The Large Binocular Telescope Interferometer (LBTI) enables nulling interferometric observations across the N band (8 to 13 µm) to suppress a star's bright light and probe for faint circumstellar emission. We present and statistically analyze the results from the LBTI/HOSTS (Hunt for Observable Signatures of Terrestrial Systems) survey for exozodiacal dust. By comparing our measurements to model predictions based on the Solar zodiacal dust in the N band, we estimate a 1 σ median sensitivity of 23 zodis for early type stars and 48 zodis for Sun-like stars, where 1 zodi is the surface density of habitable zone (HZ) dust in the Solar system. Of the 38 stars observed, 10 show significant excess. A clear correlation of our detections with the presence of cold dust in the systems was found, but none with the stellar spectral type or age. The majority of Sun-like stars have relatively low HZ dust levels (best-fit median: 3 zodis, 1 σ upper limit: 9 zodis, 95% confidence: 27 zodis based on our N band measurements), while ∼20% are significantly more dusty. The Solar system's HZ dust content is consistent with being typical. Our median HZ dust level would not be a major limitation to the direct imaging search for Earth-like exoplanets, but more precise constraints are still required, in particular

The achievement of µarcsec relative astrometry with ground-based, near infrared, extremely large telescopes requires a significant endeavour of calibration strategies. In this paper we address the removal of instrument optical distortions coming from the ELT first light instrument MICADO and its adaptive optics system MAORY by means of an astrometric calibration mask. The results of the test campaign on a prototype mask (scale 1:2) has probed the manufacturing precision down to ∼ 50nm/1mm scale, leading to a relative precision δσ ∼ 5e − 5. The assessed manufacturing precision indicates that an astrometric relative precision of δσ ∼ 5e − 5 = 50µas 1ar csec is in principle achievable, disclosing µarcsec near infrared astrometry behind an extremely large telescope. The impact of ∼ 10-100 nm error residuals on the mask pinholes position is tolerable at a calibration level as confirmed by ray tracing simulations of realistic MICADO distortion patterns affected by mid spatial frequencies residuals. We demonstrated that the MICADO astrometric precision of 50 µas is achievable also in presence of a mid spatial frequencies pattern and manufacturing errors of the WAM by fitting the distorted WAM pattern seen through the instrument with a 10 th order Legendre polynomial.

Characterisation of atmospheric optical turbulence is crucial for the design and operation of modern ground–based optical telescopes. In particular, the effective application of adaptive optics correction on large and extremely large telescopes relies on a detailed knowledge of the prevailing atmospheric conditions, including the vertical profile of the optical turbulence strength and the atmospheric coherence timescale. The Differential Image Motion Monitor (DIMM) has been employed as a facility seeing monitor at many astronomical observing sites across the world for several decades, providing a reliable estimate of the seeing angle. Here we present the Shack–Hartmann Image Motion Monitor (SHIMM), is a development of the DIMM instrument, in that it exploits differential image motion measurements of bright target stars. However, the SHIMM employs a Shack-Hartmann wavefront sensor in place of the two–hole aperture mask utilised by the DIMM. This allows the SHIMM to provide an estimate of the seeing, unbiased by shot noise or scintillation effects. The SHIMM also produces a low–resolution (three–layer) measure of the vertical turbulence profile, as well as an estimate of the coherence timescale. The SHIMM is designed as a low-cost, portable, instrument. It is comprised of off-the-shelf components so that it is easy to duplicate and well–suited for comparisons of atmospheric conditions within and between different observing sites. Here the SHIMM design and methodology for estimating key atmospheric parameters will be presented, as well as initial field test results with comparisons to the Stereo–SCIDAR instrument.