Workshop on Progress in Theoretical
and Observational Cosmology
Nov. 7-9, 2011, IHEP, Beijing
Dome A THz Astronomy
Ji Yang
Purple Mountain Observatory,
Key Laboratory for Radio Astronomy,
Chinese Academy of Sciences,
Nanjing 210008, China
jiyang@pmo.ac.cn
Outlines
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Science Drive and Dome A THz Conditions
Dome A 5m THz Telescope Concept
Challenges to the THz Development
Technological Availability & International
Collaboration
Major Challenges in Astronomy
End of Dark Age and Formation of
First Generation Stars
Ecology in the Universe: ISM, Stars, Galaxies
Precision Cosmology dominated by
Dark Energy & Dark Matter
Origin of Planetary Systems & Life
THz Wavelengths: New Windows for
Observing the Universe
 Cosmic SED peak at FIR/THz：THz as an important tracers
to the distribution, structure, and motion at different levels.
 Intensive lines carrying important information on the origin of
the universe, celestial bodies, and life.
Dole, H. et al. 2006; Driver, et al. 2008
Credit: Herschel Team
World Trends and Challenges in Ground based
Astronomy (Optical, NIR, THZ)
• World trends for large fields of view, high
sensitivities, high resolution and multiwavelength coverage；
• Finding best sites for large facilities to achieve
the best performance；
• Or, to put telescopes into space, under the cost
of money and technological risks!
• Difficulty in finding world-class sites for
optical/NIR/THz within China;
• Dome A as an potential opportunity for China
was widely recognized.
5
Dome A: The Site
 Dome A，altitude 4100m (60km10km), a plateau of small
fluctuation。Lowest Temp -83ºC。
 Site surveys under Panda Program suggest ：Dome A is a
promising site for astronomy, particularly in THz & IR.
 2005.1.18 Chinese inland
expedition team reached
Dome A.
 Astronomy follows on from
2007/2008 , by the 24th
Chinese Antarctic Expedition)
The Pre-HEAT Collaboration
(The High Elevation Antarctic Terahertz Telescope)
Pre-HEAT measured the transparency of the sky above Dome A at
submillimeter wavelengths using a high frequency heterodyne
receiver at 0.66 THz. Installed by Chinese 25th antarctic expedition
team and data were collected from Jan 24, 2008.
Major Collaboration Institutes:
University of Arizona, Exeter University, University of New South Wales,
Polar Research Institute of China, & Purple Mountain Observatory.
The Pre-HEAT Measurements
Mauna Kea at Hawaii
Stablebest
over25%
several
weather
weeks
at !!!
Mauna Kea
国际大科学工程ALMA台址
Dome A (partial time)
Yang, H. et al. 2010, PASP, 122, 490
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Dome A (4000m, -83C)
Measurement（2007-2008, Pre-HEAT
The best site ever knew
New THz windows over 150-800 m
350-200 m
windows
Measurement of Atmospheric THz Transmission
by FTS (Shi, S.-c., et al. , 2011, in preparation)
In 2009，a FIR/THz FTS was developed & installed to measure
the atmospheric transmission over 0.75-15 THz, under the
collaboration among PMO, CfA, and NAOJ, with remote operation
support from NSWU.
The results，combined with 660GHz radiometer measurement by
Pre-HEAT，strongly suggest that Dome A is a unique site for
ground-based THz observations.
 THz facilities for 200-350 micron windows should be planned.
Uniqueness of Dome A Astronomy
 Site：Excellent
 Science： Unique & Competitive
 Facility: Synergy in Wavelengths
 Technology：Feasible
Targeted Science Drivers
 Time Domain- The Legacy of a Dynamic Universe
 Large FOV+High Resolution- Revealing the Dark Universe
 New THz/IR Window- Star Formation, Young Galaxies, Early
Universe, & Origin of Celestial Life
Concepts for Dome A Observatory Phase I
• Taking the advantage of Dome A superior site conditions to
build optical/IR, THz observing facilities, and to build efficient
international collaborations;
• Two telescopes with competitive observing capabilities,
proposed as National Mega-Science Facilities;
• Major science goals on dark energy and dark matter, exoplanets, time-domain sciences, formation & evolution of stars
and galaxies;
• Self-supported observing mode under remote control;
• On-site bulk data storage, partially send back for timely
analysis and follow-up observations；
• Instrument maintenance/upgrade and data retrieval by
summer traverse.
Dome A Observatory: A Mega-Science Facility
Proposed for 2011-2015 Construction
• 2.5m Optical/NIR Telescope
• 5m THz Telescope
• Antarctic Support Platform
• Transportation & Logistics
• On-Site Assembly
• Remote Operation
12
Dome A Observatory Development:
A Roadmap
20062008
Site Survey &
Small Telescope
20092011
+Site Testing &
Middle-size
Telescope
20112015
Dome A
Observatory
Phase I
20162025
Dome A
Observatory
Phase II
5m THz
DATE5
2.5m Opt/NIR
KDUST
15m THz
6-8m
Opt/NIR
Dome A THz Explorer（DATE5）
DATE5 System Diagram
DATE5 Toy Model
Ant Optics
Ant
Relay
Optics
THz Receivers
THz Mixers
（Band1 &2）
IF Proc.
