He knew, he even tried to get another ship to respond, acknowledging the situation. He's just following orders for this trip around the block, and could have even argued against them in private.

This dangerous energy ribbon comes by every 37 years, very close to Earth, but no one knew it was due for a visit? There are so many issues with that entire plot point, which others have pointed out, in part. I don't have a problem with the overall concept - it's sci-fi, after all - but the issues with how Kirk ends up in the Nexus are plentiful.