Planetary system, star formation, and black hole science with non-redundant masking on space telescopes

Non-redundant masking (NRM) is a high contrast, high resolution technique relevant to future space missions concerned with extrasolar planetary system and star formation, as well as general high angular resolution galactic and extragalactic astronomy. NRM enables the highest angular resolution science possible given the telescope’s diameter and operating wavelength. It also provides precise information on a telescope’s optical state. NRM relies on its high quality self-calibration properties and the robustness of interferometric techniques, whereas coronagraphy requires exquisite wavefront quality. Stability during an observation sets fundamental NRM contrast limits. A non-redundant mask was recently added to JWST’s Fine Guidance Sensor Tunable Filter Imager (FGS-TFI) instrument, bringing a no-cost, no-impact boost in angular resolution that complements JWST’s coronagraphs. The JWST NRM search space lies between 50 and 400 mas at 3.8 to 5 m, even if the telescope’s image quality does not meet requirements. JWST’s NRM will produce 10 magnitudes of contrast in a 10 ks exposure on an M=7 star, placing Taurus protoplanets and nearby Jovians younger than 300 Myr within JWST’s reach. Future space telescopes can improve vastly on JWST’s NRM by utilizing more refined observing methods, and instrumentation designed to take full advantage of NRM’s high dynamic range. The ATLAST 16 m design can deliver 10 to 12 magnitudes of contrast between 0.7 to 6 mas at 0.1 m. On an 8 m telescope at 0.1 m NRM resolution is almost ten times finer than ALMA’s finest resolution. Polarization with space-based NRM opens new vistas of astrophysics in planetary system and star formation as well as AGNs and structure around galactic black hole candidates. Space NRM explores areas inaccessible to both JWST coronagraphs and future 30-m class ground-based telescopes. Ground-based NRM is limited by atmospheric variability. Optimization of space-based NRM requires consideration of flat fielding accuracy, target placement repeatability, charge diffusion, intrapixel sensitivity, image persistence, charge transfer efficiency, guiding, wavefront stability, pupil wander, and other details. We must assess NRM contrast limits realistically to understand the science yield of NRM in space, and, simultaneously, develop NRM science for planet and star formation and extragalactic science in the UV-NIR, to help steer high resolution space-based astronomy in the coming decade.