Satellites in Orbit
Mark M. / Physics 336 / 17 April 1997
After the launching of a satellite there has to be a way to get the
satellite into the correct position so that it will attain the correct
orbit pattern. There are different stages and position placement tactics
used to set the satellite in it's correct orbit. This is accomplished from
the signals sent from the command center to the satellite and the on-board
rockets move the satellite into position. Most of the time the people behind
the scenes that are controlling the satellites like to put the satellite
into a geosynchronous orbit. This is one kind of orbit that is in time
with the Earth's rotation. There are certain times in which this type of
orbit will be used to position the satellite.
Initial Positioning of Satellites
To begin the process of putting the satellite in orbit there are three
stages. The first stage raises the satellite to an elevation of about 50
miles. The second stage raises the satellite 100 miles and the third stage
places it into the transfer orbit. The satellite is placed in its final
geosynchronous orbital slot by the AKM, a type of rocket used to move the
satellite, which is fired on-command to allow the satellite to attain the
apogee, the farthest point from Earth, of its elliptical orbit. A final
thing to check is to make sure that a satellite that is to orbit the Earth
is positioned at least 100 miles above the Earth's surface so that the
atmospheric drag will not slow the satellite down (Cook 1).
Adjusting While in Orbit
Also important in the orbit of a satellite is the adjusting of it while
in orbit. This is done through the use of rockets. Throughout the life
of the satellite the orbit and attitude, the direction it points, must
be adjusted. Generally they have on-board rockets for this purpose. Sometimes
the rocket may be fired to accelerate the satellite and move it to a higher
orbit or to decelerate the satellite and move it to a lower orbit. It can
also be changed by firing the rocket to the side which changes the direction
the satellite points. With the use of these special rockets the satellite
can be moved at any time to any necessary position for any reason or another.
The rockets help keep the satellite on its course without the possibility
of it losing altitude or falling right out of the orbit in which it was
in. A satellite's position has much to do with the time. For example, a
satellite located 22,300 miles above the Earth's surface which is said
to be synchronous, takes exactly 24 hours to orbit around the Earth once.
This is said to be synchronous because it is synchronized with the Earth's
rotation. Not all orbits are said to be synchronous and the time required
for a satellite to complete one revolution around the Earth depends on
its altitude. The laws that govern a satellite in orbit are the same laws
that govern the motion of natural satellites and it travels around the
planet in a nearly circular orbit when it reaches the 100 mile mark above
the Earth's surface (Compton's Encyclopedia).
Command and Control
The command and control centers for the satellites play a big role
in the keeping of a satellite in a particular orbit. As explained by Burke
when he says, "Satellite command and control is exercised from the
operational control nodes located at Orizuka Air Station, California, and
Falcon Air Force Base, Colorado." From there, many of the techniques
of positioning are controlled. Burke also says, "The AFSCN, Air Force
Satellite Control Network, has a command and control segment that enables
execution of phases used to position satellites." In conclusion Burke
says in his article that the command center has tracking and command support
from launch preparation to on-orbit operations (1).
Conclusion
It is interesting to know that the people who work with satellites
have a large amount of control from a small room located on an Air Force
base. Through their work the satellite can be launched, positioned, and
adjusted with the touch of a few buttons. Although it is not as easy as
it may seem. These people have to know exactly what there are doing or
the satellite may not attain the proper orbit. The job is hard, but many
satellites have been put in orbit without any problems.
References
Burke, John. "Satellite and Launch Control Systems Program."
1995: United States Air Force.
Cook, William C. "Launching Satellites into Orbit." 1996:
America On-Line. 2 January 1997.
"How Artificial Satellites Work." Compton's New Century
Encyclopedia and Reference Collection 2. CD-ROM. Compton's New Media,
Inc. 1995.