In this post we briefly summarize how to search and download images acquired by ESA’s Earth observing satellite Sentinel-2a, part of the Sentinel constellation of the Copernicus programme (see previous introduction here, and the official Copernicus page). Sentinel-2 is a mission consisting of two identical polar orbiting satellites carrying one instrument each, the MSI – Multispectral instrument, that acquires high resolution multispectral imagery in 13 bands (see details here). The mission thus belongs to the same class of satellites as Landsat and SPOT. The first of the Sentinel 2 satellites was launched on 23 June 2015, images becoming available for download about half a year later. When complete, after the launch of the second satellite, the Sentinel 2 mission will result nearly complete coverage of the Earth with a minimum revisit time of 5 days at the equator.

As with all other satellites of the Sentinel family, images are freely downloadable at no cost. We here briefly review two different ways of getting the data: one the official ESA channel, the Sentinels Hub; and the other is through repository at the Amazon Web Services.

Downloading through the Sentinels Hub

We start by visiting at the Sentinels Data Hub web site. A login is necessary to access the data, so if you do not have an account you will have to create one first. Once this is done, it is simple to start searching, just click in the search button, or the advanced search button on the top left:

Choosing area, sensor, time period and maximum cloud cover in the Sentinels Data Hub.
Choosing area, sensor, time period and maximum cloud cover in the Sentinels Data Hub.

After we perform the search, the results are shown in this way:

Search results
Search results

Then, by clicking in the “eye” icon, we are shown the details of each scene:

Scene details
Scene details

If this scene satisfies our needs, we might download it by just pressing the “arrow” button, at the bottom right. Beware that scenes are packages of about 6 GB in size. Depending on the quality and speed of your connection, your download might take a lot of time and even become interrupted and might need to be resumed or restarted.

In the case shown here, our file is named:
“S2A_OPER_PRD_MSIL1C_PDMC_20160206T202952_R122_V20160206T100203_20160206T100203.SAFE”.

Contents look like this:

Sentinel 2 file contents.
Sentinel 2 file contents.

The xml file with the large name is a basic link that can be used to open this package in SNAP. Note the other xml file in the folder, designed for linking this piece of data to the INSPIRE initiative, an ambitious initiative for achieving interoperatibility of datasets across Europe.

Downloading through Amazon Web Services

I recently learned from a Twitter user (thanks @_VincentS_ for the info!) that Amazon Web Services were archiving Sentinel 2 data and offering them to the public. The procedure is somewhat simpler. We start by navigating to the AWS Sentinel 2 portal:

Amazon Web Services Sentinel 2 portal
Amazon Web Services Sentinel 2 portal

the, by clicking in “Browse through data”, in the menu to the left, we can choose region, time span and admissible cloud cover:

Data interface
Data interface

by clicking in the desired cell, we are shown the details of the image:

Available scenes and details.
Available scenes and details.
Available scenes and details.
Available scenes and details.

and lastly, by clicking on the “Link to tile” link, we are directed to a page where we can download the images:

Image download links.
Image download links.

Note that the tiles are identified as 100 km2 tile on a so called MGRS system, so it is handy to know how the tiles are named in the region of the world your images are. You can find a vector file with all tiles here. The images one downloads from Amazon Web Services are directly usable as rasters in a GIS, as usual.

In the next post we will review how to open and preprocess the files downloaded from the Sentinels Data Hub. Happy downloading!

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