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\begin{document}

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\Large \centerline {\bf Project Description} \normalsize

\section{Results from Prior NSF Support}
\subsection{High Elevation Antarctic Terahertz (HEAT) telescopes for Ridge A}
In 2010, the PI initiated an NSF-funded (ANT-0944335, 10/2010-9/2014) program to build two 60 cm terahertz telescopes for robotic operation
at the summit of the Antarctic high plateau with the dual purpose of
site testing and performing leading edge terahertz astronomy.  These
High Elevation Antarctic Terahertz (HEAT) telescopes operate from 150
to 600 microns wavelength and observe the brightest and most
diagnostic far-infrared lines in the Galaxy. An international
collaboration with Australia's University of New South Wales provided
the PLATeau Observatory for Ridge A (PLATO-R), a platform for power
and satellite communication.  In January 2012, PLATO-R and the first
HEAT prototype were successfully deployed to Ridge A and have
performed admirably.  HEAT is the world's first robotic THz telescope.  It
has the first cryogenic receiver system in the deep field that
operates for a full year between servicing missions.  HEAT is showing that
the Ridge~A site is the best site on the planet from which to perform terahertz
observations, with 10$\times$ more observing days suitable for
200~$\mu$m observations than Chajnantor (e.g. ALMA).  Already,
a public data release of 809~GHz (370~$\mu$m) data of
atomic carbon J=2-1 line emission has been made available at {\small \tt
http://soral.as.arizona.edu/heat/}.  Incremental followup data
releases are expected 1-2 times per year for the duration of the
program.  

\begin{figure}[!hbt]
\centering
\begin{minipage}{6.5in}
{\parbox{4.2in}{\includegraphics[scale=0.7,angle=0]{figures/RidgeA.eps}
\includegraphics[scale=0.42,angle=0]{figures/HEATimg.eps}}}
{\parbox{2.3in}{\caption{\label{heat} {\small (left) The PLATeau Observatory
    and 60~cm HEAT
    telescope at Ridge~A, Antarctica installed in January
    2012. (right) The first 0.6 sq.deg. 
integrated intensity map in 370 $\mu$m [CI] emission
returned by HEAT via onboard data processing and Iridium satellite
downlink. The highly extended emission observed directly probes
the {\it dark molecular gas}, i.e. H$_2$ clouds with little CO emission.}}}}
\end{minipage}
\end{figure}


\subsection{Supercam: A 64-beam Heterodyne Array Receiver at 850~$\mu$m}

In 2005, this team initiated an NSF-funded (AST-0421499,
1/2005-12/2009, PI: C. Walker) program to design and construct the
first integrated heterodyne focal plane array at submillimeter
wavelengths: 64 beams in the astrophysically important 850~$\mu$m
atmospheric window.  
Each component of Supercam has been modularized in units of 
1$\times$8 rows of the full heterodyne array
(Figure~\ref{prototype}).  Thus, the mixer blocks, bias 
electronics, IF processors, and digital FFT spectrometers are
quantized into modules that
provide 8 detector ``pixels''  each.  This one-dimensional integration is
crucial to the realization of large format heterodyne arrays and has been
successfully completed by the Supercam team (Figure~\ref{prototype}). 

\begin{figure}[!hbt]
\centering
\includegraphics[scale=0.37,angle=0]{figures/1x8_prototype_sm.eps}
\hfill
\includegraphics[scale=0.65,angle=0]{figures/supercam-focalplane.eps}
\caption{\label{prototype} {\small Left: The centerpiece of the
        Supercam heterodyne array is the integrated mixer
        block; comprised of 8 feedhorns, SIS mixers, MMIC low noise
        amplifiers, and nano IF \& DC connectors. The final 64-beam focal
        plane consists of 8 such mixer modules. Right: Zoom-in on the opened
        Supercam cryostat, showing the fully populated 64-beam focal
        plane.}}
\end{figure}


\begin{figure}[!hbt]
\centering
\includegraphics[scale=0.92,angle=0]{figures/map1.eps}
\hfill
\includegraphics[scale=1,angle=0]{figures/map2.eps}
\caption{\label{maps} {\small A sample of first light maps at 345~GHz made with
    Supercam at the HHT in late May 2012.  Left:  Integrated intensity map
    of CO J=3-2 line emission over 40'x40' of the W3 molecular
    cloud. Right: 
    Channel maps spanning 24'x30' of the Cepheus~A molecular cloud show
    complex kinematics.  Each image represents the emission in 1~km/s bins from V$_{LSR}$ = -18 to -6 km/s.  Despite the poor
    early-summer weather and a reduced pixel count, these large-scale maps were
    made in a few hours each. }} 
\end{figure}

