Telescope System Research Articles

Efficient fabrication of infrared antireflective microstructures on a curved Diamond-ZnS composite surface by using femtosecond Bessel-like beams.

Antireflective microstructures fabricated using femtosecond laser possess wide-ranging applicability and high stability across different spectral bands. However, due to the limited aspect ratio of the focused light field, traditional femtosecond laser manufacturing faces challenges in efficiently fabricating antireflective microstructures with high aspect ratio and small period, which are essential for antireflection, on curved surfaces. In this study, we present a robust and efficient method for fabricating high-aspect-ratio and basal surface insensitive antireflective microstructures using a spatially shaped Bessel-like beam. Based on theoretical simulation, a redesigned telescopic system is proposed to flexibly equalize the intensity of the Bessel beam along its propagation direction, facilitating the fabrication of antireflective subwavelength structures on the entire convex lens. The fabricated microstructures, featuring a width of less than 2 µm and a depth of 1 µm, enhance transmittance from 75% to 85% on Diamond-ZnS composite material (D-ZnS) surfaces. Our approach enables the creation of high aspect ratio subwavelength structures with a z-position difference exceeding 600 µm. This practical, efficient, and cost-effective method is facilitated for producing antireflective surfaces on aero-optical components utilized in aviation.

Dynamic Simulation Analysis of Truck Crane Based on ADAMS

Background: With a reduction in the weight of telescopic boom crane and an increase in its lifting capacity, the contradiction between its speed, stability and safety becomes more prominent. The telescopic arm also has flexible deformation during operation, which will cause vibration of the whole vehicle system. Therefore, in order to ensure safety, accuracy, and efficiency in the working process, it is necessary to accurately predict the dynamic characteristics of the telescopic boom load in the working process. Objective: The purpose of this study is to establish a rigid-flexible coupling dynamic model of the crane, which can accurately reflect the dynamic characteristics of the telescopic boom during its operation in the simulation test. Methods: In theory, this study analyzes the characteristics of a truck crane and simplifies it as a cantilever beam. Based on the Euler-Bernoulli beam theory, the vibration differential equation of the mobile masscantilever beam system is established. In the aspect of simulation, the three-dimensional modeling software Solidworks is used to establish the solid model of the truck telescopic boom, the finite element analysis software is used to establish the finite element model of the telescopic boom, and the modal neutral file is generated and imported into ADAMS to establish the dynamic model of the truck crane multi-level flexible telescopic boom. The dynamic simulation of the virtual prototype model of the truck telescopic boom crane is carried out in ADAMS software to obtain the dynamic characteristics of the key components of crane under specific working conditions. Results: The vibration differential equation derived in theory can be used to solve the dynamic response of the crane jib under specific conditions by MATLAB programming. In the aspect of simulation, the error fluctuation and its causes in the key components of the crane in the working state are analyzed, and the rationality of the virtual prototype model is verified. Finally, through the trajectory planning of the crane under typical working conditions, the purpose of stable control of the telescopic boom system of the truck crane is realized. Conclusion: The derived equation is universal for solving the vibration of crane jib in general cases. The rigid-flexible coupling model also provides a reference for the dynamic modeling, analysis, design, and manufacture of a multi-stage flexible telescopic boom. The findings of this study can provide a reference for related patent research and development.

A renewable power system for an off-grid sustainable telescope fueled by solar power, batteries and green hydrogen

A large portion of astronomy’s carbon footprint stems from fossil fuels supplying the power demand of astronomical observatories. Here, we explore various isolated low-carbon power system setups for the newly planned Atacama Large Aperture Submillimeter Telescope, and compare them to a business-as-usual diesel power generated system. Technologies included in the designed systems are photovoltaics, concentrated solar power, diesel generators, batteries, and hydrogen storage. We adapt the electricity system optimization model highRES to this case study and feed it with the telescope’s projected energy demand, cost assumptions for the year 2030 and site-specific capacity factors. Our results show that the lowest-cost system with LCOEs of $116/MWh majorly uses photovoltaics paired with batteries and fuel cells running on imported and on-site produced green hydrogen. Some diesel generators run for backup. This solution would reduce the telescope’s power-side carbon footprint by 95% compared to the business-as-usual case.

