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\begin{document}

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\twocolumn[

\Large 
\centerline {The High Elevation Antarctic Telescope (HEAT):}
\large
\centerline {Opening New Windows to Ground-Based Astronomy}
\normalsize

\bigskip

We propose to develop an automated, 0.5-meter Terahertz (far-infrared)
observatory for remote operation at the summit of ``Dome~A'', the coldest, highest, and
driest point on the central Antarctic plateau.  From this extraordinary site, 
the High Elevation Antarctic Terahertz Telescope (HEAT) will operate in the 
atmospheric windows between 150 and 400~$\mu$m, in which the most crucial
astrophysical spectral diagnostics of the formation of galaxies,
stars, planets, and life are found.  HEAT will answer timely and 
fundamental questions about the evolution
of the interstellar medium and star formation:  through large-scale
Galactic surveys the {\bf impact of the Galactic
environment} on the {\bf life cycles of interstellar clouds} and their
{\bf relation to star formation} will finally be realized. 
HEAT will pioneer new capabilities for ground-based
astronomy, Terahertz instrumentation technologies, 
and will deploy during the landmark International Polar Year (IPY).  
The HEAT project is driven by the University of Arizona but also brings with
it a rich and diverse worldwide collaboration with unique
opportunities for future development of ground, sub-orbital, and
space-based missions and technologies.

The HEAT project (through the AstroPoles program, M. Burton-PI, UNSW) 
has been endorsed by the IPY Joint Committee (see attached letter) and received 
funds from the NSF Office of Polar Programs (NSF-OPP) to conduct a detailed design study. 
The NSF-OPP recognizes the importance and pioneering spirit of HEAT and it is with their 
encouragement that we submit this proposal. 

\bigskip
\hline
\bigskip
]


\section*{Scientific Justification}

The far-infrared (Terahertz) portion of the electromagnetic
spectrum contains answers to fundamental questions 
concerning the origin and evolution of the Universe, 
galaxies, stars, and planets.   For example, far-infrared spectroscopy will fill glaring
gaps in our understanding of the life cycle of interstellar clouds (Figure~\ref{lifecycles}),
the ``nurseries'' from which all stars and planets (and life?) are
born.  {\it  It is astonishing that the formation and destruction of these
clouds remains unobserved given their importance to our
own cosmic origins!}   However, all far-infrared spectroscopy has come
from limited operation of airborne and space observatories.    
Less than 0.01\% of the Galaxy has been
surveyed with high spectral resolution in the pivotal 158~\micron\ line of ionized carbon, the
brightest spectral line in the Galaxy!  Yet no present or planned
observatory will significantly increase that figure despite
improvements in detector sensitivity.  

\begin{figure}[!hbt]
%\vspace{-0.3cm}
\centering
\includegraphics[scale=0.35,angle=0]{../figures/LifeCycle-ISM.eps}
\caption{\label{lifecycles} {\small 
HEAT will be the first dedicated instrument to study the entire life cycle of interstellar clouds from which stars and planets are formed. }}
\vspace{-0.4cm}
\end{figure}

Exciting new developments offer promise that such observations can
be performed from the ground!  
A 2005 Chinese expedition to ``Dome~A'', the summit of the Antarctic
ice plateau, installed an Australian Automated Weather Station (AWS)
that still operates today.  A plot of the atmospheric
transmission based on this data shows that entirely new windows onto
the Universe are opened in the skies above Dome~A versus
established submillimeter sites such as Mt. Graham and 
the high Atacama desert in northern Chile
(Figure~\ref{atmo}).    These data confirm
that Dome~A is the preeminent site on the planet for submillimeter and
far-infrared (THz) astronomy owing to its extreme cold (-100F), high elevation
(14,000 ft), dryness, and near-absence of weather or wind.   

\begin{figure}[!hbt]
\vspace{-0.4cm}
\centering
\includegraphics[scale=0.8,angle=0]{../figures/transplot-mtgraham.eps}
\vspace{-0.2cm}
\caption{\label{atmo} {\small The atmospheric transmission from
    Mt. Graham allows efficient operation at frequencies below 1~THz,
    but the extraordinary conditions at Dome~A open up entirely new atmospheric
    windows of crucial importance. }}
\vspace{-0.4cm}
\end{figure}

A small, dedicated survey telescope at Dome~A would benefit astronomy
enormously;  its large-scale coverage of the Galaxy 
would provide a timely study of the ecology of the
Milky Way and how the evolution of interstellar gas relates to
the evolution of stars.  It could witness for the first time the formation of
interstellar clouds from which all stars and planets are
created.  By revealing the full life cycle of interstellar clouds, a
meaningful template of the Milky Way can be constructed -- a ``Rosetta
Stone'' which can be used to translate future observations of distant
galaxies into reliable indicators of their respective histories
(Figure~\ref{lifecycles}).   These surveys would be ``finder charts''
that would enable productive focused studies with future submillimeter
and Terahertz observatories like ALMA, Herschel, and SOFIA. 

