The high contrast and spatial resolution requirements for directly imaging exoplanets requires effective coordination of wavefront control, coronagraphy, observation techniques, and post-processing algorithms. However, even with this suite of tools, identifying and retrieving exoplanet signals embedded in resolved scattered light regions can be extremely challenging due to the increased noise from scattered light off the circumstellar disk and the potential misinterpretation of the true nature of the detected signal. This issue pertains not only to imaging terrestrial planets in habitable zones within zodiacal and exozodiacal emission but also to young planets embedded in circumstellar, transitional, and debris disks. This is particularly true for Hα detection of exoplanets in transitional disks. This work delves into recent Hα observations of three transitional disks systems with MagAO-X, an extreme adaptive optics system for the 6.5-meter Magellan Clay telescope. We employed angular differential imaging (ADI) and simultaneous spectral differential imaging (SSDI) in combination with KLIP, a PCA algorithm in post-processing, for optimal starlight suppression and quasi-static noise removal. We discuss the challenges in protoplanet identification with MagAO-X in environments rich with scattered and reflected light from disk structures and explore a potential solution for removing noise contributions from real astronomical objects with current observation and post-processing techniques.
The Pandora SmallSat is a NASA flight project designed to study the atmospheres of exoplanets. Transmission spectroscopy of transiting exoplanets provides our best opportunity to identify the makeup of planetary atmospheres in the coming decade, and is a key science driver for HST and JWST. Stellar photospheric inhomogeneity due to star spots, however, has been shown to contaminate the observed spectra in these high-precision measurements. Pandora will address the problem of stellar contamination by collecting long-duration photometric observations sampled over a stellar rotation period with a visible-light channel and simultaneous spectra with a near-IR channel. These simultaneous multiwavelength observations will constrain star spot covering fractions of exoplanet host stars, enabling star and planet signals to be disentangled in transmission spectra to then reliably determine exoplanet atmosphere compositions. Pandora will observe exoplanets with sizes ranging from Earthsize to Jupiter-size and host stars spanning mid-K to late-M spectral types. Pandora was selected in early 2021 as part of NASA’s inaugural Astrophysics Pioneers Program. Herein, we present an overview of the mission, including the science objectives, operations, the observatory, science planning, and upcoming milestones as we prepare for launch readiness in 2025.
Long wavelength infrared (8-13 μm) spectroscopy is invaluable for detecting molecular features in the atmospheres of gas giant and terrestrial exoplanets. The nulling-optimized mid-infrared camera (NOMIC) on the Large Binocular Telescope Interferometer (LBTI) has a low resolution (R∼200) germanium grism that was previously installed but has not been characterized and commissioned for scientific observations. Using a 1.27 mm slit and broadband filter in combination with the grism, the infrared window between 8-13 μm can be captured. We describe initial on sky testing of the LBTI/NOMIC grism mode with adaptive optics to study standard stars and binaries. We discuss the impact of observational strategy and telluric calibration on the spectral reduction process. We infer the impact of existing mid-infrared detectors on NOMIC’s spectroscopic mode and discuss requirements to enable higher resolution 8-13 μm spectroscopy on current and future facilities.
Progress in development of a multiple-order diffractive engineered (MODE) lens as applied to space telescopes, where an ultralightweight primary lens is used instead of a mirror, is presented. Precision glass molding is used to fabricate a prototype 0.24 m diameter primary lens, and advanced alignment technology is used to bond lens segments into a ridged, monolithic structure. The primary lens is used in an f/4.17 telescope with a color corrector that provides diffraction-limited imaging over the astronomical R-band of wavelengths (589 nm to 727 nm) and +/- 0.125° field of view. Fabrication data, alignment results, and imaging experiments are presented.
The initial testing of prototype multiple-order-diffraction engineered (MODE) lens telescope is essential process before the sky test to evaluate the optical imaging performance of a space object. Prototype MODE lens telescope consists of MODE primary lens which is a core component to correct secondary spectrum, a field lens and a double Gauss type color corrector and achieves a diffraction limited performance. The performance is tested on the diffraction efficiency with respect to supercontinuum laser wavelength on an optical testbed and evaluated on the polychromatic performance for prototype molded ring segment.
The stray light analysis and testing of multiple-order-diffraction engineered (MODE) lens telescope is an essential step in the evaluation of optical imaging performance of the telescope. The MODE primary lens has a multi-order diffractive (MOD) front surface and single-order (M = 1) diffractive Fresnel lens (DFL) rear surface. Both of MOD and DFL surfaces have four transitions between five annular zones. Stray light can be minimized to prevent unwanted photons from reaching the science instrument detectors. Stray light is evaluated on an optical testbed to test the polychromatic performance with a supercontinuum laser.
