Telescope Structure Research Articles

The Multi-band Survey Telescope at Zhongshan Station, Antarctica

ABSTRACTThe Antarctic Plateau is considered to be the best ground-based astronomical site on Earth. Compared with other middle latitude observatories, the telescopes located in Antarctica have unique advantages in seeing a large fraction of clear nights, continuous observing window in the polar night, and so on. China has operated several generations of telescopes in Antarctica, but has not yet achieved multicolour simultaneous observation with tracking. Multi-band Survey Telescope (MST) is the first multicolour simultaneous survey telescope in Antarctica. It adopts a Newtonian telescope structure which is different from other Antarctic telescopes and is matched with a new alignment scheme suitable for the harsh environment of Antarctica. In addition, MST is equipped with a defrosting indium tin oxide (ITO) window and a high-precision equatorial mount. This paper introduces the optical design, mechanical structure, and analysis of the actual operation of MST in Antarctica. Since March 2022, MST has been carrying out the observation normally in Zhongshan Station, and the operation of MST has provided a new experience for the follow-up design and installation of Antarctic telescopes. We plan to further optimize the design and manufacture of MST, and develop it as a standard model of small-aperture Antarctic telescopes for space debris observations and time-domain surveys.

Comparison of the use of intramedullary telescopic system and titanium elastic rods in children with osteogenesis imperfecta I and III types

Comparison of the use of intramedullary telescopic system and titanium elastic rods in children with osteogenesis imperfecta I and III types

Теоретическое обоснование параметров телескопического водовыпускного сооружения с круглоцилиндрическим поплавком

The purpose of the research is to improve the design of a water outlet, to calculate a telescopic outlet with a round-cylindrical float and determining the diameter of the movable box float with the given parameters, which should ensure the reliability of its static position in all possible hydraulic modes of operation as a spillway with a round-cylindrical cap with a movable position of the crest, depending from the water level in the receiving main canal. The article presents the developed design of the outlet structure of the overflow outlet structure of the telescopic type, which has a simple design, reliability in operation, structural design with minimal hydraulic losses. The paper shows the results of theoretical studies of the proposed design of a telescopic outlet structure, three variants have been considered for the operation of the movable box, from the above calculations, the defining diameter of the float is the mode with water overflowing through it when the maximum flow rate of the pipeline is supplied. The following calculated diameters of the float were obtained; dfl o = 0.1279 m, dfl = 0. 0808 m and dfl t = 0.315m. It is possible to use standard PVC pipes, the nearest larger standard outer diameter is d = 0.355 mm. considering the simplicity of the design of the telescopic type water outlet, it can be manufactured in the conditions of mechanical workshops of construction organizations.

Analysis of physical mechanism of beam crosstalk in semiconductor laser array spectral-beam-combined system

In spectral beam combining systems based on a grating-external cavity, due to some factors such as the “smile” effect of the semiconductor laser array and the error of the optical components in the external cavity, the beam from one emitter transmits into the external cavity and then can return to other emitters, thereby forming beam crosstalk between the two emitters. In this work, in order to investigate the physical mechanism of beam crosstalk and the influence of beam crosstalk on beam properties such as locked spectra and beam combining efficiency, based on the optical feedback semiconductor rate equation, the beam modes that can stably oscillate in the coupling cavity are derived, and the coupling cavity oscillating model is built. With the consideration of the mode competition mechanism in the coupling cavity, the effects of different crosstalk between two emitters with different intervals on the locked spectra are analyzed in detail. The results show that crosstalk leads to the shift of the peak of locked spectrum and the generation of sub-peak. The crosstalk between two closer emitters has a more serious influence on the beam spectrum structure, combined beam spot, and combining efficiency. The combining efficiencies influencing the 1<sup>st</sup>, 2<sup>nd</sup> and 3<sup>rd</sup> crosstalk are 45.5%, 50.2%, and 63.8%, respectively (When there is no crosstalk, the efficiency is 80.1%). Finally, the results of the theoretical analysis are verified experimentally, and the experimentally observed spectra under the influence of crosstalk show phenomena such as peak degradation, peak shift, edge burrs, and side lobes in spectra, which are consistent with the theoretical predictions. Moreover, according to the simulation results and experimental observations, it is found that the crosstalk can be suppressed to a certain extent by increasing the spacing between emitters, and the Galileo telescope system is suggested to suppress crosstalk and optimize the spectral structure and beam combining efficiency. Compared with the Kepler telescope structure, the Galileo telescope does not have a real focal point, which can prevent the local power from being too high, thereby damaging the optical components.

