Exploration rank - what works?

[Eriseley]

IIRC long range passenger missions give you exploration rank, but short don't. I can't remember what the limit is.

But who wants a whiny passenger onboard for three months? Shove that old bag out the airlock and go scan waterworlds, earthlikes and likely terraformable high metals.

Short definitely do. If the mission has the Explorer icon rather than the Trade icon, you get some Explorer rank based on credits earned. Transport (NOT sightsee) is Trade rank rather than Explorer. But any sightseeing gets you explorer rank.