To meet the scientific requirements demanded for futuristic space exploration, the Nautilus space mission has adopted the newly developed multi-order diffractive optical elements (MODE) design. Primary optics with large aperture diameters, like those used commonly in observatories, are frequently the design most employed and demanded by astronomers. However, this is limited by the difficult challenges that comes with fabrication, alignment, and launch of said optics. The proposed primary optics fabrication breaks through these challenges by using molded segments as its primary optics. With the main advantage of requiring a relatively simplified assembly process and having a compressed volume, the compact form factor will allow for multiple telescope units to be sent together in a single launch. Additionally, the molding and segmented manufacturing creates a fine structure on the diffractive lens surface that is not easy to obtain via traditional surface removal fabrication processes for an identical optical surface piece. The feasibility of this assembly in respect to its accuracy and labor are the key factors of this approach. Therefore, we developed an in-Progress Metrology Control (iPMC) technique that was combined with a motorized mounting system to give us full autonomous closed-loop control during the UV curing of multiple segments. The iPMC monitors and guides the aligning of the adhesion process of the multi-segment MODE, while the metrology system measures the position of the multi-segments so that an individual actuator can automatically adjust the segment’s orientation during the UV curing process. This is happening simultaneously as the influence matrix of each actuator receives feedback from the metrology system. The validity of the iPMC is then checked using the mock-up MODE lens assembly.
The continued development of multi-order diffractive engineered (MODE) lens technology that utilizes both multi-order diffractive surfaces and a diffractive Fresnel lens surface1–3 allows for the conception and development of future applications of the technology such as lightweight large aperture telescope primary lenses. Manufacturing methods being developed for this technology use glass compression molding to create its unique optical surface features. However, to enable the design and development of larger apertures using the MODE lens, it is necessary to allow segmentation due to the size constraints of current glass molding technology. Previous proceedings presented the effectiveness of the Kinematically-Engaged Yoke System (KEYS) to align the segments of a 0.24-m, PMMA, monochromatic, MODE-like lens (having no diffractive Fresnel lens features). The KEYS alignment system consists of ball bearings with which the step-like features of MODE lens segments kinematically engage with. In previous iterations of the KEYS, these ball bearings were mounted on ultra-fine screws that are adjusted radially with flexures that occupy space in the transverse plane (perpendicular to the MODE lens’s optical axis). We present a new iteration of KEYS in which these radially adjusting flexures have been modified to be located in planes that contain the MODE len’s optical axis. The alignment and optical performance of the MODE lens are evaluated using deflectometry in order to determine its current resolution of lens segment adjustment. Improvement of the KEYS will allow optical performance testing of the aligned lens. This version of KEYS will be used to assemble a 0.24-m, compression molded, glass, segmented MODE lens.
KEYWORDS: Diffractive optical elements, Astrobiology, Telescopes, Space observatories, Planets, Space telescopes, James Webb Space Telescope, Space operations, Stars, Satellites, Optical fabrication
We describe progress on the Nautilus Space Observatory concept that is enabled by novel, very large (8.5mdiameter), ultralight-weight, multi-order diffractive lenses that can be cost-effectively replicated. The scientific goal of Nautilus is the rigorous statistical exploration of one thousand potentially life-bearing planets and the assessment of the diversity of exo-earths. Here we review the science requirements and key design features of Nautilus. The new optical technology (MODE lenses) at the heart of the Nautilus telescopes also poses exciting new optical fabrication and metrology challenges. We will summarize these challenges and provide an overview of emerging solutions.
KEYWORDS: James Webb Space Telescope, Near infrared, Atmospheric modeling, Point spread functions, Stars, Planets, Exoplanets, Atmospheric sciences, Sensors, Spectroscopy, Modeling and simulation
Pandora is a SmallSat mission, designed to study the atmospheres of exoplanets using transmission spectroscopy and to investigate the impact that stellar contamination and variability has on observing the spectra of these worlds. Pandora’s initial science operation lifetime is one year, so optimizing the science return is critical. Here we present two tools created to assist in the design process. The first is a 2-D spectrum simulator being developed to help refine target selection, optimize observation strategies, and assist in the creation of a data reduction pipeline. The second is a pseudo-retrieval framework that provides a quantifiable method for comparing potential targets against a handful of exoplanetary atmospheric parameters important to the Pandora mission. Preliminary results show Pandora will place tighter constraints on atmospheric properties like water abundance compared to HST and answering its mission objectives will help to inform targets for missions like JWST.
