Free PDF game aid.
From the publisher's website:
Every space campaign needs worlds - maybe hundreds of them! Sometimes a GM has something very specific in mind, and sometimes he's willing to let the dice decide. But whichever way you go (or even if you mix the two), GURPS Space's chapters on Basic and Advanced Worldbuilding (on pp. 62-133) take you through the process step by step.
Now e23 makes the job even easier with GURPS Space: Planetary Record and Worksheet, another free game aid! There are worksheets for every step of the worldbuilding process, and a ready-to-go Planetary Record Sheet at the end, waiting for the important data for your next space warlord's home planet, mysterious spawning ground of the enigmatic alien race, or maybe the perfect site for the newest colony. You can do it all with GURPS Space: Planetary Record and Worksheet. And did we mention it's free?