt">MODIS</span> and the other 30 satellite sensors was observed for Landsat5 TM for the red <span class="hlt">reflectance</span>, CBERS02B CCD for the NIR <span class="hlt">reflectance</span> and Landsat4 TM for the NDVI. In addition, the largest APD between <span class="hlt">MODIS</span> and the other 30 satellite sensors was observed for IKONOS for the red <span class="hlt">reflectance</span>, AVHRR1 onboard NOAA8 for the NIR <span class="hlt">reflectance</span> and IKONOS for the NDVI. The results also indicated that AVHRRs onboard NOAA7-17 showed</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3892887','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3892887"><span id="translatedtitle">Comparability of Red/Near-Infrared <span class="hlt">Reflectance</span> and NDVI Based on the Spectral Response Function between <span class="hlt">MODIS</span> and 30 Other Satellite Sensors Using Rice Canopy Spectra</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Huang, Weijiao; Huang, Jingfeng; Wang, Xiuzhen; Wang, Fumin; Shi, Jingjing</p> <p>2013-01-01</p> <p>Long-term monitoring of regional and global environment changes often depends on the combined use of multi-source sensor data. The most widely used vegetation index is the normalized difference vegetation index (NDVI), which is a function of the red and near-infrared (NIR) spectral bands. The <span class="hlt">reflectance</span> and NDVI data sets derived from different satellite sensor systems will not be directly comparable due to different spectral response functions (SRF), which has been recognized as one of the most important sources of uncertainty in the multi-sensor data analysis. This study quantified the influence of SRFs on the red and NIR <span class="hlt">reflectances</span> and NDVI derived from 31 Earth observation satellite sensors. For this purpose, spectroradiometric measurements were performed for paddy rice grown under varied nitrogen levels and at different growth stages. The rice canopy <span class="hlt">reflectances</span> were convoluted with the spectral response functions of various satellite instruments to simulate sensor-specific <span class="hlt">reflectances</span> in the red and NIR channels. NDVI values were then calculated using the simulated red and NIR <span class="hlt">reflectances</span>. The results showed that as compared to the Terra <span class="hlt">MODIS</span>, the mean relative percentage difference (RPD) ranged from −12.67% to 36.30% for the red <span class="hlt">reflectance</span>, −8.52% to −0.23% for the NIR <span class="hlt">reflectance</span>, and −9.32% to 3.10% for the NDVI. The mean absolute percentage difference (APD) compared to the Terra <span class="hlt">MODIS</span> ranged from 1.28% to 36.30% for the red <span class="hlt">reflectance</span>, 0.84% to 8.71% for the NIR <span class="hlt">reflectance</span>, and 0.59% to 9.32% for the NDVI. The lowest APD between <span class="hlt">MODIS</span> and the other 30 satellite sensors was observed for Landsat5 TM for the red <span class="hlt">reflectance</span>, CBERS02B CCD for the NIR <span class="hlt">reflectance</span> and Landsat4 TM for the NDVI. In addition, the largest APD between <span class="hlt">MODIS</span> and the other 30 satellite sensors was observed for IKONOS for the red <span class="hlt">reflectance</span>, AVHRR1 onboard NOAA8 for the NIR <span class="hlt">reflectance</span> and IKONOS for the NDVI. The results also indicated that AVHRRs onboard NOAA7</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120015744','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120015744"><span id="translatedtitle">Evaluating the Assumptions of Surface <span class="hlt">Reflectance</span> and Aerosol Type Selection Within the <span class="hlt">MODIS</span> Aerosol Retrieval Over Land: The Problem of Dust Type Selection</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mielonen, T.; Levy, R. C.; Aaltonen, V.; Komppula, M.; de Leeuw, G.; Huttunen, J.; Lihavainen, H.; Kolmonen, P.; Lehtinen, K. E. J.; Arola, A.</p> <p>2011-01-01</p> <p>Aerosol Optical Depth (AOD) and Angstrom exponent (AE) values derived with the <span class="hlt">MODIS</span> retrieval algorithm over land (Collection 5) are compared with ground based sun photometer measurements at eleven sites spanning the globe. Although, in general, total AOD compares well at these sites (R2 values generally over 0.8), there are cases (from 2 to 67% of the measurements depending on the site) where <span class="hlt">MODIS</span> clearly retrieves the wrong spectral dependence, and hence, an unrealistic AE value. Some of these poor AE retrievals are due to the aerosol signal being too small (total AOD<0.3) but in other cases the AOD should have been high enough to derive accurate AE. However, in these cases, <span class="hlt">MODIS</span> indicates AE values close to 0.6 and zero fine model weighting (FMW), i.e. dust model provides the best fitting to the <span class="hlt">MODIS</span> observed <span class="hlt">reflectance</span>. Yet, according to evidence from the collocated sun photometer measurements and back-trajectory analyses, there should be no dust present. This indicates that the assumptions about aerosol model and surface properties made by the <span class="hlt">MODIS</span> algorithm may have been incorrect. Here we focus on problems related to parameterization of the land-surface optical properties in the algorithm, in particular the relationship between the surface <span class="hlt">reflectance</span> at 660 and 2130 nm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997JGR...10229529P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997JGR...10229529P"><span id="translatedtitle">Estimating spectral albedo and nadir <span class="hlt">reflectance</span> through inversion of simple BRDF models with AVHRR/<span class="hlt">MODIS</span>-like data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Privette, Jeffrey L.; Eck, Thomas F.; Deering, Donald W.</p> <p>1997-12-01</p> <p>In recent years, many computationally efficient bidirectional <span class="hlt">reflectance</span> models have been developed to account for angular effects in land remote sensing data, particularly those from the NOAA advanced very high resolution radiometer (AVHRR), polarization and directionality of the Earth's <span class="hlt">reflectances</span> (POLDER), and the planned EOS moderate-resolution imaging spectrometer (<span class="hlt">MODIS</span>) and multi-angle imaging spectroradiometer (MISR) sensors. In this study, we assessed the relative ability of 10 such models to predict commonly used remote sensing products (nadir <span class="hlt">reflectance</span> and albedo). Specifically, we inverted each model with ground-based data from the portable apparatus for rapid acquisition of bidirectional observations of the land and atmosphere (PARABOLA) arranged in subsets representative of satellite sampling geometries. We used data from nine land cover types, ranging from soil to grassland (First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE)) to forest (Boreal Ecosystem-Atmosphere Study (BOREAS)). Retrieved parameters were used in forward model runs to estimate nadir <span class="hlt">reflectance</span> and spectral albedo over a wide range of solar angles. We rank the models by the accuracy of the estimated products and find results to be strongly dependent on the view azimuth angle range of the inversion data, and less dependent on the spectral band and land cover type. Overall, the nonlinear model of Rahman et al. [993] and the linear kernel-driven RossThickLiSparse model [Wanner et al., 1995] were most accurate. The latter was at least 25 times faster to invert than the former. Interestingly, we found these two models were not able to match the various bidirectional <span class="hlt">reflectance</span> distribution function (BRDF) shapes as well as other models, suggesting their superior performance lies in their ability to be more reliably inverted with sparse data sets. These results should be useful to those interested in the computationally fast normalization</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120007859','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120007859"><span id="translatedtitle">An Overview of <span class="hlt">MODIS</span> On-orbit Operation, Calibration, and Lessons</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Xiong, Jack; Barnes, William; Salomonson, Vincent</p> <p>2012-01-01</p> <p>Two nearly identical copies of the Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) have successfully operated onboard the Terra and <span class="hlt">Aqua</span> spacecraft for more than II years and 9 years since their launch in December 1999 and May 2002, respectively. <span class="hlt">MODIS</span> is a key instrument for the NASA's Earth Observing System (EOS) missions. <span class="hlt">MODIS</span> observations have produced an unprecedented amount and a broad range of data products and significantly benefited the science and user community. Its follow-on instrument, the Visible/Infrared Imager Radiometer Suite (VIIRS) on-board the NPOESS Preparatory Project (NPP) spacecraft, is currently scheduled for launch in late October, 2011. The NPP serves as a bridge mission between EOS and the Joint Polar Satellite System (JPSS). <span class="hlt">MODIS</span> collects data in 36 spectral bands, covering spectral regions from visible (VIS) to long-wave infrared (L WIR), and at three different spatial resolutions. Because of its stringent design requirements, <span class="hlt">MODIS</span> was built with a complete set of onboard calibrators, including a solar diffuser (SO), a solar diffuser stability monitor (SDSM), a blackbody (BB), a spectroradiometric calibration assembly (SRCA), and a space view (SV) port. Except for tbe SRCA, VIlRS carries the same set of onboard calibrators as <span class="hlt">MODIS</span>. The SD/SDSM system is used together to calibrate tbe <span class="hlt">reflective</span> solar bands (RSB). The BB is designed for the thermal emissive bands (TEB) calibration. Similar to Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span>, VIlRS will also make regular lunar observations to monitor RSB radiometric calibration stability. In this paper, we provide an overview of <span class="hlt">MODIS</span> on-orbit operation and calibration activities and present issues identified and lessons learned from mission-long instrument operations and implementation of various calibration and characterization strategies. Examples of both Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> instrument on-orbit performance, including their similarities and unique characteristics, are discussed in tbe context of what</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20070031724&hterms=Pressure+products&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DPressure%2Bproducts','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20070031724&hterms=Pressure+products&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DPressure%2Bproducts"><span id="translatedtitle">Introduction to <span class="hlt">MODIS</span> Cloud Products. Chapter 5</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Baum, Bryan A.; Platnick, Steven</p> <p>2006-01-01</p> <p>The Earth's radiative energy balance and hydrological cycle are fundamentally coupled with the distribution and properties of clouds. Therefore, the ability to remotely infer cloud properties and their variation in space and time is crucial for establishing climatologies as a reference for validation of present-day climate models and in assessing future climate change. Remote cloud observations also provide data sets useful for testing and improving cloud model physics, and for assimilation into numerical weather prediction models. The MODerate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) imagers on the Terra and <span class="hlt">Aqua</span> Earth Observing System (EOS) platforms provide the capability for globally retrieving these properties using passive solar <span class="hlt">reflectance</span> and infrared techniques. In addition to providing measurements similar to those offered on a suite of historical operational weather platforms such as the Advanced Very High Resolution Radiometer (AVHRR), the High-resolution Infrared Radiation Sounder (HIRS), and the Geostationary Operational Environmental Satellite (GOES), <span class="hlt">MODIS</span> provides additional spectral and/or spatial resolution in key atmospheric bands, along with on-board calibration, to expand the capability for global cloud property retrievals. The core <span class="hlt">MODIS</span> operational cloud products include cloud top pressure, thermodynamic phase, optical thickness, particle size, and water path, and are derived globally at spatial resolutions of either 1- or 5-km (referred to as Level-2 or pixel-level products). In addition, the <span class="hlt">MODIS</span> atmosphere team (collectively providing cloud, aerosol, and clear sky products) produces a combined gridded product (referred to as Level-3) aggregated to a 1 equal-angle grid, available for daily, eight-day, and monthly time periods. The wealth of information available from these products provides critical information for climate studies as well as the continuation and improved understanding of existing satellite-based cloud climatologies</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010SPIE.7807E..1FW','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010SPIE.7807E..1FW"><span id="translatedtitle"><span class="hlt">MODIS</span> calibration algorithm improvements developed for Collection 6 Level-1B</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wenny, Brian N.; Sun, Junqiang; Xiong, Xiaoxiong; Wu, Aisheng; Chen, Hongda; Angal, Amit; Choi, Taeyoung; Chen, Na; Madhavan, Sriharsha; Geng, Xu; Kuyper, James; Tan, Liqin</p> <p>2010-09-01</p> <p>The Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) has been operating on both the Terra and <span class="hlt">Aqua</span> spacecraft for over 10.5 and 8 years, respectively. Over 40 science products are generated routinely from <span class="hlt">MODIS</span> Earth images and used extensively by the global science community for a wide variety of land, ocean, and atmosphere applications. Over the mission lifetime, several versions of the <span class="hlt">MODIS</span> data set have been in use as the calibration and data processing algorithms evolved. Currently Version 5 <span class="hlt">MODIS</span> data is the baseline Level-1B calibrated science product. The <span class="hlt">MODIS</span> Characterization Support Team (MCST), with input from the <span class="hlt">MODIS</span> Science Team, developed and delivered a number of improvements and enhancements to the calibration algorithms, Level-1B processing code and Look-up Tables for the Version 6 Level-1B <span class="hlt">MODIS</span> data. Version 6 implements a number of changes in the calibration methodology for both the <span class="hlt">Reflective</span> Solar Bands (RSB) and Thermal Emissive Bands (TEB). This paper describes the improvements introduced in Collection 6 to the RSB and TEB calibration and detector Quality Assurance (QA) handling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.H43G1568J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.H43G1568J"><span id="translatedtitle">Blending and Downscaling of Landsat and <span class="hlt">MODIS</span> Surface <span class="hlt">Reflectance</span> for Water Body Delineation: A Comparison of Index-Simulate and Simulate-Index Methods</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jarihani, A.; Callow, J. N.; McVicar, T.; Van Niel, T.; Johansen, K.; Emelyanova, I.</p> <p>2013-12-01</p> <p>Single-sensor satellite remotely sensed data are typically either high temporal and low spatial resolution (e.g. <span class="hlt">MODIS</span>) or low temporal and high spatial resolution (e.g. Landsat). Blending algorithms have been developed to overcome this limitation by predicting the composition of higher spatial and temporal resolution band data by blending individual corresponding bands of two sensors. The objective of this paper was to evaluate the accuracy of two advanced algorithms (STARFM and ESTARFM) in blending single bands and indices to downscale <span class="hlt">MODIS</span> pixels (250-500 m) to Landsat resolution (28.5 m). We test two approaches to predicting indices: i) Index-Simulate (IS)-(i.e., indices directly predicted including EVI, NDVI NDWI24 and NDWI 27) from Landsat-<span class="hlt">MODIS</span> pairs) and ii) Simulate- Index (SI)-(i.e. indices were calculated from five predicted bands (Blue, Green, Red, Near-Infrared and Mid-Infrared). Landsat-like images and indices (IS and SI) were predicted for 18 dates by using 20 pairs of cloud-free Landsat 5 TM and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> images and compared with observed Landsat images and indices. Based on RMSD (accuracy of predicted and observed bands and indices), pixel-to-pixel accuracy of each prediction and R-squared differences of predicted and observed pixels, ESTARFM produced a lower error than STARFM in predicting all four tested indices. Results of IS and SI methods showed that, both algorithms predict indices in IS method with higher accuracy than using SI method. That is, if interested in using indices in applications it best to calculate the index at the two resolutions then use the algorithms to simulate the index as opposed to simulating the individual bands then subsequently calculating the index. This study shows that, the high spatio-temporal resolution predicted water index (NDWI) can be used in water resources applications. Landsat-like daily water indices simulated by using blending Landsat and <span class="hlt">MODIS</span> data provided daily flood inundation footprint. These</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..18.5138P&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..18.5138P&link_type=ABSTRACT"><span id="translatedtitle">Retrieval of seasonal dynamics of forest understory <span class="hlt">reflectance</span> from semi-arid to boreal forests using <span class="hlt">MODIS</span> BRDF data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pisek, Jan; Chen, Jing; Kobayashi, Hideki; Rautiainen, Miina; Schaepman, Michael; Karnieli, Arnon; Sprintsin, Michael; Ryu, Youngryel; Nikopensius, Maris; Raabe, Kairi</p> <p>2016-04-01</p> <p>Ground vegetation (understory) provides an essential contribution to the whole-stand <span class="hlt">reflectance</span> signal in many boreal, sub-boreal, and temperate forests. Accurate knowledge about forest understory <span class="hlt">reflectance</span> is urgently needed in various forest <span class="hlt">reflectance</span> modelling efforts. However, systematic collections of understory <span class="hlt">reflectance</span> data covering different sites and ecosystems are almost missing. Measurement of understory <span class="hlt">reflectance</span> is a real challenge because of an extremely high variability of irradiance at the forest floor, weak signal in some parts of the spectrum, spectral separability issues of over- and understory and its variable nature. Understory can consist of several sub-layers (regenerated tree, shrub, grasses or dwarf shrub, mosses, lichens, litter, bare soil), it has spatially-temporally variable species composition and ground coverage. Additional challenges are introduced by patchiness of ground vegetation, ground surface roughness, and understory-overstory relations. Due to this variability, remote sensing might be the only means to provide consistent data at spatially relevant scales. In this presentation, we report on retrieving seasonal courses of understory Normalized Difference Vegetation Index (NDVI) from multi-angular <span class="hlt">MODIS</span> BRDF/Albedo data. We compared satellite-based seasonal courses of understory NDVI against an extended collection of different types of forest sites with available in-situ understory <span class="hlt">reflectance</span> measurements. These sites are distributed along a wide latitudinal gradient on the Northern hemisphere: a sparse and dense black spruce forests in Alaska and Canada, a northern European boreal forest in Finland, hemiboreal needleleaf and deciduous stands in Estonia, a mixed temperate forest in Switzerland, a cool temperate deciduous broadleaf forest in Korea, and a semi-arid pine plantation in Israel. Our results indicated the retrieval method performs well particularly over open forests of different types. We also demonstrated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.B41E0376R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.B41E0376R"><span id="translatedtitle">Understanding QA: The Key to Defining the Usability and Usefulness of <span class="hlt">MODIS</span> Land Products</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ramachandran, B.; Meyer, D. J.</p> <p>2012-12-01</p> <p>NASA's Earth Observing System (EOS) ushered in an era of global Earth system science that benefits those studying all aspects of Earth's land, atmosphere, and oceans components. The Terra and <span class="hlt">Aqua</span> missions support nearly identical Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) instruments that have helped spawn an entirely new array of validated geophysical products at multiple spatial and temporal resolutions. The <span class="hlt">MODIS</span> land products continue to contribute to address key requirements for monitoring land surface processes and dynamics. The public has access to a <span class="hlt">MODIS</span> land product's archive that contains over 27 million granules (~590 TB in volume). Given such an access to a huge data collection, the usability and usefulness of those products can pose serious challenges to end-users attempting to use them in various applications. To address these challenges, the <span class="hlt">MODIS</span> mission incorporates in-depth pixel-level quality assurance (QA) layers that provide a wealth of information for those who know how to tap it. This study focuses on QA information that is encapsulated with the different <span class="hlt">MODIS</span> land products. Following a descriptive preamble of <span class="hlt">MODIS</span> land products and QA, a sizable portion is devoted to identifying why it is important for users to consult and use the QA information. Next, guidelines to identify the specific QA metadata sources in different <span class="hlt">MODIS</span> product suites are provided. The following section addresses the mechanics of deconstructing pixel-level QA, which is deemed extremely vital for applied science users. Examples of how QA information is handled and interpreted in three <span class="hlt">MODIS</span> land product suites are provided, including Land Surface <span class="hlt">Reflectance</span>, Bi-directional <span class="hlt">Reflectance</span> Distribution Function and Albedo, and Vegetation Indices. It closes with a variety of information on <span class="hlt">MODIS</span> QA-specific tools and online resources deemed helpful to end-users.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70010012','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70010012"><span id="translatedtitle"><span class="hlt">MODIS</span> and SeaWIFS on-orbit lunar calibration</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Sun, Jielun; Eplee, R.E., Jr.; Xiong, X.; Stone, T.; Meister, G.; McClain, C.R.