Searching for Sentinel data is often a complicated process due to the different missions available, the different Copernicus Sentinel Hubs that host data and geographic restrictions, but also the different performances of the Hubs in terms of download speed and latency (at both the inter and intra level). Thus, at BEYOND Center of EO Research and Satellite Remote Sensing we developed two difference services, the Copernicus Sentinel Broker Hub and the Umbrella Sentinel Access Point, that both bring the various Sentinel Access Points all together in a one stop shop (the so called federated access) offering uniform access to Sentinel 1, Sentinel 2, Sentinel 3, and Sentinel 5p metadata. This is done via connecting at the back end to a number of the available Copernicus Sentinel Data Sources and serving the data search results via a front end catalogue and an Application Programming Interface (API).
On the plus side the applications we have developed will be a solution for RO that will be the cheapest, has the best availability in terms of data access, matches the timeliness performance of the best performing Hub, and also secures downloading from the Hub with the highest, at the time, download capacity if the same product exists in more than one Hub.
On the cons side, our applications will have to use as many accounts, as the number of Hubs it connects to. If we connect to 10 different Hubs then we will need 10 different accounts to be created once following the ESA policy on data download and user tracking.
Umbrella Sentinel Access Point
- Independent of the API’s architecture; It can connect to any API under certain prerequisites.
- Provision of the download link from the most appropriate hub for any requested product at a particular instance.
- Scoring process for identifying the most appropriate Sentinel Access Point takes places every 15 minutes
- API Offer, no GUI.
- Ten connected hubs
Copernicus Sentinel Broker Hub
The Service stores not only information about the metadata, but also information about the hubs. Metadata information is the same with the one on the source hubs, e.g. polarization for Sentinel-1 or cloud coverage for Sentinel-2.
The greatest advantage of our service is that it provides users the download link from the most appropriate hub for the requested product. This is achieved by a scoring process which runs every eight hours and sums up the availability and performance of the hubs.
Summing up, our service is based on three pillars:
- The synchronization of the latest products' metadata, as well as the newly evicted products from the enlisted DataHub Services in order to update products' availability.
- The performance metrics gathered during every synchronization round, that are later on used to extract a performance KPI for every Data Hub harvested.
- The OpenSearch API, that provides a list of available access points for any requested product sorted using our performance metrics.
What to use
If a user is more comfortable to use the standard UI of DHuS and its functionality, then users will use the Copernicus Sentinel Broker Hub. If a user requires more flexibility and better performance then they should exploit the Umbrella Sentinel Access Point. From our side, we will keep maintaining and supporting both applications. As far as ESA keeps having DHuS as its main data access software and most of the Mirror Sites use this as well, the Copernicus Sentinel Broker Hub is useful. When more customized solutions are required, then the Umbrella Sentinel Access Point is the way to go.
RELATED SERVICES & PLATFORMS
The Sentinel data federated gateway is accessed through the Application Programming Interface (API) directly from the Hellenic Mirror Site :https://sentinels.space.noa.gr/dhus/#/home
Application Development of Copernicus Sentinel Broker Hub: Zavras Angelos, azabras[at]noa.gr
Application Development of Umbrella Sentinel Access Point: Athanasios Drivas, tdrivas[at]noa.gr
General Contact Person: Vassileios Sitokonstantinou, vsito[at]noa.gr