Looking for a game name (I have no idea)

It's been about 15 years, I guess. I played that game on my Amiga 500. Ok:

It was an action-game. There was a map from space with about 10-20 planets. Each had a different size, colour and name. When you chose a planet the screen changed into 3D-perspective, poor graphics though. You had a crosshair to shoot down... stuff that moved towards you (your ship, respectively). Maybe it was some kind of planetary defense system (rockets) or asteroids. I don't know if there was any cockpit.
If you had destroyed enough "objects" or time was over (not sure again) you got onto the planet, 2D again. You saw the surface of the planet... which was a city I think. It looked all alike if I remember correctly. Only the colour of the city might have varied from planet to planet. You had a space ship with a single gun. You could fly in any direction and the screen moved along. There also was a round slow moving... thing on the screen. I thing it was your mothership. However, as long as your ship stayed within this thing you were invulnerable.
Your task was to find and destroy rockets that were about to start from pits on the surface of the planet. Of course, there was something to prevent you from doing this. The only thing I can remember is that there were flying objects which destroyed or damaged your ship.
I hope some of you remember the name of this game! I really don't! Sorry for my poor english and thanks for you help!


***edit:***

I found it on my own. The name of the game is PIONEER PLAGUE.

[Hanzu]

Nice description. I imagined the screen with four monitors and some sort of window to present cockpit.

https://amiga.abime.net/screen/1001-...n3.png?v=36216