SatelliteServicesTypes&SatelliteOrbits(Part2)

7/30/2019 SatelliteServicesTypes&SatelliteOrbits(Part2)

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Lecture :- Satellite Services Types & Satellite Orbits (Part 2 )

Satellite Communication

Instructor for the Course

Senan Adel

PHD Student E-Government MIS ( Management Information System engineering )

Msc Telecommunication


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There are three basic categories of non-military satellite services:

1- Fixed satellite services

Fixed satellite services handle hundreds of billions of voice, data, and video transmission

tasks across all countries and continents between certain points on the Earth's surface.

2- Mobile satellite systems

Mobile satellite systems help connect remote regions, vehicles, ships, people and aircraft to

other parts of the world and/or other mobile or stationary communications units, in addition

to serving as navigation systems.

3- Scientific research satellites (commercial and noncommercial)Scientific research satellites provide us with meteorological information, land survey data (e.g.,

remote sensing), Amateur (HAM) Radio, and other different scientific research applications

such as earth science, marine science, and atmospheric research.

Satellite Services Types

Non-military satellite services


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1- Anti-Satellite weapons/"Killer Satellites are satellites that are

designed to destroy enemy warheads, satellites, other space assets.2- Astronomical satellites are satellites used for observation of distant

planets, galaxies, and other outer space objects.

3- Biosatellites are satellites designed to carry living organisms, generally

for scientific experimentation.

4- Communications satellites are satellites stationed in space for the

purpose of telecommunications. Modern communications satellites typicallyuse geosynchronous orbits, Molniya orbits or Low Earth orbits.

5- Miniaturized satellites are satellites of unusually low weights and small

sizes. New classifications are used to categorize these satellites: mini-

satellite (500100 kg), microsatellite (below 100 kg), nano-satellite (below

10 kg).

6- Navigational satellites are satellites which use radio time signalstransmitted to enable mobile receivers on the ground to determine their

exact location. The relatively clear line of sight between the satellites and

receivers on the ground, combined with ever-improving electronics, allows

satellite navigation systems to measure location to accuracies on the order

of a few meters in real time.

Satellite Types


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7- Reconnaissance satellites are Earth observation satellite or communications satellite

deployed for military or intelligence applications. Very little is known about the full power of

these satellites, as governments who operate them usually keep information pertaining totheir reconnaissance satellites classified.

8- Earth observation satellites are satellites intended for non-military uses such as

environmental monitoring, meteorology, map making etc. (See especially Earth Observing

System.)

9- Tether satellites are satellites which are connected to another satellite by a thin cable

called a tether.10- Weather satellites are primarily used to monitor Earth's weather and climate.

11- Recovery satellites are satellites that provides a recovery of reconnaissance,

biological, space-production and other payloads from orbit to Earth.

12- Manned spacecrafts (spaceships) are large satellites able for put human into (and

beyond) an orbit, being on it and recovery back to Earth. Spacecrafts, and orbital parts-

space planes of reusable systems also, has a major propulsion or landing facilities, and

often uses as transport to and from the orbital stations.13- Space stations are man-made orbital structures that are designed for human beings to

live on in outer space A space station is distinguished from other manned spacecraft by its

lack of major propulsion or landing facilities. Space stations are designed for medium-term

living in orbit, for periods of weeks, months, or even years.

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Tether satellites

Space stations

Manned spacecrafts


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Launching and Landing


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The Orbit Path itself can be circular or elliptical .

For Circular Path :-

The height of Satellite is the distance of satellite from earth but

for calculation purpose the height is distance between center

of earth and satellite is taken.

For Elliptical Path :-

This orbit is inclined at an angle of 64 with respect to

equatorial plane.

Orbit Path


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Orbit Types

A- Centric classifications

1- Geocentric orbit : An orbit around the planet Earth, such as the Moon or artificialsatellites. Currently there are approximately 2465 artificial satellites orbiting the Earth.

2- Heliocentric orbit An orbit around the Sun. In our Solar System, all planets, comets, andasteroids are in such orbits, as are many artificial satellites and pieces of space debris.Moons by contrast are not in a heliocentric orbit but rather orbit their parent planet.

3- Areocentric orbit : An orbit around the planet Mars, such as by moons ,or artificialsatellites .

4- Galactocentric orbit : An orbit about the center of a galaxy. Earth's sun follows this type oforbit about the galactic center of the Milky Way.

The general structure of a satellite is that it is connected to the earth stations that arepresent on the ground and connected through terrestrial links.

B- Altitude classifications

1- Low Earth orbit (LEO): Geocentric orbits ranging in altitude from 0

2000 km (0

1240miles)

2- Medium Earth orbit (MEO): Geocentric orbits ranging in altitude from 2000 km (1240miles) to just below geosynchronous orbit at 35786 km (22240 miles). Also known as anintermediate circular orbit.

3- High Earth orbit (HEO): Geocentric orbits above the altitude of geosynchronous orbit35786 km (22240 miles).


