German Receiver for Astronomy at THz Frequencies - GREAT Modular dual-channel heterodyne receiver for high-resolution spectroscopy with Stratospheric Observatory for Infrared Astronomy (SOFIA)

1. MPIfR
KOSMA
MPS
DLR-PF
ATM 1-5 THz, 14 km altitude
German Receiver for Astronomy at THz Frequencies
R.Güsten SOFIA Media Day - June 08, 2011

2. MPIfR
heterodyne receiver KOSMA
MPS
DLR-PF
GREAT is a heterodyne spectrometer for FIR (THz) astronomy
• as a spectrometer, GREAT analyses the frequency information carried
in the astronomical signal.
 much as you tune your radio to the frequency of your favorite station, we
operate GREAT at selected frequencies of astronomical interests
!! all molecules, atoms have their characteristic frequency footprints !!
R.Güsten SOFIA Media Day - June 08, 2011

3. MPIfR
heterodyne principle KOSMA
MPS
DLR-PF
GREAT is a heterodyne spectrometer for FIR (THz) astronomy
• as a spectrometer, GREAT analyses the frequency information carried
in the astronomical signal.
 much as you tune your radio to the frequency of your favorite channel, we
operate GREAT at selected frequencies of astronomical interests
!! all molecules, atoms have their characteristic frequency footprint !!
• switching on your radio, you listen to the „heterodyne principle“
which describes the generation of new frequencies by mixing two frequencies
 applied to GREAT, this describes the down-
conversion from THz to GHz frequencies,
where the signal processing takes place.
Greek roots: hetero- "different", and dyn- "power" (cf. dynamis, dunamis)
R.Güsten SOFIA Media Day - June 08, 2011

4. MPIfR
Far-Infrared spectroscopy ? KOSMA
MPS
DLR-PF
GREAT is a heterodyne spectrometer for FIR (THz) astronomy
extracted from www.sura.org
The FIR is the scientifically most promising, but so far widely underutilized
part of the electromagnetic spectrum
FIR is terra incognita because:
• lack of suitable technologies (but the „terahertz gap“ is slowly closing..)
• Earth‘s atmosphere efficiently absorbs THz photons from space. Science must be
performed from space or from high-flying platforms: SOFIA
R.Güsten SOFIA Media Day - June 08, 2011

5. MPIfR
Why observe with SOFIA ? KOSMA
MPS
DLR-PF
In the stratosphere the atmosphere becomes transparent to most (not all) FIR
R.Güsten SOFIA Media Day - June 08, 2011

6. MPIfR
KOSMA
MPS
German REceiver for Astronomy at Terahertz frequencies DLR-PF
Channel Frequencies [THz] Astronomical lines of interest
(13) +
low-frequency #1 1.25 – 1.50 [NII], CO(12-11), CO(13-12), HCN(17-16), H2D
low-frequency #2 1.82 – 1.92 [CII], CO(16-15)
2.4 – 2.7 HD, OH( 3/2), CO(22-21), CO(23-22)
2 (13)
mid-frequency
high-frequency  4.7 [OI]
R.Güsten SOFIA Media Day - June 08, 2011

7. MPIfR
KOSMA
Our first science flight MPS
DLR-PF
Press release on April 07
GREAT observed the fine-structure line of ionized carbon [CII] at 1.9 THz
and of warm carbon monoxid CO(13-12) at 1.5 THz towards M17SW, a
molecular cloud prominently forming new massive stars.
R.Güsten SOFIA Media Day - June 08, 2011

8. MPIfR
KOSMA
GREAT dips into cradle of star formation MPS
DLR-PF
CO J=11-10 G5.89 :
a cluster of massive
stars in the making
Cloud collapse is
associated with
energetic outflows
that can be studied
with GREAT/SOFIA
Image: Spitzer/GLIMPSE 8 µm
R.Güsten SOFIA Media Day - June 08, 2011

9. MPIfR
KOSMA
The circum-nuclear disk in the GC MPS
DLR-PF
a massive gas disk is rotating around & feeding the black hole in the Galactic center
CO(11-10) observed with GREAT
GREAT will help constraining the
physical conditions of the gas
carbon monoxid (CO) in orbit around the central mass reservoir, feeding the nucleus
R.Güsten SOFIA Media Day - June 08, 2011

10. MPIfR
… the next frontier: HD 2.7 THz
KOSMA
MPS
DLR-PF
While closing the THz gap! – we push GREAT into new territories, namely
spectroscopy beyond 2 THz
As we speak, our novel 2.7 THz detector is commissioned in the lab (tour)
Why is this so exciting?
 because observations of hydrogen deuteride HD become possible
Well…
 but: deuterium is only produced in the Big Bang, therefore does
serve as chemical clock of the evolution of the universe
Our chemical networks tell us that HD is likely to be the
 best tracer of the cold ISM (molecular hydrogen is not observable)
 best tracer of the late star forming process (latest freeze-out)
R.Güsten SOFIA Media Day - June 08, 2011

11. MPIfR
KOSMA
Outlook and Ongoing Upgrades MPS
DLR-PF
 while looking forward to our basic science flights in July & September
 we are preparing for the next frequency extension: H-channel at 4.6 THz ([OI])
 we have launched the instrument’s first major upgrade into a compact array:
upGREAT
to operate simultaneously 14 pixels at 1.9-2.5 THz and 7 pixels at 4.7 THz
R.Güsten SOFIA Media Day - June 08, 2011

12. MPIfR
KOSMA
the GREAT consortium MPS
DLR-PF
GREAT is developed by the Max-Planck-Institut für Radioastronomie and the Universität zu Köln, in collabo-
ration with the MPI for Solar System Research and the DLR Institute for Planetary Research, financed by the
participating institutes, the Max-Planck-Society and Deutsche Forschungsgemeinschaft, supported by DLR.
Principal Investigator Project Management Co-Investigators
Rolf Güsten Stefan Heyminck (MPIfR) Jürgen Stutzki (KOSMA)
MPI für Radioastronomie Paul Hartogh (MPS)
Auf dem Hügel 69 Heinz-Wilhelm Hübers (DLR-PF)
53121 Bonn, Germany
rguesten@mpifr.de
For more information: http://www.mpifr.de/div/submmtech/heterodyne/great/greatmain.html
R.Güsten SOFIA Media Day - June 08, 2011