Mission concept

LIFE is a space-based nulling interferometer inspired by older mission concepts such as ESA’s Darwin or NASA’s TPF-I . In contrast to the mid 2000s when those concepts were studied, we today have a much more comprehensive understanding of the existing exoplanet population, allowing for a much more robust quantification of science objectives, science requirements and expected science yield. To achieve the Science Objectives a space-based mission is required, avoiding the perturbing effects (turbulence and thermal background emission) of the Earth’s atmosphere. As detecting the thermal emission of temperate exoplanets requires observations at micrometer wavelengths – the thermal emission of Earth peaks around 10 micrometer – the current mission baseline foresees a nulling interferometer concept that provides the required spatial resolution, contrast performance and sensitivity for the direct detection of dozens of temperate terrestrial exoplanets. LIFE will consist of four formation flying collector telescopes – flying in a rectangular configuration tens to hundreds of meters apart – with an out-of-plane beam combiner spacecraft at their center. LIFE will take low-resolution spectra (R~100) between 4-18.5 micrometer wavelengths. The measurement principle is both simple and elegant: the instrument acts as a spectrograph from which the stellar flux is removed by destructive interference, while the signal from any orbiting planet is transmitted to the output of the instrument. This allows the nulling interferometer to observe exoplanets directly and build up signal-to-noise quickly without having to launch a very large, single aperture telescope. As we are finalizing the requirements for the mission, we are preparing for a concept study to look at the overall mission architecture and identify areas for additional technology development.

Ongoing Technology Development

NICE

We are developing and implementing NICE – the Nulling Interferometric Cryogenic Experiment for LIFE. The motivation of NICE is to build a lab-based nulling testbed to enhance the technology readiness level of broadband nulling interferometry. The long term goal of NICE is to demonstrate the required nulling performance of LIFE in terms of starlight suppression and stability under cryogenic conditions and with flux levels similar to those from real astrophysical sources. Details about NICE can be found here.

Waveguides and integrated optics

In early 2024 we started a collaboration at ETH Zürich to develop waveguides and integrated photonic chips that could replace some of the bulk optics for the mission. Key challenges are the high throughput we require combined with the somewhat large mid-infrared wavelength range.

Detectors

Given the low photon rates we are expecting from distant temperate terrestrial exoplanets, having a low-noise, stable, high-efficiency detector for the whole LIFE wavelength range is important. In 2023 our team members at SRON in the Netherland started looking into MKIDs for mid-infrared applications and received a grant in 2024 to work on this more systematically.

Piezo-electric DMs

Floris van der Tak (SRON) & Tim Lichtenberg (U Groningen) have obtained funding for technical and system work for the optics of LIFE. The project includes a detailed optical design for LIFE, comparing various array configurations, and leading to tolerances on the quality of the various optical components. Additionally, existing work on hysteretic deformable mirrors based on piezo-electric actuators will be extended and tested at cryogenic temperatures, which is essential for wavefront correction. The work will be carried out at the optical-infrared laboratory of the Netherlands Research School for Astronomy (NOVA) in Dwingeloo, in collaboration with the Netherlands Institute for Space Research (SRON) in Groningen and the LIFE team at ETH Zürich.

Compact Delay Line for Space Interferometry

PI Leonid Pogorelyuk (RPI), and Co-I’s Kerri Cahoy (MIT), John Monnier (UMichigan), and Michael Shao (JPL) won a NASA-funded grant for a LIFE related technology project starting in September 2024. The “Compact Delay Line for Space Interferometry” project will demonstrate a 5 m delay line that fits within a 2U (20 cm x 10 cm) envelope and can be controlled with 20 nm precision by four piezo-actuated mirrors. Long delay lines can reduce the complexity of formation-flying space interferometers, especially when it comes to the number of satellites in a (LIFE) precursor mission.