The satellites are Earth observation tools dedicated to the study and monitoring of our planet. It is based on the objectives of the satellite orbit a particular choice is made. Observation satellites are classified into two broad categories. Geostationary satellites such as Meteosat satellites that are positioned in geostationary orbit at 36,000 km altitude. These satellites are powerful enough to observe at each moment the fifth of the Earth by cons spatial resolution is limited since it is of the order of km. Their apparent immobility can transmit images of the observing site, every 15 minutes, Meteosat 8. The polar orbiting satellites such as SPOT, ENVISAT, JASON, or NOAA evolve in orbits called "low", the order of 800 km. Because of the low altitude, these satellites differ details of the land surface.
The SPOT 5 satellite is equipped with sensors that allow access to a spatial resolution of 5 m or 2.5 m after data processing, for a total field of view of 60 km. A satellite which is at an altitude of 800 km, makes one revolution of the Earth in a hundred minutes. Meanwhile the planet has rotated about 25 degrees, so that the satellite does not iron over the same point, hence its character scrolling. MetOp draws a detailed picture of atmospheric humidity on different channels that relate to different altitudes. The temperature at the surface of the Earth can also be determined as well.
Image: MetOp satellite developed by the European Space Agency (ESA) for EUMETSAT, the European Organisation for the Exploitation of Meteorological Satellites. Credit: ESA - AOES Medialab
ENVISAT (ENVIronment Satellite) is a geostationary satellite dedicated to the monitoring of land resources and responsible for acquiring high-resolution images of the atmosphere, land and ice, in a wide range of spectral bands. The high resolution required to adopt requires small swaths requiring several days of scanning to get a detailed map of the Earth's surface. ENVISAT embarks on this, ten instruments that can operate simultaneously with the imaging sensor. The Envisat mission has been designed by the European Space Agency (ESA). The data produced by Envisat are used in scientific research on Earth and the monitoring of environmental and climatic changes. ENVISAT launch was conducted from 01/03/2002 Kourou base in French Guiana by an Ariane 5 (flight 145). The mission was to continue for an operational life of 5 years but was extended until 2013.
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Image: ENVISAT is at an average altitude of 800 km on a near-circular orbit, inclined 98 degrees to the equatorial plane, which gives the synchronous. Its orbital period is 101 minutes and its orbital cycle is 35 days.
METEOSAT satellite is the best known, because of the daily circulation of her images during weather reports of various news programs. Meteosat at the initiative of France, is Europe's contribution to global observation system dedicated to meteorology and climatology. The first Meteosat was launched 23 November 1977 and operated until 1979. Meteosat-2, launched in 1981 took over, and since then there has been no interruption of service Meteosat, which is managed by the European organization EUMETSAT since 1995. Meteosat-1 to Meteosat-7 are among the first generation of Meteosat satellites. From Meteosat-8 (MSG-1), it produces satellite MSG (Meteosat Second Generation), mostly equipped with a 12-channel radiometer called SEVIRI. Meteosat rotates at 100 rpm around its main axis, a radiometer analysis of surface and converts scanned images are transmitted in real time to the European Space Operations Centre (ESOC) in Darmstadt, Germany.
From an altitude of 35,800 km, Meteosat-9 (MSG-2), above the equator at 0 ° E, just west of Africa, scans the Earth every quarter hour (96 times a day). Meteosat covers Europe, Africa, Middle East, the eastern parts of South America and the Atlantic Ocean and a western Indian Ocean. In 2007, the ESA program celebrated its 30th anniversary in effect the first launch (Meteosat-1) dated November 23, 1977.
Image: View by Meteosat-9 (MSG-2) the Indian Ocean and Asian side of our beautiful and fragile planet.
SPOT (System Probatoire Observing Earth Observation Satellite, or Earth) are a series of civilian satellites observing the earth's surface. Spot Image is a company founded in 1982 by CNES (Centre National d'Etudes Spatiales), IGN and space industry (Matra, Alcatel, SSC). This subsidiary of EADS Astrium is the operator of commercial satellites to Earth observation. Spot Image is working with a network of more than 30 direct receiving stations that receive direct images acquired by SPOT satellites. The SPOT image bank contains more than 20 years of coverage of the planet. This library allows you to easily study the phenomena changing over time and space. Spot-1, was launched February 22, 1986 (Ariane 1), Spot-2, January 22, 1990 (Ariane 40), Spot-3, 26 September 1993 (Ariane 40), Spot-4, March 23, 1998 (Ariane 40, Flight 107), SPOT-5, May 3, 2002 (Ariane 42P, Flight 151).
Image: monitoring the mud volcano in Java, image acquired September 26, 2008 by FORMOSAT-2 1 - Opening the dike east, marked by two white structures. 2 - Drainage of central south basin. The mud flows through the two side channels.
The ocean is vital to the balance of the planet, since it occupies 70% of the land surface, its observation has become an environmental issue. Launched June 20, 2008, the Jason 2 satellite took over in 2008, on the same orbit as its predecessors. It meets the demand of the international programs of study and observation of the oceans and climate across the planet. OSTM mission will provide the scientific community with high-resolution data on ocean currents and their variations and the extent of sea level. Lasting 20 years, this mission is accomplished through a series of satellites, the first is Jason 2. Jason-2 has an expected life of 5 years. With radar altimetry, the height of the seas and oceans the smallest changes are measured to the centimeter.
Jason 1, launched 7 December 2001 by Delta II Jason 2, launched June 20, 2008 by a Delta II launch vehicle from the U.S. base at Vandenberg
Image: Map of significant wave height plotted from data of 4 to 14 July 2008, the satellite Jason-2. Credits: CNES.