Instability load analysis of a telescopic boom for an all-terrain crane

Abstract. The instability load for the telescopic boom of an all-terrain crane is investigated in this paper. Combined with structural characteristics of the telescopic boom, each boom section is divided into several substructures, and the fixed-body coordinate system of each substructure is established based on the co-rotational method. A 3D Euler–Bernoulli eccentric beam element of the telescopic boom is derived. On the premise of considering the discretization of gravity and wind load, internal degrees of freedom of the substructure are condensed to the boundary nodes, forming a geometrical nonlinear super element. According to the nesting mode of the telescopic boom, a constraint way is established. The unstressed original length of the guy rope is calculated with a given preload so as to establish the equilibrium equations of the boom system with the external force of the guy rope and the corresponding tangent stiffness matrix. Regarding the above work, a new method for calculating the structural equilibrium path and instability load of telescopic boom structure is presented by solving the governing equations in a differential form. Finally, the method is validated by examples with different features.

Adaptive optics performance of a simulated coronagraph instrument on a large, segmented space telescope in steady state

Directly imaging Earth-like exoplanets (``exoEarths'') with a coronagraph instrument on a space telescope requires a stable wavefront with optical path differences limited to tens of picometers RMS during exposure times of a few hours. While the structural dynamics of a segmented mirror can be directly stabilized with telescope metrology, another possibility is to use a closed-loop wavefront sensing and control system in the coronagraph instrument that operates during the science exposures to actively correct the wavefront and relax the constraints on the stability of the telescope. In this paper, we present simulations of the temporal filtering provided using the example of LUVOIR-A, a 15~m segmented telescope concept. Assuming steady-state aberrations based on a finite element model of the telescope structure, we (1)~optimize the system to minimize the wavefront residuals, (2)~ use an end-to-end numerical propagation model to estimate the residual starlight intensity at the science detector, and (3)~predict the number of exoEarth candidates detected during the mission. We show that telescope dynamic errors of 100~pm~RMS can be reduced down to 30~pm~RMS with a magnitude 0 star, improving the contrast performance by a factor of 15. In scenarios where vibration frequencies are too fast for a system that uses natural guide stars, laser sources can increase the flux at the wavefront sensor to increase the servo-loop frequency and mitigate the high temporal frequency wavefront errors. For example, an external laser with an effective magnitude of -4 allows the wavefront from a telescope with 100~pm~RMS dynamic errors and strong vibrations as fast as 16~Hz to be stabilized with residual errors of 10~pm~RMS thereby increasing the number of detected planets by at least a factor of 4.

Regulation of Telescopic Water Intake Operations

Abstract Telescopic water intake structures play an important role in a water management system. The article is devoted to the improvement of telescopic water intake structures and the development of a solution for regulating their operation. Different types of water intakes are analyzed, and their shortcomings are identified. The structures of known telescopic water intakes are reviewed, and their operating principles are analyzed. It has been determined that the design of existing telescopic water intake structures lacks a device for stopping the operation of the intake of water. A structural solution for stopping and regulating the operation of a telescopic water intake is proposed. The construction of an additional ballast pontoon to be welded to the first section of the telescopic pipeline is proposed in order to regulate and stop the operation of the water intake. A methodology for calculating and designing an additional ballast pontoon for a telescopic water intake has been developed, and a specific example for its implementation has been provided. Based on the results of the research, the main parameters of the additional ballast pontoon structure have been established, and the methodology for its calculations has been developed.

