“no matter if it is DS or an area with planets.
Proviso: Planets/Stars/Asteroids block sensors, so some systems need more than 4 Sats to cover all the area.
I also think there's currently a bug/feature that unless you have an entity sharing sensors directly on the square with the planet/asteroid, the sensors do not cover that square.
I'll share it here again as it's somewhat relevant, and will also let you substitute sensor values for stations. Sensor Shadow/Power Calculator
Eventually I'll get around to making it actually work for multiple entities so all the power values are calculated properly.