Codes and Decodes: Or, How to Yell Across a Solar System
The transceiver in the movie sends the data through space using electromagnetic energy. One kind of electromagnetic energy is the light we see with our eyes. But there are many other forms of electromagnetic energy. One form is radio waves. We can't see radio waves, but we know how to make them and we know how to detect them. We also know how to make them carry messages. It is radio waves that bring you radio and TV!
Changing the shape of the radio waves to make them carry information is called "modulating" the wave. A radio wave that has been modulated to carry information is called a "signal." Now the wave is more than electromagnetic energy. It is a message!
(An FM signal has its frequency, or wavelength, modulated. An AM signal has its amplitude, or height, modulated. Spacecraft modulate the waveform in yet a different way, but we will save that explanation for another time! If you are curious, see our classroom activity article on the subject.)
It is the transceiver's job to convert an ordinary radio wave into one that carries a message.
Introducing Our Economy Model
Just like other electronics these days, transceivers are getting smaller, cheaper, and need less power. As part of NASA's New Millennium Program, space engineers are working on all kinds of ways to make spacecraft smaller, better, and less expensive to launch and operate.
Space Technology 5 (called ST5 for short) was a mission to make and test three very small spacecraft that would work together to study "space weather" in Earth orbit. They were smaller and much less expensive than spacecraft in the past, yet they could do all the same jobs.
One of their new, much smaller instruments was the transponder. A transponder is a transceiver and more. A transponder "bounces" a signal from Earth back to Earth, so that engineers can measure how far away the spacecraft is and how fast it is going.
Each transponder was about the size of five decks of cards stacked together, about 6 x 6 x 10 centimeters (2 x 2 x 4 inches) and weighed less than 500 grams (about 1 pound). They were nine times smaller and twelve times lighter than the transponders on other recent spacecraft. Each transponder needed much less power, too. Some of the technology used in this transponder comes from cell phone technology.
NASA hopes ST5's technologies will help future space missions work better, be less expensive, and help us discover even more wonderful and useful information about our environment of space.
Space Technology 5 (called ST5 for short) was a mission to make and test three very small spacecraft that would work together to study "space weather" in Earth orbit. They were smaller and much less expensive than spacecraft in the past, yet they could do all the same jobs. 
