The Experts below are selected from a list of 1410 Experts worldwide ranked by ideXlab platform
Changyong Cao - One of the best experts on this subject based on the ideXlab platform.
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Mission-Long Recalibrated Science Quality Suomi npp VIIRS Radiometric Dataset Using Advanced Algorithms for Time Series Studies
Remote Sensing, 2021Co-Authors: Changyong Cao, Yan Bai, Wenhui Wang, Taeyoung Choi, Slawomir Blonski, Xi Shao, Bin Zhang, Sirish Uprety, Lin LinAbstract:Suomi npp has been successfully operating since its launch on 28 October 2011. As one of the major payloads, along with microwave and infrared sounders (Advanced Technology Microwave Sounder (ATMS), Cross-track Infrared Sounder (CrIS)), and ozone mapping/profiling (OMPS) instruments, the Visible Infrared Imaging Radiometer Suite (VIIRS) has performed for well beyond its mission design life. Its data have been used for a variety of applications for nearly 30 environmental data products, including global imagery twice daily with 375 and 750 m resolutions, clouds, aerosol, cryosphere, ocean color and sea-surface temperature, a number of land products (vegetation, land-cover, fire and others), and geophysical and social economic studies with nightlights. During the early days of VIIRS operational calibration and data production, there were inconsistencies in both algorithms and calibration inputs, for several reasons. While these inconsistencies have less impact on nowcasting and near real-time applications, they introduce challenges for time series analysis due to calibration artifacts. To address this issue, we developed a comprehensive algorithm, and recalibrated and reprocessed the Suomi npp VIIRS radiometric data that have been produced since the launch. In the recalibration, we resolved inconsistencies in the processing algorithms, terrain correction, straylight correction, and anomalies in the thermal bands. To improve the stability of the reflective solar bands, we developed a Kalman filtering model to incorporate onboard solar, lunar, desert site, inter-satellite calibration, and a deep convective cloud calibration methodology. We further developed and implemented the Solar Diffuser Surface Roughness Rayleigh Scattering model to account for the sensor responsivity degradation in the near infrared bands. The recalibrated dataset was validated using vicarious sites and alternative methods, and compared with independent processing from other organizations. The recalibrated radiometric dataset (namely, the level 1b or sensor data records) also incorporates a bias correction for the reflective solar bands, which not only addresses known calibration biases, but also allows alternative calibrations to be applied if so desired. The recalibrated data have been proven to be of high quality, with much improved stability (better than 0.3%) and accuracy (by up to 2%). The recalibrated radiance data are now available from 2012 to 2020 for users and will eventually be archived on the NOAA CLASS database.
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The Reprocessed Suomi npp Satellite Observations
Remote Sensing, 2020Co-Authors: Cheng-zhi Zou, Changyong Cao, Lin Lin, Ninghai Sun, Bin Zhang, Yong Chen, Lawrence E. Flynn, Lihang Zhou, Flavio Iturbide-sanchez, Trevor BeckAbstract:The launch of the National Oceanic and Atmospheric Administration (NOAA)/ National Aeronautics and Space Administration (NASA) Suomi National Polar-orbiting Partnership (S-npp) and its follow-on NOAA Joint Polar Satellite Systems (JPSS) satellites marks the beginning of a new era of operational satellite observations of the Earth and atmosphere for environmental applications with high spatial resolution and sampling rate. The S-npp and JPSS are equipped with five instruments, each with advanced design in Earth sampling, including the Advanced Technology Microwave Sounder (ATMS), the Cross-track Infrared Sounder (CrIS), the Ozone Mapping and Profiler Suite (OMPS), the Visible Infrared Imaging Radiometer Suite (VIIRS), and the Clouds and the Earth’s Radiant Energy System (CERES). Among them, the ATMS is the new generation of microwave sounder measuring temperature profiles from the surface to the upper stratosphere and moisture profiles from the surface to the upper troposphere, while CrIS is the first of a series of advanced operational hyperspectral sounders providing more accurate atmospheric and moisture sounding observations with higher vertical resolution for weather and climate applications. The OMPS instrument measures solar backscattered ultraviolet to provide information on the concentrations of ozone in the Earth’s atmosphere, and VIIRS provides global observations of a variety of essential environmental variables over the land, atmosphere, cryosphere, and ocean with visible and infrared imagery. The CERES instrument measures the solar energy reflected by the Earth, the longwave radiative emission from the Earth, and the role of cloud processes in the Earth’s energy balance. Presently, observations from several instruments on S-npp and JPSS-1 (re-named NOAA-20 after launch) provide near real-time monitoring of the environmental changes and improve weather forecasting by assimilation into numerical weather prediction models. Envisioning the need for consistencies in satellite retrievals, improving climate reanalyses, development of climate data records, and improving numerical weather forecasting, the NOAA/Center for Satellite Applications and Research (STAR) has been reprocessing the S-npp observations for ATMS, CrIS, OMPS, and VIIRS through their life cycle. This article provides a summary of the instrument observing principles, data characteristics, reprocessing approaches, calibration algorithms, and validation results of the reprocessed sensor data records. The reprocessing generated consistent Level-1 sensor data records using unified and consistent calibration algorithms for each instrument that removed artificial jumps in data owing to operational changes, instrument anomalies, contaminations by anomaly views of the environment or spacecraft, and other causes. The reprocessed sensor data records were compared with and validated against other observations for a consistency check whenever such data were available. The reprocessed data will be archived in the NOAA data center with the same format as the operational data and technical support for data requests. Such a reprocessing is expected to improve the efficiency of the use of the S-npp and JPSS satellite data and the accuracy of the observed essential environmental variables through either consistent satellite retrievals or use of the reprocessed data in numerical data assimilations.
