# Large Interferometer For Exoplanets (LIFE): II. Signal simulation, signal extraction and fundamental exoplanet parameters from single epoch observations

**Authors:** Felix Dannert, Maurice Ottiger, Sascha P. Quanz, Romain Laugier, Emile Fontanet, Adrian Gheorghe, Olivier Absil, Colin Dandumont, Denis Defrère, Carlos Gascón, Adrian M. Glauser, Jens Kammerer, Tim Lichtenberg, Hendrik Linz, Jerôme Loicq, the LIFE collaboration  
**arXiv:** [2203.00471](https://arxiv.org/abs/2203.00471)  
**Date:** 2022-03-01  
**Summary page:** https://www.summarizepaper.com/en/paper/2203.00471v1/

## Key points

- The Large Interferometer for Exoplanets (LIFE) initiative is developing a technology roadmap and science plan for a space-based mid-infrared (MIR) nulling interferometer that can detect the thermal emission of hundreds of exoplanets and characterize their atmospheres.
- The LIFEsim software tool has been developed to simulate observations of exoplanetary systems with an MIR space-based nulling interferometer, including astrophysical noise sources such as stellar leakage and thermal emission from local zodiacal and exo-zodiacal dust.
- The Flasseur et al. (2020) detection criterion method allows us to derive a detection criterion combining measurements at multiple wavelengths with uncorrelated noise on the basis of the cost function for direct imaging methods.
- The dominant background noise in the modulated signal propagates as a linear combination to the SNR maps, meaning that in the absence of point sources, the distribution of SNR values over a large enough field-of-view also follows a normal distribution.
- From single epoch observations in a mock survey of small ($R < 1.5 R_\mathrm{Earth}$) planets orbiting within the habitable zones of their stars, typical uncertainties in estimated effective temperature are $\lesssim$10\%, for exoplanet radius $\lesssim$20\%, and for separation from the host star $\lesssim$2\%.
- SNR values obtained in the signal extraction process deviate less than 10\% from purely photon-counting statistics based SNRs.
- These findings demonstrate the potential for LIFEsim to accurately predict exoplanetary system properties and inform future space-based MIR nulling interferometer missions.

## Summary

The Large Interferometer for Exoplanets (LIFE) initiative is developing a technology roadmap and science plan for a space-based mid-infrared (MIR) nulling interferometer that can detect the thermal emission of hundreds of exoplanets and characterize their atmospheres. To quantify the potential of such a mission, an instrument simulator is required, along with signal extraction algorithms to verify that exoplanet properties can be accurately retrieved from simulated datasets. The LIFEsim software tool has been developed to simulate observations of exoplanetary systems with an MIR space-based nulling interferometer, including astrophysical noise sources such as stellar leakage and thermal emission from local zodiacal and exo-zodiacal dust. It also provides an accessible way to predict the expected signal-to-noise ratio (SNR) of future observations based on various instrument and target parameters. The extracted spectra are photon-noise dominated, as expected from current simulations. The Flasseur et al. (2020) detection criterion method allows us to derive a detection criterion combining measurements at multiple wavelengths with uncorrelated noise on the basis of the cost function for direct imaging methods. With some modifications, this approach can also be applied to nulling interferometry. The dominant background noise in the modulated signal propagates as a linear combination to the SNR maps, meaning that in the absence of point sources, the distribution of SNR values over a large enough field-of-view also follows a normal distribution. Thus, the random values of the combined cost function J′ map are expected to follow a χ2-distribution with L degrees of freedom, where L is the number of wavelength bins. The maximum-likelihood method has been used to estimate exoplanet parameters from simulated data sets. From single epoch observations in a mock survey of small ($R < 1.5 R_\mathrm{Earth}$) planets orbiting within the habitable zones of their stars, typical uncertainties in estimated effective temperature are $\lesssim$10\%, for exoplanet radius $\lesssim$20\%, and for separation from the host star $\lesssim$2\%. SNR values obtained in the signal extraction process deviate less than 10\% from purely photon-counting statistics based SNRs. These findings demonstrate the potential for LIFEsim to accurately predict exoplanetary system properties and inform future space-based MIR nulling interferometer missions.