The decade-long experience of the PI's team in building submillimeter
instruments for the AST/RO telescope at the South Pole
puts the UofA in a unique position to carry Terahertz
instrumentation and astronomy to the next stage of evolution.   The culmination of
this collaborative expertise will be brought to bear on {\tt HEAT}: the High
Elevation Antarctic Terahertz Telescope, an automated 0.5-meter
telescope for Dome~A, Antarctica. 



\section*{Instrument Description}

HEAT will be a fully automated, state-of-the-art THz observatory
designed to operate autonomously from Dome~A in Antarctica.  HEAT is designed to
take advantage of Dome~A's unparalleled atmospheric conditions and observe
simultaneously in [C~II](158 $\mu$m), [N~II](205 $\mu$m), and CO 
J=7$\rightarrow$6/[C~I] (370 $\mu$m) -- a combination that probes
every stage of a cloud's life cycle!


\begin{figure}[!hbt]
\vspace{-0.3cm}
\centering
\includegraphics[scale=0.75,angle=0]{../figures/concept.eps}
\caption{\label{concept} {\small Concept drawing of the HEAT telescope}}
\vspace{-0.3cm}
\end{figure}

For robustness and efficiency, the telescope and instrument are integrated
into a common optical support structure (Figure~\ref{concept}). 
HEAT will be mounted on top of a University of New South Wales AASTINO
(Automated Astrophysical Site-Testing InterNational Observatory, Figure~\ref{AASTINOHEAT}). 
The AASTINO provides power and communications for the HEAT telescope and
instrument. The total power budget for HEAT is 600W, 
readily provided by solar cells and/or generators within the AASTINO.   Data
transfer and command and control of HEAT will be done via Iridium
and TDRSS-1 satellites.
The University of New South Wales will participate in all aspects of design,
integration, deployment, and operation (see Support Letter from J. Storey).

\begin{figure}[!hbt]
\vspace{-0.3cm}
\centering
\includegraphics[scale=0.43,angle=0]{../figures/AASTINO.eps}
\caption{\label{AASTINOHEAT} {\small 3D rendering of HEAT mounted on its AASTINO }}
\vspace{-0.3cm}
\end{figure}

The telescope will be built at the College of Optical Sciences.  Its off-axis, Gregorian configuration
is designed to have maximum efficiency and the minimum
number of optical components.  Incoming
light is reflected horizontally off a 45$^\circ$, 0.5$\times$0.7m flat
reflector to an f/2.2 off-axis parabolic mirror. The
converging beam is intercepted by a hyperbolic tertiary mirror, to a
flat quaternary and into the receiver.   The detector system
will employ Schottky diode mixers with subharmonically-pumped Local
Oscillators that can operate effectively at ambient temperature.  The
mixers and amplifiers will be housed in a closed-cycle cryostat with a
200~watt free-piston Stirling engine cryocooler that can reduce the operating
temperature to 60K, improving sensitivity by a factor of 2-3.   Other
components, such as the IF amplifiers and processors, digital FFT
spectrometer, and bias electronics, will be identical to that
developed for SuperCam, a 64-beam imaging spectrometer for the
HHT on Mt. Graham. The receiver system will be constructed by the PI and his 
UofA team who have extensive experience designing, building, 
deploying, and using state-of-the-art submillimeter-wave/THz receiver systems. 

The 3-year budget for the HEAT project (including telescope,
instrument and personnel) is \$1,875,000, well within the cost cap of the MRI program.  

With the implementation of HEAT, the UofA will have a unique
capability for exploring the origins and ecology of galaxies, stars
and planetary systems like our own. It will play a visible role in
the landmark International Polar Year with a telescope that is a
pioneer in absolutely every regard!  During the last IPY in 1957, the U.S.
established a science station at the geographic South Pole -- this
time, the UofA could pioneer an observatory at Dome~A!  HEAT (with its accompanying 
AASTINO module) is tentatively scheduled to be taken to Dome A by a joint
Chinese/Australian/US expedition during the 2008-2009 austral summer. 
We look forward both to the exciting science that HEAT will perform and to the 
unique challenges of making it a reality. 

\end{document}
