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\begin{document}

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\Large 
\centerline {Final Report for the design study of \HEAT:}
\large
\centerline {A High Elevation Antarctic (Terahertz) Telescope}
\centerline {ANT-0538665}
\normalsize


\vspace{0.25cm}

\section{Executive Summary}

\subsection{Instrument Description}

The High Elevation Antarctic Telescope (\HEAT) is an automated, 0.5-meter Terahertz (THz) 
observatory proposed for remote operation at the summit of Dome~A, the
highest point on the Antarctic plateau.    The unparalleled stability, exceptional dryness, low wind
and extreme cold make Dome~A a ground-based site without equal for
astronomy at infrared and submillimeter wavelengths. 
Optimized for operation at Dome~A, 
\HEAT\ will forge entirely new capabilities for ground based infrared and submillimeter
astronomy.  Indeed, Dome~A 
is likely the only site on Earth where the crucial 1.9~THz window
becomes accessible for any length of time.  
\HEAT\ will routinely access one of the least explored
regions of the electromagnetic spectrum and provide new, fundamental
knowledge about the distribution and state of matter in the
Galaxy.  Through large-scale Galactic surveys, 
the measurement and impact of the Galactic
environment on the life cycles of interstellar clouds and their
relation to star formation will finally be realized. 

\HEAT\ and its accompanying Australian Plateau Observatory (PLATO) 
represent a new generation of polar instrumentation which permits the excellent 
conditions available from remote sites like Dome~A to be harnessed without the costs 
and hazards associated with manned operations.  The receiver system itself serves as a flexible 
testbed for heterodyne Terahertz components.  Future upgrades of 
mixer, local oscillator, low-noise amplifier, cryogenic, and digital 
signal processing technologies are planned and will play essential roles in
future Terahertz observatories.  This pioneering mission will pave the
way for future astronomical investigations from Dome~A. 

\HEAT\ is an IPY Joint Committee approved,
multi-national project, with contributions from the University of New
South Wales (UNSW), the Space Research Organization of the Netherlands
(SRON), the University of Cologne, as well as NASA and several US
universities.  

\subsection{Scope and Summary of Design Study}

To succeed, \HEAT\ must
be robust and capable of remote, low-power operation for a year at a
time. In many ways \HEAT\ is more like a space-based observatory than a
ground-based one.  The principal goal of this one-year study
was to arrive at a detailed design, cost analysis, and working
logistical plan for the entire project.  Based on the results of
this design study, the revised \HEAT\ design has been proposed to
NSF-OPP in June 2007 (ANT-0739777) and is currently under consideration. 

\clearpage

\noindent The three major accomplishments of this design study are:

\begin{itemize}
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\item {\bf Achieved a dramatic reduction in risk and cost:}  At the outset of the
  study, the proposed design included a 2-axis (tracking) motorized
  telescope with a state-of-the-art 4K cryocooler and arrays of Hot
  Electron Bolometer (HEB) mixers.   The high level of risk,
  particularly for a newly-developed site with no human presence or 
  infrastructure, led
  us to evaluate new approaches.  The new baseline design features a
  non-tracking one-axis telescope, a low-power ``off-the-shelf'' 70K cryocooler
  that does not compromise the mission should it fail, and robust
  Schottky mixers that can operate satisfactorily at ambient
  temperature.   These, among other alterations, improve the
  likelihood of success
  and reduce the mission costs from \$4.8M to \$2.2M!  A full cost
  breakdown is provided in our June 2007 HEAT OPP proposal. 

\item {\bf Defined a working Logistical Plan:}  A 3-year Memorandum of
  Understanding has been signed between the University of New South
  Wales (UNSW) and the Polar Research Institute of China (PRIC)
  regarding the Australian PLATO site-testing observatory and its
  attendant instruments, including \HEAT.   At the time of writing a
  direct MoU is being drafted between PRIC and the University of
  Arizona.   These negotiations have led to the Chinese
  program agreeing to deliver a UNSW PLATO module to Dome~A in
  Austral summer 2007-8. With the
  heavy lifting to be performed this year by PRIC under the IPY PANDA program, 
  only personnel transport via Twin Otter air support will be
  requested from USAP.  With extensive operation in
  the East Antarctic plateau starting in 2008 for AGAP and other
  endeavors, our air support requests are comparatively modest.
  A full development plan will 
  be undertaken once \HEAT\ is a fully funded NSF project. 

