Large Interferometer For Exoplanets (LIFE)

[Context] The Large Interferometer For Exoplanets (LIFE) initiative is developing the science and a technology road map for an ambitious space mission featuring a space-based mid-infrared (MIR) nulling interferometer in order to detect the thermal emission of hundreds of exoplanets and characterize their atmospheres.
[Aims] In order to quantify the science potential of such a mission, in particular in the context of technical trade-offs, an instrument simulator is required. In addition, signal extraction algorithms are needed to verify that exoplanet properties (e.g., angular separation and spectral flux) contained in simulated exoplanet data sets can be accurately retrieved.
[Methods] We present LIFESIM, a software tool developed for simulating observations of exoplanetary systems with an MIR space-based nulling interferometer. It includes astrophysical noise sources (i.e., stellar leakage and thermal emission from local zodiacal and exozodiacal dust) and offers the flexibility to include instrumental noise terms in the future. Here, we provide some first quantitative limits on instrumental effects that would allow the measurements to remain in the fundamental noise limited regime. We demonstrate updated signal extraction approaches to validating signal-to-noise ratio (S/N) estimates from the simulator. Monte Carlo simulations are used to generate a mock survey of nearby terrestrial exoplanets and determine to which accuracy fundamental planet properties can be retrieved.
[Results] LIFESIM provides an accessible way to predict the expected S/N of future observations as a function of various key instrument and target parameters. The S/Ns of the extracted spectra are photon noise dominated, as expected from our current simulations. Signals from multi-planet systems can be reliably extracted. From single-epoch observations in our mock survey of small (R < 1.5 REarth) planets orbiting within the habitable zones of their stars, we find that typical uncertainties in the estimated effective temperature of the exoplanets are ≲10%, for the exoplanet radius ≲20%, and for the separation from the host star ≲2%. Signal-to-noise-ratio values obtained in the signal extraction process deviate by less than 10% from purely photon-counting statistics-based S/Ns.
[Conclusions] LIFESIM has been sufficiently well validated so that it can be shared with a broader community interested in quantifying various exoplanet science cases that a future space-based MIR nulling interferometer could address. Reliable signal extraction algorithms exist, and our results underline the power of the MIR wavelength range for deriving fundamental exoplanet properties from single-epoch observations.
This work has been carried out within the framework of the National Centre of Competence in Research PlanetS supported by the Swiss National Science Foundation. S.P.Q. acknowledges the financial support of the SNSF. TL was supported by the Simons Foundation (SCOL award No. 611576). This research has made use of the following Python packages: astropy (Astropy Collaboration 2013, 2018), matplotlib (Hunter 2007), numpy (Van Der Walt et al. 2011), scipy (Virtanen et al. 2020). Author contributions: M.O. and F.D. contributed equally to this paper. M.O. wrote the original LIFESIM tool, carried out the main analyses and wrote part of the manuscript. F.D. contributed to the main analyses and the LIFESIM tool, programmed the publicly available github version, led the instrumental noise analyses and wrote part of the manuscript. S.P.Q. initiated and guided this project and wrote part of the manuscript. R.L., E.F. and A.Gh. contributed to the LIFESIM tool. All authors discussed the results and commented on the manuscript. D.D. and R.L. acknowledge the support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement CoG-866070).