Papers by Tzu-chiang Shen
Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation V
Ground-based and Airborne Instrumentation for Astronomy IX
Astronomical Data Analysis Software and Systems XXVII, Apr 1, 2020
Journal of Astronomical Telescopes, Instruments, and Systems
Software and Cyberinfrastructure for Astronomy VII
Software and Cyberinfrastructure for Astronomy VII
Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation V
IEEE Sensors Journal, 2018
The cameras of a close-range photogrammetry system must be calibrated to find their positions and... more The cameras of a close-range photogrammetry system must be calibrated to find their positions and optical properties. This is a crucial step in ensuring the performance of the complete system, especially if micrometric precision over a large field of view and long-term reproducibility is required. The target positions within the images for camera calibration and measurements are perturbed if stability between images is not achieved. This paper aims to evaluate the optimal conditions to guarantee the stability of the target images during measurements and calibration. The effect of temperature on the target positions is estimated to be about 0.1 pixels during a camera warmup period of 20 min or more. This effect is reduced to about 0.02 pixels after a warm-up period of less than 10 min by developing a controller for the camera's pixel clock. Additionally, an approximately 22% variation of illumination intensity is found to cause a small, but clearly measurable effect between images. Other aspects studied here are the illumination angle and the target characteristics. A 180 • movement of the illumination source with respect to the camera produces a 0.3 pixel change in the target locations when masked retroreflective targets are involved. In contrast, this effect is diminished by a factor of about ten with the use of larger, opaque targets.
Software and Cyberinfrastructure for Astronomy III, 2016
During operations, the ALMA observatory generates a huge amount of logs which contain not only va... more During operations, the ALMA observatory generates a huge amount of logs which contain not only valuable information related to specific failures but also for long term performance analysis. We implemented a big data solution based on Elasticsearch, Logstash and Kibana. They are configured as decoupled system which causes zero impact on the existent operations. It is able to keep more than six months of operation logs online. In this paper, we'll describe this infrastructure, applications built on top of it, and the problems that we faced during its implementation.
Proceedings of the First International Conference on Informatics in Control, Automation and Robotics, 2004
This paper describes a new method of image pattern recognition based on the Hausdorff Distance. T... more This paper describes a new method of image pattern recognition based on the Hausdorff Distance. The technique looks for similarities between a given pattern and its possible representations within an image. This method performs satisfactorily when confronted to image perturbations or partial occlusions. An extension of the classical Hausdorff Distance technique chooses the best candidate among multiple suboptimal solutions. The search strategy is based on the Branch and Bounds algorithm, where cells with low probability of containing the optimal solution are pruned, while feasible cells are divided again until the optimal solution is found. By using this strategy, exhaustive and no-informative searches are avoided among the possible combinations, reducing the processing time considerably. A case study is presented, where the proposed method is applied to calibration of surveillance radars using hydrographic charts as models for the radar echo images.
Ground-based and Airborne Instrumentation for Astronomy VII, 2018
After completion of its final-design review last year, it is full steam ahead for the constructio... more After completion of its final-design review last year, it is full steam ahead for the construction of the Multi Object Optical and Near-infrared Spectrograph (MOONS) instrument-the next generation multi-object spectrograph for the VLT. This remarkable instrument will combine for the first time: the 8 m collecting power of the VLT, 1001 optical fibers with individual robotic positioners and both medium-and high-resolution spectral coverage across the wavelength range 0.65µm-1.8 µm. Such a facility will allow a veritable host of Galactic, Extragalactic and Cosmological questions to be addressed. In this paper we will report on the current status of the instrument, details of the early testing of key components and the major milestones towards its delivery to the telescope.
arXiv: Instrumentation and Methods for Astrophysics, 2020
MOONS is the new Multi-Object Optical and Near-infrared Spectrograph currently under construction... more MOONS is the new Multi-Object Optical and Near-infrared Spectrograph currently under construction for the Very Large Telescope (VLT) at ESO. This remarkable instrument combines, for the first time, the collecting power of an 8-m telescope, 1000 fibres with individual robotic positioners, and both low- and high-resolution simultaneous spectral coverage across the 0.64-1.8 micron wavelength range. This facility will provide the astronomical community with a powerful, world-leading instrument able to serve a wide range of Galactic, extragalactic and cosmological studies. Construction is now proceeding full steam ahead and this overview article presents some of the science goals and the technical description of the MOONS instrument. More detailed information on the MOONS surveys is provided in the other dedicated articles in this Messenger issue.
Ground-based and Airborne Instrumentation for Astronomy VIII, 2020
The Multi Object Optical and Near-infrared Spectrograph (MOONS) instrument is the next generation... more The Multi Object Optical and Near-infrared Spectrograph (MOONS) instrument is the next generation multi-object spectrograph for the VLT. This powerful instrument will combine for the first time: the large collecting power of the VLT with a high multipexing capability offered by 1000 optical fibres moved with individual robotic positioners and a novel, very fast spectrograph able to provide both low- and high-resolution spectroscopy simultaneously across the wavelength range 0.64μm - 1.8μm. Such a facility will provide the astronomical community with a powerful, world-leading instrument able to serve a wide range of Galactic, Extragalactic and Cosmological studies. Th final assembly, integration and verification phase of the instrument is now about to start performance testing.
