How does NASA communicate with spacecraft?
All deep space vehicles are equipped with radio transmitters and receivers for sending radio signals to and from Earth-based stations. These signals are generated at pre-established frequencies. The problem is that there are lots of other things, both natural and human-made, that create background radio signals that mix in with the spacecraft signals. The ratio of the power of the spacecraft's signal level to the level coming from other sources is known as the signal-to-noise ratio (SNR).
"Noise" is just another name for any unwanted interference with a radio signal. You've most likely had experience with radio noise without even knowing it---you see static on your television or hear it on your radio because of interference. When dealing with deep space transmissions like those DS1 is performing, there are many sources of noise, most of those much "louder" (i.e. a stronger signal) than DS1's small transmitter. Radio astronomers have to separate the satellite's radio signal from the rest of the noise, and almost everything in space is producing some noise. Some of the strongest sources of noise include the Sun, pulsars, quasars, radio galaxies, and nebulas.
What could go wrong with communications?
What are radio waves?
How long does it take for transmissions to get between DS1 and Earth?
What is energy?
How are gaps in data dealt with?
What problems are there besides noise?
Why does communication get harder at greater distances?
What role does the Sun play in space missions like DS1's?