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An accurate metrology system is required to stabilize the differential path lengths in the Nulling Interferometry Cryogenic Experiment (nice) to within 0.45nm peak-to-peak to achieve broadband mid-infrared nulls with long exposure times, which are required for potential future space missions, such as the Large Interferometer for Exoplanets (life) mission, that aim to directly image and characterize temperate terrestrial exoplanets. For this purpose, a differential heterodyne laser distance metrology is developed to enable differential path length measurements that are stable over multiple days with sub-nanometer accuracy at a bandwidth of 1 kHz. The system aims to solve several challenges that arise in the context of NICE, such as the need for long-term stability, the high intensity attenuation through the NICE beam path, and the requirement that the metrology be able to deliver low-latency feedback for closed-loop operation to compensate vibrations and drifts of the nulling testbed. The metrology uses a 633nm HeNe laser and operates at ambient temperature and pressure with a beat frequency of 10 kHz, which is generated by acousto-optic modulators. To improve long-term stability, the compact optical layout is optimized for low susceptibility to temperature variations. Over periods of 2 s, the intrinsic instability of the metrology is ≈ 80pm RMS when sampling at 10 kHz, and it is stable to within ≈ 0.5nm peak-to-peak for 2 hours. When correcting the distance measurements for the temperature of the metrology board, it is stable to within ≈ 1nm peak-to-peak for 14 hours. The metrology fulfils the stability and bandwidth requirements for nice for a duration of at least 2 hours. To achieve stability over even longer time periods, the metrology will later be placed in a temperature-controlled vacuum environment. ISSN:0277-786X

The Hi-5 instrument, a proposed high-contrast L' band (3.5-4.0 μm) nulling interferometer for the visitor focus of the Very Large Telescope Interferometer (VLTI), will characterize young extra-solar planetary systems and exozodiacal dust around nearby main-sequence stars. Thanks to VLTI's angular resolution (λ=B = 5 mas for the longest UT baseline), it will fill the gap between young giant exoplanets discovered by ongoing single-aperture direct imaging surveys and exoplanet populations discovered by radial velocity surveys. In this paper, we investigate the exoplanet detection yield of Hi-5. First, we present the latest catalog of stars identified as members of young stellar associations within 150 pc of the Sun thanks to the BANYAN algorithm and other searches for young moving group members. Realistic exoplanet populations are then generated around these stars and processed with the SCIFYsim tool, the end-to-end simulator for the Hi-5 instrument. Then, two formation models are used to estimate the giant planet's luminosity. The first is the New Generation Planetary Population Synthesis (NGPPS), also known as the Bern model, and the second is a statistical model based on gravitational instability (hot-start model - AMES-Dusty model). We show that Hi-5 is insensitive to cold-start planets but can detect giant hot-start planets. With ATs, more than 40 planets could be detected assuming 20 nights of observations. With its unique capabilities, Hi-5 is also able to constrain in mass the observed systems. Hi-5 is sensitive to planets with a mass > 2 Mjup around the snow line.