Search

We report the detection and interferometric localization of the repeating fast radio burst (FRB) source FRB 20220912A during commissioning observations with the Deep Synoptic Array (DSA-110). Two bursts were detected from FRB 20220912A, one each on 2022 October 18 and 2022 October 25. The best-fit position is (R.A. J2000, decl. J2000) = (23:09:04.9, +48:42:25.4), with a 90% confidence error ellipse of $\pm2$ arcsec and $\pm1$ arcsec in right ascension and declination respectively. The two bursts have disparate polarization properties and temporal profiles. We find a Faraday rotation measure that is consistent with the low value of $+0.6$ rad m$^{-2}$ reported by CHIME/FRB. The DSA-110 localization overlaps with the galaxy PSO J347.2702+48.7066 at a redshift $z=0.0771$, which we identify as the likely host. PSO J347.2702$+$48.7066 has a stellar mass of approximately $10^{10}M_{\odot}$, modest internal dust extinction, and a star-formation rate likely in excess of $0.1\,M_{\odot}$ yr$^{-1}$. The host-galaxy contribution to the dispersion measure is likely $\lesssim50$ pc cm$^{-3}$. The FRB 20220912A source is therefore likely viewed along a tenuous plasma column through the host galaxy., Comment: 10 pages, 7 figures, 2 tables, submitted to AAS Journals

We present the Galactic Radio Explorer (GReX), an all-sky monitor to probe the brightest bursts in the radio sky. Building on the success of STARE2, we will search for fast radio bursts (FRBs) emitted from Galactic magnetars as well as bursts from nearby galaxies. GReX will search down to ten microseconds time resolution, allowing us to find new super giant radio pulses from Milky Way pulsars and study their broadband emission. The proposed instrument will employ ultra-wide band (0.7-2 GHz) feeds coupled to a high performance (receiver temperature 10 K) low noise amplifier (LNA) originally developed for the DSA-110 and DSA-2000 projects. In GReX Phase I (GReX-I), unit systems will be deployed at Owens Valley Radio Observatory (OVRO) and Big Smoky Valley, Nevada. Phase II will expand the array, placing feeds in India, Australia, and elsewhere in order to build up to continuous coverage of nearly 4$\pi$ steradians and to increase our exposure to the Galactic plane. We model the local magnetar population to forecast for GReX, finding the improved sensitivity and increased exposure to the Galactic plane could lead to dozens of FRB-like bursts per year.

We have developed a programmable, fast switching, accurate, and miniaturized calibration load for use in millimeter and submillimeter low-noise amplifier characterization, and Earth/planetary science radiometers. The proposed solution uses a thermally conductive waveguide vane attenuator with low thermal mass, integrated heater, and silicon thermometer. In the present design, we utilize a 125- $\mu$ m-thick z-cut crystal quartz vane due to its low dielectric constant (relative to silicon), high cryogenic thermal conductivity, chemical robustness, and small thermal contraction. To provide adequate attenuation, the bottom side of the quartz fabrication wafer has an nm thick resistive Ti metal layer deposited. On the top of the quartz wafer, a pattern of Au is deposited to allow adhesion of the heater resistor, thermometer, and internal heat strap. The z-cut quartz vane is mounted on three low thermally conductive Torlon posts, centered on the maximum E-field, and positioned across the waveguide. With this approach the quartz vane, protruding all the way into the waveguide, approximates a blackbody with a physical temperature T . The design uniqueness lies in the choice of cryogenically suitable materials coupled with detailed thermal analyses and proper miniaturization. When operated in a proportional $-$ integral $-$ derivative loop, these properties combine to facilitate a programmable calibration load with a switching speed of $\lesssim$ 10 s. It will be shown that the W-band design operates overmoded to $\sim$ 230 GHz and that the concept is in principle scalable to terahertz frequencies.

This communication proposes a compact, high performance, quadruple-ridged flared horn operating from 8 to 50 GHz. A prototype fed by two coaxial connectors has been designed and fabricated based on the combination of a four-petal structure and a back plate. Measurements show that the input reflection coefficients are below −10 dB over more than 6:1 frequency range. Radiation patterns were measured in an anechoic chamber, and good agreement was found with the simulation results. Physical optics calculations predict an average of 68% aperture efficiency with the feed installed on the square kilometer array shaped offset Gregorian reflector. The horn is a good demonstration at very high frequencies of a wideband feed for radio telescopes.

