- Santiago, Region Metropolitana, Chile
We are developing a 16x24 detector array to cover the 40-120 mu m wavelength range for AIRES, the Airborne InfraRed Echelle Spectrometer for SOFIA. Here we describe the design, fabrication, and assembly of a 2x24 prototype module for this... more
We are developing a 16x24 detector array to cover the 40-120 mu m wavelength range for AIRES, the Airborne InfraRed Echelle Spectrometer for SOFIA. Here we describe the design, fabrication, and assembly of a 2x24 prototype module for this array, and the other components required for the full array. The detectors are discrete bulk Ge:Sb photoconductors with 1 mm interelectrode
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Research Interests:
The CO N+ Deuterium Observations Receiver, CONDOR, is one of the very few existing THz heterodyne receivers in the world. It covers a frequency range between 1.25 and 1.53 THz (240mum - 196mum). CONDOR was built with a focus on observing... more
The CO N+ Deuterium Observations Receiver, CONDOR, is one of the very few existing THz heterodyne receivers in the world. It covers a frequency range between 1.25 and 1.53 THz (240mum - 196mum). CONDOR was built with a focus on observing star forming regions, using high-J CO lines H2D+ and N+ In November 2005 we tested CONDOR on the APEX
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ABSTRACT We describe the receiver concept for KOSMA's planned second generation SOFIA instrument STAR (SOFIA Terahertz Array Receiver). The receiver will contain a 4 X 4 element heterodyne mixer array for the frequency range from... more
ABSTRACT We describe the receiver concept for KOSMA's planned second generation SOFIA instrument STAR (SOFIA Terahertz Array Receiver). The receiver will contain a 4 X 4 element heterodyne mixer array for the frequency range from 1.7 to 1.9 THz (158 to 176 microns). Its main scientific goal is large scale mapping of the 158 micron fine structure transition of singly ionized carbon. The design frequency range covers this line out to moderate red shifts and also allows to observe a variety of other spectral lines.
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The German REceiver for Astronomy at Terahertz frequencies (GREAT) is a first generation PI instrument for the SOFIA telescope, developed by a collaboration between the MPIfR, KOSMA, DLR, and the MPAe. The first three institutes each... more
The German REceiver for Astronomy at Terahertz frequencies (GREAT) is a first generation PI instrument for the SOFIA telescope, developed by a collaboration between the MPIfR, KOSMA, DLR, and the MPAe. The first three institutes each contribute one heterodyne receiver channel to operate at 1.9, 2.7 and 4.7 THz, respectively. A later addition of a e.g. 1.4 THz channel is planned. The GREAT instrument is developed to carry two cryostats at once. That means that any two of the three frequencies can be observed simultaneously. Therefore, we need to be able to quickly exchange the optics benches, the local oscillator (LO) subsystems, and the cryostats containing the mixer devices. This demands a high modularity and flexibility of our receiver concept. Our aim is to avoid the need for realignment when swapping receiver channels. After an overview of the common GREAT optics, a detailed description of several parts (optics benches, calibration units, diplexer, focal plane imager) is given. ...
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We describe a focal-plane optics for millimeter-and submillimeter-wave array receivers which are both fully reflectivethus avoiding the absorption and reflection losses of dielectric lensesand expandable to an arbitrary number of... more
We describe a focal-plane optics for millimeter-and submillimeter-wave array receivers which are both fully reflectivethus avoiding the absorption and reflection losses of dielectric lensesand expandable to an arbitrary number of pixels. The optics unit cell consists of ...
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Research Interests:
We present our recent developments for the large format heterodyne array spectrometer CHAI. Operating simultaneously in two wavelength bands (650 um and 350 um) with 64 pixels, CHAI will be used for efficient large scale spectroscopic... more
We present our recent developments for the large format heterodyne array spectrometer CHAI. Operating simultaneously in two wavelength bands (650 um and 350 um) with 64 pixels, CHAI will be used for efficient large scale spectroscopic mapping with the CCAT-prime telescope, which is under construction on Cerro Chajnantor/Chile. The receiver is based on the technology developed for SMART, one of the first submillimeter heterodyne arrays and for upGREAT, the world's leading Terahertz array receiver.