\item {\bf Defined, proposed and are delivering a prototype mission:}
  With an Australian PLATO observatory to be delivered to Dome~A in
  Austral Summer 2007-8, the opportunity arose to develop a
  submillimeter instrument for it.  
  Named \preheat, this 20~cm telescope will soon measure
  the quality of the 450~\micron\ submillimeter sky above Dome~A in advance of
  HEAT, and will also perform its very own Galactic Plane survey in the
  J=6-5 line of \tco\ at 0.66~THz.  This submillimeter survey is the first
  of its kind and foreshadows the Terahertz surveys that \HEAT\ will
  perform.  Furthermore, every part of \preheat\ is a prototype
  for the full \HEAT\ mission.   

\end{itemize}

\section{Description of Major Study Issues}

\subsection{The Dome A Environment}


\begin{figure}[!hbt]
\centering
\begin{minipage}{6.5in}
{\parbox{4in}{\includegraphics[scale=0.5,angle=0]{./figures/domeA-bigplot.eps}}}
{\parbox{2.3in}{
\caption{\label{wx} {\small The joint Australian/Chinese
    deployment of an AWS to Dome~A in 2005 demonstrates that Dome~A is uniquely
    colder, drier, with lower atmospheric pressure, and calmer than
    any other known site on the Antarctic Plateau.  These measurements
allow estimates of the precipitable water vapor (bottom plot), and hence
submillimeter sky opacity, to be made.  From these estimates, it is
clear that Dome~A is the preeminent site on the planet for
ground-based Terahertz-wave astronomy; by comparison, the ALMA site in
Chile has a best quartile PWV of 0.4mm! }} }}
\end{minipage}
\end{figure}

With operation of an Australian Automated Weather Station (AWS) at
Dome~A, it is now possible to estimate the submillimeter sky opacity
based upon the ground-level temperature, dew point, and atmospheric
pressure.    A plot of the weather at Dome~A is shown in
Figure~\ref{wx} and is restricted to the first half of 2005 for
readability.    These data demonstrate conclusively the following
important points for implementing a submillimeter telescope at
Dome~A:

\begin{enumerate}
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\item Dome A is colder than other continental sites like Dome~C and
  the South Pole.   Monthly temperatures in 2005 were consistently
  5-7$^o$C colder than at South Pole, falling to -100$^o$F in early
  April!  
\item Hygrometer measurements suggest that the airmass is unsaturated,
  with a winter RH of 40\%, lower than Dome~C and South Pole.  This
  lends credence to the suggestion that the 
  virgin ``stratospheric'' airmass extends essentially all the way to the ground.
\item Although the physical altitude of Dome~A is comparable to Mauna
  Kea in Hawaii (4.1 km), the thinner atmosphere over the Poles
  reduces the atmospheric pressure significantly.   A typical winter
  reading of 560 mbar is comparable to a pressure altitude of 15,600
  ft, or 4.8 km, comparable to the Chilean sites in the high Atacama
  desert, but much colder.  
\item The winds are very low.  Although mechanical operation of the
  AWS anemometer is not reliable below -60$^o$C, the measured
  winds at Dome~A average about 2 m/s; much lower
  than South Pole (6 m/s) and incrementally lower than Dome~C (3 m/s). 
\item The resulting calculation of the precipitable water vapor,
  critical to estimating the submillimeter and Terahertz sky opacity,
  indicates that periods where the PWV drops below 0.1~mm are
  commonplace in winter.   This makes Dome~A the driest, calmest site for
  Terahertz astronomy on the planet. 
\end{enumerate}


\begin{figure}[!hbt]
\centering
\begin{minipage}{6.5in}
{\parbox{3.9in}{\includegraphics[scale=0.39,angle=-90]{../figures/transplot.eps}}}
{\parbox{2.4in}{
\caption{\label{atmo} { \small Terahertz atmospheric transmission for good 
    ($\sim$25th percentile)
    winter conditions for South Pole (bottom) and Dome~A (top),
    derived from precipitable water vapor (PWV) measurements at Pole 
and actual Automatic Weather Station (AWS) data
      collected during 2005 from Dome~A by our Chinese and Australian colleagues.
    Arrows indicate the
    wavelengths of the [N~II], [C~II], and CO/[C~I] lines.}}}}
\end{minipage}
\end{figure}


