  The Swift Gamma-ray Burst (GRB) observatory responds to GRB triggers with
optical observations in ~ 100 s, but cannot respond faster than ~ 60 s. While
some ground-based telescopes respond quickly, the number of sub-60 s detections
remains small. In mid- to late-2013, the Ultra-Fast Flash
Observatory-Pathfinder is to be launched on the Lomonosov spacecraft to
investigate early optical GRB emission. This pathfinder mission is necessarily
limited in sensitivity and event rate; here we discuss a next generation
rapid-response space observatory. We list science topics motivating our
instruments, those that require rapid optical-IR GRB response, including: A
survey of GRB rise shapes/times, measurements of optical bulk Lorentz factors,
investigation of magnetic dominated (vs. non-magnetic) jet models, internal vs.
external shock origin of prompt optical emission, the use of GRBs for
cosmology, and dust evaporation in the GRB environment. We also address the
impacts of the characteristics of GRB observing on our instrument and
observatory design. We describe our instrument designs and choices for a next
generation observatory as a second instrument on a low-earth orbit spacecraft,
with a 120 kg instrument mass budget. Restricted to relatively modest mass and
power, we find that a coded mask X-ray camera with 1024 cm2 of detector area
could rapidly locate about 64 GRB triggers/year. Responding to the locations
from the X-ray camera, a 30 cm aperture telescope with a beam-steering system
for rapid (~ 1 s) response and a near-IR camera should detect ~ 29 GRB, given
Swift GRB properties. Am additional optical camera would give a broadband
optical-IR slope, allowing dynamic measurement of dust extinction at the
source, for the first time.
