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Reference documents
MERIS Product Handbook
MERIS Product Handbook
MERIS Product Handbook
MERIS Credits
MERIS Data Formats Products
MERIS Glossary and reference documents
Optics Glossary
Vegetation Glossary
Water Vapour Glossary
Ocean Colour Glossary
Neural Network Glossary
Meteorology Glossary
Cloud Glossary
Atmosphere Glossary
Product Glossary
Geometry Glossary
Acronyms and Abbreviations
MERIS Instrument
Instrument Characteristics and Performance
MERIS Quality Status
Instrument characteristic
Characterisation and Calibration
Onboard Calibration Hardware
Calibration Modes
Instrument Description
Instrument model philosophy
Instrument Concept
Digital processing Unit
Video Electronic Unit
Detection Focal Plane
Instrument optics
The MERIS instrument
MERIS Products and Algorithms
Auxiliary Files
Common Auxiliary Datasets
Auxiliary Datasets for Level 2 Processing
Auxiliary Datasets for Level 1b Processing
Summary of Auxiliary Datasets
Water Vapour Parameters Data File
Atmosphere Parameters Data File
Level 2 Control Parameters Data File
Aerosol Climatology Data File
Coastline/Land/Ocean Data File
Digital Roughness Model Data File
Radiometric Calibration Data File
MERIS Level 1b Control Parameters Data File
Digital Elevation Model
ECMWF Data Files
ENVISAT Orbit Data Files
Surface Confidence Map File
Land Vegetation Index Parameters Data File
Cloud Measurement Parameters Data File
Ocean II Parameters Data File
Ocean I Parameters Data File
Land Aerosols Parameters Data File
Ocean Aerosols Parameters Data File
MERIS Instrument Data File
MERIS-Specific Topics
Level 2 Products and Algorithms
Level 2 Products
Level 2 Geophysical Products
Annotation data set
Water Vapour products
Land products
Meris Terrestrial Chlorophyll Index
Meris Global Vegetation Index
Aerosol Angström Coefficient
Aerosol optical thickness
Cloud products
Cloud reflectance
Cloud Type
Cloud top pressure
Cloud albedo
Cloud optical thickness
Ocean products
The MERIS Aerosol Angström Coefficient
Aerosol optical thickness
Photosynthetically Active Radiation (PAR)
Yellow substance
Suspended matter
Algal Pigment Index II
Algal Pigment Index I
Normalized water leaving radiance / reflectance
Product description
Level 2 High-Level Organisation of Products
Full Resolution Geophysical Product
Extracted Vegetation Indices
Extracted Cloud Thickness and Water Vapour for Meteo Users
Extracted Cloud Thickness and Water Vapour
Reduced Resolution Geophysical Product
Level 2 Algorithms
Level 2 Accuracies
Level 2 Algorithm Description
MERIS Level 2 Product Formatting Algorithm
Measurement Data Sets
Annotation Data Set "Tie Points Location and corresponding Auxiliary Data"
Global Annotation Data Set - Scaling Factors
Annotation Data Set "Summary Product Quality"
Specific Product Header
Main Product Header
MERIS Land Pixels Processing
MERIS Bottom Of Atmosphere Vegetation Index (BOAVI) (step 2.8)
Atmospheric correction over land (step 2.6.23)
MERIS Top Of Atmosphere Vegetation Index (TOAVI) (step 2.2)
Water Processing
MERIS Ocean Colour Processing (step 2.9)
Clear water atmospheric corrections (step 2.6.9)
Turbid water screening and corrections (steps 2.6.8, 2.6.10)
Water Confidence Checks (step 2.6.5)
Cloud Processing
Cloud type processing (step 2.4.8)
Cloud Optical Thickness processing (step 2.4.3)
Cloud Albedo processing (step 2.4.1)
Total Water Vapour Retrieval
Water vapour polynomial (function)
Range checks (steps 2.3.0, 2.3.6)
Water vapour retrieval over clouds (step 2.3.3)
Water vapour retrieval over water surfaces (steps 2.3.2, 2.3.5)
Water vapour retrieval over land surfaces (step 2.3.1)
MERIS Pixel Identification
Land Identification (step 2.6.26) and Smile Effect Correction (step 2.1.6)
Gaseous absorption corrections (step 2.6.12)
Stratospheric Aerosol Correction (step 2.1.9)
Cloud screening (steps 2.1.2, 2.1.7, 2.1.8)
MERIS Pressure Processing
Atmospheric pressure confidence tests (steps 2.1.2)
Atmospheric pressure estimate (steps 2.1.5, 2.1.12)
MERIS Pre-processing
Pre processing step
Level 1b product check
Level 2 Physical Justification
Level 1b Products and Algorithms
Level 1b product definition
Browse Products
Level 1b Essential Product Confidence Data
Level 1b Engineering Quantities
Level 1b Accuracies
Level 1b High-Level Organisation of Products
Measurement Data Sets
Annotation Data Set "Product Quality"
Annotation Data Set "Tie Points Location and corresponding Auxiliary Data"
Global Annotation Data Set
Specific Product Header
Main Product Header
Full Resolution Geolocated and Calibration TOA Radiance
Reduced Resolution Geolocated and Calibration TOA Radiance
Level 1b Algorithms
External Data Assimilation
Pixel Classification
Stray Light Correction
Radiometric Processing
Saturated Pixels
Source Data Packet Extraction
Level 0 Products
Product Evolution History
Definitions and Conventions
Notations and Conventions
Product Grid
Organisation of Products
MERIS product data structure
File naming convention
Acquisition identification scheme
Product identification scheme
Latency, Throughput and Data Volume
MERIS products overview
MERIS product types
Full and reduced resolutions
MERIS product processing levels
MERIS User Guide
Image gallery
How to Use MERIS Data
Software Tools
General Tools
How to Choose MERIS Data
Summary of Applications vs. Products
Special Features of MERIS
Geographical Coverage
Principles of Measurement
Scientific Background
Mission Objectives
MERIS Level 3 products
Geophysical Measurements
MERIS Product Handbook
Site Map
Frequently asked questions
Terms of use
Contact us


