scholarly journals Preliminary Selection and Characterization of Pseudo-Invariant Calibration Sites in Northwest China

2020 ◽  
Vol 12 (16) ◽  
pp. 2517
Author(s):  
Xiuqing Hu ◽  
Ling Wang ◽  
Junwei Wang ◽  
Lingli He ◽  
Lin Chen ◽  
...  
Keyword(s):  
Optical Sensors ◽  
Temporal Stability ◽  
Selection Procedure ◽  
Northwest China ◽  
Radiometric Calibration ◽  
Practical Utilization ◽  
Vicarious Calibration ◽  
Spatial Uniformity ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Spectral Imager

Pseudo-invariant calibration sites (PICS) have been used for the radiometric calibration and stability monitoring of satellite optical sensors. Several stable PICS, such as those in the Sahara Desert in North Africa, were selected for the vicarious calibration of earth remote sensing satellites. However, the selection procedure of PICSs in the whole of Northwest China has not been fully explored before. This paper presents a novel technique for selecting PICS in Northwest China by combined using the coefficient of variation (CV) and the iteratively reweighted multivariate alteration detection (IR-MAD) technique. IR-MAD, which calculates the differences between two multispectral N-band images from the same scene acquired at different times, is used to identify no-change pixels (NCPs) of the scene through one image pair. The NCPs from IR-MAD using the long-term data of FY-3 visible infrared radiometer (VIRR) and aqua Moderate Resolution Imaging Spectroradiometer (MODIS) were aggregated into the contiguously stable sites. The traditional spatial uniformity and temporal stability from MODIS surface products were used to select the potential PICS. By combining the results of both methods, over thirty PICSs with a wider brightness range of the scene types were selected. To confirm and characterize these PICSs over Northwest China, Landsat operational land imager (OLI) high-spatial-resolution images were used to check the spatial uniformity of the selected site to determine the specific location and the size of these sites. Additionally, the surface spectral reflectance and bidirectional reflectance distribution function (BRDF) were obtained from the field campaign at Chaidamu Basin, 2018. To demonstrate the practical utilization and usability of these PICSs, they were employed in the multi-site top of atmosphere (TOA) reflectance simulation to validate the operational calibration performance of Aqua/MODIS and FY-3D/MERSI-II (Medium Resolution Spectral Imager II). The simulation results showed good consistency compared with the observations from both MODIS and MERSI-II, with a relative bias and root mean square error (RMSE) of <5% and <0.05%, respectively. These sites provide prospects for multi-site vicarious calibrations of solar reflective bands, which may help to evaluate or characterize instrumental nonlinear responses using a wider signal dynamic from the sites in different seasons.

scholarly journals Vicarious Radiometric Calibration of Ocean Color Bands for FY-3D/MERSI-II at Lake Qinghai, China

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 139
Author(s):  
Shengli Chen ◽  
Xiaobing Zheng ◽  
Xin Li ◽  
Wei Wei ◽  
Shenda Du ◽  
...  
Keyword(s):  
Infrared Imaging ◽  
Large Deviation ◽  
Ocean Color ◽  
Calibration Method ◽  
Surface Measurement ◽  
Radiometric Calibration ◽  
Lake Qinghai ◽  
Vicarious Calibration ◽  
Calibration Methods ◽  
Spectral Imager

To calibrate the low signal response of the ocean color (OC) bands and test the stability of the Fengyun-3D (FY-3D)/Medium Resolution Spectral Imager II (MERSI-II), an absolute radiometric calibration field test of FY-3D/MERSI-II at the Lake Qinghai Radiometric Calibration Site (RCS) was carried out in August 2018. The lake surface and atmospheric parameters were mainly measured by advanced observation instruments, and the MODerate spectral resolution atmospheric TRANsmittance algorithm and computer model (MODTRAN4.0) was used to simulate the multiple scattering radiance value at the altitude of the sensor. The results showed that the relative deviations between bands 9 and 12 are within 5.0%, while the relative deviations of bands 8, and 13 are 17.1%, and 12.0%, respectively. The precision of the calibration method was verified by calibrating the Aqua/Moderate-resolution Imaging Spectroradiometer (MODIS) and National Polar-orbiting Partnership (NPP)/Visible Infrared Imaging Radiometer (VIIRS), and the deviation of the calibration results was evaluated with the results of the Dunhuang RCS calibration and lunar calibration. The results showed that the relative deviations of NPP/VIIRS were within 7.0%, and the relative deviations of Aqua/MODIS were within 4.1% from 400 nm to 600 nm. The comparisons of three on-orbit calibration methods indicated that band 8 exhibited a large attenuation after launch and the calibration results had good consistency at the other bands except for band 13. The uncertainty value of the whole calibration system was approximately 6.3%, and the uncertainty brought by the field surface measurement reached 5.4%, which might be the main reason for the relatively large deviation of band 13. This study verifies the feasibility of the vicarious calibration method at the Lake Qinghai RCS and provides the basis and reference for the subsequent on-orbit calibration of FY-3D/MERSI-II.

