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In a radio interferometer, the determination of geometrical antenna positions relies on accurate calibration of the dry and wet delay of the atmosphere above each antenna. For the Atacama Large Millimeter/Submillimeter Array (ALMA), which has baseline lengths up to 16 kilometers, the geography of the site forces the height above mean sea level of the more distant antenna pads to be significantly lower than the central array. Thus, both the ground level meteorological values and the total water column can be quite different between antennas in the extended configurations. During 2015, a network of six additional weather stations was installed to monitor pressure, temperature, relative humidity and wind velocity, in order to test whether inclusion of these parameters could improve the repeatability of antenna position determinations in these configurations. We present an analysis of the data obtained during the ALMA Long Baseline Campaign of Oct. through Nov. 2015. The repeatability of antenna position measurements typically degrades as a function of antenna distance. Also, the scatter is more than three times worse in the vertical direction than in the local tangent plane, suggesting that a systematic effect is limiting the measurements. So far we have explored correcting the delay model for deviations from hydrostatic equilibrium in the measured air pressure and separating the partial pressure of water from the total pressure using water vapor radiometer (WVR) data. Correcting for these combined effects still does not provide a good match to the residual position errors in the vertical direction. One hypothesis is that the current model of water vapor may be too simple to fully remove the day-to-day variations in the wet delay. We describe possible avenues of improvement, including measuring and applying more accurate values of the sky coupling efficiency of the WVRs., 19 pages, 14 figures, 1 table; presented at SPIE Astronomical Telescopes + Instrumentation 2016, held in Edinburgh, UK on 26 June - 1 July 2016

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., 10 pages, 5 figures, accepted by A&A for publication

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 and 450 microns (5760 pixels in total). A prototype called p-ArTeMiS has been tested at APEX in 2007 and thanks to its good performances, the team has been able to conduct scientific projects in star formation and on debris disks. This paper summarises the details of the ArTeMiS project, with a description of the detectors, the optics, the cryogenics and the electronics. We will also present the undergoing studies at CEA on detectors for the future submillimeter space missions.

Studying molecular gas in the central regions of the star burst galaxies NGC4945 and Circinus enables us to characterize the physical conditions and compare them to previous local and high-z studies. We estimate temperature, molecular density and column densities of CO and atomic carbon. Using model predictions we give a range of estimated CO/C abundance ratios. Using the new NANTEN2 4m sub-millimeter telescope in Pampa La Bola, Chile, we observed for the first time CO 4-3 and [CI] 3P1-3 P0 at the centers of both galaxies at linear scale of 682 pc and 732 pc respectively. We compute the cooling curves of 12CO and 13CO using radiative transfer models and estimate the physical conditions of CO and [CI]. The centers of NGC4945 and Circinus are very [CI] bright objects, exhibiting [CI] 3P1 - 3 P0 luminosities of 91 and 67Kkms-1kpc2, respectively. The [CI] 3P1-3 P0/CO 4-3 ratio of integrated intensities are large at 1.2 in NGC4945 and 2.8 in Circinus. Combining previous CO J= 1-0, 2-1 and 3-2 and 13CO J= 1-0, 2-1 studies with our new observations, the radiative transfer calculations give a range of densities, n(H2) = 10^3-3*104^cm-3, and a wide range of kinetic temperatures, Tkin = 20 - 100K, depending on the density. Future CO J= 7-6 and [CI] 2-1 observations will be important to resolve the ambiguity in the physical conditions and confirm the model predictions.

The 1.9 THz local-oscillator (LO) of the GREAT heterodyne receiver is presented. The LO is based on a frequency tripled backward-wave oscillator source. The frequency stabilization system is described and an astigmatic imaging system, developed for improved beam coupling, is presented. Allan variances and temperature dependent power drifts are analyzed. The LO is designed as a stand-alone system and fits into GREAT’s local-oscillator compartments. It produces more than 1.5 μW of stable output power to pump the hot electron bolometer mixers of the GREAT instrument.

In Gaussian Optics, beams with a circular cross section can easily be matched by using off-axis mirrors. Since the E -field distribution of a Gaussian beam mode is entirely independent in the two directions perpendicular to its axis of propagation, it is also possible to employ the formalism for asymmetric beams. Conventional off-axis mirrors, however, are not suitable to properly match these elliptical beams. In this case, astigmatic optics are required. This paper presents a method of designing astigmatic off-axis mirrors for Gaussian beam modes starting from a conventional off-axis mirror. 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.

This paper presents a method to manufacture a low loss window applicable for THz frequencies. The window is made out of high resistivity silicon (3 kΩ cm, n = 3.42, and α = 0.1/cm). Reflective loss due to the impedance mismatch between the substrate and free space is overcome by etching (Bosch-process) rectangular grooves of depth λ /4 into the substrate as an antireflection (AR) layer. The refractive index of the AR-layer depends on the incident wave mode (TE/TM), i.e., the AR-layer is a birefringent medium. A short theoretical description is given. Simulation of the AR-layer was done by using a transmission line analogue and the Scatter -program written by Padman. FTS measurements yield a transmittance greater than 96% at 2.1 THz and a band width of 400 GHz (1.9–2.3 THz) with ⩾90% transmission.

