# The Origins Space Telescope

Cara Battersby, Lee Armus, Edwin Bergin, Tiffany Kataria, Margaret Meixner, Alexandra Pope, Kevin B. Stevenson, Asantha Cooray, David Leisawitz, Douglas Scott, et al.

► To cite this version:

Cara Battersby, Lee Armus, Edwin Bergin, Tiffany Kataria, Margaret Meixner, et al. The Origins Space Telescope. Nature Astronomy, 2018, 2 (8), pp.596-599. 10.1038/s41550-018-0540-y. hal-02389478

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# The Origins Space Telescope

The Origins Space Telescope, one of four large Mission Concept Studies sponsored by NASA for review in the 2020 US Astrophysics Decadal Survey, will open unprecedented discovery space in the infrared, unveiling our cosmic origins.

Cara Battersby, Lee Armus, Edwin Bergin, Tiffany Kataria, Margaret Meixner, Alexandra Pope, Kevin B. Stevenson, Asantha Cooray, David Leisawitz, Douglas Scott, James Bauer, C. Matt Bradford, Kimberly Ennico, Jonathan J. Fortney, Lisa Kaltenegger, Gary J. Melnick, Stefanie N. Milam, Desika Narayanan, Deborah Padgett, Klaus Pontoppidan, Thomas Roellig, Karin Sandstrom, Kate Y. L. Su, Joaquin Vieira, Edward Wright, Jonas Zmuidzinas, Johannes Staguhn, Kartik Sheth, Dominic Benford, Eric E. Mamajek, Susan G. Neff, Sean Carey, Denis Burgarella, Elvire De Beck, Maryvonne Gerin, Frank P. Helmich, S. Harvey Moseley, Itsuki Sakon and Martina C. Wiedner

The Universe has never been seen like this before. The window into the infrared opens only above Earth's atmosphere, and humanity has barely glimpsed outside. About half of the light emitted by stars, planets, and galaxies over the lifetime of the Universe emerges in the infrared. With an unparalleled sensitivity increase — up to a factor of 1,000 more than any previous or planned mission — the advance offered by the Origins Space Telescope (OST) is akin to that from the naked eye to humanity's first telescope, or from Galileo's first telescope to the first telescope in space. While key path-finding missions have glimpsed a rich infrared cosmos, extraordinary discovery space awaits; the time for a far-infrared revolution has begun.

Are we alone or is life common in the Universe? OST will directly address this long-standing question by searching for signs of life in the atmospheres of potentially habitable terrestrial planets transiting M dwarf stars. How do planets become habitable? OST will trace the trail of cold water from the interstellar medium, through protoplanetary disks and into the outer reaches of our own Solar System. How do stars, galaxies, black holes and the elements of life form, from the cosmic dawn to today? With broad wavelength coverage and fast mapping speeds, OST will map millions of galaxies, simultaneously measuring star formation rates and black hole growth across cosmic time, peering deeper into the far reaches of the Universe than ever before.

OST will be maintained at a temperature of 4 K, enabling its tremendous sensitivity gain, and will operate from 5 µm to 600 µm, encompassing the mid- and far-infrared. OST has two Mission Concepts: Concept 1 with a 9.1-m deployed off-axis primary, and

Concept 2, described here, a non-deployed 5.9-m on-axis telescope with the equivalent collecting area of the James Webb Space Telescope (JWST). Concept 2 includes four instruments with capabilities for imaging (large surveys and pointed), spectroscopy (survey and high-resolution modes) and polarimetry, as well as an instrument for high-precision spectroscopy of transiting exoplanets. Concept 2 is optimized for maximum science return and minimal complexity, and offers fast mapping (approximately 60 arcseconds per second). We describe here the three key science themes for OST and the basic mission specifications.

## Are we alone in the Universe?

For the first time in human history, our generation will have the technology to answer this age-old question. Planet-hunting programmes (such as TRAPPIST¹, MEarth² and Kepler³) recently confirmed the first Earth analogues orbiting M dwarfs. However, it is unknown whether planets orbiting M dwarfs, the most ubiquitous stars in our Galaxy, can support life. OST will characterize the atmospheres of Earth-sized planets, and search for biosignatures.

Exoplanets are incredibly dim compared with their host stars. The transit technique is currently the only method that has characterized the atmospheres of potentially habitable worlds⁵. During primary transit, we observe the planet pass in front of its host star, which unambiguously determines the planet's size and, when combined with a mass measurement, its bulk density. Knowledge of these fundamental parameters, in addition to temperature, is an essential first step towards assessing a planet's ability to support life. OST will expand on the legacy of exoplanet science with the Hubble Space Telescope, Spitzer

Space Telescope and the upcoming JWST by using the transit technique to study the climates of Earth-sized worlds orbiting within the habitable zones of M dwarf stars.