scholarly journals Revisiting Pseudo Invariant Calibration Sites (PICS) Over Sand Deserts for Vicarious Calibration of Optical Imagers at 20 km and 100 km Scales

2019 ◽  
Vol 11 (10) ◽  
pp. 1166 ◽  
Author(s):  
Cédric Bacour ◽  
Xavier Briottet ◽  
François-Marie Bréon ◽  
Françoise Viallefont-Robinet ◽  
Marc Bouvet
Keyword(s):  
Temporal Stability ◽  
Remote Sensing Data ◽  
Global Scale ◽  
Trace Gas ◽  
Spatial Homogeneity ◽  
Vicarious Calibration ◽  
Spatial Uniformity ◽  
Surface Optical ◽  
Coarse Spatial Resolution ◽  
Semi Empirical

In-flight assessment of the radiometric performances of space-borne instruments can be achieved by means of vicarious calibration over Pseudo-Invariant Calibration Sites (PICS). PICS are chosen for the high temporal stability of their surface optical properties combined with a high spatial homogeneity. A first list of the main desert PIC sites was identified 20 years ago for the calibration of medium/coarse spatial resolution instruments in the solar spectral range (400–2500 nm). They are located in the Saharan desert and in the Arabian Peninsula. Six of them have since been endorsed by the CEOS/WGCV/IVOS as reference Calibration/Validation test sites. In this study, we have revisited the list of desert PIC sites at the global scale with the aim of (1) assessing if these twenty PICS are still “optimal”, in terms of temporal stability and spatial uniformity, and using up-to-date multi-spectral remote sensing data, and (2) identifying new calibration sites distributed over other areas of the world. We verified that the original sites remain very relevant, although alternate locations in their close vicinity have slightly better characteristics. We proposed four additional targets with similar characteristics, some of which may offer easier logistical access. In order to support radiative transfer simulations of satellite sensor measurements over the sites, we assessed the abilities of several semi-empirical models to reproduce the spectro-directional signatures of six IVOS sites and the four new candidate sites, and we derived climatologies of the main atmospheric properties (trace gas column load and aerosol optical depth).

scholarly journals ESTABLISHMENT OF VICARIOUS CALIBRATION/VALIDATION FACILITY FOR SPACE BORNE HIGH AND MID RESOLUTION OPTICAL SENSORS

2018 ◽  
Vol XLII-5 ◽  
pp. 913-919
Author(s):  
B. Santhi Sree ◽  
N. Raghavender ◽  
K. S. Raju ◽  
D. Chandrasekaran ◽  
B. Gopala Krishna ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Optical Sensors ◽  
Radiometric Calibration ◽  
Vicarious Calibration ◽  
The Earth ◽  
Medium Resolution ◽  
Infra Red ◽  
Materials Used ◽  
Edge Based ◽  
Periodic Evaluation

<p><strong>Abstract.</strong> Vicarious calibration refers to methods that make use of “invariant” natural targets of the Earth for the post-launch calibration of sensors. This process of calibration is useful for initial phase orbit operation of sensor and thereafter for validation during its operational span. This method of periodic evaluation of radiometric and geometric performance of the space-borne optical sensors and validation of derived radiance/reflectance is to ensure availability of consistent and accurate data products to the user community. This paper describes one such Cal/Val facility’s design, engineering aspects and realization at National Remote Sensing Centre (NRSC), Shadnagar. The target materials used for filling the Cal/Val site are studied for its reflectance. These targets have reflectance ranging from 9% to 53%, in the VNIR (Visible and Near Infra-Red) region. This paper also describes instruments used for calibration and homogeneity studies of targets for its invariance since operationalisation (January 2016). The last section of this paper is about reflectance based absolute radiometric calibration of medium resolution Indian Remote Sensing (IRS) sensor (Resourcesat and Cartosat series) using RT model and edge based LSF/MTF estimation of high resolution sensor carried out using the Cal/Val facility.</p>

scholarly journals ASSESSMENT OF CLOUD COVER CHARACTERISTICS OVER CALIBRATION TEST SITES USING MODIS CLOUD MASK PRODUCTS

2019 ◽  
Vol XLII-3/W7 ◽  
pp. 83-86
Author(s):  
H. Yamamoto ◽  
S. Tsuchida
Keyword(s):  
Optical Sensors ◽  
Cloud Cover ◽  
Accurate Method ◽  
Adjacent Area ◽  
Calibration Data ◽  
Radiometric Calibration ◽  
Remotely Sensed Data ◽  
Vicarious Calibration ◽  
Calibration Test ◽  
Cloud Mask

