We will discuss the design of a polarized atomic hydrogen jet target, combined with a polarimeter ("Breit-Rabi" polarimeter, BRP) that will measure the nuclear polarization of the atomic jet to 2% or better. This target is to be used for an absolute polarization measurement of the RHIC proton beams. This absolute measurement can be used in turn to calibrate a secondary polarimeter reaction. The status of the design work of the atomic-beam source (ABS) and the BRP will be presented.