Dr. Masao Saito Profile

Dr. Masao Saito

at National Astronomical Observatory of Japan

SPIE Involvement:

Conference Program Committee | Author

Publications (13)

PROCEEDINGS ARTICLE | July 27, 2016

Large aperture millimeter/submillimeter telescope: which is more cost-effective, aperture synthesis telescope versus large single dish telescope?

Proc. SPIE. 9906, Ground-based and Airborne Telescopes VI

KEYWORDS: Telescopes, Spectroscopy, Receivers, Synthetic apertures, Antennas, Analog electronics, Optical instrument design, Optical correlators, Cryogenics, Chemical mechanical planarization

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PROCEEDINGS ARTICLE | July 19, 2016

Development of the new multi-beam 100 GHz band SIS receiver FOREST for the Nobeyama 45-m Telescope

Proc. SPIE. 9914, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VIII

KEYWORDS: Observatories, Telescopes, Mirrors, Astronomy, Polarization, Receivers, Space telescopes, Signal processing, Astronomical telescopes, Galactic astronomy

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PROCEEDINGS ARTICLE | August 6, 2014

ALMA observations during its first early science cycles

Proc. SPIE. 9149, Observatory Operations: Strategies, Processes, and Systems V

KEYWORDS: Observatories, Astronomy, Data modeling, Calibration, Receivers, Data archive systems, Data processing, Software development, Antennas, Antimony

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PROCEEDINGS ARTICLE | July 22, 2014

A holography receiver for the Atacama Large millimeter/submillimeter array antenna and the measured surface deformation

Proc. SPIE. 9145, Ground-based and Airborne Telescopes V

KEYWORDS: Astronomy, Holography, Sun, Interferometers, Receivers, Aluminum, Antennas, Phase measurement, Analog electronics, Temperature metrology

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PROCEEDINGS ARTICLE | July 22, 2014

Development of high-accuracy pointing verification for ALMA antenna

Proc. SPIE. 9145, Ground-based and Airborne Telescopes V

KEYWORDS: Astronomy, Stars, Radio optics, Error analysis, Reliability, Ocean optics, Integrated optics, Antennas, Velocity measurements, Wind measurement

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Pointing performance of a radio telescope antenna is important in radio astronomical observations to obtain accurate intensity of a target source. The pointing errors of the ALMA ACA antenna are required to be better than 0.6 arcsec rss, which corresponds to 1/10 and 1/20 of the field of view of the ALMA ACA 12-m and 7-m antenna at 950 GHz, respectively. The pointing verification measurements of the ACA antenna were performed using an Optical pointing telescope (OPT) mounted on the antenna backup structure at the ALMA Operations Site Facility at 2900m above the sea level. Pointing errors of these OPT measurements contain three different origins; originated from antenna, originated of atmosphere (optical seeing), and originated of OPT itself. In order to estimate pointing errors of the antenna origin, we need to subtract the components of optical seeing and OPT itself accurately, while we need to add components that cannot be measured in the OPT measurements. The ACA antenna verification test report demonstrated that all the ACA 7-m antenna meets pointing specification of ALMA. However, about one-third of datasets, values of estimated optical seeing is larger than measured pointing errors. We re-examined a procedure to estimate optical seeing, by investigating the property of optical seeing from the high-sampling OPT pointing measurements of long tracking a bright star for 15 minutes. Particularly, we examined the relation between optical seeing and sampling rate derived from Kolmogorov PSD. Our analysis indicated that the optical seeing at ALMA site may have been overestimated in the verification test. We present a new relation between optical seeing and sampling rate proportional to average wind velocity during measurement. We used this new relation to derive the optical seeing and as a result the number of datasets becomes half in which the optical seeing is larger than measured pointing errors. As a result, we successfully develop a new verification method of optical seeing that has high reliability.

PROCEEDINGS ARTICLE | September 27, 2012

Photonic local oscillator technics for large-scale interferometers

Proc. SPIE. 8444, Ground-based and Airborne Telescopes IV

KEYWORDS: Oscillators, Polarization, Fiber Bragg gratings, Sensors, Digital filtering, Phase shift keying, Signal processing, Signal generators, Phase measurement, Signal detection

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PROCEEDINGS ARTICLE | September 17, 2012

Atacama compact array antennas

Proc. SPIE. 8444, Ground-based and Airborne Telescopes IV

KEYWORDS: Reflectors, Telescopes, Holography, Metrology, Stars, Error analysis, Electroluminescence, Antennas, Fast packet switching, Received signal strength

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PROCEEDINGS ARTICLE | September 17, 2012

