Large Aperture Telescope Research Articles

基于结构函数的大口径望远镜光机系统误差分配

An error evaluation method for the opto-mechanical system of a large aperture telescope was proposed based on structure function.The error transfer property of the structure function was analyzed,and the numerical simulation of the atmosphere disturbance was obtained by inverting the Power Spectral Density(PSD).Then,the error allocation of opto-mechanical system was built with the structure function consequently.The method was proved to be correct and feasible with the application in the 1.23 mtelescope in the Changchun Institute of Optics,Fine Mechanics and Physics.Finally,the method was used in the tertiary mirror system of 30mtelescope(TMT),and the print through effect of the system in the atmosphere disturbance was researched.The experiment show that the resolution ability of the system for print through peaks does not weaken at different seeings.The method proposed has important significant for reducing the cost efficient of the large aperturetelescope and lowering its risk in developing and use processing.

Topology optimization-based lightweight primary mirror design of a large-aperture space telescope.

For the large-aperture space telescope, the lightweight primary mirror design with a high-quality optical surface is a critical and challenging issue. This work presents a topology optimization-based design procedure for a lightweight primary mirror and a new mirror configuration of a large-aperture space telescope is obtained through the presented design procedure. Inspired by the topology optimization method considering cast constraints, an optimization model for the configuration design of the mirror back is proposed, through which the distribution and the heights of the stiffeners on the mirror back can be optimized simultaneously. For the purpose of minimizing the optical surface deviation due to self-weight and polishing pressure loadings, the objective function is selected as to maximize the mirror structural stiffness, which can be achieved by minimizing the structural compliance. The total mass of the primary mirror is assigned as the constraint. In the application example, results of the optimized design topology for two kinds of mass constraints are presented. Executing the design procedure for specific requirements and postprocessing the topology obtained of the structure, a new mirror configuration with tree-like stiffeners and a multiple-arch back in double directions is proposed. A verification model is constructed to evaluate the design results and the finite element method is used to calculate the displacement of the mirror surface. Then the RMS deviation can be obtained after fitting the deformed surface by Zernike polynomials. The proposed mirror is compared with two classical mirrors in the optical performance, and the comparison results demonstrate the superiority of the new mirror configuration.

THE MASS OF THE CENTRAL BLACK HOLE IN THE NEARBY SEYFERT GALAXY NGC 5273

We present the results of a reverberation-mapping program targeting NGC5273, a nearby early-type galaxy with a broad-lined active galactic nucleus. Over the course of the monitoring program, NGC5273 showed strong variability that allowed us to measure time delays in the responses of the broad optical recombination lines to changes in the continuum flux. A weighted average of these measurements results in a black hole mass determination of $M_{\rm BH} = (4.7 \pm 1.6) \times 10^6$ M$_{\odot}$. An estimate of the size of the black hole sphere of influence in NGC5273 puts it just at the limit of the resolution achievable with current ground-based large aperture telescopes. NGC5273 is therefore an important future target for a black hole mass determination from stellar dynamical modeling, especially because it is the only nearby early-type galaxy hosting an AGN with a reverberation-based mass, allowing the best comparison for the masses determined from these two techniques.

Progress of FAST in science, technique and instrument

High-sensitive and large aperture telescope is the key equipment for radio observation. Five-hundred-meter Aperture Spherical radio Telescope (FAST) is a Chinese mega-science project to build the largest single dish radio telescope in the world. FAST will enable astronomers to jump-start many science goals, for example, surveying the neutral hydrogen in the Milky Way and other galaxies, detecting faint pulsars, hearing the possible signals from other civilizations, etc. The paper aims to overview the latest progress of FAST including science, technique and equipment.

