### Author Topic: Ejs Open Source Geostationary Satellite around Earth Java Applet  (Read 44728 times)

#### lookang

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##### Ejs Open Source Geostationary Satellite around Earth Java Applet
« on: June 30, 2010, 11:58:49 pm »
Ejs Open Source Geostationary Satellite around Earth Java Applet
by lookang.
Thanks to Prof Paco for his Ejs Open Source Earth and Moon Model and implementing Ejs and Java3D.
Thanks to Prof Fu-Kwun Hwang sharing his valuable knowledge and constant help in my pursuit to continue my life long learning
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1877.0
This model is a simple angular velocity model which assumes
t = t+dt; // added by lookang for timer
angle += angleincrease;
anglez += anglezincrease;
rotation += 2*Math.PI/24*dt; // lookang for real time
rotString = "z:"+rotation;
The orbits are just illustration and does not contains physics newton's 2nd law of motion.

Full screen applet or Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
• Please feel free to post your ideas about how to use the simulation for better teaching and learning.
• Post questions to be asked to help students to think, to explore.
• Upload worksheets as attached files to share with more users.
Let's work together. We can help more users understand physics conceptually and enjoy the fun of learning physics!

This Geostationary Satellite around Earth Model is a simple angular velocity model that uses the Java3D implementation for realistic visualization of satellite objects in geostationary orbits at three different locations namely (near Singapore, near Africa and America in model 1,2,3).
Students can explore the meaning of geostationary orbits, cases of non-geostationary orbits( mode 4,5,6) and even non-physics orbit (mode 7).

to enable Java 3D, install java 3D http://java3d.java.net/binary-builds.html
select the installer like Installers
j3d-1_5_2-linux-amd64.bin
j3d-1_5_2-linux-i586.bin
j3d-1_5_2-solaris-sparc.bin
j3d-1_5_2-solaris-x86.bin
j3d-1_5_2-windows-amd64.exe
j3d-1_5_2-windows-i586.exe

If it doesn't show up in the web browser, it is likely due to The error seem to be Caused by:

copy to a location you have permission to read and write like d:/
the file is this found C:Program FilesJavajre6libsecurityjava.policy.

use Jedit to edit it in D:
add code to the last line
BOOM! Java 3D on Ejs Web applets Grin Grin
attached is the java.policy for windows xp system

http://youtu.be/PS4FDOurbhw

« Last Edit: April 18, 2013, 02:49:28 pm by lookang »

#### lookang

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##### Re: Ejs Open Source Geostationary Satellite around Earth Java Applet
« Reply #1 on: June 30, 2010, 11:59:27 pm »
Activity J by lookang
show an understanding of geostationary orbits and their application

drag around the sim to find the position of Singapore.
reset the sim
select from the drop down menu "Geostationary near sg"
observe the position of the satellite and the yellow line draw down perpendicular to the surface of the Earth surface towards the center of the Earth's core.
Describe what you observe in terms of the
a ) time taken to rotate one full revolution
b) direction of rotation
c) angular velocity of satellite
d) relative position from the Earth surface.
reset the sim or select another menu
you may explore mode 2 "Geostationary near Africa"
you may explore mode 3 "Geostationary near America"
check if the sim is correct for each case.

select mode 4 "Non-geostationary due to direction"
explain if this orbit motion is
i) possible?
ii) geostationary about Earth, if not, explain why clearly in terms of a) period b)rotation spin direction c) in the plane of equator.

select mode 5,51,52,53 "Non-geostationary due to angular speed"
explain if this orbit motion is
i) possible?
ii) geostationary about Earth, if not, explain why clearly in terms of a) period b)rotation spin direction c) in the plane of equator.

select mode 6 "Non-Geostationary generally"
explain if this orbit motion is
i) possible?
ii) geostationary about Earth, if not, explain why clearly in terms of a) period b)rotation spin direction c) in the plane of equator.

select mode 7 "Unlikely Orbits"
explain if this orbit motion is
i) possible? if not, explain why clearly.
ii) geostationary about Earth, if not, explain why clearly in terms of a) period b)rotation spin direction c) in the plane of equator.

Geostationary Satellites
The term Geo-stationary implies a satellite fixed about a position above the earth.
This is possible because such satellites have the same period as the Earth’s rotation (T = 24 hours) and it is directly above the equator. Therefore, it appears stationary.
For it to appear stationary from any position on Earth, the plane of rotation of the satellite must be in the plane of the Equator.
Example of geostationary satellites are GMS1, GEOS, METEOSAT etc. Most of these satellites are used for commercial and military purposes

http://en.wikipedia.org/wiki/Geosynchronous_satellite
A geosynchronous Satellite is a satellite whose orbit on the Earth repeats regularly over points on the Earth over time. If such a satellite's orbit lies over the equator and the orbit is circular, it is called a geostationary satellite. The orbits of the satellites are known as the geosynchronous orbit and geostationary orbit.

