A Satellite is a communications relay found in Encoded Emissions orbiting inhabited Earth-like Worlds and near installations. When scanned, it produces high-grade Encoded Materials, such as Specialised Legacy Firmware. To collect this data, it must be targeted and within the pilot's field of view, at which point the scanning process will automatically activate.
To find a satellite, orbit a planet at a distance between 6Mm - 10Mm at 10% - 20% throttle, and drop into any Encoded Emissions signal sources that appear. They are usually found near inhabited Earth-like Worlds. To verify that an Earth-like World is inhabited, check that the dark side of the planet for light sources on the surface.
Target a planet, get a decent orbit distance where your FSD max is 200km/s or more. For example, Earth can be orbited at 7.5Mm. Maintain the distance and circle the planet until an Unidentified Signal Source appears, and scan it to see if it is an Encoded Emissions signal source. Drop into normal space to scan the satellite.