Grade 9 Reading Task (Modified Sample from OSSLT)
Markville Secondary School: Liter8 Program
Liter8 Lesson Plan
Nick Keehn, Sahar Dolatshahi / Date:
November 12th, 2007
Liter8 Skill:
I: Increase Reading and Comprehension Skills / Grade / Subject / Level:
9 Satellite Communications Science / Unit:
Astronomy
Indicators of Liter8 Skill (cut and paste applicable indicators):
> highlighting key words, passages, quotes, elements in texts
> interpreting text forms
> organizing ideas from text: note-taking skills, concept maps, visualizing
> differentiating between most and least important ideas / information
> identifying main points, thesis, main arguments
Activity:
1. This is a Sample Activity for the OSSLT (Section 1: Reading) that has been modified to relate to the Grade 9 Science course. The format is similar to the OSSLT.
2. Optional preliminary lesson:
a) Review skills and techniques in reading informational texts such as skimming, highlighting key words, quotes, making notes, identifying main thesis and supporting arguments.
3. Once the students have had the chance to read the article and highlight the new words, they should look up the words they do not know and write down their meaning (on-line dictionaries could also be used).
4. Review the new scientific vocabulary in class, ask students to explain words based on what they have found from the dictionary, and provide clarification/explanation as required.
4. Give students handout and instruct them to read the article “Satellite Communications Basics” and answer the questions.
4. Teacher can collect activity to provide constructive feedback on writing sample. Article and questions can be taken up and discussed as a class.
Resources / Handouts:
1. OSSLT Sample Reading Activity: “Satellite Communications Basics”
Notes / Reflections:
· This lesson can be used as a Formative Activity in the middle or end of a unit to assess reading and comprehension levels in your class.
Read the selection below and answer the questions that follow it.
The basic elements of a satellite communications system are shown in Figure 1 below. The process begins at an earth station--an installation designed to transmit and receive signals from a satellite in orbit around the earth. Earth stations send information in the form of high powered, high frequency (GHz range) signals to satellites which receive and retransmit the signals back to earth where they are received by other earth stations in the coverage area of the satellite. The area which receives a signal of useful strength from the satellite is known as the satellite's footprint. The transmission system from the earth station to the satellite is called the uplink, and the system from the satellite to the earth station is called the downlink.
1. What is an orbit?
When a satellite is launched, it is placed in orbit around the earth. The earth's gravity holds the satellite in a certain path as it goes around the earth, and that path is called an "orbit." There are several kinds of orbits. Here are three of them.
A. Low Earth Orbit (LEO)
A satellite in low earth orbit circles the earth 200 to 1000 km above the earth's surface. Because it is close to the earth, it must travel very fast to avoid being pulled out of orbit by gravity and crashing into the earth. Satellites in low earth orbit travel about 28,000 km/h. These satellites can circle the whole earth in about an hour and a half.
B. Medium Earth Orbit (MEO)
Communications satellites that cover the North Pole and the South Pole are placed in a medium altitude, oval orbit. Instead of making circles around the earth, these satellites make ovals. Receivers on the ground must track these satellites. Because their orbits are larger than LEOs, they stay in sight of the ground receiving stations for a longer time. They orbit 10,000 to 20,000 km above the earth.
C. Geostationary Earth Orbit (GEO)
A satellite in geosynchronous orbit circles the earth in 24 hours—the same time it takes the earth to rotate one time. If these satellites are positioned over the equator and travel in the same direction as the earth rotates. From the ground, it appears that the satellite is not moving at all. In this high orbit, GEO satellites are always able to "see" the receiving stations on the ground, and their signals can cover a large part of the planet. Three GEO satellites can cover the globe, except for the parts at the North and South poles.
2. What's Inside a Satellite?
The launching engine that puts the satellite into orbit detaches and becomes space garbage. The rest of the satellite that orbits the Earth has a lot of equipment packed inside.
1. The power subsystem generates electricity from the solar panels on the outside of the spacecraft. The solar panels also store electricity in storage batteries, which provide power when the sun isn't shining on the panels. The power is used to operate the communications subsystem.