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Radiometric Inter-Consistency of VIIRS DNB on Suomi npp and NOAA-20 from Observations of Reflected Lunar Lights over Deep Convective Clouds
MDPI AG, 2019Co-Authors: Changyong Cao, Yan Bai, Wenhui Wang, Taeyoung ChoiAbstract:The Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band (DNB) is capable of observing reflected lunar radiances at night with its high gain stage (HGS), and the radiometric calibration is traceable to the sun through gain transfer from the low gain stage (LGS) calibrated near the terminator with the solar diffuser. Meanwhile, deep convective clouds (DCC) are known to have a stable reflectance in the visible spectral range. Therefore, the reflected lunar radiance at night from the DCC provides a unique dataset for the inter-calibration of VIIRS DNB on different satellites such as Suomi National Polar-orbiting Partnership (npp) and NOAA-20, as well as quantifying the lunar radiance as a function of lunar phase angle. This study demonstrates a methodology for comparing nighttime Suomi npp and NOAA-20 VIIRS DNB measured DCC reflected lunar radiance at various phase angles using data from July 2018 to March 2019 with an 86 second sampling interval and comparing Suomi npp VIIRS DNB measured lunar radiances with those from lunar model predictions. The result shows good consistency between these two instruments on the two satellites, although a low bias in the NOAA-20 VIIRS DNB of ~5% is found. Also, observed lunar radiance from VIIRS DNB on Suomi npp is found to be consistent with model predictions within 3% ± 5% (1σ) for a large range of lunar phase angles. However, discrepancies are significant near full moon, due to lunar opposition effects, and limitations of the lunar models. This study is useful not only for monitoring the DNB calibration stability and consistency across satellites, but also may help validate lunar models independently
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the effects of viirs spectral response differences between Suomi npp and noaa 20 for the thermal emissive bands
International Geoscience and Remote Sensing Symposium, 2018Co-Authors: Lin Lin, Changyong CaoAbstract:The NOAA-20 satellite was successfully launched on November 18,2017 into an afternoon orbit with local equator crossing time ~1: 30pm, in the same orbital plane as that of the Suomi National Polar-orbiting Partnership (npp) but with a time separation of half an orbit or ~50 minutes. The Visible Infrared Imaging Radiometer Suite (VIIRS) onboard NOAA-20 will become the primary operational imager succeeding the VIIRS onboard Suomi npp which has been in-orbit for more than six years. Although the VIIRS onboard Suomi npp and NOAA-20 have identical design, there are small differences in the relative spectral response (RSR) in most bands. Previous studies have shown that minor differences in RSR can lead to a number of effects at detector level, such as striping. This study investigates the VIIRS RSR differences between Suomi npp and NOAA-20 for the Thermal Emissive Bands (TEB) including M12-M16. The Line-By-Line radiative transfer model (LBLRTM) is used at very high spectral resolution for convolving with the RSR of VIIRS on both satellites. The impact of RSR difference between Suomi npp and NOAA-20 are evaluated for radiometric biases and potential striping in TEB. This study will contribute to the measurement consistency for the long term observations in the thermal infrared bands, and ensure the quality of the data produced by VIIRS, such as sea surface temperature (SST), fire and other retrievals.
