GROUP SIZE: Small
TIME: 3 45 minute periods
TYPE OF ACTIVITY: Student Investigation
TEACHING STRATEGY: Guided Discovery
CONCEPTS: Magnetic Field Tracking Frame of Reference
SKILLS: Observation Inference Recording Data Experimentation
Objectives: To help students understand the difficulty of conventional reference points in navigating in space; to understand how the earth’s magnetic field can be used to orient satellites in space; to illustrate how tracking stations can locate a satellite in space.
- For Activity 1 – The Problem – Thread or string, paper stars (stickers are easy); tape or tacks; shoe box; paper; pencil.
- For Activity 2 – The Solution – Bar magnet; dry cell battery; paper; light or bell; iron filings; compass; copper wire.
- For Activity 3 – Another Solution – Portable radio.
Teacher Background Information:
Tracking provides information by continuously reporting the location of a satellite, a probe that is going deep into interplanetary space, or of small rockets that will penetrate space on an up-down path of, perhaps, only a few hundred miles. Location is important for the scientist-experimenter because he/she has to know precisely where the spacecraft is at a particular point in time so an event measured by the spacecraft can be correlated, for example, to its position to the Sun, the Moon, or Earth. The scientist has to know its position to send it guidance information, to send it commands to make observations and to transmit data or change flight plans.
Long range rockets have guidance systems which work on the principle of comparing present position with point of destination. In traveling to the moon the astronauts have to navigate by using the Earth and the Moon as frames of reference. Tracking stations can also locate a satellite exactly.
The first activity should help to orient the pupils to the problems of space navigation.
- Before class, suspend thread from the top of the shoe box. Hang the paper stars on the end of the threads. Hang them in such a way as to take on the shape of the Big Dipper and place the cover on the box. Make several holes in the sides of the box for the students to look through. In addition, cut a hole for more light to enter the box in one end. (See illustration, top of next page.)
- Ask the students to look through one of the holes. In what position are the stars? Have students sketch their position on a piece of paper.
- Have the students move. What do they observe now? Re-sketch the stars.
- Why doesn’t the Dipper have its familiar shape when observed through the holes? Discuss the notion that when we travel in space the appearance of the constellations will be different. This will affect an astronaut’s bearings on direction when flights to the planets become a reality. Make certain students understand the appearance of the constellations in space depends upon the position that they are viewed from. (You can demonstrate the same thing by hanging string, with stars attached, from the ceiling of your classroom and having the students move about the room noting the difference in configuration from where they happen to be observing.)
- Encourage pupils to experiment with frames of reference such as: throwing the ball to someone who is running, plotting the paths of a child on a Ferris wheel as seen by friends on the ground, friends on the wheel and the child herself, etc.
- Have a student place a magnet under a piece of paper and sprinkle iron filings evenly over the paper.
- Have student gently tap the paper until the filings form a pattern over the magnet. Have another student hold a small compass over the pattern and observe where the needle points in relation to the lines of force. Where does it point? How does this help to orient a satellite? If we put a magnet in a small satellite near the earth, we could point it in outer space. How? To see how, set up the following apparatus: Attach a large dry cell battery (six volt) by a coiled copper wire to a light bulb or doorbell. Move a compass up to and through the coil to see where the needle points.
With a current loop around the base of a Tiros satellite, space scientists can point or orient it in outer space.
- Have a pupil turn on the transistor radio and tune it in on a station. Turn the radio around and listen to the strength of the signal received.
- Change the direction of the radio. Discuss the relationship between the location of the radio station and direction of the transistor radio. How are radio transmitters on a satellite used to aid in locating and tracking a satellite?
Extension: Have the students research the global system of tracking stations and communications networks. Have a “ham” radio operator in to tell the class about monitoring satellites and talking to astronauts in space.
Adapted from educational materials available from NASA Kennedy Space Center Teacher Resource Room