The dark nature of GRB 130528A and its host galaxy

We study the dark nature of GRB 130528A through multi-wavelength observations and conclude that the main reason for the optical darkness is local extinction inside of the host galaxy. Automatic observations were performed at BOOTES-4/MET robotic telescope. We also triggered target of opportunity (ToO) observation at the OSN, IRAM PdBI and the GTC+OSIRIS. The host galaxy photometric observations in optical to near-infrared (nIR) wavelengths were achieved through large ground-based aperture telescopes, such as the 10.4m GTC, the 4.2m WHT, 6m BTA, and the 2m LT. Based on these observations, spectral energy distributions (SED) for the host galaxy and afterglow were constructed. Thanks to mm observations at PdBI, we confirm the presence of a mm source within the XRT error circle that faded over the course of our observations and identify the host galaxy. However, we do not find any credible optical source within early observations with BOOTES-4/MET and 1.5m OSN telescopes. Spectroscopic observation of this galaxy by GTC showed a single faint emission line that likely corresponds to [OII] 3727\{AA} at a redshift of 1.250+/-0.001 implying a SFR(M_sun/yr) > 6.18 M_sun/yr without correcting for dust extinction. The probable extinction was revealed through analysis of the afterglow SED, resulting in a value of AV >= ~ 0.9 at the rest frame, this is comparable to extinction levels found among other dark GRBs. The SED of the host galaxy is explained well (chi2/d.o.f.=0.564) by a luminous (MB=-21.16), low-extinction (AV =0, rest frame), and aged (2.6 Gyr) stellar population. We can explain this apparent contradiction in global and line-of-sight extinction if the GRB birth place happened to lie in a local dense environment. In light of having relatively small specific SFR (SSFR) ~ 5.3 M_sun/yr (L/L_star)-1, this also could explain the age of the old stellar population of host galaxy.

SEPARATED FRINGE PACKET OBSERVATIONS WITH THE CHARA ARRAY. II. ω ANDROMEDA, HD 178911, AND ξ CEPHEI

When observed with optical long-baseline interferometers (OLBI), components of a binary star which are sufficiently separated produce their own interferometric fringe packets; these are referred to as Separated Fringe Packet (SFP) binaries. These SFP binaries can overlap in angular separation with the regime of systems resolvable by speckle interferometry at single, large-aperture telescopes and can provide additional measurements for preliminary orbits lacking good phase coverage, help constrain elements of already established orbits, and locate new binaries in the undersampled regime between the bounds of spectroscopic surveys and speckle interferometry. In this process, a visibility calibration star is not needed, and the separated fringe packets can provide an accurate vector separation. In this paper, we apply the SFP approach to {\omega} Andromeda, HD 178911, and {\xi} Cephei with the CLIMB three-beam combiner at the CHARA Array. For these systems we determine component masses and parallax of 0.963${\pm}$0.049 $M_{\odot}$ and 0.860${\pm}$0.051 $M_{\odot}$ and 39.54${\pm}$1.85 milliarcseconds (mas) for {\omega} Andromeda, for HD 178911 of 0.802${\pm}$0.055 $M_{\odot}$ and 0.622${\pm}$0.053 $M_{\odot}$ with 28.26${\pm}$1.70 mas, and masses of 1.045${\pm}$0.031 $M_{\odot}$ and 0.408${\pm}$0.066 $M_{\odot}$ and 38.10${\pm}$2.81 mas for {\xi} Cephei.

COMPARISON OF PRESTELLAR CORE ELONGATIONS AND LARGE-SCALE MOLECULAR CLOUD STRUCTURES IN THE LUPUS I REGION

Turbulence and magnetic fields are expected to be important for regulating molecular cloud formation and evolution. However, their effects on subparsec to 100 parsec scales, leading to the formation of starless cores, is not well understood. We investigate the prestellar core structure morphologies obtained from analysis of the Herschel-SPIRE 350 $\mu$m maps of the Lupus I cloud. This distribution is first compared on a statistical basis to the large scale shape of the main filament. We find the distribution of the elongation position angle of the cores to be consistent with a random distribution, which means no specific orientation of the morphology of the cores is observed with respect to a large-scale filament shape model for Lupus I, or relative to a large-scale bent filament model. This distribution is also compared to the mean orientation of the large-scale magnetic fields probed at 350 $\mu$m with the Balloon-borne Large Aperture Telescope for Polarimetry (BLASTPol) during its 2010 campaign. Here again we do not find any correlation between the core morphology distribution and the average orientation of the magnetic fields on parsec scales. Our main conclusion is that the local filament dynamics - including secondary filaments that often run orthogonally to the primary filament - and possibly small-scale variations in the local magnetic field direction, could be the dominant factors for explaining the final orientation of each core.

