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The ULLYSES Director’s Discretionary Program: Charting Young Stars’ Ultraviolet Light with Hubble[mfn referencenumber=(abstract)]The Hubble Space Telescope’s Ultraviolet Legacy Library of Young Stars as Essential Standards (ULLYSES) is a Director’s Discretionary program of approximately 1,000 orbits that will produce an ultraviolet spectroscopic library of young high- and low-mass stars in the local universe. The design and targets of these observations were selected in partnership with the astronomical community, allowing researchers from around the world to help develop the final program as well as have the opportunity to organize coordinated observations by other space- and ground-based telescopes. The program is composed of two distinct components: approximately 500 orbits are dedicated to UV spectroscopy of T Tauri stars in 8 star-forming regions in the Milk Way, while another 500 orbits focus on massive stars in the Magellanic Clouds, NGC 3109, and Sextans A. The ULLYSES T Tauri stars sample a broad range of stellar masses and accretion rates. Over the next 3 years, ULLYSES will obtain single epoch COS and STIS spectra of 67 survey targets and time monitoring of 4 prototypical T Tauri stars, optimizing the scheduling of the HST observations to coincide with TESS campaigns for a substantial fraction of targets. This legacy program is expected to lead to transformative advances in our understanding of the accretion rates and UV radiation fields of young low mass stars, and their impact on disk chemistry and planet habitability. ULLYSES observations of massive stars will be used to augment the current archive of far- and near-UV spectra of O, B and Wolf-Rayet stars, with the primary goal of ensuring that fundamental stellar parameters (such as spectral type, luminosity class, and metallicity) are well represented. This unique collection of low- and medium-resolution UV spectra will enable diverse and exciting astrophysical research across many fields. Significant advances are expected from the detailed characterization of the atmospheric properties of massive stars with sub-solar metallicities; studies of galactic evolution enabled by population synthesis based on complete UV libraries of template spectra; and reliable probing of the conditions in the interstellar medium in and around many different astrophysical environments. This presentation will update the community on the status of ULLYSES by discussing (a) the selection of targets; (b) the observing strategy; and (c) plans for the disseminating the spectra. The continued, active engagement of the community is a key to the overall success of this project. Ideas and involvement are actively solicited to ensure the efficient analysis and effective use of the spectroscopic treasures that ULLYSES will return.[/mfn]

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Outflows and Disks around Young Stars: Synergies for the Exploration of Ullyses Spectra (ODYSSEUS)[mfn referencenumber=(abstract)]Here we present an overview of the science goals of ODYSSEUS, a team of 55 young star experts from around the world that have united to analyze data from the upcoming HST ULLYSES DDT Survey of low-mass pre-main sequence stars. ULLYSES, coupled with forthcoming data from ALMA and JWST, will provide the foundation to revolutionize our understanding of the relationship between young stars and their protoplanetary disks. A comprehensive evaluation of the physics of disk evolution and planet formation requires understanding the intricate relationships between the mass accretion, mass outflow, and disk structure. The ODYSSEUS team will (1) measure how the accretion flow depends on the accretion rate and magnetic structures, (2) determine where winds and jets are launched and how mass loss rates compare to accretion, and (3) establish the influence of FUV radiation on the chemistry of the warm inner regions of planet-forming disks. The ODYSSEUS team will also work together to acquire and provide contemporaneous observations at X-ray, optical, near-IR, and mm wavelengths to enhance the impact of the ULLYSES data. By the end of our comprehensive 3-year program, we will provide the best measurements of the levels and evolution of mass accretion of protoplanetary disks, the properties and magnitudes of (inner) disk mass loss, and the UV radiation fields that determine ionization levels and drive disk chemistry.[/mfn]

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The high-energy environment and atmospheric escape of small exoplanets[mfn referencenumber=(abstract)]Similarly to stars, planets also lose mass with time, even our own Earth. In particular, hot extrasolar planets orbiting close to their host stars are subject to large mass loss rates due to heating by high-energy irradiation and subsequent atmospheric escape. This process is so pervasive among hot planets that it imprints features in the population of transiting exoplanets, such as the hot-Neptune desert and the photoevaporation valley of super-Earths. Are small planets able to fight atmospheric escape and retain their primary atmospheres? If so, for how long? In this seminar, I will briefly go over some recent advances in observing the upper atmospheres of small transiting exoplanets aiming to constrain their rates of atmospheric escape and their high-energy environment. I will also present the main challenges of these observations, in particular the impact of stellar activity. Finally, I will discuss what are the best targets to observe atmospheric escape, and the future prospects for research.[/mfn]

