In this occasion, i want to share about Satellite communication.
First, please look at the picture below,
God created Moon as our Earth satellite.
In order to broading our communication, people tend to use artificial satellite for communication. Based on orbits, these are the type of satellites :
"in this purpose of satellite communication, I will focus in Geo-Stationary Orbit (GSO)"
If we talk about GSO, we must mention this name, Arthur C. Clarke, a Science-Fictionist, which wrote :
"a Satellite with orbital circling at equator plane with radius of 42,242 Km (= altitude of 35,864 Km from earth's surface), should have an equal Period (T) with the Earth's period of rotation."
Thus, the satellite will always seen at a fixed location above the Earth equator.
This orbital circle above the equator is known as Clarke Belt
Geo-Stationary Orbit satellites have some characteristics, which are :
International Telecommunication Union (ITU) officially state that to avoid interference, all GSO satellites are placed minimum 2 degs apart (thus max. only 180 orbital slots/sats available).
Example : Telkom-2 @ 118.0 degE (C-band) and IPSTAR @ 119.5 degE (Ka-Ku band)
'Co'-located satellites (<= 1 deg), are deployed to maximize the utilization of those available (Clarke Belt) orbital slots.
Please note............................only above Earth's equator !
therefore separation of 0.1 deg at Clarke Belt is approximately 73 Km distance.
Signal interference from the 'Co'-located satellites can be prevented using different Polarizations and/or operating Frequencies :
namely :Vertical/Horizontal Linear Polarize and Right-Hand/Left Hand Circular Polarize.....Frequency L, S, C, X, Ku, & Ka-Bands
The signals can be differentiated based on the Polarization or Frequency. Therefore, an Earth Station can also receive signals from two (or more) Co-located satellites without any re-orientation of there Antenna.
The strategy used to prevent collision between the co-located satellites generally uses eccentricity (radial separation) and inclination (latitude separation) vector offsets. This causes the satellites to move in relative motion ellipses about each other as the relative longitude drift between the satellites is near zero. Typical separations between the satellites varies from 1 to 100 kilometers.
Example for this Co-located satellites are Astra 2A, Astra 2B, Astra 2D which orbiting in 28.2 degE.
First, please look at the picture below,
Planets of our Solar System
God created Moon as our Earth satellite.
In order to broading our communication, people tend to use artificial satellite for communication. Based on orbits, these are the type of satellites :
- Low Earth Orbit (LEO) Height : 750-2500 Km, Period : 2 - 2.5 hours
- Medium Earth Orbit (MEO) Height : 7500-10000 Km, Period : 4.5 - 6 hours
- High Earth Orbit (HEO) Height : 15000-20000 Km, Period : 11-12 hours
- Geo-Stationary Orbit (GSO) Height : 36000 Km, Period : 24 hours
- Incline Orbit Satellite (drifting > 0.1 deg. N-S and E-W)
- Polar (mostly very eliptical) orbit satellite
"in this purpose of satellite communication, I will focus in Geo-Stationary Orbit (GSO)"
If we talk about GSO, we must mention this name, Arthur C. Clarke, a Science-Fictionist, which wrote :
"a Satellite with orbital circling at equator plane with radius of 42,242 Km (= altitude of 35,864 Km from earth's surface), should have an equal Period (T) with the Earth's period of rotation."
Thus, the satellite will always seen at a fixed location above the Earth equator.
This orbital circle above the equator is known as Clarke Belt
Geo-Stationary Orbit satellites have some characteristics, which are :
- Stationary/Motionless relative to Earth Location (E/W Longitude ; N/S Latitude)
- Always orbit the globe above the Equator at 35,864 Km from Earth's surface
- The orbit's angular speed and direction matches exactly / Synchronous with our Earth's angular speed and rotation
- Hence, from anywhere on Earth, it looks like a BIRD fixed and still in the sky ("of course until the end of it service live"
)
International Telecommunication Union (ITU) officially state that to avoid interference, all GSO satellites are placed minimum 2 degs apart (thus max. only 180 orbital slots/sats available).
Example : Telkom-2 @ 118.0 degE (C-band) and IPSTAR @ 119.5 degE (Ka-Ku band)
'Co'-located satellites (<= 1 deg), are deployed to maximize the utilization of those available (Clarke Belt) orbital slots.
Please note............................only above Earth's equator !
therefore separation of 0.1 deg at Clarke Belt is approximately 73 Km distance.
Signal interference from the 'Co'-located satellites can be prevented using different Polarizations and/or operating Frequencies :
namely :Vertical/Horizontal Linear Polarize and Right-Hand/Left Hand Circular Polarize.....Frequency L, S, C, X, Ku, & Ka-Bands
The signals can be differentiated based on the Polarization or Frequency. Therefore, an Earth Station can also receive signals from two (or more) Co-located satellites without any re-orientation of there Antenna.
The strategy used to prevent collision between the co-located satellites generally uses eccentricity (radial separation) and inclination (latitude separation) vector offsets. This causes the satellites to move in relative motion ellipses about each other as the relative longitude drift between the satellites is near zero. Typical separations between the satellites varies from 1 to 100 kilometers.
Example for this Co-located satellites are Astra 2A, Astra 2B, Astra 2D which orbiting in 28.2 degE.
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