itu satellite symposium - geneva, switzerland 28th to 30th ... · bus systems communication payload...

ITU Satellite Symposium - Geneva, Switzerland 28th to 30th November 2018

SATELLITES AND LAUNCH VEHICLES

Content for GVF Advanced Satellite System Engineering Classroom Session-s

© Mahdi Bagh Computers Private Limited, All rights reserved. May not be copied or distributed in either hard or soft copy form without express written permission. [email protected] www.mbcin.com

Satellite Systems


© Mahdi Bagh Computers Private Limited, All rights reserved. May not be copied or distributed in either hard or soft copy form without express written permission. [email protected] www.mbcin.com 4.2

Satellite Functional Areas


Fully deployed satellite as it appears in orbit for launch

Stowed configuration



Functional AreasA satellite is mainly divided into 2 functional areas –

Needs an introduction.

Bus Systems Communication Payload System

Communication Payload SystemBus Systems



Functional AreasBus Systems

The Bus system consists of all the elements which supports the communication payload.

This is divided into two classes -

Mechanical

Electrical

Structural Systems Deployment Mechanisms Thermal Systems Propulsion Systems

Telemetry, Tele-command and

Communication Systems (TTC)

Power Generation, Control and Distribution

System

Attitude Control Systems and Sensors



Functional Areas

Communications Payload

The communication payload supports all the functional aspects of the mission for which the

satellite is launched. This consists of –

Communications Systems

Antennas

Receivers Multiplexers &Demultiplexers Filters

Power Amplifiers Gain Control Switching Matrices


Transparent or “bent pipe”

repeater


Regenerative repeater with on-board processing



Functional AreasStructural Systems

The structure provides the basic mechanical support for the satellite

systemsThe structure should provide the stiffness and the strength requirements to

withstand the vibrations and acoustic loads which occur during launch phase.It should also provide distortion

free platform for mounting various subsystems, specially the antennas which will face extreme temperature in the space environment.Figure 092-4-6— SPOT 6 Satellite structure & wiring in progress. (Image: Airbus Defence & Space)



Functional AreasMechanismsDuring launch operations, the satellite is kept

on top of the launch vehicle.

In order to isolate the satellite from electrodynamic heading during the launch

phase the satellite is kept in a heat shield, the dimensions of the heat shield are constrained by the dynamics of the launch vehicle.

Figure 093-4-8— Heat Shield GSAT09 (Image: ISRO)



Functional AreasMechanisms

Most of the important elements, like the solar arrays and antennas, are folded

so that they occupy the least volume during launch phase.

These panels and the antenna require to be deployed in the full configuration of the

satellite.

Mechanisms are used to achieve this goal. As these mechanisms are one-shot operation

they should be most reliable.Figure 094-4-9— NASA Engineers test Juno’s solar panels (Image: Wikipedia)



Functional AreasThermal SystemsIn the space environment, the satellite in orbit sees extreme

temperature. • When the satellite is in the shadow region it sees temperatures

close to absolute zero ( 5 – 6 K).• When the satellite is facing the sun it sees temperatures up to a

few thousand degrees centigrade.The life and the reliability of these electronic systems have a great influence on the temperature of operations and the

inside of the satellite have to be kept between 0 – 40 C.



Functional AreasThermal Systems

The design takes care of dissipation of heat from various elements inside the satellite, which are not always constant

and vary with time and operational requirements.

This thermal design is achieved by using various elements like OSRs, thermal blankets and using various paints and tapes

with different absorption and emission coefficients.



Functional AreasPropulsion SystemsGenerally, the launch vehicle leave the spacecraft in an

elliptical orbit with one point being geosynchronous satellite orbit point.The propulsion system in the spacecraft, which include

liquid apogee motor and control thrusters, are used to bring the satellite to the required longitude and arrest the satellites movement to make it a geostationary satellite.This system also carries the required fuel to maintain

the satellite in this position during its life and also to recover this satellite position in any contingency arising due to the loss of attitude.



Functional AreasTele command, Telemetry and Communication Systems

The basic functions of the TTC are to send commands for various operations and

contingency recoveries. The function of the telemetry is to monitor the health parameters of the spacecraft.

