Origins Space Telescope: baseline mission concept

Abstract

The Origins Space Telescope will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did galaxies evolve from the earliest galactic systems to those found in the Universe today? How do habitable planets form? How common are life-bearing worlds? To answer these alluring questions, Origins will operate at mid-and far-infrared (IR) wavelengths and offer powerful spectroscopic instruments and sensitivity three orders of magnitude better than that of the Herschel Space Observatory, the largest telescope flown in space to date. We describe the baseline concept for Origins recommended to the 2020 US Decadal Survey in Astronomy and Astrophysics. The baseline design includes a 5.9-m diameter telescope cryocooled to 4.5 K and equipped with three scientific instruments. A mid-infrared instrument (Mid-Infrared Spectrometer and Camera Transit spectrometer) will measure the spectra of transiting exoplanets in the 2.8 to 20 μm wavelength range and offer unprecedented spectrophotometric precision, enabling definitive exoplanet biosignature detections. The far-IR imager polarimeter will be able to survey thousands of square degrees with broadband imaging at 50 and 250 μm. The Origins Survey Spectrometer will cover wavelengths from 25 to 588 μm, making wide-area and deep spectroscopic surveys with spectral resolving power R ∼ 300, and pointed observations at R ∼ 40;000 and 300,000 with selectable instrument modes. Origins was designed to minimize complexity. The architecture is similar to that of the Spitzer Space Telescope and requires very few deployments after launch, while the cryothermal system design leverages James Webb Space Telescope technology and experience. A combination of current-state-of-the-art cryocoolers and next-generation detector technology will enable Origins' natural background-limited sensitivity. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Origins Space Telescope: trades and decisions leading to the baseline mission concept

“…Finally, we used two approaches to derive a high-fidelity estimate of the Origins baseline mission cost. 11…”

“…To suppress the observatory's thermal self-emission and approach the natural astrophysical background photon noise level-essential to achieving Origins' science goals-the telescope's optical elements must be cooled to <6 K. 11 At wavelengths >200 μm, the background noise level is extremely sensitive to telescope temperature: 4 K is much better than 6 K. Past far-infrared missions, including Spitzer, were cooled with expendable cryogens, but that approach requires a large, massive cryostat and limits the life of the mission. Advances in cryocooler technology for JWST, Hitomi, and other missions enabled us to adopt mechanical cryocoolers rather than expendable cryogens for Origins.…”

“…If the decadal survey recommends Origins, the mission will enter pre-phase A, during which open questions will be brought to closure and the mission concept will be refined and optimized. Ultimately, the mission that flies will likely resemble the baseline mission concept, 11 but a cold JWST concept 30 will receive further consideration, as it would leverage existing ground support infrastructure and a proven design, once JWST is launched and commissioned. Even if the Spitzer-like architecture is adopted, design details can be expected to change in response to future studies.…”

“…This paper describes the STDT's key decisions, the rationale for those choices, and how they led through an exploratory design process to the Origins baseline mission concept, 11 which the STDT recommended to the 2020 Decadal Survey in written and oral reports in August and November 2019, respectively. To arrive at the baseline design, we studied two distinct mission concepts and descoped the second one, aiming to maximize science per dollar and hit a selfimposed cost target.…”

“…Origins baseline design details are summarized in a series of companion papers in this JATIS special section (see Ref. 11 and references therein). Readers who are not already familiar with the Origins baseline mission concept will find it helpful to read papers 10,11 before reading the rest of this paper. The paper is organized as follows.…”