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Probing Protoplanetary Disk Winds with FUV Absorption Lines[mfn referencenumber=(abstract)]The evolution and dispersal of protoplanetary disks play an important role in planet formation, and are largely driven by angular momentum transport and mass loss due to disk winds, including fast magnetized disk wind and slow thermal (photoevaporative) wind. Disk winds are most commonly identified in optical forbidden line emission, but the mass loss rates from emission lines remain uncertain. Absorption lines have the potential to provide a powerful complement to the emission lines by probing the wind in our line-of-sight to the star. We present an observational analysis of wind absorption in far-ultraviolet stellar spectral lines from our Hubble Space Telescope survey of 40 disk-hosting stars. We detect blueshifted absorption feature in the C II doublet at 1335 angstrom in 36 out of 40 targets, indicating fast or slow disk winds. Wind absorption is preferentially detected in lines of neutral or singly ionized atoms, and is very rarely detected in Si III and C IV. We discuss the implication of our results by comparing to the accretion and disk properties. Our model of C II wind absorption assuming thermal-magnetic disk wind well explains the observational wind absorption profiles, for both fast and slow winds. In our disk wind models, the wind absorption occurs close to the stars, while the emission lines are expected to trace the wind in large volumes. A comprehensive evaluation of wind mass loss should account for both absorption and emission components.[/mfn]

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Atmospheric Escape from Extrasolar Planets: From stellar inputs to exoplanetary signatures with the ESCAPE and CUTE missions[mfn referencenumber=(abstract)]The long-term stability of exoplanetary atmospheres depends critically on the extreme-ultraviolet (EUV) flux from the host star. The EUV flux likely drives the demographics of the short-period planet population as well the ability for rocky planets to maintain habitable environments long enough for the emergence of life. I will present the Extreme-ultraviolet Stellar Characterization for Atmospheric Physics and Evolution (ESCAPE) mission, a NASA astrophysics Explorer mission currently in Phase A. ESCAPE employs EUV and FUV spectroscopy (70 – 1700 Angstroms) to characterize the high-energy radiation environment around nearby stars, including flares and energetic particles. ESCAPE provides the first comprehensive study of the stellar EUV environments that control atmospheric mass-loss.
The Colorado Ultraviolet Transit Experiment (CUTE) is a NASA-supported 6U CubeSat mission designed to characterize the interaction between exoplanetary atmospheres and their host stars. CUTE will search for: 1) enhanced transit absorption in atomic, molecular, and continuum tracers at NUV wavelengths (255 – 330 nm) and 2) evidence of transit asymmetries, ahead of the planet’s orbital motion or trailing “tails”. This dataset will provide an unprecedented look at atmospheric mass-loss in the most extreme planets, which is key to our understanding of planetary evolution. This presentation will provide a summary of the ESCAPE and CUTE science missions, an overview of the instrument and spacecraft designs, and a status update on the two projects.[/mfn]

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UV-SCOPE: A MidEx Mission Concept for the Ultraviolet Spectroscopic Characterization Of Planets and their Environment[mfn referencenumber=(abstract)]UV-SCOPE aims to measure the UV transmission spectra of exoplanets to probe the conditions and composition of their upper-atmospheres, directly measure exospheric escape, and derive the associated impact of stellar UV radiation upon planets, as it is key to the formation, evolution, and chemistry of exoplanet atmospheres. For rocky, habitable zone planets this also includes the UV impact on planet habitability and the detection and interpretation of biosignatures using future instrumentation. UV-SCOPE would be the first, large-scale UV spectroscopic mission devoted to time-domain observations of exoplanets and their stars. By observing young and old AFGKM stars with transiting planets simultaneously with both far- and near-UV spectroscopy, we seek to answer the following questions:
• How do planet atmospheres form and evolve under various stellar conditions?
• What are those planet atmospheres really made of?
• Can planets around active stars be habitable?
• What are the physics in stellar atmospheres that produce such strong UV emission and flares in low-mass stars?
In addition to filling the potentially decade(s?) long gap in U.S. access to UV spectroscopy, UV-SCOPE will provide the observations needed to help answer these driving questions in exoplanet science. [/mfn]

