The post-boost vehicle
) describes, in general terms, a complex, exoatmospheric maneuverable
object that is used to position and deploy
the reentry vehicle
), anti-ballistic missile countermeasure
packages and other associated object
The PBV typically resides at the top of a ballistic missile, and is jettisoned by the final stage after burnout. Any number of RVs may be attached to a PBV depending on the particular missile system. The PBV contains guidance, control and thruster hardware that allows it to reorient and move in three-dimensions while it flies along its ballistic arc. This allows it to deploy the RVs in a very precise (and typically covert) manner, and place whatever countermeasures it might have aboard to obscure the RV from any possible anti-missile system.
A PBV is different than an attitude control module (ACM), which typically contains only the smarts to reorient itself during flight, not move around.