The need for accessing historical Earth observation (EO) data series has strongly increased in the last ten years, mainly for long term science and environmental monitoring applications. This trend has increased even more in particular for the growing interest on global change monitoring which is driving users to request time-series of data spanning 20 years and more, and due also to the need to support the United Nations Framework Convention on Climate Change (UNFCCC).

Content of EO data archives has extended from a few years to decades and therefore their value as a scientific time-series is continuously increasing. Hence there is a strong need to preserve the EO space data without time constraints and to keep them accessible and exploitable. The preservation of EO space data can be also considered as a responsibility of the Space Agencies or data owners as they constitute a humankind asset.

The large amount of new Earth observation missions upcoming in the next years will lead to a major increase of EO space data volumes. This fact, together with the increased demands from the user community, marks a challenge for Earth observation satellite operators, Space Agencies and EO space data providers regarding coherent data preservation and optimum availability and accessibility of the different data products. Traditionally in Europe (including Canada), there has been poor cooperation in this field with no common approach for long term preservation and access to EO space data even if cooperation and sharing are key aspects to be pursued for the benefit of the user community.

A cooperative and harmonised collective approach on Long Term Data Preservation (LTDP) in Europe (i.e. a European EO LTDP Framework) is needed to coordinate and optimise European efforts in the LTDP field and to ultimately result in the preservation of the complete European EO space data set for the benefit of all European countries and users and with a reduction of overall costs.

Main goals of the European EO Long Term Data Preservation Framework are to:

• Preserve the European, and Canadian, EO space data sets for an unlimited time-span.
• Ensure and facilitate the accessibility and usability of the preserved data sets respecting the individual entities applicable data policies.
• Through the adoption of a cooperative and harmonised collective approach among the data owners (LTDP Framework) based on the application of European LTDP Common Guidelines and sustained through cooperative (multi-source) long term funding schemes.
• Ensure, to the maximum extent, the coherency with the preservation of other non-space based environmental data and international policies.

A common approach in the field of Long Term Data Preservation should aim at the progressive application of the European LTDP Common Guidelines but also at cooperation of the archive owners in several areas for a progressive development and implementation of technology, methodology, standardisation, operational solutions and data exploitation methodologies as key aspects for the set-up of the framework.

In 2006, the European Space Agency (ESA) initiated a coordination action to share among all the European (and Canadian) stakeholders a common approach to the long term preservation of Earth Observation space data. During 2007, the Agency started consultations with its Member States presenting an EO Long Term Data Preservation strategy targeting the preservation of all European (including Canada) EO space data for an unlimited time-span ensuring and facilitating their accessibility and usability through the implementation of a cooperative and harmonised collective approach among the EO space data owners.

The Long Term Data Preservation Working Group with representatives from ASI, CNES, CSA, DLR and ESA was formed at the end of 2007 within the Ground Segment Coordination Body (GSCB) with the goal to define and promote, with the involvement of all the European EO space data and archive owners, the LTDP Common Guidelines and also to increase awareness on LTDP. The LTDP guidelines constitute a basic reference for the long term preservation of EO space data. Their application by European EO space data owners and archive holders is fundamental in order to preserve the European EO space data set and to create an European LTDP Framework. The application of the identified guidelines is not a requirement or a must for European EO space data owners and archive holders but is strongly recommended also following a step-wise approach starting with a partial adherence.