Communication system is the microwave link to carry the functions and is also used to measure

the range and range rate of the satellite which helps in the orbital determination.

Figure 095-4-14— Telecommand & Telemetry (Image: SHH)



Functional AreasTTC Sub-Systems

Figure 096-4-15— TTC Subsystems (Image: SHH)

Generally the TTC systems operate in the same frequency as the communication frequency band. During the initial launch phase, the TTC systems require

the support from the world wide communication systems which help it to control and guide the satellite to its final position.The command and telemetry systems are encrypted and

there is provision for error detection so that no wrong command will reach the spacecraft.The current satellites use a CCDS format for both

command and telemetry. This is a packet based system.



Functional AreasPower SystemsThe satellite in orbit has to generate

its own power in order to support the communication payload and the bus systems.During eclipse, which occurs for

about 90 days with a period varying from few minutes to 72 minutes, power is required for satisfactory operation of the satellite systems.Rechargeable storage batteries are

used in the satellite system for taking care of the power requirements during an eclipse and during any contingencies.

Solar panels continuously track the sun for producing maximum power.

They also recharge the batteries and are mounted on the N-S faces of the satellite.



Functional AreasAttitude and Orbit Control

SystemsTO EARTH’S

CENTRETO EARTH’S

CENTRE

YAW ROTATIONYAW ROTATION

PITCH ROTATIONPITCH ROTATION

ROLL ROTATIONROLL ROTATION

SATELLITE ORBITSATELLITE ORBIT

Figure 102-4-22— 3-Axis Stabilization (Image: SHH)

The orientation of the spacecraft in space is essential for telecommunication satellites. The high precision

control in orbit is carried by the Attitude and Orbit Control System (AOCS).When this spacecraft is parked in its final position, the

AOCS helps it to maintain and orient the spacecraft to realise its full potential for optimal performance of the communication system.

AOCS consists of • Sensors, • Propulsion systems,• Actuators, and,• Control electronics



Functional AreasSensorsThere are various sensors on the

spacecraft which determine the orientation of the spacecraft with respect to either Earth or the Sun.These sensors, working along with

actuators, orient and maintain the spacecraft in the desired direction for the final mission objectives.Some of these sensor types are Earth

sensors, Sun sensors, and Star sensors.Sensors are chosen depending on the

location and accuracy requirements.Figure 103-4-23— Coarse Sun Sensor (Image: ESA)

https://artes.esa.int/projects/tno-coarse-sun-sensor-using-european-cells



Functional AreasActuators

These consist of small control thrusters, momentum and reaction wheels, and

magnetic torquers which, working along with sensors and AOCS electronics, maintain the satellite in its orbital position and appropriate orientation.

Figure 104-4-24— 10N Bipropellent Thruster (Image: ESA)



Functional AreasControl Electronics

This consists of the electronic circuitry and the algorithms necessary to

receive the data about orientation of the spacecraft and apply corrections wherever required by using the actuators and other propulsion elements.

Besides there are several contingencies that the satellite may face during

its entire life and appropriate and well documented procedures are used for controlling the spacecraft and its safe operation for the entire life.



Functional AreasCommunication Systems

Communication payload is the ultimate requirement of the satellite and it consists of –

• Antennas,• Filters,• Receivers,• De-multiplexers,• Power amplifiers,• Multiplexers,• Redundant switching elements

All these elements are designed to read the communication mission objectives and their

complexity and configuration are decided by the communication requirements.



Functional AreasCommunication SystemsThere are several factors which decides the life of a

satellite in orbit.• The fuel to be carried for various orbital and

orientation corrections• Degradation in the power generation capabilities or

the solar cells used• Storage capabilities of the batteries• Thermal control of the systems due to degradation of

the thermal control elements used• Limitation of life of high power RF elements like

TWTA in communication payloads

The system design is optimized in such a way that all these degradations will occur nearly at the same

time in order to optimize the system.



Life of a Satellite

There are several factors which decide the life of a satellite in orbit.

• The fuel to be carried for various orbital and orientation corrections.

• Degradation in the power generation capabilities or the solar cells used.

• Storage capabilities of the batteries.• Thermal control of the systems due to degradation of the

thermal control elements used.• Limitation of life of high power RF elements like TWTA in

communication payloads.