2. The communications subsystem receives signals from the earth, amplifies or strengthens them, and transmits (sends) them to another satellite or to a ground station.
3. The thermal control subsystem keeps the active parts of the satellite cool enough to work properly. It does this by directing the heat that is generated by satellite operations out into space, where it won't interfere with the satellite.
4. The pointing control subsystem keeps the satellite in the correct location. Satellites can't be allowed to jiggle or wander, because if a satellite is not exactly where it belongs, pointed at exactly the right place on the earth, the television program or the telephone call it transmits to you will be interrupted. When the satellite gets out of position, the attitude control system tells the propulsion system to fire a thruster that will move the satellite back where it belongs.
5. Operators at the ground station need to be able to transmit commands to the satellite and to monitor its health. The command and data subsystem provides a way for people at the ground stations to communicate with the satellite.
3. Electromagnetic (EM) Radiation
Electromagnetic Radiation includes heat, visible light, microwave, X-rays, radio and TV signals. The frequency of the waves is measured in units called gigahertz (GHz). Communications satellites use a variety of frequencies of electromagnetic radiation ranging from 2 GHz to 20 GHz. Direct TV broadcast satellites use the 20 GHz frequency.
Ten Years and Over Two Billion Kilometres for RADARSAT-1
The Canadian Space Agency's RADARSAT-1 satellite celebrated its tenth anniversary in 2005, having flown 2,354,120,900 km while orbiting the Earth. The word radar is short for “radio detection and ranging.” This means that a radar device emits bursts of radio waves and picks up the radio wave reflections. The reflected radio waves are used to detect objects and find out how far away they are. Radio waves travel at the speed of light and can pass through clouds, so they can be used in all kinds of weather and at night. As it’s name suggests, RADARSAT is a satellite system that uses radar. The radio waves allow the satellite to look at features on land and on oceans. Bats also use radio waves to find food and avoid obstacles.
Through the I-STOP project (Integrated Satellite Tracking of Oil Polluters), RADARSAT scans for unusual spots on the water surface that may indicate oil spills. Technical experts examine images, an aircraft is sent to confirm the spill, identify the vessel, and gather evidence in support of possible future legal action. With readily available data from space, the enforcement work can be completed in hours.
Many industries benefit from RADARSAT images. Resources like oil, gas and minerals are found underground. Often surface features of the ground help scientists predict where these resources can be found. RADARSAT images are also used to plan for disaster relief for flooding and earthquakes. The images can also be used to predict wind and weather conditions to help people avoid danger.
Canada's satellite has many achievements to its credit. RADARSAT is the first satellite to have mapped the entire continent of Antarctica. This is a delicate and risky task. To obtain images of the icy continent, the satellite was rotated in orbit by remote commands, and then set back in its original orientation three weeks later. All credit goes to the ground team. Their ingenuity made these difficult manoeuvres a success.
http://www.thetech.org/exhibits/online/satellite/5/5.html
http://www.boeing.com/defense-space/space/bss/sat101.html
http://www.space.gc.ca/asc/eng/educators/resources/telecom/space_age/student_sheets.as
www.space.gc.ca/asc/eng/default.asp
ASTRONOMY COMMUNICATION ASSIGNMENT
SNC1D– 2007
Name: ______
1) Why do low Earth orbit satellite have to travel fast? How long does it take a low Earth orbit satellite to circle the earth?
2) RADARSAT sends radio wave signals to Earth and picks up the reflected waves. What are 3 advantages of using radio waves?
3) State one of the achievements of the RADARSAT.
4) How many Geostationary Earth Orbit Satellites are required to almost cover the globe?
5) How do satellites send information back to Earth?
6) What happens when a satellite gets out of position? What subsystem inside the satellite controls correct positioning of the satellite?
7) What types of signals are sent from Earth stations to the satellites?
8) Based on Figure 4 what types of signals has the Anik series of geosynchronous satellites provided?
9) What is the height of a GEO satellite?