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Research Interests:
In this paper we present the considerations for design and assembly of a stressed gallium doped germanium photoconductor array for the Airborne InfraRed Echelle Spectrometer on SOFIA. This 8 X 12 element array will cover the wavelength... more
In this paper we present the considerations for design and assembly of a stressed gallium doped germanium photoconductor array for the Airborne InfraRed Echelle Spectrometer on SOFIA. This 8 X 12 element array will cover the wavelength range from 125 to 210 micrometers . The considerations cover the aspects of the mechanical design for stressing the detectors in a uniform way, assembly of the components, contacting them electrically with minimized stray capacitance, and the layout of the light collecting cone assembly.
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The humidity of the free troposphere can be modeled, to first order, in terms of cold-point dehydration, followed by moistening via mixing with boundary layer air. The relative balance between these processes is of prime interest for... more
The humidity of the free troposphere can be modeled, to first order, in terms of cold-point dehydration, followed by moistening via mixing with boundary layer air. The relative balance between these processes is of prime interest for understanding interannual variability of humidity and for understanding the water vapor feedback. Measurements of water vapor isotopic composition can provide quantitative constraints on these processes. The authors developed a stochastic model that parameterizes water vapor isotopic composition in terms of these processes and fit the model parameters to data from the Chajnantor Plateau, Chile (23°S). For August–November 2012, the average mixing ratio was 1680 ppmv, with mean water vapor δD of −234‰ and mean deuterium excess of 21‰. The data were best fit by an asymmetric last-saturation distribution with mean last-saturation mixing ratio rs of 391 (+45, −75) ppmv, a median rs of 368 (+45, −75) ppmv, and a mean mixing fraction between the freeze-dried a...
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... 3). This illustrates that astigmatic optics can be calculated and manufactured with high precision and could be also useful for more severe elliptic beams from sources such as quantum cascade lasers as we intend to use in the SOFIA... more
... 3). This illustrates that astigmatic optics can be calculated and manufactured with high precision and could be also useful for more severe elliptic beams from sources such as quantum cascade lasers as we intend to use in the SOFIA THz Array Receiver (STAR) from KOSMA. ...
We present the opto-mechanical layout of KOSMA's (Kölner Observatorium für SubMillimeter Astronomie) submillimeter and terahertz heterodyne array receiver STAR (SOFIA Terahertz Array Receiver) which is derived from SMART (Sub-Millimeter... more
We present the opto-mechanical layout of KOSMA's (Kölner Observatorium für SubMillimeter Astronomie) submillimeter and terahertz heterodyne array receiver STAR (SOFIA Terahertz Array Receiver) which is derived from SMART (Sub-Millimeter Array Receiver for Two frequencies). To reduce the alignment effort, SMART, for the first time, uses an integrated optics concept with no adjustable optical components inside the receiver dewar. For STAR this successful design concept will be extended and adapted for 1.9 THz and for use aboard SOFIA (Stratospheric Observatory For Infrared Astronomy). The design of STAR's cryostat and cryogenic optics is described. Emphasis is laid on the required accuracy for 4x4 spatially multiplexed Terahertz heterodyne receivers. The proposed design of the local oscillator, a frequency-tripled BWO (Backward Wave Oscillator), is outlined. The presentation comprises the scheme for multiplexing the local oscillator, dense arrangement of mixer elements in a cryogenic focal plane and manufacturing techniques of integrated optics units for reduction of optical adjustment efforts in astronomical submillimeter and terahertz receivers.
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The Stratospheric Observatory for Infrared Astronomy, SOFIA, is a joint US and German project and will start observations from altitudes up to 45,000 ft in late 2001. The 2.5 m telescope is being developed in Germany while the 747-... more
The Stratospheric Observatory for Infrared Astronomy, SOFIA, is a joint US and German project and will start observations from altitudes up to 45,000 ft in late 2001. The 2.5 m telescope is being developed in Germany while the 747- aircraft modifications and preparation of the observatory's operations center is done by a US consortium. Several research institutions and universities of both countries have started to develop science instruments. The DLR Institute of Space Sensor Technology in Berlin plans on a spectral-photometric camera working in the 20 to 220 micrometers wavelength range, using doped silicon and germanium extrinsic photoconductors in large, 2D arrays: silicon blocked-impurity band detectors, Ge:Ga and stressed Ge:Ga. While the silicon array will be commercially available, the germanium arrays have to be developed, including their cryogenic multiplexers. Partner institutions in Germany and the US will support the development of the instrument and its observations.
