On-orbit performance of MODIS solar diffuser stability monitor

Xiong, Xiaoxiong; Angal, Amit; Choi, Taeyoung; Sun, J.; Johnson, Eric H.

doi:10.1117/1.jrs.8.083514

Cited by 32 publications

(11 citation statements)

References 22 publications

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“…After more than 12 years of on-orbit operation, reflectance degradation of Aqua MODIS SD varies from 0.6% at 0.94 µm to 19.0% at 0.41 µm [22]. Due to more frequent solar exposure, the Terra MODIS SD has experienced a much larger degradation, varying from 2.3% at 0.94 µm to 48.0% at 0.41 µm.…”

Section: Degradation Of Viirs Sd As Monitored By the Sdsmmentioning

confidence: 99%

Spectral Dependent Degradation of the Solar Diffuser on Suomi-NPP VIIRS Due to Surface Roughness-Induced Rayleigh Scattering

2016

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Abstract:The Visible Infrared Imaging Radiometer Suite (VIIRS) onboard Suomi National Polar Orbiting Partnership (SNPP) uses a solar diffuser (SD) as its radiometric calibrator for the reflective solar band calibration. The SD is made of Spectralon™ (one type of fluoropolymer) and was chosen because of its controlled reflectance in the Visible/Near-Infrared/Shortwave-Infrared region and its near-Lambertian reflectance property. On-orbit changes in VIIRS SD reflectance as monitored by the Solar Diffuser Stability Monitor showed faster degradation of SD reflectance for 0.4 to 0.6 µm channels than the longer wavelength channels. Analysis of VIIRS SD reflectance data show that the spectral dependent degradation of SD reflectance in short wavelength can be explained with a SD Surface Roughness (length scale << wavelength) based Rayleigh Scattering (SRRS) model due to exposure to solar UV radiation and energetic particles. The characteristic length parameter of the SD surface roughness is derived from the long term reflectance data of the VIIRS SD and it changes at approximately the tens of nanometers level over the operational period of VIIRS. This estimated roughness length scale is consistent with the experimental result from radiation exposure of a fluoropolymer sample and validates the applicability of the Rayleigh scattering-based model. The model is also applicable to explaining the spectral dependent degradation of the SDs on other satellites. This novel approach allows us to better understand the physical processes of the SD degradation, and is complementary to previous mathematics based models.

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Section: Degradation Of Viirs Sd As Monitored By the Sdsmmentioning

confidence: 99%

Spectral Dependent Degradation of the Solar Diffuser on Suomi-NPP VIIRS Due to Surface Roughness-Induced Rayleigh Scattering

2016

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“…The direction of the SD observed by the SDRDM and AGRI was relatively fixed. Under the same incident angle, the relative change in reflectivity from the SD to the SDRDM and AGRI could be better than 0.5% [2][3][4].…”

Section: Analysis and Discussionmentioning

confidence: 99%

“…First, the SDRDM and the AGRI were used to observe the same radiance source with different energy levels; the numerical relationship between them under the same radiance input was established. Then, the outgoing radiance in the SDRDM observation direction was corrected to obtain the radiance in the AGRI observation direction [2][3][4][5][6] according to the bidirectional reflectance factor (BRF) [7][8][9] of the SD. Based on the measured relative relationship between the AGRI and the SDRDM with the full aperture response, according to the observations, the radiance source, the ratio between the calculated full aperture response value of the AGRI and the actual partial aperture measurement response was obtained; then, the PAF of the AGRI was determined.…”

Section: Introductionmentioning

confidence: 99%

Research on a Partial Aperture Factor Measurement Method for the AGRI Onboard Calibration Assembly

