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The purpose of this exercise is to gain familiarity with two different instruments onboard Envisat: the Medium Resolution Imaging Spectrometer (MERIS) and the Advanced Synthetic Aperture Radar (ASAR). You will become acquainted with their potential fields of application and some of their general technical characteristics.
 
In the data zipfile on the right, you will find an Envisat MERIS image in reduced resolution mode of a large part of the Gulf of Mexico. The image was acquired on 28 August 2005, at 15:50 UTC. The data contain all 15 channels:

MERIS_HurricaneKatrina_28-08-2005_ch1.tif
MERIS_HurricaneKatrina_28-08-2005_ch2.tif
MERIS_HurricaneKatrina_28-08-2005_ch3.tif
…
MERIS_HurricaneKatrina_28-08-2005_ch15.tif

 
 

MERIS Channel Number Centre Wavelength / Bandwidth (nm) Application 1 412.5 (purple) / 10 Yellow substance and detrial pigments 2 442.5 (blue) / 10 Chlorophyll absorption maximum 3 490 (blue-cyan) / 10 Chlorophyll and other pigments 4 510 (cyan-green) / 10 Suspended sediment, red tide 5 560 (green) / 10 Chlorophyll absorption minimum 6 620 (orange-red) / 10 Suspended sediment 7 665 (red) / 10 Chlorophyll absorption and fluorescence reference 8 681.25 (red) / 7.5 Chlorophyll fluorescence peak 9 708.75 (NIR) / 10 Fluorescence reference, atmospheric corrections 10 753.75 (NIR / 7.5 Vegetation, cloud 11 760.625 (NIR) / 3.75 Oxygen absorption R-branch 12 778.75 (NIR) / 15 Atmosphere corrections 13 865 (NIR) / 20 Vegetation, water vapour reference 14 885 (NIR) / 10 Atmosphere corrections 15 900 (NIR) / 10 Water vapour, land

 
 
The MERIS sensor’s spectral characteristics found in the table above will be helpful for all of the tasks you will be asked to perform regarding the MERIS image.

In the zip file you will also find an ASAR image in Wide Swath mode acquired on 28 August 2005. By piercing through the clouds of Hurricane Katrina, the ASAR image displays a section of the Gulf of Mexico and shows the shape of the wind-driven sea surface.
 
 

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