The Greenland Telescope (GLT) currently achieves a blind pointing accuracy of 2" rms, sufficient for 230GHz VLBI operations at Pituffik Space Base. Plans to relocate the antenna to Summit Station are underway to enable observations at ≥690GHz, which requires improving the pointing accuracy due to smaller beam sizes at higher frequencies. Since achieving the ALMA-standard referenced pointing accuracy of less than 1" for single-dish operations is impractical due to limited sensitivity, GLT’s strategy involves real-time adjustments using data from metrology sensors, following the Systematic Pointing Error Model (SPEM) by the antenna manufacturer (Vertex Antennentechnik). This paper highlights our metrology system’s role in predicting pointing corrections through real-time monitoring of inclinometers, linear, and temperature sensors. Additionally, we introduce a night-viable optical guidescope system for astrometric referencing of star-fields, aiming to enhance pointing precision for high-frequency VLBI with the GLT.
The Atacama Large Millimeter/submillimeter Array (ALMA) Band 1 receiver covers the frequency band between 35-50 GHz. The project achieved the successful delivery of 73 Band 1 receiver units to ALMA telescope site and ready for cycle 10 observation. This paper delves into the implementation of Project management methodologies applied during the both receiver development and production phases. Furthermore, the paper presents the lessons learned and challenges faced, and offer for the future endeavors in applying the project management in the scientific research projects.
The idea of ALMA Band-4+5 receivers are proposed for the upgrade after 2030. The new receiver will cover the RF frequency of the original Band-4 and Band-5 with continuous frequency tuning over 125 –211 GHz with dual polarizations, dual sidebands capability. The instantaneous intermediate frequency (IF) bandwidth is up to 16 GHz per sideband and per polarization. Both the SIS-based receiver and HEMT-based receiver schemes are considered. For the SIS receiver scheme, the niobium-based SIS junctions will be fabricated to form mixer chips, and integrated into the mixer blocks with broadband waveguide 3-dB quadrature hybrid couplers with LO couplers, cryogenic IF low-noise amplifiers, and 2-20 GHz coaxial 3-dB quadrature hybrid couplers to form sideband separating down-converters. The inputs of the sideband separating down-converters are fed by the ellipsoidal mirror pairs, corrugated feedhorn and the orthomode transducer. For the HEMT-based receiver scheme, using the same optics configuration as the SIS-based receiver, the cryogenic InP HEMT low-noise amplifiers (LNAs) chains cover 125 – 211 GHz operated in 15-K ambient temperature will be the key components of the cold cartridge assembly (CCA). For the warm cartridge assembly, a pair of sideband-separating diode or resistive transistor mixers will provide four-channel 16-GHz IF instantaneous bandwidth. To avoid the possible interference between LO and IF signals, considering the possible 16 GHz IF bandwidth over 4 – 20 GHz, the LO fundamental frequency will be chosen in 24 - 32 GHz, followed by an active frequency tripler to form the phase-lock loop with 72 – 96 GHz frequency tuning range. The key components with 51.2% relative bandwidth to be developed in-house are Nb SIS mixers, RF InP HEMT LNAs, 3-dB waveguide hybrid couplers, orthomode transducers, corrugated horn antenna, and optics mirror pairs.
In mid-2025, the initial sub-systems for METIS, the Mid-Infrared E-ELT Imager and Spectrometer, are anticipated to reach the system-level Assembly, Integration, and Testing (AIT) facility at Leiden University. The AIT process is projected to extend over three years. Throughout this period, the comprehensive testing and calibration of the entire METIS system will be conducted. The preparation for integration encompasses diverse aspects, including the planning of various assembly, integration, and verification steps. This involves the development of the integration facility, provision of support equipment, and ensuring the readiness of all requisite software to facilitate the instrument's efficient qualification. As subsystems are nearing completion, also the AIT facility is being finalized, with an expected delivery date of end-July 2024.
The Mid-Infrared E-ELT Imager and Spectrometer (METIS) for the Extremely Large Telescope in Chile, is expecting to begin the system-level Assembly, Integration, and Testing (AIT) at Leiden University in 2025. One of the key success factors for the AIT is the preparation of specialized Support Equipments (SEQs). This paper presents the SEQ units developed by ASIAA, including the AIT support frame (ASF), ASF transportation container, clean area system, and AIT lifting platform. The key requirements, functionality, and considerations for SEQ design are provided.