\subsection{Instrument Concept}

HEAT will be a fully automated, state-of-the-art THz observatory
designed to operate autonomously from Dome A in Antarctica. The
combination of high altitude (4,100~m), low precipitation, and extreme
cold make the far-IR atmospheric transmission exceptionally good
from this site. In Figure~\ref{atmo} we present a plot of the
expected atmospheric transmission above Dome A as a function of
wavelength, indicating that winter weather at Dome~A
approaches (to order of magnitude) the quality of that achieved
by SOFIA.  The wavelengths of several important
astrophysical lines are indicated with arrows. HEAT is designed to
take advantage of these unique 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). 

\begin{figure}[!hbt]
\centering
\begin{minipage}{6.5in}
{\parbox{4.4in}{\includegraphics[scale=3.1,angle=0]{figures/concept.eps}}}
{\parbox{2in}{
\caption{\label{concept} {\small  HEAT concept: The telescope has an effective
collecting area of 0.5m. Elevation tracking is accomplished by
rotating the $45^\circ$ flat reflector. The entire telescope structure
is warmed by waste heat 
conducted from the PLATO instrument module below. The Schottky mixers used in
the instrument package are efficiently cooled to $\sim$70~K using
a reliable off-the-shelf closed-cycle cryocooler. }} }}
\end{minipage}
\end{figure}

\smallskip
A conceptual drawing of HEAT is shown in Figure~\ref{concept}. For
robustness and efficiency, the telescope and instrument are integrated
into a common optical support structure (OSS). 
HEAT will be mounted on top of a University of New South Wales Plateau
Observatory (PLATO), a successor to the AASTINO
(Automated Astrophysical Site-Testing InterNational Observatory)
deployed to Dome~C in 2003. PLATO provides power and communications for the HEAT telescope and
instrument. The total power budget for HEAT (including cryogenics, telescope 
drive system, and instrument control system is maximally 600~W, which is
readily provided by efficient, high reliability solar panels in the
summer and diesel generators in the winter.  Data
transfer and control of HEAT will be done via satellite and is
described in more detail in Section~\ref{control}. 
UNSW will provide a PLATO module for HEAT and participate in the design,
integration, deployment, and operation.

\subsection{Telescope}

The telescope is designed to have maximum efficiency and the minimum
number of optical components. Its design is similar to that of Kraus
(1966) and utilizes an off-axis, Gregorian configuration. Incoming
light is reflected horizontally off a 45$^\circ$, $0.5 
\times 0.7$~m flat reflector to an f/2.2 off-axis parabolic mirror. The
converging beam is intercepted by a hyperbolic tertiary mirror that
directs it to a flat quaternary and into the receiver. The tertiary 
mirror can chop the incoming beam between source and reference
positions ($\Delta {\rm az} \sim 10^\prime$) at a rate of 0 to 4~Hz. The
mirrors are fabricated from aluminum on a numerical milling
machine and have a surface roughness $\le 3\,\mu$m rms.  Elevation
axis motion is achieved by rotating the first flat reflector.   
Mapping will be typically performed in drift-scanning (``on-the-fly'')
mode while tracking only in elevation.
In fact, some of the Galactic Plane can be mapped purely with
zero-motion sidereal-rate scanning! 
The absolute pointing accuracy will be
15$^{\prime\prime}$, 1/5 of the smallest diffraction-limited beam. The
maximum slew speed will be 5$^\circ$/sec.  The University of Arizona has a
long history of building state-of-the-art telescopes and, with oversight from members 
of the Instrument Team, has the expertise required to optimize the telescope
for operation in a Polar environment. 

