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

changes made:

1 added earth equator plane from http://www.compadre.org/osp/items/detail.cfm?ID=9390
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
pedagogy wise, i added
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
7 added t and dt
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.
color scheme added
added image for simple 3D and java 3D 25x25
made more check able stuff
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.
added to http://en.wikipedia.org/wiki/Geostationary_orbit


known bugs
Java 3D cannot render the arrows head correctly[img]http://www.phy.ntnu.edu.tw/ntnujava/index.php?action=dlattach;topic=1877.0;attach=4260;image[/img], 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