Large Telescope Wind Load Estimation with Gradient Segments Superposition and its Servo Control

Obtaining the wind load distribution on the telescope aperture is very important to estimate its influence and reduce the wind disturbance on the telescope system. The aperture of the radio telescope structure can be as large as 100 m and therefore, the uniform wind load on the aperture assumption is not suitable for the radio telescope with large aperture. In this paper, a gradient segments superposition method for calculating the wind load has been proposed. The proposed method has been constructed by combining two regional divisions. First, reflecting surface has been evenly divided in the altitudinal direction. Second, the reflecting surface has been divided into several uniform rings assuming that the wind load coefficient on different rings are different. For the 110 m aperture radio telescope, the wind load estimation results differ by 28%. After that, a structural dynamics model of telescope has been established and a fuzzy PID controller has been designed to reduce wind disturbance. The Root Mean Square Error of telescope pointing under wind disturbance has been reduced by 67.8%. It is suggested that the proposed wind load estimation method has lay a solid foundation for the design of the large telescope system under wind disturbance.

Calibration method and performance of a time-of-flight detector to measure absolute beam energy in proton therapy.

The beam energy is one of the most significant parameters in particle therapy since it is directly correlated to the particles' penetration depth inside the patient. Nowadays, the range accuracy is guaranteed by offline routine quality control checks mainly performed with water phantoms, 2D detectors with PMMA wedges, or multi-layer ionization chambers. The latter feature low sensitivity, slow collection time, and response dependent on external parameters, which represent limiting factors for the quality controls of beams delivered with fast energy switching modalities, as foreseen in future treatments. In this context, a device based on solid-state detectors technology, able to perform a direct and absolute beam energy measurement, is proposed as a viable alternative for quality assurance measurements and beam commissioning, paving the way for online range monitoring and treatment verification. This work follows the proof of concept of an energy monitoring system for clinical proton beams, based on Ultra Fast Silicon Detectors (featuring tenths of ps time resolution in 50μm active thickness, and single particle detection capability) and time-of-flight techniques. An upgrade of such a system is presented here, together with the description of a dedicated self-calibration method, proving that this second prototype is able to assess the mean particles energy of a monoenergetic beam without any constraint on the beam temporal structure, neither any a priori knowledge of the beam energy for the calibration of the system. A new detector geometry, consisting of sensors segmented in strips, has been designed and implemented in order to enhance the statistics of coincident protons, thus improving the accuracy of the measured time differences. The prototype was tested on the cyclotron proton beam of the Trento Protontherapy Center (TPC). In addition, a dedicated self-calibration method, exploiting the measurement of monoenergetic beams crossing the two telescope sensors for different flight distances, was introduced to remove the systematic uncertainties independently from any external reference. The novel calibration strategy was applied to the experimental data collected at TPC (Trento) and CNAO (Pavia). Deviations between measured and reference beam energies in the order of a few hundreds of keV with a maximum uncertainty of 0.5 MeV were found, in compliance with the clinically required water range accuracy of 1mm. The presented version of the telescope system, minimally perturbative of the beam, relies on a few seconds of acquisition time to achieve the required clinical accuracy and therefore represents a feasible solution for beam commission, quality assurance checks, and online beam energy monitoring.

Photonics Scanning Pentaprism System for the Integrated Inspection of Large-Aperture Telescopes.

To improve their spatial resolution and detection capabilities, future ground-based optical telescopes will have a size of 30 m, and the aperture of space telescopes will be increased to 10 m. Such large optical systems necessitate the development of large integrated testing equipment. In this study, spectrum and system alignment measurements and wavefront quality checking were performed using the sub-aperture detection method and a fiber-connected Photonics Scanning Pentaprism (PSP). First, the system was aligned using an optical truss, ensuring that the optical axis was properly positioned. Second, using a sub-aperture light beam though the entrance pupil, light spots were formed on the focal plane and transmitted to the spectrometer via fibers to obtain the corresponding spectral components. Then, by taking measurements at different system positions, a full-aperture spectrum response could be reached. Lastly, by photon-integrated interference on the focal plane, intensity interference fringes could be projected at the entrance pupil of the system. And the wavefront quality of the system could be verified by observing the fringe deformation. The measurement accuracy of the optical axis of the system is better than 2 mrad. The spectral measurement accuracy was better than 5%, and the wavefront measurement accuracy surpassed 0.1 wavelengths (1 wavelength = 633 nm). This study effectively enhanced the detection and in situ calibration capabilities of large telescope systems, ensuring that the performance requirements can be met in the design of future telescopes.

