The goal of the CO3D (Constellation Optique 3D) mission is the full-automatic production of a worldwide accurate DEM. CO3D is also a constellation of a new generation of low-cost optical satellites. The DEM accuracy is expected to be one meter in relative height and four meters in absolute height with a one-meter grid space. Each of the four satellites of the constellation will provide images with 0.50 m resolution in red, green, blue and near-infrared bands. The satellites resource will be shared by, on one hand, the French institutions (government, scientists concerned by global Earth monitoring) who will have dedicated access and preferred price conditions, and on the other hand commercial customers interested in 2D and 3D products. The launch of the constellation is expected mid-2025.Starting from an overview of the system characteristics and its main innovations, this paper describes the 2D and 3D products that should be available for the end-users and focus on how they should be qualified.

Earth Observation (EO) remote sensing missions are producing an increasing volume of data due to higher spatial and spectral resolutions, and higher frequency of acquisitions. To prepare new EO missions, CNES, the French space agency, develop in partnership with CS a demonstrator that aims at implementing and validating image processing chains using Big Data and Cloud technologies in an environment similar to an operational image processing center. The image processing pipeline chosen for the study is a 3D image processing chain that will be used for a future earth observation mission. The demonstrator is currently being tested at a large scale on various Cloud infrastructures with numerous stereo and tri-stereo images.

The performance stability of CCD detectors and video electronics during life time is an important issue for most of space missions. Several items are concerned, such as CCD dark signal increase, induced by space radiation environment (dose effects, proton hits, etc... ). Ground tests are performed to predict on-board behaviour and end-of-life performance. But generaly this approach cannot achieve a rigorous representation of mission conditions. Experience feedback from in-flight measurements is therefore very useful in order to infer what really occurs and to allow comparison between actual findings and ground tests.

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 17th, 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.

MODIS is the key instrument for the NASA's EOS Terra and Aqua missions, launched in late 1999 and early 2002, respectively. MODIS has 20 reflective solar bands (RSB) and 16 thermal emissive bands (TEB). MODIS RSB are calibrated on-orbit using an on-board solar diffuser and regularly scheduled lunar observations. For each instrument, the scheduled lunar observations are made through its space view (SV) port at nearly identical lunar phase angles via spacecraft roll maneuvers. Occasionally, unscheduled lunar observations at different phase angles are also collected by both Terra and Aqua MODIS. The PLEIADES system is composed of two satellites, PLEIADES-1A launched at the end of 2011 and PLEIADES-1B a year later. The PLEIADES has 5 reflective solar bands or channels (blue, green, red, nearinfrared, and panchromatic) that are calibrated on-orbit using observations of Pseudo Invariant Calibration Sites (PICS). Since launch, more than 1000 lunar images covering the phase angle range of ±115° have been acquired by PLEIADES- 1B for its on-orbit calibration and sensitivity study of lunar calibration methods. This paper provides an overview of MODIS and PLEIADES lunar observations and an assessment of their calibration difference based on lunar observations made over a range of phase angles. Also discussed in this paper are strategies and future effort that could potentially benefit other earth observing sensors and improve the calibration accuracy and consistency of existing lunar model(s).

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 properties are 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 degrees. 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.

PLEIADES earth observing system consists of two satellites designed to provide optical 70cm resolution images to civilian and defense users. The first Pleiades satellite 1A was launched on December 2011 while the second satellite Pleiades 1B was placed on orbit, one year after, on December 2012. The calibration operations and the assessment of the image of the two satellites have been performed by CNES Image Quality team during the called commissioning phase which took place after each launch and lasted each time less than 6 months. The geometric commissioning activities consist in assessing and improving the geometric quality of the images in order to meet very demanding requirements. This paper deals with the means used and methods applied, mainly the innovative ones, in order to manage these activities. It describes both their accuracy and their operational interest. Finally it gives the main results for geometric image quality performances of the PHR system.

