Large Interferometer For Exoplanets (LIFE): XI. Phase-space synthesis decomposition for planet detection and characterization (2308.01478v1)

Abstract: A mid-infrared nulling-space interferometer is a promising way to characterize thermal light from habitable planet candidates around Sun-like stars. However, one of the main challenges for achieving this ambitious goal is a high-precision stability of the optical path difference (OPD) and amplitude over a few days for planet detection and up to a few weeks for in-depth characterization. Here we propose a new method called phase-space synthesis decomposition (PSSD) to shorten the stability requirement to minutes, significantly relaxing the technological challenges of the mission. Focusing on what exactly modulates the planet signal in the presence of the stellar leak and systematic error, PSSD prioritizes the modulation of the signals along the wavelength domain rather than baseline rotation. Modulation along the wavelength domain allows us to extract source positions in parallel to the baseline vector for each exposure. The sum of the one-dimensional data converts into two-dimensional information. Based on the reconstructed image, we construct a continuous equation and extract the spectra through the singular value decomposition (SVD) while efficiently separating them from a long-term systematic stellar leak. We performed numerical simulations to investigate the feasibility of PSSD for the LIFE mission concept. We confirm that multiple terrestrial planets in the habitable zone around a Sun-like star at 10 pc can be detected and characterized despite high levels and long durations of systematic noise. We also find that PSSD is more robust against a sparse sampling of the array rotation compared to purely rotation-based signal extraction. Using PSSD as signal extraction method significantly relaxes the technical requirements on signal stability and further increases the feasibility of the LIFE mission.

• The paper presents an innovative PSSD method that reduces interferometric stability requirements from days to minutes for exoplanet detection.
• It employs singular value decomposition to effectively isolate planetary spectra from systematic stellar noise in simulation tests.
• PSSD's relaxed optical path difference and amplitude demands significantly improve the feasibility of the LIFE mission for exoplanet characterization.

Phase-space Synthesis Decomposition for Exoplanet Detection and Characterization

The paper under review introduces a novel methodological approach referred to as phase-space synthesis decomposition (PSSD), designed to address challenges in detecting and characterizing exoplanets with a mid-infrared nulling interferometer. This instrument is central to the Large Interferometer For Exoplanets (LIFE) mission, which aims to characterize exoplanets around Sun-like stars by analyzing thermal emissions. Specifically, PSSD seeks to improve upon current techniques by relaxing the stringent stability requirements typically imposed on interferometric observations, focusing on the wavelength domain and employing an advanced signal-extraction methodology.

Methodological Advancements

The authors propose PSSD as a solution to mitigate the technological constraints associated with the optical path difference (OPD) and amplitude stability necessary for exoplanet detection and characterization. Traditional approaches demand stability maintaining over days to weeks; however, PSSD reduces this time frame to mere minutes. This relaxation eases technical requirements and makes the LIFE mission more feasible.

PSSD distinguishes itself by prioritizing signal modulation in the wavelength domain over baseline rotation. This prioritization permits the extraction of spatial information in parallel with the baseline vector, transforming one-dimensional data into two-dimensional insight. By employing singular value decomposition (SVD), the method efficiently disentangles planetary spectra from long-term systematic stellar leakages. This capability is rigorously tested through numerical simulations configured around scenarios with multiple terrestrial planets.

Numerical Validation

Simulations affirm PSSD's robustness. The method successfully identifies multiple terrestrial planets within the habitable zone of a nearby Sun-like star located 10 parsecs away, even amidst significant systematic noise. Notably, PSSD's resilience to sparse array rotations affords it an advantage over more traditional rotation-dependent signal extraction techniques.

Practical and Theoretical Implications

From a practical standpoint, PSSD's reduction in stability requirements significantly enhances the operational feasibility of missions like LIFE. By relaxing OPD precision needs, the method alleviates the constraints on formation flight complexities and optical system stability. This advancement could reduce technological costs and make space-based nulling interferometers more accessible for exoplanetary research.

Theoretically, PSSD's strategy of decomposing signals in the phase-space rather than relying solely on transmission patterns opens new pathways for refining signal extraction processes. SVD-based spectral decomposition is particularly promising for isolating planetary signals amidst extraneous stellar noise, potentially setting a precedent for future signal processing algorithms in astrophysical instrumentation.

Future Outlook

Prospective applications of PSSD involve extending its principles to encompass diverse interferometric configurations and broader wavelength domains, potentially improving the detection capabilities for more varied planetary systems. The LIFE mission could thereby characterize a significant portion of terrestrial exoplanets around all types of stellar masses. With such potential developments, further advancements in AI and algorithmic methodologies could further increase the sensitivity and specificity of exoplanet detection and characterization.

In conclusion, this paper presents a comprehensive approach to overcoming key observational challenges in exoplanet detection through PSSD, offering innovative solutions with significant implications for the future of exoplanetary science and observational astronomy.