I always get a little anxious when specific real-world events are attributed to Foundation activity, but in this case it seems like it could serve a useful purpose. Currently, though, it is not.
If you have two orbital satellites actively monitoring this anomaly at relatively close range, it seems like we should have more information about it than just the period of appearance and the quantity. I dig the concept, but without any hint as to just what kind of stuff is getting dumped (which, by extension, could suggest where it might be coming from), the execution isn't fully satisfying. See if you can expand upon it in that direction a little more- this one's got plenty of potential.
I do enjoy the idea of some nefarious cosmic polluter using a moon volcano as a landfill, though, so tentatively upvoted.