Pleiades est le système d'observation de la Terre civil le mieux résolu développé en Europe. Ce programme d'imagerie est conduit par le Centre National d'Etude Spatial français (CNES). Le premier satellite a été lancé le 17/12/2011 et le second le 02/12/2012. Chaque satellite est conçu pour fournir des images optiques aux utilisateurs civils et défense. Les images sont acquises simultanément en Panchromatique (PA) et multi-spectral (XS), ce qui permet en condition d'acquisition nadir d'obtenir des scènes de 20 km de large, en couleurs naturelles ou fausses couleurs, avec une résolution de 70 cm sur les produits PA+XS fusionnés. La couverture est quasi-mondiale avec une période de revisite de 24h avec les 2 satellites.L'évaluation de la Qualité Image et les opérations d'étalonnage ont été réalisées par l'équipe Qualité Image du CNES pendant les recettes en vol de 6 mois qui ont suivi le lancement de chacun des satellites. Ces activités couvrent plusieurs thèmes comme l'étalonnage absolu, le calcul des coefficients d'égalisation, les opérations de refocalisation, l'estimation de la FTM, l'étalonnage du modèle géométrique, l'estimation de la précision de localisation, la registration multi-spectrale, les stabilités statiques et dynamiques, les précisions planimétriques et altimétriques. Ces opérations nécessitent des réglages spécifiques de la charge utile ainsi que des guidages particuliers de la plateforme du satellite. Les nouvelles capacités offertes par l'agilité des satellites Pleiades nous ont autorisées à imaginer de nouvelles méthodes d'étalonnage et de mesures des performances.Après quelques rappels sur les caractéristiques principales des satellites, la présentation décrit les opérations d'étalonnage qui ont été menées pendant les recettes en vol et fournit les principaux résultats de Qualité Image.

This paper deals with the problem of retrieving attitude perturbances in the framework of the PLEIADES-HR optical satellites. Thus, two complementary methods are compared. The first one uses the high agility capacity of satellites to acquire stars in an inertial steering mode. The second method exploits the fact that multispectral CCD arrays are shifted in the telescope focal plane in the velocity direction: for a same ground point, the resulting images are not affected by the same attitude perturbances. The resulting misregistrations can be exploited to deduce information about the attitude platform. Both methods have been applied to PLEIADES-HR satellites, during commissioning period.

In-flight calibration of space sensors once in orbit is a decisive step to be able to fulfil the mission objectives. This article presents the methods of the in-flight absolute calibration processed during the commissioning phase. Four In-flight calibration methods are used: absolute calibration, cross-calibration with reference sensors such as PARASOL or MERIS, multi-temporal monitoring and inter-bands calibration. These algorithms are based on acquisitions over natural targets such as African deserts, Antarctic sites, La Crau (Automatic calibration station) and Oceans (Calibration over molecular scattering) or also new extra-terrestrial sites such as the Moon and selected stars. After an overview of the instrument and a description of the calibration sites, it is pointed out how each method is able to address one or several aspects of the calibration. We focus on how these methods complete each other in their operational use, and how they help building a coherent set of information that addresses all aspects of in-orbit calibration. Finally, we present the perspectives that the high level of agility of PLEIADES offers for the improvement of its calibration and a better characterization of the calibration sites.

Since SPOT1, the French national space centre (CNES) has worked on improving the geometry of Earth observation spacecrafts. The accuracy of sensor calibration is one of the main key points for any Earth observation application such as orthorectification, DEM generation or surface change detection. For the last twenty years CNES has developed two families of methods: absolute methods and relative methods. These methods are used to characterize a pushbroom acquisition along the detector line and the time line. By this way, the viewing directions are measured and the residual of the spacecraft’s attitude angles (not restituted by the Attitude and Orbit Control System) is estimated. This information can complete the geometric model of all the scenes acquired by the instrument and is used in all geometric applications. This paper presents new attitude assessment methods taking advantage of the capabilities of Pléiades-HR in terms of agility and focal plane arrangement – panchromatic band and multispectral (MS) bands.

Abstract. PLEIADES is the highest resolution civilian earth observing system ever developed in Europe. This imagery program is conducted by the French National Space Agency, CNES. It has been operating since 2012 a first satellite PLEIADES-HR launched on 2011 December 17th, a second one should be launched by the end of the year. Each satellite is designed to provide optical 70 cm resolution colored images to civilian and defense users. Thanks to the extreme agility of the satellite, new calibration methods have been tested, based on the observation of celestial bodies, and stars in particular. It has then been made possible to perform MTF measurement, re-focusing, geometrical bias and focal plane assessment, absolute calibration, ghost images localization, micro-vibrations measurement, etc… Starting from an overview of the star acquisition process, this paper will discuss the methods and present the results obtained during the first four months of the commissioning phase.

