The monochromatic single frame pixel count of a camera is limited by diffraction to the space-bandwidth product, roughly the aperture area divided by the square of the wavelength. We have recently shown that it is possible to approach this limit using multiscale lenses for cameras with space bandwidth product between 1 and 100 gigapixels. When color, polarization, coherence and time are included in the image data cube, camera information capacity may exceed 1 petapixel/second. This talk reviews progress in the construction of DARPA AWARE gigapixel cameras and describes compressive measurement strategies that may be used in combination with multiscale systems to push camera capacity to near physical limits.
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 12CO 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.
We present an architecture for rapid spectral classification in spectral imaging applications. By making use of knowledge
gained in prior measurements, our spectral imaging system is able to design adaptive feature-specific measurement
kernels that selectively attend to the portions of a spectrum that contain useful classification information. With
measurement kernels designed using a probabilistically-weighted version of principal component analysis, simulations
predict an orders-of-magnitude reduction in classification error rates. We report on our latest simulation results, as well
as an experimental prototype currently under construction.
The DARPA MOSAIC program applies multiscale optical design (shared objective lens and parallel array of microcameras)
to the acquisition of high pixel count images. Interestingly, these images present as many challenges
as opportunities. The imagery is acquired over many slightly overlapping fields with diverse focal, exposure and
temporal parameters. Estimation of a consensus image, display of imagery at human-comprehensible resolutions,
automated anomaly detection to guide viewer attention, and power management in a distributed electronic environment
are just a few of the novel challenges that arise. This talk describes some of these challenges and
presents progress to date.
The size of existing and projected submillimeter heterodyne receiver arrays is rapidly increasing. As receiver arrays
grow ever larger, the local oscillator power they require increases as well. We have developed Terahertz (THz)
Traveling Wave Tube Amplifiers (TWTA) that promise to provide more than enough power in the 200 to 700 GHz
frequency range to pump the largest arrays being planned for submillimeter telescopes. This technology combines
revolutionary carbon nanotube cathodes and electron gun design with unique software modeling and micro-fabrication
capabilities. We review key enabling technologies that make this breakthrough possible, present the design, realization,
computer models and preliminary results of the THz TWT we have fabricated at 220 and 350 GHz
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 12CO(3-2) and 13CO(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.
Many of the most astrophysically important transitions of atoms and molecules occur at THz frequencies. These
transitions allow us to probe the formation and evolution of stars, planets, galaxies, and even the Universe itself. A
recent confluence of technologies involving mixers, local oscillators, micromachining, IF amplifiers, and digital signal
processing now make the fabrication of large format (~1000 pixel), heterodyne arrays at THz frequencies possible.
Planned observatories at high altitude sites (e.g. the high Atacama and Dome A in Antarctica) and in the stratosphere
(e.g. SOFIA and balloon-borne telescopes) can serve as platforms from which THz arrays can provide unprecedented
access to a powerful window to the Universe. In this paper the scientific impact and technical roadmap to the realization
and implementation of THz arrays will be discussed.
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.
Pre-HEAT is a 20 cm aperture submillimeter-wave telescope with a 660 GHz (450 micron) Schottky diode heterodyne
receiver and digital FFT spectrometer for the Plateau Observatory (PLATO) developed by the University of New South
Wales. In January 2008 it was deployed to Dome A, the summit of the Antarctic plateau, as part of a scientific traverse
led by the Polar Research Institute of China and the Chinese Academy of Sciences. Dome A may be one of the best sites
in the world for ground based Terahertz astronomy, based on the exceptionally cold, dry and stable conditions which
prevail there. Pre-HEAT is measuring the 450 micron sky opacity at Dome A and mapping the Galactic Plane in the
13CO J=6-5 line, constituting the first submillimeter measurements from Dome A. It is field-testing many of the key
technologies for its namesake -- a successor mission called HEAT: the High Elevation Antarctic Terahertz telescope.
Exciting prospects for submillimeter astronomy from Dome A and the status of Pre-HEAT will be presented.