</p> <p>2008-01-01</p> <p>The Moon plays an important role in the radiometric stability monitoring of the NASA Earth Observing System's (EOS) remote sensors. The <span class="hlt">MODIS</span> and SeaWIFS are two of the key instruments for NASA's EOS missions. The <span class="hlt">MODIS</span> Protoflight Model (PFM) on-board the Terra spacecraft and the <span class="hlt">MODIS</span> Flight Model 1 (FM1) on-board the <span class="hlt">Aqua</span> 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 <span class="hlt">Reflective</span> Solar Bands (RSB). SeaWIFS was launched on-board the OrbView-2 spacecraft on August 1, 1997. The SeaWiFS lunar calibrations are obtained once a month at a nominal phase angle of 7??. The lunar irradiance observed by these instruments depends on the viewing geometry. The USGS photometric model of the Moon (the ROLO model) has been developed to provide the geometric corrections for the lunar observations. For <span class="hlt">MODIS</span>, the lunar view responses with corrections for the viewing geometry are used to track the gain change for its <span class="hlt">reflective</span> solar bands (RSB). They trend the system response degradation at the Angle Of Incidence (AOI) of sensor's SV port. With both the lunar observation and the on-board Solar Diffuser (SD) calibration, it is shown that the <span class="hlt">MODIS</span> system response degradation is wavelength, mirror side, and AOI dependent. Time-dependent Response Versus Scan angle (RVS) Look-Up Tables (LUT) are applied in <span class="hlt">MODIS</span> RSB calibration and lunar observations play a key role in RVS derivation. The corrections provided by the RVS in the Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> data from the 412 nm band are as large as 16% and 13%, respectively. For SeaWIFS lunar calibrations, the spacecraft is pitched across the Moon so that the instrument views the Moon near nadir through the same optical path as it views the Earth. The SeaWiFS system gain changes for its eight bands are calibrated using the geometrically-corrected lunar observations. The radiometric</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000033817','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000033817"><span id="translatedtitle">Sensitivity of Cirrus Bidirectional <span class="hlt">Reflectance</span> at <span class="hlt">MODIS</span> Bands to Vertical Inhomogeneity of Ice Crystal Habits and Size Distribution</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yang, P.; Gao, B.-C.; Baum, B. A.; Wiscombe, W.; Hu, Y.; Nasiri, S. L.; Soulen, P. F.; Heymsfield, A. J.; McFarquhar, G. M.; Miloshevich, L. M.</p> <p>2000-01-01</p> <p>A common assumption in satellite imager-based cirrus retrieval algorithms is that the radiative properties of a cirrus cloud may be represented by those associated with a specific ice crystal shape (or habit) and a single particle size distribution. However, observations of cirrus clouds have shown that the shapes and sizes of ice crystals may vary substantially with height within the clouds. In this study we investigate the sensitivity of the top-of-atmosphere bidirectional <span class="hlt">reflectances</span> at two <span class="hlt">MODIS</span> bands centered at 0.65 micron and 2.11 micron to the cirrus models assumed to be either a single homogeneous layer or three distinct but contiguous, layers. First, we define the single- and three-layer cirrus cloud models with respect to ice crystal habit and size distribution on the basis of in situ replicator data acquired during the First ISCCP Regional Experiment (FIRE-II), held in Kansas during the fall of 1991. Subsequently, fundamental light scattering and radiative transfer theory is employed to determine the single scattering and the bulk radiative properties of the cirrus cloud. Regarding the radiative transfer computations, we present a discrete form of the adding/doubling principle by introducing a direct transmission function, which is computationally straightforward and efficient an improvement over previous methods. For the 0.65 micron band, at which absorption by ice is negligible, there is little difference between the bidirectional <span class="hlt">reflectances</span> calculated for the one- and three-layer cirrus models, suggesting that the vertical inhomogeneity effect is relatively unimportant. At the 2.11 micron band, the bidirectional <span class="hlt">reflectances</span> computed for both optically thin (tau = 1) and thick (tau = 10) cirrus clouds show significant differences between the results for the one- and three-layer models. The <span class="hlt">reflectances</span> computed for the three-layer cirrus model are substantially larger than those computed for the single-layer cirrus. Finally, we find that cloud</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SPIE.9607E..1TX','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SPIE.9607E..1TX"><span id="translatedtitle">Assessment of <span class="hlt">MODIS</span> and VIIRS solar diffuser on-orbit degradation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiong, Xiaoxiong; Fulbright, Jon; Angal, Amit; Wang, Zhipeng; Geng, Xu; Butler, Jim</p> <p>2015-09-01</p> <p>Both <span class="hlt">MODIS</span> and VIIRS instruments use a solar diffuser (SD) for their <span class="hlt">reflective</span> solar bands (RSB) on-orbit calibration. On-orbit changes in SD bi-directional <span class="hlt">reflectance</span> factor (BRF) are tracked by a solar diffuser stability monitor (SDSM) using its alternate measurements of the sunlight <span class="hlt">reflected</span> off the SD panel and direct sunlight through a fixed attenuation screen. The SDSM calibration data are collected by a number of filtered detectors, covering wavelengths from 0.41 to 0.94μm. In this paper we describe briefly the Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> and S-NPP VIIRS SDSM on-orbit operation and calibration activities and strategies, provide an overall assessment of their SDSM on-orbit performance, including wavelength-dependent changes in the SDSM detector responses and changes in their SD BRF, and discuss remaining challenging issues and their potential impact on RSB calibration quality. Due to different launch dates, operating configurations, and calibration frequencies, the Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> and S-NPP VIIRS SD have experienced different amount of SD degradation. However, in general the shorter the wavelength, the larger is the SD on-orbit degradation. On the other hand, the larger changes in SDSM detector responses are observed at longer wavelengths in the near infrared (NIR).</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20160005181&hterms=assessment&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dassessment','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20160005181&hterms=assessment&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dassessment"><span id="translatedtitle">Assessment of <span class="hlt">MODIS</span> and VIIRS Solar Diffuser On-Orbit Degradation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Xiong, Xiaoxiong; Fulbright, Jon; Angal, Amit; Wang, Zhipeng; Geng, Xu; Butler, Jim</p> <p>2015-01-01</p> <p>Both <span class="hlt">MODIS</span> and VIIRS instruments use a solar diffuser (SD) for their <span class="hlt">reflective</span> solar bands (RSB) on-orbit calibration. On-orbit changes in SD bi-directional <span class="hlt">reflectance</span> factor (BRF) are tracked by a solar diffuser stability monitor (SDSM) using its alternate measurements of the sunlight <span class="hlt">reflected</span> off the SD panel and direct sunlight through a fixed attenuation screen. The SDSM calibration data are collected by a number of filtered detectors, covering wavelengths from 0.41 to 0.94 micrometers. In this paper we describe briefly the Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> and S-NPP VIIRS SDSM on-orbit operation and calibration activities and strategies, provide an overall assessment of their SDSM on-orbit performance, including wavelength-dependent changes in the SDSM detector responses and changes in their SD BRF, and discuss remaining challenging issues and their potential impact on RSB calibration quality. Due to different launch dates, operating configurations, and calibration frequencies, the Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> and S-NPP VIIRS SD have experienced different amount of SD degradation. However, in general the shorter the wavelength, the larger is the SD on-orbit degradation. On the other hand, the larger changes in SDSM detector responses are observed at longer wavelengths in the near infrared (NIR).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012SPIE.8510E..0IC','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012SPIE.8510E..0IC"><span id="translatedtitle">Recent progress of <span class="hlt">MODIS</span> solar diffuser on-orbit degradation characterization</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, H.; Wang, Z.; Sun, J.; Angal, A.; Xiong, X.</p> <p>2012-09-01</p> <p>An on-board Solar Diffuser (SD) is used for the <span class="hlt">MODIS</span> <span class="hlt">reflective</span> solar bands (RSB) calibration. Its on-orbit bidirectional <span class="hlt">reflectance</span> factor (BRF) degradation is tracked using an on-board Solar Diffuser Stability Monitor (SDSM). The SDSM is a ratioing radiometer with nine detectors, covering wavelengths from 412 nm to 936 nm. During each scheduled SD calibration event, the SDSM makes alternate observations of the Sun and the sunlight <span class="hlt">reflected</span> by the SD. To best match the SDSM detector signals from its Sun view and SD view, a fix attenuation screen is placed in its Sun view path. This paper provides a brief description of <span class="hlt">MODIS</span> RSB on-orbit calibration and the use of its on-board SD and SDSM subsystem, including different approaches developed and used to track <span class="hlt">MODIS</span> SD on-orbit degradation. It reports recent progress made to better characterize <span class="hlt">MODIS</span> SD on-orbit degradation and to support <span class="hlt">MODIS</span> Level 1B (L1B) calibration look-up table (LUT) updates for the upcoming collection 6 (C6) reprocessing. Results of both Terra and <span class="hlt">Aqua</span> SD on-orbit degradation derived from newly improved SDSM Sun view screen vignetting function and response fitting strategy, and their impact on RSB calibration uncertainties are also presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010SPIE.7807E..0GD','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010SPIE.7807E..0GD"><span id="translatedtitle">Space environment's effect on <span class="hlt">MODIS</span> calibration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dodd, J. L.; Wenny, B. N.; Chiang, K.; Xiong, X.</p> <p>2010-09-01</p> <p>The MODerate resolution Imaging Spectroradiometer flies on board the Earth Observing System (EOS) satellites Terra and <span class="hlt">Aqua</span> in a sun-synchronous orbit that crosses the equator at 10:30 AM and 2:30 PM, respectively, at a low earth orbit (LEO) altitude of 705 km. Terra was launched on December 18,1999 and <span class="hlt">Aqua</span> was launched on May 4, 2002. As the <span class="hlt">MODIS</span> instruments on board these satellites continue to operate beyond the design lifetime of six years, the cumulative effect of the space environment on <span class="hlt">MODIS</span> and its calibration is of increasing importance. There are several aspects of the space environment that impact both the top of atmosphere (TOA) calibration and, therefore, the final science products of <span class="hlt">MODIS</span>. The south Atlantic anomaly (SAA), spacecraft drag, extreme radiative and thermal environment, and the presence of orbital debris have the potential to significantly impact both <span class="hlt">MODIS</span> and the spacecraft, either directly or indirectly, possibly resulting in data loss. Efforts from the Terra and <span class="hlt">Aqua</span> Flight Operations Teams (FOT), the <span class="hlt">MODIS</span> Instrument Operations Team (IOT), and the <span class="hlt">MODIS</span> Characterization Support Team (MCST) prevent or minimize external impact on the TOA calibrated data. This paper discusses specific effects of the space environment on <span class="hlt">MODIS</span> and how they are minimized.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.H51G1461C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.H51G1461C"><span id="translatedtitle">Towards the assimilation of <span class="hlt">MODIS</span> <span class="hlt">reflectance</span> into the detailed snowpack model SURFEX/ISBA-Crocus.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Charrois, L.; Cosme, E.; Dumont, M.; Lafaysse, M.; Morin, S.; Libois, Q.; Picard, G.</p> <p>2015-12-01</p> <p>Numerical simulations of snow on the ground are used for numerous scientific and operational applications such as avalanche hazard forecasting. Although the chain of models used in French mountain ranges for meteorological analysis and forecast (SAFRAN) and detailed snowpack modeling (SURFEX/ISBA-Crocus) usually perform reasonably well, significant differences with snowpack observations are common and are primarily attributed to the uncertainties in meteorological input and to the heterogeneity of snowpack conditions at all scales. So far, no snow observation is assimilated into this model chain, so that simulation errors can accumulate over the winter season. Current efforts are devoted to the assimilation of data from visible and near-infrared imagers into the snowpack model. These efforts rely on the recently developed "TARTES" optical scheme that computes <span class="hlt">reflectances</span> at various wavelengths using the vertical profile of the physical properties of snow predicted by the snowpack model. In a first step, we performed ensemble simulations by perturbing the atmospheric forcing consistently with its estimated uncertainty. These experiments showed that the simulated snowpack evolution is extremely sensitive to this uncertainty, and that the assimilation of observations can greatly improve model results. In a second step, we performed assimilation experiments using synthetic imager observations and a particle filter. The experiments were carried out for the location of Col du Lautaret area (French Alps) over 5 hydrologic seasons. They provide a good insight about the potential and limitations of assimilating imager data to improve the representation of the snowpack.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20030112964&hterms=clam&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dclam','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20030112964&hterms=clam&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dclam"><span id="translatedtitle">Towards Improved <span class="hlt">MODIS</span> Aerosol Retrieval over the US East Coast Region: Re-examining the Aerosol Model and Surface Assumptions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Levy, R. C.; Remer, L. A.; Kaufman, Y. J.; Holben, B. N.</p> <p>2002-01-01</p> <p>The MODerate resolution Imaging Spectrometer (<span class="hlt">MODIS</span>) aboard the Terra and recently the <span class="hlt">Aqua</span> platform, produces a set of aerosol products over both ocean and land regions. Previous validation efforts have shown that from a global perspective, aerosol optical depth (AOD) is successfully retrieved from <span class="hlt">MODIS</span>. Even over coastal regions, the over- land and over-ocean retrievals are consistent with each other, and well matched with ground-based sunphotometer measurements (such as AERONET). However, the East Coast of the United States is one region where there is consistently a discrepancy between land and ocean retrievals. Over the ocean, <span class="hlt">MODIS</span> AODs are consistent with coastal sunphotometer measurements, but over land, AODs are consistently over- estimated. In this study we use field data from the Chesapeake Lighthouse and Aircraft Measurements for Satellites experiment (CLAMS), (held during summer 2001) to determine the aerosol properties at a number of sites. Using the 6-S radiative transfer package, we compute simulated satellite radiances and compare them with observed <span class="hlt">MODIS</span> radiances. We believe that the AOD over-estimation is not likely due to an incorrect choice of the urban/industrial aerosol models. Using 6-S to do an atmospheric correction for a very low AOD case, we show rather, that the discrepancies are likely a result of incorrect assumptions about the surface <span class="hlt">reflectance</span> properties. Understanding and improving <span class="hlt">MODIS</span> retrievals over the East Coast will not only improve the global quality of <span class="hlt">MODIS</span>, but also would enable the use of <span class="hlt">MODIS</span> as a tool for monitoring regional aerosol events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004SPIE.5542...14B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004SPIE.5542...14B"><span id="translatedtitle"><span class="hlt">MODIS</span> instrument status and operational activities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barnes, William L.; Xiong, Xiaoxiong; Salomonson, Vincent V.</p> <p>2004-10-01</p> <p>The Terra <span class="hlt">MODIS</span> and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> have been successfully operated on-orbit for a total of more than six and a half years, collecting data for the science and applications communities to develop and enhance their understanding of the Earth/atmosphere system and to support studies of the climate and climate changes. Since its launch in December 1999, the Terra <span class="hlt">MODIS</span> has experienced several changes of its operational configuration either caused by the failure of individual electronics subsystems or purposely switched for better signal response or data quality. Excluding minor anomalies related to instrument reset events during initial on-orbit operation, the <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> has been operating in a single configuration since its launch in May 2002. There are approximately 40 science products that are being produced using the calibrated data sets from each instrument. In addition, several products are generated using the combined observations from both instruments. This paper provides an overview of Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> instrument status and summarizes those on-orbit operational activities designed and implemented to provide and support instrument calibration and characterization. The assessments of instrument performance are based on the use of on-board calibrators (OBC) and other activities specially developed and implemented by the <span class="hlt">MODIS</span> Characterization Support Team (MCST) at NASA/GSFC. Both instruments are performing well. During four and a half years of Terra <span class="hlt">MODIS</span> on-orbit operation, 11 detectors became noisy and one inoperable out of a total of 490 detectors. Except for band 6 at 1.6m that had many inoperable detectors (identified pre-launch and immediately after launch), there have been no new noisy or inoperable detectors in <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> during its two years of on-orbit operation. The sensors' spectral and spatial performance have also been very stable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SPIE.9607E..1ZX','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SPIE.9607E..1ZX"><span id="translatedtitle">Calibration improvements for <span class="hlt">MODIS</span> and VIIRS SWIR spectral bands</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiong, Xiaoxiong; Angal, Amit; Fulbright, Jon; Lei, Ning; Mu, Qiaozhen; Wang, Zhipeng; Wu, Aisheng</p> <p>2015-09-01</p> <p>Both <span class="hlt">MODIS</span> and VIIRS use a solar diffuser (SD) to calibrate their <span class="hlt">reflective</span> solar bands (RSB), covering wavelengths from 0.41 to 2.3 μm. On-orbit changes of the SD bi-directional <span class="hlt">reflectance</span> factor (BRF) are tracked by an on-board solar diffuser stability monitor (SDSM). The current SDSM design only covers the spectral range from 0.41 to 0.93 μm. In general, the SD degradation is strongly wavelength-dependent with larger degradation occurring at shorter wavelengths, and the degradation in the SWIR region is expected to be extremely small. As each mission continues, however, the impact due to SD degradation at SWIR needs to be carefully examined and the correction if necessary should be applied in order to maintain the calibration quality. For Terra <span class="hlt">MODIS</span>, alternative approaches have been developed and used to estimate the SD degradation for its band 5 at 1.24 μm and a time-dependent correction has already been applied to the current level 1B (L1B) collection 6 (C6). In this paper, we present different methodologies that can be used to examine the SD degradation and their applications for both Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> and S-NPP VIIRS SWIR calibration. These methodologies include but not limited to the use of lunar observations, Pseudo Invariant Calibration Sites (PICS), and deep convective clouds (DCC). A brief description of relative approaches and their use is also provided in this paper.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AGUFM.A33M0338G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AGUFM.A33M0338G&link_type=ABSTRACT"><span id="translatedtitle">Operationalizing a Research Sensor: <span class="hlt">MODIS</span> to VIIRS</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grant, K. D.; Miller, S. W.; Puschell, J.