  The InfraRed Imaging Spectrograph (IRIS) is a first light client science
instrument for the TMT observatory that operates as a client of the NFIRAOS
facility multi-conjugate adaptive optics system. This paper reports on the
concept study and baseline concept design of the On-Instrument WaveFront
Sensors (OIWFS) and NFIRAOS interface subsystems of the IRIS science
instrument, a collaborative effort by NRC-HIA, Caltech, and TMT AO and
Instrument teams. This includes work on system engineering, structural and
thermal design, sky coverage modeling, patrol geometry, probe optics and
mechanics design, camera design, and controls design.