There are approximately 300 operational geosynchronous satellites.

Geostationary satellites appear to be fixed over one spot above the equator. Receiving and transmitting antennas on the earth do not need to track such a satellite. These antennas can be fixed in place and are much less expensive than tracking antennas. These satellites have revolutionized global communications, television broadcasting and weather forecasting, and have a number of important defense and intelligence applications.

One disadvantage of geostationary satellites is a result of their high altitude: radio signals take approximately 0.25 of a second to reach and return from the satellite, resulting in a small but significant signal delay. This delay increases the difficulty of telephone conversation and reduces the performance of common network protocols such as TCP/IP, but does not present a problem with non-interactive systems such as television broadcasts..

Another disadvantage of geostationary satellites is the incomplete geographical coverage, since ground stations at higher than roughly 60 degrees latitude have difficulty reliably receiving signals at low elevations

2 added line from satellite to earth surface for visualization
3 added text "35 700 km fixed position of satellite relative to Planet"
4 added satellite picture from googling for images, sorry cannot track where i got it did it at midnight, if you own the picture and would like to add your credits, reply the post!
got it http://www.the3dstudio.com/thumbs_large/2009/05/02/860120BD-61DB-4157-8099-0A07962AEB14_thumb.jpg
5 remove 3D java and simple java because this applet needs to run under Java3D for earth graphics to appear
6 added a combo menu for the common misconceptions of geostationary orbits
Geostationary near sg
Geostationary near Africa
Geostationary near America
Non-geostationary due to direction
Non-geostationary due to angular speed
Non-Geostationary generally
Unlikely Orbits
8 made the relation for rotation += 2*Math.PI/24*dt; // go 1 round in 24 hours. dt
12 May 2011
added radio buttons mode =1 to 7 to increase ease of selection drop-down menu as Java 3D blocks the menu when selecting it.
add picture of SG ZA and US for ease of association during simple java mode
26 June 2011
added permanent geostationary (red) above SG for comparison with orbit in play
added axes of rotation of earth and orbit for ease of teacher explanation according to Right hand grip rule.
added image for simple 3D and java 3D 25x25
contributed to http://commons.wikimedia.org/w/index.php?title=Special:ListFiles&user=Lookang for animated thumbnails always use 220x220 the largest that work for me. Tried 300x300 but it didn't animated in thumbnail mode.

known bugs
Java 3D cannot render the arrows head correctly, the orientation is wrong but is simple 3D it is ok

things to do
Mass of Earth = 6.0 x 1024 kg
Radius of Earth = 6.40 x 10^6 m
Geostationary Orbit radius = 4.23 x 10^7 m
Height above Earth’s surface = 4.23 x 10^7 - 6.40 x 10^6 = 3.59 x 10^7 m
« Last Edit: April 04, 2012, 02:44:44 pm by lookang »

#### ahmedelshfie

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##### Re: Ejs Open Source Geostationary Satellite around Earth Java Applet
« Reply #2 on: July 01, 2010, 12:02:54 am »
Good job i like your idea

#### lookang

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##### Re: Ejs Open Source Geostationary Satellite around Earth Java Applet
« Reply #3 on: July 01, 2010, 11:15:31 am »
done!
hope students learn from it and suggest what can be done more to improve it!

#### lookang

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##### Re: Ejs Open Source Geostationary Satellite around Earth Java Applet
« Reply #4 on: July 03, 2010, 12:40:10 am »
Ejs Open Source Geostationary Satellite around Earth Java Applet
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1877.0

* Tell me. I may not get it, I'm sure to forget it.
* Show me. I may get it, I'll remember it for a little while.
* Have me do it. I'll understand it, it may stick for a while.
music from
Satellite Mind
artist: Metric
album: Fantasies
length: 3:42
label: Metric
genre: Alternative & Punk

enjoy!

this was done 4 years back by a friend of mine
« Last Edit: June 08, 2011, 10:52:50 pm by lookang »

#### lookang

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##### Re: Ejs Open Source Geostationary Satellite around Earth Java Applet
« Reply #5 on: June 23, 2011, 02:49:23 pm »
request by teacher

1) can you show the axis of rotation for Earth and for the satellite's orbit for all the modes? So that the students see that the axis must be the same for geostationary (mode 6)
2) For mode 7, can you reverse the direction of satellite's orbit so that it is rotating in the same direction as Earth?

