Try to catch several planets in one scan if possible, to minimize the Reaper interest.
The radius is slightly smaller than then animation makes out so be sure to scan every inch. You’re able to scan simply by flying around space and hitting the appropriate key (displayed in the lower left of the screen). This Mass Effect 3 Planet Salvage And War Assets Guide will list all the available planets, as well as the things you may discover on each planet. Mass Effect 3 is filled with planets waiting to be discovered, some contain rare salvage such as credits and technology, others contain assets that are vital to your war effort.