The full Supercam instrument was successfully installed on the HHT in
May 2012.  Despite the comparatively poor
weather near the end of the observing season, Supercam achieved first
light and delivered more than 1 million spectra per day.  Supercam's
relay optics delivered a 23'' diffraction-limited beam and 60\% beam
efficiency in nearly every pixel.  Two sample maps from that
engineering run are shown in Figure~\ref{maps}.  The yield of
pixels with good sensitivity (T$_{rec}<100$K DSB) during the
engineering run was approximately 55\%. Optimization of devices in the
focal plane took place in Fall 2012 and Spring 2013, and the focal
plane now achieves the desired uniformity and sensitivity.  Only the
few (8) remaining bad 'pixels' will be replaced before the
proposed work effort begins.  The current instrument performance is shown in 
Figure~\ref{perf}(left) and the corresponding mapping speed is shown
as a function of frequency in Figure~\ref{perf}(right), 
dominated by the atmospheric transmission in the 350~GHz band.  At the
frequencies of interest, near CO J=3-2 and HCO$^+$ J=4-3, the mapping
rate is approximately 4-5 hours per square degree, or {\bf 5-6 square
degrees per day}.  This sharply contrasts to the 4-5 days per square degree
that is typically expended at (easier) mm wavelengths.  
{\it Rapid, high fidelity spectroscopic 
mapping at submm wavelengths is the specific enabling
result which motivates the Galactic Plane pilot survey proposed here. }

\begin{figure}[!hbt]
\centering
\includegraphics[scale=1.05,angle=0]{figures/perf1.eps}
\hfill \includegraphics[scale=1.05,angle=0]{figures/perf2.eps}
\caption{\label{perf} {\small (left) Expected
        performance of Supercam based on laboratory receiver testing.
        The mean noise temperature of working devices is 90K DSB and
        the focal plane yield of good devices is 75\%.  (right)
        Corresponding mapping speeds at APEX, assuming an
        rms noise level of 0.2~K~km/s in median summer weather at a
        zenith angle of 30$^o$.  Near the spectral lines of interest,
        the mapping speed will be approximately 5 square degrees per
        day. }}
\end{figure}

\section{Research Activities}

Supercam will enable
pivotal astronomical research opportunities as an available PI
instrument at APEX.  For the November 2014 run, use of Supercam was
opened to all users and observing time was oversubscribed by a factor
of over 4:1 for ESO time.  Its high angular and spectral resolution,
coupled with an exceptional field of view makes it {\it a truly exceptional
Galactic Survey instrument}, which provided the primary motivation for
its construction.  Here, we outline a first
Supercam pilot study, a submillimeter CO survey of a
crucial portion of the Galactic Plane ideally observed from Chile.
The benefits to US Astronomy are substantial:

\begin{enumerate}
\item 20 square degrees of the Galactic Plane will be mapped by our
  observing proposal in 2014, with another 10-20 square degrees
  possible if an April 2015 run is granted.
\item Provides the ultimate wide-field spectroscopic survey for detailed followup with ALMA.
Data to be made available immediately with no proprietary period. 
\item Overlaps with surveys from High Elevation Antarctic Terahertz
  (HEAT) telescope (ANT- 0944335) supported by PLR and AST, and the
  Stratospheric Terahertz Observatory supported by PLR’s Long Duration
  Balloon facility at McMurdo Station (joint w/ NASA).
\item All other awarded Supercam/APEX programs have at least one US
  Co-Investigator.
\item 50\% of the awarded Supercam programs are lead by a US PI.
\item Over 320 hours of APEX time were awarded to Supercam in
  2014. April 2015 is pending. 
\end{enumerate}