1.1.3 Principles of Measurement

MERIS is a passive imaging spectrometer, which performs simultaneously spatial and spectral imaging of the Earth, by looking in the nadir direction.

The most outstanding characteristics of MERIS, detailed below, are:

· MERIS is a push-broom instrument.

· The InFOV is 68° +1°/-0.1°, which equates to a swath width of 1150 km centred around the subsatellite point.

· The 15 observed spectral bands are all programmable in position and width.

· Two spatial resolutions can be selected.

· Onboard processing can be performed on the image data.

· The polarisation sensitivity of MERIS is very low.

· MERIS has a high radiometric and spectrometric performance.

The InFOV is divided into five segments, each of which is imaged by one of the corresponding five cameras. A slight overlap exists between the FOVs of adjacent optical cameras. An area Charge-Coupled Device (CCD) detector is used, with an instantaneous detector element FOV of 1.149 arcmin.

Spatial Imaging

Spatial imaging is achieved using the push-broom principle: the across-track sampling is performed electronically and the along-track sampling is made thanks to the satellite motion. (See the figure below.)

A spatially bi-dimensional image is obtained by the gathering and the on-ground processing of subsequent images as ENVISAT moves along track.

MERIS measures the reflected solar radiation from the Earth's surface and clouds, in the visible and near-infrared spectral regions. Therefore, observation is nominally limited to the day side of the Earth, in particular the angular observation range is limited to a Sun zenith angle of less than 80 degrees at the subsatellite point. Figure 1.5 illustrates the instrument's FOV, swath dimension and camera tracks:

Figure 1.6 - MERIS FOV, camera tracks, pixel enumeration and swath dimension

Spectral Imaging

The observation is performed simultaneously in 15 programmable spectral bands, ranging from the visible to the near infrared (390 nm to 1040 nm). Each of these 15 bands is programmable in position and in width.

Spatial Resolution

MERIS is able to deliver:

· Reduced spatial resolution data

· Reduced and full spatial resolution data simultaneously

These two spatial resolutions, for the nominal orbit are:

· for full spatial resolution: 290 m × 260 m at subsatellite point

· for reduced spatial resolution: 1.2 km × 1.04 km at subsatellite point

An reduced spatial resolution pixel is obtained by averaging the signal of 16 full spatial resolution pixels. More precisely, 4 adjacent pixels across-track for 4 successive pixel lines along-track are used.

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry