The EXIST (Energetic X-ray Imaging Survey Telescope) mission includes the 1.1 m optical Infra-Red Telescope
(IRT) which provides the capability to locate, identify, and obtain spectra of transient events, in particular GRB
afterglows at redshifts up to epoch of reionization. The instrument includes a high spatial resolution imager, low
spectral resolution spectrometer (R~ 30) and high resolution slit spectrometer (R~ 3000). This instrument, with
the observatory's rapid reaction response will quickly identify the GRB afterglow, measure its brightness curves,
redshift, measure spectral characteristics of the afterglows and measure absorption spectra of the intervening
intergalactic medium. With this instrument, high redshift GRBs become important tools for studying the growth
of structure, observing the processes through which the universe is reionized.