THEIA : A new French Data Centre dedicated to Land Surfaces

(French Version)

The THEIA Land Data Centre is a French inter-agency initiative designed to promote the use of satellite data, primarily for environmental research on land surfaces but also for public policy monitoring and for management of environmental resources. Its objective is to foster the use of remote sensing data to measure the impact of human pressure and climate on ecosystems and local areas, to observe, quantify and model water and carbon cycles, to follow the evolution of societies and of their activities, including agricultural practices, and to understand the dynamics of biodiversity.


Within the Land Data Centre, CNES set up a production centre named MUSCATE. This centre aims are providing users with ready-to-use products derived from time series of images acquired over large areas. Sentinel-2 will of course be the spearhead of the production centre, but before the launch of the Sentinel-2, MUSCATE will already begin to produce data from the SPOT4 (Take 5) experiment. At the same time, the processing centre also prepares the production of all Landsat data acquired over mainland France from 2009 to 2011.


MUSCATE production centre already exists in the form of a prototype developed by CNES with strong support from Cap Gemini. This prototype is already able to handle LANDSAT, SPOT, FORMOSAT-2, Sentinel-2 and Venμs data, using processors developed by CNES for geometric processing [1], and developed by CESBIO for cloud detection [2] and for atmospheric correction [3]. Simultaneously, the development of an operational production facility is being specified.

Products provided by the MUSCATE Centre are:

Simulations of SPOT4(Take5) products from Formosat-2 data
  • Level 1C (orthorectified reflectance at the top of the atmosphere)
  • Level 2A (ortho-rectified surface reflectance after atmospheric correction, along with a mask of clouds and their shadows, as well as a mask of water and snow).
  • Level 3A (bi-monthly or monthly composite products of surface reflectances, obtained as the weighted average surface reflectance of non-cloudy pixels obtained during the period). Up to now, Level 3A chain is only available for Venμs satellite.

The data produced by MUSCATE will be freely distributed to research laboratories on the one hand, and to the French public institutions on the other, they will be if possible distributed freely to a wider community. The Land Data Center is also building a distribution server to make all these data available.


Further reading about these products :

[1]: Baillarin, S., P. Gigord, et O. Hagolle. 2008. « Automatic Registration of Optical Images, a Stake for Future Missions: Application to Ortho-Rectification, Time Series and Mosaic Products ». In Geoscience and Remote Sensing Symposium, 2008, 2:II‑1112‑II‑1115. doi:10.1109/IGARSS.2008.4779194.

[2]: Hagolle, Olivier, Mireille Huc, David Villa Pascual, et Gérard Dedieu. 2010. « A multi-temporal method for cloud detection, applied to FORMOSAT-2, VENµS, LANDSAT and SENTINEL-2 images ». Remote Sensing of Environment 114 (8) (août 16): 1747‑1755. doi:10.1016/j.rse.2010.03.002.

[3]: Hagolle, O, G Dedieu, B Mougenot, V Debaecker, B Duchemin, et A Meygret. 2008. « Correction of aerosol effects on multi-temporal images acquired with constant viewing angles: Application to Formosat-2 images ». REMOTE SENSING OF ENVIRONMENT 112 (4) (avril 15): 1689‑1701. doi:10.1016/j.rse.2007.08.016.


Choix des sites pour SPOT4 (Take 5)

(English Version)

Choisir les sites pour l'expérience SPOT4(Take5) ne fut pas de tout repos. Le délai de choix était très court, nous sentions que la demande serait forte, nous ne voulions pas être accusés de favoritisme et de copinage (et nous n'avons même pas accepté de cadeaux (1)).


Nous avons procédé de deux manières différentes pour les sites destinés aux laboratoires et organismes français d'une part, et pour les sites destinés aux agences spatiales d'autre part.


Emprise approximative des sites observés par SPOT4(Take5) en France et en Belgique

Pour les sites français, nous avons lancé un appel à proposition de sites, avec un délai de réponse très court (de l'ordre du mois), et c'est le comité TOSCA qui a procédé à la sélection. Cet appel d'offres a connu un grand succès, puisque 20 propositions ont été reçues, avec la participation de 81 laboratoires et organismes.


Les sites de SPOT4 (Take 5) en Afrique

Pour les sites internationaux, nous nous sommes rapprochés des agences spatiales ou de recherche impliquées dans le programme Sentinel-2, à savoir l'ESA, le JRC, la NASA ou le CCRS. Ici, l'accusation de copinage pourrait être retenue (mais nous n'avons pas reçu de cadeaux), nous n'avions pas le temps d'émettre un appel à proposition et de constituer un jury pour le choix. Cependant, la participation de ces agences implique de leur part une contribution financière pour l'achat des images de niveau 1A au fournisseur privé : Astrium Geo (anciennement Spot Image).


Bien évidemment, nous souhaitons que les images acquises pour l'expérience SPOT4(Take5) soient le plus largement diffusées. Les images seront donc disponibles pour toute personne en faisant la demande, pour une utilisation non commerciale dans le cadre de la préparation à Sentinel-2. Les demandes d'accès seront à adresser au Pôle Thématique Surfaces Continentales (PTSC)

(1) Par contre, maintenant que les sites sont choisis...

Selection of SPOT4 (Take 5) sites

(French Version)

Choosing the sites observed for SPOT4 (Take5) was not easy. The schedule was very tight, we felt that demand would be strong and we did not want to be blamed for favoritism or cronyism (and we did not even accept gifts (1)).


We processed differently for sites for French laboratories and organizations on the one hand, and sites for other space agencies on the other hand.


SPOT4 (Take 5) sites in France and Belgium

For the French sites, we launched a call for proposals for sites, with a very short notice (one month), and CNES TOSCA committee made the selection. This call was a great success : 20 proposals were received, with the participation of 81 laboratories and agencies.


For international sites, we contacted space and research agencies involved in Sentinel-2 project, namely ESA, JRC, NASA or the CSRC. Here, the charge of favoritism could be retained (but we have not received gifts),as we did not have time to issue a call for proposals and set up a jury for selection. However, the participation of these agencies implies their financial contribution to purchase Level 1A images from Astrium Geo (formerly Spot Image).


SPOT4(Take5) sites in Africa.

Of course, we hope that the acquired images for SPOT4 (Take5) experiment will be widely distributed. The images will be made available to anyone upon request, for non-commercial use in the framework of Sentinel-2 preparation. Please send your requests to the Land Thematic Data Center (or Pôle Thématique Surfaces Continentales (PTSC).)


(1) But now that the sites are chosen...

Choix des sites observés pour SPOT4 (Take 5)
Choix des sites observés pour SPOT4 (Take 5)