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Abstract ArTeMiS is a bolometer camera that will be installed at the APEX submillimeter telescope in Chile in 2010. This instrument will be a powerful tool for scientists with its three focal planes that will operate simultaneously in... more
Abstract ArTeMiS is a bolometer camera that will be installed at the APEX submillimeter telescope in Chile in 2010. This instrument will be a powerful tool for scientists with its three focal planes that will operate simultaneously in background limited conditions at 200, 350 ...
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Research Interests:
ABSTRACT We report on developments of submillimeter heterodyne arrays for high resolution spectroscopy with APEX. Shortly, we will operate state-of-the-art instruments in all major atmospheric windows accessible from Llano de Chajnantor.... more
ABSTRACT We report on developments of submillimeter heterodyne arrays for high resolution spectroscopy with APEX. Shortly, we will operate state-of-the-art instruments in all major atmospheric windows accessible from Llano de Chajnantor. CHAMP+, a dual-color 2×7 element heterodyne array for operation in the 450 μm and 350 μm atmospheric windows is in operation since late 2007. With its state-of-the-art SIS detectors and wide tunable local oscillators, its cold optics with single sideband filters and with 3 GHz of processed IF bandwidth per pixel, CHAMP+ does provide outstanding observing capabilities. The Large APEX sub-Millimeter Array (LAsMA) is in the final design phase, with an installation goal in 2009. The receiver will operate 7 and 19 pixels in the lower submillimeter windows, 285-375 GHz and 385-520 GHz, respectively. The front-ends are served by an array of digital wideband Fast Fourier Transform spectrometers currently processing up to 32×1.5 (optionally 1.8) GHz of bandwidth. For CHAMP+, we process 2.8 GHz of instantaneous bandwidth (in 16.4 k channels) for each of the 14 pixels.
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ABSTRACT We present the opto-mechanical layout of KOSMA's (Kölner Observatorium für SubMillimeter Astronomie) submillimeter and terahertz heterodyne array receiver STAR (SOFIA Terahertz Array Receiver) which is derived from SMART... more
ABSTRACT We present the opto-mechanical layout of KOSMA's (Kölner Observatorium für SubMillimeter Astronomie) submillimeter and terahertz heterodyne array receiver STAR (SOFIA Terahertz Array Receiver) which is derived from SMART (Sub-Millimeter Array Receiver for Two frequencies). To reduce the alignment effort, SMART, for the first time, uses an integrated optics concept with no adjustable optical components inside the receiver dewar. For STAR this successful design concept will be extended and adapted for 1.9 THz and for use aboard SOFIA (Stratospheric Observatory For Infrared Astronomy). The design of STAR's cryostat and cryogenic optics is described. Emphasis is laid on the required accuracy for 4x4 spatially multiplexed Terahertz heterodyne receivers. The proposed design of the local oscillator, a frequency-tripled BWO (Backward Wave Oscillator), is outlined. The presentation comprises the scheme for multiplexing the local oscillator, dense arrangement of mixer elements in a cryogenic focal plane and manufacturing techniques of integrated optics units for reduction of optical adjustment efforts in astronomical submillimeter and terahertz receivers.
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The Atacama Large Millimeter/submillimeter Array finds itself in the transition into full operations. Previous construction activities are being wrapped up, and regular, repetitive maintenance and upkeep will dominate the daily life,... more
The Atacama Large Millimeter/submillimeter Array finds itself in the transition into full operations. Previous construction activities are being wrapped up, and regular, repetitive maintenance and upkeep will dominate the daily life, which asks for a consolidation and streamlining of the activities at the observatory. Especially the shifting focus to the high site of the observatory deserves more attention, since assembly, integration and verification activities at the base camp have ceased by now. In parallel, adjustments in the host country's labor legislation for operations at high geographic altitudes demand a review of the way things are done. This talk outlines the underlying operational concepts, lists the limiting constraints, describes the implementation of our reactions to those, and outlines our future intentions, which will be one in a number of steps towards optimization of the productivity of the observatory. The latter is the top level goal, which the Joint ALMA Observatory (JAO) has signed up for.