The system design is optimized in such a way that all these degradations will occur

nearly at the same time in order to optimize the system.

Average Life of a Satellite

15 Years



satellite system cost

The cost of the satellite system depends on the following factors –

• Satellite cost• Launch vehicle cost• Insurance cost• Maintenance cost over its life

Launch cost becomes a major contributor to the overall cost of the satellite system.

Recent developments indicate that the launch costs will reduce by 20 – 30% due

to launch vehicle reuse.The satellite bandwidth cost depends on

the amount and complexity of the payload being carried.The high throughput satellites which are launched recently have capacity up to 30GB. This

reduces the cost of the band width and becomes comparable to the costs in terrestrial systems.

SATCOM SYSTEM VALUE-CHAIN


Earth Station Operator

SPACE INDUSTRY VIEW:

Launch Vehicle

Satellite system Integrator

Subsystem, Component Suppliers

Ground segment Earth Station

Subsystem, Component Supplier

Satellite Operator

Satellite communication Service Provider

Satellite Broadcast Service Provider

User Equipment Supplier

User Equipment Suppliers


Space Economy

▪ Satellite technology from its early inception to provide basic services has evolved into a huge industry benefiting the economy.

▪ Full range of activities and the use of resources that create and provide the value-chain

▪ Space related products and services – public and private participators

- Research and development - manufacture and use of space infrastructure - Space enabled applications( navigation equipment, satellite phones, launch vehicles and satellites etc) - Scientific knowledge generated activities

- Space derived products , services and knowledge


Satellite Commercial Industry – Mature Sectors

• Satellite Manufacturing – subsystem manufacturing, integration services

• Launch Services and launch vehicles

• Satellite DTH TV – By far the largest sector in global economy

• Satellite Radio – Established market in US

• Satellite Broadband – Growing market

• FSS Transponder Leasing - Competing market with terrestrial fibre.

• FSS Managed Services

Refers to FSS sub-sector in internal networks for businesses and govt. agencies as well as mobility services such as internet service to aircraft, passenger cabins.

Mobile Communication – Regional & Global GEOs, LEOs services Earth Observation:

Sate of imagery – expanding list of applications, state of art sensor development & deployment and build sales growth to generate revenue.


• Consumer Ground Equipment

• GNSS Device, Chipsets, and Applications:

GNSS-based positioning, navigation, and timing services – development of

high-end products, software.

Ground Equipment:

Network equipment, Consumer equipment for GNSS, satellite TV, Radio,

Broadband and Mobile.


Space Manufacturing

Launch vehicles and systems

Satellites, payloads, spacecraft

Ground segment systems and equipment

Scientific and engineering research

and consultancy

Space Operations

Launch provision and brokerage services

Proprietary satellite operation (incl. sale/lease of capacity)

Third-party ground segment operation

Space Applications

Direct-To-Home(DHT) provision

Very Small Aperture Terminal(VSAT) network

provisionValue-Added Resale (VAR)

Value-Added Services (VAS)

User equipment supply

Users

Security, safety & resilience

Game-changing services

Climate and environmental services

More efficient public sector services

e-Connectivity

Non-users

R&D and knowledge spillovers

ExternalitiesAncillary services

Financial and legal services

Insurance and brokerage services Consultancy and applied research

Other support products and services

Regulatory Considerations &

Interference Reduction


Regulatory Philosophy:

ITU regulation of international telecom in two basic areas –

- Spectrum Management(ITU-R)

- Telecommunication Standards(ITU-T)

• Area of interest to Satcom is ITU-R management of the radio spectrum which plays a critical role by providing rules to be followed by individual countries and operators of radio transmitters.

• Individual countries and radio operators need rules to avoid interference

• Through international conferences, technical recommendations, and its full time spectrum management activities the ITU oversees the use of radio frequencies and provides forum for interference resolution.

• ITU-T is in the interfacing of telecom networks with one another ie telephone, data, and other networks.


ITU Sectors and Bodies

Structure of ITU – main branches of Radio

Communication Sector


SATELLITE FREQUENCY BANDS:

Many Applications of satellite technology – Not only for radio communication, but used for astronomy, weather forecasting, broadcasting, mapping and many more.