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IGARSS - The Effects of VIIRS Spectral Response Differences between Suomi npp and NOAA-20 for the Thermal Emissive Bands
IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium, 2018Co-Authors: Lin Lin, Changyong CaoAbstract:The NOAA-20 satellite was successfully launched on November 18,2017 into an afternoon orbit with local equator crossing time ~1: 30pm, in the same orbital plane as that of the Suomi National Polar-orbiting Partnership (npp) but with a time separation of half an orbit or ~50 minutes. The Visible Infrared Imaging Radiometer Suite (VIIRS) onboard NOAA-20 will become the primary operational imager succeeding the VIIRS onboard Suomi npp which has been in-orbit for more than six years. Although the VIIRS onboard Suomi npp and NOAA-20 have identical design, there are small differences in the relative spectral response (RSR) in most bands. Previous studies have shown that minor differences in RSR can lead to a number of effects at detector level, such as striping. This study investigates the VIIRS RSR differences between Suomi npp and NOAA-20 for the Thermal Emissive Bands (TEB) including M12-M16. The Line-By-Line radiative transfer model (LBLRTM) is used at very high spectral resolution for convolving with the RSR of VIIRS on both satellites. The impact of RSR difference between Suomi npp and NOAA-20 are evaluated for radiometric biases and potential striping in TEB. This study will contribute to the measurement consistency for the long term observations in the thermal infrared bands, and ensure the quality of the data produced by VIIRS, such as sea surface temperature (SST), fire and other retrievals.
Xiaoxiong Xiong - One of the best experts on this subject based on the ideXlab platform.
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Suomi-npp VIIRS unscheduled lunar observations
Sensors Systems and Next-Generation Satellites XX, 2016Co-Authors: Zhipeng Wang, Xiaoxiong Xiong, Jon FulbrightAbstract:Lunar observations by the Suomi-npp instrument VIIRS are scheduled on a nearly monthly basis at a phase angle of approximately -51 degrees. The lunar images acquired during scheduled observations have been used for radiometric calibration stability monitoring of the reflective solar bands, band-to-band registration characterization, modulation transfer function derivation and electric crosstalk examination. A satellite roll maneuver is usually necessary for the Moon to be viewed by VIIRS detectors, which results in the loss of approximately 20-minute science data during the period. Without any scheduling, the Moon has also been regularly observed when it intrudes the field of view of the instrument’s space view port. Since the launch of Suomi-npp in late 2011, nearly 200 unscheduled lunar observations have been made with complete lunar images captured by at least two spectral bands. These observations are made at a larger phase angle from -45 to -90 degrees and libration angle range than the scheduled lunar observation. In this paper, the strategies and methodologies of lunar calibration developed for scheduled lunar observations are applied to these unscheduled lunar observations, with necessary adaptation to account for the differences in data format. The result from the unscheduled lunar observations are provided, with the focus of it comparison with the results from scheduled lunar observations as well as solar diffuser (SD) calibration. Overall, the long-term trends of these results agree with each other and the trends from the un-scheduled lunar calibration show more fluctuation. For radiometric calibration, the difference between the lunar calibration and SD calibration strongly depends on phase angles and libration angles. If the VIIRS measurement is accurate, this indicates that the lunar irradiance reference for the radiometric calibration, modeled by the USGS robotic lunar observatory (ROLO), carries systematic error that changes with these photometric factors. An empirical correction is applied to derive the relationship between the error and the phase angle to compensate the impact. The trends after the correction shows much less fluctuation to a level similar to the trends from scheduled calibration..
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Suomi npp viirs solar diffuser stability monitor performance
IEEE Transactions on Geoscience and Remote Sensing, 2016Co-Authors: Jon Fulbright, Boryana Efremova, Xiaoxiong XiongAbstract:When illuminated by the Sun, the onboard solar diffuser (SD) panel provides a known spectral radiance source to calibrate the reflective solar bands of the Visible Infrared Imaging Radiometer Suite on the Suomi-npp satellite. The SD bidirectional reflectance distribution function (BRDF) degrades over time due to solar exposure, and this degradation is measured using the SD stability monitor (SDSM). The SDSM acts as a ratioing radiometer, comparing solar irradiance measurements off the SD panel to those from a direct Sun view. We discuss the design and operations of the SDSM, the SDSM data analysis, including improvements incorporated since launch, and present the results through 1000 days after launch. After 1000 days, the band-dependent H-factors, a quantity describing the relative degradation of the BRDF of the SD panel since launch, range from 0.716 at 412 nm to 0.989 at 926 nm. The random uncertainty of these H-factors is about 0.1%, which is confirmed by the similar standard deviation values computed from the residuals of quadratic exponential fits to the H-factor time trends. The SDSM detector gains have temperature sensitivity of up to about 0.36% per kelvin, but this does not affect the derived H-factors. An initial error in the solar vector caused a seasonal bias to the H-factors of up to 0.5%. The total exposure of the SD panel to UV light after 1000 orbits is equivalent to about 100 h of direct sunlight illumination perpendicular to the SD panel surface.