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ArTeMiS is a camera designed to operate on large ground based submillimetric telescopes in the 3 atmospheric windows 200, 350 and 450 µm. The focal plane of this camera will be equipped with 5760 bolometric pixels cooled down at 300 mK... more
ArTeMiS is a camera designed to operate on large ground based submillimetric telescopes in the 3 atmospheric windows 200, 350 and 450 µm. The focal plane of this camera will be equipped with 5760 bolometric pixels cooled down at 300 mK with an autonomous cryogenic system. The pixels have been manufactured, based on the same technology processes as used for
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APEX, the Atacama Pathfinder EXperiment, is being operated successfully, now for five years, on Llano de Chajnantor at 5107m altitude in the Chilean High Andes. This location is considered one of the worlds outstanding sites for... more
APEX, the Atacama Pathfinder EXperiment, is being operated successfully, now for five years, on Llano de Chajnantor at 5107m altitude in the Chilean High Andes. This location is considered one of the worlds outstanding sites for submillimeter astronomy, which the results described in this contribution are underlining. The primary reflector with 12 m diameter is cautiously being maintained at about
Current large observatories, both in operation and projects in development or construction, face the challenge to find skilled personnel for integration and operation. Typical locations of these observatories are found to be remote,... more
Current large observatories, both in operation and projects in development or construction, face the challenge to find skilled personnel for integration and operation. Typical locations of these observatories are found to be remote, mainly due to electromagnetic pollution prevention, which in many if not all cases reduces the attractiveness of the work posts. Additional budgetary limitations restrict the recruitment radius for certain positions to the local labor market. This paper outlines these staffing constraints in more detail and elaborates on the need for training programs on various levels, which can be costly. This, in turn, drives the need for creative retention efforts. Therefore, financial modeling, contingency, risk and quality management, and the reliability, availability, and maintainability of an observatory are directly coupled to the local embedding in the labor market of the host country.
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In this paper we present the considerations for design and assembly of a stressed gallium doped germanium photoconductor array for the Airborne InfraRed Echelle Spectrometer on SOFIA. This 8 X 12 element array will cover the wavelength... more
In this paper we present the considerations for design and assembly of a stressed gallium doped germanium photoconductor array for the Airborne InfraRed Echelle Spectrometer on SOFIA. This 8 X 12 element array will cover the wavelength range from 125 to 210 micrometers . The considerations cover the aspects of the mechanical design for stressing the detectors in a uniform way, assembly of the components, contacting them electrically with minimized stray capacitance, and the layout of the light collecting cone assembly.
Research Interests:
Research Interests:
The collimated optical beam in a grating spectrometer may be circular or elliptical in cross section, so that different parts of the beam illuminate different numbers of grooves on the grating. Here we estimate the consequent loss in... more
The collimated optical beam in a grating spectrometer may be circular or elliptical in cross section, so that different parts of the beam illuminate different numbers of grooves on the grating. Here we estimate the consequent loss in spectral resolution relative to that obtained with a beam that illuminates a fixed number of grooves. The effect reduces the intrinsic resolving power of the spectrometer by approximately 15%, exclusive of other contributions such as finite entrance-slit width.
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The ArTeMiS submillimetric camera will observe simultaneously the sky at 450, 350 and 200 μm using 3 different focal planes made of 2304, 2304 and 1152 bolometric pixels respectively. This camera will be mounted in the Cassegrain cabin of... more
The ArTeMiS submillimetric camera will observe simultaneously the sky at 450, 350 and 200 μm using 3 different focal planes made of 2304, 2304 and 1152 bolometric pixels respectively. This camera will be mounted in the Cassegrain cabin of APEX, a 12 m antenna located on the Chajnantor plateau, Chile. To realize the bolometric arrays, we have adapted the Silicon processing technology used for the Herschel-PACS photometer to account for higher incident fluxes and longer wavelengths from the ground. In addition, an autonomous cryogenic system has been designed to cool the 3 focal planes down to 300 mK. Preliminary performances obtained in laboratory with the first of 3 focal planes are presented. Latest results obtained in 2009 with the P-ArTeMiS prototype camera are also discussed, including massive protostellar cores and several star forming regions that have been clearly identified and mapped.
