balloon satellites

8/2/2019 Balloon Satellites

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BALLOON SATELLITE

ABSTRACT

The main theme involved in developing this paper is to provide a clear understanding of

satellites, purpose of satellites and their types, need of satellite communications in day-to-daylife. There are two types of communication satellites low earth orbit communication satellites

(LEO) and geosynchronous communication satellites. Under LEO communication satellites there

comes Echo and Telstar communication satellites, their advantages and disadvantages and

advancements of geosynchronous communication satellites compared to LEOs has been

discussed.

A brief idea on basic communication satellite components has been given.

In the years to come, there are many projected plans in the area of satellites. This will be

a benefit to the United States and the rest of the world. Some of these advances are in satellite

photography, communications, and weather technology. Some of the future advances are in thedistant future, while others are being developed right now. The usage of satellites today, new

satellite communications, the latest in satellite gear, direct broadcast satellite T.V, satellite

advances in television, future global satellite networks. We have also presented some of the

launch vehicles used to send satellites into space.


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WHAT IS A SATELLITE

A satellite is something that goes around and around a larger something, like the earth or

another planet. Some satellites are natural, like the moon, which is a natural satellite of the earth.

Other satellites are made by scientists and technologists to go around the earth and do certain

jobs. Can We Imitate Nature (Artificial Satellites) Very soon after Newton's laws werepublished, people realized that in principle it should be possible to launch an artificial satellite

which would orbit the earth just as the moon does. A simple calculation, however, using the

equations which we developed above, will show that an artificial satellite, orbiting near the

surface of the earth (R = 4000 miles) will have a period of approximately 90 minutes. This

corresponds to a sideways velocity (needed in order to "miss" the earth as it falls), of

approximately 17,000 miles/hour (that's about 5 miles/second).


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Figure: Aryabhatta (First Indian Satellite)


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TYPES OF SATELLITES

Boeing 376, built by Boeing Satellite Systems. The Boeing 376 is used mostly for

broadcast television and cable television. Boeing 601 which is also built by Boeing SatelliteSystems. The Boeing 601 is used for many purposes, including direct broadcast TV, such as

DIRECTV. Direct broadcast TV is a system for receiving television using a very small satellitedish. The television signal is relayed by a Boeing 601 satellite. The Boeing 601 also relays

telephone, fax, and computer communications. The most powerful commercial satellite in the

world is the Boeing 702. Designed and built by Boeing Satellite Systems, this giant has a

wingspan of nearly 157 feet more than a Boeing757jetplane.

Why Satellites for Communication

By the end of World War II, the world had had a taste of "global communications."

Edward R. Murrow's radio broadcasts from London had electrified American listeners. We had,

of course, been able to do transatlantic telephone calls and telegraphs via underwater cables foralmost 50 years. At exactly this time, however, a new phenomenon was born. The first television

programs were being broadcast, but the greater amount of information required transmitting

television pictures required that they operate at much higher frequencies than radio stations.

Television signals however required much higher frequencies because they were transmitting

much more information - namely the picture. Both radio and television frequency signals can

propagate directly from transmitter to receiver. This is a very dependable signal, but it is more or

less limited to line of sight communication. The mode of propagation employed for long distance

(1000s of miles) radio communication was a signal which traveled by bouncing off the charged

layers of the atmosphere (ionosphere) and returning to earth. The higher frequency television

signals did not bounce off the ionosphere and as a result disappeared into space in a relativelyshort distance. This is shown in the diagram below. Radio Signals Reflect Off the Ionosphere;

TV Signals do not in addition, of course, the appetite for transatlantic radio and telephone was

increasing rapidly. Adding this increase to the demands of the new television medium, existing

communications capabilities were simply not able to handle all of the requirements. By the

late1950s the newly developed artificial satellites seemed to offer the potential for satisfying

many of these needs. Low Earth-Orbiting Communications Satellites In 1960, communications

satellite ever conceived was launched. It was called Echo, because it consisted only of a large

(100 feet in diameter) aluminized plastic balloon. Radio and TV signals transmitted to the

satellite would be reflected back to earth and could be received by any station within view of the

satellite.