Reconfigurable coaxial single-photon LIDAR based on the SPAD array.

The single-photon avalanche diode (SPAD) array with time-to-digital converter (TDC) circuits on each pixel is an excellent candidate detector for imaging LIDAR systems. However, the low fill-factor of the SPAD array does not allow for efficient use of laser energy when directly adopted in a LIDAR system. Here, we design a reconfigurable coaxial single-photon LIDAR based on the SPAD array and diffractive optical elements (DOEs). We use the DOE and beam expander to shape the laser beam into a laser dot matrix. The total divergence angle of the DOE spot beam is strictly matched to the total field of view (FOV) angle of the SPAD array. Meanwhile, each focused beamlet is individually matched to every active area of the SPAD array detector, which increases the use of output energy about 100 times compared to the diffusion illumination system. Besides, the system uses the active area as the minimum pixel and can support sub-pixel scanning, resulting in higher resolution images. Through this coaxial structure, two different telescope systems after transceiver switching can be reconfigured for imaging targets at different distances. Based on our single-photon LIDAR system, we achieved 3D imaging of targets at 100m and 180m using two different telescope configurations.

Optofluidic zoom system with increased field of view and less chromatic aberration.

Imaging systems are widely used in many fields. However, there is an inherent compromise between field of view (FOV) and resolution. In this paper, we propose an optofluidic zoom system with increased FOV and less chromatic aberration, which can realize switching between large FOV and high resolution. The proposed system consists of a liquid prism, a zoom objective, an image sensor and image processing module, which can realize optical zoom and deflection. The proposed system achieves non-mechanical optical zoom from f = 40.5 mm to f = 84.0 mm. Besides, the angular resolution of zoom objective is up to 26"18 at f = 84.0 mm. The deflection range is ±10°, and the whole FOV of proposed system can reach up to 30.3°. The proposed system is compact and easy to machine. In addition, we reduce chromatic aberration produced by the liquid prism significantly. The proposed system can be used in monitor system, target tracking system, telescope system and so on.

Vibration rejection of phased array telescope systems via disturbance-propagation-characteristics-based feedforward control.

Vibration rejection is one of the key techniques to stabilize the line of sight (LOS) for phased array telescope systems. Conventionally, feedback control based on image sensors is mainly used to correct the tip/tilt errors caused by disturbances and to keep the LOS stable. However, it is restricted by the sampling rate and time delay of image sensors, leading to a limited closed-loop bandwidth. Disturbances in the middle and high frequencies are hard to suppress. In this paper, disturbance-propagation-characteristics-based feedforward control is proposed to overcome these problems. A theoretical imaging model of the phased array telescope is developed to analyze the LOS disruption caused by disturbance. In addition, to improve the disturbance suppression bandwidth and correction accuracy of the system, the disturbance propagation characteristics of the phased array telescope system are analyzed. Combined with the disturbance feedforward, targeted compensation is achieved for the sub-apertures. Finally, a comparative experiment is carried out based on the self-developed Fizeau phased array telescope system to verify the superiority of the proposed method.

Exit pupil quality analysis and optimization in freeform afocal telescope systems.

Afocal telescopes are often used as foreoptics to existing imaging systems to allow for application flexibility. To properly combine an afocal telescope with an existing imaging system, the exit pupil of the afocal telescope and the entrance pupil of the imaging system must be coincident. Additionally, the exit pupil of the afocal telescope must be well-formed; that is, it must be the correct size and shape to mitigate pupil-matching challenges. This work introduces processes for designing freeform afocal telescopes with an emphasis on understanding how to analyze and control the exit pupil quality of such systems. The included 3-mirror design examples demonstrate the advantages of using freeform surfaces in afocal systems and quantify the tradeoffs required to improve the exit pupil quality.