<p><strong>Abstract.</strong> Spaceborne remotely sensed data can provide the spatial, spectral, and temporal coverage for earth monitoring. Radiometric calibration is indispensable for the accurate higher level products derived from satellite optical sensors, and the long-term radiometric calibration has a crucial role. Especially, vicarious calibration is currently the most accurate method to conduct the radiometric calibration of satellite optical sensors. Various organization and projects have been conducting the vicarious calibration experiments for satellite optical sensors. Railroad valley playa is the most popular calibration site, and we have been also acquiring the vicarious calibration data for Terra ASTER there from the past. Recently, RadCalNet (Radiometric Calibration Network) is open to the public, which is an initiative of the CEOS WGCV. Railroad valley is also one of the RadCalNet sites, and our calibration site is located at the adjacent area. Understanding the cloud cover characteristics over calibration test sites is very important for vicarious calibration and automated facilities measurement. This research evaluates the clear sky ratio for Railroad valley playa using Terra an Aqua MODIS cloud mask product (MOD35_L2 and MYD35_L2) since 2000.</p>

scholarly journals New Approach for Temporal Stability Evaluation of Pseudo-Invariant Calibration Sites (PICS)

2019 ◽  
Vol 11 (12) ◽  
pp. 1502 ◽  
Author(s):  
Fatima Tuz Zafrin Tuli ◽  
Cibele Teixeira Pinto ◽  
Amit Angal ◽  
Xiaoxiong Xiong ◽  
Dennis Helder
Keyword(s):  
Temporal Stability ◽  
Kendall Test ◽  
Sensor Calibration ◽  
Landsat 8 ◽  
Radiometric Calibration ◽  
Calibration Source ◽  
Blue Band ◽  
New Approach ◽  
Monotonic Trend ◽  
Moderate Resolution Imaging Spectroradiometer

Pseudo-Invariant Calibration Sites (PICS) are one of the most popular methods for in-flight vicarious radiometric calibration of Earth remote sensing satellites. The fundamental question of PICS temporal stability has not been adequately addressed. However, the main purpose of this work is to evaluate the temporal stability of a few PICS using a new approach. The analysis was performed over six PICS (Libya 1, Libya 4, Niger 1, Niger 2, Egypt 1 and Sudan 1). The concept of a “Virtual Constellation” was developed to provide greater temporal coverage and also to overcome the dependence limitation of any specific characteristic derived from one particular sensor. TOA reflectance data from four sensors consistently demonstrating “stable” calibration to within 5%—the Landsat 7 ETM+ (Enhanced Thematic Mapper Plus), Landsat 8 OLI (Operational Land Imager), Terra MODIS (Moderate Resolution Imaging Spectroradiometer) and Sentinel-2A MSI (Multispectral Instrument)–were merged into a seamless dataset. Instead of using the traditional method of trend analysis (Student’s T test), a nonparametric Seasonal Mann-Kendall test was used for determining the PICS stability. The analysis results indicate that Libya 4 and Egypt 1 do not exhibit any monotonic trend in six reflective solar bands common to all of the studied sensors, indicating temporal stability. A decreasing monotonic trend was statistically detected in all bands, except SWIR 2, for Sudan 1 and the Green and Red bands for Niger 1. An increasing trend was detected in the Blue band for Niger 2 and the NIR band for Libya 1. These results do not suggest abandoning PICS as a viable calibration source. Rather, they indicate that PICS temporal stability cannot be assumed and should be regularly monitored as part of the sensor calibration process.

scholarly journals Vicarious Calibration of FengYun-3D MERSI-II at Railroad Valley Playa Site: A Case for Sensors with Large View Angles

2021 ◽  
Vol 13 (7) ◽  
pp. 1347
Author(s):  
Yepei Chen ◽  
Kaimin Sun ◽  
Wenzhuo Li ◽  
Xiuqing Hu ◽  
Pengfei Li ◽  
...  
Keyword(s):  
Field Measurements ◽  
Calibration Method ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Radiometric Calibration ◽  
Vicarious Calibration ◽  
In Situ Data ◽  
Benchmark Datasets ◽  
Moderate Resolution Imaging Spectroradiometer