We report on the development of SuperCam, a 64 pixel, superheterodyne camera designed for operation in the astrophysically important 870 μm 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
advent of such a system will provide an order of magnitude increase in mapping speed over what is now available and
revolutionize how observational astronomy is performed in this important wavelength regime.
Unlike the situation with bolometric detectors, heterodyne receiver systems are coherent, retaining information about
both the amplitude and phase of the incident photon stream. From this information a high resolution spectrum of the
incident light can be obtained without multiplexing. SuperCam will be constructed by stacking eight, 1×8 rows of fixed
tuned, SIS mixers. The IF output of each mixer will be connected to a low-noise, broadband MMIC amplifier integrated
into the mixer block. The instantaneous IF bandwidth of each pixel will be ~2 GHz, with a center frequency of 5 GHz.
A spectrum of the central 500 MHz of each IF band will be provided by the array spectrometer. Local oscillator power
is provided by a frequency multiplier whose output is divided between the pixels by using a matrix of waveguide power
dividers. The mixer array will be cooled to 4K by a closed-cycle refrigeration system. SuperCam will reside at the
Cassegrain focus of the 10m Heinrich Hertz telescope (HHT). A prototype single row of the array will be tested on the
HHT in 2006, with the first engineering run of the full array in late 2007. The array is designed and constructed so that
it may be readily scaled to higher frequencies.
Precise astronomical polarization measurements generally require the use of polarization modulation. We have developed a new modulator, the Variable-delay Polarization Modulator (VPM) which uses two modified Martin- Puplett interferometers to induce a physical path length difference between polarization components. This highly durable and efficient device can easily be adapted to a wide range of wavelengths and temperatures, making it well suited for air- and space-borne facilities. This paper discusses the basic modulator design and a comparison to the half-wave plate, as well as details of VPM tests conducted at the Submillimeter Telescope Observatory (SMTO).
We report on a novel approach for implementing a dual Bracewell nulling interferometric beam combiner using miniature conductive waveguides contained in a single monolithic structure. We present modeling results for these devices at mid-infrared wavelengths. Potential applications for these devices in the Terrestrial Planet Finder mission are discussed.
Feedhorns like those commonly used in radio-telescope and radio communication equipment couple very efficiently (>98%) to the fundamental Gaussian mode (TEM00). High order modes are not propagated through a single-mode hollow metallic waveguides. It follows that a back to back feedhorn design joined with a small length of single-mode waveguide can be used as a very high throughput spatial filter. Laser micro machining provides a mean of scaling successful waveguide and quasi-optical components to far and mid infrared wavelengths. A laser micro machining system optimized for THz and far IR applications has been in operation at Steward Observatory for several years and produced devices designed to operate at λ=60μm. A new laser micromachining system capable of producing mid-infrared devices will soon be operational. These proceedings review metallic hollow waveguide spatial filtering theory, feedhorn designs as well as laser chemical etching and the design of a new high-NA UV laser etcher capable of sub-micron resolution to fabricate spatial filters for use in the mid-infrared.
We present the first astronomical results from DesertSTAR, a 7 pixel heterodyne array receiver designed for operation in the astrophysically rich 345 GHz atmospheric window. DesertSTAR was constructed for the 10m Heinrich Hertz Telescope located at 3150m elevation on Mt. Graham, Arizona. This receiver promises to increase mapping speed at the HHT by a factor of ~15 over the facility's existing single beam, dual polarization receiver. DesertSTAR uses tunerless, single-ended waveguide SIS mixers to achieve uncorrected receiver noise temperatures of ~60K. The instantaneous bandwidth is 2 GHz, with a 5 GHz Intermediate Frequency, offering 1600 km/s of velocity coverage. Cryogenic isolators are employed between the mixers and low noise amplifiers to assure a flat IF passband. The system uses a Joule-Thompson closed-cycle refrigerator with 180W capacity at 70K and 1.8W capacity at 4K. A novel reflective phase grating is used for Local Oscillator multiplexing, while a simple Mylar beamsplitter is used as an LO diplexer. Optics include only polyethelene mixer lenses and a single, cold, flat mirror, maximizing simplicity for high efficiency and easy optical alignment. The computer controlled bias system provides low noise bias for the SIS junctions, magnets and LNAs through a modular and hardware independent GUI interface, and allows remote operation and monitoring. We present measurements of receiver noise, beam quality, efficiency and stability in addition to astronomical observations obtained during engineering runs at the HHT.