Stand-off laser-induced breakdown spectroscopy of aluminum and geochemical reference materials at pressure below 1 torr

Laser-induced breakdown spectroscopy (LIBS) is an atomic emission spectroscopy that utilizes a highly irradiated pulse laser focused on the target surface to produce plasma. We obtain spectroscopic information from the microplasma and determine the chemical composition of the sample based on its elemental and molecular emission peaks. We develop a stand-off LIBS system to analyze the effect of the remote sensing of aluminum and various geochemical reference materials at pressures below 1torr. Using a commercial 4 inch refracting telescope, our stand-off LIBS system is configured at a distance of 7.2m from the four United States Geological Survey (USGS) geochemical samples that include granodiorite, quartz latite, shale-cody, and diabase, which are selected for planetary exploration. Prepared samples were mixed with a paraffin binder containing only hydrogen and carbon, and were pelletized for experimental convenience. The aluminum plate sample is considered as a reference prior to using the geochemical samples in order to understand the influence of a low pressure condition on the resulting LIBS signal. A Q-switched Nd:YAG laser operating at 1064nm and pulsed at 10Hz with 21.7 to 48.5mJ/pulse was used to obtain signals, which showed that the geochemical samples were successfully detected by the present stand-off detection scheme. A low pressure condition generally results in a decrease of the signal intensity, while the signal to noise ratio can vary according to the samples and elements of various types. We successfully identified the signals at below 1torr with stand-off detection by a tightly focused light detection and by using a relatively larger aperture telescope. The stand-off LIBS detection at low pressure is promising for potential detection of the minor elements at pressures below 1torr.

Searching for star-forming dwarf galaxies in the Antlia cluster

The formation and evolution of dwarf galaxies in clusters need to be understood, and this requires large aperture telescopes. In this sense, we selected the Antlia cluster to continue our previous work in the Virgo, Fornax, and Hydra clusters and in the Local Volume (LV). Because of the scarce available literature data, we selected a small sample of five blue compact dwarf (BCD) candidates in Antlia for observation. Using the Gemini South and GMOS camera, we acquired the Halpha imaging needed to detect star-forming regions in this sample. With the long-slit spectroscopic data of the brightest seven knots detected in three BCD candidates, we derived their basic chemical properties. Using archival VISTA VHS survey images, we derived K_S magnitudes and surface brightness profile fits for the whole sample to assess basic physical properties. FS90-98, FS90-106, and FS90-147 are confirmed as BCDs and cluster members, based on their morphology, K_S surface photometry, oxygen abundance, and velocity redshift. FS90-155 and FS90-319 did not show any H{\alpha} emission, and they could not be confirmed as dwarf cluster star-forming galaxies. Based on our data, we studied some fundamental relations to compare star forming dwarfs (BCDs and dIs) in the LV and in the Virgo, Fornax, Hydra, and Antlia clusters. Star-forming dwarfs in nearby clusters appear to follow same fundamental relations in the near infrared with similar objects in the LV, specifically the size-luminosity and the metallicity-luminosity, while other more fundamental relations could not be checked in Antlia due to lack of data.

基于功率谱的反射镜面形评价

Firstly,Power Spectral Density( PSD) is proposed for mirror surface figure evaluation in the large aperture telescope system as for some difficulties for Root Mean Square( RMS) in the evaluation of large scale variety and disadvantage of robust for rigid body displacement. Then,the decomposition arithmetic of PSD is analyzed with Zernike polynomial,and Zernike polynomial spectrum energy distribution is analyzed in some order. The algorithm has been used in the surface figure evaluation of a Φ 500 mm mirror,and energy distribution in the frequency domain of the actual mirror surface has been obtained. The experimental results indicate that the evaluation of PSD is more practical when used in large aperture mirror for their manufacture and testing and for the error budget allocation in telescope system. Finally,a kind of noncorrelative sub-aperture stitching method for evaluation of reflective mirror shape based on PSD is proposed which can be used in the large aperture telescope.

大口径光电探测设备主镜晃动的误差补偿

Large aperture optical detection equipment has the shaky with its elevation angle changing when the support point of primary mirror changes. This paper studies how compensate the measuring errors caused by the primary mirror shaking and improve the static measuring accuracy of the large aperture optical detection equipment. Firstly, the supporting structure and mechanic model of a 1m diameter telescope were presented. Then, a new error compensation method for the large aperture telescope was proposed based on the analysis of the traditional three axis error compensation method and spherical harmonic error compensation method. The calibration experiments for the optical detection equipment was performed. By selecting 32 stars whose refractions had been revised, the error of each system was solved obtain the primary mirror shaking error and the three axis difference. As comparison with the traditional error compensation method, it shows that the static measurement accuracy of the telescope has increased from 15.4 to 2.5 after the shaking error of the primary mirror is compensated. It concludes that the physical meaning of this method is clear, and each error component has good repeatability. It improves the static precision of large aperture telescope by compensating the shaking errors of primary mirror.