To prevent ice accumulation, the telescope is
enclosed and warmed to -20$^\circ$C by conduction through the
access port from the warmer PLATO module below. A small radome made of a low-loss
dielectric (e.g. Goretex or polyethylene) encircles the first flat
reflector. This optical configuration provides an unobstructed view of
the sky. A near-IR camera (provided by UNSW) is mounted just
outside the radome on an extension of the elevation axis. The camera will
provide pointing and site testing data. 

\subsection{Receiver}

\subsubsection{Design Approach}

Heterodyne receivers are needed to achieve the sensitive, high
spectral resolution ($R=\lambda/\Delta\lambda > 10^6$) observations of
[N~II], [C~II], and CO/[C~I]
required for the proposed Galactic plane survey. The key components of a
submillimeter-wave heterodyne receiver are the mixer and local
oscillator (LO).   There are 3 types of mixers in common
use; the Schottky diode mixer, the SIS mixer, and, more recently, the
Hot Electron Bolometer (HEB) mixer. The Schottky diode mixer is
somewhat less sensitive than either SIS or HEB mixers and requires more
LO power, but is exceptionally stable in operation and
{\bf can operate at ambient temperature}.  In contrast, SIS and HEB receivers require
cooling to LHe temperatures (4K).   HEAT's aggressive development
schedule combined with the critical need for robust technologies that
will work at low power and in a harsh environment leads us to select
Schottky mixer systems for the initial deployment of HEAT.   Virginia
Diodes, Inc. has a long history of delivering submm-wave Schottky
mixer systems and has demonstrated sub-harmonically pumped
Schottky mixers using lower frequency LO sources. 
Virginia Diodes will deliver one such mixer at 1.9~THz and another at
1.46~THz.   Two sub-harmonically pumped 810~GHz mixers (one for each
polarization) will be provided to increase sensitivity and
redundancy.  Though the system will function well at ambient
temperatures, we plan to improve HEAT's sensitivity to within a factor
of $\sim$3 of demonstrated THz HEB systems by cooling the 
mixer blocks to $\sim$70K using economical, low power, commercial Stirling-cycle
cryocoolers such as those sold by Qdrive and Sunpower, Inc. In this
manner we will achieve a solid blend of good sensitivity and 
experimental robustness.   A future 4K cryocooled SIS and HEB receiver system 
for HEAT is now in development at the Space Research Organization of the Netherlands
(SRON), with an initial 600K~Euros of institutional support. 

\subsubsection{Receiver Optics and Cryostat}

A close-up of the receiver optics is shown in Figure~\ref{optics}. The
incoming beam from the quartenary encounters two bandpass filters,
the first centered on the [N~II] (1.459~THz) line and the second on the
[C~II] (1.9~THz) line.  The three emerging beams are
collimated and directed into the instrument cryostat.    

Sub-harmonic LO pumping of the Schottky mixers eliminates the
quasi-optical injection of the LO signal and simplifies the optical
layout of the cryostat.    Wire grids direct the
horizontal and vertical polarization components of the incoming light
into the two 0.8~THz mixers.

\begin{figure}[!hbt]
\centering
\begin{minipage}{6.5in}
{\parbox{4in}{\includegraphics[scale=0.95, angle=0]{../figures/optics.eps}}}
{\parbox{2.3in}{
\caption{\label{optics} {\small  Optical subsystem for
 HEAT's Schottky mixers consists of bandpass filters and wire grids.
 Outside of their nominal passband, the filters are highly reflective.
 Therefore, when the incoming beam encounters the first filter, all
 but a narrow range of frequencies around the [C~II] line 
are reflected to the [N~II] filter. The light reflected off the [N~II]
filter contains the CO J=7$\rightarrow$6 and [C~I] lines.   }}}}
\end{minipage}
\end{figure}

The fabrication and integration of the vacuum vessel (10'' in diameter and 5'' tall) with the
cryocooler will be performed by Universal
Cryogenics of Tucson, Arizona, who has done similar work for the PI's
Supercam instrument, as well as for other Steward Observatory projects.  

\subsubsection{Mixer Performance}

Virginia Diodes will provide subharmonically-pumped, Schottky mixers 
with integrated, synthesizer-driven LO chains for HEAT. These mixers provide 
competitive receiver noise performance
even at ambient temperatures.   
With 5 watts of thermal load, the instrument cryocooler (either from Qdrive or Sunpower Inc.) 
will cool the mixers to ~70~K, sufficient to increase
their sensitivity by a factor of ~2.   We
anticipate delivered cooled DSB receiver noise temperatures in the vicinity
of 2000K at 0.8~THz, 4000K at 1.4~THz and 6000K at
1.9~THz. 

