Large gravitational wave detection telescopes mostly are installed in extreme environments such as plateaus and Antarctica, which are quite heavy and require high-speed and high-precision scanning. Put in such conditions of low temperature and heavy load, traditional bearings are faced with problems like creeping and lubrication failure, which make it difficult to achieve the movements required. In addition, due to the remote sites and the tight energy supply, the telescope system needs to consider energy saving. To solve these problems, this paper puts forward an electromagnetic suspension (EMS) unloading scheme. Firstly, the effectiveness of the scheme is verified from the perspective of power. Secondly, the mathematical model of the electromagnetic force is derived and verified by Maxwell 2D simulation software. When the air gap is 0.9mm and the current reaches 0.5Α , the maximum deviation between the calculated value and the simulated value of the electromagnetic force is only 0.6%, indicating the correctness of the theoretical calculation. This paper can provide a reference for similar engineering designs.
It is difficult to use traditional bearings for the telescope base in extreme environments, and the use of spliced arc guides can solve this problem. This paper studies the change of the friction force of the arc motion rolling guide under the condition of splicing error. In this paper, simulation methods are used to explore the speed change of the arc guide under different splicing error conditions, the Coulomb model is used to calculate the friction force change, and then the polynomial fitting is used to observe its fluctuation. The research results show that when the splicing error is 0.005 mm and 0.01 mm, the friction force of the arc motion rolling guide is roughly 10-15 N. Moreover, when the splicing error is 0.01 mm, the frictional force changes more discretely.
In Ali’s original gravitational wave detection project, The gravitational wave detection telescope requires a large-size azimuth shaft coupling, while meeting the needs of a large number of cables and high torsional rigidity. Torsional stiffness needs to reach 1×10^5 N⋅ m/rad. Due to its simple structure and convenient processing, the slit coupling can be widely used in the transmission of the azimuth shafting of the astronomical telescope. This paper uses finite element software to analyze and compare the key structural parameters of the slit coupling and optimize the torsional stiffness. A large-size slit coupling suitable for gravitational wave detection telescopes was designed in combination with project requirements, which meets the design requirements and has certain guiding significance for the design of other slit couplings.
The 1m telescope introduced in this paper is made for Nanjing University to do the study on the time-domain survey. The optical system of this telescope is a kind of the primary focus system. Tube designed for the 1m telescope is extremely important to support and define the optical elements and the 6K × 6K camera, because the alignment requirements between these assembles are pretty tight. Two types of the tube structure are designed in this paper, one is the cylindrical enclosed tube, the other is the open truss tube. The parameters of cylindrical tube and truss tube are optimized via the finite element analysis software ANSYS Workbench. Based on the mass, stiffness, cost performance etc. the performance of these two kinds of tube is compared to find a feasible and reliable tube design. Considering the main factors, truss tube is selected for the NU 1m telescope.
With the diameter increasing for large aperture telescope primary mirror, the gravity caused by the increased of surface size will directly affect the quality of optical imaging, the adjustment of large aperture primary mirror will be frequent according to the requirement of observation. As the angle and the azimuth’s transformation of primary mirror influences the surface shape accuracy immediately, the rational design of the primary mirror supporting structure is of crucial importance. Now the general method is to use ANSYS APDL programming, which is inconvenient and complex to fit for the different components, the calculation require much time and the analysis is lack of efficient. Taking the diameter of 1.12 m telescope primary mirror as the research objection, the paper combine the actual design parameters of SONG telescope, respectively using ANSYS WORKBENCH to employ the primary mirror axial and lateral support model in finite element method, the optimal solution is obtained by optimization design and the change rule of mirror surface deformation under inclined condition is studied. The optimization results according with the requirements of the primary mirror comprehensive error proves that the optimization analysis method is available and applicable.
China SONG telescope would achieve the goal for long time continuous, uninterrupted, full automatic observation and
works in the diffraction limit condition, what's more, it must realize 0.3 arc second tracking precision without guide star.