Echo Satellite

Unfortunately, in its low earth orbit, the Echo satellite circled the earth every ninety

minutes. This meant that although virtually everybody on earth would eventually see it, no one

person, ever saw it for more than 10 minutes or so out of every 90 minute orbit. In 1958, the

Score satellite had been put into orbit. It carried a tape recorder which would record messages as


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it passed over an originating station and then rebroadcast them as it passed over the destination.

Once more, however, it appeared only briefly every 90 minutes - a serious impediment to real

communications. In 1962, NASA launched the Telstar satellite for AT&T.

Figure: ECHO communication satellite
http://www.google.co.in/imgres?imgurl=http://www.nasa.gov/centers/langley/images/content/69831main_LaRC_History_fig9.GIF&imgrefurl=http://www.nasa.gov/centers/langley/news/factsheets/LaRC_History.html&usg=__XuEf0MyZYxTJ38NtJbt299oefps=&h=305&w=306&sz=88&hl=en&start=1&zoom=1&tbnid=SWbLY0hzyPYDgM:&tbnh=117&tbnw=117&ei=6lJJTdqJFIrJrAfuhviYDg&prev=/images?q=echo+communication+satellites&hl=en&sa=N&gbv=2&tbs=isch:1&itbs=1


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Telstar Communications Satellite

Telstar's orbit was such that it could "see" Europe" and the US simultaneously during one

part of its orbit. During another part of its orbit it could see both Japan and the U.S. As a result, it

provided real- time communications between the United States and those two areas - for minutes

out of every hour Geosynchronous Communications Satellites: The solution to the problem ofavailability, of course, lay in the use of the geosynchronous orbit. In 1963, the necessary rocket

booster power was available for the first time and the first geosynchronous satellite, Syncom2,

was launched by NASA. For those who could "see" it, the satellite was available 100% of the

time, 24hours a day. The satellite could view approximately 42% of the earth. For those outside

of that viewing area, of course, the satellite was NEVER available.


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Figure: Telstar communication satellite
http://www.google.co.in/imgres?imgurl=http://www.edwardsamuels.com/illustratedstory/chapter%205/telstar.jpg&imgrefurl=http://www.edwardsamuels.com/illustratedstory/isc5.htm&usg=__nxGfx7HE_tfGvm9JrVd_knNox28=&h=452&w=450&sz=28&hl=en&start=5&zoom=1&tbnid=Ah1F183Qaw3gFM:&tbnh=127&tbnw=126&ei=WFFJTau3NczrrQfz0bWwDg&prev=/images?q=Telstar+communication+satellites&hl=en&sa=N&gbv=2&tbs=isch:1&itbs=1


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Syncom2 Communications Satellite

However, a system of three such satellites, with the ability to relay messages from one to

the other could interconnect virtually all of the earth except the Polar Regions. The one

disadvantage(for some purposes) of the geosynchronous orbit is that the time to transmit a signal

from earth to the satellite and back is approximately of a second - the time required totravel 22,000 miles up and 22,000 miles back down at the speed of light. For telephone

conversations, this delay can sometimes be annoying. For data transmission and most other uses

it is not significant. In any event, once Syncom2 had demonstrated the technology necessary to

launch a geosynchronous satellite, a virtual explosion of such satellites followed. Today, there

are approximately 150 communications satellites in orbit, with over 100 in geosynchronous orbit.

One of the biggest sponsors of satellite development was Intelsat, an internationally-owned

corporation which has launched 8 different series of satellites (4 or 5 of each series) over a

period of more than 30 years. Spreading their satellites around the globe and making provision to

relay from one satellite to another, they made it possible to transmit 1000s of phone calls

between almost any two points on the earth. It was also possible for the first time,

due to the large capacity of the satellites, to transmit live television pictures between virtually

any two points on earth. By 1964 (if you could stay up late enough), you could for the first time

watch the Olympic Games live from Tokyo. A few years later of course you could watch the

Vietnam War live on the evening news. Basic Communications Satellite Components every

communications satellite in its simplest form (whether low earth or geosynchronous) involves

the transmission of information from an originating ground station to the satellite (the uplink),

followed by a retransmission of the information from the satellite back to the ground (the

downlink). The downlink may either be to a select number of ground stations or it may be

broadcast to everyone in a large area. Hence the satellite must have a receiver and a receiveantenna, a transmitter and a transmit antenna, some method for connecting the uplink to the

downlink for retransmission, and prime electrical power to run all of the electronics. The exact

nature of these components will differ, depending on the orbit and the system architecture, but

every communications satellite must have these basic components. This is illustrated in the

following drawing. Basic Components of a Communications Satellite Link.


