CASIMIR: a submillimeter heterodyne spectrometer for SOFIA

Abstract

The CAltech Submillimeter Interstellar Medium Investigations Receiver (CASIMIR) is a multichannel, heterodyne spectrometer being developed for the Stratospheric Observatory for Infrared Astronomy (SOFIA). It has a very high resolution, up to a million, over the submillimeter and far-infrared wavelength range of 150 to 600 jim, or 2.0 to 0.5 THz. CASIMIR is extremely well suited to the investigation of both the galactic and extragalactic warm, approximately 100 K, interstellar medium. A combination of advanced 515 and Hot Electron Bolometers (HEB) receivers will be used to cover this frequency range with very high sensitivity. CASIMIR will use only solid state local oscillators, with quasioptical coupling to the mixers. We present a description of the instrument and its capabilities, including detailed discussions of the receivers, local oscillators and IF systems.

Low Noise 1 THz–1.4 THz Mixers Using Nb/Al-AlN/NbTiN SIS Junctions

“…The receiver DSB noise temperature with the developed 1.2 THz band SIS mixer is as low as 450 K . The 1.2 THz receiver noise corrected for the loss in the LO coupler is 330 K, about 6 . The receiver with a 1.4 THz SIS mixer has a similar performance as the 1.2 THz mixer, although limited by the level of available LO power.…”

“…In our work the main goal was to study the feasibility of the low noise 1-1.4 THz receivers using the newly developed low loss THz circuit and SIS junction technology. This work is part of an effort in the development Caltech Airborne Submillimeter Interstellar Medium Investigations Receiver (CASIMIR) designed for SOFIA [6] and the 1.2 THz band of the HIFI (Heterodyne Instrument for the Far-Infrared) of the Hershel Space Observatory (HSO) [7].…”

Superconducting detectors and mixers for millimeter and submillimeter astrophysics

“…Water is of course a particularly interesting species to study. Understandably, the earth's atmosphere is opaque at the rotational transition frequencies of water [63], so observations of interstellar water generally require airborne [32], [64] or space [31], [65], [66] observatories.…”

SOFIA: The Stratospheric Observatory for Infrared Astronomy

“…Its scientific aims are the study of the warm interstellar medium in the Galaxy and external galaxies, heated by shock waves and UV radiation often associated with star formation. In addition, CASIMIR will cover many ground state rotational transitions of light hydrides, which are not observable from the ground and thus will be accessible only with Herschel and SOFIA (Edgar & Zmuidzinas 2000).…”