Performance of the MALTA telescope

MALTA is part of the Depleted Monolithic Active Pixel sensors designed in Tower 180 nm CMOS imaging technology. A custom telescope with six MALTA planes has been developed for test beam campaigns at SPS, CERN, with the ability to host several devices under test. The telescope system has a dedicated custom readout, online monitoring integrated into DAQ with realtime hit map, time distribution and event hit multiplicity. It hosts a dedicated fully configurable trigger system enabling to trigger on coincidence between telescope planes and timing reference from a scintillator. The excellent time resolution performance allows for fast track reconstruction, due to the possibility to retain a low hit multiplicity per event which reduces the combinatorics. This paper reviews the architecture of the system and its performance during the 2021 and 2022 test beam campaign at the SPS North Area.

High-frequency line-of-sight jitter rejection via an extended Youla-Kucera parameterization controller in segmented diffractive telescope—Theory and experiment

Line-of-sight jitter caused by mechanical vibrations and disturbances in the transmission medium seriously damages the imaging performance in telescope systems. This paper investigates the problem of high-frequency line-of-sight jitter rejection up to Nyquist frequency in bandwidth-limited control systems due to time delays. Although the piezoelectric ceramic-driven tip-tilt mirror has a wide bandwidth, Large time delays caused by the image sensor for high-quality imaging severely restrict the control system’s closed-loop bandwidth. The disturbance cannot be sufficiently rejected, especially outside the bandwidth. Based on the Small Gain Theorem, the gain factor and time-delay factor as an extra flexible budget in the Youla-Kucera (Y-K) parameterization are derived from decreasing the waterbed effect, improving the closed-loop system stability. Thus, this proposed Y-K method accommodates disturbance rejection frequency inside and outside control bandwidth, which can be extended to the Nyquist frequency. Simulation analyses and Experimental results have been effectively verified in the line-of-sight stabilization control of the segmented lightweight large-scaled diffractive telescope (SLLDT) system.

Astreaks: astrometry of NEOs with trailed background stars

ABSTRACT The detection and accurate astrometry of fast-moving near-Earth objects (NEOs) has been a challenge for the follow-up community. Their fast apparent motion results in streaks in sidereal images, thus affecting the telescope’s limiting magnitude and astrometric accuracy. A widely adopted technique to mitigate trailing losses is non-sidereal tracking, which transfers the streaking to background reference stars. However, no existing publicly available astrometry software is configured to detect such elongated stars. We present Astreaks, a streaking source detection algorithm, to obtain accurate astrometry of NEOs in non-sidereal data. We validate the astrometric accuracy of Astreaks on 371 non-sidereally tracked images for 115 NEOs with two instrument set-ups of the GROWTH-India Telescope. The observed NEOs had V-band magnitude in the range [15, 22] with proper motion up to 140 arcsec min−1, thus resulting in stellar streaks as high as 6.5 arcmin (582 pixels) in our data. Our method obtained astrometric solutions for all images with 100 per cent success rate. The standard deviation in observed-minus-computed (O–C) residuals is 0.52 arcsec with O–C residuals <2 arcsec (<1 arcsec) for 98.4 per cent (84.4 per cent) of our measurements. These are appreciable, given the pixel scale of ∼0.3 and ∼0.7 arcsec of our two instrument set-ups. This demonstrates that our modular and fully automated algorithm helps improve the telescope system’s limiting magnitude without compromising astrometric accuracy by enabling non-sidereal tracking on the target. This will help the NEO follow-up community cope with the accelerated discovery rates and improved sensitivity of the next-generation NEO surveys. Astreaks has been made available to the community under an open-source license.