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Figure: Syncom2 satellite
http://www.google.co.in/imgres?imgurl=http://2.bp.blogspot.com/_DSjqgiaJvag/RqosCV04Z6I/AAAAAAAAATQ/nHiAB_tTtFA/s320/Syncom.jpg&imgrefurl=http://www.tucmuc.org/2007_07_01_archive.html&usg=__d_5HlMKbNW8aRJiFIXSKOOOGGSI=&h=278&w=250&sz=19&hl=en&start=24&zoom=1&tbnid=hDOqpjvc-SbtbM:&tbnh=114&tbnw=103&ei=klVJTZDZNMPLrQfat_maDg&prev=/images?q=syncom+2+communication+satellites&start=20&hl=en&sa=N&gbv=2&tbs=isch:1&itbs=1


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DEVELOPMENTINSATELLITECOMMUNICATION

Some of the first communications satellites were designed to operate in a passive mode.

Instead of actively transmitting radio signals, they served merely to reflect signals that were beamed

up to them by transmitting stations on the ground. Signals were reflected in all directions, so

receiving stations around the world could pick them up. Echo 1, launched by the United States in

1960, consisted of an aluminized plastic balloon 30 m (100 ft) in diameter. Launched in 1964, Echo 2

was 41 m (135 ft) in diameter. The capacity of such systems was severely limited by the need for

powerful transmitters and large ground antennas. Score, launched by the United States in 1958, was

the first active communications satellite. It was equipped with a tape recorder that stored messages

received while passing over a transmitting ground station. These messages were retransmitted when

the satellite passed over a receiving station. Telstar 1, launched by American Telephone and

Telegraph Company in 1962, provided direct television transmission between the United States,

Europe, and Japan and could also relay several hundred-voice channels. Launched into an elliptical

orbit inclined 45 to the equatorial plane, Telstar could only relay signals between two ground

stations for a short period during each revolution, when both stations were in its line of sight.Hundreds of active communications satellites are now in orbit. They receive signals from one ground

station, amplify them, and then retransmit them at a different frequency to another station. Satellites

use ranges of different frequencies, measured in hertz (Hz) or cycles per second, for receiving and

transmitting signals. Many satellites use a band of frequencies of about 6 billion hertz, or 6 gigahertz

(GHz) for upward, or uplink, transmission and 4 GHZ for downward, or downlink, transmission.

Another band at 14 GHZ (uplink) and 11 or 12 GHZ (downlink) is also much in use, mostly with

fixed (non mobile) ground stations. A band at about 1.5 GHZ (for both uplink and downlink) is used

with small, mobile ground stations (ships, land vehicles, and aircraft). Solar energy cells mounted on

large panels attached to the satellite provide power for reception and transmission.

GEOSYNCHRONOUS ORBIT

A satellite in a geosynchronous orbit follows a circular orbit over the equator at an altitude of

35,800 km (22,300 mi), completing one orbit every 24 hours, in the time that it takes the earth to

rotate once. Moving in the same direction as the earth's rotation, the satellite remains in a fixed

position over a point on the equator, thereby providing uninterrupted contact between ground stations

in its line of sight. The first communications satellite to be placed in this type of orbit was Syncom2,

launched by the National Aeronautics and Space Administration (NASA) in 1963. Most

communications satellites that followed were also placed in geosynchronous orbit

RECENT TECHNICAL ADVANCES

Communications satellite systems have entered a period of transition from point-to-point

high-capacity trunk communications between large, costly ground terminals to multipoint-to-

multipoint communications between small, low-cost stations. The development of multiple access

methods has both hastened and facilitated this transition. With TDMA, each ground station is

assigned a time slot on the same channel for use in transmitting its communications; all other stations


