Active telescope for UV-through-midIR space astronomy

We consider the scientific benefits and technical feasibility of a 6-m, non-deployed, cold space telescope mission concept, covering the ultraviolet, visible, near-infrared, and mid-infrared wavebands, for direct imaging of exoplanets and a broad range of astronomical investigations. The concept uses the largest practical aperture size that can be launched without deployment, for lower risk and cost. An innovative, rigid outer barrel and sunshield control temperature and stray light in a compact, Spitzer-like configuration that provides a 100-K telescope. Additional active and passive thermal features provide millikelvin temperature stability. The ultraviolet and visible instruments are based on the suite developed for the Habitable Exoplanet Observatory concept. The cold telescope enables the scientifically important addition of mid-infrared imaging and spectroscopy modes, providing background-limited imaging to 5 um wavelength. The telescope uses actively-controlled mirrors to compensate for cool-down aberrations, other optical uncertainties, and tolerances or errors that may occur in manufacturing, assembly, launch, and on-orbit operations. A starshade provides high-dynamic-range imaging and spectroscopy of exoplanets, potentially augmented by a coronagraph for exoplanet search and orbit measurement. Special attention has been paid to contamination control, assessing the feasibility of UV imaging with a cryogenic telescope. The paper will provide design details and assessment of scientific yield and technology readiness, while addressing real and perceived issues for a space telescope capable of covering this wide wavelength range.