RadCalNet: A Radiometric Calibration Network for Earth Observing Imagers Operating in the Visible to Shortwave Infrared Spectral Range

Vicarious calibration approaches using in situ measurements saw first use in the early 1980s and have since improved to keep pace with the evolution of the radiometric requirements of the sensors that are being calibrated. The advantage of in situ measurements for vicarious calibration is that they can be carried out with traceable and quantifiable accuracy, making them ideal for interconsistency studies of on-orbit sensors. The recent development of automated sites to collect the in situ data has led to an increase in the available number of datasets for sensor calibration. The current work describes the Radiometric Calibration Network (RadCalNet) that is an effort to provide automated surface and atmosphere in situ data as part of a network including multiple sites for the purpose of optical imager radiometric calibration in the visible to shortwave infrared spectral range. The key goals of RadCalNet are to standardize protocols for collecting data, process to top-of-atmosphere reflectance, and provide uncertainty budgets for automated sites traceable to the international system of units. RadCalNet is the result of efforts by the RadCalNet Working Group under the umbrella of the Committee on Earth Observation Satellites (CEOS) Working Group on Calibration and Validation (WGCV) and the Infrared Visible Optical Sensors (IVOS). Four radiometric calibration instrumented sites located in the USA, France, China, and Namibia are presented here that were used as initial sites for prototyping and demonstrating RadCalNet. All four sites rely on collection of data for assessing the surface reflectance as well as atmospheric data over that site. The data are converted to top-of-atmosphere reflectance within RadCalNet and provided through a web portal to allow users to either radiometrically calibrate or verify the calibration of their sensors of interest. Top-of-atmosphere reflectance data with associated uncertainties are available at 10 nm intervals over the 400 nm to 1000 nm spectral range at 30 min intervals for a nadir-viewing geometry. An example is shown demonstrating how top-of-atmosphere data from RadCalNet can be used to determine the interconsistency between two sensors.

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Uncertainty analysis of sensor performance parameters in the shortwave infrared spectral range based on nightglow as the main lightsource

10.1117/12.2053321 ◽

2014 ◽

Cited By ~ 1

Author(s):

Thomas Svensson ◽

David Bergström

Keyword(s):

Uncertainty Analysis ◽

Spectral Range ◽

Performance Parameters ◽

Sensor Performance ◽

Infrared Spectral Range ◽

Infrared Spectral ◽

Shortwave Infrared

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

Remote Sensing ◽

10.3390/rs13071347 ◽

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.

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IEEE PROJECT 4001 – STANDARDS FOR CHARACTERIZATION AND CALIBRATION OF HYPERSPECTRAL IMAGING DEVICES

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-archives-xliv-m-3-2021-43-2021 ◽

2021 ◽

Vol XLIV-M-3-2021 ◽

pp. 43-47

Author(s):

B. A. Eckstein ◽

R. Arlen

Keyword(s):

Remote Sensing ◽

Hyperspectral Imaging ◽

Wavelength Range ◽

Data Structures ◽

Working Group ◽

Industrial Laboratory ◽

Characterization Methods ◽

Infrared Spectral Range ◽

Infrared Spectral ◽

Shortwave Infrared

Abstract. Hyperspectral imaging (HSI) systems have been invaluable tools for over two decades, but there are few authoritative standards that characterize these systems or define the data and metadata they produce. Manufacturers calibrate instruments and report specifications differently and, in some cases, the same term has different definitions among HSI programs.To address these inconsistencies, the Institute of Electrical and Electronics Engineers (IEEE) Geoscience and Remote Sensing Society (GRSS) sponsored Project 4001 (P4001), a Hyperspectral Working Group under the auspices of IEEE’s Standards Association. Since its inception in 2018, the IEEE P4001 Working Group has been working to specify testing and characterization methods for HSI device manufacturers, as well as recommend data structures and terminology for HSI products.P4001 focuses on the ultraviolet through the shortwave infrared spectral range (~250 to 2500 nm) and prioritizes camera technologies that are in widespread use. Many aspects of the standard will have wider applicability with respect to camera technology and wavelength range, and updates will expand the range of technologies and topics covered. Industrial, laboratory and geoscience use cases are informing the development of the standard. Utilization of the P4001 HSI standard will lead to HSI systems with consistent characterization and calibration criteria, as well as interoperable data products with a common lexicon for data and metadata.

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