For astrophysical applications at submillimeter wavelengths, efficient coupling of the feed horn pattern in the focal plane to the radiation pattern of the telescope is paramount. To date, at 840 GHz with high band width, corrugated feed horns have been used with very good results. The goal of developing instruments for KOSMA above 1 THz where state-of-the-art heterodyne systems are still governed by receiver noise rather than by radiative background, requires fabrication of corrugated structures of the order of λ/3 or less. This is non-trivial, and here we present the performance of a smooth-walled spline-profile feed horn, which is considerably easier to manufacture compared to a corrugated feed horn. The performance is assessed via radiation patterns in H, E and 45° D-Plane in co- and cross-polarization.

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.

The ALMA Test Interferometer appeared as an infrastructure solution to increase both ALMA time availability for science activities and time availability for Software testing and Engineering activities at a reduced cost (

Aims. We aim at deriving the excitation conditions of the interstellar gas as well as the local FUV intensities in the molecular cloud surrounding NGC 3603 to get a coherent picture of how the gas is energized by the central stars.Methods. The NANTEN2-4 m submillimeter antenna is used to map the [CI] 1-0, 2-1 and CO 4-3, 7-6 lines in a 2' x 2' region around the young OB cluster NGC 3603 YC. These data are combined with C(18)O 2-1 data, HIRES-processed IRAS 60 mu m and 100 mu m maps of the FIR continuum, and Spitzer/IRAC maps.Results. The NANTEN2 observations show the presence of two molecular clumps located south-east and south-west of the cluster and confirm the overall structure already found by previous CS and C(18)O observations. We find a slight position offset of the peak intensity of CO and [CI], and the atomic carbon appears to be further extended compared to the molecular material. We used the HIRES far-infrared dust data to derive a map of the FUV field heating the dust. We constrain the FUV field to values of chi = 3-6 x 10(3) in units of the Draine field across the clouds. Approximately 0.2 to 0.3% of the total FUV energy is re-emitted in the [CII] 158 mu m cooling line observed by ISO. Applying LTE and escape probability calculations, we derive temperatures (T(MM1) = 43 K, T(MM2) = 47 K), column densities (N(MM1) = 0.9 x 10(22) cm(-2), N(MM2) = 2.5 x 10(22) cm(-2)) and densities (n(MM1) = 3 x 10(3) cm(-3), n(MM2) = 10(3) - 10(4) cm(-3)) for the two observed molecular clumps MM1 and MM2.Conclusions. The cluster is strongly interacting with the ambient molecular cloud, governing its structure and physical conditions. A stability analysis shows the existence of gravitationally collapsing gas clumps which should lead to star formation. Embedded IR sources have already been observed in the outskirts of the molecular cloud and seem to support our conclusions.

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.

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.

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 15 μm by means of holography. This allows to access all atmospheric submillimeter windows accessible from the ground, up to 200 μm. Telescope and instrument performance, operational experiences and a selection of scientific results are given in this publication.

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.

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 the Herschel-PACS space photometer. We review in this paper the present status and the future plans of this project. A prototype camera, named P-ArTeMiS, has been developed and successfully tested on the KOSMA telescope in 2006 at Gornergrat 3100m, Switzerland. Preliminary results were presented at the previous SPIE conference in Orlando (Talvard et al, 2006). Since then, the prototype camera has been proposed and successfully installed on APEX, a 12 m antenna operated by the Max Planck Institute fur Radioastronomie, the European Southern Observatory and the Onsala Space Observatory on the Chajnantor site at 5100 m altitude in Chile. Two runs have been achieved in 2007, first in March and the latter in November. We present in the second part of this paper the first processed images obtained on star forming regions and on circumstellar and debris disks. Calculated sensitivities are compared with expectations. These illustrate the improvements achieved on P-ArTeMiS during the 3 experimental campaigns.

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.

Star formation at earlier cosmological times takes place in an interstellar medium with low metallicity. The Large Magellanic Cloud (LMC) is ideally suited to study star formation in such an environment. The physical and chemical state of the ISM in a star forming environment can be constrained by observations of submm and FIR spectral lines of the main carbon carrying species, CO, CI and CII, which originate in the surface layers of molecular clouds illuminated by the UV radiation of the newly formed, young stars. We present high-angular resolution sub-millimeter observations in the N159W region in the LMC obtained with the NANTEN2 telescope of the 12CO J = 4-3, J = 7-6, and 13CO J = 4-3 rotational and [CI] 3P1-3P0 and 3P2-3P1 fine-structure transitions. The 13CO J =4-3 and [CI] 3P2-3P1 transitions are detected for the first time in the LMC. We derive the physical and chemical properties of the low-metallicity molecular gas using an escape probability code and a self-consistent solution of the chemistry and thermal balance of the gas in the framework of a clumpy cloud PDR model. The separate excitation analysis of the submm CO lines and the carbon fine structure lines shows that the emitting gas in the N159W region has temperatures of about 80 K and densities of about 10^4 cm^-3. The estimated C to CO abundance ratio close to unity is substantially higher than in dense massive star-forming regions in the Milky Way. The analysis of all observed lines together, including the [CII] line intensity reported in the literature, in the context of a clumpy cloud PDR model constrains the UV intensity to about \chi ~220 and an average density of the clump ensemble of about 10^5 cm^-3, thus confirming the presence of high density material in the LMC N159W region., Comment: Accepted for publication to A&A. 14 pages, 7 figures (3 in Color), 3 tables. A version with high resolution figures available at http://www.astro.uni-bonn.de/~jopineda/pega/n159w_paper.pdf

