This is the mission to scan 3 planets for ship parts.

You need to go to your core planet build screen at the bottom left where the construct shipyard button is/was there will be a blue icon if I recall the color correctly you need to activate it in your queue. Go to 2 other planets or colonize 2 more and add the same button to their queues. 

When these are "built/scanned" you will have a ship in your shipyard choices to build once only. Pop ups will appear for each of the three "scans".