Astronomy & Telescopes

Large Interferometer For Exoplanets (LIFE): VII. Practical implementation of a kernel-nulling beam combiner with a discussion on instrumental uncertainties and redundancy benefits

By Keith Cowing
astro-ph.IM
April 26, 2022
Filed under
Large Interferometer For Exoplanets (LIFE): VII. Practical implementation of a kernel-nulling beam combiner with a discussion on instrumental uncertainties and redundancy benefits
Schematic of a Kernel-5 beam combiner, based on the design of Guyon et al. (2013). Inputs V1 through V5 pass through five adaptive nuller units (AN), a series of ten beam splitter modules (C1 through C10) consisting of a beam splitter and phase shifting plate on one input, and four spatial filters (SF). The five outputs consist of one bright output W1 and four nulled outputs W2 through W4. Two shutters (S) can be used in case of a telescope failure (see Section 4).

Context: In the previous paper in this series, we identified that a pentagonal arrangement of five telescopes, using a kernel-nulling beam combiner, shows notable advantages for some important performance metrics for a space-based mid-infrared nulling interferometer over several other considered configurations for the detection of Earth-like exoplanets around solar-type stars.

Aims: We aim to produce a practical implementation of a kernel-nulling beam combiner for such a configuration, as well as a discussion of systematic and stochastic errors associated with the instrument.

Methods: We develop the mathematical framework around a beam-combiner based on a nulling combiner first suggested by Guyon et al. (2013), and then use it along with the simulator developed in the previous paper to identify the effects of systematic uncertainties.
Results: We find that errors in the beam combiner optics, systematic phase errors and the RMS fringe tracking errors result in instrument limited performance at ∼4-7 μm, and zodiacal limited at ≳10 μm. Assuming a beam splitter reflectance error of |ΔR|=5% and phase shift error of Δϕ=3 degrees, we find that the fringe tracking RMS should be kept to less than 3 nm in order to be photon limited, and the systematic piston error be less than 0.5 nm to be appropriately sensitive to planets with a contrast of 1×10−7 over a 4-19 μm bandpass. We also identify that the beam combiner design, with the inclusion of a well positioned shutter, provides an ability to produce robust kernel observables even if one or two collecting telescopes were to fail. The resulting four telescope combiner, when put into an X-array formation, results in a transmission map with an relative SNR equivalent to 80% of the fully functioning X-array combiner.

Jonah T. Hansen, Michael J. Ireland, Romain Laugier, the LIFE collaboration

Comments: 12 Pages, 14 Figures, 3 Tables. Submitted to A&A. Comments welcome! Other papers in the LIFE series are also available. First paper: arXiv:2101.07500, preceding paper: arXiv:2201.04891
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2204.12291 [astro-ph.IM] (or arXiv:2204.12291v1 [astro-ph.IM] for this version)
Submission history
From: Jonah Hansen
[v1] Tue, 26 Apr 2022 13:17:10 UTC (2,018 KB)
https://arxiv.org/abs/2204.12291
Astrobiology,

SpaceRef co-founder, Explorers Club Fellow, ex-NASA, Away Teams, Journalist, Space & Astrobiology, Lapsed climber.