  We propose a space-borne gravitational-wave detection scheme, called atom
interferometric gravitational-wave space observatory (AIGSO). It is motivated
by the progress in the atomic matter-wave interferometry, which solely utilizes
the standing light waves to split, deflect and recombine the atomic beam. Our
scheme consists of three drag-free satellites orbiting the Earth. The phase
shift of AIGSO is dominated by the Sagnac effect of gravitational-waves, which
is proportional to the area enclosed by the atom interferometer, the frequency
and amplitude of gravitational-waves. The scheme has a strain sensitivity $<
10^{-20}/\sqrt{{\rm Hz}}$ in the 100 mHz-10 Hz frequency range, which fills in
the detection gap between space-based and ground-based laser interferometric
detectors. Thus, our proposed AIGSO can be a good complementary detection
scheme to the space-borne laser interferometric schemes, such as LISA.
Considering the current status of relevant technology readiness, we expect our
AIGSO to be a promising candidate for the future space-based gravitational-wave
detection plan.