Very large millimeter/submillimeter array toward search for 2nd Earth

Proc. SPIE. 8444, Ground-based and Airborne Telescopes IV

KEYWORDS: Telescopes, Astronomy, Stars, Receivers, Radio telescopes, Antennas, Spatial resolution, Planets, Optical instrument design, Atmospheric modeling

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PROCEEDINGS ARTICLE | July 28, 2010

Wind-induced pointing errors and surface deformation of a 10-m submillimeter antenna

Proc. SPIE. 7733, Ground-based and Airborne Telescopes III

KEYWORDS: Reflectors, Telescopes, Sensors, Computer programming, Turbulence, Antennas, Servomechanisms, Reflector telescopes, Motion measurement, Wind measurement

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PROCEEDINGS ARTICLE | June 27, 2006

Elevation angle dependence of the SMA antenna focus position

Proc. SPIE. 6275, Millimeter and Submillimeter Detectors and Instrumentation for Astronomy III

KEYWORDS: Reflectors, Telescopes, Astronomy, Oscillators, Radio optics, Antennas, Planets, Jupiter, Shape memory alloys, Temperature metrology

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PROCEEDINGS ARTICLE | June 23, 2006

Vortex shedding from a 12-m antenna

Proc. SPIE. 6267, Ground-based and Airborne Telescopes

KEYWORDS: Reflectors, Telescopes, Computer programming, Ultrasonics, Turbulence, Antennas, Velocity measurements, Motion measurement, Wind measurement, Prototyping

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PROCEEDINGS ARTICLE | September 29, 2004

Holographic surface setting of the Sub-millimeter Array antennas

Proc. SPIE. 5495, Astronomical Structures and Mechanisms Technology

KEYWORDS: Telescopes, Astronomy, Holography, Receivers, Optical testing, Near field, Antennas, Spatial resolution, Efficient operations, Shape memory alloys

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PROCEEDINGS ARTICLE | September 28, 2004

Design and performance of the ALMA-J prototype antenna

Proc. SPIE. 5489, Ground-based Telescopes

KEYWORDS: Observatories, Reflectors, Telescopes, Holography, Metrology, Stars, Computer programming, Antennas, Servomechanisms, Prototyping

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The National Astronomical Observatory of Japan has constructed a prototype 12-m antenna of the Atacama Compact Array to evaluate its performance at the ALMA Test Facility in the NRAO VLA observatory in New Mexico, the United States. The antenna has a CFRP tube backup structure (BUS) with CFRP boards to support 205 machined Aluminum surface panels. Their accuracies were measured to be 5.9 m rms on average. A chemical treatment technique of the surface panels has successfully applied to scatter the solar radiation, which resulted in a subreflector temperature increase of about 25 degrees relative to ambient temperature during direct solar observations. Holography measurements and panel adjustments led to a final surface accuracy of 20 m rms, (weighted by 12dB edge taper), after three rounds of the panel adjustments. Based on a long term temperature monitoring of the BUS and thermal deformation FEM calculation, the BUS thermal deformation was estimated to be less than 3.1 m rms. We have employed gear drive mechanism both for a fast position switching capability and for smooth drive at low velocities. Servo errors measured with angle encoders were found to be less than 0.1 arcseconds rms at rotational velocities below 0.1 degrees s-1 and to increase to 0.7 arcseconds rms at the maximum speed of the 'on-the-fly' scan as a single dish, 0.5 deg s-1 induced by the irregularity of individual gear tooth profiles. Simultaneous measurements of the antenna motion with the angle encoders and seismic accelerometers mounted at the primary reflector mirror edges and at the subreflector showed the same amplitude and phase of oscillation, indicating that they are rigid, suggesting that it is possible to estimate where the antenna is actually pointing from the encoder readout. Continuous tracking measurements of Polaris during day and night have revealed a large pointing drift due to thermal distortion of the yoke structure. We have applied retrospective thermal corrections to tracking data for two hours, with a preliminary thermal deformation model of the yoke, and have found the tracking accuracy improved to be 0.1 - 0.3 arcseconds rms for a 15-munites period. The whole sky absolute pointing error under no wind and during night was measured to be 1.17 arcseconds rms. We need to make both an elaborated modeling of thermal deformation of the structure and systematic searches for significant correlation among pointing errors and metrology sensor outputs to achieve the stable tracking performance requested by ALMA.

Showing 5 of 13 publications

Conference Committee Involvement (1)

Modeling, Systems Engineering, and Project Management for Astronomy VIII

10 June 2018 | Austin, Texas, United States

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