Design and application of a spherical aberration free continuous zoom liquid-filled micro-cylindrical lenses system

A zoom system named liquid-filled micro-cylindrical lenses integrating a capillary and a biconvex micro-cylindrical lens in a polydimethylsiloxane (PDMS) substrate is designed, which can achieve continuous changed focal length from 2.675 to 9.012 mm by injecting variable concentrations of glycerol aqueous solution into the capillary. The aberration fan diagrams, root mean square spot radius, peak-to-valley wavefront aberration, and modulation transfer function curves at different zoom configurations of the liquid-filled micro-cylindrical lenses are all analyzed, showing good imaging quality over the whole focal length range. And an anamorphic zoom system for uniform collimated beam is designed putting such two PDMS substrates similar as the Kepler telescope structure. The anamorphic system can realize the zoom shaping function with 1:2 to 2:1 aspect ratio beam conversion without machine movement along optical axis and with no significant aberration. The introduced zoom system is characterized by high image quality, small volume, and a simple and stable structure, providing a design idea for cylindrical lenses with variable focal length.

Dynamics and Control of a Reconfigurable Multi-Arm Robot for In-Orbit Assembly

In this paper, a passivity-based controller is proposed for a reconfigurable multi-arm system, which is employed for in-orbit assembly. The reconfigurable system is composed of multiple anthropomorphic arms which can be connected to a torso or operate independently. The proposed control is applicable for all the morphologies of the multi-arm system while performing several operations required for the assembly task, such as walking on a telescope structure through dedicated mechanical interfaces. The constrained dynamics is exploited to derive a unified joint actuation control law for all the considered operations and morphologies. A Co-simulation framework was developed to simulate the operations for control prototyping, and simulation results prove the effectiveness of the proposed unified controller.

Method and portable bench for tests of the laser optical calibration system components for the Baikal-GVD underwater neutrino Cherenkov telescope

The Large-scale deep underwater Cherenkov neutrino telescopes like Baikal-GVD, ANTARES or KM3NeT, require calibration and testing methods of their optical modules. These methods usually include laser-based systems which allow us to check the telescope responses to the light and for real-time monitoring of the optical parameters of water such as absorption and scattering lengths, which show seasonal changes in natural reservoirs of water. We will present a testing method of a laser calibration system and a set of dedicated tools developed for Baikal-GVD, which includes a specially designed and built, compact, portable, and reconfigurable scanning station. This station is adapted to perform fast quality tests of the underwater laser sets just before their deployment in the telescope structure, even on ice, without a darkroom. The testing procedure includes the energy stability test of the laser device, 3D scan of the light emission from the diffuser and attenuation test of the optical elements of the laser calibration system. The test bench consists primarily of an automatic mechanical scanner with a movable Si detector, beam splitter with a reference Si detector and, optionally, Q-switched diode-pumped solid-state laser used for laboratory scans of the diffusers. The presented test bench enables a 3D scan of the light emission from diffusers, which are designed to obtain the isotropic distribution of photons around the point of emission. The results of the measurement can be easily shown on a 3D plot immediately after the test and may be also implemented to a dedicated program simulating photons propagation in water, which allows us to check the quality of the diffuser in the scale of the Baikal-GVD telescope geometry.