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Ultraviolet Researcher for the Investigation of the Emergence of Life[mfn referencenumber=(abstract)]The Ultraviolet Researcher for the Investigation of the Emergence of Life (URIEL) mission is designed to evaluate the feasibility of the remote detection of alanine in Solar System bodies by its optical activity at 180 nm. A recent evaluation of alanine’s optical rotatory dispersion (ORD) indicates that enanotiomeric imbalances of ~10% and higher should be detectable with the collecting capability of a medium size UV telescope. This capability will also provide unique data in protoplanetary disk, planet formation, the erosion of planetary atmospheres by stellar winds and the properties and location of dust concentrations in young planetary disks. URIEL is conceived as 50 cm primary telescope with a Ritchey-Chrétien mounting. The telescope is equipped with a single instrument to obtain spectropolarimetric observations in the 150-600 nm wavelength range. with dispersion is 600. This dispersion enables resolving the spectral features whilst guarantees enough flux per resolution element for the Stokes parameters to be measured accurately in the full range. A technological precursor, CUVUS, is being developed to flight a 12U cubesat.[/mfn]

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Feasibility study for the implementation of small-size astronomical UV telescopes[mfn referencenumber=(abstract)]The new technological advances in instrument and materials to design state-of-the-art telescopes, and the reducing cost for launching CubeSats, made us start a feasibility study for the design and construction of modest-cost small UV telescopes that could help for the further understanding of the universe.
We propose the design of a 36 cm UV telescope that can be fit in a 27U CubeSat platform. A 2-mirror telescope with a primary of 570 mm radius and a 360 x150 mm rectangular size, and the secondary with a radius of 246 mm and a 120 x 48 mm rectangular size. The telescope could be used for exoplanet scientific research by working in a wavelength range between 120 to 280 nm and with a resolving power between 1000 to 10000.
The focusing points of our study are the nowadays advances in the key technologies that allow for the design of compact optical devices, and the coatings that provide the required optical quality for FUV science. The last advances in FUV coatings that guarantee more than 80% of surface reflectivity; the new advances in additive manufacturing and polishing technologies, that can reduce the instrument weight more than 60%; and the new and space qualified commercial off-the-shelf (COTS) components, provide the needed solutions to plan small and moderate-cost UV missions embedded in CubeSat platforms.
This study includes, moreover, a basic estimation of power, mass and volume budgets to be able to fit the required standard devices (solar panels, batteries, reaction wheels, start trackers, thrusters, communication) in a 27U CubeSat platform (54 Kg and 34 cm x 35 cm x 36 cm)[/mfn]

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17:10

UVA Working Group

UV Photometry

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Doc. on the creation of the UV photometric system

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Young stellar populations in massive early-type galaxies from UV spectroscopy[mfn referencenumber=(abstract)]The integrated UV light from galaxies is a good tracer of their content in young stars. The study of the stellar populations in galaxies is required for understanding their formation and evolution. The bulk of the stars in Early-Type Galaxies (ETGs, i.e. ellipticals and lenticulars) is overwhelming dominated by very old stellar populations so that small episodes of recent star formation are rather difficult to constrain if the analysis is restricted to the optical range. Fortunately, this can be tackled in the UV, which is full of absorption lines that are affected by small amounts of young stars on top of the old stellar populations. Using near-UV and optical stacked spectra from SDSS/BOSS data we have obtained unambiguous constraints on the fraction of young stellar populations in massive ETGs at redshift z~0.4. We find that, on average, ~0.5% of the stars are formed in the last 2 Gyr of the evolution of these galaxies and this fraction decreases with galaxy stellar mass. Furthermore, we also find that the young stars are mainly concentrated in the inner regions (< 2 kpc) of a sample of six brightest cluster galaxies in the nearby Universe. Our work highlights the need of obtaining UV spectra for studying the stellar populations of ETGs.[/mfn]

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Dr. Patrick
Cote

National Research Council of Canada, Herzberg Astronomy & Astrophysics Research Council, Canada

Update on the CASTOR Mission: Science[mfn referencenumber=(abstract)]CASTOR is a wide-field, nearly diffraction-limited space telescope concept that has been the subject of recent studies and technology development activities sponsored by the Canadian Space Agency (CSA). The 1m CASTOR telescope will produce panoramic imaging of the UV/optical (150-550 nm) sky, using a three mirror anastigmat design to provide HST-like image quality over a wide field of view (0.25 sq. deg.) in three filters, simultaneously. Operating from low-earth orbit, CASTOR will be optimized for wide-field surveys, although the telescope may also feature low- and medium-resolution spectroscopic capabilities over the 150 to 400 nm region. In this talk, I present highlights from a recent Science Maturation Study that examined CASTOR’s scientific capabilities in a wide range of fields, including Dark Energy and Weak Lensing; Time Domain and Multi-messenger Astronomy; Galaxy Evolution and AGNs; Star Formation, ISM, & IGM; Stellar & Galactic Astronomy; Compact Objects; Exoplanets; and Trans-Neptunian Objects. I also describe the expected observing plans for the facility, which will consist of both GO program and legacy surveys, including a primary survey that will image about 1/5th of the sky to a (u-band) depth 1.3 mags fainter than the final (10-year) depth of LSST.[/mfn]