The true indicator of life, however, is the detection of biosignatures, a combination of molecules whose presence together in an atmosphere can only be sustained by life. For example, the measurable presence of methane (a reducing molecule) in the Earth's oxidizing atmosphere (containing oxygen and ozone) is widely considered to be a biosignature⁵. OST will include an instrument designed to detect light absorbed and re-radiated by potentially habitable planets, whose emission peaks in the mid-infrared (Fig. 1). By obtaining emission and transmission spectra from 5 µm to 25 µm, OST will be able to precisely measure a planet's atmospheric thermal structure and search for habitability indicators such as water, carbon dioxide, ozone and methane. The definitive detection of both ozone and methane in the atmospheres of one or more planets will be the strongest evidence that we are not alone and, in fact, that life is common in our Galaxy.

## How do planets become habitable?

The trail of water leads to a habitable world, but it begins in the cold expanse of interstellar space, where water forms in condensing, starless cores. As the cores collapse into protoplanetary disks, this water is distributed through the disk, with a transition from a hot (temperature T > 200 K), vapour-dominated phase to a cold, ice-dominated phase at the water snowline. Although pioneering observations with previous infrared facilities (for example ref. ⁶) have provided glimpses of this water trail, a complete picture has so far remained elusive.
<figure><img src="image_2.png" /><figcaption>**Fig. 1** | **Are we alone in the Universe?** OST will search for biosignatures in the atmospheres of potentially habitable terrestrial planets transiting M dwarfs to determine whether we are alone in the Universe. Credit: Sun image courtesy of NASA/JPL-Caltech; rest of image, NASA Goddard/JPL-Caltech</figcaption></figure>

Uncovering the trail of water requires a space-based platform, such as OST, operating from the mid-infrared, where hundreds of water transitions probe gas at high temperature (T > 400 K), to the far-infrared, where ground-state transitions probe cooler (10 K < T < 400 K) water vapour. These ground-state transitions are needed to trace the snowline location, which is posited as a favoured site for planet formation⁷ and the accretion of oceans on forming planets. Within our Solar System, OST will survey nearly a hundred comets and provide a true sample of the D/H ratio (through measurement of HDO/H₂O), and

its variations, in cometary reservoirs — key to understanding the origin of water in the Earth's oceans.

OST's high sensitivity and broad wavelength coverage will allow us to probe the envelopes of collapsing gas clouds, tracing the heretofore hidden supply of water to a natal disk, and simultaneously detecting water vapour in hot and cold gas in protoplanetary disks out to the distance of Orion. Along with the ability to probe HD, a tracer of the total H₂ mass⁸, astronomers will be able to sample the evolving water content, both gas and ice, together with the water snowline as a function of stellar mass

and evolutionary state. Ultimately, OST will provide the definitive picture of how water forms and is provided to planetary systems, which, with this central ingredient and others, can lead to the initiation of life on alien worlds.

**From cosmic dawn to today**

The Milky Way has spent the past 12 billion years growing into the familiar spiral Galaxy we live in today: its central supermassive black hole growing along with the stars, mostly hidden behind dust⁹. To understand the complicated relationship between the growth of stars and black holes in galaxies, and chart this evolution over cosmic time, OST will characterize spectroscopically large samples of distant galaxies at the wavelengths at which they emit most of their energy, thereby viewing the Universe at earlier and earlier epochs, effectively rewinding the clock on the lifecycle of galaxies. As OST pushes to the earliest epochs, we will observe the rise of metals and dust — the creation and dispersal of heavy elements inside and outside galaxies through successive generations of stellar birth and death — from the first stars and galaxies to the present epoch.

Infrared observations provide unique tracers of the gas that feeds both star formation and black hole growth (Fig. 2). The powerful energy emitted from growing supermassive black holes plays a critical role in regulating star formation in galaxies. OST will measure this feedback on the dense interstellar medium of nearby galaxies and will revolutionize our ability to identify and measure galactic outflows over the past 12 billion years, linking theory and observations of how galaxies grow inside their dark matter halos.

A unique power of OST is its ability to conduct deep and wide spectroscopic surveys, taking full advantage of the large increase in sensitivity, while avoiding many of the problems imposed by source crowding in photometric surveys. OST will conduct deep spectroscopic surveys over tens of square degrees, simultaneously measuring redshifts, star formation rates and black hole accretion rates in millions of galaxies, using bright, infrared emission lines from hot gas as well spectral features from dust grains excited by ultraviolet photons from young stars. These surveys will map out the cosmic history of star formation and black hole accretion over more than 95% of the age of the Universe. With the ability to trace the rise of metals, stars and galaxies, as well as star formation and black hole growth from cosmic dawn to today, OST will unveil the full story of our cosmic origins.

