^Refer to topic title.

I know that each PDS on a planet where an invasion is about to occur receives a pre-emptive strike at enemy GF, but I can't clarify from the rule book whether your PDS continue to fire at the invading enemy GF troops each combat round.

They do not. PDS:s can only fire into orbit and are strictly Surface to Air.

See Page 24 of the TI3 rule book regarding invasion combat.

PDS fire ( along with planetary bombardment) is resolved before combat between the GFs..

Then combat is resolved between surviving invading GFs and the surviving defending GFs. The PDSs do not fire in this part of the invasion combat.

A thematic way to explain why PDS:s can fire at GF before combat and not during is that they actually fire at the landing drop ships / drop pods / what have yous before they touch down.

I always liked that imagery as the fluff reason as to why.. It's the way I picture it in my head.

Thanks for your help guys =)