Satellites R.Seenuvasan ii mca. Satellites Overview History How Satellites Work Satellite...

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Satellites Satellites R.Seenuvasanii R.Seenuvasanii mca mca

Transcript of Satellites R.Seenuvasan ii mca. Satellites Overview History How Satellites Work Satellite...

Page 1: Satellites R.Seenuvasan ii mca. Satellites Overview  History  How Satellites Work  Satellite Frequency Bands and Antennas  Orbit Distance, Pros &

SatellitesSatellites

R.SeenuvasaR.Seenuvasanii mcanii mca

Page 2: Satellites R.Seenuvasan ii mca. Satellites Overview  History  How Satellites Work  Satellite Frequency Bands and Antennas  Orbit Distance, Pros &

Satellites OverviewSatellites Overview

History History How Satellites WorkHow Satellites Work Satellite Frequency Bands and AntennasSatellite Frequency Bands and Antennas Orbit Distance, Pros & Cons, ApplicationsOrbit Distance, Pros & Cons, Applications Types: Types: Low-Earth-Orbit (LEOs)Low-Earth-Orbit (LEOs)

Medium-Earth-Orbit (MEOs)Medium-Earth-Orbit (MEOs)Global Positioning System (GPS)Global Positioning System (GPS)Geostationary (GEOs)Geostationary (GEOs)

Satellite Tracking System (J-Tracker, J-Pass)Satellite Tracking System (J-Tracker, J-Pass)

Page 3: Satellites R.Seenuvasan ii mca. Satellites Overview  History  How Satellites Work  Satellite Frequency Bands and Antennas  Orbit Distance, Pros &

History of SatellitesHistory of Satellites The First Satellites

The theory of satellites was simple enough - shoot something out into space at the right speed and on the correct trajectory and it will stay up there, orbiting Earth, for years - if not forever.

If the orbit is the right distance in space the satellite will keep pace with the rotation of the Earth.

Pioneer Satellites (1957)

Early in October 1957 communications stations started picking up a regular beeping noise coming from space.

The signals were coming from Russia's Sputnik 1, the world's first man-made satellite.

It was January 1958, before a Jupiter rocket successfully launched Explorer 1, the first American satellite. 

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History of SatellitesHistory of Satellites NASA's Syncom programme (1963) GEOs

In July 1963 the Hughes Aircraft Corporation launched the experimental Syncom 2 for NASA, the world's first geosynchronous communications satellite. Its earlier sister, Syncom 1, had been blown up on launch earlier that year, but the second version was a huge success.

It carried the first live two-way satellite call between heads of state when President John F. Kennedy in Washington, D.C., telephoned Nigerian Prime Minister Abubaker Balewa in Africa.

The third Syncom satellite transmitted live television coverage of the 1964 Olympic Games from Tokyo.

 

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History of SatellitesHistory of Satellites Early Bird (1965)

The world's first commercial communications satellite was Early Bird, built for the Communications Satellite Corporation (COMSAT) by Hughes.

The satellite was launched on April 6, 1965, and placed in commercial service after moving into geosynchronous orbit 22,300 miles above the equator. That meant it was always on station to provide line of sight communications between Europe and North America.

Early Bird didn't have a battery - and worked only when its solar panels were exposed to the sun.

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History of SatellitesHistory of Satellites Later communications satellites

The launch of the Intelsat 3 satellites in 1969 created a global TV and speech communications network that spanned the Atlantic, Pacific and Indian Oceans.

The introduction of multiple-beam antennas in the 1980s brought new improvements in efficiency, as a satellite's power could now be concentrated on small regions of the Earth, making possible smaller-aperture (coverage area), lower-cost ground stations.

The Capacity (the number of simultaneous television and speech channels carried) grew as well.

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How Satellites WorkHow Satellites Work

1.1. A Earth Station sends A Earth Station sends message in GHz range. message in GHz range. (Uplink) (Uplink)

2.2. Satellite Receive and Satellite Receive and retransmit signals back. retransmit signals back. (Downlink)(Downlink)

3.3. Other Earth Stations Other Earth Stations receive message in receive message in useful strength area. useful strength area. (Footprint)(Footprint)

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Satellite Frequency Bands and Satellite Frequency Bands and Antennas (Dishes)Antennas (Dishes)

The size of Satellite Dishes (antennas) are The size of Satellite Dishes (antennas) are related to the transmission frequency.related to the transmission frequency.

