Satellites Why do objects move in a circle? - PowerPoint Presentation

Slide1

SatellitesSlide2

Why do objects move in a circle?

http://www.youtube.com/watch?v=h3fH84fE0eo&feature=relatedSlide3

Why doesn’t the moon fall down?

It does.

http://www.youtube.com/watch?v=RsFf9gl6lL8&feature=relatedSlide4

What is a satellite?

Technically, anything that is in orbit around Earth is technically a satellite, but the term "satellite" is typically used to describe a useful object placed in orbit purposely to perform some specific mission or task. We commonly hear about weather satellites, communication satellites and scientific satellites.Slide5

Whose Satellite Was the First to Orbit Earth?

The Soviet Sputnik satellite was the first to orbit Earth, launched on October 4, 1957.

It weighed 184 pounds and was 23” in diameter.Slide6

What happened to it?

After 92 days, gravity took over and Sputnik burned in Earth's atmosphere. Thirty days after the Sputnik launch, the dog Laika orbited in a half-ton Sputnik satellite with an air supply for the dog. It burned in the atmosphere in April 1958. Slide7

Progress since then…

ISS Video

http://www.theblaze.com/stories/one-of-the-best-time-lapsed-videos-of-earth-from-space-yet/Slide8

How Do You Put Something In Orbit?

If the Earth were flat like some people used to believe, no matter how fast you threw something out horizontally, it would hit the ground. The faster you threw it, the farther away along the ground it would hit. Plus - all of the balls will hit the ground at the same time.

http://www.ux1.eiu.edu/~cfadd/1150/05UCMGrav/Sat.html

Slide9

But the Earth is not

flat!

As something falls "straight" toward the center of the Earth, it has to curve around with the Earth. Slide10
Slide11

Throw an object fast enough that its “fall” matches the curvature of the Earth.

The Earth’s curvature is such that it “drops” about 5 meters every 8,000 m.

So what speed would it have to go to orbit the Earth at the surface?

8 km/s!Slide12

The

only

force on a satellite is the

force of gravity.

That’s the force pulling it in to the center.Slide13

Launch

Space shuttle Atlantis final launch: NASA video of last take-off

http://www.youtube.com/watch?v=2EFuLap5Pgg

Mars exploration rover Slide14

Let’s use equations to check how fast an object near the Earth’s surface is orbiting?

Fg = Fc

Fg = mv

2

/ r

m g = m v

2

/ r

g = v

2

/ r

v

2

= g r

If r = 6.38 x 10

6

m, what is v?Slide15

The orbital velocity is

v

2

= ( 9.8 m/s ) ( 6.38 x 10

6

m ) = 6.25 x 10

7

(m/s)

2

v = 7.9 x 10

3

m/s

That’s 17 000 mi/h!Slide16

What about the

period

? How long does it take to make one orbit?

v = d / T

T = d / v

T = 2

π

r / v

T = 2 ( 3.14 ) ( 6.38 x 10

6

m ) / ( 7.9 x 10

3

m/s )

T = 5074 s [ 1 min/60 s ] = 84 minSlide17

The

Space Shuttle

is an excellent example of a satellite in a

low-Earth orbit

.

The Space Shuttle orbits about 100 km to 200 km above Earth's surface. Earth's radius is about 6 000 km so this is an increase of only about 2% or 3%. That means the force of gravity is only about 4% to 6% less than

at Earth's surface

.Slide18

Low Earth Orbit

Imagine yourself in an elevator when the cable breaks! The only force on you is gravity! Slide19

The Physical Aspect

Bodily fluids are redistributed, with less in the lower extremities, and more in the upper body. Without the pulls of normal gravity, blood doesn't flow downhill, but pools in the extremities including the face, hands and feet, causing a puffy appearance. And without that downward pressure, height increases. Body mass often decreases with a loss of muscular tissue from nitrogen depletion; the veins and arteries of the legs become weaker, anemia occurs, accompanied by a reduction in blood count. Astronauts report an overall feeling of weakness and loss of balance upon return to Earth, though recovery is nearly complete after a week.Slide20

Types of Satellites

http://www.windows.ucar.edu/spaceweather/effects1.html

Slide21

Types of Orbits

Polar Orbits

This orbit allows the satellite to observe the entire Earth's surface as it rotates beneath it. Most desired orbits are between 700 and 800 km altitude with orbit periods between 98 and 102 minutes.

Slide22

Uses of Polar Orbiting Satellites

This orbit provides global daily coverage of the Earth with higher resolution than geostationary orbit. Even though satellites do not pass directly over the poles they come close enough that their instruments can scan over the polar region, providing truly global coverage. Slide23

Geosynchronous Satellites Orbit

around the Earth at the same speed that the Earth rotates.

