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

Workshop on Progress in Theoretical and Observational CosmologyNov. 7-9, 2011, IHEP, Beijing

Outlines

• Science Drive and Dome A THz Conditions• Dome A 5m THz Telescope Concept• Challenges to the THz Development• Technological Availability & International

Collaboration

Origin of Planetary Systems & LifeEcology in the Universe: ISM, Stars, Galaxies

Precision Cosmology dominated by Dark Energy & Dark Matter

Major Challenges in Astronomy

End of Dark Age and Formation of First Generation Stars

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 multi-wavelength 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.

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Dome A ， altitude 4100m (60km10km), 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.

Dome A: The Site

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.

Dome A (4000m, -83Dome A (4000m, -83C)C) MeasurementMeasurement （（ 2007-2008, Pre-2007-2008, Pre-

HEATHEAT The best site ever knewThe best site ever knew New THz windows over 150-800 New THz windows over 150-800 m m

The Pre-HEAT Measurements

Stable over several weeks !!!best 25% weather at Mauna Kea

国际大科学工程 ALMA台址

Dome A (partial time)

Mauna Kea at Hawaii

Yang, H. et al. 2010, PASP, 122, 490

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, exo-planets, 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

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Dome A Observatory Development: A Roadmap

2006-2008

Site Survey & Small Telescope

2009-2011

2011-2015

2016-2025

+Site Testing & Middle-size Telescope

Dome A Observatory Phase I

Dome A Observatory Phase II

2.5m Opt/NIRKDUST

6-8mOpt/NIR

5m THzDATE5

15m THz

Dome A THz Explorer （ DATE5）

DATE5 Toy Model

AntRelayOptics

Ant Optics THz Receivers

THz Mixers （ Band1

&2）

IF Proc.（ 6 chs）

THz Digit LO （ Band1 &

2）

Backend SpectralProc.

Control & DAC

DATE5 System Diagram

DATE5 Specs

Optics Symmetric Cassegrain

Main Reflector 5m paraboloid

Surface Accuracy 10m (rms)

Pointing 2“ (rms)

FoV 10′×10′ (350m), 5′×5′ （ 200m）Receiver Superconducting Mixer ， Nb/NbN SIS&HEB

Wavelength 350m×6, 200m×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

1980s1980s13.7m-100GHz, Delignha POST 30cm-492GHz

1995- 1995- 2000-20052000-2005

SMA Collaboration（ 0.2-0.9THz， Mauna Kea/Hawaii）

ALMADome A THz Dome A THz DevelopmentDevelopment

2005-2009

2006-

The Superconducting Spectroscopic Array (SSAR):A mm-wave multi-beam receiver recently finished for

Delingha 14m Telescope

Sideband Separation SIS3x3 beams, 18 IFsAll digital System

DATE5: Conceptual Studies onAnt & 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(14) & Band2(12) 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

1.3THz NbN SIS mixer chip & measured I-V curve

Original design initiated from 790-850GHz band

design during ALMA R&D collaborations

Band2 HEB mixer prototype chip & measured FTS Response

Bandwidth ： 2GHz

Freq Resolution ：61kHz

Dynamic Range ：≥ 30dB

Stability ：≥ 1000s

Bandwidth ： 2GHz

Freq Resolution ：61kHz

Dynamic Range ：≥ 30dB

Stability ：≥ 1000s

Prototype 2GHz Digital FFT Spectrometer based on FPGA(Yang, J. et al., 2011, under development)

Function diagram for 2GHz real-time digital FFT spectrometer, as a prototype back-end signal processing solution to the Dome A THz telescope

real-time pipeline FFT algorithm based on FPGA, 32k points

Requirement for THz Focal Plane Imaging DetectorsCall for International Collaboration

• 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

Herschel Blue Array 2048 pixels

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

Function ： To supply power, communica-tion, 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.

2007-2009 AUS 、 CHN 、 US 、 UKJoint PLATO

2010 PMO-SEU Joint ASP