Letter to the Editor

The first-light APEX submillimeter heterodyne instrument FLASH

¹ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany e-mail: heyminck@mpifr-bonn.mpg.de
² SRON Netherlands Institute for Space Research, Postbus 800, 9700 AV Groningen, The Netherlands
³ I. Physikalisches Institut der Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany

Received: 11 April 2006
Accepted: 16 May 2006

Abstract

Development of a dual-color heterodyne instrument for use with the Atacama Pathfinder EXperiment. Commissioning of the APEX began in mid 2004, and regular science operation has been performed since July 2005. Verification of the telescope required a dual-channel receiver operating at (short) submillimeter wavelengths. It was important for the characterization of the telescope to observe at the highest possible frequency at which routine observations can be performed. For pointing, focus, and tracking verification (simultaneous) operation at lower frequencies was requested. We developed FLASH operating on two channels simultaneously – at orthogonal polarizations – in the 460 GHz and 810 GHz atmospheric windows. The system performs with a wide tuning range (420–500 GHz, 780–880 GHz) and intermediate frequency bandwidths of 2 and 4 GHz, respectively. As backends, we operate two fast-Fourier transform spectrometers (FFTS) with  GHz bandwidth each and a maximum of 16 384 channels. The receiver has been in continuous operation since June 2004. While first used for the telescope commissioning, since the middle of last year the instrument has served as the high-frequency workhorse on APEX. Simultaneous observations of the rotational transitions of warm carbon monoxide (–3 and –6) and of the two fine-structure lines of atomic carbon are scientifically attractive. FLASH is a principal investigator instrument, available to the APEX-user community on a collaborative basis with MPIfR. A state-of-the-art dual-channel heterodyne instrument has been developed, which made timely commissioning of the APEX possible. Most of the scientific results presented in this special issue rely on data derived with FLASH.