Table of Contents

Satellite Communications

Space Age Telecommunications in Canada

Teacher Background / Student sheets

It is assumed that teachers are familiar with the meaning of terms such as wavelength and frequency and with the scientific unit prefixes and their symbols (e.g. Gigahertz - GHz).

Definitions:

Amplitude Modulation – this describes a method by which information is placed on a carrier wave. The amplitude of the carrier wave is adjusted to correspond to the information being sent. This type of modulation is usually found in radio transmissions.

Antenna Footprint – this is usually referred to when showing the strength of the satellite signal on the ground. For Canadian Satellite Anik E2 (Ku), which is a domestic satellite, the Antenna Footprint covers Canada and very little else. For Anik E1 (Ku) which works in the American market, the Antenna Footprint covers the US. The numbers on the figures are a representation of the strength of the signal sent down by the satellite.

Bandwidth – this represents how much information can be transmitted using a particular Carrier Wave. The bandwidth needed is proportional to the amount of information to be sent. The higher the carrier wave frequency the larger the bandwidth available and the more data can be transmitted at one time. An analogy to the Internet is that a dial-up connection can not carry information as fast as a cable connection. This is due in part to the dial-up connection not being able to transmit as high a frequency as the cable connection.

Carrier Wave – this is a specific wavelength of electromagnetic radiation used to transmit information from a transmitter to a receiver.

Concept Mapping – this is a visual or graphical data organization technique used to help students organize, synthesize and integrate information.

Electromagnetic Radiation – this is radiation which includes heat, visible light, microwave, X-rays, radio and TV signals etc. Communications satellites use a variety of frequencies of electromagnetic radiation ranging from 2 GHz to 20 GHz. 6 GHz is sometimes known as the C-band while 12.6 GHz is known as the Ku band (pronounced kay-you) and 20 GHz is know as the Ka band (pronounced kay-eh). Ka is used for direct TV broadcast satellites.

Frequency Modulation – this describes a method by which information is placed on a carrier wave. The frequency of the carrier wave is adjusted to represent the information being transmitted. This type of modulation is found in radio and television transmissions.

Geostationary Orbit (Clarke Orbit) – this orbit is at the specific height, about 35,000 km, above the equator, where the time needed to complete one orbit by the satellite is the same as the rotation period of Earth.

Receiver – is an electronic device which converts electromagnetic waves (usually at the carrier wave frequency) to an electronic signal that is comprised of the information embedded in that signal (the modulation of that signal).

Spin-Stabilized – when an object is spinning it is more difficult to change its orientation in space (e.g. a bicycle is more stable when it is moving). Before they reach their final destination, rockets used to explore the upper atmosphere and spacecraft are usually spun to minimize the effect of small forces (perturbations).