Band designations developed for easy reference only.

DESIGNATION FREQUENCY RANGE & USE

L-BAND 1 – 2 GHz Global Positioning Carriers, Satellite mobiles at sea,land and air, satellite Radio

S-BAND 2 – 4 GHz Communication Satellites, Weather radar, Surface ship radar

C-BAND 4 – 8 GHZ Primarily used for Satcom.

X-BAND 8 – 12 GHZ Primarily used by Military. Used in Radar applications in civil, military and govt. institutions for weather monitoring, air traffic control, maritime traffic control, defense tracking and vehicle speed detection for law enforcement.

Ku-BAND 12 – 18 GHZ used for Satellite communications

Ka-BAND 26 – 40 GHz Communication satellites, High-resolution & close-range targeting radars on military aircraft


DEFINITIONS OF RADIO COMMUNICATION SERVICES:

SERVICE Definition by ITU-RR ( Radio Regulations)

FSS

C, X,Ku ,Ka Bands

Used between fixed point or points within specified areas. In some cases this service includes satellite-to-satellite links ,which may also be operated in the inter-satellite service.

This service may also include feeder links for other space radiocommunication services.

BSS

S, Ku,Ka Bands

Used to transmit signals by space stations that are intended for direct reception by general public.

The term “direct reception” shall encompass both individual reception and community reception.

MSS

L,L/S,S Bands

Used between mobile earth stations and one or more space stations, or between space stations used by this service.

This service may also include feeder links necessary for its operation.



ITU & Telecom SatellitesFrequency Allocation

Allocation is the identification of the frequency band for various communication applications and is

given in the frequency allocation table of the ITU which are finalized by the world body by discussions and in meeting called World Radio Conferences (WRC)

In the frequency allotment table certain frequency band may be allotted for different communication services.

These are called primary and secondary services.


SERVICE BAND

Typical frequency(GHz)

UPLINK DOWNLINK

FSS

C

X

Ku

Ka

5.85–7.075 3.4–4.2

7.90–8.40 7.25–7.75

13.75–14.8 10.7–11.7

28.0–30.0 17.7–19.7

BSS

S

Ku

Ka

2.65–2.69 2.5–2.54

17.7–18.2 11.2–12.2

24.75–25.25 21.4–22.0

MSS

L

L/S

S

1.626–1.66 1.525–1.56

1.61–1.626 2.483–2.5

2.67–2.69 2.5–2.52

ITU-RR General frequency Ranges Not Specific Regions:


PRIMARY & SECONDARY SERVICE ALLOCATION:

• Frequency Allocations recognises two levels of priority.

• The primary service has the highest level of rights to operate in the particular band.

• A secondary service shall not cause harmful interference to stations of primary service to which frequencies are already assigned.

• There can be more than one primary service in the same band. In this case the two must coexist through prescribed sharing criteria and frequency coordination procedures.

• On first complaint from a primary user the secondary user must be prepared to cease transmission, otherwise the user can continue to operate.

• Unlicensed applications such as cordless phones, wireless data networks(802.11b), and family radios are operating as secondary services and are under these rules.




Primary services may be allotted for more than one application. And the country’s administration will

decide which application will be used in their territory.Secondary services are defined as follows – • Shall not cause harmful interference to stations of primary services to which

frequencies are already assigned or to which frequencies may be assigned at a later date.

• Cannot claim protection from harmful interference from stations of a primary service to which frequencies are already assigned or may be assigned at a later date.

• Can claim protection, however, from harmful interference from stations of the same or other secondary services to which frequencies may be assigned at a later date.Allotment is identification of particular frequency by

each national frequency allotment authority for use in that particular country.




The geostationary orbit satellites operate on the equatorial plane and the pane has only 360 degrees

As two satellites operating in the same frequency can not be very near to each other due to interference,

there are some restrictions between the satellite separations in the equatorial orbital plane to avoid interference.The orbital separation depends on the frequency of

operation and the area covered. Hence, there is a lot of demand for orbital space for geostationary satellites. Figure 112-5-14— “Bee-hive” of satellites around the earth (Image: NASA)


Frequency Spectrum – Satellite Communication and other radio communication services


Orbit-frequency Spectrum and Interferences:

The international rules that govern the use of frequency spectrum and the orbits either GEO or Non-GEO stipulate that the system will neither cause or receive. Interference in satellite communication is one of the key determinants of system capacity and performance.

