Siegel der Universität

Universität zu Köln
Mathematisch-Naturwissenschaftliche Fakultät
Fachgruppe Physik

I. Physikalisches Institut

GREAT Far-IR Spectrometer Opens Window to New Science Opportunities

Printer-friendly versionPDF version

With successful commissioning of its high-frequency channel, the GREAT (German Receiver for Astronomy at Terahertz Frequencies) far-infrared spectrometer onboard SOFIA is ready to explore new realms.

Figure 1: First-light observations by the GREAT H-channel on SOFIA: map of planetary nebula NGC 7027 in the neutral oxygen emission line at 63 microns. The effective angular resolution is indicated by the gray circle at lower left. (Credit: GREAT Consortium)
Figure 2: High-resolution spectrum of OI toward the center of NGC 7027 showing complex velocity structure in the outflow. (Credit: GREAT Consortium)

The new so-called H-channel was first tested during SOFIA flights on May 5, 6, and 7, and confirmed to be working perfectly. It is based upon an extremely sensitive superconducting detector, developed and built at KOSMA, I. Physikalisches Institut, University of Cologne and a novel terahertz laser, a so-called quantum cascade laser. With that receiver added, the GREAT instrument is now capable of high-resolution spectroscopy of astrophysically important lines of atomic neutral oxygen [OI] at a wavelength of 63 μm ( frequency of 4.74 TeraHertz).

First-light spectra were obtained towards planetary nebula NGC 7027 (Figure 1). That nebula is an expanding bubble of gas expelled by a dying star with approximately the mass of our Sun, 3,000 light-years away in the constellation of Cygnus. The nebula has been extensively studied at other wavelengths, but only GREAT can resolve the velocities of the expanding envelope in the OI line. The spectrum (Figure 2) represents only 2 minutes of integration, illustrating the superb sensitivity of the GREAT instrument carried into the stratosphere by SOFIA.

GREAT is a Principal Investigator-class instrument for SOFIA, developed and maintained by the Max Planck Institute for Radio Astronomy (PI: Rolf Guesten) and KOSMA at the University of Cologne (Co-I: Juergen Stutzki), in collaboration with the DLR Institute of Planetary Research (Co-I: Heinz-Wilhelm Huebers) and the Max Planck Institute for Solar System Research (Co-I: Paul Hartogh).

SOFIA is a joint project of NASA and the German Aerospace Center (DLR). The aircraft is based at NASA Armstrong Flight Research Center that manages the program. NASA Ames Research Center at Moffett Field, Calif., manages the SOFIA science and mission operations in cooperation with the Universities Space Research Association (USRA) headquartered in Columbia, Md., and the German SOFIA Institute (DSI) at the University of Stuttgart.

For more information about SOFIA, visit:

For information about SOFIA's science mission, visit:

For information about GREAT, visit:


(fsc 2014-06-11)