A coarse-to-fine detection and localization method for multiple human subjects under through-wall condition using a new telescopic SIMO UWB radar

Radar-based life detecting technology has been researched more and more in recent years and applied widely in several areas. However, few researches on multi-subjects detecting and locating have been reported. Even these researches are mainly based on imaging technology with two shortcomings, namely the interference of ghost and difficult to focus the target’s position. A new coarse-to-fine approach for detecting and locating of human targets using single-input multiple-output (SIMO) radar under penetration conditions is proposed. The approach realized automatic recognition and localization of human subjects without any prior information, such as target count. Firstly, an improved censored mean level detector constant false alarm rate (CMLD-CFAR) by adding a feature to distinguish vital sign from background is proposed in each inner-channel to coarsely determine the targets’ time-of-arrival (TOA) distances. Secondly, the real targets count is finely determined by calculating the inter-channel Pearson correlation coefficient of signals from different channels. Then, a back projection (BP) is presented to calculate the targets’ 2-D locations. In the experiments of single and multi-target locating, all targets were identified correctly and localized near their actual positions with errors within 0.3 m. With the distinctive telescopic structure of the proposed radar, the azimuth resolution of locating is adjustable. Compare to current radar system for radar multi-target locating, like multiple-input multiple-output (MIMO) system, the proposed system can improve accuracy and automation of localization while decline the cost and complexity. It has potential to promote practical application of locating trapped human targets in post-disaster rescue and intelligent homeware fields.

Design and analysis of a new frame-foot wall-climbing robot

This paper designs and develops a new type of frame-foot wall-climbing robot structure. According to the bionic principle, a new parallel telescopic leg structure is proposed, and the 3D design of the overall structure of the wall-climbing robot is completed. Secondly, the kinematics analysis of the robot is carried out, and the forward and inverse solution models of the leg structure position are completed to verify the feasibility of the leg structure stability. Based on the polynomial motion equations, the robot motion planning and gait design are established, and the speed and acceleration change graphs of the leg structure slider are obtained, which avoids the rigid impact between the parts, and realizes the alternate adsorption and continuous movement of the robot legs, which the rationality of the legs structure design and the stability of the movement are verified. Through simulation and experimental results, it is shown that during the robot’s movement, the leg structure can adjust the step distance and step height according to obstacles, so as to achieve the expected obstacle crossing goal. The leg structure is adjusted according to the working environment to ensure that the fuselage and the working surface are always kept parallel to improve the stability of the overall structure.

From main axes control to flexible body control of large telescope structures

AbstractAstronomers have to point their telescopes with extreme high precision to their targets on the sky. The early craftsmen, which built their telescope mounts, were masters in mechanics and developed sophisticated axis mechanisms based on clockwork motors for the hour angle. The situation changed with the growth of the size of the optical telescopes, the upcoming of large radio telescopes, the related transition to elevation over azimuth mounts and the introduction of electrical main axes drives. The new telescopes were equipped with gears of high transmission ratios, and the dynamics of the motor control was limited by mechanical resonances between the rotors of the motors and the mass of the telescope structure. Early layout tools for the controllers were lumped mass models for the telescope structure including gear stiffnesses and inertias of rotors and brakes, with the free rotor and locked rotor frequencies as critical characteristics influencing the servo loop performance. Nowadays, static and dynamic analysis is performed with the help of finite element models, and the axes controllers are optimized with end‐to‐end models. The emergence of large radio telescopes initiated the development of additional compensation methods for environmental influences as temperature and wind on the shape of the reflectors and their pointing to the sky. Additional active elements on the telescope as surface actuators and subreflector positioners, and additional state sensors on the structure allow the identification and compensation of structural deformations. The method is called flexible body control (FBC). The increasing size of the optical telescopes initiated the development of new mirror technologies as thin meniscus or segmented mirrors in sizes not feasible with the passive supported thick meniscus mirrors. These mirrors need active elements as shape actuators, segment positioners, and wavefront and edge sensors. The method is called active optics (AcO). Astronomical observations in the visible are disturbed by atmospheric blur, and the operability is depending of the active compensation of that blur, based on a fast wavefront sensor analyzing an artificial star and an additional fast wavefront corrector. The method is called adaptive optics (AdO). The following text gives an overview on the historic development of telescope control systems from the viewpoint of the telescope mount and its axes control systems, finally culminating in FBC applications. Actual examples are the large millimeter telescope LMT/GTM in Mexico, the advanced technology solar telescope DKIST in Hawaii, and the airborne telescope of SOFIA, the Stratospheric Observatory for Infrared Astronomy with its base in Palmdale, California.

