  The Astrometric Gravitation Probe mission is a modern version of the 1919
Dyson-Eddington-Davidson experiment, based on a space-borne telescope with a
permanent built-in eclipse, provided by a coronagraphic system. The expected
improvement on experimental bounds to General Relativity and competing
gravitation theories is by at least two orders of magnitude. The measurement
principle is reviewed, in particular the principle of Fizeau-like combination
of a set of individual inverted coronagraphs simultaneously feeding a common
high resolution telescope. Also, the payload has a dual field of view property,
in order to support simultaneous observations of stellar fields either very
close, or far away, from the Sun, i.e. fields affected by either high or low
light bending. We discuss a set of solutions introduced in the optical design
to improve on technical feasibility and robustness of the optical performance
against perturbations, in particular induced by manufacturing and alignment
tolerances, and launch stresses.