Harmful interference: Affecting Radio navigation or of safety services, other radio communication services.

Unacceptable interference: Higher level than permissible and which has been agreed upon between two or more administrations.

Sharing Radio Frequencies:

Satellite systems, Cellular telephone, and wireless digital networks all employ microwave bands between 0.1 and 30 GHz.

Communication satellites unique – both to cause interference over a wide area , and to receive interference as well.


Source of interference: satellite network and terrestrial microwave link operating at same frequencies

Interference – Satellite network and Terrestrial:

Path 1 interference into satellite uplink: Protected by max. radiated power limit from the terrestrial microwave antenna

Path 2 Earth station interference into the terrestrial radio receiver – The radiation from the side lobes of the earth station antenna.

Path 3 Terrestrial radio interference into downlink receiver of the Earth station.

Path 4 Satellite interference into the terrestrial radio receiver.


Earth Terminal mis-pointing effects

Adjacent Satellite Interference:

• Antenna pointing error – a potentially significant contributor to interference and link degradation.

• When antenna mis-pointed link margin to the target satellite is degraded. The Gain in the direction of adjacent satellite can increase causing interference to those satellite signals.


Interfered with network Interfering with network

Up ASI Up ASI


Satellite user contribute to Adjacent Satellite Interference ( ASI ) and Cross-Polarization Interference ( XPI ) by:

• Excessive uplink power • Using too small of an antenna for the application, and / or • By failing to properly peak or and set polarization of their terminals

Downlink ASI: Ground receive antenna beam is large enough to receive significant signal levels from adjacent satellite

Uplink ASI: Adjacent satellites receive and rebroadcast strong signals from ground antennas which are too small / wide beam pattern, mis-pointed, or both.


Adjacent Satellite Interference in Mobile / VSAT environment


Rules for Satellite Operations:

• Protection of GEO FSS networks from interference by Non-GEO satellites.

• GEO satellites to have capability to maintain their nominal longitudinal positions to tolerance limits set by regulations for FSS, BSS and MSS.

• Side-lobe emissions ( off-axis emissions ) on earth stations are restricted to manage the overall uplink interference in the direction of GEO. This rule apply limit to the level of EIRP emitted by earth station as a function of off-axis angle.

Power Flux Density Limits:

• This provision limit the satellite power in bands where FSS is co-primary with fixed service – based on the power per unit bandwidth on the surface of Earth.

• The PFD defines how satellite might interfere with a terrestrial microwave station receiver.


International Frequency Coordination:

•This is a process that takes place with the cooperation of ITU – R for sharing the limited resources of spectrum and orbit among all nations and users.

•The Advanced Publication of Information ( API ) to ITU for a new communication satellite – a general description of the proposed satellite network.

•Review by RRB , information publication to other administrations for comments on aspects of the new satellite network interfering with their own or planned satellite networks.

•These processes for the final outcome to the API filing may involve change in the coverage pattern, power levels or specific bands or altering the orbit positions.


Additional Regulatory Approvals:

Apart from the international regulatory process relating to the radio spectrum and orbit resource country specific approvals where satellite communications services are to be provided.

• Operation of Uplink earth Stations:

Terrestrial coordination procedures are by the administration are for the earth station operator to ensure the operation of large earth stations are safe with respect to RF radiation harmful effect on the community an issue.

Earth stations should be away, requirement of shielding etc.

• Type Acceptance of Terminals:

Terminals required applications like VSAT networks and MSS services are numerous and hence type approval philosophy is used for the regulatory approval process.


On a given sample or a few of them the regulatory body can conduct tests as appropriate for approval. This test may include electromagnetic compatibility with other devices and service, safety, and orbital interference potential.

The tests conducted in govt. laboratory, third party business facility, by the manufacturer or by the network operator.

• Approval of Construction and Installations :

This is a the last step in the regulatory process of obtaining approval to construct, install and ultimately operate a satellite communication or network.

In some cases a company which obtains license for a particular frequency and location, based on general guidelines might require construction of facility under a totally different regulatory regime.