This paper describes the integration and fine-tuning of the China SONG Drive Systems. It discusses the different problems
encountered during the integration and commissioning. The servo model that was used to simulate the problems and to find
new solutions is described as well as test results and advanced analysis methods.
SONG (Stellar Oscillation Network Group) is an international project to form a global observing network of eight 1- meter class telescopes. China joined this project and funded one node telescope for this network. By the end of 2013, the Chinese SONG telescope has been installed on the Delinha observing site of Purple Mountain Observatory in Qinghai province. This paper will give the introduction of this telescope, including its optical system, structure and control system. Besides, the preliminary observing performance of the telescope on site will be given in the second part of this paper.
SONG is an international initiative to design, build, and utilize a global network of eight 1-meter class
telescopes to be operated as a whole-Earth telescope. The telescope is composed of system of azimuth axis, rotating
table, fork, system of elevation axis, top-ring, up and down truss, system of primary mirror and so on. For an
astronomical telescope mount, having a high stiffness to support the mirror cell and instruments is its basic function.
Finite element method (FEM) is a powerful tool to help structure design engineer to achieve this goal. In this paper, with
the help of ANSYS, the static and modal analysis, calculation and optimization of the SONG telescope mount will be
given. The modal result which is used for avoiding resonance and fatigue failure of the telescope acquire natural
frequency of telescope. The FEM results show that the structure, designed for SONG telescope, is feasible and reliable
and have a high stiffness-to-weight ratio to meet the optical demands.
KEYWORDS: Active optics, MATLAB, Wavefront sensors, Optical design, Telescopes, Control systems design, Wavefronts, C++, Software development, Computing systems
China has joined the international global network SONG project and will build one 1-meter telescope as one node of
SONG network. This paper shows the upper computer software system design under Linux operating system for active
optics control system of Chinese SONG telescope. The upper computer software developed in this paper under Linux OS
has three functions: detection of S-H wavefront, calculation of mirror correction force and communication with the
controller of hardware. We will introduce the three modules developed under Linux environment: wavefront image
processing module, communication module and GUI module.
The standard SONG node structure of control system is presented. The active optical control system of the project is a
distributed system, and a host computer and a slave intelligent controller are included. The host control computer collects
the information from wave front sensor and sends commands to the slave computer to realize a closed loop model. For
intelligent controller, a programmable logic controller (PLC) system is used. This system combines with industrial
personal computer (IPC) and PLC to make up a control system with powerful and reliable.
Active support scheme may decide the deformation of the optical surface figure of the primary mirror. Two active
support schemes have been designed for 1-m primary mirror, and the performance of each support scheme is conducted.
Finite element analysis (FEA) is employed to analyze the optical surface figures of the primary mirror, and optimizations
are carried out by using ANSYS for each support scheme to obtain the locations of the axial support. When the locations
are determined, axial support force sensitivities are calculated for the two support schemes in a case that a single axial
support has a force error of 0.5N. The correction ability of the active support system for both of support schemes are
analyzed when an arbitrary axial support is failure. Several low order Zernike modes are modeled with MATLAB
procedure, and active optics corrections are applied to these modes for the two active supports. Thermal deformation of
the mirror is also corrected for the two schemes.
The paper reports optical system of a 1 meter diameter telescope dedicated to Stellar Observations
Network Group (SONG) for the National Astronomical Observatories, CAS. SONG is an international
cooperative project, Optimize the design for Asteroseismology purposes. According to the prototype of
SONG, Chinese SONG telescope includes Cassegrain telescope, Nasmyth platform, Coudé train,
Coudé focal plane, Shack-Hartmann wavefront sensor and spectrograph. The telescope will provide a
field of view of 65 arcsec at the Nasmyth F/36.67 focus, 10 arcsec at the F/6 Coudé focus. The rotating
tertiary mirror directs the light to the two Nasmyth foci, one for Shack-Hartmann wavefront sensor, the
other for Nasmyth platform and spectrograph.
