Rendong Nan

THE FIVE-HUNDRED-METER APERTURE SPHERICAL RADIO TELESCOPE (FAST) PROJECT

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is a Chinese mega-science project funded by the National Development and Reform Commission (NDRC). The National Astronomical Observatories of China (NAOC) is in charge of its construction and the subsequent operation. Upon its expected completion in September of 2016, FAST will surpass the 300-meter Arecibo and the 100-meter GBT in terms of absolute sensitivity in the 70 MHz to 3 GHz bands. In this paper, we report the current status, the key science goals, and the aspiration of its early sciences. A special emphasis is paid to its innovative fatigue-resistant fibers, which are critical for the control and data acquisition under the unique FAST design.

Pulsar science with the Five hundred metre Aperture Spherical Telescope

With a collecting area of 70 000 m 2 , the Five hundred metre Aperture Spherical Telescope (FAST) will allow for great advances in pulsar astronomy. We have performed simulations to estimate the number of previously unknown pulsars FAST will find with its 19-beam or possibly 100-beam receivers for different survey strategies. With the 19-beam receiver, a total of 5200 previously unknown pulsars could be discovered in the Galactic plane, including about 460 millisecond pulsars (MSPs). Such a survey would take just over 200 days with eight hours survey time per day. We also estimate that, with about 80 six-hour days, a survey of M 31 and M 33 could yield 50–100 extra-Galactic pulsars. A 19-beam receiver would produce just under 500 MB of data per second and requires about 9 tera-ops to perform the major part of a real time analysis. We also simulate the logistics of high-precision timing of MSPs with FAST. Timing of the 50 brightest MSPs to a signal-to-noise of 500 would take about 24 h per epoch.

Singularity analysis of fine-tuning Stewart platform for large radio telescope using genetic algorithm

Abstract A new singularity analysis method for general six degree-of-freedom (DOF) Stewart platform using genetic algorithm (GA) is proposed in this paper. The Jacobian matrix of Stewart platform is first deduced, then the square of determinant of the Jacobian matrix is selected as the objective function, and the minimal of this objective function is searched in the workspace of Stewart platform by the GA. The singularity of Stewart platform depends on this minimal objective function: if this value is zero, the singularity of Stewart platform will take place, otherwise, the Stewart platform is singularity-free. The effectiveness of this new genetic singularity analysis method is validated by the singularity analysis of a six-DOF fine-tuning Stewart platform for the next generation large radio telescope. The results have shown that the fine-tuning Stewart platform is singularity-free, which has laid a solid base for the requirement of high precision trajectory tracking for the next generation large radio telescope.

Pulsar Observations with Radio Telescope FAST

FAST, Five hundred meter Aperture Spherical Telescope, is the Chinese effort for the international project SKA, Square Kilometer Array. An innovative engineering concept and design pave a new road to realizing huge single dish in the most effective way. Three outstanding features of the telescope are the unique karst depressions as the sites, the active main reflector which corrects spherical aberration on the ground to achieve full polarization and wide band without involving complex feed system, and the light focus cabin driven by cables and servomechanism plus a parallel robot as secondary adjustable system to carry the most precise parts of the receivers. Besides a general coverage of those critical technologies involved in FAST concept, the progresses in demonstrating model being constructed at the Miyun Radio Observatory of the NAOC is introduced. Being the most sensitive radio telescope, FAST will enable astronomers to jumpstart many of science goals, for example, the natural hydrogen line surveying in distant galaxies, looking for the first generation of shining objects, hearing the possible signal from other civilizations, etc. Among these subjects, the most striking one could be pulsar study. Large scale survey by FAST will not only improve the statistics of the pulsar population, but also may offer us a good fortune to pick up more of the most exotic, even unknown types like a sub-millisecond pulsar or a neutron star – black hole binary as the telescope is put into operation.

The wind-induced vibration control of feed supporting system for large spherical radio telescope using electrorheological damper

Considering the wind-induced vibration of the feed supporting system with cables for the optomechatronics design project of next generation large spherical radio telescopes, a prototype of adaptive electrorheological (ER) damper is designed to realize additional damping control of this vibration. The model of wind is first developed to implement this design and simulations. The model of the designed ER adaptive damper is described in detail, and the strategy of additional damping control using the controllable field-dependent damping force of the ER damper to counteract the wind force is proposed. The numerical simulation results have shown the validity of the designed adaptive ER damper to suppress the wind-induced vibration of the feed supporting system, and the additional damping vibration amplitude can be suppressed to one-half of the original amplitude without ER damper.