A Pneumatically Driven, Disposable, Soft Robotic Gripper Equipped With Multi-Stage, Retractable, Telescopic Fingers

Robots use their end-effectors to grasp and manipulate objects in unstructured and dynamic environments. Robot hands and grippers can vary from rigid and complex designs to soft, inflatable, and lightweight structures. In this paper, we focus on the modeling and development of a pneumatically driven soft robotic gripper with retractable telescopic fingers and finger bases with abduction / adduction capabilities. Both the main fingers and the base actuators use a pre-folded, telescopic structure facilitating passive retraction. The efficiency of the proposed device is experimentally validated through different types of experiments: i) grasping experiments that involve different everyday objects ranging from household objects and fragile items to medical waste and consumables, ii) force exertion experiments that capture the maximum forces that can be exerted by the proposed device when utilizing the different actuators of the gripper, and iii) grasp resistance experiments that focus on the effect of the inflatable structure on resisting environmental uncertainties and disturbances. The proposed gripper is able to grasp a plethora of objects, and can exert more than 14 N of grasping force. The design is so low-cost and modular that the soft fingers and palm pad of the gripper can be used in a disposable manner, facilitating the execution of specialized tasks (e.g., grasping in contaminated environments, handling of medical waste, etc). When it is not inflated, the gripper profile is thin and compact to facilitate storage.

Augmented reality enabled Galilean sighting system with an adjustable reticle.

A sighting system based on the Galileo telescope structure generally suffers from the lack of a reticle, which poses great challenges to target aiming. In this work, a hybrid Galilean sighting system integrated with an augmented reality (AR) component is proposed, which produces an image of the reticle to serve as a reticle. The depth of the reticle can be adjusted flexibly to superpose with the image of the observed object. The designed system features a fourfold magnification, a large modulation transfer function (MTF)>0.3 at 40 lp/mm, and a small distortion less than 0.3% in the full field of view. The superb imaging performance combined with the targeting function of the AR reticle renders the proposed design a powerful tool in the applications of target tracking.

Simultaneous estimation of segmented telescope phasing errors and non-common path aberrations from adaptive-optics-corrected images

ABSTRACT We investigate the focal plane wavefront sensing technique, known as Phase Diversity, at the scientific focal plane of a segmented mirror telescope with an adaptive optics (AO) system. We specifically consider an optical system imaging a point source in the context of (i) an artificial source within the telescope structure and (ii) from AO-corrected images of a bright star. From our simulations, we reliably disentangle segmented telescope phasing errors from non-common path aberrations (NCPA) for both a theoretical source and on-sky, AO-corrected images where we have simulated the Keck/NIRC2 system. This quantification from on-sky images is appealing, as it is sensitive to the cumulative wavefront perturbations of the entire optical train; disentanglement of phasing errors and NCPA is therefore critical, where any potential correction to the primary mirror from an estimate must contain minimal NCPA contributions. Our estimates require a 1-min sequence of short-exposure, AO-corrected images; by exploiting a slight modification to the AO-loop, we find that 75 defocused images produce reliable estimates. We demonstrate a correction from our estimates to the primary and deformable mirror results in a wavefront error reduction of up to 67 per cent and 65 per cent for phasing errors and NCPA, respectively. If the segment phasing errors on the Keck primary are of the order of ∼130 nm RMS, we show we can improve the H-band Strehl ratio by up to 10 per cent by using our algorithm. We conclude our technique works well to estimate NCPA alone from on-sky images, suggesting it is a promising method for any AO-system.