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The Halo of Andromeda: a Case Study for a Large Aperture UV Telescope[mfn referencenumber=(abstract)]UV absorption-line studies of single sight lines through an ensemble of galaxy halos have shown that the circumgalactic medium (CGM) plays a major role in galaxy evolution. However, these observations fail to capture accurately the radial-azimuthal dependence of the CGM properties, which have significant diagnostic power. The M31 galaxy is unique in the sense that it is the only massive galaxy (besides our own Galaxy) in the universe with the current technology where its CGM has been probed by not 1 or handful of QSOs, but a sample of 43 QSOs that were observed with HST/COS in its high resolution mode. Our large sample provides an unparalleled look on how the metals and physical conditions are distributed in the CGM of a single galaxy using ions that probe a wide range of gas-phases, ions that are available only in the UV. I will discuss how these findings are transformative, the motivations for a large aperture UV telescope to target the CGM of galaxies beyond M31, and how future deep radio HI surveys of the CGM of galaxies will likely never produce the richness achieved by a UV telescope. [/mfn]

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Clues on the history of early-type galaxies from SDSS spectra and GALEX photometry[mfn referencenumber=(abstract)]Stellar population studies of early-type galaxies (ETGs) based on their optical stellar continuum suggest that these are quiescent systems. However, emission lines and ultraviolet photometry reveal a diverse population. We use a new version of the STARLIGHT spectral synthesis code and state-of-the-art stellar population models to simultaneously fit Sloan Digital Sky Survey spectra and Galaxy Evolution Explorer photometry for a sample of 3453 galaxies at z < 0.1 with near ultraviolet (NUV) – r > 5 that are classified as elliptical by Galaxy Zoo. We reproduce far ultraviolet (FUV) magnitudes for 80% of UV upturn galaxies selected using standard criteria from the literature, this suggest that additional stellar population ingredients such as binaries and extreme horizontal branch stars may have a limited contribution to the UV upturn. The addition of ultraviolet data leads to a broadening of the distributions of mean stellar ages, metallicities, and attenuation. Stellar populations younger than 1 Gyr are required to reproduce the ultraviolet emission in 17% of our sample. These systems represent 43% of the sample at 5 < NUV – r < 5.5 and span the same stellar mass range as other ETGs in our sample. ETGs with young stellar components have larger Hα equivalent widths (WHα) and larger dust attenuation. Emission line ratios and WHα indicate that the ionizing source in these systems is a mixture of young and old stellar populations. Their young stellar populations are metal-poor, especially for high-mass galaxies, indicating recent star formation associated with rejuvenation events triggered by external processes, such as minor mergers.[/mfn]

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Ultraviolet Absorption Studies of the Magellanic Stream[mfn referencenumber=(abstract)]Extending for over 200 degrees across the sky, the Magellanic Stream together with its Leading Arm is the most spectacular example of a gaseous stream in the Local Group. The Stream is an interwoven tail of filaments trailing the Magellanic Clouds as they orbit the Milky Way. Thought to be created by tidal forces, ram pressure, and halo interactions, it holds many clues to the assembly history of the Milky Way. Ultraviolet observations have been at the center of recent progress on the Stream. I will discuss Hubble Space Telescope/Cosmic Origins Spectrograph observations that have constrained the Stream’s chemical composition, kinematics, ionization, total mass, origin, and fate. Future UV spectroscopic facilities with high sensitivity and resolution will be essential for continued studies of the Stream, and more generally for studies of the chemical evolution of the local Universe.[/mfn]