This paper presents a novel ultra-low-loss high-pass filter with 3 dB cutoff frequency of 890 MHz for astronomical receiver radio frequency interference mitigation application. The filter consists of three series capacitors, four shunt inductors, and microstrip circuit board. Specially, 4 shunt inductors are actualized by fabricating air-core short-circuit coaxial cable inductors in the filter box body, and the quality factor of these cable inductors is up to 762.2 and 1046, respectively, at 1.4 GHz. In the expected passband of 1.1–1.9 GHz, S parameters measurement show that insertion loss is lower than 0.16 dB and two-port return loss is larger than 20 dB; noise measurement show that filter noise temperature is lower than 8 at 300 K ambient temperature. Noise sources of this filter are analyzed by simulation and measurement.

This letter presents an ultra-low loss cryogenically-coolable lumped element high pass filter and the measurement method of its S parameters and noise temperature at cryogenic temperature. This filter is going to be used in RFI mitigation of FAST wideband single pixel receiver. It adopts 5 poles Chebyshev high pass structure, and ultra-low loss lumped elements are employed. At cryogenic temperature, its 3 dB cutoff frequency is 248 MHz and the high-end of passband with ultra-low insertion loss is up to 3.5 GHz. Specially, the novel mechanical and microwave design ensure effectively cryogenic cooling to all components of the filter. This filter can be operated at temperatures of 300-4 K. S parameters are measured at room and cryogenic temperatures. At 26 K, its insertion loss in passband is smaller than 0.1 dB. A direct measurement to noise temperature at 24 K physical temperature is performed in cryogenic Testing Dewar, and noise temperature smaller than 0.55 K is achieved. The stopband rejection at 95 MHz is larger than 43 dB. In passband, the return loss of 2 ports is larger than 23 dB.

A dual beam, dual polarization, low noise receiver has been installed at a Cassegrain focus of the NASA 70[Formula: see text]m antenna near Canberra, Australia. It operates in five pairs of 1[Formula: see text]GHz bands from 17 to 27[Formula: see text]GHz simultaneously. The receiver temperature measured at the feed is 21–22[Formula: see text]K at 22[Formula: see text]GHz and, during dry winter night-time conditions, zenith system temperatures as low as 35[Formula: see text]K have been observed in the 21–22[Formula: see text]GHz band. The native polarization is linear but can be converted to circular prior to down-conversion. The downconverters have complex mixers, followed by quadrature hybrids which can be bypassed or used to convert the quadrature phase channels into an upper and lower sideband, each 1000[Formula: see text]MHz wide. For spectroscopy, four ROACH1 signal processors each currently providing 32[Formula: see text]K channel spectra across four 1000[Formula: see text]MHz bands, for 0.4[Formula: see text]km/s velocity resolution at 22[Formula: see text]GHz. Using both beam- and position-switching, the receiver achieved a noise level of 5[Formula: see text]mK r.m.s. in an hour of integration and 31[Formula: see text]kHz resolution. The NASA 70[Formula: see text]m antennas have a 45 arcsec beamwidth at 22[Formula: see text]GHz and an aperture efficiency of 35.5% giving a sensitivity of 0.49[Formula: see text]K/Jy.

Intense, millisecond-duration bursts of radio waves have been detected from beyond the Milky Way [1]. Their extragalactic origins are evidenced by their large dispersion measures, which are greater than expected for propagation through the Milky Way interstellar medium alone, and imply contributions from the intergalactic medium and potentially host galaxies [2]. Although several theories exist for the sources of these fast radio bursts, their intensities, durations and temporal structures suggest coherent emission from highly magnetised plasma [3,4]. Two sources have been observed to repeat [5,6], and one repeater (FRB 121102) has been localised to the largest star-forming region of a dwarf galaxy at a cosmological redshift of 0.19 [7, 8]. However, the host galaxies and distances of the so far non-repeating fast radio bursts are yet to be identified. Unlike repeating sources, these events must be observed with an interferometer with sufficient spatial resolution for arcsecond localisation at the time of discovery. Here we report the localisation of a fast radio burst (FRB 190523) to a few-arcsecond region containing a single massive galaxy at a redshift of 0.66. This galaxy is in stark contrast to the host of FRB 121102, being a thousand times more massive, with a greater than hundred times lower specific star-formation rate. The properties of this galaxy highlight the possibility of a channel for FRB production associated with older stellar populations., Submitted version of article published online at Nature via Accelerated Article Preview (https://doi.org/10.1038/s41586-019-1389-7). 34 pages, 6 figures, 2 tables

