Dome A THz Astronomy Ji Yang Purple Mountain Observatory, 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 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 Precision Cosmology dominated by Dark Energy & Dark Matter Ecology in the Universe: ISM, Stars, Galaxies 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 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.

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 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 mm windows Dome A (4000m, -83C) Measurement（2007-2008, Pre-HEAT The best site ever knew New THz windows over 150-800 m

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.

Targeted Science Drivers 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.

2.5m Optical/NIR Telescope 5m THz Telescope Antarctic Support Platform 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

Dome A Observatory Development: A Roadmap 2006- 2008 Site Survey & Small Telescope +Site Testing & Middle-size Telescope 2009- 2011 5m THz DATE5 15m THz 2011- 2015 Dome A Observatory Phase I 2.5m Opt/NIR KDUST 2016- 2025 Dome A Observatory Phase II 6-8m Opt/NIR

Superconducting Mixer，Nb/NbN SIS&HEB Dome A THz Explorer（DATE5） Ant Relay Optics Ant Optics THz Receivers THz Mixers（Band1 &2） IF Proc. （6 chs） THz Digit LO（Band1 &2） Backend Spectral Proc. Control & DAC DATE5 System Diagram DATE5 Toy Model 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 DATE5 Specs

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 13.7m-100GHz, Delignha POST 30cm-492GHz 1995- 2000-2005 SMA Collaboration（0.2-0.9THz，Mauna Kea/Hawaii） ALMA 2005-2009 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 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

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 Freq Resolution：61kHz Dynamic Range：≥ 30dB Stability：≥ 1000s Function diagram for 2GHz real-time digital FFT spectrometer, as a prototype back-end signal processing solution to the Dome A THz telescope

Herschel Blue Array 2048 pixels Requirement for THz Focal Plane Imaging Detectors Call for International Collaboration Herschel Blue Array 2048 pixels 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, 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. 2010 PMO-SEU Joint ASP