This card's effect and name suggest that, each turn, this monster collects solar power or some similar form of energy, and then releases this energy in some form of laser when it attacks.
As the anime suggests, this monster is a Satellite, and so is floating in outer space. This is why only high Level monsters can attack it, because otherwise it is out of range from enemy attacks.
An interesting note is its anime effect is stronger than its card effect but it has a bigger weakness to compensate for it, a trait rare in anime effects. It can't be destroyed by battle by a Level 7 or lower monster and battle damage is negated. In exchange if it is attacked by a Level 8 or higher monster, its ATK becomes 0. In the actual game, it doesn't negate damage if it's not destroyed, but its ATK doesn't become 0 either.
In a 40 card Duel, there are 34 End Phases (unless the size of the Deck changes). That means the ATK of "Satelite Cannon" can be at most 34,000.