\subsection{Justification for a RAPID response}

The installation of Supercam on the APEX telescope is a timely,
once-in-an-instrument's-lifetime event.  The November 2014 (and
potentially April 2015) observing windows for Chilean, ESO and Swedish
time are available for Supercam's use, and fully endorsed by the APEX
collaboration.  Proposals for Supercam time were publicly requested and
submitted in Spring 2014.  
The respective TACs responded favorably and have publicly 
committed essentially all of the
observing time in the Nov/Dec APEX run to Supercam.  
As the German partners in APEX
have their own multi-beam receiver in development, Supercam's
readiness creates a unique window of opportunity for 2014-15 
that is very unlikely
to repeat.  This time-critical access to a needed facility makes RAPID
the most appropriate avenue for support.  

Minimal RAPID funds from NSF are requested to take
Supercam instrument development ``the last mile'' to make this opportunity a reality. Investing
\$30k to deliver the scientific benefits behind NSF’s \$2.5M instrument
development effort is an exceptional return!  All of the facilities
available will be fully utilized to make this instrument development
and observing run a success. 

The established excellence of the APEX telescope and site, combined
with the readiness of the Supercam instrument creates a compelling and
unique opportunity to leverage NSF's major investment in the world's
first integrated submillimeter-wave imaging spectrometer. 

\subsection{Critical questions this pilot study will address}

The evolution of (the stellar population of) galaxies is
determined to a large extent by the life cycles of
interstellar clouds: their creation, star-forming properties, and
subsequent destruction by both natal and dying (massive) stars. 
The need to understand the evolution of interstellar clouds as they
directly 
relate to star formation and galaxy evolution has become acute.  The
most recent decadal 
survey, ``Astro2010: New Worlds, New Horizons'', specifically
identifies the questions ``{\it What controls the mass-energy-chemical
cycles within galaxies}'', ``{\it how do stars form}'', ``{\it what
  determines the 
star formation rates and efficiencies in molecular clouds}'', and
``{\it what determines the properties of pre-stellar cloud cores and what
is the origin of the stellar mass function}'' as among the key
questions for radio and (sub)millimeter facilities in this decade.
{\bf Further, the specific recommendation is made: ``A large-field
  mapper operating at 
millimeter and submillimeter wavelengths is required to pave the way
for follow-up observations with ALMA''.   Supercam is a
direct answer to this recommendation and is ready now}.


This project ultimately aims to increase our understanding of the
interactions between stars and the molecular clouds which form them.
Stars affect their environments through the direct input of kinetic
energy and by radiation which ionizes or heats adjacent molecular
gas.  This proposed survey will yield major new results targeted at
answering specific questions about molecular clouds, star formation,
and stellar feedback:

\smallskip
 {\bf(1)} How do molecular clouds form, evolve, and get disrupted?  How
  do typical atoms and grains cycle through the ISM; in particular,
  how do molecular clouds relate to the atomic hydrogen component of
  the ISM?  Is there statistical evidence that molecular clouds may be
  formed by colliding streams or filaments of HI as has been suggested in
  hydrodynamical models?

\smallskip
{\bf(2)} How and under what conditions do molecular clouds form stars?
  What role does the underlying physical structure of molecular clouds and
  their dense cores have on the mass function of stars that result?

\smallskip
{\bf (3)} What are the effects of HII regions on their associated
  molecular clouds? To what extent does cloud compression caused by
  expanding HII regions trigger the formation of dense cores and
  subsequent star formation?  To what extent do the dynamical, heating
  and ionization effects of OB stars and their HII regions destroy
  associated molecular clouds?  

\smallskip
{\bf(4)} What is the evolutionary and dynamical state of molecular cloud
  cores?  

\smallskip
{\bf(5)} How does the Galactic environment impact the formation of clouds
  and stars?   What are the specific roles of spiral arms, central
  bars, and infall and other influences from outside the Galaxy?  Can
  star formation in the Milky Way be synthesized into a ``template''
  to help interpret star formation in distant, unresolved galaxies?


