Virtual European Solar &amp; Planetary Access (VESPA) 2024: Legacy
Authors: Erard Stéphane ,   VESPA team
Published: July 2024

During the last 2 EC-funded Europlanet programmes, VESPA has focused on adapting Virtual Observatory (VO) standards and procedures to Planetary Science data [1]. The objective was to build a contributory distribution system to provide 1) FAIR access to the many datasets from a single end points, 2) a simple solution for institutes to share their research results and therefore enforce the Open Science policy in the field. The infrastructure is now mature and available to the community.
Data description. EPNCore is a specific metadata vocabulary providing uniform description of datasets in the field. Associated to the TAP mechanism, it allows uniform cross-searches in connected data services [2]. In 2022, this EPN-TAP v2.0 protocol has been approved by the International Virtual Observatory Alliance, and is now the standard to publish Solar System data in the VO. Version 2.1 is in progress and will enlarge the scope of descriptive parameters as well as the support of coordinate systems. The VESPA team is deeply involved in the evolution of IVOA vocabularies and mapping them with neighbouring fields.
Data content. Nearly 250 data services using EPN-TAP are declared in the IVOA registry. The main VESPA portal dispatches queries to 73 reviewed services at the time of writing. Contributions from space agencies include ESA&#8217;s PSA, and 100+ datasets from the NASA PDS PPI node (under review). Contributions from the community have been solicited via an annual call and implementation workshop since 2016, where ~30 research teams were invited to acquire the knowledge to design and publish their data in the VO. Such data services are typically installed under DaCHS on Docker in the institutes, but installation on EOSC has been validated also. A dedicated validator is available in TOPCAT/taplint.
In addition to EPN-TAP data services, 69 multi-resolution maps of solar system bodies have been published in HiPS format. They provide detailed basemaps for display in Aladin and similar tools.
Data access and curation. The main VESPA portal is a discovery tool to search reviewed EPN-TAP services globally. It has been deeply redesigned in the past two years to make the user experience smoother, and a gallery view of thumbnails is being added. Other access modes are available: scripts, web services, Jupyter notebook, VO tools, etc, including two more specialised portals.
The main portal uses a local registry of reviewed services to ensure quality control, and is regularly updated. For instance some older data services and assessments studies have been dropped recently. All EPN-TAP services are now properly declared in the IVOA registry, which allows simple access via VO tools and python libraries (astropy, pyvo, etc).
A discovery portal is used internally to check the consistency of data content, relying on an ElasticSearch database of all metadata from reviewed services; in the mid-term, this may provide a better interface for cross-service searches than the main portal. A geospatial portal also uses this system to support 2D searches on planetary surfaces, both in data services and planetary HiPS. This makes extensive use of of MOC (MultiOrder Coverages) and HiPS standards from the IVOA, but also provides interoperability with OGC standards used in GIS (WMS, WCS, shapefiles). Planetary HiPS can be displayed in AladinLite Planetary Explorer, which queries USGS web services to retrieve named surface features.
Connectivity. Existing VO tools (TOPCAT, Aladin, CASSIS) can query EPN-TAP services and can receive data from the portals via SAMP. Data services providing calls to web services such as WMS/WCS or das2 can send data to dedicated tools (resp. QGIS and Autoplot). The environment uses web services from USGS (named surface features), IMCCE (body name resolver, ephemeris) or CNES (WMS-HiPS converter, CRS definitions). Planetary coordinate systems have been included in the WCSlib and astropy libraries. A workflow platform installed on EOSC is used to run computation on demand &#8211; results may be collected and distributed in EPN-TAP services.
Sustainability. A standard workflow has been designed for preservation, relying on a common GitLab repository (with authentication granted by G&#201;ANT/eduTEAMS). Services definition files are stored there to allow interaction between teams (through GitLab issues) and possible crisis management. Several services no longer maintained for various reasons have been reinstalled in new places or on EOSC servers; this is possible when they do not rely on a specific backend to provide the data.
Further uses. Although VESPA was initially designed to provide simple access to solar system data, the capacity to easily distribute derived data products from research institutes has become a major goal with the apparition of Open Science commitments, in particular for publicly funded programs.
Other applications of this infrastructure are however possible, including private data services. Those can be installed in the frame of a research project to help the analysis of a dataset. The whole VO infrastructure also contain all that is needed to setup ground segments of space instruments and prepare the data distribution phase, in particular for nanosat missions.
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The Europlanet-2024 Research Infrastructure project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreements No 871149.

[1]&#160;&#160; S. Erard, B. Cecconi, P. Le Sidaner, M. Demleitner, and M. Taylor, &#8220;EPN-TAP: the VO standard to share and access Solar System data&#8221; PV2023 conference, Dec. 2023, doi: 10.5281/ZENODO.10255586.
[2]&#160;&#160; S. Erard, B. Cecconi, P. Le Sidaner, M. Demleitner, and M. Taylor, &#8220;EPN-TAP: Publishing Solar System Data to the Virtual Observatory Version 2.0&#8221; IVOA Recommendation 22 August 2022, Aug. 2022.