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In support of characterization of potential sites for the European Extremely Large Telescope (E-ELT) the European Southern Observatory (ESO), the Institute for Space Imaging Science (ISIS) and the astrometeorology group of the Universidad... more
In support of characterization of potential sites for the European Extremely Large Telescope (E-ELT) the European Southern Observatory (ESO), the Institute for Space Imaging Science (ISIS) and the astrometeorology group of the Universidad Valparaiso have jointly established an improved understanding of atmospheric precipitable water vapour (PWV) above ESO's La Silla Paranal Observatory. In a first step, 8 years worth of high resolution near-IR spectra taken with VLT-UVES have been statistically analysed to reconstruct the PWV history above Paranal. To this end a radiative transfer model of Earth's atmosphere (BTRAM) developed by ISIS has been used. A median PWV of 2.1 mm is found for Paranal based on UVES data covering the period 2001-2008. Furthermore we conclude that Paranal can serve as a reference site for Northern Chile due to the stable atmospheric conditions in the region. The median offset between Paranal and Armazones is derived to be 0.3 mm, but local arbitrary variations of a few tenths of a mm between the sites have been found by measurement. In order to better understand the systematics involved two dedicated campaigns were conducted in August and November 2009. Several methods for determining the water column were employed, including radiosonde launches, continuous measurements by infrared radiometer, and VLT instruments operating at various wavelengths: CRIRES, UVES, VISIR and X-shooter. In a first for astronomical instruments all methods have been evaluated with respect to the radiosondes, the established standard in atmospheric research. Agreement between the radiosondes and the IR radiometer (IRMA) is excellent while all other astronomical methods covering a wavelength range from 700 - 20000 nm have also been successfully validated in a quantitative manner. All available observations were compared to satellite estimates of water vapour above the observatory in an attempt to ground-truth the satellite data. GOES can successfully be used for site evaluation in a purely statistical approach since agreement with the radiosondes is very good on average. For use as an operational tool at an observatory GOES data are much less suited because of significant deviations depending on atmospheric conditions. We propose to routinely monitor PWV at the VLT and to use it as an operational constraint to guide scheduling of IR observations at Paranal. For the E-ELT we find that a stand-alone high time resolution PWV monitor will be essential for optimizing the scientific output.
Research Interests: Observational Astronomy, Infrared Astronomy, Atmospheric Water Vapor, Site Characterization (Hydrogeology), Astronomy, and 10 moreSatellite Data, High Resolution, Infrared, Observatory, Northern Chile, Acoustic Radiative Transfer Model, Water vapour, Ground Truth, Statistical Approach, and Site testing
The content of precipitable water vapor (PWV) in the atmosphere is very important for astronomy in the infrared and radio (sub-millimeter) spectral regions. Therefore, the astrometeorology group has developed different methods to derive... more
The content of precipitable water vapor (PWV) in the atmosphere is very important for astronomy in the infrared and radio (sub-millimeter) spectral regions. Therefore, the astrometeorology group has developed different methods to derive this value from measurements and making forecasts using a meteorological model. The goal is use that model to predict the atmospheric conditions and support the scheduling of astronomical observations. At ESO, several means to determine PWV over the observatories have been used, such as IR-radiometers (IRMA), optical and infrared spectrographs as well as estimates using data from GOES-12 satellite. Using all of these remote sensing methods a study undertaken to compare the accuracy of these PWV measurements to the simultaneous in-situ measurements provided by radiosondes. Four dedicated campaigns were conducted during the months of May, July, August and November of 2009 at the La Silla, APEX and Paranal observatory sites. In addition, the astrometeorological group employs the WRF meteorological model with the goal of simulating the state of the atmosphere (every 6 hours) and forecasting the PWV. With these simulations, plus satellite images, radiosonde campaign data can be classified synoptically and at the same time the model can be validated with respect to PWV.