#### lookang

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##### Re: Ejs Open Source Geostationary Satellite around Earth Java Applet
« Reply #6 on: June 25, 2011, 11:30:52 pm »
my teacher friend says that web deploy java 3d didnt show up anymore.
the solution is

to enable Java 3D, install java 3D http://java3d.java.net/binary-builds.html
select the installer like Installers
j3d-1_5_2-linux-amd64.bin
j3d-1_5_2-linux-i586.bin
j3d-1_5_2-solaris-sparc.bin
j3d-1_5_2-solaris-x86.bin
j3d-1_5_2-windows-amd64.exe
j3d-1_5_2-windows-i586.exe

If it doesn't show up in the web browser, it is likely due to The error seem to be Caused by:

copy to a location you have permission to read and write like d:/
the file is this found C:Program FilesJavajre6libsecurityjava.policy.

use Jedit to edit it in D:
add code to the last line
BOOM! Java 3D on Ejs Web applets Grin Grin
attached is the java.policy for windows xp system

http://youtu.be/PS4FDOurbhw

#### lookang

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• Posts: 1772
• http://weelookang.blogspot.com
##### Re: Ejs Open Source Geostationary Satellite around Earth Java Applet
« Reply #7 on: June 26, 2011, 11:58:42 am »
using the latest Ejs 4.3.3.2 from http://www.compadre.org/osp/items/detail.cfm?ID=7305

but still have errors during running
at org.opensourcephysics.drawing3d.simple3d.SimpleElementTrail.computePositions(Unknown Source)
at org.opensourcephysics.drawing3d.simple3d.SimpleElementTrail.processChanges(Unknown Source)
at org.opensourcephysics.drawing3d.Element.processChanges(Unknown Source)
at org.opensourcephysics.drawing3d.ElementTrail.processChanges(Unknown Source)
at org.opensourcephysics.drawing3d.Group.processChanges(Unknown Source)
at org.opensourcephysics.drawing3d.simple3d.SimpleDrawingPanel3D.paintDrawableList(Unknown Source)
at org.opensourcephysics.drawing3d.simple3d.SimpleDrawingPanel3D.paintEverything(Unknown Source)
at org.opensourcephysics.drawing3d.simple3d.SimpleDrawingPanel3D.render(Unknown Source)
at org.opensourcephysics.drawing3d.simple3d.SimpleDrawingPanel3D.render(Unknown Source)
at org.opensourcephysics.drawing3d.DrawingPanel3D.render(Unknown Source)
at org.colos.ejs.library.control.drawing3d.ControlDrawingPanel3D.finalUpdate(Unknown Source)
at org.colos.ejs.library.control.EjsControl.finalUpdate(Unknown Source)
at org.colos.ejs.library.Animation.update(Unknown Source)
at org.colos.ejs.library.Animation.step(Unknown Source)
at org.colos.ejs.library.Animation.run(Unknown Source)

anyone has suggestions how to overcome this
ok i overcome this by setting number of point in Trail = 499!

#### lookang

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##### Re: Ejs Open Source Geostationary Satellite around Earth Java Applet
« Reply #8 on: June 28, 2011, 09:32:08 am »
teacher request

For the geostationary model:
>> 1) can you make the equator plane more obvious?

> Ok done transparency = 200 instead of 50 previously
>
>> 2) can you show the radius of orbit for the satellite?

>> 3) For mode 7, can you make the satellite rotate at the same rate as Earth?
>> 4) For mode 6, the axis of rotation for satelllite is wrong, even for non 3D
>> model. Can you correct it?
>>
> It is correct, I dont get why u say wrong.
« Last Edit: June 28, 2011, 10:21:27 am by lookang »

#### lookang

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##### Re: Ejs Open Source Geostationary Satellite around Earth Java Applet
« Reply #9 on: March 09, 2012, 03:49:30 pm »
discussion with teacher

Geostationary orbit
- please add a button to reveal & hide "gravitational force" acting on the satellite towards the centre of the Earth for all the modes.

done!

other changes

R = 6.37E6 m = 0.637 in model
R geostationary = 4.23E7 m= 4.27 in model

circular motion r=Re, T = 1.4 hr
circular motion r=2*Re, T = 3.98 hr
circular motion r=3*Re, T =7.30 hr
circular motion r=10.5*Re, T = 48 hr
expanding on the non-geostationary due to speed.

remove simple 3D as EJS4.3.6 supports java 3D and also a bug toggling from simple to java 3d.
enjoy!
« Last Edit: March 12, 2012, 04:22:43 pm by lookang »

#### lookang

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##### Re: Ejs Open Source Geostationary Satellite around Earth Java Applet
« Reply #10 on: April 04, 2012, 02:27:30 pm »

Geostationary Satellite around Earth Model

This Geostationary Satellite around Earth Model is a simple angular velocity model that uses the Java3D implementation for realistic visualization of satellite objects in geostationary orbits at three different locations namely (near Singapore, near Africa and America in model 1,2,3).
Students can explore the meaning of geostationary orbits, cases of non-geostationary orbits( mode 4,5,6) and even non-gravity physics orbit  (mode 7).