<figure><img src="image_3.png" /><figcaption>**Fig. 2** | **OST simultaneously traces star formation, feedback and active galactic nuclei over cosmic history.** OST will simultaneously observe key diagnostics of star formation (such as polycyclic aromatic hydrocarbon features as well as [Ne II], [Si II], [O I] and [C II] lines), feedback (such as H₂ lines) and black hole growth (such as [Ne V] and [O IV] lines) for millions of galaxies across 95% of the age of the Universe. Owing to its ability to perform deep, wide spectroscopic surveys, OST will benefit from the factor of 1,000 increase in sensitivity while avoiding limitations imposed by source confusion. AGN, active galactic nuclei; ALMA, Atacama Large Millimeter/submillimeter Array. Credit: NASA/JPL-Caltech; star formation inset panel courtesy of NASA/JPL-Caltech/Harvard-Smithsonian CfA; feedback panel courtesy of NASA/JPL-Caltech/T. Megeath (University of Toledo); AGN panel courtesy of NASA/Goddard Space Flight Center Conceptual Image Lab</figcaption></figure>
<figure><img src="image_4.png" /></figure>

**Fig. 3 |** OST offers an expansive new discovery space. Spectral line sensitivity (5σ in 1 hour) across the far-infrared band for the OST instruments (blue) for Concept 2 (5.9 m) compared with existing and future facilities. The OST has a sensitivity up to a factor of 1,000 higher than any previous or planned facility. The OSS and ALMA sensitivities refer to high-resolution (R = 10<sup>6</sup>) observations, for example for protoplanetary disks and interstellar medium kinematics. MIRI, Mid-Infrared Instrument; PACS, Photodetector Array Camera and Spectrometer; SPIRE, Spectral and Photometric Imaging Receiver; SOFIA FIFI-LS, Stratospheric Observatory for Infrared Astronomy, Far Infrared Field-Imaging Line Spectrometer. Credit: NASA and the Origins Space Telescope Science and Technology Definition Team

## The OST Mission Concepts

OST is one of four Decadal Survey Mission Concept Studies sponsored by NASA for the 2020 National Research Council Decadal Study in Astronomy and Astrophysics in the United States. The OST study has two Mission Concepts, both covering wavelengths from 5 to 600 µm. Mission Concept 1 consists of a 9.1-m off-axis telescope and five instruments. Mission Concept 2, currently under development and the focus of this article, is an optimized concept addressing all key science themes outlined above, composed of a 5.9-m on-axis telescope with JWST-sized collecting area and four instruments. The telescope in Mission Concept 2 is a three-mirror anastigmat, providing a field of view that allows OST to achieve all of its science goals. A field-steering fourth mirror enables the rapid sky motion needed for the far-infrared detectors. A multilayer sunshade, a cold baffle and cryocoolers ensure that the telescope environment is maintained at 4 K, key to achieving OST's unprecedented sensitivity gain.

The four instruments under study for Mission Concept 2 enable a broad range of scientific advancements, including those

described here, but are designed to be flexible to the key questions of the 2030s and immense discovery space opened by OST (Fig. 3). The OST Survey Spectrometer (OSS; resolution R ≈ 300 and R > 40,000 for 30–600 µm) will provide imaging and spectroscopy over large extragalactic fields and will study protoplanetary disks. The Mid-Infrared Imager, Spectrometer and Camera (MISC) instrument (R ≈ 300) will conduct transit and emission spectroscopy of transiting exoplanets (Earth-sized to Jupiter-sized), with simultaneous wavelength coverage from 4 to 22 µm. It will have an imager and imaging spectrometer, and will also be used to guide the observatory. OST's Far-Infrared Imaging Polarimeter (FIP) will conduct 40-, 80-, 120- and 240-µm imaging and polarimetry of wide extragalactic fields and star-forming regions in our Galaxy. The Heterodyne Receiver for OST (HERO; resolution R ≈ 10<sup>9</sup>–10<sup>7</sup> in selected wavelength bands between 111 µm and 566 µm) will measure the kinematics of gas in the interstellar medium and in protoplanetary disks.

The observatory will be outfitted with control moment gyroscopes and momentum wheels to enable large-scale mapping of the sky at approximately 60 arcseconds per second. Additionally, OST will support moving target tracking for Solar System observations. The OST Concept 2 design has minimal deployments (sunshields and solar arrays). The flight system, comprising the telescope, instrument accommodation module, sunshield and spacecraft, will be launchable in a fairing 7 or 8 m in diameter. Three possible launch vehicles — NASA's Space Launch System and two commercial vehicles — are expected to be equipped with such fairings by the 2030s, when OST is planned to launch.