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monitor these slots and select the communications directed to them. By amplifying a single carrier

frequency in each satellite repeater, TDMA ensures the most efficient use of the satellite's onboard

power supply. A technique called frequency reuse allows satellites to communicate with a number of

ground stations using the same frequency by transmitting in narrow beams pointed toward each of the

stations. Beam widths can be adjusted to cover areas as large as the entire United States or as small as

a state like Maryland. Two stations far enough apart can receive different messages transmitted on the

same frequency. Satellite antennas have been designed to transmit several beams in different

directions, using the same reflector. A method for interconnecting many ground stations spread over

great distances was demonstrated in 1993 with the launch of NASA's ACTS (Advanced

Communications Technology Satellite). The satellite uses what is known as the hopping spot beam

technique to combine the advantages of frequency reuse, spot beams, and TDMA. By concentrating

the energy of the satellite's transmitted signal, ACTS can use ground stations that have smaller

antennas and reduced power requirements. The concept of multiple spot beam communications was

successfully demonstrated in 1991 with the launch of Aalst, developed by the Italian Research

Council. With six spot beams operating at 30 GHZ (uplink) and 20 GHZ (downlink), the satelliteinterconnects TDMA transmissions between ground stations in all the major economic centers of

Italy. It does this by demodulating uplink signals, routing them between up- and downlink beams, and

combining and re modulating them for downlink transmission. Laser beams can also be used to

transmit signals between a satellite and the earth, but the rate of transmission is limited because of

absorption and scattering by the atmosphere. Lasers operating in the blue-green wavelength, which

penetrates water, have been used for communication between satellites and submarines. The latest

development in satellites is the use of networks of small satellites in low earth orbit (2,000 km (1,200

mi) or less) to provide global telephone communication. The Iridium system uses 66 satellites in low

earth orbit, while other groups have or are developing similar systems. Special telephones that

communicate with these satellites allow users to access the regular telephone network and place calls

from anywhere on the globe. Anticipated customers of these systems include international business

travelers and people living or working in remote areas.


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BALLOON SATELLITE

Figure: Balloon satellite


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Model of a Balloon SatelliteA balloon satellite (Also occasionally referred to as a "Balloon", which is a trademarked

name owned by Gilmore Schjeldahl's G.T. Schjeldahl Company) is a satellite that is inflated with gas

after it has been put into orbit.

The Pythagorean Theorem allows us to calculate easily how far a satellite is visible at such a

great height. It can be determined that a satellite in a 1,500-kilometer (930 mi) orbit rises and sets

when the horizontal distance is 4,600 kilometers (2,900 mi). However, the atmosphere causes this

figure to vary slightly. Thus if two radio stations are 9,000 kilometers (5,600 mi) apart and the

satellite's orbit goes between them, they may be able to receive each other's reflected radio signals if

the signals are strong enough.

Optical visibility is, however, lower than that of radio waves, because the satellite must be

illuminated by the sun the observer needs a dark sky (that is, he must be in the Earth's own shadow on

the planet's twilight or night side) the brightness of a sphere depends on the angle between theincident light and the observer (see phases of the moon) the brightness of a sphere is much reduced as

it approaches the horizon, as atmospheric extinction swallows up as much as 90% of the light.

Despite this there is no problem observing a flying body such as Echo 1 for precise purposes

of satellite geodesy, down to a 20 elevation, which corresponds to a distance of 2,900 kilometers

(1,800 mi). In theory this means that distances of up to 5,000 kilometers (3,100 mi) between

measuring points can be "bridged", and in practice this can be accomplished at up to 3,0004,000kilometers (1,9002,500 mi).For visual and photographic observation of bright satellites andballoons, and regarding their geodetic use, see Echo 1 andPagesfor further information.

Other balloon satellites

For special testing purposes two or three satellites of the Explorer series were constructed as

balloons (possibly Explorer 19 and 38).Echo 1 was an acknowledged success of radio engineering,

but the passive principle of telecommunications (reflection of radio waves on the balloon's surface)

was soon replaced by active systems. Telstar 1 (1962) and Early Bird (1965) were able to transmit

several hundred audio channels simultaneously in addition to a television program exchanged

between continents.

