Questions and Answers
Why did the ITU grant all countries the right to an orbital slot directly over their territory?
What is a necessary requirement for installing and operating an earth station or VSAT?
What is the purpose of multiple burns during a GEO satellite launch?
What determines the customization of a satellite's payload?
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What is the estimated cost of launch services for a GEO telecom satellite?
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What is the main objective of the ITU's orbital slot registration?
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Why do some satellites cost as much as $500 million?
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What is the primary benefit of using satellites in communication systems?
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What type of satellite uses GPS technology to provide a person's exact location on Earth?
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What is the transmission of signals to the satellite called?
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What is the advantage of satellite systems utilizing MEO (medium Earth orbit)?
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Why are satellites complementary to cable?
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What is the transmission of information from the satellite called?
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What is one of the benefits of using satellites in communication systems?
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Study Notes
Satellite Operators
- International Mobile Satellite Organization (IMSO) oversees public satellite safety and security communication services via Inmarsat satellites.
- IMSO provides services for maritime safety within the Global Maritime Distress and Safety System (GMDSS), including distress alerting, search and rescue co-ordinating communications, maritime safety information broadcasts, and general communications.
Satellite Services
- The commercial satellite industry provides various services, including:
- Voice/Video/Data Communications
- Position Location
- Rural Telephony
- News Gathering/Distribution
- Internet Trunking
- Corporate VSAT Networks
- Tele-Medicine
- Distance-Learning
- Mobile Telephony
- Videoconferencing
- Business Television
- Remote Sensing
- Pipeline Monitoring
- Security & Database Access
- Emergency Services
- Direct-To-Consumer services, including Broadband IP, DTH/DBS Television, Digital Audio Radio, Interactive Entertainment & Games, and Video & Data to handhelds
Technology Trends
- Market trends for capacity continue to grow despite fibre deployment.
- There is a potential shortage of capacity in some areas due to heavy cutbacks in launches.
- Bandwidth is increasing on a per-link basis.
- User demands include:
- Smaller terminals
- High throughput
- Enhanced capability
- Constellations
- Responsive space
- Lower costs ($1000 or less)
The Space Segment
- A communications satellite has various components, including:
- Propulsion System
- Telemetry, Attitude Control, and Commanding
- Power System/Thermal System
- Solar Arrays
- Receiver Section
- Transponder
- Transmitter Section
- Rx Antennas
- Tx Antenna
- Satellite capacity typically ranges from 24 to 72 transponders, with each transponder capable of handling up to 155 Mbps.
Satellite Design
- Key aspects of satellite design include:
- Electrical Power
- Station Keeping
- Attitude Control
- Orbital Control
- Thermal Control
- Orbital Control involves keeping the satellite stationary with respect to Earth station antennas.
Satellite Orbits
- The ITU Member States have established a legal regime for orbital slot registration.
- The ITU acknowledged that all countries have an equal right to orbital slots.
- Article II of the Outer Space Treaty forbids sovereignty claims over orbital slots.
- Countries have rights to an orbital slot directly over their territory.
Building and Launching a Telecommunications Satellite
- It takes approximately 3 years to build and launch a GEO telecom satellite.
- Satellite payloads are customized for a given mission.
- Satellites undergo extensive testing, including mechanical, thermal, noise, and RF tests.
- The typical cost of a satellite is 150−150-150−250 million, with some costing up to $500 million.
- Launch services and insurance add additional costs (55−55-55−100 million).
Satellite Link Analysis
- A 2 Mbps link using QPSK-3/4 modulation has a required bandwidth of 1.67 MHz and an efficiency of 1.20 bps/Hz.
- The same link using 8PSK-3/4 modulation has a required bandwidth of 1.11 MHz and an efficiency of 1.80 bps/Hz.
- The same link using 8PSK-7/8 modulation has a required bandwidth of 0.95 MHz and an efficiency of 2.10 bps/Hz.
Modcod Selection
- Modcod selection is constrained by signal to noise ratio (SNR) at reception.
- Higher modulation order requires a higher SNR for demodulation.
- SNR is affected by link conditions, available power, satellite performance, antenna size, and modem capabilities.
Satellite Link Budget Analysis
- A satellite link budget analysis determines the suitable modcod, required bandwidth, and power.
Efficiency
- A good efficiency depends on the specific satellite link analysis.
Satellite Communication Components
- A satellite circuit consists of an antenna that transmits/receives and focuses the signal towards/from the satellite.
- The satellite receives signals, filters them, converts frequencies, and amplifies them for transmission.
Benefits of Satellites
- Adaptable to customer requirements
- Mobility
- Cost advantage
- Not affected by geographical obstructions
- Quick implementation
- Alternate routing or redundancy
- Cost is independent of distance
- Cost-effective for short-term requirements
Types of Satellites
- Communications satellites
- Weather satellites
- Earth observation satellites
- Navigation satellites
- Broadcast satellites
- Scientific satellites
- Military satellites
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Description
Learn about the International Mobile Satellite Organization (IMSO), its role in satellite safety and security, and its services within the Global Maritime Distress and Safety System (GMDSS).