We will use Supercam, the aforementioned state-of-the-art 64-beam
heterodyne array to map a pilot, 20+ square degree region of the
Galactic Plane (Galactic longitudes 310-330 degrees) in the J=3-2
transition of CO.  The proposed observations 
exploit the unique capabilities of Supercam, namely
efficient, rapid, high-fidelity spectral mapping over large angular
scales.  The survey angular resolution at APEX, 18'', will
yield maps superior in resolution and sensitivity to any other imaging
data yet presented over comparably large areas of sky.  
We will also employ other available data to form as
comprehensive a picture as possible of the ISM and the stellar content of
Galactic interstellar clouds.  With detailed kinematic analyses,
it will be possible to compare our data with predictions of numerical
hydrodynamical models of the ISM and thereby to constrain the physical
mechanisms resulting from stellar energy injection and the resulting
feedback which regulates the star formation process.  We emphasize
that these properties can only be determined from well-sampled
large-area maps that cover a wide range of spatial scales.  {\bf
  Single-dish telescopes are key to making 
high-fidelity images of the ISM with high spectral resolution and
spatial dynamic range}.  With the advent of ALMA, sensitive, high resolution
imaging of relatively small regions is now possible.  However,
large-scale imaging with ALMA is prohibitively time consuming; this is
a task most effectively performed by precision single-dish telescopes
outfitted with multi-beam receivers like Supercam.

\section{Project Impact}

\subsection{Educational Impact}

The training of students in the development and use of state-of-the-art
instrumentation  
is essential to the future of science. This is particularly true in
mm/submm astronomy where technological advances are occuring so rapidly.
Ironically, there are only a handful of laboratories in the world
where students 
gain hands-on experience in the design, fabrication, and fielding of
radio astronomy 
instrumentation. In the team's lab (SORAL: Steward Observatory Radio
Astronomy Laboratory), we have been fortunate to have had
a number of 
talented students pursue their research. Over the past 10 years the
lab has produced  
9 Ph.D.'s and numerous undergraduate senior projects.  The PI is in
fact a byproduct of this educational facility!  Most of the
Ph.D.'s are still 
pursuing astronomical research and a number of the undergraduates have
gone on to 
receive Ph.D's at other institutions. In recent years research in the
lab has drawn 
an increasing number of students from other departments, particularly
optical sciences and electrical engineering.  It is interest in
astronomy and the interdisciplinary nature of the research 
that attracts them to the SORAL lab.  In an effort to reach this
population of students, 
the Co-PI's and fellow faculty members in other departments are seeking to
establish an 
interdisciplinary program in astronomical instrumentation. Two of
Co-PI Walker's past
Ph.D. students have received majors and minors in different
departments.  Co-PI Walker currently 
has 4 graduate and 2 undergraduate students participating in
interdisciplinary studies. 


\subsection{Global Impact: Survey Synergies}
\label{synergies}

The proposed Galactic Plane survey with Supercam
will serve as the ultimate ``finding charts'' for future, focused surveys 
with ALMA and markedly enhance the value of numerous contemporary
surveys.  These data will be released openly to the astronomical
community, with no proprietary period.  The data management section
provides details of the Supercam data flow and archival plan.

\section {Project Management}
\label{management}

Transitioning Supercam from an instrument development to a scientific
workhorse is an exciting prospect that our team has been working
towards for years. Collectively the Supercam
team members represent many years of successful instrument development and
observing experience.  
The main components of the organization are the PI, who has overall 
responsibility for the project and coordinates the activities of the 
participants; Co-PI Walker who shares in these
responsibilities and lead the student advising efforts; and the
distributed members of the science team who act as an advisory council
to the PI and Co-PIs to ensure that the project stays on course. 
Routine communications between project participants is essential.
There will be monthly science team telecons
to monitor progress and provide insight into solutions to
emerging problems, and redefine priorities as needed. A Supercam wiki
at Arizona will provide a resource for team communications and
documentation.  

A {\bf first-draft Interface Control Document (ICD)} that outlines the
interfaces between Supercam and 
the APEX telescope is provided in Supplementary Documents.  Questions
that this document was designed to raise will be answered during an
on-site visit by the Supercam instrument team in late July 2014. 

\end{document}