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Suomi npp viirs day night band calibration with stars
Proceedings of SPIE, 2015Co-Authors: Jon Fulbright, Xiaoxiong XiongAbstract:Observations of stars can be used to calibrate the radiometric performance of the Day/Night Band (DNB) of the Suomi-npp instrument VIIRS. Bright stars are normally visible in the Space View window. In this paper, we describe several potential applications of stellar observations with preliminary results for several. These applications include routine trending of the gain of the highand mid-gain stages of the DNB and trending the gain ratio between those stages. Many of the stars observed by the VIIRS DNB have absolute flux curves available, allowing for an absolute calibration. Additionally, stars are visible during scheduled lunar roll observations. The electronic sector rotations applied during the scheduled lunar observations greatly increases the sky area recorded for a brief period, increasing the observing opportunities. Additionally, the DNB recorded data during the spacecraft pitch maneuver. This means the deep sky was viewed through the full Earth View. In this situation, thousands of stars (and the planet Mars) are recorded over a very short time period and over all aggregation zones. A possible application would be to create a gain curve by comparing the instrument response to the known apparent stellar brightness for a large number of stars of similar spectral shape. Finally, the DNB is especially affected the mirror degradation afflicting VIIRS. The degradation has shifted peak of the relative spectral response (RSR) of the DNB the blue and the effective band pass has been slightly reduced. The change in response for hot stars (effective temperatures of over 30,000 K) due to this degradation will differ by about 10 percent from the response change of cool stars (below 3500 K).
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Earth Observing Systems - Suomi-npp VIIRS day/night band calibration with stars
Earth Observing Systems XX, 2015Co-Authors: Jon Fulbright, Xiaoxiong XiongAbstract:Observations of stars can be used to calibrate the radiometric performance of the Day/Night Band (DNB) of the Suomi-npp instrument VIIRS. Bright stars are normally visible in the Space View window. In this paper, we describe several potential applications of stellar observations with preliminary results for several. These applications include routine trending of the gain of the highand mid-gain stages of the DNB and trending the gain ratio between those stages. Many of the stars observed by the VIIRS DNB have absolute flux curves available, allowing for an absolute calibration. Additionally, stars are visible during scheduled lunar roll observations. The electronic sector rotations applied during the scheduled lunar observations greatly increases the sky area recorded for a brief period, increasing the observing opportunities. Additionally, the DNB recorded data during the spacecraft pitch maneuver. This means the deep sky was viewed through the full Earth View. In this situation, thousands of stars (and the planet Mars) are recorded over a very short time period and over all aggregation zones. A possible application would be to create a gain curve by comparing the instrument response to the known apparent stellar brightness for a large number of stars of similar spectral shape. Finally, the DNB is especially affected the mirror degradation afflicting VIIRS. The degradation has shifted peak of the relative spectral response (RSR) of the DNB the blue and the effective band pass has been slightly reduced. The change in response for hot stars (effective temperatures of over 30,000 K) due to this degradation will differ by about 10 percent from the response change of cool stars (below 3500 K).
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Overview of Suomi npp VIIRS performance in the last 2.5 years
Earth Observing Missions and Sensors: Development Implementation and Characterization III, 2014Co-Authors: Changyong Cao, Yan Bai, Wenhui Wang, Slawomir Blonski, Xi Shao, Tayoung Choi, Xiaoxiong XiongAbstract:Since the successful launch of the Suomi npp on October 28, 2011, the VIIRS instrument has performed well in general. This paper provides an overview of the evolution of the VIIRS instrument performance, major events experienced in the nearly three years since launch, and the ground processing system changes to account for various effects and discrepancies. The mirror degradation in the near-infrared bands due to prelaunch mirror contamination has been gradually leveling off, although the degradation in the solar diffuser continues. In the ground processing, many changes have been implemented in the operational code. This includes the stray-light correction for the Day/Night band, the automatic calibration for the reflective solar band, and corrections for several errors in the code, and resolving various discrepancies in the calibration equations and coefficients. The scientific community is generally satisfied with the quality of the VIIRS SDR data. However, there are remaining issues to be resolved through further research and development. These issues include meeting the more stringent requirement and desire for ocean color applications, better understanding of the polarization effects especially off-nadir, understanding and resolving inconsistencies between solar and lunar calibration. The Suomi npp VIIRS SDR has been used for generating a variety of products with great success by worldwide users. Together with the follow-on instruments J1 and J2, VIIRS will be the primary data source for moderate resolution satellite observations in the next decades.
Zoltán Kolláth - One of the best experts on this subject based on the ideXlab platform.