（6 chs）
THz Digit LO
（Band1 &2）
Back
end
Spec
tral
Proc.
Control & DAC
DATE5 Specs
Optics
Symmetric Cassegrain
Main Reflector
5m paraboloid
Surface Accuracy
10m (rms)
Pointing
2“ (rms)
FoV
10′×10′ (350m), 5′×5′（200m）
Receiver
Superconducting Mixer，Nb/NbN SIS&HEB
Wavelength
350m×6, 200m×2
Power Consumption
<= 3 kW
The Extreme Site Conditions as The Major
Challenges to Dome A THz Development
• High altitude: 4000m;
• Low pressure: 570 hPa;
• Extremely low temperature & large temp difference:
-58.4 C , (-10 C ~ -83 C);
• Harsh weather conditions： snow, ice, radiation;
• Transportation: complicated
• Installation/testing：limited working time/facilities;
• Operation: low-bandwidth communication;
• Logistics: limited summer support, no winter-over.
THz Astronomy Development at PMO
1980s
1995-
13.7m-100GHz, Delignha
POST 30cm-492GHz
2005-2009 ALMA
2000-2005
SMA Collaboration（0.20.9THz，Mauna Kea/Hawaii）
Dome A THz Development
2006-
The Superconducting Spectroscopic Array (SSAR):
A mm-wave multi-beam receiver recently finished for
Delingha 14m Telescope
Sideband Separation SIS
3x3 beams, 18 IFs
All digital System
DATE5: Conceptual Studies on
Ant & Relay Optics (Lou, Z. et al. 2011)
Roof mirror partition scheme for
dividing the incoming beam into
receivers of two bands
Far-field distribution for Band1(14) & Band2(12)
beams, calculated by Physical Optics through
numerical methods based on GPU
Focal plane distribution for
Band 1&2, calculated by GO
DATE5 Prototype SIS Mixers
Developed by Shi, S. et al & International Collaborations
Original design initiated
from 790-850GHz band
design during ALMA
R&D collaborations
1.3THz NbN SIS mixer chip & measured I-V curve
1.0
Spectral response
Air transmission
Beam splitter
0.8
Band2 HEB mixer prototype
chip & measured FTS
Response
FTS response
fmax=15 THz
fres=15 GHz
0.6
0.4
0.2
0.0
0
1
2
Freq. (THz)
3
Prototype 2GHz Digital FFT Spectrometer based on FPGA
(Yang, J. et al., 2011, under development)
real-time pipeline FFT algorithm
based on FPGA, 32k points
 Bandwidth：2GHz
Function diagram for 2GHz real-time
digital FFT spectrometer, as a
prototype back-end signal processing
solution to the Dome A THz telescope
 Freq Resolution：61kHz
 Dynamic Range：≥ 30dB
 Stability：≥ 1000s
Requirement for THz Focal Plane Imaging Detectors
Call for International Collaboration
Herschel Blue Array 2048 pixels
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background limit
NEP  10-16 W/ Hz at Dome A
Full sampling at Focal Plane
Undergoing Collaboration with world institutes
Demo device available with next few years
Summary
• Stimulated by Polar Research activities, the site surveys at
Dome A demonstrate its excellent observing conditions for
ground-based astronomy;
• Small-scale instruments have been used at Dome A for
continuing site survey and astronomical observations;
• Dome A was selected as one of the major goals of
development for Chinese astronomy for the next decade;
Major Instruments, including 5m THz telescope & 2.5m
Opt/IR telescope, have been proposed;
• Dedicated teams are organized to study the 5m telescope
and key technologies on receiver systems;
• International collaboration has been successful and should
be encouraged in future for Dome A THz astronomy.
Acknowledgements
• Part of the materials in this talk was contributed by Chinese Center for
Antarctic Astronomy (CCAA) and The International Partner Group on
Cosmic Star Formation.
CCAA is a center jointly initiated by Chinese institutes and universities,
including Purple Mountain Observatory, Nanjing Institute of
Astronomical Optics and Technology, Polar Research Institute of China,
Polar Research Institute of China, National Astronomical Observatories
of Chinese Academy of Sciences, and Chinese universities. CCAA is
based at Purple Mountain Observatory, Chinese Academy of Sciences.
The International Partner Group on Cosmic Star Formation is a
program supported by NSFC and CAS and affiliated to Purple Mountain
Observatory.
• Materials of this talk are also based on international collaborators
including UNSW, UoA, CfA, NAOJ, etc.
Antarctic Support Platforms for Remote Operation :
Joint Developments
2007-2009 AUS、CHN、US、UK
Joint PLATO
Function：To supply power, communication, remote operation and data storage/
manipulation capabilities.
Results：PLATO operated over 204 days
in 2008，and full winter over 2009-2010。
New design of ASP by PMO-SEU: higher
power output & larger data storage, testing
in Tibet in 2010 summer.
2010 PMO-SEU Joint ASP