Maybe try leaving a beacon, flying to another planet, saving and returning?

Sometimes if you're a far enough distance away and you reload, it'll change the location of the objective markers. I've had a marker for a crashed freighter move to another planet in the system change multiple times.

I’m at the part of the mission where the scientist sends me to an observatory, however, when I arrive I can’t use the terminal I’m supposed to because I’ve already been sent here before and used it... Is there anything I can do besides warp to a new system and restart the mission? 

Scientific Research - Can’t Complete