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angular distribution of upwelling artificial light in europe as observed by Suomi npp satellite
Journal of Quantitative Spectroscopy & Radiative Transfer, 2020Co-Authors: Kai Pong Tong, Christopher C. M. Kyba, Georg Heygster, Helga U. Kuechly, Justus Notholt, Zoltán KolláthAbstract:Abstract Measuring the angular distribution of upwelling artificial light is important for modeling light pollution, because the direction of emission affects how light propagates in the atmosphere. We characterize the angular distributions of upwelling artificial light for Europe and northern Africa in 2018, based on night time radiance data for clear nights without twilight and moonlight from the VIIRS–DNB sensor on board the Suomi npp satellite. We find that in general, suburban areas of major cities emit more light at larger zenith angles, whereas the opposite can be seen at the city centers, where the highest radiance is directed upward. The mean numbers of overflights for the year is 83, meaning that there are on average approximately seven suitable overflights per month. Future analysis may consider using moonlight models to compensate for the retrieval of moonlit scenes and analyzing data from different years in order to expand the amount of available data. As the VIIRS–DNB sensor on board the NOAA–20 satellite (launched 2017) has almost the same design, this method can also be extended to the data taken by NOAA–20.
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Angular distribution of upwelling artificial light in Europe as observed by Suomi–npp satellite
Journal of Quantitative Spectroscopy and Radiative Transfer, 2020Co-Authors: Kai Pong Tong, Christopher C. M. Kyba, Georg Heygster, Helga U. Kuechly, Justus Notholt, Zoltán KolláthAbstract:Abstract Measuring the angular distribution of upwelling artificial light is important for modeling light pollution, because the direction of emission affects how light propagates in the atmosphere. We characterize the angular distributions of upwelling artificial light for Europe and northern Africa in 2018, based on night time radiance data for clear nights without twilight and moonlight from the VIIRS–DNB sensor on board the Suomi npp satellite. We find that in general, suburban areas of major cities emit more light at larger zenith angles, whereas the opposite can be seen at the city centers, where the highest radiance is directed upward. The mean numbers of overflights for the year is 83, meaning that there are on average approximately seven suitable overflights per month. Future analysis may consider using moonlight models to compensate for the retrieval of moonlit scenes and analyzing data from different years in order to expand the amount of available data. As the VIIRS–DNB sensor on board the NOAA–20 satellite (launched 2017) has almost the same design, this method can also be extended to the data taken by NOAA–20.
Jon Fulbright - One of the best experts on this subject based on the ideXlab platform.
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Suomi-npp VIIRS unscheduled lunar observations
Sensors Systems and Next-Generation Satellites XX, 2016Co-Authors: Zhipeng Wang, Xiaoxiong Xiong, Jon FulbrightAbstract:Lunar observations by the Suomi-npp instrument VIIRS are scheduled on a nearly monthly basis at a phase angle of approximately -51 degrees. The lunar images acquired during scheduled observations have been used for radiometric calibration stability monitoring of the reflective solar bands, band-to-band registration characterization, modulation transfer function derivation and electric crosstalk examination. A satellite roll maneuver is usually necessary for the Moon to be viewed by VIIRS detectors, which results in the loss of approximately 20-minute science data during the period. Without any scheduling, the Moon has also been regularly observed when it intrudes the field of view of the instrument’s space view port. Since the launch of Suomi-npp in late 2011, nearly 200 unscheduled lunar observations have been made with complete lunar images captured by at least two spectral bands. These observations are made at a larger phase angle from -45 to -90 degrees and libration angle range than the scheduled lunar observation. In this paper, the strategies and methodologies of lunar calibration developed for scheduled lunar observations are applied to these unscheduled lunar observations, with necessary adaptation to account for the differences in data format. The result from the unscheduled lunar observations are provided, with the focus of it comparison with the results from scheduled lunar observations as well as solar diffuser (SD) calibration. Overall, the long-term trends of these results agree with each other and the trends from the un-scheduled lunar calibration show more fluctuation. For radiometric calibration, the difference between the lunar calibration and SD calibration strongly depends on phase angles and libration angles. If the VIIRS measurement is accurate, this indicates that the lunar irradiance reference for the radiometric calibration, modeled by the USGS robotic lunar observatory (ROLO), carries systematic error that changes with these photometric factors. An empirical correction is applied to derive the relationship between the error and the phase angle to compensate the impact. The trends after the correction shows much less fluctuation to a level similar to the trends from scheduled calibration..