</p> <p>2012-12-01</p> <p>The National Oceanic and Atmospheric Administration (NOAA) and NASA are jointly acquiring the next-generation civilian environmental satellite system: the Joint Polar Satellite System (JPSS). JPSS will replace the afternoon orbit component and ground processing system of the current Polar-orbiting Operational Environmental Satellites (POES) managed by NOAA. The JPSS satellite will carry a suite of sensors designed to collect meteorological, oceanographic, climatological, and solar-geophysical observations of the earth, atmosphere, and space. The primary sensor for the JPSS mission is the Visible/Infrared Imager Radiometer Suite (VIIRS) developed by Raytheon Space and Airborne Systems (SAS). The ground processing system for the JPSS mission is known as the Common Ground System (JPSS CGS), and consists of a Command, Control, and Communications Segment (C3S) and the Interface Data Processing Segment (IDPS) which are both developed by Raytheon Intelligence and Information Systems (IIS). The Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) was developed by Raytheon SAS for the NASA Earth Observing System (EOS) as a research instrument to capture data in 36 spectral bands, ranging in wavelength from 0.4 μm to 14.4 μm and at varying spatial resolutions (2 bands at 250 m, 5 bands at 500 m and 29 bands at 1 km). <span class="hlt">MODIS</span> data provides unprecedented insight into large-scale Earth system science questions related to cloud and aerosol characteristics, surface emissivity and processes occurring in the oceans, on land, and in the lower atmosphere. <span class="hlt">MODIS</span> has flown on the EOS Terra satellite since 1999 and on the EOS <span class="hlt">Aqua</span> satellite since 2002 and provided excellent data for scientific research and operational use for more than a decade. The value of <span class="hlt">MODIS</span>-derived products for operational environmental monitoring motivated led to the development of an operational counterpart to <span class="hlt">MODIS</span> for the next-generation polar-orbiting environmental satellites, the Visible/Infrared Imager</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20030020719&hterms=classification+ecosystems&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dclassification%2Becosystems','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20030020719&hterms=classification+ecosystems&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dclassification%2Becosystems"><span id="translatedtitle">Remote Sensing of Cloud, Aerosol, and Land Properties from <span class="hlt">MODIS</span>: Applications to the East Asia Region</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>King, Michael D.; Platnick, Steven; Moody, Eric G.</p> <p>2002-01-01</p> <p><span class="hlt">MODIS</span> is an earth-viewing cross-track scanning spectroradiometer launched on the Terra satellite in December 1999 and the <span class="hlt">Aqua</span> satellite in May 2002. <span class="hlt">MODIS</span> scans a swath width sufficient to provide nearly complete global coverage every two days from a polar-orbiting, sun-synchronous, platform at an altitude of 705 km, and provides images in 36 spectral bands between 0.415 and 14.235 microns with spatial resolutions of 250 m (2 bands), 500 m (5 bands) and 1000 m (29 bands). These bands have been carefully selected to enable advanced studies of land, ocean, and atmospheric processes. In this paper we will describe the various methods being used for the remote sensing of cloud, aerosol, and surface properties using <span class="hlt">MODIS</span> data, focusing primarily on (i) the <span class="hlt">MODIS</span> cloud mask used to distinguish clouds, clear sky, heavy aerosol, and shadows on the ground, (ii) cloud optical properties, especially cloud optical thickness and effective radius of water drops and ice crystals, (iii) aerosol optical thickness and size characteristics both over land and ocean, and (iv) ecosystem classification and surface spectral <span class="hlt">reflectance</span>. The physical principles behind the determination of each of these products will be described, together with an example of their application using <span class="hlt">MODIS</span> observations to the east Asian region. All products are archived into two categories: pixel-level retrievals (referred to as Level-2 products) and global gridded products at a latitude and longitude resolution of 1 min (Level-3 products).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.B33L..07D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.B33L..07D"><span id="translatedtitle">Identifying crop specific signals for global agricultural monitoring based on the stability of daily multi-angular <span class="hlt">MODIS</span> <span class="hlt">reflectance</span> time series</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Duveiller, G.; Lopez-Lozano, R.</p> <p>2013-12-01</p> <p>Global agricultural monitoring requires satellite Earth Observation systems that maximize the observation revisit frequency over the largest possible geographical coverage. Such compromise has thus far resulted in using a spatial resolution that is often coarser than desired. As a consequence, for many agricultural landscapes across the world, crop status can only be inferred from a mixed signal of the landscape (with a pixel size typically close to 1 km), composed of <span class="hlt">reflectance</span> from neighbouring fields with potentially different crops, variable phenological behaviours and distinct management practices. <span class="hlt">MODIS</span> has been providing, since 2000, a higher spatial resolution (~250m) that is closer to the size of individual fields in many agro-ecological landscapes. However, the challenge for operational crop specific monitoring remains to identify in time where a given crop has been sown during the current growing season. An innovative use of <span class="hlt">MODIS</span> daily data is proposed for crop identification based on the stability of the multi-angular signal. <span class="hlt">MODIS</span> is a whiskbroom sensor with a large swath. For any given place, consecutive <span class="hlt">MODIS</span> observations are made with considerably different viewing angles according to the daily change in orbit. Consequently, the footprint of the observation varies considerably, thereby sampling the vicinity around the centre of the grid cell in which the time series is ultimately recorded in. If the consecutive observations that have sampled the vicinity provide similar NDVI values (for which BRDF effects are reduced), the resulting temporal signal is relatively stable. This stability indicated that the signal comes from a spatially homogeneous surface, such as a single large field covered by the same crop with similar agro-management practices. If the resulting temporal signal is noisy, it is probable that the consecutive daily observations have sampled different land uses, thus contaminating the signal. Such time series can therefore be</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.usgs.gov/fs/2008/3061/','USGSPUBS'); return false;" href="http://pubs.usgs.gov/fs/2008/3061/"><span id="translatedtitle">Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) Overview</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>U.S. Geological Survey</p> <p>2008-01-01</p> <p>The Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) is an instrument that collects remotely sensed data used by scientists for monitoring, modeling, and assessing the effects of natural processes and human actions on the Earth's surface. The continual calibration of the <span class="hlt">MODIS</span> instruments, the refinement of algorithms used to create higher-level products, and the ongoing product validation make <span class="hlt">MODIS</span> images a valuable time series (2000-present) of geophysical and biophysical land-surface measurements. Carried on two National Aeronautics and Space Administration (NASA) Earth Observing System (EOS) satellites, <span class="hlt">MODIS</span> acquires morning (EOS-Terra) and afternoon (EOS-<span class="hlt">Aqua</span>) views almost daily. Terra data acquisitions began in February 2000 and <span class="hlt">Aqua</span> data acquisitions began in July 2002. Land data are generated only as higher-level products, removing the burden of common types of data processing from the user community. <span class="hlt">MODIS</span>-based products describing ecological dynamics, radiation budget, and land cover are projected onto a sinusoidal mapping grid and distributed as 10- by 10-degree tiles at 250-, 500-, or 1,000-meter spatial resolution. Some products are also created on a 0.05-degree geographic grid to support climate modeling studies. All <span class="hlt">MODIS</span> products are distributed in the Hierarchical Data Format-Earth Observing System (HDF-EOS) file format and are available through file transfer protocol (FTP) or on digital video disc (DVD) media. Versions 4 and 5 of <span class="hlt">MODIS</span> land data products are currently available and represent 'validated' collections defined in stages of accuracy that are based on the number of field sites and time periods for which the products have been validated. Version 5 collections incorporate the longest time series of both Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> data products.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110007087','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110007087"><span id="translatedtitle">Trends in <span class="hlt">MODIS</span> Geolocation Error Analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wolfe, R. E.; Nishihama, Masahiro</p> <p>2009-01-01</p> <p>Data from the two <span class="hlt">MODIS</span> instruments have been accurately geolocated (Earth located) to enable retrieval of global geophysical parameters. The authors describe the approach used to geolocate with sub-pixel accuracy over nine years of data from M0DIS on NASA's E0S Terra spacecraft and seven years of data from <span class="hlt">MODIS</span> on the <span class="hlt">Aqua</span> spacecraft. The approach uses a geometric model of the <span class="hlt">MODIS</span> instruments, accurate navigation (orbit and attitude) data and an accurate Earth terrain model to compute the location of each <span class="hlt">MODIS</span> pixel. The error analysis approach automatically matches <span class="hlt">MODIS</span> imagery with a global set of over 1,000 ground control points from the finer-resolution Landsat satellite to measure static biases and trends in the MO0lS geometric model parameters. Both within orbit and yearly thermally induced cyclic variations in the pointing have been found as well as a general long-term trend.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.H32B..04U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.H32B..04U"><span id="translatedtitle">The <span class="hlt">MODIS</span> Vegetation Canopy Water Content product</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ustin, S. L.; Riano, D.; Trombetti, M.</p> <p>2008-12-01</p> <p>Vegetation water stress drives wildfire behavior and risk, having important implications for biogeochemical cycling in natural ecosystems, agriculture, and forestry. Water stress limits plant transpiration and carbon gain. The regulation of photosynthesis creates close linkages between the carbon, water, and energy cycles and through metabolism to the nitrogen cycle. We generated systematic weekly CWC estimated for the USA from 2000-2006. <span class="hlt">MODIS</span> measures the sunlit <span class="hlt">reflectance</span> of the vegetation in the visible, near-infrared, and shortwave infrared. Radiative transfer models, such as PROSPECT-SAILH, determine how sunlight interacts with plant and soil materials. These models can be applied over a range of scales and ecosystem types. Artificial Neural Networks (ANN) were used to optimize the inversion of these models to determine vegetation water content. We carried out multi-scale validation of the product using field data, airborne and satellite cross-calibration. An Algorithm Theoretical Basis Document (ATBD) of the product is under evaluation by NASA. The CWC product inputs are 1) The <span class="hlt">MODIS</span> Terra/<span class="hlt">Aqua</span> surface <span class="hlt">reflectance</span> product (MOD09A1/MYD09A1) 2) The <span class="hlt">MODIS</span> land cover map product (MOD12Q1) reclassified to grassland, shrub-land and forest canopies; 3) An ANN trained with PROSPECT-SAILH; 4) A calibration file for each land cover type. The output is an ENVI file with the CWC values. The code is written in Matlab environment and is being adapted to read not only the 8 day <span class="hlt">MODIS</span> composites, but also daily surface <span class="hlt">reflectance</span> data. We plan to incorporate the cloud and snow mask and generate as output a geotiff file. Vegetation water content estimates will help predicting linkages between biogeochemical cycles, which will enable further understanding of feedbacks to atmospheric concentrations of greenhouse gases. It will also serve to estimate primary productivity of the biosphere; monitor/assess natural vegetation health related to drought, pollution or diseases</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110006383','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110006383"><span id="translatedtitle">On-Orbit Operation and Performance of <span class="hlt">MODIS</span> Blackbody</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Xiong, X.; Chang, T.; Barnes, W.</p> <p>2009-01-01</p> <p><span class="hlt">MODIS</span> collects data in 36 spectral bands, including 20 <span class="hlt">reflective</span> solar bands (RSB) and 16 thermal emissive bands (TES). The TEB on-orbit calibration is performed on a scan-by-scan basis using a quadratic algorithm that relates the detector response with the calibration radiance from the sensor on-board blackbody (BB). The calibration radiance is accurately determined each scan from the BB temperature measured using a set of 12 thermistors. The BB thermistors were calibrated pre-launch with traceability to the NIST temperature standard. Unlike many heritage sensors, the <span class="hlt">MODIS</span> BB can be operated at a constant temperature or with the temperature continuously varying between instrument ambient (about 270K) and 315K. In this paper, we provide an overview of both Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> on-board BB operations, functions, and on-orbit performance. We also examine the impact of key calibration parameters, such as BB emissivity and temperature (stability and gradient) determined from its thermistors, on the TEB calibration and Level I (LIB) data product uncertainty.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.B41D0430W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.B41D0430W"><span id="translatedtitle">Improvements to the <span class="hlt">MODIS</span> Land Products in Collection Version 6</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wolfe, R. E.; Devadiga, S.; Masuoka, E. J.; Running, S. W.; Vermote, E.; Giglio, L.; Wan, Z.; Riggs, G. A.; Schaaf, C.; Myneni, R. B.; Friedl, M. A.; Wang, Z.; Sulla-menashe, D. J.; Zhao, M.</p> <p>2013-12-01</p> <p>The <span class="hlt">MODIS</span> (Moderate Resolution Imaging Spectroradiometer) Adaptive Processing System (MODAPS), housed at the NASA Goddard Space Flight Center (GSFC), has been processing the earth view data acquired by the <span class="hlt">MODIS</span> instrument aboard the Terra (EOS AM) and <span class="hlt">Aqua</span> (EOS PM) satellites to generate suite of land and atmosphere data products using the science algorithms developed by the <span class="hlt">MODIS</span> Science Team. These data products are used by diverse set of users in research and other applications from both government and non-government agencies around the world. These validated global products are also being used in interactive Earth system models able to predict global change accurately enough to assist policy makers in making sound decisions concerning the protection of our environment. Hence an increased emphasis is being placed on generation of high quality consistent data records from the <span class="hlt">MODIS</span> data through reprocessing of the records using improved science algorithms. Since the launch of Terra in December 1999, <span class="hlt">MODIS</span> land data records have been reprocessed four times. The Collection Version 6 (C6) reprocessing of <span class="hlt">MODIS</span> Land and Atmosphere products is scheduled to start in Fall 2013 and is expected to complete in Spring 2014. This presentation will describe changes made to the C6 science algorithms to correct issues in the C5 products, additional improvements made to the products as deemed necessary by the data users and science teams, and new products introduced in this reprocessing. In addition to the improvements from product specific changes to algorithms, the C6 products will also see significant improvement in the calibration by the <span class="hlt">MODIS</span> Calibration Science Team (MCST) of the C6 L1B Top of the Atmosphere (TOA) <span class="hlt">reflectance</span> and radiance product, more accurate geolocation, and an improved Land Water mask. For the a priori land cover input, this reprocessing will use the multi-year land cover product generated with three years of <span class="hlt">MODIS</span> data as input as opposed to one</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20060047447','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20060047447"><span id="translatedtitle">Status of the <span class="hlt">MODIS</span> Level 1B Algorithms and Calibration Tables</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Xiong, X; Salomonson, V V; Kuyper, J; Tan, L; Chiang, K; Sun, J; Barnes, W L</p> <p>2005-01-01</p> <p>The Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) makes observations using 36 spectral bands with wavelengths from 0.41 to 14.4 m and nadir spatial resolutions of 0.25km, 0.5km, and 1km. It is currently operating onboard the NASA Earth Observing System (EOS) Terra and <span class="hlt">Aqua</span> satellites, launched in December 1999 and May 2002, respectively. The <span class="hlt">MODIS</span> Level 1B (L1B) program converts the sensor's on-orbit responses in digital numbers to radiometrically calibrated and geo-located data products for the duration of each mission. Its primary data products are top of the atmosphere (TOA) <span class="hlt">reflectance</span> factors for the sensor's <span class="hlt">reflective</span> solar bands (RSB) and TOA spectral radiances for the thermal emissive bands (TEB). The L1B algorithms perform the TEB calibration on a scan-by-scan basis using the sensor's response to the on-board blackbody (BB) and other parameters which are stored in Lookup Tables (LUTs). The RSB calibration coefficients are processed offline and regularly updated through LUTs. In this paper we provide a brief description of the <span class="hlt">MODIS</span> L1B calibration algorithms and associated LUTs with emphasis on their recent improvements and updates developed for the <span class="hlt">MODIS</span> collection 5 processing. We will also discuss sensor on-orbit calibration and performance issues that are critical to maintaining L1B data product quality, such as changes in the sensor's response versus scan-angle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRD..121.4783C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRD..121.4783C"><span id="translatedtitle">Assessment of <span class="hlt">MODIS</span> RSB detector uniformity using deep convective clouds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chang, Tiejun; Xiong, Xiaoxiong (Jack); Angal, Amit; Mu, Qiaozhen</p> <p>2016-05-01</p> <p>For satellite sensor, the striping observed in images is typically associated with the relative multiple detector gain difference derived from the calibration. A method using deep convective cloud (DCC) measurements to assess the difference among detectors after calibration is proposed and demonstrated for select <span class="hlt">reflective</span> solar bands (RSBs) of the Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>). Each detector of <span class="hlt">MODIS</span> RSB is calibrated independently using a solar diffuser (SD). Although the SD is expected to accurately characterize detector response, the uncertainties associated with the SD degradation and characterization result in inadequacies in the estimation of each detector's gain. This work takes advantage of the DCC technique to assess detector uniformity and scan mirror side difference for RSB. The detector differences for Terra <span class="hlt">MODIS</span> Collection 6 are less than 1% for bands 1, 3-5, and 18 and up to 2% for bands 6, 19, and 26. The largest difference is up to 4% for band 7. Most <span class="hlt">Aqua</span> bands have detector differences less than 0.5% except bands 19 and 26 with up to 1.5%. Normally, large differences occur for edge detectors. The long-term trending shows seasonal oscillations in detector differences for some bands, which are correlated with the instrument temperature. The detector uniformities were evaluated for both unaggregated and aggregated detectors for <span class="hlt">MODIS</span> band 1 and bands 3-7, and their consistencies are verified. The assessment results were validated by applying a direct correction to <span class="hlt">reflectance</span> images. These assessments can lead to improvements to the calibration algorithm and therefore a reduction in striping observed in the calibrated imagery.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20160007849&hterms=clouds&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dclouds','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20160007849&hterms=clouds&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dclouds"><span id="translatedtitle">Assessment of <span class="hlt">MODIS</span> RSB Detector Uniformity Using Deep Convective Clouds</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chang, Tiejun; Xiong, Xiaoxiong (Jack); Angal, Amit; Mu, Qiaozhen</p> <p>2016-01-01</p> <p>For satellite sensor, the striping observed in images is typically associated with the relative multiple detector gain difference derived from the calibration. A method using deep convective cloud (DCC) measurements to assess the difference among detectors after calibration is proposed and demonstrated for select <span class="hlt">reflective</span> solar bands (RSBs) of the Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>). Each detector of <span class="hlt">MODIS</span> RSB is calibrated independently using a solar diffuser (SD). Although the SD is expected to accurately characterize detector response, the uncertainties associated with the SD degradation and characterization result in inadequacies in the estimation of each detector's gain. This work takes advantage of the DCC technique to assess detector uniformity and scan mirror side difference for RSB. The detector differences for Terra <span class="hlt">MODIS</span> Collection 6 are less than 1% for bands 1, 3-5, and 18 and up to 2% for bands 6, 19, and 26. The largest difference is up to 4% for band 7. Most <span class="hlt">Aqua</span> bands have detector differences less than 0.5% except bands 19 and 26 with up to 1.5%. Normally, large differences occur for edge detectors. The long-term trending shows seasonal oscillations in detector differences for some bands, which are correlated with the instrument temperature. The detector uniformities were evaluated for both unaggregated and aggregated detectors for <span class="hlt">MODIS</span> band 1 and bands 3-7, and their consistencies are verified. The assessment results were validated by applying a direct correction to <span class="hlt">reflectance</span> images. These assessments can lead to improvements to the calibration algorithm and therefore a reduction in striping observed in the calibrated imagery.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2171368','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2171368"><span id="translatedtitle">Global Data for Ecology and Epidemiology: A Novel Algorithm for Temporal Fourier Processing <span class="hlt">MODIS</span> Data</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Scharlemann, Jörn P. W.; Benz, David; Hay, Simon I.; Purse, Bethan V.; Tatem, Andrew J.; Wint, G. R. William; Rogers, David J.