In-orbit image performance simulation for GOCI from integrated ray tracing computation

Oh, Eunsong; Kim, Sug Whan; Jeong, Yong-Jin; Jeong, S.; Ryu, Dongok; Cho, Seongick; Ryu, Ja‐Hyoung; Ahn, Yu-Hwan

doi:10.1117/12.897989

Cited by 3 publications

(5 citation statements)

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“…Extremely high SPM values occurred at the lower portion of the 12th slot. This is inferred to be related to the effect of instrumental correction problem such as the previously reported stray light issues induced by inner slot response (Oh et al 2011(Oh et al , 2013Kim et al 2015), which will be discussed in later section. Thus, we termed this type of speckle a 'slot-related speckle.…”

Section: Slot-related Specklementioning

confidence: 74%

“…GOCI also has essential instrumental problems related to the slot. In addition to the sharp disconnections between neighbouring slots, there is another issue related to the response phase in the inner slot termed the stray light effect (Oh et al 2011(Oh et al , 2013Kim et al 2015). These characteristic effects become increasingly intensified at the bottom of each individual slot.…”

Section: Discussionmentioning

confidence: 99%

“…Unlike these sensors, GOCI as a sensor of a geostationary satellite adopts a 'step and stare' mode that observes each channel in a slot sequentially and then moves to a neighboring slot continuously until the last slot (Figure 1(a)) (Kang et al 2006;Faure, Coste, and Kang 2008;Kang et al 2010). The stray light effect, as one of the mechanical problems of GOCI, may contaminate original signals from the sea surface by inflating the signals at the lower part of the slot (Oh et al 2011(Oh et al , 2013Kim et al 2015). There are large differences in observation times between slots.…”

Section: Slot-related Specklesmentioning

confidence: 99%

“…Similar to previous ocean colour satellite images, numerous speckles are shown in GOCI images. One of the significant errors originates from the stray light effect of the GOCI sensor, which should be considered for a proper estimation of optical properties to enhance the data quality for further scientific analysis (Oh et al 2011(Oh et al , 2013Kim et al 2015). The SPM is one of the ocean colour variables with higher possibility of speckle than any other parameters as inferred from general formula of the estimation of SPM, unlike chlorophyll-a concentration and CDOM.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Spatial and temporal characteristics and removal methodology of suspended particulate matter speckles from Geostationary Ocean Color Imager data

Lee

Park

Moon

et al. 2018

International Journal of Remote Sensing

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Reviewing six years of Geostationary Ocean Color Imager (GOCI) suspended particulate matter (SPM) concentration images from 2011 to 2016 revealed unexpected and some enormously high or low values. These speckles are randomly scattered throughout the entire study area or congregated at a certain part, which has strongly restricted the scientific applications of GOCI data thus far. They can be classified into four types: isolated, near-cloud, patchtype, and slot-related speckles, based on spatial distribution and potential causes. These types are investigated. The speckles are induced by a moving-cloud during a complete observation of 8 bands for each slot of GOCI, partly by an incomplete cloud masking procedure near cloud edges, by relatively low reflectance of pixels corresponding to a cloud shadow, by imperfect atmospheric corrections related to water vapor after cloud passage, or by sensor-related troubles related to the effects of stray light. Spatial and temporal variabilities of the identified speckles are investigated and used to develop a methodology for their removal. The SPM concentration values of the error-free pixels, passing through the post-processing of the speckle removal procedure, are compared to those previously with speckles. As a result, the enormously large values of SPM, occupying 6.06% of the pixel numbers, are all eliminated. Typical seasonality of SPM, unrevealed using the speckled images, is clearly presented through the removal procedure. This study addresses the importance of preprocessing for speckle error in SPM concentrations from GOCI data and implies more reliable SPM data without speckles can be used in scientific application research.