We have implemented a single wideband receiver package that could cover the 8 to 48 GHz frequency range of the ngVLA. The current JVLA covers this frequency range employing five distinct receiver packages. We estimate that reducing the number of receiving systems required to cover the full frequency range should reduce operating costs. The receiver package we developed consists of a quad-ridge feed horn, low-noise amplifiers (LNA), and a down-converter to analog intermediate frequencies. Both the feedhorn and the LNA are cryogenically cooled. On the LNA front we pursued two 8–48 GHz MMIC designs, the first using 70-nm gallium arsenide, metamorphic high-electron-mobility-transistors (HEMT), and the second using 35-nm indium phosphide HEMTs. In this paper, we report the measured gain and noise temperatures of these LNAs.

The Deep Synoptic Array 10 dish prototype is an instrument designed to detect and localise fast radio bursts with arcsecond accuracy in real time. Deployed at Owens Valley Radio Observatory, it consists of ten 4.5m diameter dishes, equipped with a 250MHz bandwidth dual polarisation receiver, centered at 1.4GHz. The 20 input signals are digitised and field programmable gate arrays are used to transform the data to the frequency domain and transmit it over ethernet. A series of computer servers buffer both raw data samples and perform a real time search for fast radio bursts on the incoherent sum of all inputs. If a pulse is detected, the raw data surrounding the pulse is written to disk for coherent processing and imaging. The prototype system was operational from June 2017 - February 2018 conducting a drift scan search. Giant pulses from the Crab pulsar were used to test the detection and imaging pipelines. The 10-dish prototype system was brought online again in March 2019, and will gradually be replaced with the new DSA-110, a 110-dish system, over the next two years to improve sensitivity and localisation accuracy., Comment: 10 pages, 13 figures, accepted by MNRAS

The additive noise (i.e., noise figure) in the 1-Hz-1-GHz range and multiplicative noise (i.e., gain fluctuations) in the 1-Hz-100-kHz range have been measured for six different types of high electron mobility transistors and two heterojunction bipolar transistors. The instrumentation enables measurement of multiplicative noise as small as 10-6 (1 ppm). Measurements were performed at 300 and 22 K and results are discussed with regard to transistor technology, coupling of additive and multiplicative effects, and bias circuit dependence. The results are applied to radiometers and the degradation in performance due to the gain fluctuation is presented.

The noise models of InP and GaAs HEMTs are compared with measurements at both 300 and 20 K. The critical parameter, Tdrain, in the Pospieszalski noise model is determined as a function of drain current by measurements of the 1-GHz noise of discrete transistors with 50- Ω generator impedance. The dc I-V for the transistors under test are presented and effects of impact-ionization are noted. InP devices with both 100% and 75% indium mole fraction in channel are included. Examples of the design and measurement of very wideband low-noise amplifiers (LNAs) using the tested transistors are presented. At 20-K physical temperature the GaAs LNA achieves 10-K noise over the 0.7-16-GHz range with 16 mW of power and an InP LNA measures 20-K noise over the 6-50-GHz range with 30 mW of power.

This paper presents a new technique to reject the radio frequency interference (RFI) from the nearby radar at 9.4 GHz, which causes about 20% blockage of the sky coverage in the Very Long Baseline Inter ferometry (VLBI) telescope at the Goddard Geophysical Astronomical Observatory (GGAO), in Greenbelt, MD. An internal notch filter is proposed by inserting and optimizing two-quarter wavelength slots within the wide band Quad-Ridge Flared Horn (QRFH) feed to achieve RFI band rejection at 9.4 GHz. The simulated result shows about 95 % rejection at 9.4 GHz. The estimated attenuation due to the band rejection slots is of the order of .01 dB at frequencies distant from the rejection frequency. This technique will open the door for designing wideband feeds with RFI band rejection characteristics for different RFI sources.