</p> <p>2008-01-01</p> <p>Background Remotely-sensed environmental data from earth-orbiting satellites are increasingly used to model the distribution and abundance of both plant and animal species, especially those of economic or conservation importance. Time series of data from the MODerate-resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) sensors on-board NASA's Terra and <span class="hlt">Aqua</span> satellites offer the potential to capture environmental thermal and vegetation seasonality, through temporal Fourier analysis, more accurately than was previously possible using the NOAA Advanced Very High Resolution Radiometer (AVHRR) sensor data. <span class="hlt">MODIS</span> data are composited over 8- or 16-day time intervals that pose unique problems for temporal Fourier analysis. Applying standard techniques to <span class="hlt">MODIS</span> data can introduce errors of up to 30% in the estimation of the amplitudes and phases of the Fourier harmonics. Methodology/Principal Findings We present a novel spline-based algorithm that overcomes the processing problems of composited <span class="hlt">MODIS</span> data. The algorithm is tested on artificial data generated using randomly selected values of both amplitudes and phases, and provides an accurate estimate of the input variables under all conditions. The algorithm was then applied to produce layers that capture the seasonality in <span class="hlt">MODIS</span> data for the period from 2001 to 2005. Conclusions/Significance Global temporal Fourier processed images of 1 km <span class="hlt">MODIS</span> data for Middle Infrared <span class="hlt">Reflectance</span>, day- and night-time Land Surface Temperature (LST), Normalised Difference Vegetation Index (NDVI), and Enhanced Vegetation Index (EVI) are presented for ecological and epidemiological applications. The finer spatial and temporal resolution, combined with the greater geolocational and spectral accuracy of the <span class="hlt">MODIS</span> instruments, compared with previous multi-temporal data sets, mean that these data may be used with greater confidence in species' distribution modelling. PMID:18183289</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011AGUFM.U41B0013G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011AGUFM.U41B0013G&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Aqua</span> Education and Public Outreach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Graham, S. M.; Parkinson, C. L.; Chambers, L. H.; Ray, S. E.</p> <p>2011-12-01</p> <p>NASA's <span class="hlt">Aqua</span> satellite was launched on May 4, 2002, with six instruments designed to collect data about the Earth's atmosphere, biosphere, hydrosphere, and cryosphere. Since the late 1990s, the <span class="hlt">Aqua</span> mission has involved considerable education and public outreach (EPO) activities, including printed products, formal education, an engineering competition, webcasts, and high-profile multimedia efforts. The printed products include <span class="hlt">Aqua</span> and instrument brochures, an <span class="hlt">Aqua</span> lithograph, <span class="hlt">Aqua</span> trading cards, NASA Fact Sheets on <span class="hlt">Aqua</span>, the water cycle, and weather forecasting, and an <span class="hlt">Aqua</span> science writers' guide. On-going formal education efforts include the Students' Cloud Observations On-Line (S'COOL) Project, the MY NASA DATA Project, the Earth System Science Education Alliance, and, in partnership with university professors, undergraduate student research modules. Each of these projects incorporates <span class="hlt">Aqua</span> data into its inquiry-based framework. Additionally, high school and undergraduate students have participated in summer internship programs. An earlier formal education activity was the <span class="hlt">Aqua</span> Engineering Competition, which was a high school program sponsored by the NASA Goddard Space Flight Center, Morgan State University, and the Baltimore Museum of Industry. The competition began with the posting of a Round 1 <span class="hlt">Aqua</span>-related engineering problem in December 2002 and concluded in April 2003 with a final round of competition among the five finalist teams. The <span class="hlt">Aqua</span> EPO efforts have also included a wide range of multimedia products. Prior to launch, the <span class="hlt">Aqua</span> team worked closely with the Special Projects Initiative (SPI) Office to produce a series of live webcasts on <span class="hlt">Aqua</span> science and the Cool Science website <span class="hlt">aqua</span>.nasa.gov/coolscience, which displays short video clips of <span class="hlt">Aqua</span> scientists and engineers explaining the many aspects of the <span class="hlt">Aqua</span> mission. These video clips, the <span class="hlt">Aqua</span> website, and numerous presentations have benefited from dynamic visualizations showing the <span class="hlt">Aqua</span> launch</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009GeoRL..36.9811L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009GeoRL..36.9811L"><span id="translatedtitle">View-angle consistency in <span class="hlt">reflectance</span>, optical thickness and spherical albedo of marine water-clouds over the northeastern Pacific through MISR-<span class="hlt">MODIS</span> fusion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liang, Lusheng; Di Girolamo, Larry; Platnick, Steven</p> <p>2009-05-01</p> <p>View-angle consistency in bidirectional <span class="hlt">reflectance</span> factor (BRF), optical thickness and spherical albedo is examined for marine water clouds over a region of the northeastern Pacific using six years of fused Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) and Multiangle Imaging SpectroRadiometer (MISR) data. Consistency is quantified by the root-mean-square of relative differences between MISR-measured BRF and their plane-parallel values and variation of plane-parallel retrieved optical thickness and spherical albedo across multiple view-angles. Probability distribution functions of consistency show that, for example, these clouds are angularly consistent within 5% in BRF, optical thickness and spherical albedo 72.2%, 39.0% and 81.1% of the time, respectively. We relate angular consistency to the spatial variability of nadir-BRF, thus allowing us to potentially identify, with a prescribed confidence level, which <span class="hlt">MODIS</span> microphysical retrievals within the MISR swath meet the plane-parallel assumption to within any desired range in view-angle consistency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008SPIE.7081E..0CX','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008SPIE.7081E..0CX"><span id="translatedtitle">Characterization of <span class="hlt">MODIS</span> VIS/NIR spectral band detector-to-detector differences</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiong, X.; Sun, J.; Meister, G.; Kwiatkowska, E.; Barnes, W. L.</p> <p>2008-08-01</p> <p><span class="hlt">MODIS</span> has 36 spectral bands with wavelengths in the visible (VIS), near-infrared (NIR), short-wave infrared (SWIR), mid-wave infrared (MWIR), and long-wave infrared (LWIR). It makes observations at three nadir spatial resolutions: 0.25km for bands 1-2 (40 detectors per band), 0.5km for bands 3-7 (20 detectors per band), and 1km for bands 8-36 (10 detectors per band). The VIS, NIR, and SWIR are the <span class="hlt">reflective</span> solar bands (RSB), which are calibrated on-orbit by a solar diffuser (SD) and a solar diffuser stability monitor (SDSM). The bi-directional <span class="hlt">reflectance</span> factor (BRF) of the SD provides a RSB calibration reference and its on-orbit changes are tracked by the SDSM. In addition, <span class="hlt">MODIS</span> lunar observations are regularly scheduled and used to track the RSB calibration stability. On-orbit observations show that the changes in detector response are wavelength and scan angle dependent. In this study, we focus on detector-to-detector calibration differences in the <span class="hlt">MODIS</span> VIS/NIR spectral bands, which are determined using SD and lunar observations, while the calibration performance is evaluated using the Earth view (EV) level 1B (L1B) data products. For <span class="hlt">Aqua</span> <span class="hlt">MODIS</span>, the detector calibration differences and their impact are also characterized using standard ocean color data products. The current calibration approach for <span class="hlt">MODIS</span> RSB carries a band-averaged response versus scan angle (RVS) correction. The results from this study suggest that a detector-based RVS correction should, due to changes in the scan mirror's optical properties, be implemented in order to maintain and improve the current RSB L1B data product quality, particularly, for several VIS bands in Terra <span class="hlt">MODIS</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.A33C0251J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.A33C0251J"><span id="translatedtitle">Investigating Correlations Between Satellite-Derived Aerosol Optical Depth And Ground PM2.5 Measurements in Californias San Joaquin Valley with <span class="hlt">MODIS</span> Deep Blue</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Justice, E.; Huston, L.; Krauth, D.; Mack, J.; Oza, S.; Strawa, A.; Legg, M.; Schmidt, C.; Skiles, J.</p> <p>2008-12-01</p> <p>Air quality in the San Joaquin Valley has failed to meet state and federal particulate matter (PM) attainment standards for the past several years. Air quality agencies currently use ground sensors to monitor the region's air. While this method provides accurate information at specific locations, it does not provide a clear indication of conditions over large regions. Measurements from satellite imagery have the potential to provide timely air quality data for large swaths of land. While previous studies show strong correlations between <span class="hlt">MODIS</span>-derived Aerosol Optical Depth (AOD) and surface PM measurements on the East Coast of the United States, only weak correlations have been found in the West. Specific causes of this discrepancy have not been identified, nor has a solution been found. This study compares hourly and daily surface PM measurements to both traditional and Deep Blue-derived <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> AOD data. Deep Blue is a newly developed algorithm that was recently applied to all <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> data. Additionally, we analyzed the effects of relative humidity, surface <span class="hlt">reflectance</span>, and aerosol vertical distribution, from CALIPSO's CALIOP sensor, on differences in PM and AOD measurements. Results show hourly PM2.5 data improved correlations with satellite AOD values. Also PM2.5 data, corresponding to sites in Bakersfield and Fresno, correlate better with Deep Blue-derived AOD values than with traditional <span class="hlt">MODIS</span> AOD. Further investigation into the affects of seasonal variation, particle distribution and speciation is needed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMIN11B3609R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMIN11B3609R"><span id="translatedtitle">Protocol for Validation of the Land Surface <span class="hlt">Reflectance</span> Fundamental Climate Data Record using AERONET: Application to the Global <span class="hlt">MODIS</span> and VIIRS Data Records</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Roger, J. C.; Vermote, E.; Holben, B. N.</p> <p>2014-12-01</p> <p>The land surface <span class="hlt">reflectance</span> is a fundamental climate data record at the basis of the derivation of other climate data records (Albedo, LAI/Fpar, Vegetation indices) and a key parameter in the understanding of the land-surface-climate processes. It is essential that a careful validation of its uncertainties is performed on a global and continuous basis. One approach is the direct comparison of this product with ground measurements but that approach presents several issues related to scale, the episodic nature of ground measurements and the global representativeness. An alternative is to compare the surface <span class="hlt">reflectance</span> product to reference <span class="hlt">reflectance</span> determined from Top of atmosphere <span class="hlt">reflectance</span> corrected using accurate radiative transfer code and very detailed measurements of the atmosphere obtained over the AERONET sites (Vermote and al, 2014, RSE) which allows to test for a large range of aerosol characteristics; formers being important inputs for atmospheric corrections. However, the application of this method necessitates the definition of a very detailed protocol for the use of AERONET data especially as far as size distribution and absorption are concerned, so that alternative validation methods or protocols could be compared. This paper describes the protocol we have been working on based on our experience with the AERONET data and its application to the <span class="hlt">MODIS</span> and VIIRS record.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003SPIE.5151..375X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003SPIE.5151..375X"><span id="translatedtitle">On-orbit characterization of a solar diffuser"s bidirectional <span class="hlt">reflectance</span> factor using spacecraft maneuvers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiong, Xiaoxiong; Sun, Junqiang; Esposito, Joe; Liu, Xiaojin; Barnes, William L.; Guenther, B.</p> <p>2003-11-01</p> <p>The MODerate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) uses an on-board solar diffuser (SD) panel made of Spectralon for the radiometric calibration of its 20 <span class="hlt">reflective</span> solar bands (RSB). The spectral wavelengths of the RSB range from 0.41 to 2.1 micrometers. The on-orbit calibration coefficients are determined from the sensor s responses to the diffusely <span class="hlt">reflected</span> solar illumination from the SD. This method requires an accurate pre-launch characterization of solar diffuser s bi-directional <span class="hlt">reflectance</span> factors (BRF) that should cover the sensor s spectral range and illumination/viewing angles and accurate on-orbit monitoring of SD degradation over time. The <span class="hlt">MODIS</span> SD panel s bi-directional <span class="hlt">reflectance</span> factors were characterized prior to the sensor s final system integration (pre-launch by the instrument vendor using reference samples traceable to the NIST <span class="hlt">reflectance</span> standards at a number of wavelengths and carefully selected combinations of the illumination/viewing angles. The measured BRF values were fitted into smooth surfaces and then interpolated for each of the <span class="hlt">MODIS</span> <span class="hlt">reflective</span> solar bands. In this paper, we describe an approach designed for the <span class="hlt">MODIS</span> on-orbit characterization and validation of its SD BRF using multiple SD solar observations at several spacecraft yaw angels. This approach has been successfully applied to both the Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span>. This paper presents the algorithm used to derive the SD s relative BRF from observations during spacecraft yaws and compares the on-orbit results with corresponding pre-launch values.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100020840','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100020840"><span id="translatedtitle"><span class="hlt">MODIS</span> On-Board Blackbody Function and Performance</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Xiaoxiong, Xiong; Wenny, Brian N.; Wu, Aisheng; Barnes, William</p> <p>2009-01-01</p> <p>Two <span class="hlt">MODIS</span> instruments are currently in orbit, making continuous global observations in visible to long-wave infrared wavelengths. Compared to heritage sensors, <span class="hlt">MODIS</span> was built with an advanced set of on-board calibrators, providing sensor radiometric, spectral, and spatial calibration and characterization during on-orbit operation. For the thermal emissive bands (TEB) with wavelengths from 3.7 m to 14.4 m, a v-grooved blackbody (BB) is used as the primary calibration source. The BB temperature is accurately measured each scan (1.47s) using a set of 12 temperature sensors traceable to NIST temperature standards. The onboard BB is nominally operated at a fixed temperature, 290K for Terra <span class="hlt">MODIS</span> and 285K for <span class="hlt">Aqua</span> <span class="hlt">MODIS</span>, to compute the TEB linear calibration coefficients. Periodically, its temperature is varied from 270K (instrument ambient) to 315K in order to evaluate and update the nonlinear calibration coefficients. This paper describes <span class="hlt">MODIS</span> on-board BB functions with emphasis on on-orbit operation and performance. It examines the BB temperature uncertainties under different operational conditions and their impact on TEB calibration and data product quality. The temperature uniformity of the BB is also evaluated using TEB detector responses at different operating temperatures. On-orbit results demonstrate excellent short-term and long-term stability for both the Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> on-board BB. The on-orbit BB temperature uncertainty is estimated to be 10mK for Terra <span class="hlt">MODIS</span> at 290K and 5mK for <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> at 285K, thus meeting the TEB design specifications. In addition, there has been no measurable BB temperature drift over the entire mission of both Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.3132T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.3132T"><span id="translatedtitle">Using <span class="hlt">MODIS</span> data to estimate river discharge in ungauged sites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tarpanelli, A.; Brocca, L.; Lacava, T.; Faruolo, M.; Melone, F.; Moramarco, T.; Pergola, N.; Tramutoli, V.</p> <p>2012-04-01</p> <p>The discharge prediction at a river site is fundamental for water resources management and flood risk prevention. An accurate discharge estimation depends on local hydraulic conditions which are usually detected by recording water level and carrying out flow measurements, which are costly and sometimes impractical for high flows. Over the last decade, the possibility to obtain river discharge estimates from satellite sensors data has become of considerable interest. For large river basins, the use of satellite data derived by altimeter and microwave sensors, characterized by a daily temporal resolution, has proven to be a useful tool to integrate or even increase the discharge monitoring. For smaller basins, Synthetic Aperture Radars (SARs) have been usually employed for the indirect estimation of water elevation but their low temporal resolution (from a few days up to 30 days) might be considered not suitable for discharge prediction. The Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) aboard of Terra and <span class="hlt">Aqua</span> Earth Observing System (EOS) satellites, can provide a proper tradeoff between temporal and spatial resolution useful for discharge estimation. It assures, in fact, at least a daily temporal resolution and a spatial resolution up to 250 m in the first two channels. In this study, the capability of <span class="hlt">MODIS</span> data for discharge prediction is investigated. Specifically, the different spectral behavior of water and land in the Near Infrared (NIR) portion of the electromagnetic spectrum (<span class="hlt">MODIS</span> channel 2) is exploited by computing the ratio of the <span class="hlt">MODIS</span> channel 2 <span class="hlt">reflectance</span> values between two pixels located within and outside the river. Values of such a ratio should increase when more water and, hence, discharge, is present. Time series of daily water level, velocity and discharge between 2002 and 2010 measured at different gauging stations located along the Upper Tiber River (central Italy) and the Po River (North Italy), as well as <span class="hlt">MODIS</span> channel 2 data for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080023286','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080023286"><span id="translatedtitle"><span class="hlt">MODIS</span> Land Data Products: Generation, Quality Assurance and Validation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Masuoka, Edward; Wolfe, Robert; Morisette, Jeffery; Sinno, Scott; Teague, Michael; Saleous, Nazmi; Devadiga, Sadashiva; Justice, Christopher; Nickeson, Jaime</p> <p>2008-01-01</p> <p>The Moderate Resolution Imaging Spectrometer (<span class="hlt">MODIS</span>) on-board NASA's Earth Observing System (EOS) Terra and <span class="hlt">Aqua</span> Satellites are key instruments for providing data on global land, atmosphere, and ocean dynamics. Derived <span class="hlt">MODIS</span> land, atmosphere and ocean products are central to NASA's mission to monitor and understand the Earth system. NASA has developed and generated on a systematic basis a suite of <span class="hlt">MODIS</span> products starting with the first Terra <span class="hlt">MODIS</span> data sensed February 22, 2000 and continuing with the first <span class="hlt">MODIS-Aqua</span> data sensed July 2, 2002. The <span class="hlt">MODIS</span> Land products are divided into three product suites: radiation budget products, ecosystem products, and land cover characterization products. The production and distribution of the <span class="hlt">MODIS</span> Land products are described, from initial software delivery by the <span class="hlt">MODIS</span> Land Science Team, to operational product generation and quality assurance, delivery to EOS archival and distribution centers, and product accuracy assessment and validation. Progress and lessons learned since the first <span class="hlt">MODIS</span> data were in early 2000 are described.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016AMT.....9.3193S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016AMT.....9.3193S&link_type=ABSTRACT"><span id="translatedtitle">Comparison of <span class="hlt">MODIS</span> and VIIRS cloud properties with ARM ground-based observations over Finland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sporre, Moa K.; O'Connor, Ewan J.; Håkansson, Nina; Thoss, Anke; Swietlicki, Erik; Petäjä, Tuukka</p> <p>2016-07-01</p> <p>Cloud retrievals from the Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) instruments aboard the satellites Terra and <span class="hlt">Aqua</span> and the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument aboard the Suomi-NPP satellite are evaluated using a combination of ground-based instruments providing vertical profiles of clouds. The ground-based measurements are obtained from the Atmospheric Radiation Measurement (ARM) programme mobile facility, which was deployed in Hyytiälä, Finland, between February and September 2014 for the Biogenic Aerosols - Effects on Clouds and Climate (BAECC) campaign. The satellite cloud parameters cloud top height (CTH) and liquid water path (LWP) are compared with ground-based CTH obtained from a cloud mask created using lidar and radar data and LWP acquired from a multi-channel microwave radiometer. Clouds from all altitudes in the atmosphere are investigated. The clouds are diagnosed as single or multiple layer using the ground-based cloud mask. For single-layer clouds, satellites overestimated CTH by 326 m (14 %) on average. When including multilayer clouds, satellites underestimated CTH by on average 169 m (5.8 %). <span class="hlt">MODIS</span> collection 6 overestimated LWP by on average 13 g m-2 (11 %). Interestingly, LWP for <span class="hlt">MODIS</span> collection 5.1 is slightly overestimated by <span class="hlt">Aqua</span> (4.56 %) but is underestimated by Terra (14.3 %). This underestimation may be attributed to a known issue with a drift in the <span class="hlt">reflectance</span> bands of the <span class="hlt">MODIS</span> instrument on Terra. This evaluation indicates that the satellite cloud parameters selected show reasonable agreement with their ground-based counterparts over Finland, with minimal influence from the large solar zenith angle experienced by the satellites in this high-latitude location.