Preparatory Study for Constructing FAST, the World's Largest Single Dish

A 500-m aperture spherical telescope (FAST) was funded by the National Development and Reform Commission of China (NDRC) in July 2007 and will be located in the unique Karst region, a sinkhole-like landform, in Guizhou province. FAST can be seen as a modified ldquoArecibordquo type radio telescope using many innovative techniques, with as much as twice the collecting area and a wider sky coverage. FAST has, first, an active reflector, conforming to a paraboloid of revolution from a sphere in real time through actuated control, which enables the realization of wide bandwidth and full polarization capability by using standard feed design. Secondly, it has a light focus cabin suspension system, integrating optical, mechanical, and electronic technologies, reducing effectively the cost of the support structure and control system. With such a huge collecting area of more than 30 football fields, FAST will become the largest single dish ever built. Here we will summarize the FAST concept and the milestones achieved in experiments on its key technologies, i.e., site exploration, active reflector prototyping, focus cabin driving mechanism, measurement and control techniques, and the receiver layout. The Miyun FAST demonstrator also will be presented.

The Five-hundred-meter Aperture Spherical Radio Telescope Project and its Early Science Opportunities

The National Astronomical Observatories, Chinese Academy of Science (NAOC), has started building the largest antenna in the world. Known as FAST, the Five-hundred-meter Aperture Spherical radio Telescope is a Chinese mega-science project funded by the National Development and Reform Commission (NDRC). FAST also represents part of Chinese contribution to the international efforts to build the square kilometer array (SKA). Upon its finishing around September of 2016, FAST will be the most sensitive single-dish radio telescope in the low frequency radio bands between 70 MHz and 3 GHz. The design specifications of FAST, its expected capabilities, and its main scientific aspirations were described in an overview paper by Nan et al . (2011). In this paper, we briefly review the design and the key science goals of FAST, speculate the likely limitations at the initial stages of FAST operation, and discuss the opportunities for astronomical discoveries in the so-called early science phase.

Introduction to FAST: five hundred meter Aperture Spherical radio Telescope

FAST is an Arecibo-type antenna with 3 outstanding aspects: the unique karst depression as the site; the active main reflector which corrects spherical aberration on the ground to achieve full polarization and wide band without involving complex feed system; and the light focus cabin driven by cables and servomechanism plus a parallel robot as secondary adjustable system to carry the most precise parts of the receivers. These design features will enable FAST to jumpstart many of science goals, such as HI neutral hydrogen line survey, pulsar survey, largest station in VLBI network, spectral line observations and Search for aliens technologies. The feasibility studies for FAST have been carried out for 14 years, being supported by Chinese and world astronomical communities. Funding for Project FAST has been approved by the National Development and Reform commission NDRC in July of 2007 with a capital budget ~ 600 millions RMB and a project time of 5.5 years from the foundation.

Working space analysis and optimization of the main positioning system of FAST cabin suspension

This paper devotes to the working space analysis of the main positioning system of FAST cabin suspension, a flexible-cable-driven parallel manipulator. The problem formulation is deduced through equilibrium analysis of the cabin platform and suspension cables, which changes subsequently into a nonlinear constrained optimization intending a uniform allocation of the six cable tension force. The analysis verifies the accessibility of focus cabin to the whole focus surface. The optimization investigates the orientation of the focus cabin under equilibrium and the optimal cable forces, as well as elaborates their importance in the finite element modeling of the cable-cabin system and the respective layout designs of the rotator, Stewart stabilizer and capstan motors. In the end, the influences of the tower height and the position of mass center of the focus cabin on the optimization results are discussed.

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) project

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is a Chinese mega-science project funded by the National Development and Reform Commission (NDRC). The National Astronomical Observatories of China (NAOC) is in charge of its construction and the subsequent operation. Upon its expected completion in September of 2016, FAST will surpass the 300-meter Arecibo and the 100-meter GBT in terms of absolute sensitivity in the 70 MHz to 3 GHz bands. In this paper, we report the current status, the key science goals, and the aspiration of its early sciences. A special emphasis is paid to its innovative fatigue-resistant fibers, which are critical for the control and data acquisition under the unique FAST design.