Tolerance analysis of a self-coherent camera for wavefront sensing and dark hole maintenance

Exceptional wavefront correction is required for coronagraphs on future space observatories to reach 10(-10) contrasts for direct imaging of rocky exoplanets around Sun-like stars. This picometer level wavefront correction must be stable over long periods of time and should be limited only by photon noise and wavefront sensing architecture. Thus, wavefront errors that arise from optical surface errors, thermal gradients, pointing induced beamwalk, and polarization aberration must be tightly controlled. A self-coherent camera (SCC) allows for image plane correction of mid-spatial frequency errors and a continuous means of dark-hole maintenance. By introducing a reference pinhole at the Lyot stop of a coronagraph, coherent starlight can be interfered with image plane speckles while leaving incoherent planet light untouched. A coronagraph model was created using High Contrast Imaging in Python (HCIPy) to simulate the SCC. Using these tools, realistic input disturbances can be introduced to analyze wavefront sensor performance. Using our model, we first demonstrate the necessity of a complimentary low-order wavefront sensor (LOWFS) to be paired with the SCC. Next, we discuss considerations when creating the modified Lyot stop of an SCC. Finally, a tolerance analysis of the SCC in the presence of optical surface errors, beamwalk due to pointing errors, photon noise, and detector read noise is presented.