A Primary Pioneer Group is a possible Forerunner Naval fleet that searches for habitable planets. Advance Survey Team-Alpha is probably a smaller group of the Pioneers. A Primary Pioneer Group was sent to G617 g1 to observe the ecosystem of the planet, and it was there that they encountered the Flood, shortly after which they disappeared. Advance Survey Team-Alpha was sent shortly after to investigate their disappearance. A Primary Pioneer Group also led the Forerunners to the discovery of Earth, where the Portal to the Ark was built by the The Librarian as she was indexing all the creatures in the Galaxy.
- Primary Pioneer Group were the first Forerunners to be infected by the Flood.