Jason is a family of satellite altimetry to measure topography of the ocean, are the successors of TOPEX / Poseidon. The French-US satellite Jason-3 should be launched in 2013 to replace Jason-1 at an altitude of 1336 km. With an inclination of 66 °, this will allow almost total coverage of all ocean free of ice. The measurements of these satellites show that the sea level rises of 3.5 mm per year on average while it rose only 1.7 mm in 1993-1994. The cumulative rise in 20 years is 6 cm. Altimetry measurements from Topex-Poseidon (1992-2005) and Jason-1 (2001) and Jason-2 (2008), as a reference to the IPCC. "The ocean altimetry, in other words the extent of sea level from space with extreme precision over the entire surface of the globe has been a revolution before, it had only local instruments and imprecise: the gauges. " Eric Thouvenot, program manager at CNES Jason-3. Jason combines the best existing altimeters, it is placed in an orbit and allows optimal particular to abstract effects of the tides.
Altimetry technique is based on measuring the instantaneous height of the sea with a radar on board a man-made satellite. The radar wave (around 13 GHz) emitted by the satellite is reflected on the sea surface and is returned on board. The satellite will measure the round-trip time and analyzes the received waveform, allowing respectively to determine the distance between the satellite and the sea surface and the surface roughness. The measurement accuracy depends on the stability of the satellite orbit (1336 km), this altitude puts away the upper layers of the atmosphere that act as a brake. The farther from Earth and the more smooth the disruptive effects of Earth's gravity field as the gravity of the Earth is not uniform, depending on where you stand, gravity is more or less.
Image: LThe orbit of Topex / Poseidon (1992), Jason-1 (2001) and Jason-2 (2008). Control Centre at CNES in Toulouse. Credits: NASA / JPL.
The NOAA (National Oceanic and Atmospheric Administration) weather satellites are Americans who observes the Earth from an altitude of about 820 to 855 km orbit inclined 99 degrees to the equatorial plane. They belong to the observation mechanism established by the World Meteorological Organization whose mission is the observation of meteorological phenomena, mapping the sea surface temperature structure, agro-meteorology, the study of evolution of marine and coastal environment. NOAA was the first satellite put into orbit in 1970, and from, 18 NOAA satellites were launched.
LNOAA operational satellites are out of phase: the same area is flown 4 times daily at intervals of 6 hours in the morning and evening by the satellite even number; night and early this afternoon by the number of satellite odd.
GOCE, launched March 16, 2009, the satellite is the most sophisticated Earth observation satellites to provide information about the gravitational field of the Earth as never before. GOCE data will be essential to obtain precise measurements of ocean circulation and the change in sea level, both affected by climate change. The data will better understand the processes occurring inside the Earth, associated with volcanoes and earthquakes. GOCE (Gravity Ocean Circulation Explorer) first placed on a low-altitude orbit, reached its operational orbit at 259 km altitude, in September 2009. The satellite carries a ton of highly sensitive gradiometer to measure spatial variations in the gravity field in three dimensions. The data collected provide a high resolution map of the "geoid (the reference surface of the planet) and of gravitational anomalies. This map will not only improve our knowledge and understanding of the internal structure of the Earth, but will also be used to provide much data for the study of climate and oceanic circulation. To make this mission possible, ESA, in collaboration with a consortium of 45 European companies led by Thales Alenia Space and the scientific community had to overcome some technical challenges impressive. GOCE is the first in a series of Earth Explorer satellites to be orbited.
Earth Explorer missions have been designed by ESA to promote research on the Earth's atmosphere, biosphere, hydrosphere, cryosphere. Two other Earth Explorer missions are also planned in 2009: SMOS to study soil moisture and ocean salinity and CryoSat-2 will measure the thickness of the ice. Additional missions for Earth Explorer have been designed to address specific topics such as the study of the evolution of the magnetic field (Swarm), whose launch is planned for 2010. ADM-Aeolus will measure atmospheric dynamics in the years 2011 and investigate the radiation balance of the Earth around 2013.
Video: GOCE, the most sophisticated Earth observation satelites.
Picard is a scientific satellite of 150 kg, led by CNES, the French space agency. The satellite was placed on a sun-synchronous orbit June 15, 2010. Its mission is to observe the workings of our Sun and to study its influence on the Earth's climate. This orbit of 725 km, allowing instruments to always see the sun. The satellite should operate at least 2 years. This mission completes a set of solar space missions like SOHO, SORCE, Solar B and STEREO. The mission is named after the French seventeenth century, Jean Picard, the astronomer who measured the diameter of the Sun to determine the eccentricity of the orbit. The distance from the Sun and therefore its apparent size, varies throughout the year and therefore depends on the eccentricity of the orbit. Picard's mission through its instrument SODISM, free of atmospheric turbulence, will provide much more precise measurements. PICARD carries instruments SOVAP (SOlar Variability PICARD), consisting of a differential absolute radiometer and a bolometric sensor to measure the total solar irradiance, PREMOS
(Precision Monitor Sensor), a set of three photometers to study the variability of ozone and observe solar oscillations (helioseismology) SODISM (SOlar Diameter Imager and Surface Mapper), a telescope linked to a CCD imager to measure the diameter and shape of the sun a few milli-arc second, and conduct a survey of the solar interior (helioseismology).
Image: Sun's image taken July 22 by the French small telescope of 11 cm. The telescope is SODISM Picard on board the satellite. "The numerical SODISM made from light captured by the telescope are transmitted by radio frequency to one of six receiving stations Picard project, they then pass to the Control Centre at CNES in Toulouse before being sent to the mission center in Brussels. This is where the image is made from the data decoded and decompressed. ", said François Buisson.