Concept Study of the Heterodyne Spectroscopy Instrument (HSI) for the Proposed Far-IR Spectroscopy Space Telescope (FIRSST)
Year: 2026
Type: article
Abstract: The Heterodyne Spectroscopy Instrument (HSI) is a focal plane array receiver (FPA) for the Far-IR Spectroscopy Space Telescope (FIRSST), a proposal submitted to NASA's APEX call. Though FIRSST was not selected for further study, the receiver design allowed us to quantitatively demonstrate that small (few to few tens of pixels) heterodyne FPAs are now feasible for space missions, can be built with high TRL components, are reliable and fit within the mass/volume/power constraints of medium to large missions. The design also identified the challenges and critical design considerations, in particular that great care needs to be taken to minimize the cryogenic heat load of the cryogenic IF amplifiers and to keep the power consumption of the spectrometer backends low. The HSI was designed primarily to study the trail of water from the Interstellar Medium (ISM) to planets and to observe the important low-lying transitions of water and its isotopes between 500 and 2000 GHz undetectable from the ground due to Earth's atmosphere. HSI has a spectral resolving power of up to 107 (0.03 km/s), ideal for kinematic studies or line tomography. HSI has six 5-pixel-arrays covering 3 frequency bands and 2 linear polarizations. The concept study showed that heterodyne array receivers such as HSI can be built today even for fast missions and that they are powerful and versatile instruments, with low-risk technology capable of opening up the THz sky at very high spectral resolving power for new discoveries.
Authors: Martina C. Wiedner, Andrey Baryshev, Paul Grimes, Victor Belitsky, Vincent Desmaris, Yan Delorme, Juan-Daniel Gallego, Cristina García-Miró, Uma Gorti, Paul Hartogh, Cornelia E. Honingh, Bernd Klein, Jean-Michel Krieg, Gary Melnick, Sebastiano Ligori, Boon-Kok Tan, Bertrand Thomas, Volker Tolls, Jeanne Treuttel, Jérôme Valentin, David L. Clements, Ray Blundell, Asantha Cooray, Meredith MacGregor, Ronald J. Vervack
Institutions: Centre National de la Recherche Scientifique, Université Paris Cité, Université Paris Sciences et Lettres, Observatoire de Paris, Sorbonne Université, Laboratoire d’Etudes du Rayonnement et de la Matière en Astrophysique et Atmosphères, University of Groningen, Smithsonian Institution, Smithsonian Astrophysical Observatory, Center for Astrophysics Harvard & Smithsonian, Chalmers University of Technology, Yebes Observatory, Search for Extraterrestrial Intelligence, Max Planck Institute for Solar System Research, Max Planck Society, Max Planck Institute for Radio Astronomy, Osservatorio Astrofisico di Torino, National Institute for Astrophysics, University of Oxford, Radiometer (Germany), Imperial College London, University of California, Irvine, Johns Hopkins University, Johns Hopkins University Applied Physics Laboratory
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7134820347