Teacher Resources

Sounds from Space

This recording was taken via IRLP VHF radio link from NASA during a recent shuttle mission. The voices you can hear are mission control ( clearest & loudest), next clearest are astronauts in the International Space Station. The more muffled sounds are from the Astronauts in their space suits.
Listen carefully as they go through the check list for each task- In space, nothing is left to chance.

Satellite Details

Low Earth Orbit
This project is primarily aimed at low earth orbit satellites (also known as LEO satellites). These devices are launched in a polar orbit of between 650Km and 2500Km above the earth. Low earth orbit satellites have a smaller path loss because they are physically closer to the earth. This means that less power is required to send signals to the satellite and less sophisticated equipment is required to receive signals from the satellite.
There have been a number of instances where amateur operators have been able to set up satellite communications with a 5watt hand held radio and a directional yagi antenna. One of the most popular LEO satellites is ECHO or AMSAT OSCAR 51.




Low earth orbit satellites travel at very high speeds with maximum pass times for most parts of the earth being less than 15 minutes. They complete one orbit every 90 minutes.

Calculating the path loss is an interesting exercise for students as it demonstrates the inverse square law very effectively.


High Earth Orbit Satellites
High earth orbit or HEO satellites travel in orbits that are many thousands of Km above the earth. These orbits are normally elliptical which means that there will be a large difference between the apogee and the perigee of the satellite. While HEO satellites are more technically difficult to access, they do remain relatively stable in the sky for longer periods of time. These satellites are also capable of seeing very large amounts of the earth surface at one time. This makes them ideal for very long distance communication.
Using low powered satellites at great distances means that there is a high signal loss between the ground station and the satellite. Stations that use these satellites will have large, high gain antennas in order to maximise the signal received.
Have you ever wondered why there are different sized satellite dishes in use? Larger antennas have high gain which means that they can receive weaker signals. In Europe, satellite TV is transmitted with such a strong signal that an antenna a little bigger than a dinner plate will provide an acceptable signal.

Weather Satellites
There are a number of weather satellites orbiting the earth. These satellites take constant photos of the earth below them and transmit the back to earth. It is possible to track these NOAA satellites and even download and decode their signals.

International Space Station - How to Talk to the Astronauts

  • The international space station can be tracked as a class project either through the NASA website www.naga.gov or through the AMSAT satellite prediction page www.amsat.org Both sites list the international space station as ISS. All you will need is your latitude, longitude and altitude in order to accurately calculate the location of the station. On a clear evening, the station can be seen with a reasonable telescope. The satellite predictor will also provide details on where the ISS will rise and fall over the horizon and the amount of time it is visible. As the ISS is not on a polar orbit, it may take a few weeks before an orbit passes over you in the early evening.
  • The International Space Station is also equipped with an automatic packet radio transponder. This allows signals to be sent and received without the intervention of the crew.
  • ARISS is a joint project of NASA and AMSAT to provide the opportunity for school students to book time to speak with the crew of the International Space Station. As you can well imagine, crew time is very precious and schools who wish to be involved in the program will need to satisfy a number of necessary requirements. The ARISS program website is www.amsat.org/amsat-new/archive/catalog/ariss-cd/index.php
  • Resources for finding a local Amateur radio operator to assist you with your project can include contacting the Wireless Institute of Australia www.wia.org.au, or AMSAT www.amsat.org who may be able to assist you with operators who are located near your school.

Who Uses Morse Code Anyway?

  • Until recently, radio operators with licences that enabled international communications were required to pass tests in sending and receiving morse code. While these tests are no longer required, code demonstrations provide a valuable insight into the history of communications.
    Code generators are available on the web with some code practice sessions still broadcast on various radio frequencies.
  • If you have a licenced radio operator on staff, they may even be persuaded to provide a demonstration for your students.

Radio Facts

  • When morse code ( CW) is sent via radio, all the key is doing is turning the radio transmitter on and off. There is no tone transmitted, that is generated by the radio receiver.
  • The next time you receive an SMS text message on your phone, the default tone is the letters SMS spelt out in morse code.