Satellite geodesy with Echo 1 and 2 was able to fulfill all expectations not only for the planned

23 years, but for nearly 10 years. For this reason NASA soon planned the launch of the even larger40-meter (130 ft) balloonPages. The name is from "passive geodesic satellite", and sounds similar to"Geo", a successful active electronic satellite from 1965.1965-1975: Success with flashing light

beacons Bright balloon satellites are well visible and were measurable on fine-grained (less sensitive)

photographic plates, even at the beginning of space travel, but there were problems with the exact

chronometry of a satellite's track. In those days it could only be determined within a few
http://en.wikipedia.org/wiki/Gilmore_Schjeldahlhttp://en.wikipedia.org/wiki/Satellitehttp://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Orbithttp://en.wikipedia.org/wiki/Pythagorean_theoremhttp://en.wikipedia.org/wiki/Phases_of_the_moonhttp://en.wikipedia.org/wiki/Extinction_(astronomy)http://en.wikipedia.org/wiki/Echo_1http://en.wikipedia.org/wiki/Pageoshttp://en.wikipedia.org/wiki/Pageoshttp://en.wikipedia.org/wiki/Pageoshttp://en.wikipedia.org/wiki/Explorer_programhttp://en.wikipedia.org/wiki/Echo_1http://en.wikipedia.org/wiki/Telstar_1http://en.wikipedia.org/wiki/Early_Birdhttp://en.wikipedia.org/wiki/NASAhttp://en.wikipedia.org/wiki/Pageoshttp://en.wikipedia.org/wiki/Pageoshttp://en.wikipedia.org/wiki/Pageoshttp://en.wikipedia.org/wiki/Pageoshttp://en.wikipedia.org/wiki/NASAhttp://en.wikipedia.org/wiki/Early_Birdhttp://en.wikipedia.org/wiki/Telstar_1http://en.wikipedia.org/wiki/Echo_1http://en.wikipedia.org/wiki/Explorer_programhttp://en.wikipedia.org/wiki/Pageoshttp://en.wikipedia.org/wiki/Echo_1http://en.wikipedia.org/wiki/Extinction_(astronomy)http://en.wikipedia.org/wiki/Phases_of_the_moonhttp://en.wikipedia.org/wiki/Pythagorean_theoremhttp://en.wikipedia.org/wiki/Orbithttp://en.wikipedia.org/wiki/Gashttp://en.wikipedia.org/wiki/Satellitehttp://en.wikipedia.org/wiki/Gilmore_Schjeldahl


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milliseconds.

Since satellites circle the earth at about 78 kilometers per second (4.35.0 mi/s), a time error of0.002 second translates into a deviation of about 15 meters (49 ft). In order to meet a new goal of

measuring the tracking stations precisely within a couple of years, a method of flashing light beacons

was adopted around 1960.To build a three-dimensional measuring network, geodesy needs exactlydefined target points, more so than a precise time. This precision is easily reached by having two

tracking stations record the same series of flashes from one satellite. Flash technology was already

mature in 1965 when the small electronic satellite Geo (later named Geos1was launched; along with

its companion Geos2, it brought about a remarkable increase in precision.

From about 1975 on, almost all optical measurement methods lost their importance, as they

were overtaken by speedy progress in electronic distance measurement. Only newly developed

methods of observation using CCD and the highly precise star positions of the astrometry satellite

Hip arcos made further improvement possible in the measurement of distance.
http://en.wikipedia.org/w/index.php?title=Geos_1&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Geos_2&action=edit&redlink=1http://en.wikipedia.org/wiki/Charge-coupled_devicehttp://en.wikipedia.org/wiki/Astrometryhttp://en.wikipedia.org/wiki/Hipparcoshttp://en.wikipedia.org/wiki/Hipparcoshttp://en.wikipedia.org/wiki/Astrometryhttp://en.wikipedia.org/wiki/Charge-coupled_devicehttp://en.wikipedia.org/w/index.php?title=Geos_2&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Geos_1&action=edit&redlink=1


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CONCLUSION

Looking at the rate of advancement in satellite communication one would foresee the use of satellites

in every field where communication is required such as relaying television and radio signals. Special

telephones that communicate with these satellites allow users to access the regular telephone network

and place calls from anywhere on the globe. Additional satellites are scheduled for launch that will

enable new communication systems to be used around the world. Advances in the new Satellite

Technology have made people no more than a phone call away. Satellites can send messages from

one continent to another and also from one planet to another. Satellite technology brings us the

weather, cellular phones, wireless cable, and direct broadcast television. Satellite communication

companies are expecting these services to be offered all over the world in the very near future.


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http://www.connected-earth.com .

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