30m望远镜三镜镜面面形误差的斜率均方根评价

As the traditional method based on Root Mean Square (RMS) is hard to accurately express middle spatial frequency errors of an optical surface in evaluation of a large aperture telescope, this paper proposes a new method based on SlopeRms to evaluate the optical surface. The method solves the SlopeRms in different space intervals after fitting the optical surface figure by Zernike polynomial. It can better quantify the small scale irregularities and the surface figure error from a smaller size grinding tool or from an aperture mirror surface figure error in multi-point support. The mathematical model of SlopeRms is established, how to calculate the SlopeRms is deduced and then the surface figure for TMT (Thirty Meter Telescope) tertiary mirror is evaluated by the proposed method. The obtained results show that the mirror surface figure error is 0.9 rad, which is better than that of traditional method (RMS=115 nm) and meets the design requirement. It means that the method based on SlopeRms can objectively evaluate the mirror surface figure error for a large aperture telescope.

2m望远镜塔台的构建

The site choice and pier foundation of existing ground based large aperture telescopes were analyzed and how to construct a pier for a 2 m aperture telescope was explored. Firstly, the relationship between the astronomical seeing and the pier height of a telescope was discussed and the pier height was determined to be 13 m by measuring the astronomical seeing of the seat of the telescope. Then, according to the requirements of pier construction of the 2 m aperture telescope, a simulation model was established, and the simulation analysis was performed by Ansys. A pier and ground base design scheme with a resonant frequency more than 30 Hz under the load condition of 30 t was proposed to resist a 5 level earthquake and certain wind load. Finally, the spectral analysis and random vibration method were used to research the responses of the pier designed to the earthquake and certain wind loads. The results show that the scheme proposed meets the demands of 2 m aperture telescope for pier foundation and it would provide a reference for construction of a 4 m aperture telescope.

用于空间目标偏振探测的望远镜系统偏振分析

The polarization imaging system based on large aperture ground-based adaptive telescope can acquire both intensity image and polarization image at the same time. Richer information for detecting and identifying space target can be provided by the combination of intensity and polarization. Because the polarization-maintaining design of the 1.23 m ground-based adaptive telescope is ignored, the telescope's polarization properties on propagation should be known before experiments. But it is difficult to calibrate the polarization properties of large aperture telescope. To analyze the polarization properties of the 1.23 m ground-based adaptive telescope, an analysis model based on coherent matrices and ray tracing formulas is constructed. By simulation, impact of the optical system on the accuracy of polarizing detection is found. An improved scheme to decrease the deviation of polarizing detection is given and its effectiveness is identified by the model constructed above.

自适应光学系统校正后实际分辨率评价指标

A new index,Resolved Cells Ratio( RCR),was proposed to evaluate the actual resolution of ground-based large-aperture telescope for spatial objective observation after adaptive optical system partial correcting. We discussed the physical meaning of the RCR combined with the observation instances of the 1. 23 adaptive optical telescope. The range of the application of the RCR,the error influence factors and the effect of the atmospheric dispersion on the RCR were also analyzed. The result shows that the RCR could completely reflect the correction effectiveness of the adaptive optical telescope and the physical meaning of the RCR wasintuitive. RCR can be applied to the estimation of the correction effectiveness of a telescope that can get the characterization of the wavefront. The error of the RCR mainly depend on the measurement error of the wavefront sensor. The effect of atmospheric dispersion on the RCR can be neglected.

