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German Receiver for Astronomy at THz Frequencies - GREATModular dual-channel heterodyne receiver for high-resolution spectroscopy with Stratospheric Observatory for Infrared Astronomy (SOFIA)
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SOFIA Media Day - June 08, 2011
MPIfR KOSMA MPS
DLR-PF
R.Güsten
German Receiver for Astronomy at THz Frequencies ATM 1-5 THz, 14 km altitude
SOFIA Media Day - June 08, 2011
MPIfR KOSMA MPS
DLR-PF
R.Güsten
heterodyne receiver
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 !!
SOFIA Media Day - June 08, 2011
MPIfR KOSMA MPS
DLR-PF
R.Güsten
heterodyne principle
GREAT is a heterodyne spectrometer for FIR (THz) astronomy
Greek roots: hetero- "different", and dyn- "power" (cf. dynamis, dunamis)
• 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.
SOFIA Media Day - June 08, 2011
MPIfR KOSMA MPS
DLR-PF
R.Güsten
Far-Infrared spectroscopy ?
GREAT is a heterodyne spectrometer for FIR (THz) astronomy
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
extracted from www.sura.org
SOFIA Media Day - June 08, 2011
MPIfR KOSMA MPS
DLR-PF
R.Güsten
Why observe with SOFIA ?
In the stratosphere the atmosphere becomes transparent to most (not all) FIR
SOFIA Media Day - June 08, 2011
MPIfR KOSMA MPS
DLR-PF
R.Güsten
German REceiver for Astronomy at Terahertz frequencies
Channel Frequencies [THz] Astronomical lines of interest
low-frequency #1 1.25 – 1.50 [NII], CO(12-11), (13)
CO(13-12), HCN(17-16), H2D+
low-frequency #2 1.82 – 1.92 [CII], CO(16-15) mid-frequency 2.4 – 2.7 HD, OH(
23/2), CO(22-21),
(13)CO(23-22)
high-frequency 4.7 [OI]
SOFIA Media Day - June 08, 2011
MPIfR KOSMA MPS
DLR-PF
R.Güsten
Our first science flight
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.
Press release on April 07
SOFIA Media Day - June 08, 2011
MPIfR KOSMA MPS
DLR-PF
R.Güsten
GREAT dips into cradle of star formation
CO J=11-10
Image: Spitzer/GLIMPSE 8 µm
G5.89 :
a cluster of massive
stars in the making
Cloud collapse is
associated with
energetic outflows
that can be studied
with GREAT/SOFIA
SOFIA Media Day - June 08, 2011
MPIfR KOSMA MPS
DLR-PF
R.Güsten
The circum-nuclear disk in the GC
carbon monoxid (CO) in orbit around the central mass
GREAT will help constraining the
physical conditions of the gas
reservoir, feeding the nucleus
a massive gas disk is rotating around & feeding the black hole in the Galactic center
CO(11-10) observed with GREAT
SOFIA Media Day - June 08, 2011
MPIfR KOSMA MPS
DLR-PF
R.Güsten
… the next frontier: HD 2.7 THz
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)
SOFIA Media Day - June 08, 2011
MPIfR KOSMA MPS
DLR-PF
R.Güsten
Outlook and Ongoing Upgrades
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
SOFIA Media Day - June 08, 2011
MPIfR KOSMA MPS
DLR-PF
R.Güsten
the GREAT consortium
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
For more information: http://www.mpifr.de/div/submmtech/heterodyne/great/greatmain.html
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.