A unique wide band receiver for radio astronomy has been designed, constructed and will be installed on the 500 m Aperture Spherical Telescope (FAST) in Guizhou, China. The receiver has a frequency range of 270 to 1620 MHz. Astronomical use of the receiver includes observing pulsars, continuum source surveys, galactic hydrogen line and extragalactic hydrogen with high red shift.

A numerical model is used for accurately calculating the temperature along a coaxial line with ends at different cryogenics temperatures. The calculations take into account the variation of thermal and electrical conductivity with temperature, an important consideration not present in previous publications. Estimates of line attenuation and added noise temperature can be more accurately calculated using this profile, and the profile can provide insight into thermal clamp position and thermal loading calculations. These calculations have a significant impact on the accuracy of variable temperature load and cold attenuator noise measurements.

Due to copyright restrictions, the access to the full text of this article is only available via subscription. In this paper we discuss the design of low-noise amplifiers (LNAs) for both cryogenic and room-temperature operation in general and take the stability and linearity of the amplifiers into special consideration. Oscillations that can occur within a multi-finger transistor are studied and verified with simulations and measurements. To overcome the stability problem related to the multi-finger transistor design approach a parallel two-finger unit transistor monolithic microwave integrated circuit LNA design technique, which enables the design of wideband and high-linearity LNAs with very stable, predictable, and repeatable operation, is proposed. The feasibility of the proposed design technique is proved by demonstrating a three-stage LNA packaged in a WR10 waveguide housing and fabricated using a 35-nm InP HEMT technology that achieves more than a 20-dB gain from 75 to 116 GHz and 26-33-K noise temperature from 85 to 116 GHz when cryogenically cooled to 27 K. Jet Propulsion Laboratory, California Institute of Technology ; Oak Ridge Associated Universities under NASA Postdoctoral Program (NPP) ; Academy of Finland ; Alfred Kordel Foundation ; National Aeronautics and Space Administration

This report presents results of recent work on the design of a wideband cryogenic low noise amplifier (LNA). The amplifier operates from 200 MHz to 6 GHz with noise temperatures of 2.8 K and 4.5 K at 1.6 GHz and 5.2 GHz respectively. Design, fabrication and cryogenic test results will be described.

State-of-the-art radio astronomy terahertz receivers utilize clusters of super-conducting mixers with cryogenic IF amplifiers. The critical parameters of the IF amplifiers are noise temperature, bandwidth, power consumption, input return loss, and physical size. This paper presents test data on three approaches to the IF amplifier; two are silicon-germanium (SiGe) monolithic microwave integrated circuit designs and the third is a discrete SiGe transistor miniature module. The amplifiers provide noise temperatures in the range of 5-15 K, from 1 to 6 GHz, at power consumptions as low as 2 mW.

A system for measuring the noise parameters of a device at cryogenic temperatures is described. The method includes the thermal calibration of a module consisting of a noise diode, a dispersive coupling network, a temperature sensor, heater, and a bias-tee. The magnitude and phase of the reflection coefficient presented by the module vary rapidly with frequency and the noise output of the module can be thermally calibrated by changing the temperature of the module with an internal heater. The resulting variable impedance-calibrated noise source can be used to measure noise parameters of transistors or amplifiers over a frequency range of 0.4 to 12 GHz via the wideband frequency-variation method. The calibration scheme is not unique to the module and may be applied in general to any noise source. Calibration and noise parameter measurements are made at cryogenic temperatures on a discrete transistor and two different low-noise amplifiers. The results are compared against theoretical values and those obtained using independent measurements. To the best of the authors' knowledge, this is the first measurement of a transistor's noise parameters at cryogenic temperatures using such techniques.

A wideband Radio Telescope was designed and built for use in the Goldstone Apple Valley Radio Telescope (GAVRT) program. It uses an existing 34-m antenna retrofitted with a tertiary offset mirror placed at the vertex of the main reflector. It can be rotated to allow using two feeds that cover the 0.5-14-GHz band. The feed for 4.0-14.0 GHz is a cryogenically cooled, commercially available, open-boundary quadridge horn from ETS-Lindgren. Coverage from 0.5 to 4.0 GHz is provided by an uncooled lower frequency version of the same feed that uses a cooled LNA. The measured aperture efficiency is greater than 40% over much of the band.