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C- Inclination classifications

Inclined orbit: An orbit whose inclination in reference to

the equatorial plane is not zero degrees. Polar orbit: An orbit that passes above or nearly aboveboth poles of the planet on each revolution. Therefore ithas an inclination of (or very close to) 90 degrees.

Polar sun synchronous orbit: A nearly polar orbit that

passes the equator at the same local time on every pass.Useful for image taking satellites because shadows willbe nearly the same on every pass.

most of its time over a designated area of the planet.

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D- Eccentricity classifications

Circular orbit: An orbit that has an eccentricity of 0 and whose path traces

a circle . Hohmann transfer orbit: An orbital maneuver that moves a spacecraft

from one circular orbit to another using two engine impulses. Thismaneuver was named after Walter Hohmann .

Elliptic orbit: An orbit with an eccentricity greater than 0 and less than 1whose orbit traces the path of an ellipse.

Geosynchronous transfer orbit : An elliptic orbit where the perigee isat the altitude of a Low Earth orbit LEO) and the apogee at the altitude ofa geosynchronous orbit.

Geostationary transfer orbit : An elliptic orbit where the perigee is atthe altitude of a Low Earth orbit (LEO) and the apogee at the altitude of ageostationary orbit.

Molniya orbit: A highly elliptic orbit with inclination of 63.4 andorbital period of half of a sidereal day (roughly 12 hours). Such asatellite spends most of its time over a designated area of the planet .

Tundra orbit: A highly elliptic orbit with inclination of 63.4 and orbitalperiod of one sidereal day (roughly 24 hours). Such a satellite spends

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Hyperbolic orbit: An orbit with the eccentricity greater than 1.

Such an orbit also has a velocity in excess of the escape

velocity and as such, will escape the gravitational pull of theplanet and continue to travel infinitely.

Parabolic orbit: An orbit with the eccentricity equal to 1. Such

an orbit also has a velocity equal to the escape velocity and

therefore will escape the gravitational pull of the planet andtravel until its velocity relative to the planet is 0. If the speed of

such an orbit is increased it will become a hyperbolic orbit.

Escape orbit (EO): A high-speed parabolic orbit where the

object has escape velocity and is moving away from the

planet.

Capture orbit : A high-speed parabolic orbit where the

object has escape velocity and is moving toward the planet

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E- Synchronous classifications :-

Synchronous orbit: An orbit where the satellite has an orbital period equal to the

average rotational period (earth's is: 23 hours, 56 minutes, 4.091 seconds) of the body

being orbited and in the same direction of rotation as that body. To a ground observersuch a satellite would trace an analemma (figure 8) in the sky.

Semi-synchronous orbit (SSO): An orbit with an altitude of approximately 20200 km

(12544.2 miles) and an orbital period equal to one-half of the average rotational period

(earth's is approximately 12 hours) of the body being orbited

Geosynchronous orbit (GSO): Orbits with an altitude of approximately 35786 km

(22240 miles). Such a satellite would trace an analemma in the sky.Geostationary orbit (GEO): A geosynchronous orbit with an inclination of zero.

To an observer on the ground this satellite would appear as a fixed point in the sky.

Clarke orbit: Another name for a geostationary orbit. Named after scientist

and writer Arthur C. Clarke.

Super synchronous orbit: A disposal / storage orbit above GSO/GEO. Satellites

will drift west. Also a synonym for Disposal orbit.Sub synchronous orbit: A drift orbit close to but below GSO/GEO. Satellites will

drift east.

Graveyard orbit: An orbit a few hundred kilometers above geosynchronous that

satellites are moved into at the end of their operation.

Disposal orbit: A synonym for graveyard orbit.

Junk orbit: A synonym for graveyard orbit.

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Areosynchronous orbit: A synchronous orbit around the

planet Mars with an orbital period equal in length to Mars'sidereal day, 24.6229 hours.

Areostationary orbit (ASO): A circular areosynchronous orbit

on the equatorial plane and about 17000 km(10557 miles) above

the surface. To an observer on the ground this satellite wouldappear as a fixed point in the sky.

Heliosynchronous orbit : A heliocentric orbit about the Sun

where the satellite's orbital period matches the Sun's period of

rotation. These orbits occur at a radius of 24,360 Gm (0.1628 AU)

around the Sun, a little less than half of the orbital radius of

Mercury.

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1- Sun-synchronous orbit:An orbit which combines altitude and inclination in such a

way that the satellite passes over any given point of the planet's surface at the same

local solar time. Such an orbit can place a satellite in constant sunlight and is useful for

imaging, spy, and weather satellites.

2- Moon orbit: The orbital characteristics of Earth's Moon. Average altitude of 384403

kilometres (238857 mi), ellipticalinclined orbit.

Pseudo-orbit classifications

1- Horseshoe orbit: An orbit that appears to a ground observer to be orbiting a certain

planet but is actually in co-orbit with the planet.

2- Exo-orbit: A maneuver where a spacecraft approaches the height of orbit but lacksthe velocity to sustain it.

3- Suborbital spaceflight: A synonym for exo-orbit.

Special classifications


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Lunar transfer orbit (LTO)

Prograde orbit: An orbit with an inclination of less than 90. Or rather, an

orbit that is in the same direction as the rotation of the primary.