KEYWORDS: Receivers, Optical amplifiers, Radio astronomy, Antennas, Astronomy, Observatories, Cryogenics, Simulation of CCA and DLA aggregates, Roads, Galactic astronomy
The Atacama large millimeter/submillimeter array (ALMA) band-1 receiver covers the frequency band between 35-50 GHz. An extension of up to 52 GHz is on a best-effort basis. Covering the longest wavelengths visible with ALMA, this receiver is enabling studies of dust grain evolution in proto-planetary systems probing dust grain sizes close to 1 cm, and with multiple red-shifted molecular lines it will open up a new window in the high-redshift universe. The band-1 project has recently achieved first light and with this passed a major project milestone. We present the challenges, from initial development to prototype, to establishing the infrastructure, integration, and evaluation of 73 production receiver units, and to the final tasks to complete the project. We conclude with the initial performance and characterization of the first band-1 receivers installed on ALMA.
Auto-Correlation Spectral Imaging System (ACSIS) is an IF, correlation, reduction, and display system for the submillimeter telescope James Clerk Maxwell Telescope (JCMT). It can produce calibrated spectral images in real time and enables rapid imaging of large areas of the sky over a wide spectral range or at high resolution from up to 16 receiver feeds. Now more than 20 years old, the original 8-10GHz synthesizers for the down conversion module are obsolete and no longer available. Due to the hardware changes in the new 4-10GHz model, an interface circuit is needed to shorten the rise time of the serial clock signal. Further upgrades can better support wide IF band 2-12GHz receiver applications, such as Atacama Large Millimeter Array (ALMA) band-6 receivers. This paper discusses the observatory’s development of a new correlator that utilizes several existing electronics to support current and future receivers.
The Ka-/Q-band in the microwave region of the electromagnetic spectrum is important for astrophysical and astrochemical research, particularly in the subfield of interstellar medium (ISM). The two bands cover not only the fundamental lines of the abundant dense gas tracer CS and its isotopologues but also a vast number of transitions of relatively large, long-chain, and/or complex organic species. Here, through a Taiwan-Japan collaboration, an extended Q-band (30-50GHz) receiver is built for Nobeyama 45-m telescope. The receiver front-end was installed at Nobeyama 45-m telescope in Nov. 2021 and obtained its first light in the same month. Commissioning and science verification (CSV) of the receiver was conducted in the first half of 2022. After commissioning, this receiver will be the only one in the world providing capability to cover 3 Zeeman transitions simultaneously at 7mm wavelength installed at large single dish telescope. It will be one of the most powerful facilities to explore the magnetic fields towards the pre-protostellar cores.
METIS, the Mid-infrared E-ELT Imager and Spectrometer, is being designed for the Extremely Large Telescope (ELT) and is currently expected to arrive at the telescope early 2028. As part of the design of the instrument, we are developing the Assembly, Integration and Verification strategy for METIS. Although the sub-systems will be largely qualified at their respective institutes, only once all components come together at system level will it be possible to verify all the interfaces, full system thermal characteristics and full instrument performance. Although one of the smaller instruments for the ELT, the fully integrated METIS will still be more than 7 meters high, with a footprint in excess of 15 square meters and a weight of the order of 10 tons. This paper describes the system level assembly, integration and verification of METIS, both in Europe as well as once delivered to the telescope.
Namakanui is an instrument containing three inserts in an ALMA type Dewar. The three inserts are ‘Ala’ihi, ‘U’ū and ‘Āweoweo operating around 86, 230 and 345GHz. The receiver is being commissioned on the JCMT. It will be used for both Single dish and VLBI observations. We will present commissioning results and the system.
The Greenland Telescope (GLT), currently located at Thule Air Base, is a 12-m single dish telescope operating at frequencies of 86, 230 and 345 GHz. Since April 2018, the GLT has regularly participated in (sub-)mm VLBI observations of supermassive black holes as part of the Event Horizon Telescope (EHT) and the Global mm VLBI Array (GMVA). We present the status of scientific commissioning activities at the GLT, including most recently the 345 GHz first light and test observations. The antenna surface accuracy has been improved to ~25 microns through panel adjustments aided by photogrammetry, significantly increasing the antenna efficiency. Through all-sky spectral line pointing observations (SiO masers at 86 GHz and CO at 230 and 345 GHz), we have improved the radio pointing accuracy down to <~ 3" at all 3 frequencies. Due to the pandemic, we are in the process of transitioning GLT commissioning and observing activities to remote operations.
