Design and commissioning of an In-Air Coronagraph Testbed in the HCIT facility at NASA's Jet Propulsion Laboratory

After completing its duty in the vacuum chamber at the High Contrast Imaging Testbed (HCIT) facility at NASA's Jet Propulsion Laboratory, the General Purpose Coronagraph Testbed (GPCT) has been retrofitted as the In-Air Coronagraph Testbed (IACT), with the purpose of verifying Boston Micromachines (BMC) 50x50 MEMS deformable mirrors (DM) performance by comparing the contrast achieved before and after random vibration testing. The testbed is configured as a vortex coronagraph, with one MEMS DM in the pupil plane to create a one-sided dark hole in monochromatic light. An environmentally isolating enclosure, based on the enclosure design previously used on Caltech's High Contrast Spectroscopy Testbed (HCST), minimizes air turbulence and other dynamic wavefront error sources. A smaller internal enclosure maintains the low relative humidity (<30%) necessary for safe operation of the MEMS DM. We expect this testbed to achieve 10(-8) contrast, and will use this contrast level as a baseline to assess survival or failure of MEMS DMs during vibration testing. In this presentation, we will present an overview of the design of the IACT, commissioning results, and plans for upcoming DM tests in preparation for launch of future space telescopes with coronagraph instruments.