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Research Interests:
The THz atmospheric windows centered at roughly 1.3 and 1.5~THz, contain numerous spectral lines of astronomical importance, including three high-J CO lines, the N+ line at 205 microns, and the ground transition of para-H2D+. The CO lines... more
The THz atmospheric windows centered at roughly 1.3 and 1.5~THz, contain numerous spectral lines of astronomical importance, including three high-J CO lines, the N+ line at 205 microns, and the ground transition of para-H2D+. The CO lines are tracers of hot (several 100K), dense gas; N+ is a cooling line of diffuse, ionized gas; the H2D+ line is a non-depleting tracer of cold (~20K), dense gas. As the THz lines benefit the study of diverse phenomena (from high-mass star-forming regions to the WIM to cold prestellar cores), we have built the CO N+ Deuterium Observations Receiver (CONDOR) to further explore the THz windows by ground-based observations. CONDOR was designed to be used at the Atacama Pathfinder EXperiment (APEX) and Stratospheric Observatory For Infrared Astronomy (SOFIA). CONDOR was installed at the APEX telescope and test observations were made to characterize the instrument. The combination of CONDOR on APEX successfully detected THz radiation from astronomical sources. CONDOR operated with typical Trec=1600K and spectral Allan variance times of 30s. CONDOR's first light observations of CO 13-12 emission from the hot core Orion FIR4 (= OMC1 South) revealed a narrow line with T(MB) = 210K and delta(V)=5.4km/s. A search for N+ emission from the ionization front of the Orion Bar resulted in a non-detection. The successful deployment of CONDOR at APEX demonstrates the potential for making observations at THz frequencies from ground-based facilities.
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The CO N+ Deuterium Observations Receiver, CONDOR, is one of the very few existing THz heterodyne receivers in the world. It covers a frequency range between 1.25 and 1.53 THz (240μm - 196μm). CONDOR was built with a focus on observing... more
The CO N+ Deuterium Observations Receiver, CONDOR, is one of the very few existing THz heterodyne receivers in the world. It covers a frequency range between 1.25 and 1.53 THz (240μm - 196μm). CONDOR was built with a focus on observing star forming regions, using high-J CO lines H2D+ and N+ In November 2005 we tested CONDOR on the APEX telescope, and successfully observed CO 13-12 in several regions in Orion. In FIR4 we find a surprisingly narrow CO 13-12 line width (5.4 km/s), from which we conclude that the hot gas is probably radiatively heated rather than shock excited. The observations of NGC2024 reviled additional hot gas. In order to model the CO lines between J= 3-2 and J=13-12 consistently a model with molecular gas in 4 different layers is required. High spectral resolution observations in the THz regime allow us not only to probe gas otherwise diffcult to observe, but also to obtain information about the structure and kinematics of the source.
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Research Interests:
... Symp. Space THz Technol. 15 (2004), pp. 248254. [10] D. Rabanus, U. Graf, M. Philipp, J. Stutzki and A. Wagner, Cryogenic design of KOSMA's SOFIA terahertz array receiver (STAR), SPIE: Airborne Telescope Systems 5498... more
... Symp. Space THz Technol. 15 (2004), pp. 248254. [10] D. Rabanus, U. Graf, M. Philipp, J. Stutzki and A. Wagner, Cryogenic design of KOSMA's SOFIA terahertz array receiver (STAR), SPIE: Airborne Telescope Systems 5498 (2004), pp. 473480. Full Text via CrossRef. ...
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We demonstrate for the first time the closure of an electronic phase lock loop for a continuous-wave quantum cascade laser (QCL) at 1.5 THz. The QCL is operated in a closed cycle cryo cooler. We achieved a frequency stability of better... more
We demonstrate for the first time the closure of an electronic phase lock loop for a continuous-wave quantum cascade laser (QCL) at 1.5 THz. The QCL is operated in a closed cycle cryo cooler. We achieved a frequency stability of better than 100 Hz, limited by the resolution bandwidth of the spectrum analyser. The PLL electronics make use of the intermediate frequency (IF) obtained from a hot electron bolometer (HEB) which is downconverted to a PLL IF of 125 MHz. The coarse selection of the longitudinal mode and the fine tuning is achieved via the bias voltage of the QCL. Within a QCL cavity mode, the free-running QCL shows frequency fluctuations of about 5 MHz, which the PLL circuit is able to control via the Stark-shift of the QCL gain material. Temperature dependent tuning is shown to be nonlinear, and of the order of -16 MHz/K. Additionally we have used the QCL as local oscillator (LO) to pump an HEB and perform, again for the first time at 1.5 THz, a heterodyne experiment, and obtain a receiver noise temperature of 1741 K.