What’s its period?

24 hours

If they stay over the same place, they are called geostationary. Where do they orbit?

Over the equator. Because of this, it appears to remain over a fixed point on the Earth's surface.

Slide24

Uses of Geosynchronous Satellites

Perfect for communications satellites because always in view of the ground station providing continuous TV and telecommunications services to customers. Also ideal for making uninterrupted observations of the weather or environmental conditions in a given area. Slide25

Definitions:

Geosynchronous- same period as Earth

Geostationary – orbits over the same location on Earth

Asynchronous – not once a day, like the space station.Slide26

What is the orbital radius of a geosynchronous satellite?

Fg = Fc

Fg = mv

2

/ r

GM

E

M

S

/r

2

= M

S

v

2

/ r

GM

E

/r

2

= (2

π

r/T)

2

/ r

GM

E

/r

2

=

(2

π

r)

2

/ T

2

r

GM

E

/r

2

= 4

π

2

r

2

/ T

2

rSlide27

GM

E

/r

2

= 4

π

2

r

2

/ T

2

r

Move r

2

to top

GM

E

= 4

π

2

r

2

r

2

/ T

2

r

GM

E

= 4

π

2

r

3

/ T

2

Solving for r:

r

3

= GM

E

T

2

/ 4

π

2

This means that for a fixed period – like 24 hr – there is only ONE radius that will work!!

Slide28

r

3

= (6.67 x 10

-11

)(6 x 10

24

kg)(86,400s)

2

/4

π

2

r

3

= 7.54 x 10

22

m

3

r = 4.2 x 10

7

m

If we subtract off the radius of the Earth, which is 6.38 x 10

6

m (or 6380 km), then

The orbital radius is 36,000 km above earth, or

6 r

E

(

6 times Earth’s radius

). Slide29

What’s the velocity of a geosynchronous satellite?

Fg = Fc

Fg = mv

2

/ r

GM

E

M

S

/r

2

= M

S

v

2

/ r

GM

E

/r

2

= v

2

/ r

GM

E

/r = v

2

v= square root of (GM

E

/r)

V

= 3070 m/s Slide30

So all the geosynchronous satellites orbit at this radius!Slide31

Geosynchronous orbits are 1/10 the distance to the moon!Slide32

Space Junk at Tipping Point

http://www.youtube.com/watch?v=2gTkoFJ2yIQ&feature=fvsr

Debris – green dots

http://www.youtube.com/watch?v=L915JJMcu4sSlide33

What happens when satellites plunge back toward Earth?

This happened on Sept. 22, 2011.

Watch Out! NASA UARS satellite to hit Earth... Anywhere!

(Upper Atmosphere Research Satellite)

http://www.youtube.com/watch?v=vwnNTllrAdM

http://www.youtube.com/watch?v=GCd4VwmNATU&feature=relatedSlide34

Comparing velocity, radius and period:

Radius

r

Period

T

Velocity

v

Surface/ LEO

6.38 x 10

6

m

83 min.

8 km/s

Geostationary

4.23 x 10

7

m

24 hr.

3 km/s

Moon

3.84 x 10

8

m

27.3 days

1 km/sSlide35

Does this make sense?

Doesn’t v = 2

π

r/T?

Then doesn’t that mean

that as r ↑, v ↑?

But v depends on T, so to eliminate v:

F

c

 = F

g

⇒ m

S

v

2

/r

 = Gm

S

m

E

/ r

2

⇒ v = √Gm

E

/

r

v

2

= Gm

E

/r

 = 4π

2

r

2

/

T

2

r

3

/T

2

 = 

Gm/

4π

2

= constant 

r

3

 ∝ 

T

2

So as r increases, T increases. Slide36

Summary - 2 ways to find velocity:

V = 2

π

r / T

V = √ (GME/r)

(This means square root!)

Where r is the orbital radius, not the height above the surface. Slide37

Problem Solving

What is the speed of a space shuttle in a circular orbit 1000km above Earth’s surface?

The mass of Earth is 6 x 10

24

kg and the radius of Earth is 6.38 x 10

6

m. G = 6.67 x 10-11. Slide38

Solution

R = 7.38 x 10

6

m

Fc = Fg

V

2 = GMe/RV = 7.35 x 103 m/s or 16,500 mphSlide39

NASA GOES - P Mission Overview

http://www.youtube.com/watch?v=QpBSwwCPC94&feature=related

Cup of coffee

http://www.youtube.com/watch?v=pk7LcugO3zg&feature=related

Going to the bathroom

http://www.youtube.com/watch?v=HUe2HcFUPSo&feature=related

Slide40

Space Junk Video

4 min.

http://videos.howstuffworks.com/hsw/19197-satellite-technology-orbit-and-orbital-debris-video.htm

