I never had the Stellar Explorer (always wanted it), although I had almost all the other sets from that period. I actually had two of these plates back in the day, one came from a set of base plates you used to be able buy in a stand alone pack, and the other from this set
http://www.bricklink.com/catalogItem.asp?S=6980-1
Thanks again for the fantastic comments.
Quoting Marshall H
Spot on brilliant David! The working lift is fantastic. The control room operator looks like he's managing his post with efficiency. I totally dig the rock formation in the corner too. Your innovation skills are taking your builds to all new levels. I was looking forward to seeing this base. Wow! The base plate reminds me of the Stellar Explorer set that I had in '78, but I think at least 2 sets had that one back then. Keep it up man! :D