Retrograde orbit: An orbit with an inclination of more than 90. Or rather, an

orbit counter to the direction of rotation of the planet. Apart from those in sun-

synchronous orbit, few satellites are launched into retrograde orbit because

the quantity of fuel required to launch them is much greater than for a

prograde orbit. This is because when the rocket starts out on the ground, it

already has an eastward component of velocity equal to the rotational velocity

of the planet at its launch latitude.

Halo orbit and Lissajous orbit: Orbits "around" Lagrangian points.

Spacecraft bus or service module

Three orbits that a satellite may travel:


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Geostationary Satellite Orbit:-

A geostationary satellite is any satellite which is placed in a geostationary orbit.

Satellites in geostationary orbit maintain a constant position relative to the surface of the earth.

They are often referred to as geosynchronous or just GEO.

Geostationary satellites orbit the earth approximately 22,300 miles above the equator. This

orbital path is called the Clarke Belt, in honor of Arthur C. Clarke. Who was responsible for the

idea that GEO satellites would be ideal for telecommunications relays.

Geostationary satellites are used for weather forecasting, satellite TV, satellite radio and not to

forget, disaster recovery systems for voice communications.

A single geostationary satellite can provide coverage over about 33-40 percent of the planet.

The typical life expectancy of a geostationary satellite is ten to fifteen years.

Because geostationary satellites circle the earth at the equator, they are not able to provide

coverage at the Northernmost and Southernmost latitudes.

Three orbits that a satellite may travel:

LEO, MEO, & GEO


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Geosynchronous Orbit Satellite

When the inclination of the orbit is not zero and/or eccentricityis not zero, it is called geosynchronous.

The period of geosynchronous orbit is equal to period of

revolution of earth with itself.

I means geosynchronous orbit and geostationary orbit have

the same period.


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Differences and Similarities between Geosynchronous and Geostationary

Sr. no Geostationary Orbit Geosynchronous Orbit

1 This orbit is circular This orbit is Not circular

2 This orbit lies is equatorial plane ,

its inclination is zero

This orbit is inclined with respect to equatorial

plane

3 A satellite in this Orbit appears to

be stationary with respect to earth.

A Satellite in this Orbit Appears to Oscillate

with respect to a point on earth.

4 Period of satellite in this orbit is 23

hours 56 min, 4.1 sec

Period of satellite in this orbit is 23 hours 56

min, 4.1 sec

5 There is only one Geostationary

Orbit

There can be many geosynchronous Orbits


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Low Earth Orbit (LEO) refers to a satellite which orbits the earth at altitudes

between 500 and 2000 Km.

Low Earth Orbit satellites travel very quickly to resist the pull of gravity --approximately 17,000 miles per hour. Because of this, Low Earth Orbitsatellites can orbit the planet in as little as 90 minutes.

Low Earth Orbit satellite systems require several dozen satellites to providecoverage of the entire planet, and typically operate in polar orbits.

Low Earth Orbit satellites are used for applications where a short RoundTrip Time (RTT) is very important, such as Mobile Satellite Services

(MSS)

Low Earth Orbit satellites have a typical life expectancy of five to sevenyears.

LEO Satellites


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How LEO Satellite Work ?

Low Earth Orbiting satellites travel in a circular orbit moving frompole to pole, collecting data in a swath beneath them as the earth

rotates on its axis. In this way, a polar orbiting satellite can see

the entire planet twice in a 24 hour period. The United States refers

to their operational LEO satellites as Polar Operational

Environmental Satellites (POES) and maintains ascending (south

to north) and descending (north to south) orbits, each circling the

earth every 12 hours. POES placed into sun-synchronous orbits,

giving the spacecraft a constant relationship to the sun. This way,

images and data can be downloaded by direct broadcast at thesame time each day. Orbiting at around 500 miles from the earths

surface, these satellites result in high resolution images.


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Medium Earth Orbit (MEO) refers to a satellite which orbits the earth at an altitude

below 22,300 miles (geostationary orbit) and above the altitude ofLow Earth Orbit

(LEO) satellites.

Medium Earth Orbit represents a series of tradeoffs between geostationary orbit (GEO)

and Low Earth Orbit (LEO).

Medium Earth Orbit allows a satellite provider to cover the earth with fewer satellitesthan Low Earth Orbit, but require more satellites than that of the geostationary.

Medium Earth Orbit terrestrial terminals can be of lower power and use smaller

antennas than the terrestrial terminals of geostationary orbit satellite systems. However,

they cannot be as low power or have as small antennas as Low Earth Orbit terrestrialterminals.

Medium Earth Orbit satellite systems offer better Round Trip Time (RTT) than

geosynchronous orbit systems, but not as low as Low Earth Orbit systems.

MEO Satellites


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End Of Lecture

Instructor for the Course

Senan Adel

PHD Student E-Government MIS ( Management Information System )

Msc Telecommunication

27 Instructor Senan Adil PHD Student E-

Government (MIS) - MSC Telecom.

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SatelliteServicesTypes&SatelliteOrbits(Part2)