The Pleiades system, ORFEO system optical component (Optical and Radar Federated Earth Observation) consists of a constellation of two satellites for very High Resolution panchromatic and multispectral optical observation of the Earth. Its mission is to cover all European civilian needs (mapping, tracking floods and fires) and defence in the category of metric resolution: 0.7m Nadir. The first Pleiades satellite was launched at the end of last year. One of the key objectives of the Pleiades HR (PHR) project is to achieve a location accuracy that will allow the use of images in GIS (Geographical Information System) without geometrical model improvement by refining on ground control points. The image location without refined model was specified with the precision of the most commonly used tool ie the civil GPS. So the location accuracy has been specified at less than 12m for 90% of the images on a nominal satellite configuration. Very special care has been taken all along the PHR project realization to achieve this very good location accuracy. The final touch is given during the in-orbit commissioning phase which lasts until June 2012. The geometric quality implies to tune the parameters involved in the geolocation model (geometric calibration): besides attitude and orbit restitution tuning (not considered here), it consists in estimating the biases between the instrument orientation and the AOCS reference frame, and also the sight line of each detector in the focal plane. This is called static geometrical model. The analysis of dynamic perturbations outside of the model are the second most important image quality objective of in-flight commissioning, not described in this paper. Finally “image quality assessment” consists in evaluating the image quality obtained in the final products. For geolocation model, it is quantified by the absolute geolocation and the pointing accuracies, and it is a main contributor in length alteration and planimetric and altimetric accuracies. In this paper we will present both the different practices we have adopted (their advantages, limitations and complementarities) and the means we are using for the operational assessment of the location quality of PHR images. We will focus on the innovative methods and mention the improvements in progress. To conclude, we will present the very first accuracy results assessed after PHR1A launch on L1 and Sensor products.

The new French high resolution earth observing satellite PLEIADES-HR will be launched in 2011. A specific design and new technologies have been embarked to provide great agility. These capabilities offer new methods to perform the image quality activities during the commissioning period. Some of them depend on dedicated guidance of the satellite platform and specific targets on the Earth or beyond. For instance, one concerns the so-called AMETHIST method to compute the normalization coefficients of the radiometric model. Another one is based on a controlled slow-motion to get a reference image line whose deviation along the image will give information on radiometric noise or attitude perturbations. Another uses the stars to measure the line-of-sight dynamic stability or the instrument refocusing needs. These originals methods and some more are briefly presented in this paper after an introduction of PLEIADES-HR capacities.

Since SPOT1, the French national space center (CNES) has worked on improving the geometry of Earth observation spacecrafts. The accuracy of sensor calibration is one of the main key points for any Earth observation application such as orthorectification, DEM generation or surface change detection [7]. Two families of methods have been developed by CNES for twenty years: absolute methods and relative methods. These methods are used to characterize a pushbroom acquisition along the detector line and the time line. By this way, the viewing directions are measured and the residual of the spacecraft's attitude angles (not restituted by the AOCS) are estimated. This information can complete the geometric model of all the scenes acquired by the instrument and is used in all geometric applications. We will first consider the absolute methods and then the relative methods.

Pleiades-HR is the highest resolution civilian earth observing system ever developed in Europe. This optical imaging project is conducted by the French National Space Agency, CNES. It will operate two satellites designed to provide optical images to civilian and military users. The first satellite will be ready for launch by April 2010, the second 18 months later. It will allow, in Nadir acquisition conditions, to deliver image products 20 km wide, false or natural coloured scenes with a 50 cm ground sampling distance. Imaging capabilities have been highly optimized in order to acquire, in the same pass, along-track mosaics, stereo pairs and triplets, and multi-targets. To fulfil the operational requirements and ensure quick access to information, ground processing has to automatically perform the radiometnc and geometric corrections. Since ground processing capabilities have been taken into account very early in the mission development, it has been possible to relax some costly on-board components requirements, in order to achieve a cost effective on-board/ground compromise. Starting from a Pleiades-HR system overview, this paper gives a quick description of the ground segment functional breakdown and focuses more precisely on the image processing and associated products. The geometric accuracy is evaluated and the excellent results obtained are presented. Finally the paper presents the ground segment architecture that will handle this "heavy" processing in the different operational Centres.