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... The KOSMA 1 group is part of a consortium developing the German receiver for astronomy at terahertz frequencies (GREAT) [1], a first generation instrument for the stratospheric observatory for infrared astronomy (SOFIA) [2]. Covering... more
... The KOSMA 1 group is part of a consortium developing the German receiver for astronomy at terahertz frequencies (GREAT) [1], a first generation instrument for the stratospheric observatory for infrared astronomy (SOFIA) [2]. Covering the frequencies of 1.61.9, 2.42.7 and 4.7 ...
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Research Interests:
... A numerical simulation and an application for KOSMA's 1.9 THz local oscillator for the GREAT instrument on SOFIA gives evidence supporting the theory. Keywords: Gaussian optics; Off-axis mirror; Astigmatic optics. Article... more
... A numerical simulation and an application for KOSMA's 1.9 THz local oscillator for the GREAT instrument on SOFIA gives evidence supporting the theory. Keywords: Gaussian optics; Off-axis mirror; Astigmatic optics. Article Outline. ...
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Research Interests:
GREAT, the German REceiver for Astronomy at Terahertz frequencies, is a first generation SOFIA dual channel heterodyne PI-instrument for high resolution spectroscopy. The system is developed by a consortium of German research institutes.... more
GREAT, the German REceiver for Astronomy at Terahertz frequencies, is a first generation SOFIA dual channel heterodyne PI-instrument for high resolution spectroscopy. The system is developed by a consortium of German research institutes. The receiver will allow simultaneous observations in two out of the following three far-infrared frequency bands: * a low-frequency (1.4-1.9 THz) channel for e.g. the fine-structure lines of ionized nitrogen [NII] at 205μm and ionized carbon [CII] at 158μm * a mid-frequency (2.4-2.7 THz) channel for e.g. the 112μm transition of HD; and * a high-frequency (4.7 THz channel) for the 63 μm fine-structure line of neutral atomic oxygen. Hot electron bolometers (HEB) mixers provide state of the art sensitivity. A spectral resolving power of up to 108 is achieved with chirp transform spectrometers, and a total bandwidth of 4 GHz at 1 MHz resolution is reached with wide band acousto-optical spectrometers. The modular concept of GREAT allows to observe with any combination of two out of the three channels aboard SOFIA. A more complete frequency coverage of the THz regime by adding additional GREAT channels is possible in the future. The adaptation of new LO-, mixer- or backend-techniques is easily possible. We describe details of the receiver and the results of first performance tests of the system at 1.9 THz. As an outlook to future developments we show first results obtained with phase locking a quantum cascade laser, the most promising option for future high power local oscillators in the Terahertz regime.
Research Interests: Submillimetre astronomy, Low Frequency, Astronomy, High Frequency, Airborne Remote sensing, and 11 moreTerahertz, Nitrogen, Atomic Oxygen, Millimeter and Submillimeter Wave Antennas, Phase Locking, Fine Structure Constant, High Power, Far Infrared, Receiver, Heterodyne Linewidth Measurement, and Performance Test
NGC 2024, a sites of massive star formation, have complex internal structures caused by cal heating by young stars, outflows, and stellar winds. These complex cloud structures lead to intricate emission line shapes. The goal of this paper... more
NGC 2024, a sites of massive star formation, have complex internal structures caused by cal heating by young stars, outflows, and stellar winds. These complex cloud structures lead to intricate emission line shapes. The goal of this paper is to show that the complex line shapes of 12 CO lines in NGC 2024 can be explained consistently with a model, whose temperature and velocity structure are based on the well-established scenario of a PDR and the Blister model. We present velocity-resolved spectra of seven CO lines ranging from J=3 to J=13, and we combined these data with CO high-frequency data from the ISO satellite. We find that the bulk of the molecular cloud associated with NGC 2024 consists of warm (75 K) and dense (9e5 cm-3) gas. An additional hot (~ 300 K) component, located at the interface of the HII region and the molecular cloud, is needed to explain the emission of the high-J CO lines. Deep absorption notches indicate that very cold material (20 K) exists in front of the warm material, too. A temperature and column density structure consistent with those predicted by PDR models, combined with the velocity structure of a Blister model, appropriately describes the observed emission line profiles of this massive star forming region. This case study of NGC 2024 shows that, with physical insights into these complex regions and careful modeling, multi-line observations of CO can be used to derive detailed physical conditions in massive star forming regions.