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Accessing the evolution of the UV upturn[mfn referencenumber=(abstract)]The so-called ultraviolet (UV) upturn of elliptical galaxies is a phenomenon characterized by the up-rise of their fluxes in bluer wavelengths, between the Lyman limit and 2500 Å. This work aims at estimating the rate of occurrence of the UV upturn over the entire red-sequence population of galaxies that show significant UV emission, in terms of redshift and stellar mass. The analysis is then expanded to account for emission line classification. We built a multiwavelength spectrophotometric catalogue from the GAMA survey, together with aperture-matched data from GALEX-MIS and SDSS-DR7, covering the redshift range between 0.06 and 0.40. From this sample, we analyse the UV emission among UV bright galaxies, by selecting those that occupy the red-sequence locus. To that end, we make use of the photometric classification by Yi et al. (2011), and emission-line diagnostic diagrams. A Bayesian logistic model was built to simultaneously deal with the effects of confounding variables (including emission-line classification or lack thereof). The main results show that retired/passive systems host an up-rise in the fraction of UV upturn for redshifts between 0.06 and 0.25, followed by an in-fall up to 0.35. We also show that the fraction of UV upturn hosts rises with rising stellar mass.[/mfn]

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First Co-spatial Comparison of Stellar, Neutral-, and Ionized-gas Metallicities in a metal-rich galaxy: M83[mfn referencenumber=(abstract)]Extragalactic abundance measurements have been critical for deciphering a plethora of physical and evolutionary processes such as, star formation, stellar feedback and interstellar/intergalactic chemical enrichment and mixing. Studies of local star-forming galaxies (SFGs) can be performed at exquisite signal-to-noise and spatial/spectral resolution, which are not achievable at higher redshift. Therefore, these studies establish a baseline in understanding how gas and stellar properties evolve through cosmic time. Metallicity measurements of nearby SFGs galaxies have relied for decades on the analysis of their ionized gas, and to a lesser degree on their young stellar populations. A third and relatively unexplored metallicity component in galaxies is that from the neutral gas. In spite of the variety of tools available to investigate the chemical composition of SFGs, detailed comparisons of the abundances obtained from the ionized-gas, neutral-gas, and stellar components are needed to fully understand the chemical state and evolution of galaxies. We take advantage of the unique FUV spectroscopic capabilities of the Hubble Space Telescope, and complement our space observations with LBT/MODS and VLT/MUSE to carry out the first co-spatial comparative analysis of the metallicities from the multi-phase gas and stellar component in the metal-rich face-on spiral galaxy M83. We bring together the observational evidence from the wealth of ancillary data and different methodologies, into a coherent and detailed picture of the chemical evolution of M83. Similar co-spatial studies are essential for validating the observed trend in a variety of other environments in the Local Universe.[/mfn]

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Mapping Outflowing Gas in the Fermi Bubbles; a UV Absorption Survey[mfn referencenumber=(abstract)]The Fermi Bubbles are an example of extreme feedback in our own Milky Way. These two giant bubbles extend ~10 kpc above and below the center of the Galaxy. They are thought to have formed via an outburst from our central supermassive black hole or nuclear star formation. Understanding the origins of the Fermi Bubbles requires UV spectroscopic facilities to be used for careful measurements of their kinematics and chemical abundances. We have obtained FUV spectra from Hubble/COS to characterize the previously unexplored low-latitude region of the southern Fermi Bubble, close to where the bubbles are launched, over a wide range of Galactic longitudes (−26° ≤ b ≤ −16°). We combine these data with previous FUV and atomic hydrogen datasets to characterize the Fermi Bubbles at all latitudes and gain a more complete picture of the multiphase gas flows and their impact on the Galaxy. Future high sensitivity and resolution UV instruments will be necessary to understand the impact of the Fermi Bubbles on the Milky Way halo.[/mfn]

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CCD and CMOS quantum efficiency evaluation in the EUV and VUV spectral ranges[mfn referencenumber=(abstract)]Accurate measurements of quantum efficiency (QE) in the EUV and VUV ranges for modern CCD and CMOS detectors for laboratory and space applications is still limited due to the complexity of the necessary equipment, especially the source of monochromatic, calibrated and uniform EUV and VUV radiation.
We have taken QE measurements of two modern radiation-hard custom devices based on different technologies (CCD272-64 and GSENSE400BSI-GP CMOS), that can be used in space applications. Both sensors were specially designed to improve VUV/UV and EUV sensitivity respectively.
The CCD272-64 was developed by Teledyne e2v for the WUVS spectrograph of the World Space Observatory Ultraviolet (WSO-UV) space project. The operating spectral range of the CCD is 115-305 nm, the pixel design and output amplifies are optimized to provide low level signal operation with a noise level of 3e- RMS and a maximum signal of 50ke-. We have measured QE values of a CCD with specially designed antireflection coating optimized for best performance in the 174-305 nm spectral range in accordance with WUVS spectrograph characteristics. We compare the QE values taken for coated and uncoated CCD regions.
The GSENSE400BSI-GP CMOS is an experimental device developed by Gpixel company to compare the effectiveness of different technological ways to improve the EUV sensitivity and radiation resistance to strong overillumination in the EUV spectral range. We have compared 4 versions of the CMOS sensor, each with specific post-processing of the back surface: large/small boron implantation and strong/weak annealing. The QE values were measured in 17-59 nm and 120-300 nm spectral ranges.
The QE values of the sensors were measured at Budker Institute of Nuclear Physics, Russian Academy of Sciences. The measurements were carried out at the “Cosmos” beamline using synchrotron radiation from the VEPP-4М synchrotron storage ring. An absolutely calibrated photodiode SPD was used for reference.[/mfn]

