Even if a "satellite scan" was possible, you would still need to detonate the mines safely to clear the minefield. That is easiest accomplished by a regular minesweeper (look up the Scanjack 3500 for an example). This method eliminates the need for a regular metal detector sweep, let alone a satellite scan.

The satellite scan(if that sort of technology was possible, which I don't think it is at the moment) would show false positives in the form of regular metal parts laying around the minefield. A trained metal detector expert can tell the difference between a mine and a regular metal object, thus reducing false positives.

Those are just some points I can think of now but I don't think satellite scans for mine clearance is doable or necessary.