Optical Instrument Thermal Control on the Large Ultraviolet/Optical/Infrared Surveyor

The Large Ultraviolet/Optical/Infrared Surveyor (LUVOIR) is a multi-wavelength observatory commissioned by NASA as one of four large mission concept studies for the Astro2020 Decadal Survey. Two concepts are under study which bound a range of cost, risk, and scientific return: an 8-meter diameter unobscured segmented aperture primary mirror and a 15-meter segmented aperture primary mirror. Each concept carries with it an accompanying suite of instruments. The Extreme Coronagraph for Living Planetary Systems (ECLIPS) is a near-ultraviolet (NUV) / optical / near-infrared (NIR) coronagraph; the LUVOIR Ultraviolet Multi-object Spectrograph (LUMOS) provides multi-object imaging spectroscopy in the 100-400 nanometer ultraviolet (UV) range; and the High Definition Imager (HDI) is a wide field-of-view near-UV / optical / near-IR camera that can also perform astrometry. The 15-meter concept also contains an additional instrument, Pollux, which is a high-resolution UV spectro-polarimeter. While the observatory is nominally at a 270 Kelvin operational temperature, the requirements of imaging in both IR and UV require separate detectors operating at different temperature regimes, each with stringent thermal stability requirements. The change in observatory size requires two distinct thermal designs per instrument. In this current work, the thermal architecture is presented for each instrument suite. We describe here the efforts made to achieve the target operational temperatures and stabilities with passive thermal control methods. Additional discussion will focus on how these instrument thermal designs impact the overall system-level architecture of the observatory and indicate the thermal challenges for hardware implementation

The Large UV/Optical/Infrared Surveyor Decadal Mission Concept Thermal System Architecture

The Large Ultraviolet/Optical/Infrared (LUVOIR) Surveyor is one of four large strategic mission concept studies commissioned by NASA for the 2020 Decadal Survey in Astronomy and Astrophysics. Slated for launch to the second Lagrange point (L2) in the mid-to-late 2030s, LUVOIR seeks to directly image habitable exoplanets around sun-like stars, characterize their atmospheric and surface composition, and search for biosignatures, as well as study a large array of astrophysics goals including galaxy formation and evolution. Two observatory architectures are currently being considered which bound the trade-off between cost, risk, and scientific return: a 15-meter diameter segmented aperture primary mirror in a three-mirror anastigmat configuration, and an 8-meter diameter unobscured segmented aperture design. To achieve its science objectives, both architectures require milli-Kelvin level thermal stability over the optics, structural components, and interfaces to attain picometer wavefront RMS stability. A 270 Kelvin operational temperature was chosen to balance the ability to perform science in the near-infrared band and the desire to maintain the structure at a temperature with favorable material properties and lower contamination accumulation. This paper will focus on the system-level thermal designs of both LUVOIR observatory architectures. It will detail the various thermal control methods used in each of the major components - the optical telescope assembly, the spacecraft bus, the sunshade, and the suite of accompanying instruments - as well as provide a comprehensive overview of the analysis and justification for each design decision. It will additionally discuss any critical thermal challenges faced by the engineering team should either architecture be prioritized by the Astro2020 Decadal Survey process to proceed as the next large strategic mission for development

The Large UV/Optical/Infrared Surveyor (LUVOIR): Decadal Mission Concept Study Update