ASPHERIC TWO-MIRROR TELESCOPES OF NANOSATELLITES FOR REMOTE EARTH SENSING AND SEARCH OF MINERALS

The optical system is one of the important components of any space satellite used to observe the Earth's surface or astronomical objects. Due to the small overall size of nanosatellites, lens objectives with the relatively short focal length are often used. The latter provides the sufficiently wide field of view, but limits the spatial resolution of obtained images. In addition, to address various problems in agriculture and geodesy, it is important to obtain images of the earth's surface in different spectral ranges. This fact prevents the application of widespread commercial photographic lenses corrected for the visible spectral range. The article presents the results of the automated parametric synthesis of centered and decentered aspheric optical systems of mirror telescopes based on the Ritchie-Chretien scheme. The obtained optical systems have the focal length of 547 mm, the square entrance aperture of 80×80 mm, and the axial length that does not exceed the size of two CubeSat units. The angular field of view of the telescopes, which is equal to 0.7° in diagonal, enables to apply modern matrix image sensors having a diagonal of the sensitive area up to 6.7 mm. For an axial beam, 90% of the radiation energy falls into a square area of the image with a side of 2.5 μm. The maximum value of relative distortion does not exceed 0.4 %. The considered mirror systems do not have chromatic aberrations, which makes it possible to obtain high-quality images not only in the visible spectral range, but also in several infrared sub-bands. The given results of the aberration analysis testify to the high image quality achieved in both variants. The presented optical systems can observe a rectangular area of the Earth's surface with the diagonal size of about 7.9 km from the satellite’s track height of 650 km. When using a multi-element image detectors with the pixel size of 3 μm, the geometric projection of one pixel on the Earth's surface will be equal to 3.6 m.

Co-phase errors sensing method for Golay3 telescope system via a transfer network.

Optical sparse-aperture systems face severe challenges, including detecting and correcting co-phase errors. In this study, a search framework based on fine tuning a pre-trained network is proposed to analyze the co-phase errors of a Golay3 telescope system. Based on this, an error compensation control system is established. First, a hash-like binary code is created by fine-tuning the pre-trained model. Secondly, a pre-trained network is used to extract the deep features of the image, and an index database is built between the image features and the corresponding co-phase error values. Finally, the Top 1-ranked features and corresponding co-phase error values are returned through the hash-like binary code hierarchical deep search database to provide driving data for the error correction system. Numerical simulations and experimental results verify the method's validity. The experimental results show that the correction system works well when the dynamic piston is [-5,5]λ, and the tilt error range is [-15,15]µr a d. Compared with existing detection methods, this method does not require additional optical components, has a high correction accuracy, and requires a short training time. Furthermore, it can be used to detect piston and tilt errors simultaneously.

Модернизация системы обеспечения устойчивости железнодорожного крана КЖ-971 и оценка её эффективности

The weight of the load hanging on the boom of a railroad hydraulic crane KZH-971 creates a load moment that bends the crane slewing ring. To partially balance the load moment, a stationary counterweight is installed on the crane, rigidly fixed on a slewing platform. With an increase in the boom departure, the unbalanced part of the load moment and tensions in the slewing ring increases. In this article, to ensure a constant value of the unbalanced part of the load moment and reduce bending tensions, it is proposed to install a counterweight on the railroad crane with a telescoping system and the ability to rotate about the vertical axis for a work in cramped conditions. A strength analysis of the slewing ring for the change in maximum tensions from the use of a movable counterweight was carried out. An adaptive control system for the position of a movable counterweight has been modeled, with the help of which it will be possible to develop a device for convenient control from the crane operator’s cabin in the future. The advantages of using a movable counter-weight with the possibility of rotation relative the vertical axis are shown when performing loading and repair work in cramped conditions. The results of the strength analysis of the slewing ring with the location of loads in the main working positions are summarized.

Fault Analysis and Diagnosis of Downhole Traction Robot Hydraulic System

Fault diagnosis of downhole traction robot has characteristics of special mechanical structure, complicated working condition and lack of research data. In this paper, a method of fault analysis and diagnosis of tractor hydraulic system based on model is presented. The failure mode and mechanism of key components in telescopic hydraulic system are analyzed. The fault diagnosis of hydraulic system is proposed based on the mathematical model of hydraulic component. Based on AMESim, the fault model of hydraulic system is established, and the diagnosis of single fault and multi-fault are simulated, which can collect the fault data and the specific diagnosis process. To carry forward the engineering application, the simulated internal leakage system in cylinder is set up and schemes of fault diagnosis are carried out, which prove that the diagnosis is consistent with theoretical analysis and simulation. The research on fault analysis and diagnosis of the downhole traction robot hydraulic system not only lays theoretical basis for the tractor fault detection, but also provides guidance for the construction and implementation of the diagnostic system.

