Atpdec is an open source program that decodes images transmitted by POES NOAA weather satellite series.
These satellites transmit continuously, among other things, medium resolution images of the earth on 137Mhz.
These transmissions could be easily received with an inexpensive antenna and dedicated receiver.
For more information about receiving POES satellite images consult the rig site.
The output of the receiver, is an audio signal that could be recorded into a soundfile with any soundcard.
Atpdec will convert these sounfiles into .png images.
It accepts lots of soundfile format, but sampling frequency must be 11025Hz.
For each soundfile up to 5 different images could be generated :