Research Interests:
GREAT, the German REceiver for Astronomy at Terahertz frequencies, is a first generation SOFIA dual channel heterodyne PI-instrument for high resolution spectroscopy. The system is developed by a consortium of German research institutes.... more
GREAT, the German REceiver for Astronomy at Terahertz frequencies, is a first generation SOFIA dual channel heterodyne PI-instrument for high resolution spectroscopy. The system is developed by a consortium of German research institutes. The receiver will allow simultaneous observations in two out of the following three far-infrared frequency bands: a 1.4-1.9 THz channel for e.g. the fine-structure line of ionized carbon [CII] at 158μm a 2.4-2.7 THz channel for e.g. the 112μm transition of HD; and a 4.7 THz channel for the 63 μm fine-structure line of neutral atomic oxygen. Hot electron bolometers (HEB) mixers provide state of the art sensitivity. A spectral resolving power of up to 108 is achieved with chirp transform spectrometers, and a total bandwidth of 4 GHz at 1 MHz resolution is reached with wide band acousto-optical spectrometers. The modular concept of GREAT allows to observe with any combination of two out of the three channels aboard SOFIA. A more complete frequency coverage of the THz regime by adding additional GREAT channels is possible in the future. The adaptation of new LO-, mixer- or backend-techniques is easily possible. We describe details of the receiver and the results of first performance tests of the system at 1.9 THz.
Research Interests: Submillimetre astronomy, Low Frequency, Astronomy, High Frequency, Airborne Remote sensing, and 11 moreTerahertz, Nitrogen, Atomic Oxygen, Millimeter and Submillimeter Wave Antennas, Phase Locking, Fine Structure Constant, High Power, Far Infrared, Receiver, Heterodyne Linewidth Measurement, and Performance Test
The spectral-photometric infrared camera SPICA is proposed as one of the German science instruments of the Stratospheric Observatory for Infrared Astronomy, SOFIA. It will cover a wavelength range of 20 to 220 µm with three large area... more
The spectral-photometric infrared camera SPICA is proposed as one of the German science instruments of the Stratospheric Observatory for Infrared Astronomy, SOFIA. It will cover a wavelength range of 20 to 220 µm with three large area detector arrays (Si-BIB, Ge:Ga and stressed Ge:Ga). In its imaging mode SPICA will provide unpresedented diffraction limited spatial resolution in the far-infrared with the 2.5 m SOFIA telescope. In addition, low resolution ( 20) imaging spectroscopy using the "3D-principle" is planned. While the silicon array will be commercially available, the germanium arrays have to be developed, including their cryogenic multiplexers. The overall concept, camera optics and the detector array design have been developed by the DLR Institute of Space Sensor Technology (Institut fuer Weltraumsensorik) in Berlin. Several German and U.S. partners are interested to support the instrument development. However, due to funding constraints SPICA will probably not be one of the first-light instruments on SOFIA.
Research Interests:
The spectral-photometric infrared camera SPICA is proposed as one of the German science instruments of the Stratospheric Observatory for Infrared Astronomy, SOFIA. It will cover a wavelength range of 20 to 220 μm with three large area... more
The spectral-photometric infrared camera SPICA is proposed as one of the German science instruments of the Stratospheric Observatory for Infrared Astronomy, SOFIA. It will cover a wavelength range of 20 to 220 μm with three large area detector arrays (Si-BIB, Ge:Ga and stressed Ge:Ga). With the 2.5 m SOFIA telescope, SPICA will provide unprecedented diffraction limited spatial resolution in the far-infrared. In addition, low resolution 3D-imaging spectroscopy (λ/Δλ ≡ 20) is planned. While the silicon array will be commercially available, the germanium arrays are being developed, including their cryogenic multiplexers. The overall instrument concept, its camera optics and the status of the detector development are presented.