The THz spectral region includes a number of important transitions which allow us to trace the evolution of the interstellar medium. Because of the opacity of the atmosphere in this spectral range, the best sites for ground-based THz observations are on the Antarctic Plateau; of these sites, Dome A is expected to be the best. THz survey science can be carried out with small telescopes, easing logistical constraints. By deploying a submillimetre-wave tipper/ telescope to Dome A, we have trialled several technologies for such an instrument, and we are able to test whether the site quality is sufficient for THz surveys.

This paper describes a method for designing cryogenic silicon-germanium (SiGe) transistor low-noise amplifiers and reports record microwave noise temperature, i.e., 2 K, measured at the module connector interface with a 50-Omega generator. A theory for the relevant noise sources in the transistor is derived from first principles to give the minimum possible noise temperature and optimum generator impedance in terms of dc measured current gain and transconductance. These measured dc quantities are then reported for an IBM SiGe BiCMOS-8HP transistor at temperatures from 295 to 15 K. The measured and modeled noise and gain for both a single-and two-transistor cascode amplifier in the 0.2-3-GHz range are then presented. The noise model is then combined with the transistor equivalent-circuit elements in a circuit simulator and the noise in the frequency range up to 20 GHz is compared with that of a typical InP HEMT.

We report on heterodyne measurements at submillimeter wavelengths using a receiver with a Superconductor-Insulator-Superconductor (SIS) mixer device and a Microwave Monolithic Integrated Circuit (MMIC) cryogenic low noise amplifier (LNA) module integrated into the same block. The mixer characterization presented in this work demonstrates the feasibility of operating a MMIC LNA in close proximity to the SIS device without penalty in mixer performance due to heating effects. Verification of this functionality is crucial for the ongoing development of SuperCam, a 64-pixel focal plane array receiver consisting of eight, 1 × 8 integrated mixer/LNA modules. The test setup included a mixer block modified to accept a MMIC amplifier. Our tests show that the LNA can be operated over a broad range of Vdrain voltages from 0.40–1.40 V, corresponding to dissipative powers of 2.6–29 mW. We observe no significant effect on the measured uncorrected receiver noise temperatures in the 345 GHz band.

In this paper we propose a parallel two-finger unit transistor MMIC low-noise amplifier design technique which enables the design of wideband and high linearity low-noise amplifiers with very stable, predictable, and repeatable operation. We prove the feasibility of the proposed design technique by demonstrating a three-stage LNA packaged in a WR10 waveguide housing and fabricated using a 35-nm InP HEMT technology that achieves more than a 20-dB gain from 75 to 116 GHz and 26–33-K noise temperature from 85 to 116 GHz when cryogenically cooled to 27 K.

The combination of the traveling wave OMT device and the ultra-low-noise MMIC amplifiers has allowed us to develop a broadband 6-8 GHz receiver with a noise temperature of around 10 K. The combination of receiver noise and the additional noise contributions by the telescope optics gives an overall receiver temperature of around 28 K and 34 K in the two polarizations. The large collecting area of the telescope gives rise to a system equivalent flux density of around 4.5 Jy at 7 GHz

In this paper, we demonstrate non-destructive cryogenic probing of monolithic microwave integrated circuit (MMIC) amplifiers at W-band and discuss the implications for the development of large-format focal plane arrays for radio astronomy. Using a purpose-built cryogenic probe station to measure S-parameters and noise temperature of MMIC low-noise amplifiers (LNAs), an order of magnitude increase in efficiency can be achieved when compared with measurements on individually packaged amplifiers. The amplifiers are tested non-destructively, which enables selection based on cryogenic noise and gain; this is crucial for the development of highly-integrated miniaturized receivers for focal plane arrays, such as those used for the measurement of the cosmic microwave background (CMB) polarization and future arrays aimed at probing the epoch of reionization (EoR).

We report on the laboratory testing of KAPPa, a 16-pixel proof-of-concept array to enable the creation THz imaging spectrometer with ~1000 pixels. Creating an array an order of magnitude larger than the existing state of the art of 64 pixels requires a simple and robust design as well as improvements to mixer selection, testing, and assembly. Our testing employs a single pixel test bench where a novel 2D array architecture is tested. The minimum size of the footprint is dictated by the diameter of the drilled feedhorn aperture. In the adjoining detector block, a 6mm × 6mm footprint houses the SIS mixer, LNA, matching and bias networks, and permanent magnet. We present an initial characterization of the single pixel prototype using a computer controlled test bench to determine Y-factors for a parameter space of LO power, LO frequency, IF bandwidth, magnet field strength, and SIS bias voltage. To reduce the need to replace poorly preforming pixels that are already mounted in a large format array, we show techniques to improve SIS mixer selection prior to mounting in the detector block. The 2D integrated 16-pixel array design has been evolved as we investigate the properties of the single pixel prototype. Carful design of the prototype has allowed for rapid translation of single pixel design improvements to be easily incorporated into the 16-pixel model.

