  The first light instrument on the Thirty Meter Telescope (TMT) project will
be the InfraRed Imaging Spectrograph (IRIS). IRIS will be mounted on a bottom
port of the facility AO instrument NFIRAOS. IRIS will report guiding
information to the NFIRAOS through the On-Instrument Wavefront Sensor (OIWFS)
that is part of IRIS. This will be in a self-contained compartment of IRIS and
will provide three deployable wavefront sensor probe arms. This entire unit
will be rotated to provide field de-rotation. Currently in our preliminary
design stage our efforts have included: prototyping of the probe arm to
determine the accuracy of this critical component, handling cart design and
reviewing different types of glass for the atmospheric dispersion.