There is a There is a inverse relationshipinverse relationship between between frequency and wavelength. frequency and wavelength.

As wavelength increases (and frequency As wavelength increases (and frequency decreases), larger antennas (satellite dishes) decreases), larger antennas (satellite dishes) are necessary to gather the signal.are necessary to gather the signal.

Page 9: Satellites R.Seenuvasan ii mca. Satellites Overview  History  How Satellites Work  Satellite Frequency Bands and Antennas  Orbit Distance, Pros &

Satellite Frequency Bands and Satellite Frequency Bands and Antennas (Dishes)Antennas (Dishes)

C-BandC-Band Ku-Band Ku-Band

Most commonly used bands: Most commonly used bands: C-band C-band (4 to 8 GHz) (4 to 8 GHz) , Ku-, Ku-band band (11 to 17 GHz) , and Ka-band (20 to 30 GHz ). (11 to 17 GHz) , and Ka-band (20 to 30 GHz ).

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Low-Earth-Orbit (LEO)Low-Earth-Orbit (LEO)

Altitude (375-1000 miles)Altitude (375-1000 miles) Revolution time: 90 min - 3 hours.Revolution time: 90 min - 3 hours. Advantages:Advantages:

Reduces transmission delay Reduces transmission delay Eliminates need for bulky Eliminates need for bulky

receiving equipment.receiving equipment. Disadvantages:Disadvantages:

Smaller coverage area.Smaller coverage area. Shorter life span (5-8 yrs.) Shorter life span (5-8 yrs.)

than GEOs (10 yrs).than GEOs (10 yrs). Subdivisions: Little, Big, and Mega Subdivisions: Little, Big, and Mega

(Super) LEOs.(Super) LEOs.

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Little LEOs ApplicationsLittle LEOs Applications

0.8 GHz range0.8 GHz range

Small, low-costSmall, low-cost

Vehicle tracking, Vehicle tracking, environmental monitoring environmental monitoring and two-way data and two-way data communication. Used for communication. Used for short, narrowband short, narrowband communications. communications.

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Big LEOs ApplicationsBig LEOs Applications 2 GHz or above range2 GHz or above range

Can offer global services, which Can offer global services, which can be subject to regulatory can be subject to regulatory requirements. requirements.

Used for technology devices such Used for technology devices such as high-speed, high-bandwidth as high-speed, high-bandwidth data communications, and video data communications, and video conferencing. They carry voice conferencing. They carry voice and high-speed data services. and high-speed data services. The main uses are data The main uses are data communications and real-time communications and real-time voice delivery to hand-held voice delivery to hand-held devices. devices.

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Mega (Super) LEOs ApplicationsMega (Super) LEOs Applications

20-30 GHz range20-30 GHz range

Mainly handles broadband Mainly handles broadband data. These systems are data. These systems are optimized for packet-switched optimized for packet-switched data rather than voice. They data rather than voice. They share the same advantages share the same advantages and drawbacks of other LEOs and drawbacks of other LEOs and are intended to operate and are intended to operate with inter-satellite links to with inter-satellite links to minimize transmission times minimize transmission times and avoid dropped signals. and avoid dropped signals.

Page 14: Satellites R.Seenuvasan ii mca. Satellites Overview  History  How Satellites Work  Satellite Frequency Bands and Antennas  Orbit Distance, Pros &

Hubble TelescopeHubble Telescope Classification: LEOClassification: LEO Orbit: 375 miles, 600 km.Orbit: 375 miles, 600 km. Revolution time: 100 min. Revolution time: 100 min. Speed: 17,000 miles/hrSpeed: 17,000 miles/hr Concerns:Concerns: Orbit decay from Orbit decay from

gravity and solar output. gravity and solar output. During “solar maximum”, the During “solar maximum”, the densities at all altitudes are densities at all altitudes are enhanced, and the drag effects enhanced, and the drag effects on satellites are much larger on satellites are much larger than during times of solar than during times of solar minimum. minimum.