Also, after construction the developer needs approval to go on air. The difficult comes when the particular characteristic of the ground antenna or the uplink power might not pass this type of certification causing delays.


• Licensing and access practices – satellite systems and Earth terminals :

Licensing of satellite service is based on the primary requirement to manage spectrum resources so that harmful interference is prevented.

Ensure configuration of transmission parameters so that transmission do not exceed appropriate levels.

Proper installation and use of transmission equipment – requiring adequate training for equipment installation, installers and operators.

Conditions of Licensing:

• Efficient use of spectrum. • Avoidance of interference. • Avoidance of overloading when the same channel is assigned to more than one user. • Maintain dialogue between the administration and the end user of the radio

spectrum.


• Licensee – Consumer Relationship:

•Transparent and predictable regulatory regime safeguard industry development in the region – the satellite operates gains confidence in the industry and the market so that they are encouraged to plan long-range activities and research.

•Manage scarce resources – Regulators to allocate efficiently and in the public interest scarce resources such as radio spectrum. If the allocated spectrum not use, under-used or misused the license conditions allow regulators to reclaim the resources concerned.

•License issued by administrations for the segment of satellite system fall in two groups:

★Authorisation required for satellite service providers.

★Individual licensing for earth station facilities.

•Service Provider Licensing is for quality assurance to their customers.


Individual licensing vs “blanket licensing”:

•A single blanket license – VSATs configured based upon technical criteria – involving power levels, frequency etc – that mitigate the risk of interference.

•A single licensing can be issued covering a large number of VSAT terminals.

•The trend by individual regulators for blanket licensing based on their national interests.

VISION FOR SATCOM GROWTH


• Emergence of innovative technologies.

• Ability to provide broad coverage.

• Mobility applications on land, sea & air.

• Resilience to compete with terrestrial to take the service direct to the

consumer.

• Cost-effective broadcasting services.

• Instantaneous re-deployment of capacity, provides back-up / instant

communication infrastructure.

• Overall flexibility of communication configuration for applications and

reliability of service.


Training & Education for the future of Satcom Industry:

•Industry consolidation, downsizing off workforce in aerospace and satellite communications.

•Shortage of qualified personnel – areas related to spacecraft design & manufacture, ground segment manufacture, and terrestrial/wireless interface and standards.

•More focus on university level program and professional training groups supporting the field of satellite communications.

•In service training for employees in satcom institutions/industry.


There has been a continued focus towards deriving higher capacity from satellite platforms through technology innovation & adoption. Major gains have been achieved now.

This has resulted in reducing the equivalent cost for the satellite as well as ground systems for service applications.

Launch cost remains high and hence become the cost driver for the satellite systems.

Key success factors for the satellite industry will be in getting substantial reduction in the cost of putting LEO, MEO and GEO satellites.


SPECTRUM RESOURCE FOR SATCOM GROWTH :

• Ensuring spectrum availability is critical for the continuous innovations that are taking place in technological domain as well as in service applications.

• Regulatory certainty regarding allocated spectrum is critical to sustaining and meeting the growing demand for satellite services.

• Diverse satellite services – how we remain connected wherever we are, navigate on road, observe our food crops & natural resources through Earth Observations, keep our national borders secured, provide advance warning on natural calamities to save lives and manage situations.

• Ubiquity of satellite coverage and critical access it provides to consumers are challenges to other means of communications.

• The industry has made huge investments in deploying large satellite platforms, HTS with frequency re-use & spot beam technologies, satellite architecture development for small satellites exploiting the benefits of low orbits.


• Innovations are taking place as well plans being put on satellite based networking for Internet of Things( IoT ). This is expected to vastly expand mobile commerce.

•When these plans materialises shortly the industry will be poised for sharp growth creating job opportunities for millions.

•Commercial satellite capability also enhance military’s communication needs in the air, on land and at sea.

•In view of global threats many developing nations have also taken to development of space infrastructure for intelligence gathering, Surveillance & Reconnaissance.

•Even the vision for 5G roll out is an integrated network with satellite system, both Geo and Non-Geo playing a great part.

Thank You

itu satellite symposium - geneva, switzerland 28th to 30th ... · bus systems communication payload...

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