I'm writing a speculative story about aliens coming to earth, and just wanted to bounce a couple of ideas for scientific accuracy (or at least lack of obvious impossibility). This is set in the near future (~2050s) and it's more of a comic story so the details need not be exact.

If the alien ship jumps into the solar system (i.e. after superluminal flight) about 2 million kilometers from earth — what would pick it up first? I guess at certain point of time all big observatories will — how long might that take?

Another plot point is communication between the aliens being picked up by one guy (but not by the governments). It's something like this: there is a network of satellites used for providing internet connection, and the communication between the alien crafts caused interference with this in some areas (maybe due to the same frequencies? Ka band?) which our guy was able to pick up, isolate and decode — however, no official space agency did. Is that possible?

I don't have much background in radio communication - so apologies if these questions sound very amateurish.