  With continuous advances in related technologies, relativistic gravitational
experiments with orbiting gradiometers becomes feasible, which could naturally
be incorporated into future satellite gravity missions. Tests of Chern-Simons
modified gravity are meaningful since such a modification gives us insights
into (possible) parity-violations in gravitation. In this work, we derive, at
the post-Newtonian level, the new observables of secular gradients from the
non-dynamical Chern-Simons modified gravity, which will greatly improve the
constraint on the mass scale $M_{CS}$ that may be drawn from satellite
gradiometry measurements. For superconducting gradiometers, a strong bound
$M_{CS}\geq 10^{-7}\ eV$ could in principle be obtained. For future optical
gradiometers based on similar technologies from the LISA PathFinder mission, a
even stronger bound $M_{CS}\geq 10^{-6}\sim 10^{-5}\ eV$ might be expected.
