Name of Instrument: CASIMIR - CAltech Submillimeter Interstellar Medium Investigations Receiver

Instrument type: Heterodyne Spectrometer, 250-600 microns

Principal Investigator: J. Zmuidzinas

The NASA Stratospheric Observatory for Infrared Astronomy (SOFIA) Program made a programmatic decision to cease the science instrument development of CASIMIR by the end of December 2010. CASIMIR, Caltech Airborne Submillimeter Interstellar Medium Investigations Receiver, was a planned high-resolution heterodyne spectrometer to have operated in five bands between 500 and 1500 GHz. The decision to withdraw CASIMIR from the suite of first-generation SOFIA science instruments was motivated by budget pressures and the science contributions from current and planned high-resolution submillimeter spectrometers on other facilities. High resolution spectroscopy remains an important priority for SOFIA, and the ongoing rapid advancements in technology may make an advanced heterodyne spectrometer a compelling option in the future.

Scientific/Technical Abstract

CASIMIR will be a sensitive submillimeter and far-infrared heterodyne receiver for SOFIA. The receiver will use sensitive superconducting mixers, including both tunnel junction (SIS) and hot electron bolometers (HEB). The double-sideband receiver noise temperatures are projected to be 4-10 times the quantum limit. The local oscillators will be continuously tunable, and will consist of Gunn oscillators or HEMT power amplifiers followed by frequency multipliers.

Our goal is to cover the 500-2100 GHz frequency range in seven bands: SIS mixers in four bands up to 1200 GHz, and HEB mixers in three bands covering 1200-2100 GHz. Up to four of these frequency bands could be selected for use on a given flight; if necessary, the selection of frequency bands could be changed between flights. The HEB mixers will not be available at first light on SOFIA. The receiver will have an intermediate-frequency (IF) bandwidth of 4 GHz, which will be processed by a high resolution backend spectrometer (most likely an acousto-optic spectrometer with 1 MHz resolution), as well as a low resolution (30 MHz) analog correlator.

This instrument will be used to study a wide range of astrophysical problems ranging from the evolution of galaxies to the birth and death of stars.