VENUS-EXPRESS : a contribution to a long-term archive process
Evelyne Orsal(1), Marcel Camps(1), Pierre Bourrousse(1)
(1) CNES
18 av E. Belin, 31401 Toulouse Cedex 9, France
EMail: evelyne.orsal@cnes.fr
ABSTRACT

The Venus-Express mission is an ESA mission, decided in 2002. The probe was launched on November 9, 
2005 and was put into orbit around Venus on April 11, 2006.

ASPERA-4 (Analyzer of Space Plasmas and Energetic Atoms) is one of the 7 scientific experiments, aiming 
at the long-term observation of the venusian atmosphere.

IRF (Kiruna, Sweden) is the PI institute and IRAP (Toulouse, France) the Co-PI Institute of this experience. 
IRAP receives data from the instrument ASPERA-4, processes L1 (level 1) data and provides the L1 
products to Co-I Institutes.

For its planetary missions, ESA has defined a requirement to archive data under PDS (Planetary Data 
System) format. The PDS is a format defined by NASA for its archives of Planetology data. The task of 
converting the ASPERA-4 L1 data under PDS format and to archive them at the PSA (Planetary Science 
Archive) based at ESAC (Villafranca del Castillo, Spain) has been delegated to CNES (Toulouse, France).

The PDS is a standard distributed data format created by the Office of Space Science at NASA and used in 
the field of space science, which ensures long-term archiving of scientific data, describing all the necessary 
elements. The PDS is an active archive that makes available to the research community well documented 
data, reviewed by experts.

The PSA provides expert consultancy to all of the data producers throughout the archiving process. As soon 
as an instrument is selected, PSA begin to work with the instrument team to define a set of data products and 
data set structures that will be suitable for ingestion into the long-term archive.

The archive is organized by “data sets” that contain data and all the elements necessary to the understanding 
and interpretation of them (description of the mission, the satellite instruments and documentation of their 
calibration, delivered software, detailed description of the archive contents). Rules, methodology and full 
description of data sets are specified in the EAICD (Experiment to Archive Interface Control Document) 
which is the main applicable document for the archive preparation.

The overall processing system of L1 data and L1 PDS is operated under delayed time mode. The L1 data of a 
quarter are processed within a 3 months period after their acquisition. At the end of these 3 months (in fact 6 
months after the start of the acquisition of the quarter) they are available to be put under PDS format and 
transmitted to ESAC. Data sets will be provided to ESAC every 3 months duration of a "release", a dataset 
corresponds to 3 months of data

The first operational constraint lies in the broadcast from ESA within a 6 months period after the acquisition 
of measurements (in other words, at the end of the "Proprietary" period).

Another constraint originates from the chronological treatment of a "release".

All the exploitation constraints are well taken into account at CNES by:
- using CNES multi mission facilities (archiving, data production and delivery, network data exchange, help 
desk and web services, …) ;
- sharing the same software maintenance team with Cassini, Mars-Express, ... ;
- sharing the same data production team with many other missions ;
- relying on an IRAP experts common team for Mars-Express and Venus-Express ASPERA data.