The Carina region is an excellent astrophysical laboratory for studying the feedback mechanisms of newly born, very massive stars within their natal giant molecular clouds (GMCs) at only 2.35 kpc distance. We use a clumpy PDR model to analyse the observed intensities of atomic carbon and CO and to derive the excitation conditions of the gas. The NANTEN2-4m submillimeter telescope was used to map the [CI] 3P1-3P0, 3P2-3P1 and CO 4-3, 7-6 lines in two 4'x4' regions of Carina where molecular material interfaces with radiation from the massive star clusters. One region is the northern molecular cloud near the compact OB cluster Tr14, and the second region is in the molecular cloud south of etaCar and Tr16. These data were combined with 13CO SEST spectra, HIRES/IRAS 60um and 100um maps of the FIR continuum, and maps of 8um IRAC/Spitzer and MSX emission. We used the HIRES far-infrared dust data to create a map of the FUV field heating the gas. The northern region shows an FUV field of a few 1000 in Draine units while the field of the southern region is about a factor 10 weaker. We constructed models consisting of an ensemble of small spherically symmetric PDR clumps within the 38" beam (0.43pc), which follow canonical power-law mass and mass-size distributions. We find that an average local clump density of 2x10**5 cm-3 is needed to reproduce the observed line emission at two selected interface positions. Stationary, clumpy PDR models reproduce the observed cooling lines of atomic carbon and CO at two positions in the Carina Nebula., Comment: accepted by A&A

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.

We present the opto-mechanical layout of KOSMA's (Kolner Observatorium fur 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.

We present the concept for KOSMA's 16 element 1.9 THz heterodyne array STAR (SOFIA Terahertz Array Receiver) which is being developed for SOFIA. The instrument will consist of two interleaved sub-arrays of 8 pixels each. Together we will have a 4 × 4 pixel array with a beam spacing on the sky of approximately 1.5 times the beam size of 15 arcsec (FWHM). The receiver is mainly targeted at measuring the fine structure transition of ionized atomic carbon at 1.9 THz (158 microns). STAR's optics setup is modeled after the successful design used in KOSMA's SMART receiver. It will contain a K-mirror type beam rotator, a Martin-Puplett diplexer for LO coupling and an LO multiplexer using imaging Fourier gratings. Complete optical sub-assemblies will be machined monolithically as integrated optics units, to reduce the need for optical alignment. STAR will probably use waveguide mixers with diffusion cooled hot electron bolometers, which are being developed at KOSMA. The receiver backends will be KOSMA Array-AOSs. Local oscillator power will be provided by a backward wave oscillator (BWO), followed by a frequency tripler.

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.

The spectral-photometric IR camera SPICA is proposed as one of the German science instruments of the Stratospheric Observatory for IR Astronomy (SOFIA). It will cover a wavelength range of 20-220 micrometers with three large area detector arrays. With the 2.5 m SOFIA telescope, SPICA will provide unprecedented diffraction limited spatial resolution in the far-IR. In addition, low resolution 3D-imaging spectroscopy 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 will be presented. The instrument is being developed by the DLR Institute of Space Sensor Technology in Berlin with support of several German and US partners.

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.

CONDOR, the CO, N+, Deuterium Observations Receiver, is designed to make velocity-resolved observations of the CO, [NII], and p-H2D+ lines in the 1.4 THz (200-240μm) atmospheric windows. CONDOR's first light observations were made with the APEX telescope in November 2005. The CONDOR beam on APEX (at ν = 1.5 THz) was expected to consist of a 4.3″ main beam and a 73″ error beam; this beam structure was verified from scans of Mars. The pointing accuracy, also determined from Mars scans, was better than 7″. The average atmospheric transmission during our Orion observations (elev~57°) was 19 ± 4% along the line-of-sight. A forward efficiency of Feff = 0.8 was determined from sky dips, and observations of the Moon and Mars were used to couple the CONDOR beam to sources of different sizes (ηc = 0.40 and ~0.10, respectively). For more information, see Wiedner et al. 2006.

We describe a focal-plane optics for millimeter- and submillimeter-wave array receivers which are both fully reflective—thus avoiding the absorption and reflection losses of dielectric lenses—and expandable to an arbitrary number of pixels. The optics unit cell consists of two mirrors and a feedhorn optimized for near-field operation. Employing an integrated optics approach the mirror setup consists of only three mechanical parts, independent of the number of pixels, and requires no internal optical alignment. With a 345GHz 3×3-beam prototype a Gaussicity of ⩾98% and a focal-plane beam separation of 3.6 waist radii was obtained. In this article we present the optics design as well as numerical simulations and measured beam patterns.