Maureen P. / Physics Sec. #337 / 19 May 1997
In order for satellites to work properly, controlling them is very
important and necessary. People on the ground have complete control over
their satellite and need to be able to know where the satellite is at all
times. They also should be in contact with the satellite at all times.
Controlling a satellite can be accomplished by rocket engines, specific
types of tracking, guidance systems and Telemetry links.
Rocket engines are one of many ways to control satellites. They help
to keep satellites from drifting off course. In order to do this, some
systems use small bursts from the rocket engines which are placed around
the satellite. One specific rocket engine is the Agena rocket. This rocket
is on a satellite called the Seasat. It keeps pointing toward the Earth
and gives the satellite an elongated shape which helps provide stabilization.
Satellites are tracked from tracking stations. "Tracking stations
are usually ground based but have been placed aboard ships, aircrafts and
satellites" (Dooling). There are also specific types of tracking.
One type is optical tracking. "Optical tracking is used mainly for
orbit determination of inactive spacecraft or of satellites equipped with
optical ranging" (Dooling). Another type of tracking is radio tracking.
"Radio tracking is used extensively to acquire data from spacecrafts
and to transmit commands" (Dooling).
Guidance systems are also a very important part of controlling satellites.
They help the satellite to function and to stay on target. There are different
types of guidance systems as well. Radio-command is one example. "In
the radio-command guidance system, changes in velocity and direction are
broadcasted by the spacecraft to a station on the ground. The data is fed
into computers that make the calculations required to keep the craft on
course. The necessary adjustments are then broadcasted back to the craft
and control motors on the craft to carry out the instructions. This procedure
may be directed by the ground station or it may be automatic" (Waters
305). One other type of guidance system is the inertial-guidance system.
"In an inertial-guidance system, the velocity and direction are measured
by an to board sensor system. This information if then fed onboard computers
and flight controls" (Waters 305).
Telemetry links aid in the way information is transmitted to and from
the satellites. "Commands from the ground and details of how the satellite
is functioning are transmitted to and from the satellite by Telemetry links.
Many scientific satellites collect data continuously but are only in view
of the ground stations for a short time. In this case, the data will be
recorded on a tape recorder and played back at a higher speed when in contact
with the ground station" ("Satellite" 2040).
As you can see, there are many factors involved in controlling a satellite.
Some ways that satellites are controlled are by the use of rocket engines,
tracking stations, guidance systems and Telemetry links. These are just
some examples of how to control a satellite. There are many other ways
because the world of satellites is a big field of physics and is being
Couper, Heather and Nigel Henbest. Space Probes and Satellites.
New York: Franklin Watts, 1987.
Dooling, David. "Tracking Station." Grolier Encyclopedia
. CD-ROM. Grolier Electronic Publishing, 1993.
"Satellite." How it Works the Illustrated Encyclopedia
of Science and Technology. New York: Kingfisher Books, 1991.
Waters, Tom. "Space Satellites." The New Book of Popular
Science. Connecticut: Grolier Incorporated, 1996.