We have proposed to develop a prototype 0.5-meter far-infrared telescope and heterodyne receiver/spectrometer system for fully-automated 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. HEAT, the High Elevation Antarctic Terahertz Telescope, will operate in the atmospheric windows between 150 and 400 microns, in which the most crucial astrophysical spectral diagnostics of the formation of galaxies, stars, planets, and life are found. At these wavelengths, HEAT will have high aperture efficiency and excellent atmospheric transmission most of the year. The proposed superheterodyne receiver system will be comprised of 0.8, 1.4 and 1.9 THz channels which will observe the pivotal J=7-6 line of CO, the J=2-1 line of atomic carbon, and the far-infrared fine structure lines of N+ and C+, the brightest emission lines in the entire Milky Way Galaxy. When combined with the HEAT telescope, the receiver system represents a uniquely powerful instrument for reconstructing the history of star formation in our Galaxy, with application to the distant Universe. The receiver system itself serves as a valuable testbed for heterodyne Terahertz components, using leading-edge mixer, local oscillator, low-noise amplifier, cryogenic, and digital signal processing technologies that will play essential roles in future Terahertz observatories. The proposed study will pave the way for future astronomical investigations from Dome A.
Laser induced, micro-chemical etching is a promising new technology that can be used to fabricate three dimensional structures many millimeters across with micrometer accuracy. Laser micromachining possesses a significant edge over more conventional techniques. It does not require the use of masks and is not confined to crystal planes. A non-contact process, it eliminates tool wear and vibration problems associated with classical milling machines. At the University of Arizona we have constructed the first such laser micromaching system optimized for the fabrication of THz and far IR waveguide and quasi-optical components. Our system can machine many millimeters across down to a few microns accuracy in a short time, with a remarkable surface finish. This paper presents the design, operation and performance of our system, and its applications to waveguide devices for sub millimeter and far IR interferometry.
DesertSTAR is a 7 beam, 345 GHz heterodyne array receiver for the Heinrich Hertz Telescope (HHT) on Mt. Graham, AZ. The instrument uses fixed-backshort Superconductor-Insulator-Superconductor (SIS) mixers with a broadband waveguide probe. Instantaneous bandwidths greater than 2 GHz can be achieved over the entire 345 GHz atmospheric window. A cryostat with a Joule-Thompson (JT) mechanical refrigerator allows continuous operation and 1.8W of cooling capacity at 4K, and provides the needed temperature stability for low-noise operation. Local Oscillator (LO) distribution is accomplished with a novel phase grating that yields high efficiency and power uniformity in a hexagonally symmetric geometry. The computer controlled bias system is an evolution of a proven design that is simple and portable to any computer platform. The 2 GHz Intermediate Frequency (IF) bandwidth allows the future addition of a wideband backend optimized for extragalactic observations, with ~1700 km/s of velocity coverage. We present measurements of receiver performance and plans for integration on the HHT.
Based on the excellent performance of NbN HEB mixer receivers at THz frequencies which we have established in the laboratory, we are building a Terahertz REceiver with NbN HEB Device (TREND) to be installed on the 1.7 meter diameter AST/RO submillimeter wave telescope at the Amundsen/Scott South Pole Station. TREND is scheduled for deployment during the austral summer season of 2002/2003. The frequency range of 1.25 THz to 1.5 THz was chosen in order to match the good windows for atmospheric transmission and interstellar spectral lines of special interest. The South Pole Station is the best available site for THz observations due to the very cold and dry atmosphere over this site. In this paper, we report on the design of this receiver. In particular, we report on HEB mixer device performance, the quasi-optical coupling design using an elliptical silicon lens and a twin-slot antenna, the laser local oscillator (LO), as well as the mixer block design and the plans for coupling the TREND receiver to the sky beam and to the laser LO at the AST/RO telescope site.
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