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70173626','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70173626"><span id="translatedtitle">High-frequency remote monitoring of large lakes with <span class="hlt">MODIS</span> 500 m imagery</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>McCullough, Ian M.; Loftin, Cynthia S.; Sader, Steven A.</p> <p>2012-01-01</p> <p>Satellite-based remote monitoring programs of regional lake water quality largely have relied on Landsat Thematic Mapper (TM) owing to its long image archive, moderate spatial resolution (30 m), and wide sensitivity in the visible portion of the electromagnetic spectrum, despite some notable limitations such as temporal resolution (i.e., 16 days), data pre-processing requirements to improve data quality, and aging satellites. Moderate-Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) sensors on <span class="hlt">Aqua</span>/Terra platforms compensate for these shortcomings, although at the expense of spatial resolution. We developed and evaluated a remote monitoring protocol for water clarity of large lakes using <span class="hlt">MODIS</span> 500 m data and compared <span class="hlt">MODIS</span> utility to Landsat-based methods. <span class="hlt">MODIS</span> images captured during May–September 2001, 2004 and 2010 were analyzed with linear regression to identify the relationship between lake water clarity and satellite-measured surface <span class="hlt">reflectance</span>. Correlations were strong (R² = 0.72–0.94) throughout the study period; however, they were the most consistent in August, <span class="hlt">reflecting</span> seasonally unstable lake conditions and inter-annual differences in algal productivity during the other months. The utility of <span class="hlt">MODIS</span> data in remote water quality estimation lies in intra-annual monitoring of lake water clarity in inaccessible, large lakes, whereas Landsat is more appropriate for inter-annual, regional trend analyses of lakes ≥ 8 ha. Model accuracy is improved when ancillary variables are included to <span class="hlt">reflect</span> seasonal lake dynamics and weather patterns that influence lake clarity. The identification of landscape-scale drivers of regional water quality is a useful way to supplement satellite-based remote monitoring programs relying on spectral data alone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20090027813&hterms=art+performance&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dart%2Bperformance','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20090027813&hterms=art+performance&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dart%2Bperformance"><span id="translatedtitle">Performance of <span class="hlt">MODIS</span> Thermal Emissive Bands On-orbit Calibration Algorithms</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Xiong, Xiaoxiong; Chang, T.</p> <p>2009-01-01</p> <p>Two nearly identical copies of the Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) are currently operated on-board the Terra and <span class="hlt">Aqua</span> spacecrafts, launched in December 1999 and May 2002, respectively. Together, they have produced an unprecedented amount of science data products, which are widely used for the studies of changes in the Earth's system of land, oceans, and atmosphere. <span class="hlt">MODIS</span> is a cross-track scanning radiometer, which uses a two-sided scan mirror and collects data continuously over a wide scan angle range (+/-55 degree relative to the instrument nadir) each scan of 1.47 seconds. It has 36 spectral bands with wavelengths ranging from visible (VIS) to long-wave infrared (LWIR). <span class="hlt">MODIS</span> bands 1-19 and 26 are the <span class="hlt">reflective</span> solar bands (RSB) and bands 20-25 and 27-36 are the thermal emissive bands (TEB). <span class="hlt">MODIS</span> was developed and designed with improvements made over its heritage sensors (such as AVHRR and Landsat) and, in particular, with more stringent calibration requirements. Because of this, <span class="hlt">MODIS</span> was built with a set of state-of-art on-board calibrators (OBC), which include a solar diffuser (SD), a solar diffuser stability monitor (SDSM), a blackbody (BB), a spectroradiometric calibration assembly (SRCA), and a space view (SV) port. With the exception of view angle differences, <span class="hlt">MODIS</span> OBC measurements and the Earth View (EV) observations are made via the same optical path. <span class="hlt">MODIS</span> TEB have a total of 160 individual TEB detectors (10 per band), which are located on two cold focal plane assemblies (CFPA). For nominal on-orbit operation, the CFPA temperature is controlled at 83K via a passive radiative cooler. For the TEB, the calibration requirements at specified typical scene radiances are less than or equal to 1% with an exception for the fire detection (low gain) band. <span class="hlt">MODIS</span> TEB on-orbit calibration is performed on a scan-by-scan basis using a quadratic calibration algorithm, and data collected from sensor responses to the onboard BB and SV. The BB</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014E%26ES...17a2112Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014E%26ES...17a2112Y"><span id="translatedtitle">Retrieval of Secchi disk depth in the Yellow Sea and East China Sea using 8-day <span class="hlt">MODIS</span> data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, D. F.; Xing, Q. G.; Lou, M. J.; Shi, P.</p> <p>2014-03-01</p> <p>Secchi disk depth (SDD), is widely used as an indicator of water clarity. The traditional sampling method is not only time-consuming and labor-intensive but also limited in terms of temporal and spatial coverage. Remote sensing technology may deal with these limitations. In this paper, the applicability of 8-day <span class="hlt">MODIS-Aqua</span> remote sensing <span class="hlt">reflectance</span> data with 4 km spatial resolution for estimating water clarity in the Yellow Sea and the East China Sea was investigated. Field data such as Secchi depths were collected from two cruises conducted in the Yellow Sea and the East China Sea from 5 May to 7 June 2009. A three-band algorithm to retrieve SDD was developed based on remote sensing <span class="hlt">reflectance</span> at bands of 488, 555, and 678 nm, which performed better than single-band model and band ratio algorithm, with a determination coefficient of 0.72 and a mean relative error of 19%. This suggests that 8-day <span class="hlt">MODIS-Aqua</span> products of remote sensing <span class="hlt">reflectance</span> could be used to assess water transparency in the study area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.A13J0305L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.A13J0305L"><span id="translatedtitle">Introduction to <span class="hlt">MODIS</span> Collection 6 'Deep Blue' aerosol products and strategy for cirrus-signal correction in AOD retrievals using 1.38 μm <span class="hlt">reflectance</span> data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, J.; Hsu, N. C.; Sayer, A. M.; Bettenhausen, C.</p> <p>2012-12-01</p> <p>This study shows the characteristics of the Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) Collection 6 Deep Blue aerosol products (hereafter, C006 DB products) and a strategy for correcting cirrus-signal in the aerosol optical depth (AOD) retrievals. The C006 DB products have several changes over the C005, including extended coverage, surface <span class="hlt">reflectance</span> model, aerosol microphysical model, and cloud screening, etc. One of the new features is the inclusion of pixel-level uncertainty estimates on the retrieved AOD. These uncertainty estimates have been determined based on a validation against Aerosol Robotic Network (AERONET) direct-Sun AOD measurements, and are parameterized as a function of AOD, viewing geometry, and retrieval quality flag. This will provide users with a simple way to assess the uncertainty on Deep Blue AOD data for their particular application of interest. Preliminary results show strong agreement with AERONET, suggesting that the Deep Blue algorithm performs as well as other state-of-the-art satellite AOD datasets. In addition, a strategy for cirrus-signal correction in the retrieved AOD is presented. The cirrus <span class="hlt">reflectance</span> at each wavelength to be used in the aerosol retrieval algorithms is determined by the relationships between <span class="hlt">reflectances</span> at 1.38 μm and the aerosol bands and subtracted from the original TOA <span class="hlt">reflectance</span> values assuming linear relationship for the optically thin case (ρ1.38 < 0.05). Since the 1.38 μm band is located in the strong water vapor absorption band, thus representing cirrus signal only, the slope between the 1.38 μm <span class="hlt">reflectance</span> values and minimum <span class="hlt">reflectance</span> values at each aerosol band for the corresponding values at 1.38 μm can be used to convert the 1.38 μm <span class="hlt">reflectance</span> to the cirrus <span class="hlt">reflectance</span> at each wavelength. Then, the cirrus-signal-corrected AOD can be retrieved by using the corrected <span class="hlt">reflectance</span> data as input data into the aerosol retrieval algorithms. The retrieval results show that the AOD</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040171173&hterms=Methodology+Research&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DMethodology%2Bof%2BResearch%2B','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040171173&hterms=Methodology+Research&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DMethodology%2Bof%2BResearch%2B"><span id="translatedtitle"><span class="hlt">MODIS</span> In-flight Calibration Methodologies</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Xiong, X.; Barnes, W.</p> <p>2004-01-01</p> <p><span class="hlt">MODIS</span> is a key instrument for the NASA's Earth Observing System (EOS) currently operating on the Terra spacecraft launched in December 1999 and <span class="hlt">Aqua</span> spacecraft launched in May 2002. It is a cross-track scanning radiometer, making measurements over a wide field of view in 36 spectral bands with wavelengths from 0.41 to 14.5 micrometers and providing calibrated data products for science and research communities in their studies of the Earth s system of land, oceans, and atmosphere. A complete suite of on-board calibrators (OBC) have been designed for the instruments in-flight calibration and characterization, including a solar diffuser (SD) and solar diffuser stability monitor (SDSM) system for the radiometric calibration of the 20 <span class="hlt">reflective</span> solar bands (RSB), a blackbody (BB) for the radiometric calibration of the 16 thermal emissive bands (TEB), and a spectro-radiometric calibration assembly (SRCA) for the spatial (all bands) and spectral (RSB only) characterization. This paper discusses <span class="hlt">MODIS</span> in-flight Cali bration methodologies of using its on-board calibrators. Challenging issues and examples of tracking and correcting instrument on-orbit response changes are presented, including SD degradation (20% at 412nm, 12% at 466nm, and 7% at 530nm over four and a half years) and response versus scan angle changes (10%, 4%, and 1% differences between beginning of the scan and end of the scan at 412nm, 466nm, and 530nm) in the VIS spectral region. Current instrument performance and lessons learned are also provided.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AMT.....6.2989L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AMT.....6.2989L"><span id="translatedtitle">The Collection 6 <span class="hlt">MODIS</span> aerosol products over land and ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Levy, R. C.; Mattoo, S.; Munchak, L. A.; Remer, L. A.; Sayer, A. M.; Patadia, F.; Hsu, N. C.</p> <p>2013-11-01</p> <p>The twin Moderate resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) sensors have been flying on Terra since 2000 and <span class="hlt">Aqua</span> since 2002, creating an extensive data set of global Earth observations. Here, we introduce the Collection 6 (C6) algorithm to retrieve aerosol optical depth (AOD) and aerosol size parameters from <span class="hlt">MODIS</span>-observed spectral <span class="hlt">reflectance</span>. While not a major overhaul from the previous Collection 5 (C5) version, there are enough changes that there are significant impacts to the products and their interpretation. The C6 aerosol data set will be created from three separate retrieval algorithms that operate over different surface types. These are the two "Dark Target" (DT) algorithms for retrieving (1) over ocean (dark in visible and longer wavelengths) and (2) over vegetated/dark-soiled land (dark in the visible), plus the "Deep Blue" (DB) algorithm developed originally for retrieving (3) over desert/arid land (bright in the visible). Here, we focus on DT-ocean and DT-land (#1 and #2). We have updated assumptions for central wavelengths, Rayleigh optical depths and gas (H2O, O3, CO2, etc.) absorption corrections, while relaxing the solar zenith angle limit (up to ≤ 84°) to increase poleward coverage. For DT-land, we have updated the cloud mask to allow heavy smoke retrievals, fine-tuned the assignments for aerosol type as function of season/location, corrected bugs in the Quality Assurance (QA) logic, and added diagnostic parameters such topographic altitude. For DT-ocean, improvements include a revised cloud mask for thin-cirrus detection, inclusion of wind speed dependence on the surface <span class="hlt">reflectance</span>, updates to logic of QA Confidence flag (QAC) assignment, and additions of important diagnostic information. At the same time, we quantified how "upstream" changes to instrument calibration, land/sea masking and cloud masking will also impact the statistics of global AOD, and affect Terra and <span class="hlt">Aqua</span> differently. For <span class="hlt">Aqua</span>, all changes will result in reduced</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMIN21A1040C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMIN21A1040C"><span id="translatedtitle">Ground-based vicarious radiometric calibration of Terra <span class="hlt">MODIS</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Czapla-Myers, J.; Thome, K.</p> <p>2009-12-01</p> <p>Accurate radiometric calibration is required by Earth-observing systems to ensure that the derived data products are of the highest quality. Preflight calibration is used as a baseline to understand the system before it is launched on orbit, while post-launch calibration is used to understand changes that may have occurred due to the nature of launching an instrument into space. On-orbit radiometric calibration ensures that changes in the system, including any onboard calibration sources, can be monitored. The Remote Sensing Group at the University of Arizona has been directly involved in the ground-based vicarious calibration of both Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> since their respective launches in 1999 and 2002. RSG personnel are present at a test site during sensor overpass, and surface <span class="hlt">reflectance</span> and atmospheric attenuation measurements are used as inputs to a radiative transfer code to determine the top-of-atmosphere radiance for the sensor under test. In the case of Terra <span class="hlt">MODIS</span>, a 1-km2 site at Railroad Valley, Nevada, is used as a test site. This work presents results obtained using the <span class="hlt">reflectance</span>-based approach at RSG’s Railroad Valley test site. Results from 10 years of in situ data collection at Railroad Valley show a percent difference in the seven land spectral channels between RSG and Terra <span class="hlt">MODIS</span> ranging from 1.6 % in channel 6 (1632 nm), to 5.1% in channel 4 (553 nm). The average percent difference for Terra MODIS’s seven land channels and RSG is 3.5%. The uncertainty is within the 3-5% predicted for ground-based vicarious calibration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009SPIE.7452E..17W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009SPIE.7452E..17W"><span id="translatedtitle">Characterization of <span class="hlt">MODIS</span> SD screen vignetting function using observations from spacecraft yaw maneuvers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Zhipeng; Xiong, Xiaoxiong</p> <p>2009-08-01</p> <p>The <span class="hlt">MODIS</span> <span class="hlt">reflective</span> solar bands (RSB) include both the low-gain and high-gain spectral bands depending on their specific applications. <span class="hlt">MODIS</span> RSBs are calibrated on-orbit by an on-board solar diffuser. In order to avoid detector response saturation when calibrating the high-gain bands, an optional attenuation screen, made of a metal plate with pinhole arrays, is placed in front of the SD panel. Since no pre-launch system-level characterization was made for the SD screen (SDS) vignetting function (VF), a series of spacecraft (Terra and <span class="hlt">Aqua</span>) yaw maneuvers were carried out to perform on-orbit characterization of the VF. Assuming that the low-gain bands and the high-gain bands have the same VF, the current VF was derived from yaw observations using the <span class="hlt">MODIS</span> low-gain bands through taking the ratio of their SD responses with and without the SDS in place. In this study, we attempt to characterize the SDS VF directly using detector responses of individual high-gain bands with the SDS in place only. The corresponding SD responses without the SDS, not available from measurements due to saturation, are calculated using detector gains, the SD bi-directional <span class="hlt">reflectance</span> factor (BRF), and the view geometry that matches the yaw observations with the SDS in place. Results and discussions are focused on the band dependent and detector dependent features of the SDS VF, and their potential impact on the RSB calibration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20070034809&hterms=html&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dhtml','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20070034809&hterms=html&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dhtml"><span id="translatedtitle">Generating a Long-Term Land Data Record from the AVHRR and <span class="hlt">MODIS</span> Instruments</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pedelty, Jeffrey; Devadiga, Sadashiva; Masuoka, Edward; Brown, Molly; Pinzon, Jorge; Tucker, Compton; Vermote, Eric; Prince, Stephen; Nagol, Jyotheshwar; Justice, Christopher; Roy, David; Ju, Junchang; Schaaf, Crystal; Liu, Jicheng; Privette, Jeffrey; Pincheiro, Ana</p> <p>2007-01-01</p> <p>The goal of NASA's Land Long Term Iiata Record (LTDR) project is to produce a consistent long term data set from the AVHRR and <span class="hlt">MODIS</span> instruments for land climate studies. The project will create daily surface <span class="hlt">reflectance</span> and normalized difference vegetation index (NDVI) products at a resolution of 0.05 deg., which is identical to the Climate Modeling Grid (CMG) used for <span class="hlt">MODIS</span> products from EOS Terra and <span class="hlt">Aqua</span>. Higher order products such as burned area, land surface temperature, albedo, bidirectional <span class="hlt">reflectance</span> distribution function (BRDF) correction, leaf area index (LAI), and fraction of photosyntheticalIy active radiation absorbed by vegetation (fPAR), will be created. The LTDR project will reprocess Global Area Coverage (GAC) data from AVHRR sensors onboard NOAA satellites by applying the preprocessing improvements identified in the AVHRR Pathfinder Il project and atmospheric and BRDF corrections used in <span class="hlt">MODIS</span> processing. The preprocessing improvements include radiometric in-flight vicarious calibration for the visible and near infrared channels and inverse navigation to relate an Earth location to each sensor instantaneous field of view (IFOV). Atmospheric corrections for Rayleigh scattering, ozone, and water vapor are undertaken, with aerosol correction being implemented. The LTDR also produces a surface <span class="hlt">reflectance</span> product for channel 3 (3.75 micrometers). Quality assessment (QA) is an integral part of the LTDR production system, which is monitoring temporal trands in the AVHRR products using time-series approaches developed for <span class="hlt">MODIS</span> land product quality assessment. The land surface <span class="hlt">reflectance</span> products have been evaluated at AERONET sites. The AVHRR data record from LTDR is also being compared to products from the PAL (Pathfinder AVHRR Land) and GIMMS (Global Inventory Modeling and Mapping Studies) systems to assess the relative merits of this reprocessing vis-a-vis these existing data products. The LTDR products and associated information can be found at</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20110007300&hterms=ecosystem+marine&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Decosystem%2Bmarine','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20110007300&hterms=ecosystem+marine&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Decosystem%2Bmarine"><span id="translatedtitle">Remote Sensing of Radiative and Microphysical Properties of Clouds During TC (sup 4): Results from MAS, MASTER, <span class="hlt">MODIS</span>, and MISR</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>King, Michael D.; Platnick, Steven; Wind, Galina; Arnold, G. Thomas; Dominguez, Roseanne T.