  High sensitivity differential atom interferometers are promising for
precision measurements in science frontiers in space, including gravity field
mapping for Earth science studies and gravitational wave detection. We propose
a new configuration of twin atom interferometers connected by a laser ranging
interferometer (LRI-AI) to provide precise information of the displacements
between the two AI reference mirrors and a means to phase-lock the two
independent interferometer lasers over long distances, thereby further
enhancing the feasibility of long baseline differential atom interferometers.
We show that a properly implemented LRI-AI can achieve equivalent functionality
to the conventional differential atom interferometer measurement system. LRI-AI
isolates the laser requirements for atom interferometers and for optical phase
readout between distant locations, thus enabling optimized allocation of
available laser power within a limited physical size and resource budget. A
unique aspect of LRI-AI also enables extended dynamic range of differential
signals and the highest possible effective data rate.
