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  1. 1. Satellite and Their Specifications ENVISAT Satellite and Their SpecificationEnvisat ("Environmental Satellite") is an inoperative Earth-observing satellite stillin orbit. It was launched on 1 March 2002 aboard an Ariane 5 from the GuyanaSpace Centre in Kourou, French Guyana, into a Sun synchronous polar orbit at analtitude of 790 km (490 mi) (± 10 km (6.2 mi)).It orbits the Earth in about 101 minutes with a repeat cycle of 35 days. Afterlosing contact with the satellite on 8 April 2012, ESA formally announced the endof Envisats mission on 9 May 2012This European Space Agency (ESA) satellite is the most advanced environmentalspacecraft ever built and the largest civilian Earth observation satellite put intospace.Envisat was an Earth observation satellite. Its objective was to service thecontinuity of European Remote-Sensing Satellite missions, providing additionalobservational parameters to improve environmental studies.In working towards the global and regional objectives of the mission, numerousscientific disciplines currently use the data acquired from the different sensors onthe satellite, to study such things as atmospheric chemistry, ozonedepletion, biological oceanography, ocean temperature and colour, windwaves, hydrology (humidity, floods), agriculture and arboriculture, naturalhazards, digital elevation modelling (using interferometry), monitoring ofmaritime traffic, atmospheric dispersion modelling (pollution), cartography andstudy of snow and ice.The mission is due to be replaced by the Sentinel series of satellites. The first ofthese - Sentinel 1 - is supposed to take over the radar duties of Envisat when it islaunched on 2013.S K Diwakar
  2. 2. Satellite and Their SpecificationsSatellite SpecificationLaunch Date 1 March 2002Launch Vehicle Ariane 5Operational Life 5 years (design), 10 years (achieved)Orbit Polar, Sun-synchronousOrbital Period 100.6 Min.Inclination 98.6 degreeRevolutions Around the 14.7, every 24 hoursEarthAltitude 790 kilometersResolution at Nadir 0.82 meters panchromatic; 3.2 meters multispectralResolution 26° Off-Nadir 1.0 meter panchromatic; 4.0 meters multispectral 11.3 kilometers at nadir; 13.8 kilometers at 26° off-Image Swath nadirEquator Crossing Time Nominally 10:30 AM solar timeRevisit Time Approximately 3 days at 40° latitudeDynamic Range 11-bits per pixelImage Bands Panchromatic, blue, green, red, near IRS K Diwakar
  3. 3. Satellite and Their SpecificationsEnvisat carried an array of nine Earth-observation instruments that gatheredinformation about the Earth (land, water, ice, and atmosphere) using a variety ofmeasurement principles. A tenth instrument, DORIS, provided guidance andcontrol. Several of the instruments are advanced versions of instruments thatwere flown on the earlier ERS 1 and ERS 2 missions and other satellites.MERISMERIS (MEdium Resolution Imaging Spectrometer) measures the reflectance ofthe Earth (surface and atmosphere) in the solar spectral range (390 to 1040 nm)and transmits 15 spectral bands back to the ground segment. MERIS was built atthe Cannes Mandelieu Space Center.AATSRAATSR (Advanced Along Track Scanning Radiometer) can measurethe sea surface temperature in the visible and infrared spectra. Because of itswide angle lens it is possible to make very precise measurements of atmosphericeffects on how emissions from the Earths surface propagate.S K Diwakar
  4. 4. Satellite and Their SpecificationsSCIAMACHYSCIAMACHY (SCanning Imaging Absorption spectroMeter for AtmosphericCHartographY) compares light coming from the sun to light reflected by theEarth, which provides information on the atmosphere through which the Earth-reflected light has passed.SCIAMACHY is an image spectrometer with the principal objective of mapping theconcentration of trace gases and aerosols in the troposphere and stratosphere.Rays of sunlight that are reflected transmitted, backscattered and reflected by theatmosphere are captured at a high spectral resolution (0.2 to 0.5 nm) forwavelengths between 240 to 1,700 nm, and in certain spectra between 2,000 and2,400 nm. Its high spectral resolution over a wide range of wavelengths candetect many trace gases even in tiny concentrations. The wavelengths capturedalso allow effective detection of aerosols and clouds. SCIAMACHY uses 3 differenttargeting modes: to the nadir (against the sun), to the limbus (through theatmospheric corona), and during solar or lunar eclipses.RA-2RA-2 (Radar Altimeter 2) is a dual-frequency Nadir pointing Radar operating inthe Ku band and S bands, it is used to define ocean topography, map/monitor seaice and measure land heights.MWRMWR (Microwave Radiometer) was designed for measuring water vapour inthe atmosphere.DORISDORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite)determines the satellites orbit to within 10 centimetres (4 in).S K Diwakar
  5. 5. Satellite and Their SpecificationsGOMOSGOMOS (Global Ozone Monitoring by Occultation of Stars) looks to stars as theydescend through the Earths atmosphere and change color, which also tells a lotabout the presence of gases such as ozone (O3), and allows for the first time aspace-based measurement of the vertical distribution of these trace gases.GOMOS uses the principle of occultation. Its sensors detect light from a startraversing the Earths atmosphere and measures the depletion of that light bytrace gases nitrogen dioxide (NO2), nitrogen trioxide, (NO3), OClO), ozone (O3) andaerosols present between about 20 to 80 km (12 to 50 mi) altitude. It has aresolution of 3 km (1.9 mi).MIPASMIPAS (Michelson Interferometer for Passive Atmospheric Sounding) is a Fouriertransforming infrared spectrometer which provides pressure and temperatureprofiles, and profiles of trace gases nitrogen dioxide (NO2), nitrous oxide (N2O),methane (CH4), nitric acid (HNO3), ozone (O3), and water (H2O) inthe stratosphere. The instrument functions with high spectral resolution in anextended spectral band, which allows coverage across the Earth in all seasons andat equal quality night and day. MIPAS has a vertical resolution of 3 to 5 kilometres(2 to 3 mi) depending on altitude (the larger at the level of the upperstratosphere).ASARASAR (Advanced Synthetic Aperture Radar) operates in the C band in a widevariety of modes. It can detect changes in surface heights with sub-millimeter precision. It served as a data link for ERS 1 and ERS 2, providingnumerous functions such as observations of different polarities of light orcombining different polarities, angles of incidence and spatial resolutions.S K Diwakar