In recent years, Nanjing Institute of Astronomical Optics and Technology (NIAOT) has made several telescopes for
observatories all around the world. In 2011 NIAOT just finished the development of a 2.5m optical/infrared telescope
mount. First part of this paper is to introduce the mount structure and their adjustment work. Second part is to give an
introduction of the mount performance test methods and test results finished on NIAOT workshop.
SONG is initiated by Danish to design, build, and utilize a global network of eight 1-meter class telescopes to be
operated as a whole-Earth telescope. China has joined the international SONG project in 2009 and will build one 1-meter
telescope as the node of SONG global network in China. Now the telescope is during the period of building. This paper
will give an introduction of Chinese SONG telescope, including telescope requirements, telescope design and other
information.
LAMOST is a kind of special reflecting Schmidt telescope which solved the problem to achieve both wide FOV and
large aperture on one telescope. This feature makes it competitive to do the large sky area survey work. According to the
configuration, the focal plate of this kind of telescope will perform three main motions: derotation, tilt and focusing.
Normally the focal plate will be supported at a certain height above ground. China has launched the astronomy research
at Antarctic Dome A and planned to set up a LAMOST-style telescope there. Considering the harsh environment and
terrible remote transportation, a kind of simple and compact support structure of focal plate is proposed in this paper
aiming at light weight, easy installation and easy adjustment, based on the review of LAMOST experiments. The
calculation and simulation results show that the compact support structure can meet the system requirements.
KEYWORDS: Telescopes, Mirrors, Control systems, Computer programming, Astronomical imaging, Optical instrument design, Control systems design, Astronomy, Astronomical telescopes, Information technology
Telescope is a very important tool for astronomers to survey and study the stellar stars and astronomical phenomena. The
performance of a telescope is its capability to track the observing objects and keep the image on the field of view during
the observing period. All these functions will be achieved by telescope mount, including mount control system. The
mount is to support the mirror cell and keep the mirror cell position stability. Meanwhile, with the help of control
system, the mount acts as tracker of the observing objects. So, for a telescope, the mount and its control system play an
important role during the telescope operation. This paper gives an introduction of a mount structure designed for a 2.5m
optical/infrared telescope and the corresponding control system. Some of preliminary test results are also given in this
paper.
Friction drive is used in some large astronomical telescopes in recent years. Comparing to the direct drive, friction drive
train consists of more buildup parts. Usually, the friction drive train consists of motor-tachometer unit, coupling, reducer,
driving roller, big wheel, encoder and encoder coupling. Normally, these buildup parts will introduce somewhat errors to
the drive system. Some of them are random error and some of them are systematic error. For the random error, the
effective way is to estimate their contributions and try to find proper way to decrease its influence. For the systematic
error, the useful way is to analyse and test them quantitively, and then feedback the error to the control system to correct
them. The main task of this paper is to analyse these error sources and find out their characteristics, such as random error,
systematic error and contributions. The methods or equations used in the analysis will be also presented detail in this
paper.
Telescope is a very important tool for astronomers to survey and study the stellar stars and astronomical phenomena. The
performance of a telescope is its capability to track the observing objects and keep the image on the field of view during
the observing period. All these functions will be achieved by telescope mount, including mount control system. The
mount is to support the mirror cell and keep the mirror cell position stability. Meanwhile, with the help of control system,
the mount acts as tracker of the observing objects. So, for a telescope, the mount and its control system play an important
role during the telescope operation. This paper introduces the structure design and analysis of the mount system of a
2.5m optical/infrared telescope, such as azimuth axis, elevation axis, M2 positioning system, M3 positioning system, and
so on. Especially, an innovative support and escape mechanism of M3 will be proposed and analysed in this paper.
For an astronomical telescope mount, having a high stiffness to support the mirror cell and instruments is its basic
function. Traditionally, the mount is composed of azimuth base, azimuth axis, fork, altitude axis, tube, top-ring, etc. On
the other hand, telescope will be driven to track the observing objects during operation. So, for the mechanical structure
design engineer, finding a high stiffness-to-weight ratio mount is the main task. Finite element method (FEM) is a
powerful tool to help structure design engineer to achieve this goal. ANSYS is one of these kinds of finite element
method software. In this paper, with the help of ANSYS, the static and dynamic analysis, calculation and optimization of
a 2.5m telescope mount will be given. The FEM results show that the structure, designed for 2.5m telescope, is feasible
and reliable and have a high stiffness-to-weight ratio to meet the optical demands.
