earth sci chap 08C

8/8/2019 earth sci chap 08C

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TWO CATEGORIES:

1. Satellites

2. Probes


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A satellit

e is

any object

that orbitsor revolves

aroundanother

object.

What is a satellite?


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To launch and keep a satellite in

orbit you need:1. POWERFUL ROCKET

2. GUIDANCE SYSTEM


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Object

mustreach

escapevelocity

of25,000

mph.


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POWERFUL

ROCKETS

First ICBMs were

used

Developed more

powerful rocketsby adding

stages.


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Three-Stage

Rocket usedto launch

weather

satellite.

RL-10 Rocket

Engine made at Pratt

& Whitney,

Florida


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2. GUIDANCE SYSTEM

Guidance system is so complex itmust be controlled by computer.

Satellite must beat exactly the

right altitude andspeed to

maintain orbit.


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Early

computerswere

HUGE and

less

powerful

than thechip inside

a Furby!

ILLIAC - 1962


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A satellite is actually being pulled by

earths gravity all the time.

In other words, it is always falling.

It musttravel fast

enough to

miss theearth as it

falls.


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The speed for a

proper orbitdepends on the

distance of the

satellite from theearth.


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The lower the orbit

the stronger the pull

of gravity

greater

velocity is

necessaryto maintain

orbit.


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The higher the

orbit the weaker the pull of gravity

less velocity isnecessary to

maintain orbit.


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GRAVITY

VELOCITY

Must be balanced

to stay in orbit.


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parallel to

the equator

124-1240

miles abovethe earths

surface


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Satellites in LEO circle the earth

about once every 90 minutes.Early weather

satellites were

placed in LEO.

Now, some

communicationsatellites are in

LEO.


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More than a

million objects

are in LEO most smaller

than a tennis

ball.


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passes over

north and southpoles

altitudesrange from

435500 miles


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Used forweather

satellites,mapping and

oceanography.


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Satellite passes over a given point at

the same time every day. Used for

environmental monitoring.

Some PEOs

are sunsynchronous.


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GEOs are

22,000

miles over

the equator

and have a24 hour

orbit.


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GEOs travel about 17,000 mph

making one orbit every 24 hours.

In geosynchronous orbit, thesatellite remains "parked" over a

certain spot on the earth.


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The term

geostationaryrefers to a

satellite thatstays directly

over the

same spot on

earth.

North Pole


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Explorer 1 (1958) was the firstUS scientific satellite. Confirmed

existence of magnetosphere.


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Transmitted

data aboutthe shape

of theearth.

Vanguard I(1958)


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UARS 1991

Upper

Atmosphere

ResearchSatellite -

study ofozone layer.


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LANDSAT 1 - 7

Longest

runningsatellite

program

1968 to

present.


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Looks

outwardfrom earth

orbit into

the

universe.


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1. Communications

Some satellites

act as relaystations to

bouncemessages all

over the world.


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EchoStaris the

satellite that

carries TV

broadcasts formost of North

America.

The area covered by a

communication satellite is calledits footprint.


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Because communication

satellites are geostationarywe can

point our

receiver in

one

direction allthe time.


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2. GPS Satellites

Global Positioning System24 Satellites

in 6 different

orbital planes

circling the

earth twiceeach 24

hours.


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GPS was designed for and is

controlled by the U.S. Military

NAVSTAR


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Paths of GPS Satellites

in 24 Hour Period


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Today, handheld or console

models are commonand inexpensive.


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3.WEATHER

SAT

ELLIT

ESSome are

placed in apolar orbit

circling theearth twice

every 24 hours.


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First US

weathersatellite

launched in1960 by

NOAA wasnamed

TIROS I.


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Others are placed in

geosynchronous orbits.


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Russia, Europe, Japan, India,

China,& US share information.


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Not placed into orbits

1.Sounding RocketsUsed to collect information

about the upper atmosphere ofearth.


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2. Lunar Probes

USSR program was called LUNA


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USA LUNAR PROBES

Ranger

Surveyor


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PROBES TO VENUS

USA - Magellan

USSR - Venera


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EARLY PROBES TO MARS

USSR Mars 1

USA - Viking

C S


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CURRENT USA

MARS ROVERS


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PROBES TOOUTER PLANETS

USAVoyager II

All four gas giants 1979-89

PROBES TO HALLEYS COMET


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PROBES TO HALLEYS COMET

1986

European - Giotto

Japan - Sakigake


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Heliocentric

orbit itfollows the

earths orbitaround the

sun.


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SOHO Sun and Heliographic

Observer is in a halo orbitbetween the sun and the earth.

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earth sci chap 08C