</p> <p>2010-01-01</p> <p>The Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) Airborne Simulator (MAS) and <span class="hlt">MODIS</span>/Advanced Spaceborne Thermal Emission and <span class="hlt">Reflection</span> Radiometer (ASTER) Airborne Simulator (MASTER) were used to obtain measurements of the bidirectional <span class="hlt">reflectance</span> and brightness temperature of clouds at 50 discrete wavelengths between 0.47 and 14.2 microns (12.9 microns for MASTER). These observations were obtained from the NASA ER-2 aircraft as part of the Tropical Composition, Cloud and Climate Coupling (TC4) experiment conducted over Central America and surrounding Pacific and Atlantic Oceans between 17 July and 8 August 2007. Multispectral images in eleven distinct bands were used to derive a confidence in clear sky (or alternatively the probability Of cloud) over land and ocean ecosystems. Based on the results of individual tests run as part of the cloud mask, an algorithm was developed to estimate the phase of the clouds (liquid water, ice, or undetermined phase). The cloud optical thickness and effective radius were derived for both liquid water and ice clouds that were detected during each flight, using a nearly identical algorithm to that implemented operationally to process <span class="hlt">MODIS</span> Cloud data from the <span class="hlt">Aqua</span> and Terra satellites (Collection 5). This analysis shows that the cloud mask developed for operational use on <span class="hlt">MODIS</span>, and tested using MAS and MASTER data in TC(sup 4), is quite capable of distinguishing both liquid water and ice clouds during daytime conditions over both land and ocean. The cloud optical thickness and effective radius retrievals use five distinct bands of the MAS (or MASTER), and these results were compared with nearly simultaneous retrievals of marine liquid water clouds from <span class="hlt">MODIS</span> on the Terra spacecraft. Finally, this <span class="hlt">MODIS</span>-based algorithm was adapted to Multiangle Imaging SpectroRadiometer (MISR) data to infer the cloud optical thickness Of liquid water clouds from MISR. Results of this analysis are compared and contrasted.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130014411','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130014411"><span id="translatedtitle">A Full Snow Season in Yellowstone: A Database of Restored <span class="hlt">Aqua</span> Band 6</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gladkova, Irina; Grossberg, Michael; Bonev, George; Romanov, Peter; Riggs, George; Hall, Dorothy</p> <p>2013-01-01</p> <p>The algorithms for estimating snow extent for the Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) optimally use the 1.6- m channel which is unavailable for <span class="hlt">MODIS</span> on <span class="hlt">Aqua</span> due to detector damage. As a test bed to demonstrate that <span class="hlt">Aqua</span> band 6 can be restored, we chose the area surrounding Yellowstone and Grand Teton national parks. In such rugged and difficult-to-access terrain, satellite images are particularly important for providing an estimation of snow-cover extent. For the full 2010-2011 snow season covering the Yellowstone region, we have used quantitative image restoration to create a database of restored <span class="hlt">Aqua</span> band 6. The database includes restored radiances, normalized vegetation index, normalized snow index, thermal data, and band-6-based snow-map products. The restored <span class="hlt">Aqua</span>-band-6 data have also been regridded and combined with Terra data to produce a snow-cover map that utilizes both Terra and <span class="hlt">Aqua</span> snow maps. Using this database, we show that the restored <span class="hlt">Aqua</span>-band-6-based snow-cover extent has a comparable performance with respect to ground stations to the one based on Terra. The result of a restored band 6 from <span class="hlt">Aqua</span> is that we have an additional band-6 image of the Yellowstone region each day. This image can be used to mitigate cloud occlusion, using the same algorithms used for band 6 on Terra. We show an application of this database of restored band-6 images to illustrate the value of creating a cloud gap filling using the National Aeronautics and Space Administration s operational cloud masks and data from both <span class="hlt">Aqua</span> and Terra.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110007875','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110007875"><span id="translatedtitle">Validation of the <span class="hlt">MODIS</span> "Clear-Sky" Surface Temperature of the Greenland Ice Sheet</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hall, Dorothy K.; Koenig, L. S.; DiGirolamo, N. E.; Comiso, J.; Shuman, C. A.</p> <p>2011-01-01</p> <p>Surface temperatures on the Greenland Ice Sheet have been studied on the ground, using automatic weather station (AWS) data from the Greenland-Climate Network (GC-Net), and from analysis of satellite sensor data. Using Advanced Very High Frequency Radiometer (AVHRR) weekly surface temperature maps, warming of the surface of the Greenland Ice Sheet has been documented from 1981 to present. We extend and refine this record using higher-resolution Moderate-Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) data from March 2000 to the present. To permit changes to be observed over time, we are developing a well-characterized monthly climate-data record (CDR) of the "clear-sky" surface temperature of the Greenland Ice Sheet using data from both the Terra and <span class="hlt">Aqua</span> satellites. We use the <span class="hlt">MODIS</span> ice-surface temperature (IST) algorithm. Validation of the CDR consists of several facets: 1) comparisons between the Terra and <span class="hlt">Aqua</span> IST maps; 2) comparisons between ISTs and in-situ measurements; 3) comparisons between ISTs and AWS data; and 4) comparisons of ISTs with surface temperatures derived from other satellite instruments such as the Thermal Emission and <span class="hlt">Reflection</span> Radiometer. In this work, we focus on 1) and 2) above. Surface temperatures on the Greenland Ice Sheet have been studied on the ground, using automatic weather station (AWS) data from the Greenland-Climate Network (GC-Net), and from analysis of satellite sensor data. Using Advanced Very High Frequency Radiometer (AVHRR) weekly surface temperature maps, warming of the surface of the Greenland Ice Sheet has been documented from 1981 to present. We extend and refine this record using higher-resolution Moderate-Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) data from March 2000 to the present. To permit changes to be observed over time, we are developing a well-characterized monthly climate-data record (CDR) of the "clear-sky" surface temperature of the Greenland Ice Sheet using data from both the Terra and <span class="hlt">Aqua</span> satellites</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PhDT........43M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PhDT........43M&link_type=ABSTRACT"><span id="translatedtitle">Estimation of suspended particulate matter concentration in the Mississippi Sound using <span class="hlt">MODIS</span> imagery</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Merritt, Danielle</p> <p></p> <p>The discharge of sediment-laden rivers into the Mississippi Sound increases the turbidity of coastal waters. The concentration of suspended particulates is an important parameter in the analysis of coastal water quality factors. The spatiotemporal resolution associated with satellite sensors makes remote sensing an ideal tool to monitor suspended particulate concentrations. Accordingly, the presented research evaluated the validity of published algorithms that relate remote sensing <span class="hlt">reflectance</span> (Rrs) with suspended particulate matter for the Mississippi Sound. Additionally, regression analysis was used to correlate in situ SPM concentrations with coincident observations of visible and nearinfrared band <span class="hlt">reflectance</span> collected by the <span class="hlt">MODIS</span> <span class="hlt">Aqua</span> sensor in order to develop a predictive model for SPM. The most robust algorithm yielded an RMSE of 15.53% (n = 86) in the determination of SPM concentrations. The application of this algorithm allows for the rapid assessment of water quality issues related to elevated SPM concentrations in the Mississippi Sound.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70032007','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70032007"><span id="translatedtitle">Detection rates of the <span class="hlt">MODIS</span> active fire product in the United States</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hawbaker, T.J.; Radeloff, V.C.; Syphard, A.D.; Zhu, Z.; Stewart, S.I.</p> <p>2008-01-01</p> <p><span class="hlt">MODIS</span> active fire data offer new information about global fire patterns. However, uncertainties in detection rates can render satellite-derived fire statistics difficult to interpret. We evaluated the <span class="hlt">MODIS</span> 1??km daily active fire product to quantify detection rates for both Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> sensors, examined how cloud cover and fire size affected detection rates, and estimated how detection rates varied across the United States. <span class="hlt">MODIS</span> active fire detections were compared to 361 reference fires (??? 18??ha) that had been delineated using pre- and post-fire Landsat imagery. Reference fires were considered detected if at least one <span class="hlt">MODIS</span> active fire pixel occurred within 1??km of the edge of the fire. When active fire data from both <span class="hlt">Aqua</span> and Terra were combined, 82% of all reference fires were found, but detection rates were less for <span class="hlt">Aqua</span> and Terra individually (73% and 66% respectively). Fires not detected generally had more cloudy days, but not when the <span class="hlt">Aqua</span> data were considered exclusively. <span class="hlt">MODIS</span> detection rates decreased with fire size, and the size at which 50% of all fires were detected was 105??ha when combining <span class="hlt">Aqua</span> and Terra (195??ha for <span class="hlt">Aqua</span> and 334??ha for Terra alone). Across the United States, detection rates were greatest in the West, lower in the Great Plains, and lowest in the East. The <span class="hlt">MODIS</span> active fire product captures large fires in the U.S. well, but may under-represent fires in areas with frequent cloud cover or rapidly burning, small, and low-intensity fires. We recommend that users of the <span class="hlt">MODIS</span> active fire data perform individual validations to ensure that all relevant fires are included. ?? 2008 Elsevier Inc. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010ACP....1010949Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010ACP....1010949Z"><span id="translatedtitle">A decadal regional and global trend analysis of the aerosol optical depth using a data-assimilation grade over-water <span class="hlt">MODIS</span> and Level 2 MISR aerosol products</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, J.; Reid, J. S.</p> <p>2010-11-01</p> <p>Using the ten-year (2000-2009) Data-Assimilation (DA) quality Terra <span class="hlt">MODIS</span> and MISR aerosol products, as well as 7 years of <span class="hlt">Aqua</span> <span class="hlt">MODIS</span>, we studied both regional and global aerosol trends over oceans. This included both operational and data assimilation grade versions of the products. After correcting for what appears to be aerosol signal drift from the radiometric calibration of both <span class="hlt">MODIS</span> instruments, we found <span class="hlt">MODIS</span> and MISR agreed on a statistically negligible global trend of ±0.003/per decade. Our study also suggests that AODs over the Indian Bay of Bengal, east coast of Asia, and Arabian Sea show increasing trends of 0.07, 0.06, and 0.06 per decade for <span class="hlt">MODIS</span>, respectively. These regional trends are considered as significant with a confidence level above 95%. Similar increasing trends were found from MISR, but with less relative magnitude. These trends <span class="hlt">reflect</span> respective increases in the optical intensity of aerosol events in each region: anthropogenic aerosols over the east coast of China and Indian Bay of Bengal; and a stronger influence from dust events over the Arabian Sea. Negative AOD trends, low in confidence levels, are found off Central America, the east coast of North America, and the west coast of Africa, which indicate that longer periods of observation are necessary to be conclusive.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010ACPD...1018879Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010ACPD...1018879Z"><span id="translatedtitle">A decadal regional and global trend analysis of the aerosol optical depth using a data-assimilation grade over-water <span class="hlt">MODIS</span> and Level 2 MISR aerosol products</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, J.; Reid, J. S.</p> <p>2010-08-01</p> <p>Using the ten-year (2000-2009) DA quality Terra <span class="hlt">MODIS</span> and MISR aerosol products, as well as 7 years of <span class="hlt">Aqua</span> <span class="hlt">MODIS</span>, we studied both regional and global aerosol trends over oceans. This included both natural and data assimilation grade versions of the products. Contrary to some of the previous studies that showed a decreasing trend in aerosol optical depth (AOD) over global oceans, after correcting for what appears to be aerosol signal drift from the radiometric calibration of both <span class="hlt">MODIS</span> instruments, we found <span class="hlt">MODIS</span> and MISR agreed on a statistically negligible global trend of 0.0003/per year. Our study also suggests that AODs over the Indian Bay of Bengal, east coast of Asia, and Arabian Sea show statistically significant increasing trends of 0.07, 0.06, and 0.06 per ten years for <span class="hlt">MODIS</span>, respectively. Similar increasing trends were found from MISR, but with less relative magnitude. These trends <span class="hlt">reflect</span> respective increases in the optical intensity of aerosol events in each region: anthropogenic aerosols over the east coast of China and Indian Bay of Bengal; and a stronger influence from dust events over the Arabian Sea. Negative AOD trends are found off Central America, the east coast of North America, and the west coast of Africa. However, confidence levels are low in these regions, which indicate that longer periods of observation are necessary to be conclusive.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRD..120.4132C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRD..120.4132C"><span id="translatedtitle">Frequency and causes of failed <span class="hlt">MODIS</span> cloud property retrievals for liquid phase clouds over global oceans</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cho, Hyoun-Myoung; Zhang, Zhibo; Meyer, Kerry; Lebsock, Matthew; Platnick, Steven; Ackerman, Andrew S.; Di Girolamo, Larry; -Labonnote, Laurent C.; Cornet, Céline; Riedi, Jerome; Holz, Robert E.</p> <p>2015-05-01</p> <p>Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) retrieves cloud droplet effective radius (r_e) and optical thickness (τ) by projecting observed cloud <span class="hlt">reflectances</span> onto a precomputed look-up table (LUT). When observations fall outside of the LUT, the retrieval is considered "failed" because no combination of τ and r_e within the LUT can explain the observed cloud <span class="hlt">reflectances</span>. In this study, the frequency and potential causes of failed <span class="hlt">MODIS</span> retrievals for marine liquid phase (MLP) clouds are analyzed based on 1 year of <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> Collection 6 products and collocated CALIOP and CloudSat observations. The retrieval based on the 0.86 μm and 2.1 μm <span class="hlt">MODIS</span> channel combination has an overall failure rate of about 16% (10% for the 0.86 μm and 3.7 μm combination). The failure rates are lower over stratocumulus regimes and higher over the broken trade wind cumulus regimes. The leading type of failure is the "r_e too large" failure accounting for 60%-85% of all failed retrievals. The rest is mostly due to the "r_e too small" or τ retrieval failures. Enhanced retrieval failure rates are found when MLP cloud pixels are partially cloudy or have high subpixel inhomogeneity, are located at special Sun-satellite viewing geometries such as sunglint, large viewing or solar zenith angles, or cloudbow and glory angles, or are subject to cloud masking, cloud overlapping, and/or cloud phase retrieval issues. The majority (more than 84%) of failed retrievals along the CALIPSO track can be attributed to at least one or more of these potential reasons. The collocated CloudSat radar <span class="hlt">reflectivity</span> observations reveal that the remaining failed retrievals are often precipitating. It remains an open question whether the extremely large r_e values observed in these clouds are the consequence of true cloud microphysics or still due to artifacts not included in this study.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20030108344&hterms=Water+Africa&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DWater%2BAfrica','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20030108344&hterms=Water+Africa&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DWater%2BAfrica"><span id="translatedtitle">A Technique for Remote Sensing of Suspended Sediments and Shallow Coastal Waters Using <span class="hlt">MODIS</span> Visible and Near-IR Channels</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Li, Rong-Rong; Kaufman, Yoram J.</p> <p>2002-01-01</p> <p>We have developed an algorithm to detect suspended sediments and shallow coastal waters using imaging data acquired with the Moderate Resolution Imaging SpectroRadiometer (<span class="hlt">MODIS</span>). The <span class="hlt">MODIS</span> instruments on board the NASA Terra and <span class="hlt">Aqua</span> Spacecrafts are equipped with one set of narrow channels located in a wide 0.4 - 2.5 micron spectral range. These channels were designed primarily for remote sensing of the land surface and atmosphere. We have found that the set of land and cloud channels are also quite useful for remote sensing of the bright coastal waters. We have developed an empirical algorithm, which uses the narrow <span class="hlt">MODIS</span> channels in this wide spectral range, for identifying areas with suspended sediments in turbid waters and shallow waters with bottom <span class="hlt">reflections</span>. In our algorithm, we take advantage of the strong water absorption at wavelengths longer than 1 micron that does not allow illumination of sediments in the water or a shallow ocean floor. <span class="hlt">MODIS</span> data acquired over the east coast of China, west coast of Africa, Arabian Sea, Mississippi Delta, and west coast of Florida are used in this study.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150001339','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150001339"><span id="translatedtitle">An Approach for the Long-Term 30-m Land Surface Snow-Free Albedo Retrieval from Historic Landsat Surface <span class="hlt">Reflectance</span> and <span class="hlt">MODIS</span>-based A Priori Anisotropy Knowledge</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Shuai, Yanmin; Masek, Jeffrey G.; Gao, Feng; Schaaf, Crystal B.; He, Tao</p> <p>2014-01-01</p> <p>Land surface albedo has been recognized by the Global Terrestrial Observing System (GTOS) as an essential climate variable crucial for accurate modeling and monitoring of the Earth's radiative budget. While global climate studies can leverage albedo datasets from <span class="hlt">MODIS</span>, VIIRS, and other coarse-resolution sensors, many applications in heterogeneous environments can benefit from higher-resolution albedo products derived from Landsat. We previously developed a "<span class="hlt">MODIS</span>-concurrent" approach for the 30-meter albedo estimation which relied on combining post-2000 Landsat data with <span class="hlt">MODIS</span> Bidirectional <span class="hlt">Reflectance</span> Distribution Function (BRDF) information. Here we present a "pre-<span class="hlt">MODIS</span> era" approach to extend 30-m surface albedo generation in time back to the 1980s, through an a priori anisotropy Look-Up Table (LUT) built up from the high quality MCD43A BRDF estimates over representative homogenous regions. Each entry in the LUT <span class="hlt">reflects</span> a unique combination of land cover, seasonality, terrain information, disturbance age and type, and Landsat optical spectral bands. An initial conceptual LUT was created for the Pacific Northwest (PNW) of the United States and provides BRDF shapes estimated from <span class="hlt">MODIS</span> observations for undisturbed and disturbed surface types (including recovery trajectories of burned areas and non-fire disturbances). By accepting the assumption of a generally invariant BRDF shape for similar land surface structures as a priori information, spectral white-sky and black-sky albedos are derived through albedo-to-nadir <span class="hlt">reflectance</span> ratios as a bridge between the Landsat and <span class="hlt">MODIS</span> scale. A further narrow-to-broadband conversion based on radiative transfer simulations is adopted to produce broadband albedos at visible, near infrared, and shortwave regimes.We evaluate the accuracy of resultant Landsat albedo using available field measurements at forested AmeriFlux stations in the PNW region, and examine the consistency of the surface albedo generated by this approach</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20050156603&hterms=effect+climatic+changes+db&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Deffect%2Bclimatic%2Bchanges%2Bdb','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20050156603&hterms=effect+climatic+changes+db&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Deffect%2Bclimatic%2Bchanges%2Bdb"><span id="translatedtitle"><span class="hlt">MODIS</span> Direct Broadcast and Remote Sensing Applications</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tsay, Si-Chee</p> <p>2004-01-01</p> <p>The Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) was developed by NASA and launched onboard both Terra spacecraft on December 18, 1999 and <span class="hlt">Aqua</span> spacecraft on May 4, 2002. <span class="hlt">MODIS</span> scans a swath width sufficient to provide nearly complete global coverage every two days from a polar-orbiting, sun-synchronous, platform at an altitude of 705 km, and provides images in 36 spectral bands between 0.415 and 14.235 microns with spatial resolutions of 250 m (2 bands), 500 m (5 bands) and 1000 m (29 bands). Equipped with direct broadcast capability, the <span class="hlt">MODIS</span> measurements can be received worldwide real time. There are 82 ingest sites (over 900 users, listed on the Direct Readout Portal) around the world for Terra/<span class="hlt">Aqua-MODIS</span> Direct Broadcast DB) downlink. This represents 27 (6 from EOS science team members) science research organizations for DB land, ocean and atmospheric processing, and 53 companies that base their application algorithms and value added products on DB data. In this paper we will describe the various methods being used for the remote sensing of cloud properties using <span class="hlt">MODIS</span> data, focusing primarily on the <span class="hlt">MODIS</span> cloud mask used to distinguish clouds, clear sky, heavy aerosol, and shadows on the ground, and on the remote sensing of aerosol/cloud optical properties, especially optical thickness and effective particle size. Additional properties of clouds derived from multispectral thermal infrared measurements, especially cloud top pressure and emissivity, will also be described. Preliminary results will be presented and discussed their implications in regional-to-global climatic effects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20000105141&hterms=bottleneck&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dbottleneck','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20000105141&hterms=bottleneck&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dbottleneck"><span id="translatedtitle">Production and Distribution of Global Products From <span class="hlt">MODIS</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Masuoka, Edward; Smith, David E. (Technical Monitor)</p> <p>2000-01-01</p> <p>The Moderate Resolution Imaging Spectroradiometer was launched on the EOS Terra spacecraft in December 1999 and will also fly on EOS <span class="hlt">Aqua</span> in December 2000. With 36 spectral bands from the visible through thermal infrared and spatial resolution of 250m to 1 kilometer, each <span class="hlt">MODIS</span> instrument will image the entire Earth surface in 2 days. This paper traces the flow of <span class="hlt">MODIS</span> data products from the receipt of Level 0 data at the EDOS facility, through the production and quality assurance process to the Distributed Active Archive Centers (DAACs), which ship products to the user community. It describes where to obtain products and plans for reprocessing <span class="hlt">MODIS</span> products. As most components of the ground system are severely limited in their capacity to distribute <span class="hlt">MODIS</span> products, it also describes the key characteristics of <span class="hlt">MODIS</span> products and their metadata that allow a user to optimize their selection of products given anticipate bottlenecks in distribution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040171375','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040171375"><span id="translatedtitle">Cloud Inhomogeneity from <span class="hlt">MODIS</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Oreopoulos, Lazaros; Cahalan, Robert F.