Archiving sample science data in PDS4: Challenges and solutions

PDS4 for planetary missions

Planetary data acquired by flight and landed missions scientific instruments are currently archived in several planetary science archives, such as the ESA Planetary Science Archive, or the NASA PDS, following the Planetary Data System (PDS) standard. In PDS version 4 (PDS4), a product consists in zero to many data files and a PDS4 label (XML or LBLX) capturing the metadata attributes of the product. Those metadata attributes are critical to identify PDS4 products, associate products to specific missions, instruments, time of data acquisition, targets, and fully describe the data and document object(s) properties. The PDS4 standard allows to open data products easily, which can be archived in many possible data formats (ASCII, binary, FITS, CDF, …) and structures (tables, images, cubes, …), using a standard PDS4 data reader.

 

PDS4 dictionaries usage

While common metadata attributes are part of the PDS4 core information model, so-called PDS4 “discipline”, “mission” or “instrument” local data dictionaries extend the capabilities of the core information model and capture the specifics of the data products. In particular, discipline and instrument dictionaries usually cover a wide flavour of very specific attributes and classes dealing with e.g. imaging instrument settings (Imaging dictionary), spectral measurement techniques (Spectral and Spectral Library dictionaries), observing geometries (Geometry dictionary). Instruments onboard classical flight and landed missions easily make use of these dictionaries. Data acquired on collected samples with specific on-ground instrumentation in dedicated facilities are however very diverse and may not fit all within the scope of the existing discipline dictionaries.  

 

Archiving sample science data in PDS4 format

With the increase of planetary sample return missions, the need to better support the PDS4 archiving for returned sample data arise. In the framework of the Analogue Sample Library project, we are acquiring and archiving data and documentation on terrestrial analogue samples of planetary bodies collected on the field. The data products generated encompass sample description and classification, catalogues, field reports, chemical testing, strength testing, X-ray diffraction (XRD), X-ray Computed Tomography (XCT), and many others. These many data sets are usually recorded in very diverse formats (proprietary and non-proprietary). As a first step, we are currently migrating the data products into PDS4-compliant formats (CSV tables and binary cubes). Instruments, facilities, samples and investigations are being registered in PDS4 to fill the products metadata. New PDS4 dictionaries better suited for sample science products are being designed, in order to capture the sample material high-level properties and geological context. New attributes are being identified to capture metadata at product level related to the new types of measurements performed on the samples. We will present the status of project.