Can you put the obstacles in any order or it must be first asteroids, then debris and finally the station.

In any order. No order is listed only that the 6 Obstacles must be placed (3 Asteroids, 2 Debris, One Station)

Only Contested Outpost changes that, stating that the Outpost is hung on to, to be placed last.

Thanks!

There are some strategies to obstacle placement. I will be making a video when I have time on these.