Optical design for CETUS: A wide-field 1.5-m aperture UV payload being studied for a NASA probe class mission study

Robert A. Woodruff, William C. Danchi, Sara R. Heap, Tony Hull, Stephen E. Kendrick, Lloyd R. Purves, Michael S. Rhee, Eric Mentzell, Brian Fleming, Marty Valente, James Burge, Ben Lewis, Kelly Dodson, Greg Mehle, Matt Tomic

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


As part of a study funded by NASA headquarters, we are developing a probe-class mission concept called the Cosmic Evolution through UV Spectroscopy (CETUS). CETUS includes a 1.5-m aperture diameter telescope with a large field of view (FOV). CETUS includes three scientific instruments: a far ultraviolet (FUV) and near ultraviolet (NUV) imaging camera (CAM); a NUV multiobject spectrograph (MOS); and a dual-channel point/slit spectrograph (PSS) in the Lyman ultraviolet (LUV), FUV, and NUV spectral regions. The large FOV three-mirror anastigmatic (TMA) optical telescope assembly (OTA) simultaneously feeds the three separate scientific instruments. That is, the instruments view separate portions of the TMA image plane, enabling parallel operation by the three instruments. The field viewed by the MOS, whose design is based on an Offner-type spectrographic configuration to provide wide FOV correction, is actively configured to select and isolate numerous field sources using a next-generation micro-shutter array. The two-channel CAM design is also based on an Offner-like configuration. The PSS performs high spectral resolution spectroscopy on unresolved objects over the NUV region with spectral resolving power, R ∼ 40,000, in an echelle mode. The PSS also performs long-slit imaging spectroscopy at R ∼ 20,000 in the LUV and FUV spectral regions with two aberration-corrected, blazed, holographic gratings used in a Rowland-like configuration. The optical system also includes two fine guidance sensors, and wavefront sensors that sample numerous locations over the full OTA FOV. In-flight wavelength calibration is performed by a wavelength calibration system, and flat-fielding is also performed, both using in-flight calibration sources. We describe the current optical design of CETUS and the major trade studies leading to the design.

Original languageEnglish (US)
Article number024006
JournalJournal of Astronomical Telescopes, Instruments, and Systems
Issue number2
StatePublished - Apr 1 2019


  • Aberration-corrected Rowland spectrographs
  • Echelle spectrographs
  • Image error budgets
  • Imagers
  • Multiobject spectrographs
  • Optical design
  • Reflective telescopes
  • Space sensors
  • Ultraviolet sensors

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Control and Systems Engineering
  • Instrumentation
  • Astronomy and Astrophysics
  • Mechanical Engineering
  • Space and Planetary Science


Dive into the research topics of 'Optical design for CETUS: A wide-field 1.5-m aperture UV payload being studied for a NASA probe class mission study'. Together they form a unique fingerprint.

Cite this