Pleiades Absolute Calibration : Inflight Calibration Sites and Methodology

Lachérade, Sophie; Fourest, Sébastien; Gamet, Philippe; Lebègue, Laurent

doi:10.5194/isprsarchives-xxxix-b1-549-2012

Cited by 8 publications

(5 citation statements)

References 6 publications

(4 reference statements)

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“…The absolute calibration of the 5 spectral bands is based on 5 different calibration sites: 2 types of pseudo-invariant calibration sites, African deserts and Antarctica (Dome sites) desert sites; oceanic sites used for calibration over Rayleigh scattering; Lacrau site where ROSAS, the CNES RObotic Station for Atmosphere and Surface located on La Crau test site is settled; and the Moon [2].…”

Section: Absolute Calibrationmentioning

confidence: 99%

POLO: a unique dataset to derive the phase angle dependence of the Moon irradiance

et al. 2014

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PLEIADES is a dual Earth observation system composed of two satellites, PLEIADES-1A and PLEIADES-1B, respectively launched at the end of 2011 and 2012. This imagery system, led by CNES, has four spectral bands, blue, green, red and near infrared, with a spatial resolution of 2.8 m and a panchromatic band with a resolution of 0.7 m in vertical viewing. Its swath is about 20 km.In the framework of the PLEIADES radiometric calibration, studies took place in order to determine the calibration precision that could be reached from the acquisitions realized on the Moon. Indeed, the precisions reached from observations of calibration sites on Earth (African deserts, Antarctica, clouds, instrumented sites) are about 2-3% for most of the spectral bands in the visible and the near infrared spectra. It is very difficult to further improve this precision down to 1% because each method has its own limitations, generally due to atmospheric disturbances. In this context, the Moon seems to be an ideal calibration site: there is no atmosphere and its surface properties -thus its optical propertiesare perfectly stable. Taking advantage of the high level of agility of PLEIADES, we performed an intensive observation campaign of the Moon in addition to the nominal acquisitions -when the Moon phase angle is about 40°. This intensive observation of the Moon, named POLO for Pleiades Orbital Lunar Observations, consists of a thousand acquisitions covering the phase angle range ±115 deg. The Moon was acquired as frequently as once every orbit, which represents acquisitions every 100 minutes. This paper provides an overview of these lunar experiments and an assessment of the variation of the irradiance of the Moon with phase angle. This paper also discusses a way to improve the phase angle dependence of existing lunar models.

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Section: Absolute Calibrationmentioning

confidence: 99%

POLO: a unique dataset to derive the phase angle dependence of the Moon irradiance

et al. 2014

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“…The inorbit geometric calibration of satellites is completed by selfcalibration. In the literature, in-orbit calibration is performed by high-resolution push broom satellite images and side sway scanning images with the same coverage area [14,[23][24][25]. However, the GF-7 footprint camera is an area-array sensor with a narrow field of view (FOV).…”

Section: Introductionmentioning

confidence: 99%

In‐orbit geometric calibration approach and positioning accuracy analysis for the Gaofen‐7 laser footprint camera

Xie

Ren

Huang

et al. 2021

IET Image Processing

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The Gaofen‐7 (GF‐7) satellite is China's first submeter high‐resolution optical stereo‐mapping satellite. The satellite is equipped with two area‐array laser footprint cameras to capture the laser spots emitted by laser altimeters. To accurately identify and locate the geographical positions of laser spots, a stepwise geometric calibration method with ground laboratory information for high‐resolution area‐array camera is proposed in this paper. It includes the internal and external calibration. First, the initial values of the camera's internal parameters are determined based on the laboratory calibration results. Then, based on a high‐precision reference ortho‐image and a digital elevation model, the ground control points (GCPs) for multi‐scene footprint images are obtained by image matching. Finally, the external and internal calibration methods for the laser footprint camera are implemented successively. The experimental results indicate that this method can restore geometric imaging relationships with high precision. After the internal and external calibration, the systematic residual error of the image point is eliminated, the remaining residual achieves 0.38 pixel, and the accuracy of direct positioning on the ground is better than 5.0 m, and the elevation accuracy is within 1.5 m.

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“…In a nominal calibration mode, the moon is observed once a month during the descending phase in order to follow the stability of the absolute calibration of the different spectral bands [7].…”

Section: B Absolute Calibrationmentioning

confidence: 99%

First in-flight results of Pleiades 1A innovative methods for optical calibration

Kubik

Lebègue

Fourest

et al. 2017

International Conference on Space Optics — ICSO 2012

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The PLEIADES program is a space Earth Observation system led by France, under the leadership of the French Space Agency (CNES). Since it was successfully launched on December 17 th , 2011, Pleiades 1A high resolution optical satellite has been thoroughly tested and validated during the commissioning phase led by CNES. The whole system has been designed to deliver submetric optical images to users whose needs were taken into account very early in the design process. This satellite opens a new era in Europe since its off-nadir viewing capability delivers a worldwide 2-days access, and its great agility will make possible to image numerous targets, strips and stereo coverage from the same orbit. Its imaging capability of more than 450 images of 20 km x 20 km per day can fulfill a broad spectrum of applications for both civilian and defence users.For an earth observing satellite with no on-board calibration source, the commissioning phase is a critical quest of wellcharacterized earth landscapes and ground patterns that have to be imaged by the camera in order to compute or fit the parameters of the viewing models. It may take a long time to get the required scenes with no cloud, whilst atmosphere corrections need simultaneous measurements that are not always possible.The paper focuses on new in-flight calibration methods that were prepared before the launch in the framework of the PLEIADES program : they take advantage of the satellite agility that can deeply relax the operational constraints and may improve calibration accuracy. Many performances of the camera were assessed thanks to a dedicated innovative method that was successfully validated during the commissioning period : Modulation Transfer Function (MTF), refocusing, absolute calibration, line of sight stability were estimated on stars and on the Moon. Detectors normalization and radiometric noise were computed on specific pictures on Earth with a dedicated guidance profile. Geometric viewing frame was determined with a particular image acquisition combining different views of the same target.All these new methods are expected to play a key role in the future when active optics will need sophisticated in-flight calibration strategy.

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Pleiades Absolute Calibration : Inflight Calibration Sites and Methodology

Cited by 8 publications

References 6 publications

POLO: a unique dataset to derive the phase angle dependence of the Moon irradiance

POLO: a unique dataset to derive the phase angle dependence of the Moon irradiance

In‐orbit geometric calibration approach and positioning accuracy analysis for the Gaofen‐7 laser footprint camera

First in-flight results of Pleiades 1A innovative methods for optical calibration

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