\subsubsection{IF Processors}

The entire IF processing and
spectrometer system will be leveraged from the successful design
being implemented in SuperCam (the PI's 64-pixel, 345~GHz array receiver).
Funds will only be needed to
fabricate additional amplifiers, IF processor modules, and
spectrometer boards for HEAT.    
The 5~GHz-centered IF output of the THz mixers is first amplified by a 
low-noise MMIC amplifier designed by Sander Weinreb's group at
Caltech for the Supercam project.    In order to
simultaneously detect the CO J=7$\rightarrow$6 and [C~I] lines in
separate sidebands, the 0.8~THz mixer will
have an IF center frequency of 1.5~GHz and then be upconverted to 5~GHz 
to match the other channels for subsequent IF processing. Low-noise, cryogenic,
1.5~GHz IF amplifiers are readily available.

The IF processor board provides each channel with an
initial 48 dB of gain, a variable digital attenuator, a 1~GHz bandpass
filter, a mixer conversion to baseband, a low pass filter, and 
50~dB of baseband gain.  An additional circuit provides total-power
measurements of the IF power for telescope pointing and continuum
measurements.  
 A picture of the 8-channel IF
processor module and a sample 512 MHz bandpass is shown in
Figure~\ref{IFproc}.   Only four of these channels will be utilized by
the \HEAT\ instrument.

\begin{figure}[!hbt]
\centering
\includegraphics[scale=0.75,angle=0]{../../../2004/MRI-SuperCam/supplement/figures/IFproc2.eps}
\includegraphics[scale=0.8,angle=0]{../../../2004/MRI-SuperCam/supplement/figures/IFproc1.eps}
\caption{\label{IFproc} {\small 8-channel IF processor module and
    sample bandpass}}
\end{figure}






\subsubsection{FFT-in-FPGA Spectrometer}

The HEAT Galactic Plane surveys require both fine kinematic resolution  (1~MHz) 
to disentangle cloud components and wide instantaneous bandwidth ($\ge$~1~GHz) to span the
velocity dispersion of the Galaxy.
Recent gains in high-speed ADCs and FPGAs have
made such a wide bandwidth, direct-digitization spectrometer economically feasible. 
The baseband output of the IF processors is fed into two direct
digitization spectrometer boards, each board with 2-IF inputs.
For each IF input the spectrometer board provides 1~GHz of instantaneous bandwidth at
1~MHz resolution.   The resulting velocity coverage (up to 
370~km/s at a resolution $\le 0.4$~km/s) enables all three
lines to be resolved and observed throughout the Milky Way.  
Omnisys Inc. has already
designed and delivered 8 of these boards for the PI's Supercam array project.
The delivered system is
depicted in Figure~\ref{FFTspec} and
performs admirably.  The measured Allan variance (stability) time is 650 seconds
when using a 5~GHz noise source that has been downconverted through the Caltech 
IF processor board (Figure~\ref{end2endresults}).  

\begin{figure}[!hbt]
\centering
\begin{minipage}{6.5in}
{\parbox{3.8in}{\includegraphics[scale=0.9,angle=0]{../figures/spectrometer.eps}}}
{\parbox{2.5in}{
\caption{\label{FFTspec} {\small  The assembled 8-board, 16~GHz FFT spectrometer from the
PI's Supercam project is no larger than a rack-mounted PC and requires
only 200 watts of input power!  One-fourth of this
spectrometer system will be purchased for HEAT. }}}} 
\end{minipage}
\end{figure}

\begin{figure}[!hbt]
\centering
\includegraphics[scale=0.85,angle=0]{../../../2004/MRI-SuperCam/supplement/figures/spec-line.eps}
\includegraphics[scale=0.7,angle=0]{../../../2004/MRI-SuperCam/supplement/figures/specperf2.eps}
\caption{\label{end2endresults} {\small Sample results from the end-to-end
   test of SuperCam components to be used for HEAT (August 2006):  (TOP) 
    First spectral light of an injected line at 346 GHz as detected by the
    Omnisys FFT spectrometer.  (BOTTOM) Allan-variance of the
    combined Caltech IF processor and Omnisys FFT spectrometer.  
    Classical spectroscopic Allan time is 650~seconds. }}
\end{figure}