Active lateral support system for a thin 1-meter meniscus mirror with virtual fixed points

This publication presents an active lateral support system for the thin 1-m meniscus mirror of a Ritchey-Chrétien telescope system. The goal is to keep the mirror at its position under varying external influences, such as gravity and temperature, therefore maintaining the alignment and optical image quality. To achieve this, the lateral support consists of eight actuators, based on stepper motors with gearboxes, with local force measurement and three laser triangulation sensors to measure the mirror’s lateral position. A cascaded control structure with local force feedback in the inner loop and position feedback in the outer loop is proposed. In the outer loop, three single-input single-output PI-controllers are implemented to maintain mirror position in the three lateral degrees of freedom. The developed system is able to position the mirror with root mean square errors of 0.27 and 0.18 μm in translational directions and 5.1 μrad in the rotational direction over the operational altitude range with a slewing speed of 0.2 deg / s.

The results of the use of the telescopic intramedullary system in the surgical treatment of patients with osteogenesis imperfecta types I and III

Background. The main orthopedic manifestation of osteogenesis imperfecta is multiple fractures. In severe disease, frequent fractures lead to malunion and deformity, which increases the risk of refracture. Surgical treatment of children with osteogenesis imperfecta is aimed at reducing the risk of complications and improving the quality of life of the child. The Fassier-Duval telescopic intramedullary system has taken the leading place among the growing metal fixators. In this study, we conduct a comparative analysis of the results of a longitudinal study between patients with osteogenesis imperfecta types I and III, as well as an assessment of motor activity.
 Aim. To evaluate the efficiency of using the telescopic intramedullary system depending on the type of osteogenesis imperfecta.
 Materials and methods. A prospective analysis of surgical treatment of 20 children with types I and III was carried out. Group I included 8 patients with type I NO, group II included 12 with type III. The average age of patients was 8.2 years. Surgical treatment was carried out on the basis of the neuroorthopedic department with orthopedics of the National Medical Research Center for Children's Health. A total of 48 intramedullary telescopic pins were installed. The average period of postoperative dynamic follow-up was 42 months. The analysis of the results of surgical treatment was carried out according to the following criteria: the frequency of migrations of metal structures, the formation of bone deformities, the number of revisions, as well as the number of bone fractures with an installed metal fixator. Evaluation of the results of motor activity was carried out using two scales: Gillette Functional Assesment Questionnaire (Gillette FAQ) and HofferBullock.
 Results. There were no statistical differences in the number of complications in the two groups. Fractures among patients with type I occurred more often than in patients with type III by 19.3%. The frequency of migrations in the I study group was 7.1% (1 segment), in the II group 35.3% (12 segments). The formation of deformation was the main factor in the revision intervention, which in our case amounted to 83.3%. In the group of patients with type I, the number of repeated operations was 7.1% (1 segment in 1 patient), in the group of patients with type III 17.6% (6 segments in 4 patients). All patients in the postoperative period had II or I level of motor capabilities on the HofferBullock scale. According to the Gillette FAQ scale in the postoperative period, the subjects showed a result above 4 points.
 Conclusion. The Fassier-Duval telescopic rod is a modern and reliable metal fixator. Despite the absence of statistical differences in the two study groups (p-value20.005), there was an increase in the tendency to complications in severe course with NO. Correction of varus deformation when restoring normal values of DN125 and HEA within 2538 is the prevention of the re-formation of the truth of Coxa Vara. The motor activity of children with severe course did not statistically differ from children with mild course (p-value20.005) in the postoperative period with an average follow-up period of 42 months, regardless of the initial low motor capabilities in children with type III.

Fiber-Connected Wavefront-Sensing System for Large Segmented Space Telescopes

Fiber-Connected Wavefront-Sensing System for Large Segmented Space Telescopes