</p> <p>2004-01-01</p> <p>Two full months (July 2003 and January 2004) of <span class="hlt">MODIS</span> Atmosphere Level-3 data from the Terra and <span class="hlt">Aqua</span> satellites are analyzed in order to characterize the horizontal variability of cloud optical thickness and water path at global scales. Various options to derive cloud variability parameters are discussed. The climatology of cloud inhomogeneity is built by first calculating daily parameter values at spatial scales of l degree x 1 degree, and then at zonal and global scales, followed by averaging over monthly time scales. Geographical, diurnal, and seasonal changes of inhomogeneity parameters are examined separately for the two cloud phases, and separately over land and ocean. We find that cloud inhomogeneity is weaker in summer than in winter, weaker over land than ocean for liquid clouds, weaker for local morning than local afternoon, about the same for liquid and ice clouds on a global scale, but with wider probability distribution functions (PDFs) and larger latitudinal variations for ice, and relatively insensitive to whether water path or optical thickness products are used. Typical mean values at hemispheric and global scales of the inhomogeneity parameter nu (roughly the mean over the standard deviation of water path or optical thickness), range from approximately 2.5 to 3, while for the inhomogeneity parameter chi (the ratio of the logarithmic to linear mean) from approximately 0.7 to 0.8. Values of chi for zonal averages can occasionally fall below 0.6 and for individual gridpoints below 0.5. Our results demonstrate that <span class="hlt">MODIS</span> is capable of revealing significant fluctuations in cloud horizontal inhomogenity and stress the need to model their global radiative effect in future studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009EGUGA..1112835C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009EGUGA..1112835C&link_type=ABSTRACT"><span id="translatedtitle">Regional scale net radiation estimation by means of Landsat and TERRA/<span class="hlt">AQUA</span> imagery and GIS modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cristóbal, J.; Ninyerola, M.; Pons, X.; Llorens, P.; Poyatos, R.</p> <p>2009-04-01</p> <p>Net radiation (Rn) is one of the most important variables for the estimation of surface energy budget and is used for various applications including agricultural meteorology, climate monitoring and weather prediction. Moreover, net radiation is an essential input variable for potential as well as actual evapotranspiration modeling. Nowadays, radiometric measurements provided by Remote Sensing and GIS analysis are the technologies used to compute net radiation at regional scales in a feasible way. In this study we present a regional scale estimation of the daily Rn on clear days, (Catalonia, NE of the Iberian Peninsula), using a set of 22 Landsat images (17 Landsat-5 TM and 5 Landsat-7 ETM+) and 171 TERRA/<span class="hlt">AQUA</span> images <span class="hlt">MODIS</span> from 2000 to 2007 period. TERRA/<span class="hlt">AQUA</span> <span class="hlt">MODIS</span> images have been downloaded by means of the EOS Gateway. We have selected three different types of products which contain the remote sensing data we have used to model daily Rn: daily LST product, daily calibrated <span class="hlt">reflectances</span> product and daily atmospheric water vapour product. Landsat-5 TM images have been corrected by means of conventional techniques based on first order polynomials taking into account the effect of land surface relief using a Digital Elevation Model, obtaining an RMS less than 30 m. Radiometric correction of Landsat non-thermal bands has been done following the methodology proposed by Pons and Solé (1994), which allows to reduce the number of undesired artifacts that are due to the effects of the atmosphere or to the differential illumination which is, in turn, due to the time of the day, the location in the Earth and the relief (zones being more illuminated than others, shadows, etc). Atmospheric correction of Landsat thermal band has been carried out by means of a single-channel algorithm improvement developed by Cristóbal et al. (2009) and the land surface emissivity computed by means of the methodology proposed by Sobrino and Raissouni (2000). Rn has been estimated through the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20020081319&hterms=usher&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dusher','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20020081319&hterms=usher&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dusher"><span id="translatedtitle">Global Aerosol Remote Sensing from <span class="hlt">MODIS</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ichoku, Charles; Kaufman, Yoram J.; Remer, Lorraine A.; Chu, D. Allen; Mattoo, Shana; Tanre, Didier; Levy, Robert; Li, Rong-Rong; Martins, Jose V.; Lau, William K. M. (Technical Monitor)</p> <p>2002-01-01</p> <p>The physical characteristics, composition, abundance, spatial distribution and dynamics of global aerosols are still very poorly known, and new data from satellite sensors have long been awaited to improve current understanding and to give a boost to the effort in future climate predictions. The derivation of aerosol parameters from the MODerate resolution Imaging Spectro-radiometer (<span class="hlt">MODIS</span>) sensors aboard the Earth Observing System (EOS) Terra and <span class="hlt">Aqua</span> polar-orbiting satellites ushers in a new era in aerosol remote sensing from space. Terra and <span class="hlt">Aqua</span> were launched on December 18, 1999 and May 4, 2002 respectively, with daytime equator crossing times of approximately 10:30 am and 1:30 pm respectively. Several aerosol parameters are retrieved at 10-km spatial resolution (level 2) from <span class="hlt">MODIS</span> daytime data. The <span class="hlt">MODIS</span> aerosol algorithm employs different approaches to retrieve parameters over land and ocean surfaces, because of the inherent differences in the solar spectral radiance interaction with these surfaces. The parameters retrieved include: aerosol optical thickness (AOT) at 0.47, 0.55 and 0.66 micron wavelengths over land, and at 0.47, 0.55, 0.66, 0.87, 1.2, 1.6, and 2.1 micron over ocean; Angstrom exponent over land and ocean; and effective radii, and the proportion of AOT contributed by the small mode aerosols over ocean. To ensure the quality of these parameters, a substantial part of the Terra-<span class="hlt">MODIS</span> aerosol products were validated globally and regionally, based on cross correlation with corresponding parameters derived from ground-based measurements from AERONET (AErosol RObotic NETwork) sun photometers. Similar validation efforts are planned for the <span class="hlt">Aqua-MODIS</span> aerosol products. The <span class="hlt">MODIS</span> level 2 aerosol products are operationally aggregated to generate global daily, eight-day (weekly), and monthly products at one-degree spatial resolution (level 3). <span class="hlt">MODIS</span> aerosol data are used for the detailed study of local, regional, and global aerosol concentration</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B33C0193L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B33C0193L"><span id="translatedtitle">Mapping Crop Cycles in China Using <span class="hlt">MODIS</span>-EVI Time Series</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, L.; Friedl, M. A.; Xin, Q.; Gray, J. M.; Pan, Y.; Frolking, S. E.</p> <p>2014-12-01</p> <p>As the Earth's population continues to grow and demand for food increases, multiple cropping is an effective way to increase crop production. Cropping intensity, which we define here as the number of cropping cycles per year, is an important dimension of land use that is strongly influences water demand and agricultural production. Satellite data provide global land cover maps with indispensable information regarding areal extent of global croplands and its distribution. However, the land use information such as cropping intensity is not routinely provided by global land cover products from instruments such as <span class="hlt">MODIS</span>, because mapping this information from remote sensing is challenging. We present a straight forward but efficient algorithm for automated mapping of agricultural intensity over large geographic regions using 8-day <span class="hlt">MODIS</span> EVI time series data derived from Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> surface <span class="hlt">reflectance</span> products. The proposed algorithm first applies an adaptive Savitzky-Golay filter to smooth Enhanced Vegetation Index (EVI) time series derived from <span class="hlt">MODIS</span> surface <span class="hlt">reflectance</span> data, and then uses an iterative moving-window methodology to identify cropping cycles from the smoothed EVI time series. Comparison of results from our algorithm with national survey data at both the provincial and prefectural level in China show that the algorithm provides estimates of gross sown area that agree well with inventory data. Accuracy assessment using data generated by expert classification of randomly selected pixel samples indicates an overall accuracy of 91.0% for three agricultural intensity classes. More generally, the algorithm shows significant potential to automatically estimate reliable cropping intensity information in support of large-scale studies of agricultural land use and land cover dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040031769&hterms=cloud+bases&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dcloud%2Bbases','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040031769&hterms=cloud+bases&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dcloud%2Bbases"><span id="translatedtitle">Global Multispectral Cloud Retrievals from <span class="hlt">MODIS</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>King, Michael D.</p> <p>2003-01-01</p> <p>The Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) was developed by NASA and launched onboard the Terra spacecraft on December 18,1999 and <span class="hlt">Aqua</span> spacecraft on May 4,2002. It achieved its final orbit and began Earth observations on February 24, 2000 for Terra and June 24, 2002 for <span class="hlt">Aqua</span>. A comprehensive set of remote sensing algorithms for cloud masking and the retrieval of cloud physical and optical properties has been developed by members of the <span class="hlt">MODIS</span> atmosphere science team. The archived products from these algorithms have applications in climate change studies, climate modeling, numerical weather prediction, as well as fundamental atmospheric research. In addition to an extensive cloud mask, products include cloud-top properties (temperature, pressure, effective emissivity), cloud thermodynamic phase, cloud optical and microphysical parameters (optical thickness, effective particle radius, water path), as well as derived statistics. We will describe the various cloud properties being analyzed on a global basis from both Terra and <span class="hlt">Aqua</span>, and will show characteristics of cloud optical and microphysical properties as a function of latitude for land and ocean separately, and contrast the statistical properties of similar cloud types in various parts of the world.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120008715','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120008715"><span id="translatedtitle">The Operational <span class="hlt">MODIS</span> Cloud Optical and Microphysical Property Product: Overview of the Collection 6 Algorithm and Preliminary Results</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Platnick, Steven; King, Michael D.; Wind, Galina; Amarasinghe, Nandana; Marchant, Benjamin; Arnold, G. Thomas</p> <p>2012-01-01</p> <p>Operational Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) retrievals of cloud optical and microphysical properties (part of the archived products MOD06 and MYD06, for <span class="hlt">MODIS</span> Terra and <span class="hlt">Aqua</span>, respectively) are currently being reprocessed along with other <span class="hlt">MODIS</span> Atmosphere Team products. The latest "Collection 6" processing stream, which is expected to begin production by summer 2012, includes updates to the previous cloud retrieval algorithm along with new capabilities. The 1 km retrievals, based on well-known solar <span class="hlt">reflectance</span> techniques, include cloud optical thickness, effective particle radius, and water path, as well as thermodynamic phase derived from a combination of solar and infrared tests. Being both global and of high spatial resolution requires an algorithm that is computationally efficient and can perform over all surface types. Collection 6 additions and enhancements include: (i) absolute effective particle radius retrievals derived separately from the 1.6 and 3.7 !-lm bands (instead of differences relative to the standard 2.1 !-lm retrieval), (ii) comprehensive look-up tables for cloud <span class="hlt">reflectance</span> and emissivity (no asymptotic theory) with a wind-speed interpolated Cox-Munk BRDF for ocean surfaces, (iii) retrievals for both liquid water and ice phases for each pixel, and a subsequent determination of the phase based, in part, on effective radius retrieval outcomes for the two phases, (iv) new ice cloud radiative models using roughened particles with a specified habit, (v) updated spatially-complete global spectral surface albedo maps derived from <span class="hlt">MODIS</span> Collection 5, (vi) enhanced pixel-level uncertainty calculations incorporating additional radiative error sources including the <span class="hlt">MODIS</span> L1 B uncertainty index for assessing band and scene-dependent radiometric uncertainties, (v) and use of a new 1 km cloud top pressure/temperature algorithm (also part of MOD06) for atmospheric corrections and low cloud non-unity emissivity temperature adjustments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20040171680&hterms=land+cover+change&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dland%2Bcover%2Bchange','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20040171680&hterms=land+cover+change&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dland%2Bcover%2Bchange"><span id="translatedtitle">Spatially Complete Surface Albedo Data Sets: Value-Added Products Derived from Terra <span class="hlt">MODIS</span> Land Products</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Moody, Eric G.; King, Michael D.; Platnick, Steven; Schaaf, Crystal B.; Gao, Feng</p> <p>2004-01-01</p> <p>Spectral land surface albedo is an important parameter for describing the radiative properties of the Earth. Accordingly it <span class="hlt">reflects</span> the consequences of natural and human interactions, such as anthropogenic, meteorological, and phenological effects, on global and local climatological trends. Consequently, albedos are integral parts in a variety of research areas, such as general circulation models (GCMs), energy balance studies, modeling of land use and land use change, and biophysical, oceanographic, and meteorological studies. Recent observations of diffuse bihemispherical (white-sky) and direct beam directional hemispherical (black-sky ) land surface albedo included in the MOD43B3 product from <span class="hlt">MODIS</span> instruments aboard NASA's Terra and <span class="hlt">Aqua</span> satellite platforms have provided researchers with unprecedented spatial, spectral, and temporal characteristics. Cloud and seasonal snow cover, however, curtail retrievals to approximately half the global land surfaces on an annual equal-angle basis, precluding MOD43B3 albedo products from direct inclusion in some research projects and production environments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160005113','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160005113"><span id="translatedtitle">EOS <span class="hlt">Aqua</span> Mission Status at Earth Science Constellation MOWG Meeting @ LASP April 13, 2016</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Guit, William J.</p> <p>2016-01-01</p> <p>This presentation <span class="hlt">reflects</span> the EOS <span class="hlt">Aqua</span> mission status, spacecraft subsystem summary, recent and planned activities, inclination adjust maneuvers, propellant usage and lifetime estimate, orbital maintenance maneuvers, conjunction assessment high interest events, ground track error, spacecraft orbital parameters trends and predictions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.A33M0335C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.A33M0335C"><span id="translatedtitle">Adapting <span class="hlt">MODIS</span> Dust Mask Algorithm to Suomi NPP VIIRS for Air Quality Applications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ciren, P.; Liu, H.; Kondragunta, S.; Laszlo, I.</p> <p>2012-12-01</p> <p>Despite pollution reduction control strategies enforced by the Environmental Protection Agency (EPA), large regions of the United States are often under exceptional events such as biomass burning and dust outbreaks that lead to non-attainment of particulate matter standards. This has warranted the National Weather Service (NWS) to provide smoke and dust forecast guidance to the general public. The monitoring and forecasting of dust outbreaks relies on satellite data. Currently, <span class="hlt">Aqua/MODIS</span> (MODerate resolution Imaging Spectrometer) and Terra/<span class="hlt">MODIS</span> provide measurements needed to derive dust mask and Aerosol Optical Thickness (AOT) products. The newly launched Suomi NPP VIIRS (Visible/Infrared Imaging Radiometer Suite) instrument has a Suspended Matter (SM) product that indicates the presence of dust, smoke, volcanic ash, sea salt, and unknown aerosol types in a given pixel. The algorithm to identify dust is different over land and ocean but for both, the information comes from AOT retrieval algorithm. Over land, the selection of dust aerosol model in the AOT retrieval algorithm indicates the presence of dust and over ocean a fine mode fraction smaller than 20% indicates dust. Preliminary comparisons of VIIRS SM to CALIPSO Vertical Feature Mask (VFM) aerosol type product indicate that the Probability of Detection (POD) is at ~10% and the product is not mature for operational use. As an alternate approach, NESDIS dust mask algorithm developed for NWS dust forecast verification that uses <span class="hlt">MODIS</span> deep blue, visible, and mid-IR channels using spectral differencing techniques and spatial variability tests was applied to VIIRS radiances. This algorithm relies on the spectral contrast of dust absorption at 412 and 440 nm and an increase in <span class="hlt">reflectivity</span> at 2.13 μm when dust is present in the atmosphere compared to a clear sky. To avoid detecting bright desert surface as airborne dust, the algorithm uses the <span class="hlt">reflectances</span> at 1.24 μm and 2.25 μm to flag bright pixels. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130013087','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130013087"><span id="translatedtitle"><span class="hlt">Aqua</span> 10 Years After Launch</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parkinson, Claire L.</p> <p>2013-01-01</p> <p>A little over ten years ago, in the early morning hours of May 4, 2002, crowds of spectators stood anxiously watching as the Delta II rocket carrying NASA's <span class="hlt">Aqua</span> spacecraft lifted off from its launch pad at Vandenberg Air Force Base in California at 2:55 a.m. The rocket quickly went through a low-lying cloud cover, after which the main portion of the rocket fell to the waters below and the rockets second stage proceeded to carry <span class="hlt">Aqua</span> south across the Pacific, onward over Antarctica, and north to Africa, where the spacecraft separated from the rocket 59.5 minutes after launch. Then, 12.5 minutes later, the solar array unfurled over Europe, and <span class="hlt">Aqua</span> was on its way in the first of what by now have become over 50,000 successful orbits of the Earth.