Millimetron microvibration analysis at low frequency range

This paper presents the results of Millimetron microvibration analysis at low frequencies. Millimetron telescope structure behavior was studied in order to predict its central mirror response from microvibration disturbance caused by mechanical cryocoolers. The results contain the most significant values of acceleration which appeared on the mirror surface as well as rotational deflections which affect the telescope optical axis stability. To make it possible the microvibration analysis technique was derived from the theoretical aspects and other researches results. This technique was adapted to Millimetron microvibration analysis using its finite-element model and taking into account several assumptions which were also discussed at this paper.

On the mathematical modeling for optimal selecting of calibers of conductors in DC radial distribution networks: An MINLP approach

This paper addresses the problem of optimal conductor selection in direct current (DC) distribution networks with radial topology. A nonlinear mixed-integer programming model (MINLP) is developed through a branch-to-node incidence matrix. An important contribution is that the proposed MINLP model integrates a set of constraints related to the telescopic structure of the network, which allows reducing installation costs. The proposed model also includes a time-domain dependency that helps analyze the DC network under different load conditions, including renewable generation and battery energy storage systems, and different voltage regulation operative consigns. The objective function of the proposed model is made up of the total investment in conductors and the total cost of energy losses in one year of operation. These components of the objective function show multi-objective behavior. For this reason, different simulation scenarios are performed to identify their effects on the final grid configuration. An illustrative 10-nodes medium-voltage DC grid with 9 lines is used to carry out all the simulations through the General Algebraic Modeling System known as GAMS.

Analysis of the Unconcentrated Background of the EPIC pn Camera on Board XMM-Newton

Abstract Our understanding of the background of the EPIC/pn camera on board XMM-Newton is incomplete. This affects the study of extended sources and can influence the predictions of the expected background of future X-ray missions, such as the Advanced Telescope for High Energy Astrophysics (ATHENA). Here we provide new results based on the analysis of the largest data set ever used. We focus on the unconcentrated component of the EPIC/pn background, supposedly related to cosmic rays interacting with detector and telescope structures. We show that the so-called out field-of-view region of the pn detector is actually exposed to the sky. After carefully cleaning from the sky contamination, the unconcentrated background measured in the out field-of-view region does not show significant spatial variations, and its time behavior is anticorrelated with the solar cycle. We find a very tight linear correlation between unconcentrated backgrounds detected in the EPIC/pn and EPIC/MOS2 cameras. This relationship permits the correct evaluation of the pn unconcentrated background of each exposure on the basis of MOS2 data, avoiding the use of the contaminated out field-of-view region of the pn, as done in standard techniques. We find a tight linear correlation between the pn unconcentrated background and the proton flux in the 630–970 MeV energy band, as measured by the EPHIN instrument on board SOHO. Through this relationship, we quantify the contribution of cosmic-ray interaction to the pn unconcentrated background. This reveals a second source that contributes to the pn unconcentrated background for a significant fraction (30%–70%). This agent does not depend on the solar cycle or vary with time and is roughly isotropic. After having ruled out several candidates, we find that the hard X-ray photons of the cosmic X-ray background satisfy all known properties of the constant component. Our findings provide an important observational confirmation of simulation results on ATHENA and suggest that a high-energy particle monitor could contribute decisively to the reproducibility of the background for both experiments on ATHENA.

The Simons Observatory: modeling optical systematics in the Large Aperture Telescope.

We present geometrical and physical optics simulation results for the Simons Observatory Large Aperture Telescope. This work was developed as part of the general design process for the telescope, allowing us to evaluate the impact of various design choices on performance metrics and potential systematic effects. The primary goal of the simulations was to evaluate the final design of the reflectors and the cold optics that are now being built. We describe nonsequential ray tracing used to inform the design of the cold optics, including absorbers internal to each optics tube. We discuss ray tracing simulations of the telescope structure that allow us to determine geometries that minimize detector loading and mitigate spurious near-field effects that have not been resolved by the internal baffling. We also describe physical optics simulations, performed over a range of frequencies and field locations, that produce estimates of monochromatic far-field beam patterns, which in turn are used to gauge general optical performance. Finally, we describe simulations that shed light on beam sidelobes from panel gap diffraction.