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Space DebrisSpace Debris

According to the U.S. According to the U.S. Space Command Space Command (USSC), there are more (USSC), there are more than 8,000 objects larger than 8,000 objects larger than a softball now than a softball now circling the globe.circling the globe.

Of these, Of these, over 2000 are over 2000 are satellites (working and satellites (working and not).not).

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Middle-Earth-Orbiting (MEO)Middle-Earth-Orbiting (MEO)

MEOs orbits between the altitudes of 5,600 and 9,500 miles.

These orbits are primarily reserved for communications satellites that cover the North and South Pole.

Unlike the circular orbit of the geostationary satellites, MEOs are placed in an elliptical (oval-shaped) orbit.

Approximately a dozen medium Earth orbiting satellites are necessary to provide continuous global coverage 24 hours a day.

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GPS: What is it ?GPS: What is it ?

A constellation of 24 satellites

The Global Positioning System (GPS) is a worldwide radio-navigation system formed from a constellation of 24 satellites and their ground stations.

They are constantly moving, making two complete orbits in less than 24 hours.

These satellites are traveling at speeds of roughly 7,000 miles an hour.

GPS Satellites

Name: NAVSTAR Manufacturer: Rockwell International Altitude: 10,900 nautical miles Weight: 1900 lbs (in orbit)Size: 17 ft with solar panels

extended Orbital Period: 12 hours Orbital Plane: 55 degrees to

equatorial plane Planned Lifespan: 7.5 years Current constellation: 24 Block II production

satellites

The spacing of the satellites are arranged so that a minimum of five satellites are in view from every point on the globe.

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GPS: How it worksGPS: How it worksSatellites are reference points for locations on Earth

The whole idea behind GPS is to use satellites in space as reference points for locations here on

earth. GPS satellites use a "triangulate," system where the GPS receiver measures distance using the travel time of radio signals.

By using triangulation, we can accurately measure our distance and find out position from three satellites position anywhere on earth.

EX. THE BIG PICTURE

If a particular satellite is 11,000 miles above it. Then we know that it’s radius is 11,000 miles!

EX. THE BIG PICTURE

Basic calculations measuring distance

Velocity * Time = Distance

Velocity = speed of light (186,000 miles per second. )

Time = a lot of analysis and calculations!

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GPS: Problems in the SystemGPS: Problems in the System

Even though the satellites positions are constantly monitored, they can't be watched every second.

The atomic clocks they use are very, very precise but they're not perfect. Minute discrepancies can occur, and these translate into travel time measurement errors.

The signal may not actually get to the ground station receivers first. It may bounce off various objects before it gets to the receivers.

Satellites are precise but are not perfect.

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GPS: Who Uses GPS ?GPS: Who Uses GPS ?GPS has a variety of applications

Land: diverse uses; ex. surveying, recreational. Etc

Sea: navigation by recreational boaters, commercial fishermen, and professional mariners

Air: navigation by general aviation and commercial aircraft

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Geosynchronous-Earth-Orbit (GEO)Geosynchronous-Earth-Orbit (GEO) Orbit is sychroneous with Orbit is sychroneous with

the earths rotation.the earths rotation.

From the ground the From the ground the satellite appears fixed.satellite appears fixed.

Altitude is about 23,000 Altitude is about 23,000 miles.miles.

Coverage to 40% of Coverage to 40% of planet per satellite.planet per satellite.

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Basics of GEOsBasics of GEOs

Geostationary satellites are commonly used for Geostationary satellites are commonly used for communications and weather-observation.communications and weather-observation.

The typical service life expectancy of a geostationary The typical service life expectancy of a geostationary satellite is 10-15 years. satellite is 10-15 years.

Because geostationary satellites circle the earth at the Because geostationary satellites circle the earth at the equator, they are not able to provide coverage at the equator, they are not able to provide coverage at the Northernmost and Southernmost latitudes.Northernmost and Southernmost latitudes.

Page 23: Satellites R.Seenuvasan ii mca. Satellites Overview  History  How Satellites Work  Satellite Frequency Bands and Antennas  Orbit Distance, Pros &

GEOs and WeatherGEOs and Weather

The altitude is chosen so The altitude is chosen so that it takes the satellite that it takes the satellite 24 hours to orbit the Earth 24 hours to orbit the Earth once, which is also the once, which is also the rotation rate of the Earth.rotation rate of the Earth.