Empirical modelling of the BLASTPol achromatic half-wave plate for precision submillimetre polarimetry

A cryogenic achromatic half-wave plate (HWP) for submillimetre astronomical polarimetry has been designed, manufactured, tested, and deployed in the Balloon-borne Large-Aperture Submillimeter Telescope for Polarimetry (BLASTPol). The design is based on the five-slab Pancharatnam recipe and it works in the wavelength range 200-600 micron, making it the broadest-band HWP built to date at (sub)millimetre wavelengths. The frequency behaviour of the HWP has been fully characterised at room and cryogenic temperatures with incoherent radiation from a polarising Fourier transform spectrometer. We develop a novel empirical model, complementary to the physical and analytical ones available in the literature, that allows us to recover the HWP Mueller matrix and phase shift as a function of frequency and extrapolated to 4K. We show that most of the HWP non-idealities can be modelled by quantifying one wavelength-dependent parameter, the position of the HWP equivalent axes, which is then readily implemented in a map-making algorithm. We derive this parameter for a range of spectral signatures of input astronomical sources relevant to BLASTPol, and provide a benchmark example of how our method can yield improved accuracy on measurements of the polarisation angle on the sky at submillimetre wavelengths.

FAINTUBVRISTANDARD STAR FIELDS

High-quality CCD-based UBVRI photometry is presented for ∼45, 000 stars distributed among 60 different fields centered on the celestial equator and at δ ≈ –50°. This photometry has been calibrated to the standard Johnson UBV and Kron-Cousins RI systems via observations of the UBVRI standard stars presented in the works of Landolt. The majority of the stars in our photometric catalog fall in the magnitude range 12 ∼< V ∼< 22 and in the color range –0.3 ∼< (B – V) ∼< 1.8. Each star averages 67 measures in each UBVRI filter from data taken on 250 different photometric nights over a period of ∼6.5 yr from two different telescopes. Our final photometric database effectively extends the UBVRI standard star network defined by Landolt to much fainter magnitudes and increases the number density of stars within pre-existing standard fields. Hence, these new, fainter standards serve as suitable calibrators for investigators who employ either small or large-aperture telescopes for their observational projects.

Recent advances in solar storm studies in China

"Solar storm" has been commonly accepted by academic community and the public as a very popular scientific term. It is a vivid description of violent ejections of a huge amount of magnetized plasma from the Sun as strong flare/CMEs, which sweep over into interplanetary space, develop, and affect our space environment. The solar storm could bring us disastrous space weather, destroy crucial technology, and cause a large-scale blackout. It is one of the natural disasters faced by modern human beings. Here we first briefly summarize the observational features of solar storms and introduce some key issues, and then we focus on major advances in observational studies. We mainly introduce the efforts made by the Chinese scientists and comment on the challenges and opportunities that they are facing. In this era when scientific breakthroughs in solar storm studies crucially depend on space-borne devices and large-aperture ground-based telescopes, the Chinese solar research community needs to develop its own major observational facilities and improve space weather forecasting abilities.

Astronomical aspects of building a system for detecting and monitoring hazardous space objects

In order to meet the practical priority of the mass detection of hazardous celestial bodies (HCBs) during the creation of a system to counteract space hazards (asteroids, comet hazards and space debris), we need clear technical requirements for the detection instruments designed (created). Specially targeted astronomical investigations into the basic properties of the HCB ensemble were conducted to specify such requirements (limitations). The paper presents these findings. As to asteroid and comet hazards, quantitative limitations on the HCB size (50 m) have been introduced and quantitative definitions of threatening and collisional HCB orbits have been proposed for the first time. It is shown that at a lead time of 30 days, it is necessary to detect HCBs at distances of about 1 AU, which corresponds to a telescope’s resolving power of V ∼ 23m. This entails the necessity to design wide-angle large-aperture telescopes. For detecting and monitoring space debris objects and meteoroids in the near-earth space at a time scale of about several days, faster instruments with smaller apertures but larger vision fields are efficient. An example is given of a basic design of a space-based system that takes into account the astronomical requirements discussed.

Analysing Kinematics of a Novel 3CPS Parallel Manipulator Based on Rodrigues Parameters

In order to adjust the poses of the segment mirrors and give the correct surface shape to a large aperture telescope, an active adjusting platform for segment mirror with a novel 3CPS parallel manipulator as core module is proposed. The platform has 6 degree-of-freedoms (DOFs) including three translational freedoms and three rotational freedoms. Its kinematics are analysed systematically. By means of the Rodrigues parameters method, the formulae for solving the inverse/forward displacement, the inverse/forward velocity, and the inverse/forward acceleration kinematics are derived. A numerical simulation of the kinematics model is then carried out combining the topological structure characteristics of the manipulator. The correctness of the kinematics model is verified by an experiment in which the pose of moving platform is measured using a photogrammetric method.