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A High-Resolution Imaging Interferometer at the Lunar South Pole: Stellar Imager – Lunar Pole (SI-LP)[mfn referencenumber=(abstract)]NASA’s return to the Moon via the Artemis Program offers significant opportunities to take practical steps towards high impact scientific capabilities. One obvious candidate is extremely high-resolution interferometric imaging at visible and ultraviolet wavelengths. This can resolve the surfaces of stars, probe the inner accretion disks surrounding nascent stars and black holes, and begin the technical journey towards resolving surface features and weather patterns on the nearest exoplanets. A fully developed facility will be large and expensive, but it need not start that way. The technologies can be developed and tested with 2 or 3 small telescopes on short baselines. Once the technology is developed, baselines can be lengthened, larger telescopes can be inserted, and the number of telescopes can be increased. Each of these upgrades can be accomplished with minimal disruption of the rest of the system. A 1996 study (Bely et al., Proc. SPIE 2807, Space Telescopes and Instruments IV, 59) examined the trade-offs between placing kilometric-sized interferometers on the lunar surface vs. designing them as free-flyers in open space. They concluded that, in the absence of a pre-existing human infrastructure on the lunar surface to provide power and on-going maintenance, it was better to pursue space-based free-flyers. Thus, previous studies of interferometers in space concentrated on free-flying designs. However, now a lunar infrastructure is foreseeable as part of the Artemis 2024 program and it is compelling and timely that we investigate building interferometers on the lunar surface. We present here a preliminary mission concept that we are developing for building a high-resolution UV/optical imaging interferometer near the South Pole of the moon, in the vicinity of an Artemis Moonbase.[/mfn]

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A catalog of 2-minute GALEX photometry for intra-visit science[mfn referencenumber=(abstract)]We have created a substantial reimplementation of the calibration and photometric extraction pipelines for the GALEX all-sky survey ultraviolet imaging data as a follow-on to the gPhoton project. All >20 minute GALEX observations through General Release 7 (GR7) have been reintegrated as 2-minute images. Source detection and extraction on these images resulted in a catalog of ~18M UV light curves. We will describe this catalog and how to access it, along with tips and caveats for use.[/mfn]

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CLASSY: The COS Legacy Archive Spectroscopic SurveY[mfn referencenumber=(abstract)]Far-UV spectra are fundamental to our understanding of star-forming galaxies (SFGs), providing a unique
window on massive stellar populations, chemical evolution, feedback processes, and reionization. The launch of
JWST and construction of the ELTs will soon usher in a new era, pushing the UV spectroscopic frontier to
z~15-20. The success of these future endeavors hinges on a comprehensive understanding of the massive star
populations and interstellar medium (ISM) gas conditions that power the observed UV spectral features. This
requires the level of detail that is only possible in local galaxies. Unfortunately, the most prolific UV spectral
database of nearby SFGs not only lacks this requisite sensitivity and resolution, but also has limited parameter
space coverage. In this talk we present The COS Legacy Archive Spectroscopic SurveY (CLASSY), a 135 orbit HST Cycle 27 Treasury program that builds upon archival data to create the first high-quality, high-resolution FUV spectral
catalog of SFGs at z~0. Our sample of 46 SFGs was selected to span similar properties as seen at high-z, with a
large range of masses, metallicities, star formation rates, ionization parameters, and densities. The spectra
detect a suite of emission and absorption lines from massive stars and the ISM. We will use this spectral atlas to
investigate the massive stellar populations that populate metal poor galaxies, the physical properties of large scale
outflows that regulate star formation, and the chemical abundance patterns of the gas and stars. CLASSY
will improve the diagnostic power of the UV lines for future JWST/ELT surveys, providing a long-lasting
legacy to the astronomical community for decades to come.
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Special session on coordinating activities