We report results on the cryogenic operation of two different monolithic X-band silicon-germanium (SiGe) heterojunction bipolar transistor low noise amplifiers (LNAs) implemented in a commercially-available 130 nm SiGe BiCMOS platform. These SiGe LNAs exhibit a dramatic reduction in noise temperature with cooling, yielding Teff of less than 21 K (0.3 dB noise figure) across X-band at a 15 K operating temperature. To the authors’ knowledge, these SiGe LNAs exhibit the lowest broadband noise of any Si-based LNA reported to date.

In this paper we present the design and measurement results, both on-wafer and in package, of an ultra-low-noise and wideband monolithic microwave integrated circuit (MMIC) amplifier in the frequency range of 75 to 116 GHz. The three-stage amplifier packaged in a WR10 waveguide housing and fabricated using a 35-nm InP HEMT technology achieves a record noise temperature of 23 K at 108 GHz when cryogenically cooled to 27 K. The measured gain is 22 to 27 dB for frequency range of 75 to 116 GHz. Furthermore, the amplifier utilizes four-finger devices with a total gate width of 60 μm resulting in higher output power. Therefore, we consider that this amplifier achieves state-of-the-art performance in terms of bandwidth, noise temperature, gain, and linearity so far reported for cryogenically cooled amplifiers around W-band.

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 ^(12)CO J=3-2. This large-scale survey will help answer fundamental questions about the formation, physical conditions, and energetics of molecular clouds within the Milky Way. The data set will be available via the web to all interested researchers.

KAPPa (the Kilopixel Array Pathfinder Project) is developing key technologies to enable the construction of heterodyne focal plane arrays in the terahertz frequency regime with ~1000 pixels. The leap to ~1000 pixels requires solutions to several key technological problems before the construction of such a focal plane is possible. The KAPPa project will develop a small (16-pixel) 2D integrated heterodyne focal plane array for the 660 GHz atmospheric window as a technological pathfinder towards future kilopixel heterodyne focal plane arrays.

Five versions of monolithic W-band 0.1 /spl mu/m AlGaAs-InGaAs-GaAs pseudomorphic HEMT, four-stage, low noise amplifiers based on two different designs were developed. These millimeter wave monolithic integrated circuits have produced a minimum noise figure of 3.5 dB with 23.0 dB gain at 92 GHz and a maximum gain of 33.5 dB with a 6.2 dB noise figure at 102 GHz. This is the highest gain yet reported for a single chip W-band amplifier. The chips feature coplanar waveguide circuit elements and compact size for low-cost production, single-polarity bias requirement, and a minimum of DC bonding pads. >

The state of the art for feeds and LNAs with frequency ranges approaching one decade will be presented. These components reduce the cost of receivers required to cover a given frequency range and enable observations requiring large bandwidth such as spectral index measurements, search for spectral lines with unknown red shift, and detection of transient events. An example of a 2 to 12 GHz feed will be given and compared in efficiency with an octave band feed. Low noise amplifiers for the 0.5 to 12 GHz range utilizing HEMT and SiGe bipolar transistor will be described.

A quad-ridged, flared horn achieving nearly constant beamwidth and excellent return loss over a 6∶1 frequency bandwidth is presented. Radiation pattern measurements show excellent beamwidth stability from 2 to 12 GHz. Measured return loss is > 10 dB over the entire band and > 15 dB from 2.5 to 11 GHz. Using a custom physical optics code, system performance of a radio telescope is computed and predicted performance is average 70% aperture efficiency and 10 Kelvin of antenna noise temperature.

