There a little cheat/glitch
If you hold down the right mouse button and move the crosshairs off the screen while still holding down the button, you can let go of the right mouse button and the satellite will continue firing as if the button is still being pressed. Then you just move the crosshairs around until the wave ends and then click the screen again to disengage it so you can upgrade/buy weapons from the shop. Then at the start of the wave, repeat the first steps again. Makes the game a little too easy, especially when you have the side mounted rocket pods maxed out.