Pandora is a low-cost space telescope designed to measure the composition of distant transiting planets. The Pandora observatory is designed with the capability of measuring precision photometry simultaneously with nearinfrared spectroscopy, enabling scientists to disentangle stellar activity from the subtle signature of a planetary atmosphere. The broad-wavelength coverage will provide constraints on the spot and faculae covering fractions of low-mass exoplanet host stars and the impact of these active regions on exoplanetary transmission spectra. Pandora will subsequently identify exoplanets with hydrogen- or water-dominated atmospheres, and robustly determine which planets are covered by clouds and hazes. Pandora observations will also contribute to the study of transit timing variations and phase curve photometry. With a launch readiness date of early-2025, the Pandora mission represents a new class of low-cost space missions that will achieve out-of-this-world science.
One of the main design considerations of the Large Binocular Telescope (LBT) was the goal to resolve the habitable zones (HZs) of the nearest stars at mid-infrared wavelengths around 10 μm. The LBT Interferometer (LBTI) makes use of the telescope’s two 8.4m mirrors on a common mount and their 22.7m edge-to-edge separation for sensitive, high-angular resolution observations at thermal-infrared wavelengths. In addition to adaptive optics imaging using the two mirrors separately, the instrument enables nulling and Fizeau imaging interferometry exploiting the full resolving power of the LBT. The LBTI team has successfully completed the Hunt for Observable Signatures of Terrestrial planetary Systems (HOSTS), for which we used nulling-interferometry to search for exozodiacal dust, and we are continuing the characterization of the detected systems. Here, we describe a new program to exploit the LBTI’s Fizeau imaging interferometric capabilities for a deep imaging search for low-mass, HZ planets around a small sample of particularly suitable, nearby stars. We also review the LBTI’s current status relevant to the proposed project to demonstrate the instrument is ready for such a large project.
Giant exoplanets on 10-100 au orbits have been directly imaged around young stars. The peak of the thermal emission from these warm young planets is in the near-infrared (∼1-5 µm), whereas mature, temperate exoplanets (i.e., those within their stars’ habitable zones) radiate primarily in the mid-infrared (mid-IR: ∼10 µm). If the background noise in the mid-IR can be mitigated, then exoplanets with low masses–including rocky exoplanets–can potentially be imaged in very deep exposures. Here, we review the recent results of the Breakthrough Watch/New Earths in the Alpha Centauri Region (NEAR) program on the Very Large Telescope (VLT) in Chile. NEAR pioneered a ground-based mid-IR observing approach designed to push the capabilities for exoplanet imaging with a specific focus on the closest stellar system, α Centauri. NEAR combined several new optical technologies–including a mid-IR optimized coronagraph, adaptive optics system, and rapid chopping strategy to mitigate noise from the central star and thermal background within the habitable zone. We focus on the lessons of the VLT/NEAR campaign to improve future instrumentation specifically on strategies to improve noise mitigation through chopping. We also present the design and commissioning of the Large Binocular Telescope’s Exploratory Survey for Super-Earths Orbiting Nearby Stars (LESSONS), an experiment in the Northern hemisphere that is building on what was learned from NEAR to further push the sensitivity of mid-IR imaging. Finally, we briefly discuss some of the possibilities that mid-IR imaging will enable for exoplanet science.
Our past GAPplanetS survey over the last 5 years with the MagAO visible AO system discovered the first examples of accreting protoplanets (by direct observation of H-alpha emission). Examples include LkCa15 b (Sallum et al. 2015) and PDS70 b (Wagner et al. 2018). In this paper we review the science performance of the newly (Dec. 2019) commissioned MagAO-X extreme AO system. In particular, we use the vAPP coronagraphic contrasts measured during MagAO-X first light. We use the Massive Accreting Gap (MAG) protoplanet model of Close 2020 to predict the H-alpha contrasts of 19 of the best transitional disk systems (ages 1-5 Myr) for the direct detection of H-alpha from accretion of hydrogen onto these protoplanets. The MAG protoplanet model applied to the observed first light MagAO-X contrasts predict a maximum yield of 46±7 planets from 19 stars (42 of these planets would be new discoveries). This suggests that there is a large, yet, unexplored reservoir of protoplanets that can be discovered with an extreme AO coronagraphic survey of 19 of the best transitional disk systems. Based on our first light contrasts we predict a healthy yield of protoplanets from our MaxProtoPlanetS survey of 19 transitional disks with MagAO-X.
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.
KEYWORDS: Planets, Stars, Telescopes, Monte Carlo methods, Point spread functions, Adaptive optics, Exoplanets, Image processing, Imaging systems, L band
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.
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