Spectrum-UV/WSO-UV status 2020 [mfn referencenumber=(abstract)]The Spectrum-UV/WSO-UV space telescope is an ultraviolet observatory to run imaging and spectroscopic observations in the 115-315 nm range. The telescope has a 170 cm primary and it is equipped with instruments for high resolution spectroscopy (50,000), long slit low resolution spectroscopy (1000), high angular resolution imaging in the 115-175 nm range (FCU/FUV) and wide field imaging in the 175-600 nm range (FCU/NUV). The project is now in the mid of the construction phase. In this contribution the current status of mission will be presented.[/mfn]

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The LUVOIR Mission Concept: Telling the Story of Life in the Universe[mfn referencenumber=(abstract)]The Large UV/Optical/Infrared Surveyor (LUVOIR) is one of four large mission concepts studied in preparation for the US Astro2020 Decadal Survey. This guest observer-driven, serviceable observatory will enable revolutionary breakthroughs in astrophysics, exoplanet science, and solar system remote sensing. LUVOIR was designed for stability to enable high-contrast direct observations of Earth-like exoplanets and far- to near-UV capability to enable a wide range of astrophysical studies.
Two distinct observatory designs have been developed, both featuring segmented, deployable telescopes: LUVOIR-A, an on-axis telescope with a 15-m primary mirror diameter and LUVOIR-B, an off-axis telescope with an 8-m primary. The candidate instruments studied are: 1) a high-performance NUV/optical/NIR coronagraph with imaging and spectroscopic capability, 2) a UV imager and spectrograph with multi-resolution and multi-object capability, 3) a high-definition wide-field optical/NIR camera, and 4) a high-resolution UV spectropolarimeter. The fourth instrument was designed by a consortium of European institutions, with support from CNES. This presentation will describe the observatories and provide an overview of the transformative science LUVOIR could accomplish.[/mfn]

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Astrophysics with POLLUX, a high-resolution spectropolarimeter on LUVOIR[mfn referencenumber=(abstract)]We introduce POLLUX, a concept for a high-resolution UV spectropolarimeter designed for the 15-m primary mirror architecture of LUVOIR. LUVOIR is one of four Mission Concept Studies initiated by NASA for its 2020 Decadal Survey of Astronomy and Astrophysics. POLLUX is designed to operate over a broad spectral range (90 to 400 nm), at high spectral resolution (R >= 120,000), with a unique spectropolarimetric capability. I will present the instrument concept and innovative technologies development needed to achieve the desired performances of the instrument. I will also review the science case of POLLUX, and outline the potential of this instrument for ground-breaking discoveries. [/mfn]

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The European Ultraviolet-Visible Observatory[mfn referencenumber=(abstract)]The European observatory for ultraviolet-visible observatory (EUVO) is a scientific proposal to build a versatile space observatory with UV sensitivity a factor of 50-100 higher than the existing facilities. Such a facility will revolutionize our unnderstanding of the pathway to life in the Universe and will be synergic with the last investments being done at global scale to investigate the emergence of life in the Universe (VLT, JWST, ELT, GMT, TMT, ALMA, FAST, VLA, ATHENA, SKA) including the ESA’s CHEOPS, PLATO and ARIEL missions. In this contribution, the main science to be carried by this facility is outlined. Also, some baseline architectures are proposed ranging from 10-15 meters deployable mirrors to compact, ~5 meter diameter monoblock fitting into an Ariane VI launcher.[/mfn]