We describe the latest development of the control and monitoring system of the Greenland Telescope (GLT). The GLT is a 12-m radio telescope aiming to carry out the sub-millimeter Very Long Baseline Interferometry (VLBI) observations through the Event Horizon Telescope (EHT) and the Global Millimeter VLBI Array (GMVA), to image the shadows of super massive black holes. The telescope is currently located at the Thule Air Base for commissioning before deployed to the Summit Station. The GLT participated in the VLBI observing campaigns in 2018 and 2019 and fringes were successfully detected at 86 and 230 GHz. Our antenna control software was adapted from the Submillimeter Array (SMA), and as a result for single-dish observations we added new routines to coordinate it with other instruments. We are exploring new communication interfaces; we utilized both in-memory and on-disk databases to be part of the interfaces not only for hardware monitoring but also for engineering event logging. We plan to incorporate the system of the James Clerk Maxwell Telescope for the full Linux-based receiver control. The current progress of integrating our receivers, spectrometers, sub-reflector, and continuum detector into control is presented, together with the implementation of the commissioning software for spectral line pointing. We also describe how we built the anti-collision protection and the recovery mechanism for the sub-reflector hexapod.
A three-cartridge cryogenic receiver system is constructed for the Greenland Telescope Project. The system is equipped with a set of sub-millimeter receivers operating at 86, 230, and 345 GHz, as well as a complete set of instruments for calibration, control and monitoring. It is single pixel instrument built for VLBI observations. With the receiver system, the GLT has completed commissioning of its 12-m sub-millimeter antenna and participated in global very-long-baseline interferometry (VLBI) observations at Thule Air Base (TAB). This paper describes the receiver specification, construction, and verification.
The Atacama Large Millimeter/submillimeter Array (ALMA) Band 1 receiver covers the frequency range of 35-50 GHz. An extension of up to 52 GHz is on a best-effort basis. A total of 73 units have to be built in two phases: 8 preproduction and then 65 production units. This paper reports on the assembly, testing, and performance of the preproduction Band 1 receiver. The infrastructure, integration, and evaluation of the fully-assembled Band 1 receiver system will be covered. Finally, a discussion of the technical and managerial challenges encountered for this large number of receivers will be presented.
The Greenland Telescope project has recently participated in an experiment to image the supermassive black hole shadow at the center of M87 using Very Long Baseline Interferometry technique in April of 2018. The antenna consists of the 12-m ALMA North American prototype antenna that was modified to support two auxiliary side containers and to withstand an extremely cold environment. The telescope is currently at Thule Air Base in Greenland with the long-term goal to move the telescope over the Greenland ice sheet to Summit Station. The GLT currently has a single cryostat which houses three dual polarization receivers that cover 84-96 GHz, 213-243 GHz and 271-377 GHz bands. A hydrogen maser frequency source in conjunction with high frequency synthesizers are used to generate the local oscillator references for the receivers. The intermediate frequency outputs of each receiver cover 4-8 GHz and are heterodyned to baseband for digitization within a set of ROACH-2 units then formatted for recording onto Mark-6 data recorders. A separate set of ROACH-2 units operating in parallel provides the function of auto-correlation for real-time spectral analysis. Due to the stringent instrumental stability requirements for interferometry a diagnostic test system was incorporated into the design. Tying all of the above equipment together is the fiber optic system designed to operate in a low temperature environment and scalable to accommodate a larger distance between the control module and telescope for Summit Station. A report on the progress of the above electronics instrumentation system will be provided.
