Page 21 - RemoteSnsing&GIS by PK Gogoi

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basis of orbital altitude from the earth surface revolution of satellite around the earth with its . Inclined Orbit Satellites (also called Sun-

there are three types of satellites, those are viz. ascending and descending passes, the satellite 2Synchronous Orbit Satellite)

EO (Lower Earth Orbit Satellite) .The sensors record any of these satellite orbits are also sun-
Lorbital height is between 500 to 1500 information of a Msynchronous which means in this orbit,

Km) segment of the the satellite is placed in a way so that the angle
earth surface .
EO (Middle Earth Orbit Satellite ) The between the orbital plane and the line joining
The imaged
Morbital height is between 5000 to Earth and the sun remains constant. Many
portion of the
12000 Km) remote sensing platforms are designed to follow
earth in a an orbit (basically north-south) which, in
EO (Geostationary Earth Orbit
complete cycle covers conjunction with the Earth's rotation (west-
GSatellite). The orbital height is 35,867
hundreds of east), allows them to cover most of the Earth's
Km (approx 36000Km)
k i l o m e t e r s . S u c h surface over a certain period of time. These are
gain , on the basis of inclination of orbital segment of imaged near polar orbits, so named for the
Apalne with respect to the equator, satellites portion by the sensor is inclination of the orbit

are of three categories . Here the term ‘orbit’ called a ‘swath’ . One relative to a line running
refers to the path followed by a satellite (both swath means one between the North and

artificial and natural). The three categories of complete revolution of the satellite around the South poles. Many
satellites are : earth. It is very much likely that of these satellite

1 . Polar Orbit Satellites one after another every synchronous such
orbits are also sun-
new
capturing
swath
. Inclined Orbit Satellites (also called
2Sun-Synchronous Orbit Satellite) portion of the earth due to that they cover each
earth’s own rotation from
. Equatorial Orbit Satellites (also called area of the world at a
west to east. Consequently , after
3Geostationary Satellites or Geosynchronous constant local time of day
a period of time the satellite again overhead on
satellites). called local sun time. At any given
the same location or starting point of the first latitude, the position of the sun in the sky as the
. Polar Orbit Satellites : In polar orbit
swath. The repetitive point of swath is called satellite passes overhead will be the same within
1satellites, satellites are following the north
‘Nidar’ point. The time required by a satellite to the same season. SPOT 4 is on a circular sun-
-south rotation in conjugation with the earth's
complete its orbit cycle is called ‘revisit period’. synchronous orbit at an altitude of 830 km with
rotation (west-east). As the satellite path is
Suppose today at 1st of January 2021, a satellite an inclination of 98.8° with respect to the
north-south over the earth’s west to east rotation
is falling overhead at South equator
,therefore it allows them to cover most of the
Haiborgaon,Nagaon,Near ADP College and it is
Earth's surface over a certain period of time. The
expected that the satellite should again be
movements(path) of satellites is from south to
overhead at the same location after a period say
north pole and from north to south pole
after 21 days. This period is called revisit period
continuously across the equator. Such types
or ‘receptivity. However ’ satellite Revisit
movement of satellite are called ‘ascending’and
period is different from satellite to satellite.
‘descending’ passes respectively. Each