European Space Agency (ESA)
MERIS is a passive imaging sensor flying on Envisat which was launched in 2002. Similar to other sensors such as MODIS and AVHRR, it is designed to image the earth at a global and regional scale. The primary mission of MERIS is to monitor oceans and coastal areas, but has many land applications as well. Its land mission is to study the role of terrestrial surfaces in climate dynamics and biogeochemical cycles for climate change.
MERIS has 15 spectral bands within the visible and near infrared range, each capable of gathering data at a resolution of 260m across track x 300m along track. The narrow bands of MERIS make it possible to derive more accurate land cover and vegetation indices than other systems such as AVHRR.
The standard products available through MERIS include: radiance, reflectance, and two vegetation indices known as the MERIS Global Vegetation Index (MGVI) and the MERIS Terrestrial Chlorophyll Index (MTCI). Products at a reduced resolution (1040m x 1160m) can usually be obtained free of charge over the internet, while full resolution products (260m x 300m) usually have to be requested and carry a fee.
MERIS can collect data in two modes. Reduced resolution (1040m across track x 1160m along track) is acquired and processed systematically. Full resolution (260m across track x 300m along track) is only acquired and processed on demand.
|1||0.407-0.417||Yellow substance and detrital pigments|
|2||0.437-0.447||Chlorophyll absorbtion maximum|
|3||0.485-0.495||Chlorophyll and other pigments|
|4||0.505-0.515||Suspended sediment, red tide|
|5||0.555-0.565||Chlorophyll absorbtion minimum|
|7||0.660-0.670||Chlorophyll absorbtion and flourescence reference|
|8||0.677-0.685||Chlorophyll flourescence peak|
|9||0.704-0.714||Flourescence reference, atmospheric corrections|
|11||0.758-0.7625||O2 R-branch absorbtion band|
|13||0.855-0.875||Vegetation, water vapor reference|
|15||0.895-0.905||Water vapor, land|
Swath width of 1150 km Scene Sizes:
Envisat is a polar orbiting satellite with a sun synchronous orbit. It has an altitude of 800 km above the earth and completes global coverage in 3 days.
Images from 2002 to present are available. Level 1B products are top of atmosphere radiance values
Level 2 products provide geophysical information such as reflectance, and vegetation indices based on the fractional absorbed photosynthetically active radiation (FAPAR).
Products obtained over the internet are usually free of charge while new acquisitions carry some cost. Please review the product price list for more detailed information. ESA
To obtain MERIS and other Envisat data, you must register with the ESA. If you seek data that is systematically acquired and archived (reduced resolution), you can do a quick registration and get instant access. If you are interested in full resolution data, you must send a proposal requesting the acquisition, a process that can take up to 8 weeks. Use this link for registration: https://earth.esa.int/web/guest/pi-community/apply-for-data/fast-registration
Once registered, access to systematically acquired and archived data can be found through several on-line portals. https://earth.esa.int/web/guest/data-access/online-archives
If the products you seek are not available from these on-line archives, you must use the EOLI-SA tool. EOLI-SA is a java application used to visually search for and order Envisat data products. The program has to be downloaded and installed. http://earth.esa.int/EOLi/EOLi.html
Detailed information on all Envisat data products. https://earth.esa.int/web/guest/data-access/browse-data-products
Tutorial on how to access Envisat products. http://earth.esrin.esa.it/pub/ESA_DOC/ENVISAT/ENVI87a.pdf
MERIS data comes in the Envisat format which will generally have to be converted to other formats to be useful for remote sensing purposes. Please see the Software/Hardware requirements for further instructions on working with the data.
Working with MERIS data may be challenging because the default format will probably have to be converted to other formats recognized by commercial image software. Below are a few suggestions.
EnviView is a free software tool that displays MERIS and any other data from Envisat. Enviview can only carry out basic operations of visualization, therefore other commercial software packages are needed for detailed data analysis. The program will convert MERIS data to other formats that are more easily read and manipulated by image software programs. These formats include: hierarchical data format (HDF), ASCII, and binary formats. Programs such as Erdas Imagine and ENVI can read these formats. To obtain EnviView, you must send an email request to firstname.lastname@example.org
Basic Toolbox for Envisat AATSR and MERIS (BEAM) is an open source software program intended to compliment the functions of major commercial packages with specific tools developed to handle Envisat MERIS and AATSR products. It has the capability to read common image formats such as Geotiff. http://www.brockmann-consult.de/cms/web/beam/welcome
Still many users will find these formats cumbersome and may prefer formats such as GeoTiff. Tools for carrying out data transformations into other formats and projections can be found at: https://lpdaac.usgs.gov/tools.
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