The Greenland Telescope completed its construction, so the commissioning phase has been started since December 2017. Single-dish commissioning has started from the optical pointing which produced the first pointing model, followed by the radio pointing and focusing using the Moon for both the 86 GHz and the 230 GHz receivers. After Venus started to rise from the horizon, the focus positions has been improved for both receivers. Once we started the line pointing using the SiO(2-1) maser line and the CO(2-1) line for the 86 GHz and the 230 GHz receivers, respectively, the pointing accuracy also improved, and the final pointing accuracy turned to be around 3" - 5" for both receivers. In parallel, VLBI commissioning has been performed, with checking the frequency accuracy and the phase stability for all the components that would be used for the VLBI observations. After all the checks, we successfully joined the dress rehearsals and actual observations of the 86 GHz and 230 GHz VLBI observations, The first dress rehearsal data between GLT and ALMA were correlated, and successfully detected the first fringe, which confirmed that the GLT commissioning was successfully performed.
The Greenland Telescope Project (GLT) has successfully commissioned its 12-m sub-millimeter. In January 2018, the fringes were detected between the GLT and the Atacama Large Millimeter Array (ALMA) during a very-long-baseline interferometry (VLBI) exercise. In April 2018, the telescope participated in global VLBI science observations at Thule Air Base (TAB). The telescope has been completely rebuilt, with many new components, from the ALMA NA (North America) Prototype antenna and equipped with a new set of sub-millimeter receivers operating at 86, 230, and 345 GHz, as well as a complete set of instruments and VLBI backends. This paper describes our progress and status of the project and its plan for the coming decade.
We describe the control and monitoring system for the Greenland Telescope (GLT). The GLT is a 12-m radio telescope aiming to carry out the sub-millimeter Very Long Baseline Interferometry (VLBI) observations and image the shadow of the super massive black hole in M87. In November 2017 construction has been finished and commissioning activity has been started. In April 2018 we participated in the VLBI observing campaign for the Event Horizon Telescope (EHT) collaboration. In this paper we present the entire GLT control/monitoring system in terms of computers, network and software.
The Atacama Large Millimeter/submillimeter Array(ALMA) Band 1 receiver covers the 35-50 GHz frequency band. Development of prototype receivers, including the key components and subsystems has been completed and two sets of prototype receivers were fully tested. We will provide an overview of the ALMA Band 1 science goals, and its requirements and design for use on the ALMA. The receiver development status will also be discussed and the infrastructure, integration, evaluation of fully-assembled band 1 receiver system will be covered. Finally, a discussion of the technical and management challenges encountered will be presented.
Since the ALMA North America Prototype Antenna was awarded to the Smithsonian Astrophysical Observatory (SAO), SAO and the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) are working jointly to relocate the antenna to Greenland. This paper shows the status of the antenna retrofit and the work carried out after the recommissioning and subsequent disassembly of the antenna at the VLA has taken place. The next coming months will see the start of the antenna reassembly at Thule Air Base. These activities are expected to last until the fall of 2017 when commissioning should take place. In parallel, design, fabrication and testing of the last components are taking place in Taiwan.
The ALMA Band-1 receiver front-end prototype cold and warm cartridge assemblies, including the system and key
components for ALMA Band-1 receivers have been developed and two sets of prototype cartridge were fully tested. The
measured aperture efficiency for the cold receiver is above the 80% specification except for a few frequency points.
Based on the cryogenically cooled broadband low-noise amplifiers provided by NRAO, the receiver noise temperature
can be as low as 15 – 32K for pol-0 and 17 – 30K for pol-1. Other key testing items are also measured. The receiver
beam pattern is measured, the results is well fit to the simulation and design. The pointing error extracted from the
measured beam pattern indicates the error is 0.1 degree along azimuth and 0.15 degree along elevation, which is well fit
to the specification (smaller than 0.4 degree). The equivalent hot load temperature for 5% gain compression is 492 -
4583K, which well fit to the specification of 5% with 373K input thermal load. The image band suppression is higher
than 30 dB typically and the worst case is higher than 20 dB for 34GHz RF signal and 38GHz LO signal, which is all
higher than 7 dB required specification. The cross talk between orthogonal polarization is smaller than -85 dB based on
present prototype LO. The amplitude stability is below 2.0 x 10-7 , which is fit to the specification of 4.0 x 10-7 for
timescales in the range of 0.05 s ≤ T ≤ 100 s. The signal path phase stability measured is smaller than 5 fs, which is
smaller than 22 fs for Long term (delay drift) 20 s ≤ T < 300 sec. The IF output phase variation is smaller than 3.5° rms
typically, and the specification is less than 4.5° rms. The measured IF output power level is -28 to -30.5 dBm with 300K
input load. The measured IF output power flatness is less than 5.6 dB for 2GHz window, and 1.3dB for 31MHz window.