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Suomi npp viirs solar diffuser stability monitor performance
IEEE Transactions on Geoscience and Remote Sensing, 2016Co-Authors: Jon Fulbright, Boryana Efremova, Xiaoxiong XiongAbstract:When illuminated by the Sun, the onboard solar diffuser (SD) panel provides a known spectral radiance source to calibrate the reflective solar bands of the Visible Infrared Imaging Radiometer Suite on the Suomi-npp satellite. The SD bidirectional reflectance distribution function (BRDF) degrades over time due to solar exposure, and this degradation is measured using the SD stability monitor (SDSM). The SDSM acts as a ratioing radiometer, comparing solar irradiance measurements off the SD panel to those from a direct Sun view. We discuss the design and operations of the SDSM, the SDSM data analysis, including improvements incorporated since launch, and present the results through 1000 days after launch. After 1000 days, the band-dependent H-factors, a quantity describing the relative degradation of the BRDF of the SD panel since launch, range from 0.716 at 412 nm to 0.989 at 926 nm. The random uncertainty of these H-factors is about 0.1%, which is confirmed by the similar standard deviation values computed from the residuals of quadratic exponential fits to the H-factor time trends. The SDSM detector gains have temperature sensitivity of up to about 0.36% per kelvin, but this does not affect the derived H-factors. An initial error in the solar vector caused a seasonal bias to the H-factors of up to 0.5%. The total exposure of the SD panel to UV light after 1000 orbits is equivalent to about 100 h of direct sunlight illumination perpendicular to the SD panel surface.
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Suomi npp viirs day night band calibration with stars
Proceedings of SPIE, 2015Co-Authors: Jon Fulbright, Xiaoxiong XiongAbstract:Observations of stars can be used to calibrate the radiometric performance of the Day/Night Band (DNB) of the Suomi-npp instrument VIIRS. Bright stars are normally visible in the Space View window. In this paper, we describe several potential applications of stellar observations with preliminary results for several. These applications include routine trending of the gain of the highand mid-gain stages of the DNB and trending the gain ratio between those stages. Many of the stars observed by the VIIRS DNB have absolute flux curves available, allowing for an absolute calibration. Additionally, stars are visible during scheduled lunar roll observations. The electronic sector rotations applied during the scheduled lunar observations greatly increases the sky area recorded for a brief period, increasing the observing opportunities. Additionally, the DNB recorded data during the spacecraft pitch maneuver. This means the deep sky was viewed through the full Earth View. In this situation, thousands of stars (and the planet Mars) are recorded over a very short time period and over all aggregation zones. A possible application would be to create a gain curve by comparing the instrument response to the known apparent stellar brightness for a large number of stars of similar spectral shape. Finally, the DNB is especially affected the mirror degradation afflicting VIIRS. The degradation has shifted peak of the relative spectral response (RSR) of the DNB the blue and the effective band pass has been slightly reduced. The change in response for hot stars (effective temperatures of over 30,000 K) due to this degradation will differ by about 10 percent from the response change of cool stars (below 3500 K).
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Earth Observing Systems - Suomi-npp VIIRS day/night band calibration with stars
Earth Observing Systems XX, 2015Co-Authors: Jon Fulbright, Xiaoxiong XiongAbstract:Observations of stars can be used to calibrate the radiometric performance of the Day/Night Band (DNB) of the Suomi-npp instrument VIIRS. Bright stars are normally visible in the Space View window. In this paper, we describe several potential applications of stellar observations with preliminary results for several. These applications include routine trending of the gain of the highand mid-gain stages of the DNB and trending the gain ratio between those stages. Many of the stars observed by the VIIRS DNB have absolute flux curves available, allowing for an absolute calibration. Additionally, stars are visible during scheduled lunar roll observations. The electronic sector rotations applied during the scheduled lunar observations greatly increases the sky area recorded for a brief period, increasing the observing opportunities. Additionally, the DNB recorded data during the spacecraft pitch maneuver. This means the deep sky was viewed through the full Earth View. In this situation, thousands of stars (and the planet Mars) are recorded over a very short time period and over all aggregation zones. A possible application would be to create a gain curve by comparing the instrument response to the known apparent stellar brightness for a large number of stars of similar spectral shape. Finally, the DNB is especially affected the mirror degradation afflicting VIIRS. The degradation has shifted peak of the relative spectral response (RSR) of the DNB the blue and the effective band pass has been slightly reduced. The change in response for hot stars (effective temperatures of over 30,000 K) due to this degradation will differ by about 10 percent from the response change of cool stars (below 3500 K).