The paper discusses one direct drive telescope experiment bed (DDTEB), which is designed to simulate the
modern telescope tracking system. The main task is to find the problem and the reliability which might be met in the real
direct drive tracking system of the telescope and how to handle them. More information and experience will be acquired
and accumulated to use the direct drive technology in the telescope complex motion system of Chinese telescope in the
future.
The South Pole, especially the highest plateau Dome A, is the best place to locate telescopes in the world due to its
compelling environment, such as dry air, low humidity, low wind speeds, low values of sky noise, etc. For this site,
especially significant is its very clean air with the lowest concentration of atmospheric aerosols and its negligible
artificial light pollution. But the air temperature in Dome-A is extremely low. The lowest air temperature is about 89
degrees below zero. On the other hand, Dome A is covered with deep snow. In order to build and operate a telescope at
such low temperature successfully, some of the problems caused by low temperature should be considered and tested
through experiments. According to the Chinese Antarctic 2m LAMOST-style telescope project, a conceptual design of
tracking system for a 2 meter optical and infrared telescope fitting to operate at Dome-A, including axes structure,
materials, drive systems, lubricant and feasible ways to install telescope will be discussed in this paper.
This paper describes four different drive systems adopted in LAMOST focal plane mechanism to achieve four movements: field derotation, focal plane attitude adjustment, focusing and move aside out of light path for optical checking. Different type drive systems, such as worm gear drive, spur gear drive, friction drive and direct drive, which
were devised and used in telescopes in the past years, have their own inherent characteristics and their working conditions. According to feasibility, reliability, suitability and cost effective, friction drive, worm gear drive, ball screw drive and chain drive are selected to as the drive systems for the above four movements. The on-shop test results show that all the drive systems have met the design goals with the accuracy of image field derotation 0.45 arcsec, attitude adjustment 0.24 arcsec, focusing 2 microns and move aside 0.02mm.
In the past years, friction drive was developed to overcome the inherent deficiencies in both worm drive and gear drive. No periodical error and free of backlash are the main advantages of friction drive. With the trend towards bigger and bigger aperture of the optical telescopes, there are some reports about friction drive employed to drive the telescopes. However friction drive has its own deficiencies, such as slippage and creepage. This report here describes the study on the friction drive finished in an experiment arranged by LAMOST project. It comprises three main parts. First, it introduces the experiment apparatus and proposes a new kind of measurement and adjustment mechanisms. Secondly, the report gives the analysis of friction drive characteristics theoretically, such as slippage, creepage and gives the results of corresponding experiments. The experiment shows that the lowest stable speed reaches 0.05"/s with precision of 0.009"(RMS), the preload has little influence on the drive precision in the case of constant velocity and the variable velocity when the angle acceleration is less than 5"/s2 with close loop control and the creepage velocity of this experiment system is 1.47"/s. Lastly, the analysis in the second section lists some measures to improve the precision and stability further. These measures have been actually conducted in the testing system and proved to be reliable.
The Large sky Area Multi-Object fiber Spectroscopic Telescope is a very special reflecting Schmidt telescope with a 40 m long optical axis between the reflecting Schmidt correcting plate and the spherical main mirror. In the middle is located the spherical focal plane of 1.75 m in diameter. The reflecting Schmidt correcting plate serves not only to correct wavefront by active optics but also to point and track celestial objects by normal tracking with collaboration of the focal plane to form a special mounting and tracking system. In this paper, the operational principle and technical specification of the tracking system is briefed. Design and test measurement as well as driving mode of both the Schmidt plate and the focal plane are investigated with structural calculations and analyses. The paper is closed with the conclusion that the mounting and tracking system is to meet global technical specifications of the LAMOST excellently.
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