Can anyone direct me to a thread about trade skills? in the book it says they allow characters to craft things or earn extra profit factor for the group. Some seem more obvious than others, shipwright and armourer for example, but how would trade archaeologist or explorator or remembrancer factor in?

You can get some inspiration from Dark Heresy Inquisitor's Handbook: sections "Expanded Skills" &"Crafting". Although DH is another game and skill sets do not exactly coincide , they are quite similar.

Not all of them might factor in, in a direct way.

With remembrance I can't think of an example that would directly yield PF. However the party could be in a situation when they have to use it (to remember something). For example: if they successful on the test it could make negotiations easier (by remembering some local custom, or recall what was in the tent of the head of the village and therefore bringing some gifts to liking); or if they have to break into somewhere they can try to remember the layout and that makes it easier to avoid guards (and give some bonus to subsequent hide tests) and to get in and out faster
Archeology: is useful when building a dig site above ancient Eldar ruins, or whatever. They have to know where to dig, how to dig, making tunnels, and how to retrieve and then clean up and make readable an old piece of stone with unknown language written on it. If you don't want to play it out, you can always just have them roll a test when they are colonizing or visiting a world, and if they are successful you can give them some achievement points or a PF. If they don't have the skill then they wouldn't have the option to do so.

Explorator: A standard scrutny + detection scan could reveal planetary bodies or ships in a system, but if you want to do a thorough search, look for a space hulk or an asteroid with precious minerals on it, you have to do it in a specific (topologycal) manner to be efficient. With trade(explorator) they can find something that they otherwise wouldn't be able to, or they can reduce search time for an emergency pod significantly (from months to weeks, etc)

thanks zolik. very helpful