Atom interferometry offers new perspectives for geophysics and inertial sensing. We present the industrial prototype of a quantum-based instrument: a compact, transportable, differential quantum gravimeter capable of measuring simultaneously the absolute values of both gravitational acceleration
g and its vertical gradient ${\mathrm{\ensuremath{\Gamma}}}_{zz}$. While the sensitivity to
g is competitive with the best industrial gravimeters, the sensitivity on ${\mathrm{\ensuremath{\Gamma}}}_{zz}$ reaches the limit set by quantum projection noise---leading to a long-term stability of
0.1E ($1\phantom{\rule{0.28em}{0ex}}\mathrm{E}=1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}\phantom{\rule{0.28em}{0ex}}{\mathrm{s}}^{\ensuremath{-}2}$). This dual-purpose instrument constitutes the industrial integration of cold atom sensors for practical applications. It paves the way for different applications in geophysics, civil engineering, and gravity-aided navigation, where accurate mapping of the gravitational field plays an important role.
In recent years, quantum technology has attracted attention in inertial navigation, especially due to its extreme sensitivity to inertial forces and strong immunity to drifts, which plague conventional sensors. There are multiple groups around the world working on cold atom interferometry aiming to develop high sensitive inertial sensors for very high accuracy autonomous navigation. Recent advancements in micro-fabrication technologies have helped in development of robust and miniaturized atom interferometry based high performance inertial systems. These, in future, will pave way for autonomous satellite inertial navigation sensors based on cold atoms. Here we discuss the achievements towards realizing cold atom inertial sensors and their indomitable role as inertial sensors for future satellites. A detailed survey on the initiatives taken by different space agencies, their achievements and their plans to explore its potential in space are also discussed.