Publications (4)0 Total impact
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Christopher Groppi,
Christopher Walker,
Craig Kulesa,
Dathon Golish,
Jenna Kloosterman,
Sander Weinreb,
Glenn Jones,
Joseph Barden,
Hamdi Mani,
Tom Kuiper, Jacob Kooi,
Art Lichtenberger
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ABSTRACT: We report on laboratory testing and telescope integration 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 12 CO(3-2) and 13 CO(3-2) with 0.3 km/s velocity resolution. SuperCam will have several times more pixels than any existing spectroscopic imaging array at submillimeter wavelengths. The exceptional mapping speed that will result, combined with the efficiency and angular resolution provided by the HHT will make SuperCam a powerful instrument for probing the history of star formation in our Galaxy and nearby galaxies. 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. Through Galactic surveys, particularly in CO and its isotopomers, the impact of Galactic environment on these phenomena will be realized. These studies will serve as "finder charts" for future focused research (e.g. with ALMA) and markedly improve the interpretation, and enhance the value of numerous contemporary surveys.
01/2010;
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Christopher Groppi,
Christopher Walker,
Craig Kulesa,
Patrick Puetz,
Dathon Golish,
Paul Gensheimer,
Abigail Hedden,
Shane Bussmann,
Sander Weinreb,
Thomas Kuiper, Jacob Kooi,
Glenn Jones,
Joseph Bardin,
Hamdi Mani,
Arthur Lichtenberger,
Gopal Narayanan
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ABSTRACT: We report on the development of SuperCam, a 64 pixel, superheterodyne camera 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 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, 1x8 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. Comment: 12 pages, 14 figures, to be published in the Proceedings of SPIE Vol. 6275, "Astronomical Telescopes and Instrumentation, Millimeter and Submillimeter Detectors and Instrumentation for Astronomy III"
06/2006;
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Christopher Groppi,
Christopher Walker,
Craig Kulesa,
Dathon Golish,
Jenna Kloosterman,
Patrick Pütz,
Sander Weinreb,
Thomas Kuiper, Jacob Kooi,
Glenn Jones,
Joseph Bardin,
Hamdi Mani,
Arthur Lichtenberger,
Thomas Cecil,
Abigail Hedden,
Gopal Narayanan
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ABSTRACT: For future ground, airborne and space based single aperture telescopes, multipixel heterodyne imaging arrays are necessary to take full advantage of platform lifetime, and facilitate science requiring wide field spectral line imaging. A first generation of heterodyne arrays with ~10 pixels has already been constructed, i.e. CHAMP, SMART, HERA, DesertStar, PoleStar and HARP. Our group is now constructing SuperCam, a 64 pixel heterodyne array for operation in the 350 GHz atmospheric window. This instrument will realize another order of magnitude increase in array pixel count. Several new techniques were used for SuperCam to maximize integration and modularity. Unlike other SIS array receivers, SuperCam is built around 8 pixel linear mixer modules, rather than independent mixer blocks. These modules house 8 single ended waveguide mixers with SOI substrate SIS devices. Each device is tab bonded to a MMIC based LNA. These modules dissipate only 8 mW of heat, while still maintaining 5 K IF noise temperature and 32 dB gain. Blind mate IF and DC connectors allow each module to be inserted in or removed from the focal plane as a unit. The modules are machined using a state-of-the-art CNC micromilling machine acquired specifically for this project. IF signals are processed by 8 channel IF downconverter boards, which provide gain, baseband downconversion and IF total power monitoring. A real-time FFT spectrometer implemented with high speed ADCs and Xilinx 4 FPGAs produce spectra of the central 250 MHz of each channel at 0.25 km/s spectral resolution. For arrays with an additional order of magnitude increase in pixel count, several additional technical problems must be overcome. Kilopixel arrays will require advances in device fabrication, cryogenics, micromachining, IF processing and spectrometers. In addition, seemingly straightforward receiver systems will require new approaches to realize a kilopixel heterodyne array with manageable complexity and cost. Wire count and 4K heat load must all be reduced significantly compared to SuperCam. IF and DC cabling and interconnects may be replaced with multiconductor microstrip or stripline ribbon. Parallel biasing of LNAs, magnets and even SIS devices is feasible if device uniformity is good enough. IF processing will require further integration, possibly with integrated MMIC chips containing all parts of a IF downconversion chain. Continued advances in FFT spectrometers could allow processing many hundreds of gigahertz of IF bandwidth for a realizable cost. We present results from final SuperCam receiver integration and testing, and concepts for expanding heterodyne arrays to kilopixel scales in the future.
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ABSTRACT: The advent of large format (~100 pixel) spectroscopic imaging cameras at submillimeter wavelengths would fundamentally change the way in which astronomy is performed in this important wavelength regime. While the possibility of such instruments has been discussed for more than two decades (Gillespie & Philips 1979), only recently have advances in mixer technology, device fabrication, micromachining, digital signal process-ing, and telescope design made the construction of such an instrument possible and economical. In our paper, we will present the design concept for a 10x10 heterodyne camera designed to operate at the prime focus of one of the 8.4 m mirrors of the Large Binocular Telescope, now under construction on Mt. Graham, Arizona. The array will be optimized for spectroscopic studies of galactic star formation regions in the 350 micron atmospheric window. Each pixel of the array will produce an 11" diffraction limited beam. The array field of view will be ~3.7 x 3.7 arc minutes. The unique optical and mechanical design of the LBT allows the instrument to be 'swung' into place in a matter of minutes. The instrument will be fully automated with all 100 spectra available on line after each integration. SuperCam could be ready for observations on the LBT as early as fall 2003.
Institutions
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2010
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Jet Propulsion Laboratory
Pasadena,
CA,
USA