The first batch of prototype cartridges will be installed on site for further commissioning on July of 2017.
ALMA covering 35-950 GHz is the largest existing telescope array in the world. Among the 10 receiver bands, Band-1,
which covers 35-50 GHz, is the lowest. Due to its small dimension and its time-variant frequency-dependent gain
characteristics, current solar filter located above the cryostat cannot be applied to Band-1 for solar observation. Here we
thus adopt new strategies to fulfill the goals. Thanks to the flexible dc biasing scheme of the HEMT-based amplifier in
Band-1 front-end, bias adjustment of the cryogenic low noise amplifier is investigated to accomplish solar observation
without using solar filter. Large power handling range can be achieved by the de-tuning bias technique with little
degradation in system performance.
KEYWORDS: Receivers, Oscillators, Waveguides, Prototyping, Amplifiers, Optical amplifiers, Antennas, Optical isolators, Field effect transistors, Simulation of CCA and DLA aggregates
The prototype cartridges for ALMA Band-1 receivers have been developed, based on the key components developed in ALMA Band-1 consortium laboratories. The prototype cartridges for each receiver consist of two parts, cold cartridge assembly and warm cartridge assembly. The cold cartridge assembly (CCA) consists of horn antenna, orthomode transducer and a pair of 35-52 GHz cold low-noise amplifiers, the amplified signals of both polarizations are transmitted to warm cartridge assembly by long waveguide sections. In warm cartridge assembly (WCA), two major modules incorporated, down-converter assembly including warm low-noise amplifier, high-pass filter, mixer and 4-12 GHz IF amplifier, and local oscillator based on a 31-40 GHz YIG-tunes oscillator. The frequency range is based on the upper sideband scheme. Based on the measured performance of the key components, the expected noise performance of the receiver will be 26-33K.
The Greenland Telescope project will deploy and operate a 12m sub-millimeter telescope at the highest point of the Greenland i e sheet. The Greenland Telescope project is a joint venture between the Smithsonian As- trophysical Observatory (SAO) and the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA). In this paper we discuss the concepts, specifications, and science goals of the instruments being developed for single-dish observations with the Greenland Telescope, and the coupling optics required to couple both them and the mm-VLBI receivers to antenna. The project will outfit the ALMA North America prototype antenna for Arctic operations and deploy it to Summit Station,1 a NSF operated Arctic station at 3,100m above MSL on the Greenland I e Sheet. This site is exceptionally dry, and promises to be an excellent site for sub-millimeter astronomical observations. The main science goal of the Greenland Telescope is to carry out millimeter VLBI observations alongside other telescopes in Europe and the Americas, with the aim of resolving the event horizon of the super-massive black hole at the enter of M87. The Greenland Telescope will also be outfitted for single-dish observations from the millimeter-wave to Tera-hertz bands. In this paper we will discuss the proposed instruments that are currently in development for the Greenland Telescope - 350 GHz and 650 GHz heterodyne array receivers; 1.4 THz HEB array receivers and a W-band bolometric spectrometer. SAO is leading the development of two heterodyne array instruments for the Greenland Telescope, a 48- pixel, 325-375 GHz SIS array receiver, and a 4 pixel, 1.4 THz HEB array receiver. A key science goal for these instruments is the mapping of ortho and para H2D+ in old protostellar ores, as well as general mapping of CO and other transitions in molecular louds. An 8-pixel prototype module for the 350 GHz array is currently being built for laboratory and operational testing on the Greenland Telescope. Arizona State University are developing a 650 GHz 256 pixel SIS array receiver based on the KAPPa SIS mixer array technology and ASIAA are developing 1.4 THz HEB single pixel and array receivers. The University of Cambridge and SAO are collaborating on the development of the CAMbridge Emission Line Surveyor (CAMELS), a W-band `on- hip' spectrometer instrument with a spectral resolution of R ~ 3000. CAMELS will consist of two pairs of horn antennas, feeding super conducting niobium nitride filter banks read by tantalum based Kinetic Inductance Detectors.