Slide41

Real Time Satellite Tracking

Click and drag applet

http://www.n2yo.com/

Slide42

Tracking ISS

Another ISS tracking site.

http://spaceflight.nasa.gov/realdata/tracking/index.html

Slide43

Satellite Tracking

Position of ISS and other satellites

http://science.nasa.gov/Realtime/jtrack/3d/JTrack3d.html

Slide44

History of ISS

http://www.nasa.gov/worldbook/intspacestation_worldbook.html

Slide45

Attitudes of ISS

Adjusting the angle for solar panels.

http://spaceflight.nasa.gov/station/flash/iss_attitude.html

Slide46

Interactive Reference Guide

Videos of how the crew eats, sleeps and exercises.

http://www.nasa.gov/externalflash/ISSRG/

Slide47

Upcoming Launches

http://www.nasa.gov/missions/highlights/schedule.html

Slide48

NASA in motion

Link to NASA Drawing VideoSlide49

Cup of Joe

Link to Cup of Joe Video Slide50

Atlantis leaves ISS

Link to Undocking VideoSlide51

Takeoff and Landing of Discovery

http://www.youtube.com/watch?v=5B9ff-2bDb4

Slide52

Apollo Guys – Co Ops

http://www.youtube.com/watch?v=sItKDSf0xl8

Link Apollo Guys (Apologize)

Watching on the screen

Saturn V lifts off the ground

After many sims,

Flight control has got it down

You say that its not easy, but

Astronauts are all moonbound and wait

Were watching them on TV

Walking on the lunar ground and say

We did it Apollo Guys! Slide53

How GPS WorksSlide54

The dashed lines show the actual intersection point, and the gray bands indicate the area of uncertainty. Slide55

The solid lines indicate

where the GPS receiver "thinks" the spheres

are located. Because of errors in the

receiver's internal clock, these spheres do

not intersect at one point.

Three spheres are necessary to find position in two dimensions, four are needed in three dimensions. Slide56

Problem Solving #1

A satellite over Jupiter is placed 6 x 10

5

m above surface, given mass of Jupiter, find v.

Mass of Jupiter = 2 x 10

27

kg,

R

adius of Jupiter

= 71,492

kilometers

So r = radius of Jupiter + height over surface

r = 7.2 x 10

7

m

V

2

= GM

J

/r

v

2

= 1.76 x 10

9

m/s

v = 4.195 x 10

4

m/sSlide57

Problem Solving #2

A

satellite wishes to orbit the earth at a height of 100 km (approximately 60 miles) above the surface of the earth. Determine the speed, acceleration and orbital period of the satellite. (Given:

M

earth

= 5.98 x 1024

kg,

R

earth = 6.37 x 10

6

m)

Speed =

= 7.85 x 10

3

m/s

Acceleration =

a = 9.53 m/s

2

Orbital

period =

T = 5176 s = 1.44

hrsSlide58

#3

One

of Saturn's moons is named

Mimas

. The mean orbital distance of

Mimas

is 1.87 x 108 m. The mean orbital period of Mimas is approximately 23 hours (8.28x10

4

s). Use this information to estimate a mass for the planet Saturn.

Using the T and R values given, the T

2

/ R

3

ratio is 1.05 x 10

-15

. This ratio is equal to 4*pi

2

/ G *

M

central

.

Mass

of

S

aturn

can be found to be 5.64 x 10

26

kg.Slide59

#4

Satellites circling unknown planet. Sat1 has v1 = 1.7 x 10

4

m/s, and r = 5.25 x 10

6

m. Sat2 has r = 8.6 x 10

6 m. Find v for Sat2.

V

2

= GM

PLANET

/r

So M

PLANET

G

=

constant

= v

2

r

V

1

2

r

1

= v

2

2

r

2

V

2

= 1.33 x 10

4

m/sSlide60

Which of following statements is accurate regarding man-made satellites?

A. It is possible to have a satellite traveling at either a high speed or at a low speed in a given circular orbit.

B. Only

circular orbits (and not elliptical ones) are possible for artificial satellites.

C. A

satellite in a large diameter circular orbit will always have a longer period of revolution about the

e

arth than will a satellite in a smaller circular orbit.

D. The

velocity required to keep a satellite in a given orbit depends on the mass of the satellite

. Slide61
Slide62

Next Genertion Car Navigation

http://my.clarion.com/en-ca/html/products

Slide63

Practice Questions Giancoli

http://cwx.prenhall.com/giancoli/chapter5/multiple1/deluxe-content.html

Slide64

Satellites orbiting earth

http://www.youtube.com/watch?v=gEOAp6k72gc

Slide65

Launching Satellites

http://www.youtube.com/watch?v=W4PE8LK2Ga0

Slide66