  SAGE (SagnAc interferometer for Gravitational wavE) is a fast track project
for a space observatory based on multiple 12-U CubeSats in geostationary orbit.
The objective of this project is to create a Sagnac interferometer with 73000
km circular arms. The geometry of the interferometer makes it especially
sensitive to circularly polarized gravitational waves at frequency close to 1
Hz. The nature of the Sagnac measurement makes it almost insensitive to
position error, allowing spacecrafts in ballistic trajectory. The light source
and recombination units of the interferometer are based on compact fibered
technologies, without the need of an optical bench. The main limitation would
come from non-gravitational acceleration of the spacecraft. However,
conditionally upon our ability to post-process the effect of solar wind, solar
pressure and thermal expansion, we would detect gravitational waves with
strains down to 10^-21 over a few days of observation.