Vicarious calibration, as one on-orbit calibration method, is a supplement to onboard calibration of sensors. The application of vicarious calibration, however, is greatly limited due to the time- and effort-consuming field measurements of atmosphere and surface. Fortunately, the Radiometric Calibration Network (RadCalNet) provides automated in situ data at multiple sites, thus increasing the opportunities to achieve ongoing ground-reference calibration of in-orbit instruments. The MEdium Resolution Spectrum Imager-II (MERSI-II) onboard FengYun-3D (FY) has the temporal, spectral, spatial, and radiometric capacity for image capture at a level on par with other sensors used worldwide, such as the Moderate Resolution Imaging Spectroradiometer (MODIS). Its on-orbit radiometric performance, however, is assessed in a limited manner. In this study, the reflectance-based vicarious calibration method was employed to calibrate the MERSI-II sensor using ground measurements from RadCalNet at the Railroad Valley Playa site. The calibration of the MERSI-II sensor with large view angles presents difficulties due to the uncertainties introduced by surface bidirectional reflectance distribution function (BRDF) effects. Thus, we performed BRDF correction to harmonize the sensor and ground measurements to consistent observation geometries, before the in-situ measurements were taken as inputs for the 6SV radiative transfer model to predict at-sensor radiance. The calibration results were comprehensively validated with ground data and MODIS benchmark datasets. The results show that accounting for BRDF correction could improve the accuracy of vicarious calibration and ensure inter-consistency between different sensors. An analysis of the vicarious calibration of FY-3D MERSI-II yielded uncertainties of <5% for solar reflective bands, which meets the radiometric accuracy requirements typical for land-monitoring space missions. The proposed approach is also applicable to the calibration of other large footprint sensors.

scholarly journals Radiometric Calibration for a Multispectral Sensor Onboard RISESAT Microsatellite Based on Lunar Observations

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2429
Author(s):  
Masataka Imai ◽  
Junichi Kurihara ◽  
Toru Kouyama ◽  
Toshinori Kuwahara ◽  
Shinya Fujita ◽  
...  
Keyword(s):  
Optical Sensors ◽  
Temperature Correction ◽  
Visible Range ◽  
Reference Source ◽  
Radiometric Calibration ◽  
The Moon ◽  
Infrared Band ◽  
Special Equipment ◽  
Vicarious Calibration ◽  
The Earth

Radiometric calibration utilizing the Moon as a reference source is termed as lunar calibration. It is a useful method for evaluating the performance of optical sensors onboard satellites orbiting the Earth. Lunar calibration provides sufficient radiometric calibration opportunities without requiring any special equipment, and is suitable for nano/microsatellites. This study applies lunar calibration to a multispectral sensor, Ocean Observation Camera (OOC), on board a microsatellite named Rapid International Scientific Experiment Satellite. Simulating the brightness of the Moon based on the RObotic Lunar Observatory and SELENE/Spectrum Profiler models, sensitivity degradation was proven to be negligible in any of the four spectral bands of the OOC with the sensor temperature correction. A bluing trend in the OOC’s sensor sensitivity was revealed, indicating a shorter observation wavelength shows larger irradiance. Comparing the top-of-atmosphere reflectance of Railroad Valley Playa with the Radiometric Calibration Network dataset revealed that the derived calibration parameter from the lunar calibration was valid for correcting the bluing trend in the visible range. Although the lunar and vicarious calibration parameters for the infrared band were unexpectedly inconsistent, lunar calibration could potentially contribute toward estimating the contaminated background radiance in the Earth observation images.

scholarly journals TEMPORAL STABILITY OF TUZ GÖLÜ AND ATACAMA DESERT REFERENCE SURFACES FOR ABSOLUTE CALIBRATION OF ORBITAL SENSORS

2015 ◽  
Vol 33 (2) ◽  
Author(s):  
Cibele Teixeira Pinto ◽  
Flávio Jorge Ponzoni ◽  
Ruy Morgado Castro
Keyword(s):  
Optical Sensors ◽  
Temporal Stability ◽  
Atacama Desert ◽  
Temporal Analysis ◽  
Earth Observation ◽  
Sensor Calibration ◽  
Absolute Calibration ◽  
Radiometric Calibration ◽  
Definition Of ◽  
Better Than

