What is Metadata?
Without context data has no meaning. Take for example, the following table:
Without context the values in columns A, B, and C are ambiguous; the answer to whether or not the table’s content refers to the same thing (e.g., a satellite, an asteroid, etc.) is uncertain.
- Metadata, or simply, data that describes data, provides the context necessary for the table’s values to have meaning.
With basic metadata, the columns can be given context and are no longer ambiguous (Figure 2). The table can now be interpreted and recognized for what it is (e.g., orbital elements) and the data is therefore meaningful and useful.
One issue with metadata is that it is rarely consistent. Two tables that describe the same thing, for example, may use very different metadata (Fig. 3).
The need for a metadata schema, or a common way of describing and organizing metadata, is therefore needed when working with more than one dataset, sharing information with other people, or searching across different systems using tools like APIs. In this way metadata helps facilitate the sharing of lessons learned and access to information.
Different, existing metadata standards can be “crosswalked” (Fig. 4) and incorporated into a single metadata schema. One group may choose to implement a schema using Standard 1, while another may choose to use a Standard 2. The metadata crosswalk makes these standards translatable, while the schema itself makes it clear which standard is being used and in what context.
Figure 4: Simplified Orbital Elements Crosswalk
What is MetaSat?
MetaSat, as a common way of describing small satellite missions, aims to improve interoperability and access to mission outputs by removing ambiguity and providing the digital infrastructure necessary for crosswalking mission-related metadata and standards. In this way the schema is like a recipe card that can be filled out by people participating in missions and recording information about missions. The schema does not include small satellite mission data itself, but rather, data about mission data. In this way the schema remains a highly flexible tool regardless of its specific use case (e.g., maintaining a database, running a ground station network).
Consider how a recipe card could be used to describe a recipe on a website, in a cookbook, or in a script for a cooking show — in each case the same schema could be implemented. In one case certain metadata elements may not be required, and in another case it may be necessary to add new elements to the schema. For instance, it may be necessary to include elements about a recipe’s cultural origin (e.g. geographic region) or the type of oven required to prepare the dish, but in other cases these metadata elements may not be necessary.
Similarly, a schema to describe small satellite missions may need elements to record or link to standardized metadata about images taken by a specific instrument, but not all satellite missions would need to use those elements. Likewise, if the schema was implemented on a dashboard to monitor an on-going mission, fields related to a satellite’s orbit would be essential, but that information may be less essential if the schema is being used to build an archive of software used by missions funded through a specific program.
- For this reason, MetaSat is open and publically available so that it can be implemented for any purpose.