This produces the cloud This produces the cloud animations you see on animations you see on TV.TV.

Can take images Can take images approximately every approximately every minute.minute.

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Facts about GEOsFacts about GEOs Instruments on GEOs are designed to last 3-9 years.Instruments on GEOs are designed to last 3-9 years.

Measurements that are taken are in the form of electrical Measurements that are taken are in the form of electrical voltages that are digitized, and then transmitted to voltages that are digitized, and then transmitted to receiving stations on the ground. receiving stations on the ground.

Instruments usually have:Instruments usually have:

Small telescope or antenna.Small telescope or antenna.

A scanning mechanism.A scanning mechanism.

One or more detectors that detect either visible, One or more detectors that detect either visible, infrared, or microwave radiation. infrared, or microwave radiation.

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GEOs GEOs

Satellites are Satellites are positioned every 4-8 positioned every 4-8 degrees.degrees.

Aproximately 300 GEO Aproximately 300 GEO satellites are in orbit.satellites are in orbit.

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Pros and Cons of GEOsPros and Cons of GEOs Advantages:Advantages:

Weather images can Weather images can be displayed.be displayed.

Television broadcasts Television broadcasts are uninterrupted.are uninterrupted.

Used to track major Used to track major developments such as developments such as hurricanes 24 hours a hurricanes 24 hours a day.day.

Disadvantages:Disadvantages:

It takes longer for the It takes longer for the signal to get to earth signal to get to earth and back to satellite.and back to satellite.

Increased difficulty of Increased difficulty of telephone telephone conversations.conversations.

GEOs are not GEOs are not positioned in the positioned in the farthest northern and farthest northern and southern orbits.southern orbits.

Page 27: Satellites R.Seenuvasan ii mca. Satellites Overview  History  How Satellites Work  Satellite Frequency Bands and Antennas  Orbit Distance, Pros &

Provides images of nearly Provides images of nearly one-third of the Earth's one-third of the Earth's surface every 23 minutes surface every 23 minutes with 4 km resolution.with 4 km resolution.

While the United States While the United States maintains and operates its maintains and operates its GEOs, the European GEOs, the European community is served by its community is served by its European Space Agency European Space Agency (ESA) Meteosat satellite, (ESA) Meteosat satellite, and Japan with its GMS and Japan with its GMS satellite. satellite.

GEOsGEOs

Page 28: Satellites R.Seenuvasan ii mca. Satellites Overview  History  How Satellites Work  Satellite Frequency Bands and Antennas  Orbit Distance, Pros &

Satellite Tracking SystemSatellite Tracking System

NASA J-Tracker

NASA J-Pass

Page 29: Satellites R.Seenuvasan ii mca. Satellites Overview  History  How Satellites Work  Satellite Frequency Bands and Antennas  Orbit Distance, Pros &

ConclusionConclusion

HistoryHistory How Satellites WorkHow Satellites Work Satellite Frequency Bands and AntennasSatellite Frequency Bands and Antennas Orbit Distance, Pros & Cons, ApplicationsOrbit Distance, Pros & Cons, Applications Types: Types: Low-Earth-Orbit (LEOs)Low-Earth-Orbit (LEOs)

Medium-Earth-Orbit (MEOs)Medium-Earth-Orbit (MEOs)Global Positioning System (GPS)Global Positioning System (GPS)Geostationary (GEOs)Geostationary (GEOs)

Satellite Tracking System (J-Tracker, J-Pass)Satellite Tracking System (J-Tracker, J-Pass)

Page 30: Satellites R.Seenuvasan ii mca. Satellites Overview  History  How Satellites Work  Satellite Frequency Bands and Antennas  Orbit Distance, Pros &

Questions ???Questions ???

Page 31: Satellites R.Seenuvasan ii mca. Satellites Overview  History  How Satellites Work  Satellite Frequency Bands and Antennas  Orbit Distance, Pros &

Arts By:Arts By:

R.Seenuvasan.MBA,M.Phil

II MCA ‘B’,Tiruvannamalai.E-Mail ID: [email protected]