MEdium Resolution Imaging Spectrometer (MERIS) was one of the main instruments on board the

European Space Agency , owners = , headquarters = Paris, Île-de-France, France , coordinates = , spaceport = Guiana Space Centre , seal = File:ESA emblem seal.png , seal_size = 130px , image = Views in the Main Control Room (1205 ...

(ESA)'s

Envisat Envisat ("Environmental Satellite") is a large inactive Earth-observing satellite which is still in orbit and now considered space debris. Operated by the European Space Agency (ESA), it was the world's largest civilian Earth observation satell ...

platform. The sensor was in orbit from 2002 to 2012. ESA formally announced the end of Envisat's mission on 9 May 2012. Envisat image of a phytoplankton bloom in the Baltic Sea ESA226711

Envisat image of a phytoplankton bloom in the Baltic Sea ESA226711

This instrument was composed of five cameras disposed side by side, each equipped with a

pushbroom A push broom scanner, also known as an along-track scanner, is a device for obtaining images with spectroscopic sensors. The scanners are regularly used for passive remote sensing from space, and in spectral analysis on production lines, for exampl ...

spectrometer A spectrometer () is a scientific instrument used to separate and measure spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomenon where the ...

. These spectrometers used two-dimensional CCDs. One of the sides of the detector was oriented perpendicular to the trajectory of the satellite and simultaneously collected, through the front optics, observations for a line of points at the Earth's surface (or in the atmosphere). The displacement of the platform along its orbit, combined with a short integration time, generated data that was later used to create two-dimensional images. A light dispersing system separated the various wavelengths (colors) composing the incoming radiation at the entrance of the instrument and directed these on the detector along the second dimension, i.e., along-track. These spectrometers acquired data in many spectral bands. For technical reasons only 16 of the bands were actually transmitted to the

ground segment A ground segment consists of all the ground-based elements of a space system used by operators and support personnel, as opposed to the space segment and user segment. The ground segment enables management of a spacecraft, and distribution of p ...

(one of which is required for the low-level processing of the raw data). This instrument thus provided useful data in 15 spectral bands, which were actually programmable in position, width and gain. In practice these technical characteristics were kept constant most of the time to allow many systematic or operational missions. The intrinsic spatial resolution of the detectors provided for samples every 300 m near

nadir The nadir (, ; ar, نظير, naẓīr, counterpart) is the direction pointing directly ''below'' a particular location; that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface. The direc ...

at the Earth's surface, and the pushbroom design avoided or minimized the distortions (e.g., bow tie effects) typical of scanning instruments. This is known as the 'Full Resolution (FR)' product. The more common 'Reduced Resolution (RR)' products were generated by aggregating the FR data to a nominal resolution of 1200 m. The total field of view of MERIS was 68.5

degree Degree may refer to: As a unit of measurement * Degree (angle), a unit of angle measurement ** Degree of geographical latitude ** Degree of geographical longitude * Degree symbol (°), a notation used in science, engineering, and mathematics ...

s around nadir (yielding a swath width of 1150 km), which was sufficient to collect data for the entire planet every three days (in equatorial regions). Polar regions were visited more frequently due to the convergence of orbits. The primary objective of MERIS was to observe the color of the

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...

, both in the open ocean (clear or Case I waters) and in

coast The coast, also known as the coastline or seashore, is defined as the area where land meets the ocean, or as a line that forms the boundary between the land and the coastline. The Earth has around of coastline. Coasts are important zones in n ...

al zones (turbid or Case II waters). These observations were used to derive estimates of the concentration of

chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to a ...

and

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...

s in suspension in the water. It was also used for monitoring and mapping the deposits of seagrass ''

Posidonia oceanica ''Posidonia oceanica'', commonly known as Neptune grass or Mediterranean tapeweed, is a seagrass species that is endemic to the Mediterranean Sea. It forms large underwater meadows that are an important part of the ecosystem. The fruit is free f ...

'', in couple with the airborne HR/VHR (High/Very High Resolution) multispectral sensors for correcting the atmospheric and water column noise attenuation of the reflectance signals which arise from the shallow and turbid sea bottom waters in the

Northern Mediterranean Southern Europe is the southern region of Europe. It is also known as Mediterranean Europe, as its geography is essentially marked by the Mediterranean Sea. Definitions of Southern Europe include some or all of these countries and regions: Alba ...

. These measurements are useful to study the oceanic component of the global

carbon cycle The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and Earth's atmosphere, atmosphere of the Earth. Carbon is the main component of biological compounds as well as ...

and the productivity of these regions, amongst other applications. The characterization of atmospheric properties (gaseous absorption and

aerosol An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be natural or Human impact on the environment, anthropogenic. Examples of natural aerosols are fog o ...

scattering) is essential to derive accurate information over the oceans because they contribute to the bulk of the signal measured (under clear skies) or simply because clouds prevent the observation of the underlying surface. In addition, this instrument is useful to monitor the evolution of terrestrial environments, such as the fraction of the solar radiation effectively used by plants in the process of

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...

, amongst many others applications.

References

External links

Earth Snapshot
- Web Portal dedicated to Earth Observation. Includes commented satellite images, information on storms, hurricanes, fires and meteorological phenomena.
Miravi
- Meris Image Rapid Visualization. MIRAVI shows the gallery of images generated on the Level0 (raw data) Meris Full Resolution (300m) products, few seconds after their availability.
SRRS
- Satellite Rapid Response System. Like MIRAVI but including also ASAR, MERIS Full and Reduced Resolution and ALOS AVNIR2 images.
ESA page on MERIS
Earth observation satellites Oceanographic satellites Spectrometers Satellite imaging sensors Satellite meteorology {{Space-based meteorological observation

See also

References

External links