We report on the performance of a high sensitivity 4.7 THz heterodyne receiver based on a NbN hot electron bolometer mixer and a quantum cascade laser (QCL) as local oscillator. The receiver is developed to observe the astronomically important neutral atomic oxygen [OI] line at 4.7448 THz on a balloon based telescope. The single-line frequency control and improved beam pattern of QCL have taken advantage of a third-order distributed feedback structure. We measured a double sideband receiver noise temperature (T<sub>rec(DSB)</sub>) of 815 K, which is ~ 7 times the quantum noise limit (hν/2kB). An Allan time of 15 s at an effective noise fluctuation bandwidth of 18 MHz is demonstrated. Heterodyne performance was further supported by a measured methanol line spectrum around 4.7 THz.
Supercam is a 345 GHz, 64-pixel heterodyne imaging array for the Heinrich Hertz Submillimeter Telescope
(HHSMT). By integrating SIS mixer devices with Low Noise Ampliers (LNAs) in 8 - 1x8 pixel modules, the
size needed for the cryostat and the complexity of internal wiring is signicantly reduced. All subsystems
including the optics, cryostat, bias system, IF boxes, and spectrometer have been integrated for all 64 pixels. In
the spring of 2012, SuperCam was installed on the HHSMT for an engineering run where it underwent system
level tests and performed rst light observations. In the fall of 2012 SuperCam will begin a 500 square degree
survey of the Galactic Plane in <sup>12</sup>CO J=3-2. This large-scale survey will help answer fundamental questions
about the formation, physical conditions, and energetics of molecular clouds within the Milky Way. The data
set will be available via the web to all interested researchers.
The Stratospheric TeraHertz Observatory (STO) is a NASA funded, Long Duration Balloon (LDB) experiment designed to
address a key problem in modern astrophysics: understanding the Life Cycle of the Interstellar Medium (ISM). STO will
survey a section of the Galactic plane in the dominant interstellar cooling line [C II] (1.9 THz) and the important star
formation tracer [N II] (1.46 THz) at ~1 arc minute angular resolution, sufficient to spatially resolve atomic, ionic and
molecular clouds at 10 kpc. STO itself has three main components; 1) an 80 cm optical telescope, 2) a THz instrument
package, and 3) a gondola . Both the telescope and gondola have flown on previous experiments [2,3]. They have been reoptimized
for the current mission. The science flight receiver package will contain four [CII] and four [NII] HEB mixers,
coupled to a digital spectrometer. The first engineering test flight of STO was from Ft. Sumner, NM on October 15, 2009.
The ~30 day science flight is scheduled for December 2011.
We report on both laboratory and telescope integration results from SuperCam, a 64 pixel imaging spectrometer
designed for operation in the astrophysically important 870 micron atmospheric window. SuperCam will be used to
answer fundamental questions about the physics and chemistry of molecular clouds in the Galaxy and their direct
relation to star and planet formation. The SuperCam key project is a fully sampled Galactic plane survey covering over
500 square degrees of the Galaxy in <sup>12</sup>CO(3-2) and <sup>13</sup>CO(3-2) with 0.3 km/s velocity resolution
In the past, all heterodyne focal plane arrays have been constructed using discrete mixers, arrayed in the focal plane.
SuperCam reduces cryogenic and mechanical complexity by integrating multiple mixers and amplifiers into a single
array module with a single set of DC and IF connectors. These modules are housed in a closed-cycle cryostat with a
1.5W capacity 4K cooler. The SuperCam instrument is currently undergoing laboratory testing with four of the eight
mixer array modules installed in the cryostat (32 pixels). Work is now underway to perform the necessary modifications
at the 10m Heinrich Hertz Telescope to accept the SuperCam system. SuperCam will be installed in the cassegrain cabin
of the HHT, including the optical system, IF processing, spectrometers and control electronics. SuperCam will be
integrated with the HHT during the 2009-2010 observing season with 32 pixels installed. The system will be upgraded to
64 pixels during the summer of 2010 after assembly of the four additional mixer modules is completed.
In the wavelength regime between 60 and 300 microns there are a number of atomic and molecular emission lines that
are key diagnostic probes of the interstellar medium. These include transitions of [CII], [NII], [OI], HD, H<sub>2</sub>D+, OH, CO,
and H<sub>2</sub>O, some of which are among the brightest global and local far-infrared lines in the Galaxy. In Giant Molecular
Clouds (GMCs), evolved star envelopes, and planetary nebulae, these emission lines can be extended over many arc
minutes and possess complicated, often self absorbed, line profiles. High spectral resolution (R> 10<sup>5</sup>) observations of
these lines at sub-arcminute angular resolution are crucial to understanding the complicated interplay between the
interstellar medium and the stars that form from it. This feedback is central to all theories of galactic evolution. Large
format heterodyne array receivers can provide the spectral resolution and spatial coverage to probe these lines over
The advent of large format (~100 pixel) spectroscopic imaging cameras in the far-infrared (FIR) will fundamentally
change the way astronomy is performed in this important wavelength regime. While the possibility of such instruments
has been discussed for more than two decades, only recently have advances in mixer and local oscillator technology,
device fabrication, micromachining, and digital signal processing made the construction of such instruments tractable.
These technologies can be implemented to construct a sensitive, flexible, heterodyne array facility instrument for
SOFIA. The instrument concept for StratoSTAR: Stratospheric Submm/THz Array Receiver includes a common user
mounting, control system, IF processor, spectrometer, and cryogenic system. The cryogenic system will be designed to
accept a frontend insert. The frontend insert and associated local oscillator system/relay optics would be provided by
individual user groups and reflect their scientific interests. Rapid technology development in this field makes SOFIA the
ideal platform to operate such a modular, continuously evolving instrument.
We report on the development of SuperCam, a 64 pixel imaging spectrometer designed for operation in the
astrophysically important 870 micron atmospheric window. SuperCam will be used to answer fundamental questions
about the physics and chemistry of molecular clouds in the Galaxy and their direct relation to star and planet formation.
The Supercam key project is a fully sampled Galactic plane survey covering over 500 square degrees of the Galaxy in
12CO(3-2) and 13CO(3-2) with 0.3 km/s velocity resolution.