  We are now investigating and studying a small satellite mission HiZ-GUNDAM
for future observation of gamma-ray bursts (GRBs). The mission concept is to
probe "the end of dark ages and the dawn of formation of astronomical objects",
i.e. the physical condition of early universe beyond the redshift z > 7. We
will consider two kinds of mission payloads, (1) wide field X-ray imaging
detectors for GRB discovery, and (2) a near infrared telescope with 30 cm in
diameter to select the high-z GRB candidates effectively. In this paper, we
explain some requirements to promote the GRB cosmology based on the past
observations, and also introduce the mission concept of HiZ-GUNDAM and basic
development of X-ray imaging detectors.
