Eugene Serabyn/Jet Propulsion Laboratory
The vortex coronagraph possesses all of the characteristics necessary for an affordable space-based high-contrast coronagraph aimed at the imaging and spectroscopy of exoplanets: simplicity, high throughput, the ability to observe very close to the star, and a clear 360 degree search space around the star. In this work, we therefore plan to advance vortex coronagraph performance to the level needed by an initial exoplanet-imaging space mission. Our primary goal is to test our vortex phase masks in the High Contrast Imaging Testbed (HCIT) facility to demonstrate the rejection of simulated starlight to better than the 10-9 level (with a goal of 10-10) over a 20% bandwidth. Our goal for the inner radius for these experiments is 2 λ/D. Ancillary to this overarching goal are a number of specific improvements at the device level (e.g., the phase masks, polarizers and waveplates) and the system level (e.g., the pointing and wavefront sensing approaches).
The HCIT tests will build off the PI's APRA-funded vortex mask development effort, by enabling access to and testing of our vortex masks at high-contrast in the unique HCIT facility, the funding of specific upgrades needed to enable vortex masks to reach very good broadband contrast, the modeling of our masks' performance in the full HCIT optical system, and system-level work that includes pointing stabilization on the center of the vortex, and the demonstration of vortex-specific pointing and wavefront sensing approaches.
We aim not only at demonstrations of deep, broadband starlight rejection at the level needed by an exoplanet mission, the core capability needed by any successful exoplanet coronagraph, but also at defining and simplifying the optical layout of potential space-based vortex coronagraphs through theoretical analysis, modeling, and demonstrations. In particular, a number of recent advances suggest that vortex coronagraphs are compatible with the use of affordable, small, on-axis, space-based telescopes. Likewise, vortex-specific pointing and wavefront-sensing configurations enable the direct measurement of the phases of focal-plane speckles using the science camera, thus simplifying wavefront measurements. Thus, we aim to combine targeted component improvements with system-level reconfigurations and tests to define a simplified coronagraphic system capable of meeting NASA's exoplanet mission needs.
Strategic Astrophysics Technology