New 60-cm Radio Survey Telescope with the Sideband-Separating SIS Receiver for the 200 GHz Band

TL;DR

This paper reports the upgrade of a 60-cm radio telescope with a new sideband-separating SIS receiver, enabling simultaneous detection of molecular lines in the 200 GHz band, and demonstrates its effectiveness through successful astronomical observations.

Contribution

Introduction of a waveguide-type sideband-separating SIS mixer for the 200 GHz band, allowing simultaneous molecular line observations with improved noise performance.

Findings

Successful detection of CO emission lines in Orion KL.

First simultaneous 12CO and 13CO survey of the galactic plane.

Enhanced capability for large-scale molecular cloud mapping.

Abstract

We have upgraded the 60-cm radio survey telescope located in Nobeyama, Japan. We developed a new waveguide-type sideband-separating SIS mixer for the telescope, which enables the simultaneous detection of distinct molecular emission lines both in the upper and lower sidebands. Over the RF frequency range of 205-240 GHz, the single-sideband receiver noise temperatures of the new mixer are 40-100 K for the 4.0-8.0 GHz IF frequency band. The image rejection ratios are greater than 10 dB over the same range. For the dual IF signals obtained by the receiver, we have developed two sets of acousto-optical spectrometers and a telescope control system. Using the new telescope system, we successfully detected the 12CO (J=2-1) and 13CO (J=2-1) emission lines simultaneously toward Orion KL in 2005 March. Using the waveguide-type sideband-separating SIS mixer for the 200 GHz band, we have initiated the first simultaneous 12CO (J=2-1) and 13CO (J=2-1) survey of the galactic plane as well as large-scale mapping observations of nearby molecular clouds.