You can download the game from Automation disk 14(ftp://ftp.cs.tu-berlin.de/pub/atari/games/Automation/A_014.ST).
You can see Power Pack instructions from http://www.geocities.com/yotisrx7/PowerPack.html#StarGoose.
God I loved this game. I got it as part of my "Power Pack" for Christmas. I remember shooting the turrets and was always dead impressed by that opening animation of the mothership dropping your "buggy". Collecting the Gems ... oh how I wish I hadn't sold my 520STfm! I can still imagine playing this with my Powerplay cruiser in hand on a Saturday if I close my eyes...
Oh how I wish my 520STe still lived!!
I was only about 7 at the time but I adored that game!
I vaguely recall going through the different coloured tunnels to refuel etc.
Awwww, I want it all back!
The best oft his game is the 3D effect on the playfield. The game is somewhat easy to master and it lacks new types of enemies on further levels.
However addictive enough for a few nice hours of play.
There are games for the ST that are much more crap than this one.