## Summary

With a sensitivity gain of up to a factor of 1,000 over any previous or planned mission, OST will open unprecedented discovery space, allowing us to peer through an infrared window teeming with possibility. OST will fundamentally change our understanding of our cosmic origins — from the growth of galaxies and black holes, to uncovering the trail of water, to life signs in nearby Earth-sized planets, and to discoveries never imagined. Built to be highly adaptable, while addressing key science across many areas of astrophysics, OST will usher in a new era of infrared astronomy. ☐

Cara Battersby¹*, Lee Armus², Edwin Bergin³, Tiffany Kataria⁴, Margaret Meixner⁵,⁶, Alexandra Pope⁷, Kevin B. Stevenson⁵,

Asantha Cooray⁸, David Leisawitz⁹, Douglas Scott¹⁰, James Bauer¹¹, C. Matt Bradford⁴,¹², Kimberly Enrico¹³, Jonathan J. Fortney¹⁴, Lisa Kaltenegger¹⁵, Gary J. Melnick¹⁶, Stefanie N. Milam⁹, Desika Narayanan¹⁷, Deborah Padgett⁴, Klaus Pontoppidan⁵, Thomas Roellig¹³, Karin Sandstrom¹⁸, Kate Y. L. Su¹⁹, Joaquin Vieira²⁰, Edward Wright²¹, Jonas Zmuidzinas¹², Johannes Staguhn⁶,⁹, Kartik Sheth²², Dominic Benford²², Eric E. Mamajek⁴, Susan G. Neff⁹, Sean Carey², Denis Burgarella²³, Elvire De Beck²⁴, Maryvonne Gerin²⁵, Frank P. Helmich²⁶, S. Harvey Moseley⁹, Itsuki Sakon²⁷ and Martina C. Wiedner²⁵

¹Department of Physics, University of Connecticut, Storrs, CT, USA. ²Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA, USA. ³Department of Astronomy, University of Michigan, Ann Arbor, MI, USA. ⁴NASA Jet Propulsion Laboratory, Pasadena, CA, USA.

⁵Space Telescope Science Institute, Baltimore, MD, USA. ⁶Department of Physics & Astronomy, Johns Hopkins University, Baltimore, MD, USA. ⁷Department of Astronomy, University of Massachusetts, Amherst, MA, USA. ⁸Department of Physics & Astronomy, University of California, Irvine, CA, USA. ⁹NASA Goddard Space Flight Center, Greenbelt, MD, USA. ¹⁰Department of Physics & Astronomy, University of British Columbia, Vancouver, BC, Canada. ¹¹Department of Astronomy, University of Maryland, College Park, MD, USA. ¹²Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA, USA. ¹³NASA Ames Research Center, Moffett Field, CA, USA. ¹⁴Department of Astronomy & Astrophysics, University of California, Santa Cruz, CA, USA. ¹⁵Carl Sagan Institute at Cornell, Ithaca, NY, USA. ¹⁶Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA. ¹⁷Department of Astronomy, University of Florida, Gainesville, FL, USA. ¹⁸Department of Physics, University of California, San Diego, CA, USA. ¹⁹Steward Observatory, University of Arizona, Tucson, AZ, USA. ²⁰Department of Astronomy, University of Illinois, Urbana-Champaign, IL, USA. ²¹Department of Physics and Astronomy, University of California, Los Angeles, CA, USA. ²²Astrophysics Division, Science Mission Directorate, NASA Headquarters, Washington, DC, USA. ²³Laboratoire d'Astrophysique, University of Marseille, Marseille, France. ²⁴Department of Space, Earth and Environment, Chalmers Institute of Technology, Onsala Space Observatory, Onsala, Sweden.

²⁵Sorbonne Université, Observatoire de Paris, Université PSL, CNRS, Paris, France.

²⁶SRON Netherlands Institute for Space Research, Groningen, The Netherlands. ²⁷Department of Astronomy, University of Tokyo, Tokyo, Japan.

*e-mail: cara.battersby@uconn.edu

Published online: 1 August 2018
https://doi.org/10.1038/s41550-018-0540-y
References

1. Gillon, M. et al. *Nature* **533**, 221–224 (2016).

2. Berta-Thompson, Z. K. et al. *Astrophys. J.* **775**, 1–12 (2013).

3. Borucki, W. J. et al. *Science* **327**, 977–980 (2010).

4. de Wit, J. et al. *Nat. Astron.* **2**, 214–219 (2018).

5. Kaltengeger, L. *Annu. Rev. Astron. Astrophys.* **55**, 433–485 (2017).

6. van Dishoeck, E. F. et al. in *Protostars and Planets VI* (eds Beuther, H. et al.) 835–858 (Univ. Arizona Press, Tucson, 2014).

7. Stevenson, D. J. & Lunine, J. I. *Icarus* **75**, 146–155 (1998).

8. Bergin, E. A. et al. *Nature* **493**, 644–646 (2013).

9. Madau, P. & Dickinson, M. *Annu. Rev. Astron. Astrophys.* **52**, 415–486 (2014).