Why do radio astronomers worry about interference?
The radio signals arriving on Earth from astronomical objects are extremely weak — millions (or billions) of times weaker than the signals used by communication systems. For example, a cellular telephone located on the moon would produce a signal on earth that radio astronomers consider quite strong. Because the cosmic radio sources are so weak, they are easily masked by man-made interference. Possibly even worse than complete masking, weaker interfering signals can contaminate the data collected by radio telescopes, potentially leading astronomers to erroneous interpretations.