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Cosmic Evolution Through UV Surveys[mfn referencenumber=(abstract)]In November 2016, we proposed to NASA to study Cosmic Evolution Through UV Surveys (CETUS), a Probe-class mission concept (i.e. cost to NASA less than $1B) that would be ready for development starting in FY2023. CETUS was the only UV mission concept to be selected by NASA for study. We completed our study in 2019 and posted our CETUS Final Report at ArXiv: 1909.10437. In January 2020, we presented the case for CETUS to Astro2020’s panel on ElectroMagnetic Observations from Space.
Here, we will introduce the CETUS mission concept by comparing it with a mission we already know: the Hubble Space Telescope. Hubble is a UV-optical-IR telescope. By design, it does things that only a telescope in space can do: it obtains exquisite images of astronomical sources unmarred by atmospheric seeing effects; and from above Earth’s atmosphere, it observes UV radiation from astronomical sources. CETUS is an all-UV space mission concept, and it does things that only CETUS can do. The five main capabilities of CETUS that even Hubble doesn’t have are:
(1) wide-field (17.4’x17.4’) UV imaging and spectroscopy of astronomical sources with 0.5” resolution;
(2) spectral sensitivity to UV radiation at wavelengths as short as 1000 Å;
(3) near-UV multi-object slit spectroscopy;
(4) rapid-response UV spectroscopy and deep imaging of transients like GW 170817; and
(5) 23 times higher sensitivity than Hubble to faint extended sources.
These new capabilities of CETUS will enable new types of observations, so the potential for discovery is high.
CETUS will be a worthy successor to Hubble. Except for its multi-object slit spectrograph with a micro-shutter array like JWST’s MOS, CETUS’ camera and point/slit spectrograph are recognizable outgrowths of Hubble instruments:ACS, WFC3, COS, and STIS. The plan is to carry on the work of Hubble far beyond Hubble’s lifetime as well as to make new types of observations. Unlike Hubble, CETUS is a survey telescope. As CETUS observations may be used by multiple astronomers for different purposes, it makes sense for CETUS to have no proprietary time. All data in the CETUS archive will be immediately available to all. The archival data will be science-ready.
The CETUS team welcomes international participation[/mfn]

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Dr. Alan
Scott

Honeywell International, USA

Update on the CASTOR Mission: Design[mfn referencenumber=(abstract)]CASTOR is a wide-field, nearly diffraction-limited space telescope concept that has been the subject of recent studies and technology development activities sponsored by the Canadian Space Agency (CSA). The 1 m CASTOR telescope will produce panoramic imaging of the UV/optical (150-550 nm) sky, using a three mirror anastigmat design to provide HST-like image quality over a wide field of view (0.25 sq. deg.) in three filters, simultaneously. This presentation will give an overview of the mission design, including spacecraft and payload layout, telescope opto-mechanical design, focal plane arrays and spectroscopic instrument packages, thermal control, altitude and data handling, launch plan, orbit maintenance, communications, electronics, and ground support. This talk will outline the mission development plan and summarize ongoing work designed to increase technology readiness levels associated with key mission elements, including the optical design, focal plane array and telescope guiding subsystem.[/mfn]

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CASTOR Team

Planning for a future large UVOIR telescope[mfn referencenumber=(abstract)]A next generation large UVOIR telescope is a tremendously exciting, but very challenging undertaking. It will need to be identified as the highest mission priority in at least one agency but also gain significant support from others to cover its costs, In the US the decadal survey is the process addressing future priorities, informed by a series fo NASA studies of possible flagship missions, while in Europe ESA’s Voyage 2050 is looking ahead to future science priorities and missions beyond 2030. As a participant in the NASA LUVOIR study and lead proposer on the “The Search for Living Worlds and the Connection to our Cosmic Origins” submission to Voyage 2050, I will report on these submissions and the current progress of the various prioritisation activities. I will discuss the potential range of outcomes and what action will be needed from the wider UVOIR community.[/mfn]

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Bridging the Gap: High-Resolution UV Spectroscopy in the 2020s and 2030s[mfn referencenumber=(abstract)]In the post-HST era, which will begin sometime in the 2020-2025 time frame, it is unclear how and when the clear need for high-resolution UV spectroscopy can be met. There are excellent instruments proposed for future large missions, including the LUMOS and Pollux instruments proposed for the Large Ultraviolet/Optical/Infrared Surveyor (LUVOIR) spacecraft and the UVS instrument on the Habitable Exoplanet Observatory (HabEx). While these are powerful instruments with greater sensitivity than STIS and COS and new capabilities (multiobject observing with LUMOS and spectropolarimetry with POLLUX),, they are visions that are distant in time. At best NASA will select one of these major observatories out of four competing missions, and the timescale for future large missions from selection to launch is often 20 years. On this basis neither will launch until the 2040s. After HST there could be a 15 year time interval in which there is no powerful high-resolution UV spectrography in orbit. WSO-UV also called Spektr-UV could fill the gap if launched as proposed in 2025, but it is prudent to push for other options. Other countries (e.g., China, India, Japan) and ESA could build large mission with their long timescales, but moderate-sized and perhaps even smallsats can obtain essential high-resolution spectra with innovative technology and reduced capabilities. Building such instruments is a major challenge for the post-HST era.[/mfn]

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17:30

DISCUSSION