1. Satellite and Their Specifications
ENVISAT Satellite and Their Specification
Envisat ("Environmental Satellite") is an inoperative Earth-observing satellite still
in orbit. It was launched on 1 March 2002 aboard an Ariane 5 from the Guyana
Space Centre in Kourou, French Guyana, into a Sun synchronous polar orbit at an
altitude 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. After
losing contact with the satellite on 8 April 2012, ESA formally announced the end
of Envisat's mission on 9 May 2012
This European Space Agency (ESA) satellite is the most advanced environmental
spacecraft ever built and the largest civilian Earth observation satellite put into
space.
Envisat was an Earth observation satellite. Its objective was to service the
continuity of European Remote-Sensing Satellite missions, providing additional
observational parameters to improve environmental studies.
In working towards the global and regional objectives of the mission, numerous
scientific disciplines currently use the data acquired from the different sensors on
the satellite, to study such things as atmospheric chemistry, ozone
depletion, biological oceanography, ocean temperature and colour, wind
waves, hydrology (humidity, floods), agriculture and arboriculture, natural
hazards, digital elevation modelling (using interferometry), monitoring of
maritime traffic, atmospheric dispersion modelling (pollution), cartography and
study of snow and ice.
The mission is due to be replaced by the Sentinel series of satellites. The first of
these - Sentinel 1 - is supposed to take over the radar duties of Envisat when it is
launched on 2013.
S K Diwakar

2. Satellite and Their Specifications
Satellite Specification
Launch Date 1 March 2002
Launch Vehicle Ariane 5
Operational Life 5 years (design), 10 years (achieved)
Orbit Polar, Sun-synchronous
Orbital Period 100.6 Min.
Inclination 98.6 degree
Revolutions Around the
14.7, every 24 hours
Earth
Altitude 790 kilometers
Resolution at Nadir 0.82 meters panchromatic; 3.2 meters multispectral
Resolution 26° Off-Nadir 1.0 meter panchromatic; 4.0 meters multispectral
11.3 kilometers at nadir; 13.8 kilometers at 26° off-
Image Swath
nadir
Equator Crossing Time Nominally 10:30 AM solar time
Revisit Time Approximately 3 days at 40° latitude
Dynamic Range 11-bits per pixel
Image Bands Panchromatic, blue, green, red, near IR
S K Diwakar

3. Satellite and Their Specifications
Envisat carried an array of nine Earth-observation instruments that gathered
information about the Earth (land, water, ice, and atmosphere) using a variety of
measurement principles. A tenth instrument, DORIS, provided guidance and
control. Several of the instruments are advanced versions of instruments that
were flown on the earlier ERS 1 and ERS 2 missions and other satellites.
MERIS
MERIS (MEdium Resolution Imaging Spectrometer) measures the reflectance of
the 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 at
the Cannes Mandelieu Space Center.
AATSR
AATSR (Advanced Along Track Scanning Radiometer) can measure
the sea surface temperature in the visible and infrared spectra. Because of its
wide angle lens it is possible to make very precise measurements of atmospheric
effects on how emissions from the Earth's surface propagate.
S K Diwakar

4. Satellite and Their Specifications
SCIAMACHY
SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric
CHartographY) compares light coming from the sun to light reflected by the
Earth, 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 the
concentration of trace gases and aerosols in the troposphere and stratosphere.
Rays of sunlight that are reflected transmitted, backscattered and reflected by the
atmosphere are captured at a high spectral resolution (0.2 to 0.5 nm) for
wavelengths between 240 to 1,700 nm, and in certain spectra between 2,000 and
2,400 nm. Its high spectral resolution over a wide range of wavelengths can
detect many trace gases even in tiny concentrations. The wavelengths captured
also allow effective detection of aerosols and clouds. SCIAMACHY uses 3 different
targeting modes: to the nadir (against the sun), to the limbus (through the
atmospheric corona), and during solar or lunar eclipses.
RA-2
RA-2 (Radar Altimeter 2) is a dual-frequency Nadir pointing Radar operating in
the Ku band and S bands, it is used to define ocean topography, map/monitor sea
ice and measure land heights.
MWR
MWR (Microwave Radiometer) was designed for measuring water vapour in
the atmosphere.
DORIS
DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite)
determines the satellite's orbit to within 10 centimetres (4 in).
S K Diwakar

5. Satellite and Their Specifications
GOMOS
GOMOS (Global Ozone Monitoring by Occultation of Stars) looks to stars as they
descend through the Earth's atmosphere and change color, which also tells a lot
about the presence of gases such as ozone (O3), and allows for the first time a
space-based measurement of the vertical distribution of these trace gases.
GOMOS uses the principle of occultation. Its sensors detect light from a star
traversing the Earth's atmosphere and measures the depletion of that light by
trace gases nitrogen dioxide (NO2), nitrogen trioxide, (NO3), OClO), ozone (O3) and
aerosols present between about 20 to 80 km (12 to 50 mi) altitude. It has a
resolution of 3 km (1.9 mi).
MIPAS
MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) is a Fourier
transforming infrared spectrometer which provides pressure and temperature
profiles, and profiles of trace gases nitrogen dioxide (NO2), nitrous oxide (N2O),
methane (CH4), nitric acid (HNO3), ozone (O3), and water (H2O) in
the stratosphere. The instrument functions with high spectral resolution in an
extended spectral band, which allows coverage across the Earth in all seasons and
at 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 upper
stratosphere).
ASAR
ASAR (Advanced Synthetic Aperture Radar) operates in the C band in a wide
variety 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, providing
numerous functions such as observations of different polarities of light or
combining different polarities, angles of incidence and spatial resolutions.
S K Diwakar