Powerful and novel telescope design is key to pushing the available limits of astronomical sciences and a segmented primary is an attractive approach. For the Nautilus Space mission, a segmented lens has been proposed to replace large monolithic primary optics for the purpose of survey faint objects like exo-planets as well as time-domain astrophysics observations. Enabling technology for Nautilus is an ultra-lightweight multi-order diffractive engineered (MODE) lens that replaces bulky primary mirrors. The MODE lens consists of multiple, identical, molded segments. This is because the complicated optical design of both the diffractive surfaces is not easily manufacturable by traditional fabrication methods. Besides, the molding approach for identical segmented optics allows for a cost-efficient process. Conversely, the fusion of segmented optics demands high precision metrology and a delicate assembly strategy. We propose an in-process metrology technique that mitigates post-assembly process complications. This system monitors the co-phase character of the segmented optics during UV cured assembly, guiding the overall process.
We describe a novel space observatory concept that is enabled by very large (8.5m-diameter), ultralight-weight multi-order diffractive lenses that can be cost-effectively replicated. The observatory utilizes an array of identical telescopes with a total combined light collecting area equivalent to that of a 50m-diameter telescope. Here we review the capabilities of a Nautilus unit telescope, the observatory concept, and the technology readiness of the key components. The Nautilus Observatory is capable of surveying a thousand transiting exo-earth candidates to 300 pc for biosignatures, enabling a rigorous statistical exploration of potentially life-bearing planets and the diversity of exo-earths.
The Exo-Life Finder (ELF) will be an optical system with the resolving power of a ≥20m telescope optimized for characterizing exoplanets and detecting exolife. It will allow for direct detection of Earth-size planets in commonlyconsidered water-based habitable zones (WHZ) of nearby stars and for generic exolife studies. Here we discuss capabilities of the ELF to detect biosignatures and technosignatures in exoplanetary atmospheres and on their surfaces in the visual and near infrared. We evaluate sensitivity limits for mid- and low-resolution spectral, photometric and polarimetric measurements, analyzed using atmosphere models and light-curve inversions. In particular, we model and estimate integration times required to detect O2, O3, CO2, CH4, H2O and other biosignature gases and habitability markers. Disequilibrium biosignature pairs such as O2+CH4 or CO2+CH4–CO are also explored. Photosynthetic and nonphotosynthetic pigments are other important biosignatures that ELF will search for in atmospheres and on resolved surfaces of exoplanets, in the form of bioaerosols and colonies of organisms. Finally, possible artificial structures on exoplanet surfaces and in near-exoplanet space can be detected. Practical instrument requirements are formulated for detecting these spectral and structural biosignatures and technosignatures. It is imperative that such a study is applied first to characterize the nearest exoplanet Proxima b, then to search for exo-Earths in the Alpha Cen A and B system and other near-Sun stars, and finally to explore larger exoplanets around more distant stars.
The Large Binocular Telescope with its integrated adaptive optics systems and the LBTI beamcombiner provides a good platform for carrying out coherent imagin across its 22.7 m baseline. The first cameras used with LBTI have focused on infrared wavelengths. We describe a concept, called the LBT Interferometer Visible Extension (LIVE) to carry out coherent imaging with the LBT at visible wavelengths. LIVE will be able to create images of some of the stars with the largest angular diameters, map the surface of solar system moons, and provide detailed imaging of the inner scattered light regions of protoplanetary and transition disks. An initial approach can use the beamcombiner with its existing infrared phase sensor to carry out coherent imaging using frame selection to improve the image quality. Refined and more versatile phase sensing and correction can be implemented in a second stage to enable observations of a wider range of targets. LIVE will work both as a coherent imager, as well as a flexible dual aperture AO imager where simultaneous differential measurements can be made through independent use of each arm. We describe the science case and technical description below. We plan to develop the system with a flexible approach that allows increasingly complex modes of observation to be added once the basic performance is demonstrated.
In Spring 2013, the LEECH (LBTI Exozodi Exoplanet Common Hunt) survey began its ~130-night campaign from the Large Binocular Telescope (LBT) atop Mt Graham, Arizona. This survey benefits from the many technological achievements of the LBT, including two 8.4-meter mirrors on a single fixed mount, dual adaptive secondary mirrors for high Strehl performance, and a cold beam combiner to dramatically reduce the telescope’s overall background emissivity. LEECH neatly complements other high-contrast planet imaging efforts by observing stars at L’ (3.8 μm), as opposed to the shorter wavelength near-infrared bands (1-2.4 μm) of other surveys. This portion of the spectrum offers deep mass sensitivity, especially around nearby adolescent (~0.1-1 Gyr) stars. LEECH’s contrast is competitive with other extreme adaptive optics systems, while providing an alternative survey strategy. Additionally, LEECH is characterizing known exoplanetary systems with observations from 3-5μm in preparation for JWST.
We are carrying out a survey to search for giant extrasolar planets around nearby, moderate-age stars in the
mid-infrared L' and M bands (3.8 and 4.8 microns, respectively), using the Clio camera with the adaptive optics
system on the MMT telescope. To date we have observed 7 stars, of a total 50 planned, including GJ 450
(distance about 8.55pc, age about 1 billion years, no real companions detected), which we use as our example
here. We report the methods we use to obtain extremely high contrast imaging in L', and the performance we
have obtained. We find that the rotation of a celestial object over time with respect to a telescope tracking
it with an altazimuth mount can be a powerful tool for subtracting telescope-related stellar halo artifacts and
detecting planets near bright stars. We have carried out a thorough Monte Carlo simulation demonstrating our
ability to detect planets as small as 6 Jupiter masses around GJ 450. The division of a science data set into two
independent parts, with companions required to be detected on both in order to be recognized as real, played a
crucial role in detecting companions in this simulation. We mention also our discovery of a previously unknown
faint stellar companion to another of our survey targets, HD 133002. Followup is needed to confirm this as a
physical companion, and to determine its physical properties.
The high optical quality of ESO's ISAAC instrument at the 8.2-m ANTU VLT telescope and the good observing conditions at the Paranal site allow very detailed studies of southern massive star-forming regions. Our observations revealed their large degree of complexity. By means of near- and thermal-infrared images we performed a thorough characterisation of the embedded stellar population. Imaging polarimetry provided clues on the spatial distribution of the dust grains and the illuminating sources. Special emphasis was put on the most massive objects, young luminous stars that cause ultracompact HII regions.