Geostationary Satellites
The term Geo-stationary implies a satellite fixed about a position above the earth. This is possible because such satellites have the same period as the Earth’s rotation
1 (T = 24 hours)
2 same rotational sense as the earth's rotation spin
3 is directly above the equator in other words the plane of rotation of the satellite must be in the plane of the Equator
Therefore, it appears stationary.

Application
Example of geostationary satellites are GMS1, GEOS, METEOSAT etc. Most of these satellites are used for commercial and military purposes

Main Simulation View
The simulation has a Earth and a Satellite object

Allows for selecting what motion of Satellite is simulated.
mode = 1 Geostationary near sg
mode = 2 Geostationary near Africa
mode = 3 Geostationary near America
mode = 4 Non-geostationary due to direction
mode = 5 Non-geostationary due to angular speed circular motion r=Re, T = 1.4 hr
mode = 51 circular motion r=2*Re, T = 3.98 hr
mode = 52 circular motion r=3*Re, T =7.30 hr
mode = 53 circular motion r=10.5*Re, T = 48 hr
mode = 6 Non-Geostationary generally
mode = 7 Unlikely Orbits

Checkboxes
show: equator Plane, for visualizing the Earth's rotating equator plane
Geo stationary, for visualizing a geostationary object (RED) for comparative observation with the other modes.
Show text: 35 700 km fixed position of object relative to planet eart.
Axes earth: show spin axes of the rotation of earth in GREEN
Axes satellite: show spin axes of the rotation of satellite in MAGENTA
Force: pair of action reaction force of equal magnitude, opposite direction and on different bodies. (Newton's 3rd Law)

Buttons
Play
Step Forward
Reset
have their usual meaning.

Credits:
The Geostationary Satellite around Earth Model was created by created by lookang (based on a earlier model Francisco Esquembre http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1830.0) by using the Easy Java Simulations (EJS) version 4.3.6 authoring and modeling tool. An applet version of this model is available on the NTNU website . Shout our thanks to the Ejs community namely, Francisco Esquembre , Fu-Kwun Hwang and Wolfgang Christian for their professional learning community support. You can examine and modify this compiled EJS model if you run the model (double click on the model's jar file), right-click within a plot, and select "Open EJS Model" from the pop-up menu. You must, of course, have EJS installed on your computer. Information about EJS is available at: http://www.um.es/fem/Ejs/ and in the OSP comPADRE collection http://www.compadre.org/OSP/.

#### lookang

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##### Re: Ejs Open Source Geostationary Satellite around Earth Java Applet
« Reply #11 on: April 05, 2012, 02:29:51 pm »
more changes

remove 2 orbits
now just have one slower and one faster
EarthAndSatelite.html
EarthAndSateliteactivity.html
reduced to20 FPS now.
ecliptic so that it appears circular. 36,36,36 for a rounder plane of equator
"Show text" is too small to read in J3D. font increased
forces check-box text as "Free Body Diagram"

earth disappear when Free Body Diagram is selected to allow visualization of point mass forces acting on them.

enjoy!

#### lookang

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##### Re: Ejs Open Source Geostationary Satellite around Earth Java Applet
« Reply #12 on: April 27, 2012, 01:29:38 pm »
more discussion with teacher

1) can you make the satellite in mode 6 orbit with period = 24 hours?
added a new polar orbit with T = 24hours.
redesign the equation
x = R*(Math.cos(angle)*Math.cos(anglez));
y = R*(Math.sin(angle)*Math.cos(anglez));
z = R*Math.sin(anglez); // lookang for other orbits

2) The "Show Text" button doesn't seem to work.
it is removed as there is a problem in Java3D implementation as the text does not move with he satellite.
we can add it in after EJS can generate the code correctly for Java3D.

3) The simulation 'hangs' after it is being played for some time.
The whole thing just stops and I need to close the window.
i cant solve it unless the problem is repeatable

#### lookang

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##### Re: Ejs Open Source Geostationary Satellite around Earth Java Applet
« Reply #13 on: April 30, 2012, 10:10:57 am »
more discussion

added mode back due to problem of Java3D after using the combo list in full screen mode
transparent Earth after showing Free Body Diagram

geostationary show is a bug, toggle the button should be fine.