What is CMR?
Modern Earth Science applications strive to provide end users with nearly immediate access and interactivity across massive stores of Earth Science data. That data is discovered, navigated, and often interrogated through science metadata. The Common Metadata Repository (CMR) is a high-performance, high-quality, continuously evolving metadata system that catalogs all of the metadata records describing NASA’s earth facing satellite data as well as data from select other US and international agencies. The CMR maintains hundreds of millions of metadata records; striving to make them available in under 1 second. Clients can access this freely available metadata by leveraging REST protocols and APIs to perform keyword, spatial, temporal and faceted search. The simple to use APIs allow clients to perform powerful searches in order to find exactly the data they are looking for.
The metadata inside of the CMR falls into predominately two categories: granules and collections. Granule metadata describes an individual data file and contains spatial and temporal extents of the data as well as the quality and lineage of the data. Collection metadata describes an entire set of granules or data files and contains information such as the combined spatial and temporal extents, instruments used, citation information and other related topics. Both types of data can be queried from the CMR.
Collection level metadata can be queried in many different formats. The CMR serves to translate source metadata into the format that is desired by the client, regardless of the native format of the metadata. To date, the CMR can return search results as DIF9, DIF10, ECHO10, ISO19115 and a UMMC JSON format. Most formats are xml based, except for UMMC JSON.
The CMR incorporates both human and machine metadata assessment features that work to ensure the highest quality metadata possible.
The CMR itself is meant to be used in conjunction with a client. That client may be a simple script which makes REST based API calls to the CMR, or it could be a rich UI such as the Earthdata Search Client or Worldview. See Getting Started with the CMR for more information on developing a CMR client.