Question: How does the GBT ignore GPS signals? While visiting Green Bank this weekend (thank you!) we learned about several kinds of ground-sourced EM interference that can disrupt the reception of signals from space. How does the GBT manage to ignore orbital-sourced recurring signals, such as from GPS satellites? – Daniel
Answer: Radio astronomers do most of their measurements in frequency bands that are not used by orbital transmission sources like GPS. There are both national and international agreements which allocate chunks of frequency space exclusively to astronomy, while there are also frequency bands allocated to communications satellites. There are also less definite allocations of frequency space in which both astronomers and mainly ground-based communication services operate, which is a major source of terrestrial interference for radio astronomers.