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Suomi npp viirs lunar radiometric calibration observations
Proceedings of SPIE, 2014Co-Authors: Jon Fulbright, Zhipeng Wang, Xiaoxiong XiongAbstract:Lunar observations by the Suomi-npp instrument VIIRS help improve our understanding of the radiometric calibration of the reflected solar bands (RSB). The spacecraft performs a scheduled roll maneuver approximately nine times per year to acquire lunar data at nearly constant phase angles. The instrument also captures lunar radiometric data at other times when the instrument Space View port serendipitously points at the Moon. In this paper, we present results only from the scheduled Moon observations, comparing the observed lunar irradiance to ROLO model results to provide calibration coefficients for each band, mirror side, and detector. These results can be evaluated directly to the primary RSB calibration method derived from the Solar Diffuser. This paper also discusses recent improvements to our methodology for measuring the lunar irradiance, including a new method for determining the lunar position within the field of view, an all-detector calibration methodology, and an assessment of the uncertainties in our lunar observations. This paper includes lunar observation data through June 2014.
Xi Shao - One of the best experts on this subject based on the ideXlab platform.
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Mission-Long Recalibrated Science Quality Suomi npp VIIRS Radiometric Dataset Using Advanced Algorithms for Time Series Studies
Remote Sensing, 2021Co-Authors: Changyong Cao, Yan Bai, Wenhui Wang, Taeyoung Choi, Slawomir Blonski, Xi Shao, Bin Zhang, Sirish Uprety, Lin LinAbstract:Suomi npp has been successfully operating since its launch on 28 October 2011. As one of the major payloads, along with microwave and infrared sounders (Advanced Technology Microwave Sounder (ATMS), Cross-track Infrared Sounder (CrIS)), and ozone mapping/profiling (OMPS) instruments, the Visible Infrared Imaging Radiometer Suite (VIIRS) has performed for well beyond its mission design life. Its data have been used for a variety of applications for nearly 30 environmental data products, including global imagery twice daily with 375 and 750 m resolutions, clouds, aerosol, cryosphere, ocean color and sea-surface temperature, a number of land products (vegetation, land-cover, fire and others), and geophysical and social economic studies with nightlights. During the early days of VIIRS operational calibration and data production, there were inconsistencies in both algorithms and calibration inputs, for several reasons. While these inconsistencies have less impact on nowcasting and near real-time applications, they introduce challenges for time series analysis due to calibration artifacts. To address this issue, we developed a comprehensive algorithm, and recalibrated and reprocessed the Suomi npp VIIRS radiometric data that have been produced since the launch. In the recalibration, we resolved inconsistencies in the processing algorithms, terrain correction, straylight correction, and anomalies in the thermal bands. To improve the stability of the reflective solar bands, we developed a Kalman filtering model to incorporate onboard solar, lunar, desert site, inter-satellite calibration, and a deep convective cloud calibration methodology. We further developed and implemented the Solar Diffuser Surface Roughness Rayleigh Scattering model to account for the sensor responsivity degradation in the near infrared bands. The recalibrated dataset was validated using vicarious sites and alternative methods, and compared with independent processing from other organizations. The recalibrated radiometric dataset (namely, the level 1b or sensor data records) also incorporates a bias correction for the reflective solar bands, which not only addresses known calibration biases, but also allows alternative calibrations to be applied if so desired. The recalibrated data have been proven to be of high quality, with much improved stability (better than 0.3%) and accuracy (by up to 2%). The recalibrated radiance data are now available from 2012 to 2020 for users and will eventually be archived on the NOAA CLASS database.
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Comparison of Suomi-npp VIIRS and HIMARWARI-8 AHI MWIR observations for hot spot and heat island studies
2016 IEEE International Geoscience and Remote Sensing Symposium (IGARSS), 2016Co-Authors: Xi Shao, Bin Zhang, Xiangqian Wu, Fangfang YuAbstract:The mid-wavelength infrared (MWIR) imageries of Suomi-npp Visible Infrared Imaging Radiometer Suite (VIIRS) and HIMAWARI-8 Advanced Himawari Imager (AHI) enable monitoring temperature variation of heat sources such as hot spots and urban heat islands. The 3.75 um band of VIIRS provides imagery in high spatial resolution (~375 m) twice a day and can be used to monitor temperature variation of hot spots due to industrial activities. The 3.9 um channel of AHI imagery in 10-minute time resolution enables continuous monitoring of temporal variation of urban heat island temperature. This paper compared using imageries of VIIRS and AHI MWIR channel to monitor both spatial distribution and temporal (seasonal and diurnal) variation of hot spots and urban heat islands. It was shown that the MWIR imageries of VIIRS and AHI complement each other in understanding the spatial structure and temporal variation of social economic activities-related heat sources.