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030032934','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030032934"><span id="translatedtitle"><span class="hlt">MODIS</span> Data from the GES DISC DAAC: Moderate-Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2002-01-01</p> <p>The Goddard Earth Sciences (GES) Distributed Active Archive Center (DAAC) is responsible for the distribution of the Level 1 data, and the higher levels of all Ocean and Atmosphere products (Land products are distributed through the Land Processes (LP) DAAC DAAC, and the Snow and Ice products are distributed though the National Snow and Ice Data Center (NSIDC) DAAC). Ocean products include sea surface temperature (SST), concentrations of chlorophyll, pigment and coccolithophores, fluorescence, absorptions, and primary productivity. Atmosphere products include aerosols, atmospheric water vapor, clouds and cloud masks, and atmospheric profiles from 20 layers. While most <span class="hlt">MODIS</span> data products are archived in the Hierarchical Data Format-Earth Observing System (HDF-EOS 2.7) format, the ocean binned products and primary productivity products (Level 4) are in the native HDF4 format. <span class="hlt">MODIS</span> Level 1 and 2 data are of the Swath type and are packaged in files representing five minutes of Files for Level 3 and 4 are global products at daily, weekly, monthly or yearly resolutions. Apart from the ocean binned and Level 4 products, these are in Grid type, and the maps are in the Cylindrical Equidistant projection with rectangular grid. Terra viewing (scenes of approximately 2000 by 2330 km). <span class="hlt">MODIS</span> data have several levels of maturity. Most products are released with a provisional level of maturity and only announced as validated after rigorous testing by the <span class="hlt">MODIS</span> Science Teams. <span class="hlt">MODIS</span>/Terra Level 1, and all <span class="hlt">MODIS</span>/Terra 11 micron SST products are announced as validated. At the time of this publication, the <span class="hlt">MODIS</span> Data Support Team (MDST) is working with the Ocean Science Team toward announcing the validated status of the remainder of <span class="hlt">MODIS</span>/Terra Ocean products. <span class="hlt">MODIS/Aqua</span> Level 1 and cloud mask products are released with provisional maturity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AMTD....8.6877L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AMTD....8.6877L"><span id="translatedtitle">Towards a long-term global aerosol optical depth record: applying a consistent aerosol retrieval algorithm to <span class="hlt">MODIS</span> and VIIRS-observed <span class="hlt">reflectance</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Levy, R. C.; Munchak, L. A.; Mattoo, S.; Patadia, F.; Remer, L. A.; Holz, R. E.</p> <p>2015-07-01</p> <p>To answer fundamental questions about aerosols in our changing climate, we must quantify both the current state of aerosols and how they are changing. Although NASA's Moderate resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) sensors have provided quantitative information about global aerosol optical depth (AOD) for more than a decade, this period is still too short to create an aerosol climate data record (CDR). The Visible Infrared Imaging Radiometer Suite (VIIRS) was launched on the Suomi-NPP satellite in late 2011, with additional copies planned for future satellites. Can the <span class="hlt">MODIS</span> aerosol data record be continued with VIIRS to create a consistent CDR? When compared to ground-based AERONET data, the VIIRS Environmental Data Record (V_EDR) has similar validation statistics as the <span class="hlt">MODIS</span> Collection 6 (M_C6) product. However, the V_EDR and M_C6 are offset in regards to global AOD magnitudes, and tend to provide different maps of 0.55 μm AOD and 0.55/0.86 μm-based Ångstrom Exponent (AE). One reason is that the retrieval algorithms are different. Using the Intermediate File Format (IFF) for both <span class="hlt">MODIS</span> and VIIRS data, we have tested whether we can apply a single <span class="hlt">MODIS</span>-like (ML) dark-target algorithm on both sensors that leads to product convergence. Except for catering the radiative transfer and aerosol lookup tables to each sensor's specific wavelength bands, the ML algorithm is the same for both. We run the ML algorithm on both sensors between March 2012 and May 2014, and compare monthly mean AOD time series with each other and with M_C6 and V_EDR products. Focusing on the March-April-May (MAM) 2013 period, we compared additional statistics that include global and gridded 1° × 1° AOD and AE, histograms, sampling frequencies, and collocations with ground-based AERONET. Over land, use of the ML algorithm clearly reduces the differences between the <span class="hlt">MODIS</span> and VIIRS-based AOD. However, although global offsets are near zero, some regional biases remain, especially in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AMT.....8.4083L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AMT.....8.4083L"><span id="translatedtitle">Towards a long-term global aerosol optical depth record: applying a consistent aerosol retrieval algorithm to <span class="hlt">MODIS</span> and VIIRS-observed <span class="hlt">reflectance</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Levy, R. C.; Munchak, L. A.; Mattoo, S.; Patadia, F.; Remer, L. A.; Holz, R. E.</p> <p>2015-10-01</p> <p>To answer fundamental questions about aerosols in our changing climate, we must quantify both the current state of aerosols and how they are changing. Although NASA's Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) sensors have provided quantitative information about global aerosol optical depth (AOD) for more than a decade, this period is still too short to create an aerosol climate data record (CDR). The Visible Infrared Imaging Radiometer Suite (VIIRS) was launched on the Suomi-NPP satellite in late 2011, with additional copies planned for future satellites. Can the <span class="hlt">MODIS</span> aerosol data record be continued with VIIRS to create a consistent CDR? When compared to ground-based AERONET data, the VIIRS Environmental Data Record (V_EDR) has similar validation statistics as the <span class="hlt">MODIS</span> Collection 6 (M_C6) product. However, the V_EDR and M_C6 are offset in regards to global AOD magnitudes, and tend to provide different maps of 0.55 μm AOD and 0.55/0.86 μm-based Ångström Exponent (AE). One reason is that the retrieval algorithms are different. Using the Intermediate File Format (IFF) for both <span class="hlt">MODIS</span> and VIIRS data, we have tested whether we can apply a single <span class="hlt">MODIS</span>-like (ML) dark-target algorithm on both sensors that leads to product convergence. Except for catering the radiative transfer and aerosol lookup tables to each sensor's specific wavelength bands, the ML algorithm is the same for both. We run the ML algorithm on both sensors between March 2012 and May 2014, and compare monthly mean AOD time series with each other and with M_C6 and V_EDR products. Focusing on the March-April-May (MAM) 2013 period, we compared additional statistics that include global and gridded 1° × 1° AOD and AE, histograms, sampling frequencies, and collocations with ground-based AERONET. Over land, use of the ML algorithm clearly reduces the differences between the <span class="hlt">MODIS</span> and VIIRS-based AOD. However, although global offsets are near zero, some regional biases remain, especially in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19990004142','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19990004142"><span id="translatedtitle">[<span class="hlt">MODIS</span> Investigation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Abbott, Mark R.</p> <p>1996-01-01</p> <p>The objectives of the last six months were: (1) Complete sensitivity analysis of fluorescence; line height algorithms (2) Deliver fluorescence algorithm code and test data to the University of Miami for integration; (3) Complete analysis of bio-optical data from Southern Ocean cruise; (4) Conduct laboratory experiments based on analyses of field data; (5) Analyze data from bio-optical mooring off Hawaii; (6) Develop calibration/validation plan for <span class="hlt">MODIS</span> fluorescence data; (7) Respond to the Japanese Research Announcement for GLI; and (8) Continue to review plans for EOSDIS and assist ECS contractor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110023024','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110023024"><span id="translatedtitle">Validation of <span class="hlt">MODIS</span> Aerosol Optical Depth Retrievals over a Tropical Urban Site, Pune, India</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>More, Sanjay; Kuman, P. Pradeep; Gupta, Pawan; Devara, P. C. S.; Aher, G. R.</p> <p>2011-01-01</p> <p>In the present paper, <span class="hlt">MODIS</span> (Terra and <span class="hlt">Aqua</span>; level 2, collection 5) derived aerosoloptical depths (AODs) are compared with the ground-based measurements obtained from AERONET (level 2.0) and Microtops - II sun-photometer over a tropical urban station, Pune (18 deg 32'N; 73 deg 49'E, 559 m amsl). This is the first ever systematic validation of the <span class="hlt">MODIS</span> aerosol products over Pune. Analysis of the data indicates that the Terra and <span class="hlt">Aqua</span> <span class="hlt">MODIS</span> AOD retrievals at 550 nm have good correlations with the AERONET and Microtops - II sun-photometer AOD measurements. During winter the linear regression correlation coefficients for <span class="hlt">MODIS</span> products against AERONET measurements are 0.79 for Terra and 0.62 for <span class="hlt">Aqua</span>; however for premonsoon, the corresponding coefficients are 0.78 and 0.74. Similarly, the linear regression correlation coefficients for Microtops measurements against <span class="hlt">MODIS</span> products are 0.72 and 0.93 for Terra and <span class="hlt">Aqua</span> data respectively during winter and are 0.78 and 0.75 during pre-monsoon. On yearly basis in 2008-2009, correlation coefficients for <span class="hlt">MODIS</span> products against AERONET measurements are 0.80 and 0.78 for Terra and <span class="hlt">Aqua</span> respectively while the corresponding coefficients are 0.70 and 0.73 during 2009-2010. The regressed intercepts with <span class="hlt">MODIS</span> vs. AERONET are 0.09 for Terra and 0.05 for <span class="hlt">Aqua</span> during winter whereas their values are 0.04 and 0.07 during pre-monsoon. However, <span class="hlt">MODIS</span> AODs are found to underestimate during winter and overestimate during pre-monsoon with respect to AERONET and Microtops measurements having slopes 0.63 (Terra) and 0.74 (<span class="hlt">Aqua</span>) during winter and 0.97 (Terra) and 0.94 (<span class="hlt">Aqua</span>) during pre-monsoon. Wavelength dependency of Single Scattering Albedo (SSA) shows presence of absorbing and scattering aerosol particles. For winter, SSA decreases with wavelength with the values 0.86 +/- 0.03 at 440 nm and 0.82 +/- 0.04 at 1020nm. In pre-monsoon, it increases with wavelength (SSA is 0.87 +/- 0.02 at 440nm; and 0.88 +/-0.04 at 1020 nm).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20000080269&hterms=aerosols+desert&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Daerosols%2Bdesert','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20000080269&hterms=aerosols+desert&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Daerosols%2Bdesert"><span id="translatedtitle">New Satellite Measurements of Aerosol Direct Radiative Forcing from <span class="hlt">MODIS</span>, MISR, and POLDER</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kaufman, Y.</p> <p>2000-01-01</p> <p>New set of satellites, <span class="hlt">MODIS</span> and MISR launched on EOS-Terra and POLDER launched on ADEOS-1, and scheduled for ADEOS-II and PARASOL in orbit with EOS-<span class="hlt">AQUA</span>, open exciting opportunities to measure aerosol and their radiative forcing of climate. Each of these instruments has a different approach to invert remote sensing data to derive the aerosol properties. <span class="hlt">MODIS</span> is using wide spectral range 0.47-2.1 micron. MISR is using narrower spectral range (0.44 to 0.87 micron) but observing the same spot from 9 different angles along the satellite track. POLDER using similar wavelengths, uses two dimensional view with a wide angle optics and adds polarization to the inversion process. Among these instruments, we expect to measure the global distribution of aerosol, to distinguish small pollution particles from large particles from deserts and ocean spray. We shall try to measure the aerosol absorption of solar radiation, and their refractive index that indicates the effect of liquid water on the aerosol size and interaction with sunlight. The radiation field measured by these instruments in variety of wavelengths and angles, is also used to derive the effect of the aerosol on <span class="hlt">reflection</span> of sunlight spectral fluxes to space. When combined with flux measurements at the ground, it gives a complete characterization of the effect of aerosol on solar illumination, heating in the atmosphere and <span class="hlt">reflection</span> to space.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1045215','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1045215"><span id="translatedtitle">A SOAP Web Service for accessing <span class="hlt">MODIS</span> land product subsets</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>SanthanaVannan, Suresh K; Cook, Robert B; Pan, Jerry Yun; Wilson, Bruce E</p> <p>2011-01-01</p> <p>Remote sensing data from satellites have provided valuable information on the state of the earth for several decades. Since March 2000, the Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) sensor on board NASA s Terra and <span class="hlt">Aqua</span> satellites have been providing estimates of several land parameters useful in understanding earth system processes at global, continental, and regional scales. However, the HDF-EOS file format, specialized software needed to process the HDF-EOS files, data volume, and the high spatial and temporal resolution of <span class="hlt">MODIS</span> data make it difficult for users wanting to extract small but valuable amounts of information from the <span class="hlt">MODIS</span> record. To overcome this usability issue, the NASA-funded Distributed Active Archive Center (DAAC) for Biogeochemical Dynamics at Oak Ridge National Laboratory (ORNL) developed a Web service that provides subsets of <span class="hlt">MODIS</span> land products using Simple Object Access Protocol (SOAP). The ORNL DAAC <span class="hlt">MODIS</span> subsetting Web service is a unique way of serving satellite data that exploits a fairly established and popular Internet protocol to allow users access to massive amounts of remote sensing data. The Web service provides <span class="hlt">MODIS</span> land product subsets up to 201 x 201 km in a non-proprietary comma delimited text file format. Users can programmatically query the Web service to extract <span class="hlt">MODIS</span> land parameters for real time data integration into models, decision support tools or connect to workflow software. Information regarding the <span class="hlt">MODIS</span> SOAP subsetting Web service is available on the World Wide Web (WWW) at http://daac.ornl.gov/modiswebservice.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1811679M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1811679M&link_type=ABSTRACT"><span id="translatedtitle">Global land surface albedo maps from <span class="hlt">MODIS</span> using the Google Earth Engine</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mitraka, Zina; Benas, Nikolaos; Gorelick, Noel; Chrysoulakis, Nektarios</p> <p>2016-04-01</p> <p>The land surface albedo (LSA) is a critical physical variable, which influences the Earth's climate by affecting the energy budget and distribution in the Earth-atmosphere system. Its role is highly significant in both global and local scales; hence, LSA measurements provide a quantitative means for better constraining global and regional scale climate modelling efforts. The Moderate Resolution Imaging Spectroradiometer (<span class="hlt">MODIS</span>) sensor, on board NASA's Terra and <span class="hlt">Aqua</span> platforms, provides the parameters needed for the computation of LSA on an 8-day temporal scale and a variety of spatial scales (ranging between 0.5 - 5 km). This dataset was used here for the LSA estimation and its changes over the study area at 0.5 km spatial resolution. More specifically, the <span class="hlt">MODIS</span> albedo product was used, which includes both the directional-hemispherical surface <span class="hlt">reflectance</span> (black-sky albedo) and the bi-hemispherical surface <span class="hlt">reflectance</span> (white-sky albedo). The LSA was estimated for the whole globe on an 8-day basis for the whole time period covered by <span class="hlt">MODIS</span> acquisitions (i.e. 2000 until today). To estimate LSA from black-sky and white-sky albedos, the fraction of the diffused radiation is needed, a function of the Aerosol Optical Thickness (AOT). Required AOT information was acquired from the <span class="hlt">MODIS</span> AOT product at 1̊ × 1̊ spatial resolution. Since LSA also depends on solar zenith angle (SZA), 8-day mean LSA values were computed as averages of corresponding LSA values for representative SZAs covering the 24-hour day. The estimated LSA was analysed in terms of both spatial and seasonal characteristics, while LSA changes during the period examined were assessed. All computation were performed using the Google Earth Engine (GEE). The GEE provided access to all the <span class="hlt">MODIS</span> products needed for the analysis without the need of searching or downloading. Moreover, the combination of <span class="hlt">MODIS</span> products in both temporal and spatial terms was fast and effecting using the GEE API (Application</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120002030','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120002030"><span id="translatedtitle">Analysis of Co-Located <span class="hlt">MODIS</span> and CALIPSO Observations Near Clouds</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Varnai, Tamas; Marshak, Alexander</p> <p>2011-01-01</p> <p>The purpose of this paper is to help researchers combine data from different satellites and thus gain new insights into two critical yet poorly understood aspects of anthropogenic climate change, aerosol-cloud interactions and aerosol radiative effects, For this, the paper explores whether cloud information from the <span class="hlt">Aqua</span> satellite's <span class="hlt">MODIS</span> instrument can help characterize systematic aerosol changes near clouds by refining earlier perceptions of these changes that were based on the CALIPSO satellite's CALIOP instrument. Similar to a radar but using visible and ncar-infrared light, CALIOP sends out laser pulses and provides aerosol and cloud information along a single line that tracks the satellite orbit by measuring the <span class="hlt">reflection</span> of its pulses. In contrast, <span class="hlt">MODIS</span> takes images of <span class="hlt">reflected</span> sunlight and emitted infrared radiation at several wavelengths, and covers wide areas around the satellite track. This paper analyzes a year-long global dataset covering all ice-free oceans, and finds that <span class="hlt">MODIS</span> can greatly help the interpretation of CALIOP observations, especially by detecting clouds that lie outside the line observed by CALlPSO. The paper also finds that complications such as differences in view direction or clouds drifting in the 72 seconds that elapse between <span class="hlt">MODIS</span> and CALIOP observations have only a minor impact. The study also finds that <span class="hlt">MODIS</span> data helps refine but does not qualitatively alter perceptions of the systematic aerosol changes that were detected in earlier studies using only CALIOP data. It then proposes a statistical approach to account for clouds lying outside the CALIOP track even when <span class="hlt">MODIS</span> cannot as reliably detect low clouds, for example at night or over ice. Finally, the paper finds that, because of variations in cloud amount and type, the typical distance to clouds in maritime clear areas varies with season and location. The overall median distance to clouds in maritime clear areas around 4-5 km. The fact that half of all clear areas is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980236657','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980236657"><span id="translatedtitle">[<span class="hlt">MODIS</span> Investigation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Abbott, Mark R.</p> <p>1996-01-01</p> <p>Our first activity is based on delivery of code to Bob Evans (University of Miami) for integration and eventual delivery to the <span class="hlt">MODIS</span> Science Data Support Team. As we noted in our previous semi-annual report, coding required the development and analysis of an end-to-end model of fluorescence line height (FLH) errors and sensitivity. This model is described in a paper in press in Remote Sensing of the Environment. Once the code was delivered to Miami, we continue to use this error analysis to evaluate proposed changes in <span class="hlt">MODIS</span> sensor specifications and performance. Simply evaluating such changes on a band by band basis may obscure the true impacts of changes in sensor performance that are manifested in the complete algorithm. This is especially true with FLH that is sensitive to band placement and width. The error model will be used by Howard Gordon (Miami) to evaluate the effects of absorbing aerosols on the FLH algorithm performance. Presently, FLH relies only on simple corrections for atmospheric effects (viewing geometry, Rayleigh scattering) without correcting for aerosols. Our analysis suggests that aerosols should have a small impact relative to changes in the quantum yield of fluorescence in phytoplankton. However, the effect of absorbing aerosol is a new process and will be evaluated by Gordon.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_13");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. Their policies may differ from this site.</small> </div> </center> <div id="footer-wrapper"> <div class="footer-content"> <div id="footerOSTI" class=""> <div class="row"> <div class="col-md-4 text-center col-md-push-4 footer-content-center"><small><a href="http://www.science.gov/disclaimer.html">Privacy and Security</a></small> <div class="visible-sm visible-xs push_footer"></div> </div> <div class="col-md-4 text-center col-md-pull-4 footer-content-left"> <img src="http://www.osti.gov/images/DOE_SC31.png" alt="U.S. Department of Energy" usemap="#doe" height="31" width="177"><map style="display:none;" name="doe" id="doe"><area shape="rect" coords="1,3,107,30" href="http://www.energy.gov" alt="U.S. Deparment of Energy"><area shape="rect" coords="114,3,165,30" href="http://www.science.energy.gov" alt="Office of Science"></map> <a ref="http://www.osti.gov" style="margin-left: 15px;"><img src="http://www.osti.gov/images/footerimages/ostigov53.png" alt="Office of Scientific and Technical Information" height="31" width="53"></a> <div class="visible-sm visible-xs push_footer"></div> </div> <div class="col-md-4 text-center footer-content-right"> <a href="http://www.osti.gov/nle"><img src="http://www.osti.gov/images/footerimages/NLElogo31.png" alt="National Library of Energy" height="31" width="79"></a> <a href="http://www.science.gov"><img src="http://www.osti.gov/images/footerimages/scigov77.png" alt="science.gov" height="31" width="98"></a> <a href="http://worldwidescience.org"><img src="http://www.osti.gov/images/footerimages/wws82.png" alt="WorldWideScience.org" height="31" width="90"></a> </div> </div> </div> </div> </div> <p><br></p> </div><!-- container --> </body> </html>