\subsubsection{Calibration}

HEAT will be able to calibrate observations through several means. 1)
A vane with an ambient temperature absorbing load will be located at
the cryostat entrance window, allowing standard chopper wheel calibration
to be performed. 2) HEAT will routinely perform sky-dips to
compute the atmospheric optical depth in each of its three wavelength
bands. 3) HEAT will regularly observe a standard list of calibration
sources. 4) The PLATO will host {\tt Pre-HEAT}, a 450~$\mu$m tipper 
that will measure 
atmospheric transmission. Its measurements will be
coordinated with HEAT spectral line observations to provide cross
calibration. 

\subsubsection{Control System and Communication}
\label{control}

The HEAT control system consists of several subsystems; 
the telescope drive system, receiver frontend
({\it e.g.} mixers, LOs, and cryostat) computer, and backend
(spectrometer) computer.  The subsystems communicate via Ethernet.  
The subsystems are based on
Technologic Systems TS-ARM embedded computers that draw
less than 2 watts of power, run Linux or NetBSD, and have been
field-tested to survive the cold.   These systems
provide digital I/O, analog-to-digital conversion, serial I/O, and CAN, SPI and I2C bus interfaces for
control of the various electronic subsystems in HEAT.  These
single-board computers are slave to a UNSW-designed ``supervisor'' power control
board in PLATO that contains a watchdog circuit that will reset the system in
case of a software or hardware malfunction and cycle tasks to the next
available embedded computer.   HEAT will be designed to work 
autonomously for up to a week at a time, performing pre-programmed
observational programs and storing astronomical and housekeeping data
on non-volatile memory.  Preprocessed sample data will be uploaded to
control centers at the Universities of Arizona and New South Wales
via dedicated Iridium satellite channels located on each
``supervisor'' board.  Raw data will be recovered from HEAT each year
during maintenance and processed into the released data products.  We
aim to also integrate a portable field antenna for NASA's TDRSS-1 satellite for
routine downlink of raw data well in advance of annual maintenance. 


\begin{figure}[!hbt]
\centering
\includegraphics[scale=0.87,angle=0]{figures/powercontrol.eps}
\caption{\label{power} {\small  A sample power and control
    distribution diagram showing schematically the integration of the
    HEAT subsystems into a single observatory.}}
\end{figure}


\begin{figure}[!hbt]
\centering
\includegraphics[scale=1,angle=0]{figures/IFlevels.eps}
\caption{\label{IFdist} {\small  An RF integration diagram showing the
    (inter)relation of all
    receiver-level IF components. }}
\end{figure}

\subsection{Integration and Testing}

The use of developed or commercial subsystems in HEAT
allows system integration and testing to be performed in a timely
manner.   Sample system-wide diagrams of power and IF distribution in
HEAT are shown in Figures~\ref{power}-\ref{IFdist}.

\vspace{-0.2cm}
\begin{enumerate}
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\item {\bf Cold component testing} will be used to determine limiting
temperatures for reliable operation of constituent components in each
subsystem.  These component tests will define a process by which the
telescope can be nominally operated in a range of highest reliability, or
safely resurrected from an idle state in which all components have been
cold-soaked.  

\item  {\bf Subsystem testing} will demonstrate
the proper functionality of large components of the HEAT system, such
as the assembled telescope drive system or the Schottky instrument
package and control electronics, or the spectrometer and data system.

\item {\bf Integrated system testing} involves the interplay of subsystems in the
actual collection of data, such as performing on-the-fly mapping
observations with active receivers, spectrometers, data system, while
monitored over a Iridium satellite connection; i.e. normal
astronomical operation
at Dome~A. 

\item   {\bf Failure Mode testing} involves the intentional
disabling of a component to observe the fault handling and
interplay of the hardware and software systems.   A Failure Mode Effects Criticality
Analysis (FMECA) will be generated to determine system robustness to
component failure.  System reliability will then be
enhanced through application of redundancy, increased reliability rated
components, and improved operational design where indicated.

