Habroxia 2 (HP)

On the very first level, at the very start of the level you have an open area above you and a closed off area at the bottom of the screen, blocked by large rocks. Immediately fly to the bottom of the screen, shoot the rocks there and collect the Astronaut that was trapped there.

The rocks at the end of this passage often yield good rewards I find as well, so I take this route most runs.