The ALMA North America Prototype Antenna was awarded to the Smithsonian Astrophysical Observatory (SAO) in 2011. SAO and the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), SAO’s main partner for this project, are working jointly to relocate the antenna to Greenland to carry out millimeter and submillimeter VLBI observations. This paper presents the work carried out on upgrading the antenna to enable operation in the Arctic climate by the GLT Team to make this challenging project possible, with an emphasis on the unexpected telescope components that had to be either redesigned or changed. Five-years of inactivity, with the antenna laying idle in the desert of New Mexico, coupled with the extreme weather conditions of the selected site in Greenland have it necessary to significantly refurbish the antenna. We found that many components did need to be replaced, such as the antenna support cone, the azimuth bearing, the carbon fiber quadrupod, the hexapod, the HVAC, the tiltmeters, the antenna electronic enclosures housing servo and other drive components, and the cables. We selected Vertex, the original antenna manufacturer, for the main design work, which is in progress. The next coming months will see the major antenna components and subsystems shipped to a site of the US East Coast for test-fitting the major antenna components, which have been retrofitted. The following step will be to ship the components to Greenland to carry out VLBI
We report the first measurements of 225 GHz atmospheric opacity at Summit Camp (Latitude 72°.57 N; Longitude
38°.46 W; Altitude 3250 m) in Greenland and the Polar Environment Atmospheric Research Laboratory
(PEARL: Latitude 80°.05 N; Longitude 86°.42 W; Altitude 600 m) in Northern Canada with a tipping radiometer.
Summit Camp and PEARL are research stations mostly interested in meteorology and geophysics, and
they are potentially excellent sites for astronomical observations at sub-millimeter wavelength. We purchased
a tipping radiometer from Radiometer Physics GmbH. After a test run at the summit of Mauna Kea, Hawaii,
the radiometer was deployed to PEARL in February 2011, and relocated to Summit Camp in August 2011. The
atmospheric opacity has been monitored from February 14th to May 10th, 2011 at PEARL and since August
2011 at Summit Camp. The median values of the measured opacity at PEARL ranged from 0.11 in February to 0.19 in May; Summit Camp varied in the range from 0.04 to 0.18 between August 2011 and May 2012. Summit
Camp in Greenland is expected to be an excellent site for sub-millimeter and Terahertz astronomy, and we plan
to set up there a 12-m telescope for VLBI and single-dish observations.
The Array for Microwave Background Anisotropy (AMiBA) is a radio interferometer for research in cosmology,
currently operating 7 0.6m diameter antennas co-mounted on a 6m diameter platform driven by a hexapod
mount. AMiBA is currently the largest hexapod telescope. We briefly summarize the hexapod operation with
the current pointing error model. We then focus on the upcoming
13-element expansion with its potential
difficulties and solutions. Photogrammetry measurements of the platform reveal deformations at a level which
can affect the optical pointing and the receiver radio phase. In order to prepare for the 13-element upgrade, two
optical telescopes are installed on the platform to correlate optical pointing tests. Being mounted on different
locations, the residuals of the two sets of pointing errors show a characteristic phase and amplitude difference
as a function of the platform deformation pattern. These results depend on the telescope's azimuth, elevation
and polarization position. An analytical model for the deformation is derived in order to separate the local
deformation induced error from the real hexapod pointing error. Similarly, we demonstrate that the deformation
induced radio phase error can be reliably modeled and calibrated, which allows us to recover the ideal synthesized
beam in amplitude and shape of up to 90% or more. The resulting array efficiency and its limits are discussed
based on the derived errors.
The next generation wide field camera HSC (Hyper Suprime-Cam) on Subaru telescope is planned to
cover 1.5 degree diameter field with a focal plane size about 650mm. To minimize the impact to the telescope,
the design for the elements of the camera is constraint to the tight space and weight limits. In order to fit the
available space, the screen winding shutter and petal shape filter exchanger are designed for the HSC. The
CFRP is used for the structure to minimize the load. In this report, the design and analysis for the shutter and
filter exchanger system will be presented. The result for the shutter membrane tests will also be discussed.
