Envisat MERIS Online Dissemination Help Page

Introduction

Welcome to the ESA Envisat MERIS Online Dissemination Service allowing direct access to the latest reprocessed MERIS Data.

For troubleshooting or questions, please contact the ESA EO Help Desk.

Supported Browsers

The following Web Browsers are supported by this system: Internet Explorer, Firefox, Google Chrome, Safari. It is recommended to use the latest release.

Terms and Conditions for the Utilisation of ESA’s Earth Observation Data

The access and use of Envisat MERIS products are regulated by the ESA Data Policy and subject to the acceptance of the specific Terms & Conditions.

Users accessing MERIS products are intrinsically acknowledging and accepting the above.

Data Availability

The data available through this service is stemming from the 4th MERIS reprocessing. Both the MERIS Full Resolution (FR) and Reduced Resolution (RR) data has been generated with the same processor configuration (MEGS 9) and is covering the entire Envisat MERIS mission archive spanning from:

  • MERIS Reduced Resolution (RR): 29 April 2002 to 8 April 2012 (end of mission)
  • MERIS Full Resolution (FR): 17 May 2002 to 8 April 2012 (end of mission)

To be noted that during the Envisat mission operations, MERIS Reduced Resolution (RR) was systematically operated and data recorded on board for the duration of the sun-illuminated segment. Differently, the Full Resolution (FR) data was acquired only when required to satisfy specific user requests and/or for the background mission scenario. The data availability/coverage for the two resolutions is consequently not the same.

On the dissemination server, the MERIS data is organised in four separate collections for respectively MERIS Full Resolution (FR) and MERIS Reduced Resolution (RR) Level 1 and Level 2 data. Note that the collections are independent and it is not possible to search products from multiple collections at the same time.

Data Format

The 4th MERIS data reprocessing has been focused on the alignment of the MERIS and Sentinel-3/OLCI data processing chains to ensure a continuity of the products derived from these two instruments. The former MERIS Envisat data format (.N1) has been changed in favour of the Sentinel-3 SAFE format based on a folder of NetCDF files including an xml manifest file. Also the file naming convention has been changed.

For all the distributed MERIS Level 1 and Level 2 products, the EO Product Component is a ZIP archive enclosing the .SEN3 package in ‘Sentinel-3 like’ format.

The S3-like product contains several files (Measurement Data files and/or Annotation Data files in NetCDF-4 format for metadata, variables and flags) all stored in one directory.

Note that the .ZIP filename follows a different format with respect to the S3-like file naming convention.

In the .ZIP product file name, as shown in the online catalogue and downloaded by the user, is reported the absolute orbit, relative orbit/track and product generation time information (see values highlighted in blue in sample A and B below, e.g. MER_FRS_1P and MER_RR__1P).

The unzipped MERIS product contained in the .ZIP file follows the new S3-like format where instead the product duration, cycle and relative orbit/track information is reported (see values highlighted in blue in sample A and B below, e.g. ME_1_FRG and ME_1_RRG).

Samples of MERIS FR/RR .ZIP and S3-like files:

A) Full Resolution -> MER_FRS_1P / ME_1_FRG

ZIP file name:
EN1_MDSI_MER_FRS_1P_20041214T033837_20041214T035016_014587_0004_20180416T110133_0100.ZIP

SEN3 file name:
ENV_ME_1_FRG____20041214T033837_20041214T035016_________________0698_033_004______DSI_R_NT____.SEN3

B) Reduced Resolution -> MER_RR__1P / ME_1_RRG

ZIP file name:
EN1_MDSI_MER_RR__1P_20110401T170555_20110401T174931_047512_0084_20180818T061758_0100.ZIP

SEN3 file name:
ENV_ME_1_RRG____20110401T170555_20110401T174931_________________2616_101_084______DSI_R_NT____.SEN3

For further information on the MERIS products and related format, please refer to the MERIS Sentinel3-like L1 and L2 Product Format Specification.


Tools

The Sentinel Application Platform (SNAP) and the Sentinel-3 Toolbox can be used for handling the MERIS 4th reprocessing data in Sentinel-3 like format.


1. EO Sign In Registration

EO Sign In is based on a modern Identity and Access Management interface replacing the EO Single Sign On (EO SSO), to facilitate users’ access to ESA EO data and services technology in compliance with the EU General Data Protection Regulations.

You can openly search and browse for all data products from this Service, but log-in with your own EO Sign In account is required in order to download any files.

In order to create a personal account, new ESA users must follow the registration process by clicking on "Login" at the top-right corner of any page and then on “Register Now”, to create the new account.

1.1 Login

You can login into the system following these simple steps:


2. Search for Data

The Envisat MERIS Online Dissemination Service is based on HTTP access via the dedicated web portal. Note that users can freely search and browse the MERIS data collections without performing a login. The login will however be requested at the moment of the download of the data.

2.1 Search via the web portal

To start searching for data, navigate to the Service https://meris-ds.eo.esa.int/oads/access/, click on the "Collection" button and choose the data collection of interest.

The online dissemination service allows for search and download in the following different ways:

  • Search in collection by Catalogue
  • Search in collection by Treeview
  • Search in collection by Filename

2.1.1 Search by Treeview Navigation

This function allows navigating a dynamic structure via the Web Browser where data is organised in collections. The user can navigate among the available data types by Mission Phase, Year and Track/Relative Orbit.