Chen

et al. 2022

Sensors

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A partial aperture onboard calibration method can solve the onboard calibration problems of some large aperture remote sensors, which is of great significance for the development trend of increasingly large apertures in optical remote sensors. In this paper, the solar diffuser reflectance degradation monitor (SDRDM) in the onboard calibration assembly (CA) of the FengYun-4 (FY-4) advanced geostationary radiance imager (AGRI) was used as the reference radiometer. It was designed for measuring the partial aperture factor (PAF) for the AGRI onboard calibration. First, the linear response count variation relationship between the two was established under the same radiance source input. Then, according to the known bidirectional reflection distribution function (BRDF) of the solar diffuser (SD) in the CA, the relative reflectance ratio coefficient between the AGRI observation direction and the SDRDM observation direction was calculated. On this basis, the response count value of the AGRI and the SDRDM was used to realize the high-precision measurement of the PAF of the AGRI B1~B3 bands by simulating the AGRI onboard calibration measurement under the illumination of a solar simulator in the laboratory. According to the determination process of the relevant parameters of the PAF, the measurement uncertainty of the PAF was analyzed; this uncertainty was greater than 2.04% and provided an important reference for the evaluation of the onboard absolute radiometric calibration uncertainty after launch.

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“…The SD reflectance has decreased over the mission due to the periodic exposure to solar radiation during the scheduled SD/SDSM calibration events, as well as some indirect exposure to solar stray light through the nadir port. The degradation of the SD has been reliably tracked by the SDSM system for the last two decades 15 , 16 Figure 2(a). shows the time evolution of the SD degradation, which is the SD reflectance relative to its value at launch, at different wavelengths as measured by three of the nine SDSM detectors.…”

Section: On-orbit Performancementioning

confidence: 98%

“…The degradation of the SD has been reliably tracked by the SDSM system for the last two decades. 15,16 Figure 2(a) shows the time evolution of the SD degradation, which is the SD reflectance relative to its value at launch, at different wavelengths as measured by three of the nine SDSM detectors. There is more degradation for shorter wavelengths, with the shortest wavelength detector 1 (410 nm) showing 22% drop in reflectance as of March, 2023.…”

Section: Rsb Radiometric Performancesmentioning

confidence: 99%

Aqua MODIS: 20 years of on-orbit calibration and performance

Xiong

Angal

Chang

et al. 2023

J. Appl. Rem. Sens.

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Since its launch in May, 2002, Aqua MODIS has successfully operated for more than 20 years and has continuously generated a wide range of data products that have enabled and supported the remote sensing community and users worldwide for their studies of the Earth's system by monitoring changes in its key environmental parameters. Although Aqua MODIS, designed with a lifetime requirement of 6 years, is currently operated in its extended mission phase, it continues to make high quality global observations of the Earth's surface via its 36 spectral bands that cover wavelengths from visible to long-wave infrared. To date, all instrument on-board calibrators (OBC) remain capable of performing their design functions, providing various calibration data sets to help monitor on-orbit changes in sensor responses and performance characteristics. In addition to the OBC, regularly scheduled lunar observations and select Earth-view targets are used extensively to support sensor on-orbit calibration, especially for the calibration of the visible channels (or bands). We provide an overview of Aqua MODIS on-orbit calibration activities and methodologies for both reflective solar bands and thermal emissive bands, illustrate its on-orbit performance over the past 20 years using examples derived from OBC measurements, lunar observations, and Earth-view response trends, and describe various calibration improvements made over its entire mission. We focus on key issues identified since launch, such as solar diffuser degradation, electronic crosstalk, and on-orbit changes in sensor response versus scan-angle, along with approaches and strategies developed to mitigate their impact on sensor calibration quality. Also discussed in this paper are some of the key calibration enhancements incorporated recently in the Collection 6.1 and the upcoming Collection 7 Level-1B algorithms.

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On-orbit performance of MODIS solar diffuser stability monitor

Cited by 32 publications

References 22 publications

Spectral Dependent Degradation of the Solar Diffuser on Suomi-NPP VIIRS Due to Surface Roughness-Induced Rayleigh Scattering

Spectral Dependent Degradation of the Solar Diffuser on Suomi-NPP VIIRS Due to Surface Roughness-Induced Rayleigh Scattering

Research on a Partial Aperture Factor Measurement Method for the AGRI Onboard Calibration Assembly

Aqua MODIS: 20 years of on-orbit calibration and performance

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