In preparation for the 2020 Decadal Survey in Astronomy and Astrophysics, NASA commissioned the study of four large mission concepts: the Large UV/Optical/Infrared Surveyor (LUVOIR), the Habitable Exoplanet Imager (HabEx), the far-infrared surveyor Origins Space Telescope (OST), and the X-ray surveyor Lynx. The LUVOIR Science and Technology Definition Team (STDT) has identified a broad range of science objectives for LUVOIR that include the direct imaging and spectral characterization of habitable exoplanets around sun-like stars, the study of galaxy formation and evolution, the exchange of matter between galaxies, star and planet formation, and the remote sensing of Solar System objects. The LUVOIR Study Office, located at NASA's Goddard Space Flight Center (GSFC), is developing two mission concepts to achieve the science objectives. LUVOIR-A is a 15-meter segmented-aperture observatory that would be launched in an 8.4-m extended fairing on the Space Launch System (SLS) Block 2 configuration. LUVOIR-B is an 8-meter unobscured segmented aperture telescope that fits in a smaller, conventional 5-meter fairing, but still requires the lift capacity of the SLS Block 1B Cargo vehicle. Both concepts include a suite of serviceable instruments: the Extreme Coronagraph for Living Planetary Systems (ECLIPS), an optical/near-infrared coronagraph capable of delivering 10 (sup minus10) contrast at inner working angles as small as 2 lambda divided by D; the LUVOIR UV Multi-object Spectrograph (LUMOS), which will provide low- and medium-resolution UV (100-400 nanometer) multi-object imaging spectroscopy in addition to far-UV imaging; the High Definition Imager (HDI), a high-resolution wide-field-of-view NUV-Optical-NIR imager. LUVOIR-A also has a fourth instrument, Pollux, a high-resolution UV spectro-polarimeter being contributed by Centre National d'Etudes Spatiales (CNES). This paper provides an overview of the LUVIOR science objectives, design drivers, and mission concepts

The Large UV/Optical/Infrared Surveyor (LUVOIR): Decadal Mission Study Update

NASA commissioned the study of four large mission concepts, including the Large Ultraviolet / Optical / Infrared (LUVOIR) Surveyor, to be evaluated by the 2020 Decadal Survey in Astrophysics. In response, the Science and Technology Definition Team (STDT) identified a broad range of science objectives for LUVOIR that include the direct imaging and spectral characterization of habitable exoplanets around sun-like stars, the study of galaxy formation and evolution, the exchange of matter between galaxies, star and planet formation, and the remote sensing of Solar System objects. To meet these objectives, the LUVOIR Study Office, located at NASA's Goddard Space Flight Center (GSFC), completed the first design iteration of a 15-m segmented-aperture observatory that would be launched by the Space Launch System (SLS) Block 2 configuration. The observatory includes four serviceable instruments: the Extreme Coronagraph for Living Planetary Systems (ECLIPS), an optical / near-infrared coronagraph capable of delivering 10(exp -10) contrast at inner working angles as small as 2 lambda/D; the LUVOIR UV Multi-object Spectrograph (LUMOS), which will provide low- and medium-resolution UV (100 - 400 nm) multi-object imaging spectroscopy in addition to far-UV imaging; the High Definition Imager (HDI), a high-resolution wide-field-of-view NUV-Optical-NIR imager; and Pollux, a high-resolution UV spectro-polarimeter being contributed by Centre National d'Etudes Spatiales (CNES). The study team has executed a second design iteration to further improve upon the 15-m concept, while simultaneously studying an 8-m concept. In these proceedings, we provide an update on these two architectures

Optical Instrument Thermal Control on the Large Ultraviolet/Optical/Infrared Surveyor

The Large Ultraviolet/Optical/Infrared Surveyor (LUVOIR) is a multi-wavelength observatory commissioned by NASA as one of four large mission concept studies for the Astro2020 Decadal Survey. Two concepts are under study which bound a range of cost, risk, and scientific return: an 8-meter diameter unobscured segmented aperture primary mirror and a 15-meter segmented aperture primary mirror. Each concept carries with it an accompanying suite of instruments. The Extreme Coronagraph for Living Planetary Systems (ECLIPS) is a near-ultraviolet (NUV) / optical / near-infrared (NIR) coronagraph; the LUVOIR Ultraviolet Multi-object Spectrograph (LUMOS) provides multi-object imaging spectroscopy in the 100-400 nanometer ultraviolet (UV) range; and the High Definition Imager (HDI) is a wide field-of-view near-UV / optical / near-IR camera that can also perform astrometry. The 15-meter concept also contains an additional instrument, Pollux, which is a high-resolution UV spectro-polarimeter. While the observatory is nominally at a 270 Kelvin operational temperature, the requirements of imaging in both IR and UV require separate detectors operating at different temperature regimes, each with stringent thermal stability requirements. The change in observatory size requires two distinct thermal designs per instrument. In this current work, the thermal architecture is presented for each instrument suite. We describe here the efforts made to achieve the target operational temperatures and stabilities with passive thermal control methods. Additional discussion will focus on how these instrument thermal designs impact the overall system-level architecture of the observatory and indicate the thermal challenges for hardware implementation