This paper describes the photogrammetry method as a mean to measure the deformation of the 6-meter carbon fiber reinforced
plastic (CFRP) Platform of the AMiBA interferometric array telescope installed at the Mauna Loa Observatory, Hawaii. The
Platform was surveyed at a series of elevation, azimuth and polarization angles. Photogrammetry demonstrates that the
deformation of the Platform is not only gravity-induced but also due to the Hexapod mount actuator. The measurement results
verify the predictions of the Finite Element Analysis (FEA).
Using the array of seven 0.6m antennas in Hawaii, we have conducted short observations on several galaxy clusters through
the Sunyaev-Zeldovich effect at 3mm wavelength in 2007. The observations were done with a resolution of 6', and we
have chosen the low redshift (z=0.09-0.32) massive clusters to optimize detection. Major contamination to the data comes
from instrumental offset and ground pickup. We will demonstrate the results based on a simple on source - off source
switching observing scheme. In addition, the performance of a wideband analog 4-lag correlator was also investigated.
The Academia Sinica, Institute for Astronomy and Astrophysics (ASIAA) is installing the AMiBA interferometric array telescope at the Mauna Loa Observatory, Hawaii. The 6-meter carbon fiber fully steerable platform is mounted on the Hexapod Mount. After integration and equipment with dummy weights, the platform has been measured by photogrammetry to verify its behavior predicted by Finite Element Analysis. The Hexapod servo control is now operational and equipment of the platform with the initial 7 60-cm dishes, the correlator and electronics is underway. Pointing has started with the aid of the optical telescope. We present the status of the telescope after the servo and initial pointing tests have been carried out. We also present the results of platform measurements by photogrammetry.
AMiBA, as a dual-polarization 86-102 GHz interferometer array, is designed to measure the power spectrum of fluctuations in the cosmic microwave background (CMB) radiation, and to detect the high-redshift clusters of galaxies via the Sunyaev-Zel'dovich Effect (SZE). The operation of AMiBA is about to begin after installation of the first two receivers and correlators onto the 6-meter diameter platform by the end of 2005. The initial setup of the array will consist of 7 antennas with 60 cm diameter reflectors in a hexagonal configuration, aiming at multipoles l ~ 3000. Signals from receivers are cross-correlated in analog lag correlators. The initial operation will focus on characterizing the systematics by observing various known objects on the sky. The expansion to 13 elements with larger dishes will commence once the 7-element array testing is completed.
This is to report on our development for a dual-polarization receiver to detect the cosmic microwave background (CMB) in 85 to 105 GHz band. The receiver is based on a MMIC, HEMT-based LNA developed in the Jet Propulsion Laboratory. A W-band, orthomode transducer (OMT) is used for polarization separation. Most of the RF front-end is located in cryogenics environment at 20K. We have developed a MMIC sub-harmonically pumped diode mixer, operating at 42 GHz, for signal down-conversion. The entire base-band, 2 to 18 GHz, is correlated in a lag-correlator system. The receiver design details and the lab test results will be described in this report.
AMiBA consists of a 90 GHz interferometric array telescope with dishes ranging in size from 0.3 to 2.4 meter in diameter, mounted on a 6-meter fully steerable platform. The dishes are attached to the receivers, which are mounted on a platform controlled by a six degree of freedom hexapod mount. The hexapod mount is a parallel connection manipulator also called Stewart Platform. The basic reference for this mechanism is a paper by Stewart. The Stewart Platform is a unique kinematically constrained work platform. It can be manipulated through the six degrees of freedom. The hexapod also provides better accuracy, rigidity, load to weight ratio and load distribution than a serial manipulator or traditional manipulator. The advantages of the hexapod shows that it is a great choice for the AMiBA project. Vertex Antennentechnik GmbH fabricates the hexapod. Testing has started in Germany. The telescope will be delivered in the summer of 2004. The 6m in diameter hexagonal platform is made of carbon fiber reinforced plastics (CFRP) and consists of seven pieces of three different unique types. The platform can be disassembled and fits in a container for transportation. The mounting plane flatness is an important issue for the platform assembly. The deflection angle of the mounting plane relative to any other mounting position must be less than 20 arcsec. Meanwhile, the platform must endure a loading of 3 tons. The platform has been built by Composite Mirror Applications, Inc. (CMA) in Tucson, and mounted on the Hexapod in Germany. This report describes the design and testing of platform and mount for the AMiBA telescope.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.