ABSTRACT. The vicarious absolute calibration of electro-optical sensors dedicated to the Earth observation includes the definition of a reference surface from which radiometric measurements taken from the ground are compared to the effective radiance measured by the sensor in orbit. In order to facilitate the surface radiometric characterization process and consequently the sensor radiometric calibration, it is desirable that the surface presents, besides additional characteristics, temporal reflectance stability. This study aimed to evaluate the temporal stability of two potential reference surfaces for radiometric calibration of orbital electro-optical sensors located at: Tuz Gölü Salar in Turkey and Atacama Desert in Chile. Therefore, a temporal analysis of the radiometric properties of these two surfaces using cloud free images of TM/Landsat 5 sensor, acquired from 2003 to 2011, was performed. It was concluded, based on statistical criteria, that both reference surfaces do not presented temporal stability. Nevertheless, both surfaces may still be used for sensor calibration purposes if they were submitted to further spectral characterization with higher frequency and/or if the surfaces were considered stable “enough” within a certain limit of variation in reflectance. Taking that into account, according to the results of this work, it can be stated that Tuz G¨ol¨u surface reflectance has temporal stability within a range of 3-14% and the Atacama Desert better than 6%.Keywords: Earth observation sensors, radiometric calibration, reflectance, TM/Landsat 5.RESUMO. A primeira etapa para a realização da calibração absoluta de sensores de observação da Terra é a definição de uma superfície de referência. Um dos métodos mais comuns de calibração após o lançamento do sensor utiliza medições radiométricas de áreas localizadas na superfície terrestre. Para facilitar o processode caracterização da superfície e consequentemente o processo de calibração radiométrica, é desejável que a superfície apresente, entre outras características, estabilidade temporal. Assim, este trabalho teve como objetivo avaliar a estabilidade temporal de duas superfícies de referência potenciais para a calibração radiométrica de sistemas sensores eletro-ópticos: o salar de Tuz Gölü na Turquia e o deserto de Atacama no Chile. Para tanto, foi realizada uma análise temporal do comportamento espectral das duas superfícies por meio de imagens do sensor TMabordo do Landsat 5 livres de nuvens adquiridas nos anos de 2003 a 2011.De acordo com os resultados obtidos foi possível concluir, segundo os critérios estatísticos, que as duas superfícies de referência não apresentam estabilidade temporal. Apesar disso, as duas superfícies ainda podem ser utilizadas para calibração de sensores. Nesse caso, deve-se caracterizar espectralmente as duas áreas com maior frequência e/ou considerar a superfície como sendo “suficientemente” estável se a variação na reflectância ao longo do tempo for menor do que um determinado valor. Se esta consideração for feita pode-se afirmar, segundo o resultado desse trabalho, que Tuz Gölü tem estabilidade temporal entre 3 a 14% e o deserto de Atacama melhor do que 6%.Palavras-chave: sensores de observação da Terra, calibração radiométrica, reflectância, TM/Landsat 5.

scholarly journals Practical example for use of the supervised vicarious calibration (SVC) method on multisource hyperspectral imagery data – ValCalHyp airborne hyperspectral campaign under the EUFAR framework

2014 ◽  
Vol XL-7 ◽  
pp. 51-53
Author(s):  
A. Brook ◽  
E. Ben Dor
Keyword(s):  
Atmospheric Correction ◽  
Ground Truth ◽  
Critical Issue ◽  
Radiometric Calibration ◽  
Vicarious Calibration ◽  
Flight Direction ◽  
Novel Approach ◽  
Novel Method ◽  
General Goal ◽  
Cross Calibration

A novel approach for radiometric calibration and atmospheric correction of airborne hyperspectral (HRS) data, termed supervised vicarious calibration (SVC) was proposed by Brook and Ben-Dor in 2010. The present study was aimed at validating this SVC approach by simultaneously using several different airborne HSR sensors that acquired HSR data over several selected sites at the same time. The general goal of this study was to apply a cross-calibration approach to examine the capability and stability of the SVC method and to examine its validity. This paper reports the result of the multi sensors campaign took place over Salon de Provenance, France on behalf of the ValCalHyp project took place in 2011. The SVC method enabled the rectification of the radiometric drift of each sensor and improves their performance significantly. The flight direction of the SVC targets was found to be a critical issue for such correction and recommendations have been set for future utilization of this novel method. The results of the SVC method were examined by comparing ground-truth spectra of several selected validation targets with the image spectra as well as by comparing the classified water quality images generated from all sensors over selected water bodies.

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