  The Photo-z InfraRed Telescope (PIRT) is an instrument on the Gamow Explorer,
currently proposed for a NASA Astrophysics Medium Explorer. PIRT works in
tandem with a companion wide-field instrument, the Lobster Eye X-ray Telescope
(LEXT), that will identify x-ray transients likely to be associated with high
redshift gamma-ray bursts (GRBs) or electromagnetic counterparts to
gravitational wave (GW) events. After receiving an alert trigger from LEXT, the
spacecraft will slew to center the PIRT field of view on the transient source.
PIRT will then begin accumulating data simultaneously in five bands spanning
0.5 - 2.5 microns over a 10 arc-minute field of view. Each PIRT field will
contain many hundreds of sources, only one of which is associated with the LEXT
transient. PIRT will gather the necessary data in order to identify GRB sources
with redshift $z > 6$, with an expected source localization better than 1
arcsec. A near real-time link to the ground will allow timely follow-up as a
target of opportunity for large ground-based telescopes or the James Webb Space
Telescope (JWST). PIRT will also allow localization and characterization of GW
event counterparts. We discuss the instrument design, the on-board data
processing approach, and the expected performance of the system.