The Atacama Large Millimeter /sub-millimeter Array (ALMA) has been working in operations phase re... more The Atacama Large Millimeter /sub-millimeter Array (ALMA) has been working in operations phase regime since 2013. The transition to the operations phase has changed the priorities within the observatory, in which, most of the available time will be dedicated to science observations at the expense of technical time required for testing newer version of ALMA software. Therefore, a process to design and implement a new simulation environment, which must be comparable - or at least- be representative of the production environment was started in 2017. Concepts of model in the loop and hardware in the loop were explored. In this paper we review and present the experiences gained and lessons learned during the design and implementation of the new simulation environment.
arXiv: Instrumentation and Methods for Astrophysics, 2020
HIRES will be the high-resolution spectrograph of the European Extremely Large Telescope at optic... more HIRES will be the high-resolution spectrograph of the European Extremely Large Telescope at optical and near-infrared wavelengths. It consists of three fibre-fed spectrographs providing a wavelength coverage of 0.4-1.8 mic (goal 0.35-1.8 mic) at a spectral resolution of ~100,000. The fibre-feeding allows HIRES to have several, interchangeable observing modes including a SCAO module and a small diffraction-limited IFU in the NIR. Therefore, it will be able to operate both in seeing and diffraction-limited modes. ELT-HIRES has a wide range of science cases spanning nearly all areas of research in astrophysics and even fundamental physics. Some of the top science cases will be the detection of bio signatures from exoplanet atmospheres, finding the fingerprints of the first generation of stars (PopIII), tests on the stability of Nature's fundamental couplings, and the direct detection of the cosmic acceleration. The HIRES consortium is composed of more than 30 institutes from 14 cou...
SCI Overview The priorities have been changing in the observatory since entering into operations.... more SCI Overview The priorities have been changing in the observatory since entering into operations. This transition has lead to a reduction in the technical time both for software testing and engineering tasks such as maintenance and hardware integration in benefit of having more time for science operations, and this tendency will increase in the following year. The previous reasons have lead to realize one of the weakest areas in the existent infrastructure for software testing: The simulation environment of the ALMA software.
Ground-based and Airborne Instrumentation for Astronomy VII, 2018
We present the results from the phase A study of ELT-HIRES, an optical-infrared High Resolution S... more We present the results from the phase A study of ELT-HIRES, an optical-infrared High Resolution Spectrograph for ELT, which has just been completed by a consortium of 30 institutes from 12 countries forming a team of about 200 scientists and engineers. The top science cases of ELT-HIRES will be the detection of life signatures from exoplanet atmospheres, tests on the stability of Nature's fundamental couplings, the direct detection of the cosmic acceleration. However, the science requirements of these science cases enable many other groundbreaking science cases. The baseline design, which allows to fulfil the top science cases, consists in a modular fiberfed cross-dispersed echelle spectrograph with two ultra-stable spectral arms providing a simultaneous spectral range of 0.4-1.8 µm at a spectral resolution of ∼ 100, 000. The fiber-feeding allows ELT-HIRES to have several, interchangeable observing modes including a SCAO module and a small diffraction-limited IFU.
Modeling, Systems Engineering, and Project Management for Astronomy VI, 2016
The ALMA software is a large collection of modules, which implements the functionality needed for... more The ALMA software is a large collection of modules, which implements the functionality needed for the observatory day-today operations. The main ALMA software components include: array/antenna control/correlator, submission/processing of science proposals, telescope calibration and data archiving. The implementation of new features and improvements for every software subsystem must be coordinated by considering developers schedule, observatory milestones and testing resources available to verify new software. This paper describes the software delivery process adopted by ALMA since the construction phase and its evolution until these days. It also presents the acceptance procedure implemented by the observatory for validating the software used for science operations. Main roles of the software delivery and acceptance processes are mentioned on this paper by including their responsibility at the different development and testing phases. Finally, some ideas are presented about how the model should change in the near future by considering the operational reality of ALMA Observatory.
Software and Cyberinfrastructure for Astronomy III, 2016
ALMA software development cycle includes well defined testing stages that involves developers, te... more ALMA software development cycle includes well defined testing stages that involves developers, testers and scientists. We adapted Behavior Driven Development (BDD) to testing activities applied to Telescope Calibration (TELCAL) software. BDD is an agile technique that encourages communication between roles by defining test cases using natural language to specify features and scenarios, what allows participants to share a common language and provides a high level set of automated tests. This work describes how we implemented and maintain BDD testing for TELCAL, the infrastructure needed to support it and proposals to expand this technique to other subsystems.
SPIE Proceedings, 2016
The Multi-Object Optical and Near-infrared Spectrograph (MOONS) will cover the Very Large Telesco... more The Multi-Object Optical and Near-infrared Spectrograph (MOONS) will cover the Very Large Telescope's (VLT) field of view with 1000 fibres. The fibres will be mounted on fibre positioning units (FPU) implemented as two-DOF robot arms to ensure a homogeneous coverage of the 500 square arcmin field of view. To accurately and fast determine the position of the 1000 fibres a metrology system has been designed. This paper presents the hardware and software design and performance of the metrology system. The metrology system is based on the analysis of images taken by a circular array of 12 cameras located close to the VLTs derotator ring around the Nasmyth focus. The system includes 24 individually adjustable lamps. The fibre positions are measured through dedicated metrology targets mounted on top of the FPUs and fiducial markers connected to the FPU support plate which are imaged at the same time. A flexible pipeline based on VLT standards is used to process the images. The position accuracy was determined to ∼ 5 μm in the central region of the images. Including the outer regions the overall positioning accuracy is ∼25 μm. The MOONS metrology system is fully set up with a working prototype. The results in parts of the images are already excellent. By using upcoming hardware and improving the calibration it is expected to fulfil the accuracy requirement over the complete field of view for all metrology cameras.
Uploads
Papers by Tzu-chiang Shen