Large Interferometer For Exoplanets (LIFE)

Abstract

Context. In the fourth 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 physical 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 developed a mathematical framework around a nulling beam combiner, and then used it along with a space interferometry simulator to identify the effects of systematic uncertainties. Results. We find that errors in the beam combiner optics, systematic phase errors and the root-mean-squared (RMS) fringe tracking errors result in instrument-limited performance at ∼4-7 µm, and zodiacal light limited at ≳10 µm. Assuming a beam splitter reflectance error of |∆R| = 5% and phase shift error of ∆ϕ = 3 • , we find that the fringe tracking RMS error 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 fourtelescope combiner, when put into an X-array formation, results in a transmission map with a relative signal-to-noise ratio equivalent to 80% of a fully functioning X-array combiner. Conclusions. The advantage in sensitivity and planet yield of the Kernel-5 nulling architecture, along with an inbuilt contingency option for a failed collector telescope, leads us to recommend this architecture be adopted for further study for the LIFE mission.

Large Interferometer For Exoplanets (LIFE)

“…However, stellar leak is more sensitive to the optical path difference (OPD) and low-order aberrations in the second-order null than in the fourth-order null (e.g., Hansen et al 2023a). Initially, Lay (2004) quantified the systematic errors generated from the fluctuation of the null depth, which could obscure the modulated planetary signal over the baseline rotation.…”