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Section: Slot-related Specklementioning

confidence: 74%

Section: Discussionmentioning

confidence: 99%

Section: Slot-related Specklesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Spatial and temporal characteristics and removal methodology of suspended particulate matter speckles from Geostationary Ocean Color Imager data

Lee

Park

Moon

et al. 2018

International Journal of Remote Sensing

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“…2 shows how the ISRD deteriorates the continuity in the marginal parts of the slots in the L1B product, which is demonstrated by the band difference and band ratio images between Bands 6 and 7. One of the factors that cause the ISRD is currently believed to be the stray light generated from the misalignment of sensor elements, such as filters, the support beam, and the thermal heater, the intensity of which is strengthened by bright targets in distant areas possibly located outside the slot [10], [11]. In this paper, the radiometric surge caused by the stray light is referred to as the stray-light-driven radiometric inflation (SLRI).…”

mentioning

confidence: 99%

Correction of Stray-Light-Driven Interslot Radiometric Discrepancy (ISRD) Present in Radiometric Products of Geostationary Ocean Color Imager (GOCI)

Kim

Ahn

Park

2015

IEEE Trans. Geosci. Remote Sensing

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The radiometric calibration of satellite data is critical in many environmental studies and applications that are based on remote sensing data. The Geostationary Ocean Color Imager (GOCI) has suffered from what is called an interslot radiometric discrepancy (ISRD), which creates clear inconsistency between the adjacent slots in GOCI Level 1B (L1B) radiometric products, the largest source of which is currently believed to be the stray light generated in the sensor instrument. Difficulties in removing the stray-light-driven anomalies are that the intensity and the spatial extent vary with time and location, depending on the reflectance of nearby bright targets, such as cloud and land. This paper proposes an image-based correction method that removes the stray-light-driven radiometric inflation without involving an independent reference so that the method can be used for GOCI operational data processing. First, the radiometric inflation pattern is characterized by independent sources, such as Moderate Resolution Imaging Spectrometer (MODIS) data, and the inflation pattern is modeled by the minimum noise fraction transform of the input data. The modeled inflation patterns in individual slots are then adjusted across the slots in such a way that the overall ISRD in all slot boundaries is minimized. The analysis shows that the stray-light-driven radiometric anomalies can be up to 20% of the normal signals in Bands 6 (680 nm) and 8 (865 nm) of the uncorrected L1B images, and the proposed correction method reduces it to less than 2% in most of the cases, recovering the spatial continuity of natural variability across the slots.Index Terms-Geostationary Ocean Color Imager (GOCI), interslot radiometric discrepancy (ISRD), minimum noise fraction (MNF), stray light, top-of-atmosphere (TOA) radiance.

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Novel ray tracing method for stray light suppression from ocean remote sensing measurements

Oh¹,

Hong²,

Kim³

et al. 2016

Opt. Express

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We developed a new integrated ray tracing (IRT) technique to analyze the stray light effect in remotely sensed images. Images acquired with the Geostationary Ocean Color Imager show a radiance level discrepancy at the slot boundary, which is suspected to be a stray light effect. To determine its cause, we developed and adjusted a novel in-orbit stray light analysis method, which consists of three simulated phases (source, target, and instrument). Each phase simulation was performed in a way that used ray information generated from the Sun and reaching the instrument detector plane efficiently. This simulation scheme enabled the construction of the real environment from the remote sensing data, with a focus on realistic phenomena. In the results, even in a cloud-free environment, a background stray light pattern was identified at the bottom of each slot. Variations in the stray light effect and its pattern according to bright target movement were simulated, with a maximum stray light ratio of 8.5841% in band 2 images. To verify the proposed method and simulation results, we compared the results with the real acquired remotely sensed image. In addition, after correcting for abnormal phenomena in specific cases, we confirmed that the stray light ratio decreased from 2.38% to 1.02% in a band 6 case, and from 1.09% to 0.35% in a band 8 case. IRT-based stray light analysis enabled clear determination of the stray light path and candidates in in-orbit circumstances, and the correction process aided recovery of the radiometric discrepancy.

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In-orbit image performance simulation for GOCI from integrated ray tracing computation

Cited by 3 publications

References 0 publications

Spatial and temporal characteristics and removal methodology of suspended particulate matter speckles from Geostationary Ocean Color Imager data

Spatial and temporal characteristics and removal methodology of suspended particulate matter speckles from Geostationary Ocean Color Imager data

Correction of Stray-Light-Driven Interslot Radiometric Discrepancy (ISRD) Present in Radiometric Products of Geostationary Ocean Color Imager (GOCI)

Novel ray tracing method for stray light suppression from ocean remote sensing measurements

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