  Direct imaging of Earth-like exoplanets requires high contrast imaging
capability and high angular resolution. Primary mirror segmentation is a key
technological solution for large-aperture telescopes because it opens the path
toward significantly increasing the angular resolution. The segments are kept
aligned by an active optics system that must reduce segment misalignments below
tens of nm RMS to achieve the high optical quality required for astronomical
science programs. The development of cophasing techniques is mandatory for the
next generation of space- and ground-based segmented telescopes, which both
share the need for increasing spatial resolution. We propose a new focal plane
cophasing sensor that exploits the scientific image of a coronagraphic
instrument to retrieve simultaneously piston and tip-tilt misalignments. The
self-coherent camera phasing sensor (SCC-PS) adequately combines the SCC
properties to segmented telescope architectures with adapted segment
misalignment estimators and image processing. An overview of the system
architecture, and a thorough performance and sensitivity analysis, including a
closed-loop efficiency, are presented by means of numerical simulations. The
SCC-PS estimates simultaneously piston and tip-tilt misalignments and corrects
them in closed-loop operation. The SCC-PS does not require any a priori on the
signal at the segment boundaries or any dedicated optical path. It has a
moderate sensitivity to misalignments, virtually none to pupil shear, and is
insensitive to segment gaps and edge effects. Primary mirror phasing can be
achieved with bright natural guide star. The SCC-PS is a noninvasive concept
and an efficient phasing sensor from the image domain. It is an attractive
candidate for segment cophasing at the instrument level or alternatively at the
telescope level, as usually envisioned in current space- and ground-based
observatories.