\end{enumerate}

The combination of Schottky diode receivers, 
interchangable (and in some cases, 
dual string) computer control subsystems, Iridium communication links on robust watchdog circuits, 
diesel power generation with solar
panel backup, and adopting a largely fixed, stable, simple optical system, 
all contribute to a highly {\bf reliable and robust system}.

\subsection{Logistics: Deployment to Dome A}
 
Antarctic science has reached a level of maturity where several options exist
for fielding instruments on remote sites. For Dome~A, these include:

\begin{enumerate}
\setlength{\topsep}{-1ex}
\setlength{\partopsep}{-1ex}
\setlength{\itemsep}{-0.4ex}
\setlength{\parsep}{-0.4ex}

\item {\bf (Chinese) Traverse from Zhongshan to Dome~A}:  UNSW has
  recently signed a Memorandum of Understanding (provided in the
  Supplementary Documentation) with the Polar
  Research Institute of China and the National Astronomical
  Observatories of China for Chinese deployment of a UNSW PLATO to
  Dome~A in 2007-8.   Our baseline plan is to simply
  install HEAT atop this PLATO module over two of the remaining spare
  ``roof'' ports.   It could be installed
  as part of a 2009 Chinese traverse,  combined with supplemental transport
  options described below.  

\item {\bf Twin Otter Air Support}:  If a
  Chinese traverse brings PLATO (in 2007) and HEAT to Dome~A (in 2009),
  USAP Twin Otter air support would allow personnel to be flown in from South
  Pole or the forthcoming AGAP field camps (such as AGO3) to facilitate the HEAT
  installation. 

\item {\bf CASA 212} (Australian Antarctic Division): J. Storey of
  UNSW will be requesting one CASA 212 cargo flight directly from
   e.g. South Pole to Dome~A for transport of the HEAT experiment,
   with subsequent flights to support fuel and/or personnel for the
   HEAT installation. 

\end{enumerate}

The HEAT team will continue to work closely with the NSF, USAP, Raytheon
Polar Services, and the International Community to implement an optimal plan
for deployment to Dome~A.  

\subsection{Pre-HEAT: A Forerunner to HEAT}

An exciting and timely opportunity has arisen that allows us to 
perform pioneering research {\it immediately} at Dome~A.
Our Chinese and Australian partners will be installing the first base Plateau
Observatory (PLATO) on Dome~A this coming Austral summer (2007-8) and have given us
the opportunity to field a submillimeter radiometer as part of this expedition.
This instrument, \preheat, is a 450~\micron\ (660~GHz)
tipping radiometer coupled with a digital FFT spectrometer.  
The goals of \preheat\ are to (1) Measure the
submillimeter sky opacity as a quantitative demonstration of the
exceptional conditions of Dome~A, (2) Perform strip maps of the
Galactic Plane in the $^{13}$CO J=6-5 line at 661~GHz, constituting the first
astrophysical measurements from Dome~A, and (3) Field-test many of the
key technologies for \HEAT\ as possible.   \preheat\ will pioneer new capabilities for ground-based
astronomy and is an opportunity for the US to play a major role in a 
landmark International Polar Year (IPY) project.  

Pre-HEAT is being funded by NSF under the auspices of the Small Grants
for Exploratory Research (SGER) program (ANT-0735854).
Generous contributions from our domestic and international partners
have made this instrument feasible with minimal financial outlay.
Pre-HEAT is currently being constructed and will be shipped to UNSW
for integration with PLATO in late September 2007!   An assembly cutaway of the
Pre-HEAT tipper telescope is shown in Figure~\ref{preheat}. 

\begin{figure}[!hbt]
\centering
\includegraphics[scale=1,angle=0]{figures/preheat.eps}
\caption{\label{preheat} {\small  An exploded view of the Pre-HEAT
    telescope and its installation onto the UNSW PLATO module.
    Pre-HEAT will test all key technologies for HEAT and conduct its
    own submillimeter Galactic Plane survey from Dome~A in 2008! }}
\end{figure}


\end{document}
