A single feed cryogenic Q-band (35 – 50 GHz) dual-linear polarization receiver is under development at the NRC, primarily to establish the antenna performance parameters of the Dish Verification Antenna 2 at its high-frequency limit and as a possible receiver system for the National Radio Astronomy Observatory’s Next Generation Very Large Array (ngVLA). The cryostat houses a corrugated feed horn cooled to 16 K with a wide opening half-angle of 55°. The linear orthomode transducer (OMT) was redesigned to incorporate noise injection couplers and the power dividing function thus reducing the amount of components, connections, and thermal mass. The low noise (TLNA = 12 K) amplifier (LNA) was also redesigned to replace coaxial ports with WR-22 waveguide ports. The specifications, receiver design, measured farfield feed horn beam patterns from a near-field planar scanner, simulated OMT results, and sub-20 K receiver noise analysis is presented, along with future plans for production and installation.
DVA1 (Dish Verification Antenna 1) is a highly innovative rim-supported single-piece composite-material dish radio telescope developed at the National Research Council Canada (NRC). It has a feed-high offset Gregorian optical design with a primary effective diameter of 15 m. DVA1 has been undergoing mechanical and astronomical system tests since 2014. Astronomical measurements were made in L band using a prototype front end developed for MeerKAT by EMSS Antennas (South Africa), including aperture efficiency, beam profiles, sensitivity, and tipping curves. The clean shaped optics, careful attention to feed design, and high sensitivity of the L band receiver (Trx ~ 6 K) yield a system with high aperture efficiency (~ 0.8), excellent sensitivity (~ 9 m2/K), and low spillover (~ 4 K). Observations of 21 cm atomic hydrogen lines towards standard sources demonstrate the low stray radiation pickup of the antenna. Ku band holography has measured the effective surface accuracy and stability of the dual-reflector antenna. The effective RMS of ~ 0.85 mm implies a Ruze efficiency of ~ 0.88 at 10 GHz and ~ 0.60 at 20 GHz. The surface is stable (~ 10% variation in surface RMS) over the limited range of environmental conditions tested. Testing continues for characterization of pointing, low frequency performance (< 1 GHz), and polarimetric performance. NRC is developing a successor antenna, DVA3, which will have a more accurate surface and be usable at frequencies at least up to Q band (30 – 50 GHz).
Phased array feed (PAF) receivers used on radio astronomy telescopes offer the promise of increased fields of view
while maintaining the superlative performance attained with traditional single pixel feeds (SPFs). However, the much
higher noise temperatures of room temperature PAFs compared to cryogenically-cooled SPFs have prevented their
general adoption. Here we describe a conceptual design for a cryogenically cooled 2.8 – 5.18 GHz dual linear
polarization PAF with estimated receiver temperature of 11 K. The cryogenic PAF receiver will comprise a 140 element
Vivaldi antenna array and low-noise amplifiers housed in a 480 mm diameter cylindrical dewar covered with a RF
transparent radome. A broadband two-section coaxial feed is integrated within each metal antenna element to withstand
the cryogenic environment and to provide a 50 ohm impedance for connection to the rest of the receiver. The planned
digital beamformer performs digitization, frequency band selection, beam forming and array covariance matrix
calibration. Coupling to a 15 m offset Gregorian dual-reflector telescope, cryoPAF4 can expect to form 18 overlapping
beams increasing the field of view by a factor of ~8x compared to a single pixel receiver of equal system temperature.
The Atacama Large Millimeter/submillimeter Array (ALMA) Band 10 receiver covering 787 to 950 GHz is the highest frequency receiver of the ten bands envisioned for the ALMA Front End system. The Band 10 receivers have been undergoing installation and commissioning since 2012. After the Band 10 receiver tuning scripts (Josephson currents suppression, LO power optimization) and operation procedures had been developed and implemented, astronomical verification procedures (radio pointing, focus, beam squint, and end-to-end spectroscopic verification) were established in single dish mode at the ALMA Operations Support Facility (OSF; 2900 m elevation). Subsequently, the first Band 10 astronomical fringes were achieved at the Array Operations Site in October 2013 (AOS; 5000 m elevation). This is the highest frequency ever achieved by a radio interferometer and opens up a new window into submillimeter astrophysics.
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 (<30000K USD) and a low setup time of less than 1 hour. The Test Interferometer could include up to 16 Antennas when used with only AOS resources and a possible maximum of 4 Antennas when configured using Correlator resources at OSF. A joined effort between ADC and ADE-IG took the challenge of generate the Test Interferometer from an already defined design for operations which imposed a lot of complex restrictions on how to implement it. Through and intensive design and evaluation work it was determined that is possible to make an initial implementation using the ACA Correlator and now it is also being tested the feasibility to implement the Testing Interferometer connecting the Test Array at AOS with Correlator equipment installed at the OSF, separated by 30 km. app. Lastly, efforts will be done to get interferometry between AOS and OSF Antennas with a baseline of approximately 24 km.
The Atacama Large Millimeter/submillimeter Array (ALMA) is a joint project between astronomical organizations in
Europe, North America, and East Asia, in collaboration with the Republic of Chile. ALMA will consist of at least 54
twelve-meter antennas and 12 seven-meter antennas operating as an aperture synthesis array in the (sub)millimeter
wavelength range. It is the responsibility of ALMA AIV to deliver the fully assembled, integrated, and verified antennas
(array elements) to the telescope array.
After an initial phase of infrastructure setup AIV activities began when the first ALMA antenna and subsystems became
available in mid 2008. During the second semester of 2009 a project-wide effort was made to put in operation a first 3-
antenna interferometer at the Array Operations Site (AOS). In 2010 the AIV focus was the transition from event-driven
activities towards routine series production. Also, due to the ramp-up of operations activities, AIV underwent an
organizational change from an autonomous department into a project within a strong matrix management structure.
When the subsystem deliveries stabilized in early 2011, steady-state series processing could be achieved in an efficient
and reliable manner. The challenge today is to maintain this production pace until completion towards the end of 2013.
This paper describes the way ALMA AIV evolved successfully from the initial phase to the present steady-state of array
element series processing. It elaborates on the different project phases and their relationships, presents processing
statistics, illustrates the lessons learned and relevant best practices, and concludes with an outlook of the path towards
The Atacama Large Millimeter/submillimeter Array (ALMA) will consist of at least 54 twelve-meter antennas and 12
seven-meter antennas operating as an aperture synthesis array in the (sub)millimeter wavelength range. The ALMA
System Integration Science Team (SIST) is a group of scientists and data analysts whose primary task is to verify and
characterize the astronomical performance of array elements as single dish and interferometric systems. The full set of
tasks is required for the initial construction phase verification of every array element, and these can be divided roughly
into fundamental antenna performance tests (verification of antenna surface accuracy, basic tracking, switching, and on-the-fly rastering) and astronomical radio verification tasks (radio pointing, focus, basic interferometry, and end-to-end
spectroscopic verification). These activities occur both at the Operations Support Facility (just below 3000 m elevation)
and at the Array Operations Site at 5000 m.