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IGARSS - Comparison of Suomi-npp VIIRS and HIMARWARI-8 AHI MWIR observations for hot spot and heat island studies
2016 IEEE International Geoscience and Remote Sensing Symposium (IGARSS), 2016Co-Authors: Xi Shao, Changyong Cao, Bin Zhang, Yan BaiAbstract:The mid-wavelength infrared (MWIR) imageries of Suomi-npp Visible Infrared Imaging Radiometer Suite (VIIRS) and HIMAWARI-8 Advanced Himawari Imager (AHI) enable monitoring temperature variation of heat sources such as hot spots and urban heat islands. The 3.75 um band of VIIRS provides imagery in high spatial resolution (∼375 m) twice a day and can be used to monitor temperature variation of hot spots due to industrial activities. The 3.9 um channel of AHI imagery in 10-minute time resolution enables continuous monitoring of temporal variation of urban heat island temperature. This paper compared using imageries of VIIRS and AHI MWIR channel to monitor both spatial distribution and temporal (seasonal and diurnal) variation of hot spots and urban heat islands. It was shown that the MWIR imageries of VIIRS and AHI complement each other in understanding the spatial structure and temporal variation of social economic activities-related heat sources.
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Radiometric Stability Monitoring of the Suomi npp Visible Infrared Imaging Radiometer Suite (VIIRS) Reflective Solar Bands Using the Moon
Remote Sensing, 2015Co-Authors: Taeyoung Choi, Changyong Cao, Xi Shao, Fuzhong WengAbstract:The Suomi npp (S-npp) Visible Infrared Imaging Radiometer Suite (VIIRS) performs the scheduled lunar roll maneuver on a monthly basis. The lunar calibration coefficients and lunar F-factor are calculated by taking the ratio of the lunar observed radiance to the simulated radiance from the Miller and Turner (MT) lunar model. The lunar F-factor is also validated against that derived from the VIIRS Solar Diffuser (SD). The MT model-based lunar F-factors in general agree with SD F-factors. The Lunar Band Ratio (LBR) is also derived from two channel lunar radiances and is implemented in the National Oceanic and Atmospheric Administration (NOAA) Integrated Calibration and Validation System (ICVS) to monitor the VIIRS long-term radiometric performance. The lunar radiances at pixels are summed for each of the VIIRS Reflective Solar Bands (RSBs) and normalized by the reference band M11 which has the most stable SD-based calibration coefficient. LBRs agree with the SD based F-factor ratios within one percent. Based on analysis with these two independent lunar calibration methods, SD-based and LBR-based calibrations show a lifetime consistency. Thus, it is recommended that LBR be used for both VIIRS radiometric calibration and lifetime stability monitoring.
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comparison between the Suomi npp day night band and dmsp ols for correlating socio economic variables at the provincial level in china
Remote Sensing, 2015Co-Authors: Xin Jing, Changyong Cao, Xi Shao, Lei YanAbstract:Nighttime light imagery offers a unique view of the Earth’s surface. In the past, the nighttime light data collected by the DMSP-OLS sensors have been used as an efficient means to correlate regional and global socio-economic activities. With the launch of the Suomi National Polar-orbiting Partnership (Suomi-npp) satellite in 2011, the day-night band (DNB) of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard represents a major advancement in nighttime imaging capabilities, because it surpasses its predecessor DMSP-OLS in radiometric accuracy, spatial resolution and geometric quality. In this paper, four variables (total night light, light area, average night light and log average night light) are extracted from nighttime radiance data observed by the VIIRS-DNB composite in 2013 and nighttime digital number (DN) data from the DMSP-OLS stable dataset in 2012, respectively, and correlated with 12 socio-economic parameters at the provincial level in mainland China during the corresponding period. Background noise of DNB composite data is removed using either a masking method or an optimal threshold method. In general, the correlation of these socio-economic data with the total night light and light area of VIIRS-DNB composite data is better than with the DMSP-OLS stable data. The correlations between total night light of denoised DNB composite data and built-up area, gross regional product (GRP) and power consumption are higher than 0.9 and so are the correlations between the light area of denoised DNB composite data and city and town population, built-up area, GRP, power consumption and waste water discharge. However, the correlations of socio-economic data with the average night light and log average night light of VIIRS-DNB composite data are not as good as with the DMSP-OLS stable data. To quantitatively analyze the reasons for the correlation difference, a cubic regression method is developed to correct the saturation effect of the DMSP stable data, and we artificially convert the pixel value of the DNB composite into six bits to match the DMSP stable data format. The correlation results between the processed data and socio-economic data show that the effects of saturation and quantization are two of the reasons for the correlation difference. Additionally, on this basis, we estimate the total night light ratio between saturation-corrected DMSP stable data and finite quantization DNB composite data, and it is found that the ratio is ~11.28 ± 4.02 for China. Therefore, it appears that a different acquisition time is the other reason for the correlation difference.