We have recently equipped the 34-meter DSS-28 radio telescope at the Goldstone Deep Space Communications Complex with a novel wide bandwidth radiometer and digital signal processor as part of the Goldstone Apple Valley Radio Telescope (GAVRT) educational outreach program operated by the Jet Propulsion Laboratory and the Lewis Center for Educational Research. The system employs a cryogenically cooled wide bandwidth quad-ridge feed and InP low noise amplifiers to achieve excellent noise performance from 2.7 to 14 GHz; a fractional bandwidth better than 4:1. Four independently tunable dual-polarization receivers each down-convert a 2 GHz block to baseband, providing access to 8 GHz of instantaneous bandwidth. A flexible FPGA-based signal processor has been constructed using CASPER FPGA hardware and tools to take advantage of this enormous bandwidth. This system demonstrates many of the enabling wide bandwidth technologies that will be crucial to maximizing the utility of future large centimeter-wavelength arrays, in particular the Square Kilometer Array. The GAVRT program has previously used narrow bandwidth total power radiometers to study flux variability of quasars and the outer planets. The versatility of DSS-28 will enable other projects including spectroscopy and SETI. Finally, the wide instantaneous bandwidth available makes this system uniquely suited for studying transient radio pulses. A configuration of the digital signal processor has been developed which provides the capability of recording a burst of raw baseband voltage data triggered by a real-time incoherent dedispersion system which is very sensitive to pulses from a known source, such as the Crab Nebula pulsar.

The Stratospheric TeraHertz Observatory (STO) is a NASA funded, Long Duration Balloon (LDB) experiment designed to address a key problem in modern astrophysics: understanding the Life Cycle of the Interstellar Medium (ISM). STO will survey a section of the Galactic plane in the dominant interstellar cooling line [C II] (1.9 THz) and the important star formation tracer [N II] (1.46 THz) at ~1 arc minute angular resolution, sufficient to spatially resolve atomic, ionic and molecular clouds at 10 kpc. STO itself has three main components; 1) an 80 cm optical telescope, 2) a THz instrument package, and 3) a gondola [1]. Both the telescope and gondola have flown on previous experiments [2,3]. They have been reoptimized for the current mission. The science flight receiver package will contain four [CII] and four [NII] HEB mixers, coupled to a digital spectrometer. The first engineering test flight of STO was from Ft. Sumner, NM on October 15, 2009. The ~30 day science flight is scheduled for December 2011.

We report on 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. 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.

The first 42 elements of the Allen Telescope Array (ATA-42) are beginning to deliver data at the Hat Creek Radio Observatory in Northern California. Scientists and engineers are actively exploiting all of the flexibility designed into this innovative instrument for simultaneously conducting surveys of the astrophysical sky and conducting searches for distant technological civilizations. This paper summarizes the design elements of the ATA, the cost savings made possible by the use of COTS components, and the cost/performance trades that eventually enabled this first snapshot radio camera. The fundamental scientific program of this new telescope is varied and exciting; some of the first astronomical results will be discussed., Special Issue of Proceedings of the IEEE: "Advances in Radio Telescopes", Baars,J. Thompson,R., D'Addario, L., eds, 2009, in press

In this letter, the design and measurement of the first SiGe integrated-circuit LNA specifically designed for operation at cryogenic temperatures is presented. At room temperature, the circuit provides greater than 25.8 dB of gain with an average noise temperature (T_e) of 76 K (NF = 1 dB) and S11 of -9 dB for frequencies in the 0.1-5 GHz band. At 15 K, the amplifier has greater than 29.6 dB of gain with an average Te of 4.3 K and S11 of -14.6 dB for frequencies in the 0.1-5 GHz range. To the authors' knowledge, this is the lowest noise ever reported for a silicon integrated circuit operating in the low microwave range and the first matched wideband cryogenic integrated circuit LNA that covers frequencies as low as 0.1 GHz.

We have constructed an 810 GHz receiver system incorporating a HIFI Band-3 superconductor-insulator-superconductor (SIS) mixer developed for Herschel space observatory and a wide-band SiGe low noise amplifier (LNA) designed at Caltech. The instrument is currently installed at the RLT telescope (elevation 5500 m) in northern Chile. Hot/cold (280K/72K) load measurements performed at the telescope yield noise temperatures of 225 K (Y-factor = 1.7) including receiver optics. First-light observations indicate that the receiver is highly sensitive and functions stably. We present details of the receiver system, its performance at the telescope, and first-light observations with a Herschel mixer.

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 13 CO 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 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.