2.1.2 Search by File Name

This function allows searching a product by its file name. You can use the whole name of the file of interest, or part of it (using "*" for any number or characters and "?" for exactly one character of any type) in order to search for multiple products

Before starting to use this functionality, it is recommended to get familiar with the MERIS file naming conventions.
See section for Data Format.

  • To display the results on a list of products, tick the "Show search result as product list"
  • To display the results in a short URL list, tick "Show search result as URL list"
Note that in case of more than 500 results the view defaults to a "URL list".

2.1.3 Catalogue Search

This function allows geographical search by bounding box and metadata filtering.

2.1.3.1 Search Form

  • Click the "draw bbox" checkbox and draw a rectangular area to define the bounding box of interest on the world map
  • When a bounding box is drawn on the world map, the "footprint" information gets filled by the coordinates of the displayed rectangular area. This information can be manually adjusted by changing latitude and longitude values. The area will be adjusted as well on the map
  • In order to refine your search, if needed, you can specify additional metadata parameters:
    • "Format": "HTML search response" is intended for detailed browsing, "Bulk download lists" and "Plain text metadata index" are intended for bulk download
    • "Items per page": only refers to the "HTML search response"
    • "Geographical coverage": allows indicating the coordinates of the area of interest as min and max latitude and min and max longitude values
    • "Acquisition Date": defines the "sensing-start-time" and the (optional) "sensing-stop-time" of interest. Search goes from 00:00:00 of the start date to 23:59:59 of the stop date, or from 00:00:00 to 23:59:59 of the single date. The date can be entered either manually (as YYYY-MM-DD UTC, time specification is not allowed) or by means of the provided Date Selection widget
    • "Orbit Direction": can be used to select the orbit direction by optionally choosing the possible value from the drop-down menu, i.e. "DESCENDING". MERIS data was only acquired in "descending” mode
  • Click on the "Search" button.

The search results can be adjusted as described in Section 2.1.3.2.

2.1.3.2 Search Results Format

The Simple Online Catalogue allows selecting among different response formats by clicking on the "Format" blank field and selecting one of the options from the drop-down menu:

  • "HTML search response": this returns an HTML page with the list of all requested products (ref. to Section 2.1.3.2.1 for further details)
  • "Bulk download lists": this returns an HTML page containing different options to save or view:
    • a Plain text list of download URLs, i.e. a plain text page containing one single download URL per line
    • a Metalink list of download URLs, i.e. an XML text file containing the download metalinks for the matching products
    • an HTML page with the list of all requested products
  • "Plain text metadata index": this returns a plain text page containing the full metadata records for the matched products, encoded in a tab separated value format

It is also possible to set the pagination parameter ("Items per page") to define the maximum number of records per page of the "HTML search response".

2.1.3.2.1 HTML Search Response

The "HTML search response" (see Section 2.1.3.2) contains a list of data items (products) matching the search parameters organised into different pages, each with as many items as indicated in "Items per page".

The displayed list of results contains the data item file name with a link to download the product (which requires authentication), a link to view the associated metadata and a link to the relevant browse image.

By clicking on the file name, the given item will be identified and highlighted on the map zoomed to its extent. Alternatively, by clicking on a given product footprint displayed on the map, the corresponding search record in the list will be highlighted.


3. Download Products

There are different mechanisms to access the data and download the products of interest.

3.1 Download via HTTP

The MERIS data can be accessed and downloaded via HTTP as follows:

  • Login with your own EO Sign In credentials (email address and password)
  • For interactive or individual downloads, select the data of interest by using a search mechanism (ref. Section 2)
  • Download the files by using the product download links

3.2 Download in bulk

It is also possible to perform a download in bulk of a set of data contained in a web page. Note that the maximum number of returned records for each download URL list is limited to 100.

In order to download multiple products all at once, it is suggested to use Firefox or Chrome with the DownThemAll! extension able to automatically parse a list of URLs inputs:

  • Execute a search as described in either File name search or Catalogue search , respectively by selecting "Show search result as URL list" or one of the "Format" options to get a list of download URLs
  • On the result page, select "Tools" > "DownThemAll! Tools" > "DownThemAll!" from the Firefox Browser's Toolbar
  • In the "DownThemAll!" window use the "Filters" or "Fast Filtering" options in order to select ".zip"
  • Select "Start" for immediate download, or "Add paused" and activate the download at wish from the "DownThemAll! Manager" window.

DownThemAll is available for download at https://www.downthemall.org/

Please also refer to the DownThemAll FAQ page at https://www.downthemall.org/howto/faq/


4. Troubleshooting

  • Authentication process

    In case of problems with the authentication process (inconsistent session), you can try to solve the issue by cleaning the cookie cache (Browser memory) or by closing and reopening again your Web Browser.

  • Internet connection performance

    The major constraint on performance is the user's own internet connection which limits the speed of the product download. If you are experiencing issues, try reducing the number of products ordered at the same time.

  • Error messages

    Resource couldn't be accessed / Internal server error / Java exception / Operation timed out

    These error messages usually indicate a temporary connection error or system outage. Try resubmitting the request again after a few minutes. If it still doesn't work, please contact the ESA EO Help Desk.


For further troubleshooting or any other questions, please contact the ESA EO Help Desk.