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15 pages, 8416 KiB

Open AccessArticle

Interference Measurements Across Vacuum and Atmospheric Environments for Characterization of Space-Borne Telescope

by Yi-Kai Huang and Cheng-Huan Chen

Photonics 2024, 11(12), 1105; https://doi.org/10.3390/photonics11121105 - 22 Nov 2024

Viewed by 856

Abstract

A space-borne telescope is used for Earth observation at about 500 km above sea level in the thermosphere where the air density is very low and the temperature increases significantly during daytime. If the telescopes are aligned and characterized on the ground with [...] Read more.

A space-borne telescope is used for Earth observation at about 500 km above sea level in the thermosphere where the air density is very low and the temperature increases significantly during daytime. If the telescopes are aligned and characterized on the ground with standard temperature and pressure (STP) conditions, different from that of the thermosphere, their performance could drift during their mission. Therefore, they are usually placed in a thermal vacuum chamber during ground testing in order to verify the system can perform well and withstand the harsh environment such as a high vacuum level and large temperature variations before being launched. Nevertheless, it remains a challenge to build up an in situ optical measurement system for a large aperture telescope in a thermal vacuum chamber due to the finite internal space of the chamber, limited aperture size of the vacuum view port and thermal dissipation problem of the measuring instruments. In this paper, a novel architecture of an interferometer whose light path travels across a vacuum chamber and an atmospheric environment has been proposed to resolve all of these technical issues. The major feature of the architecture is the diverger lens being located within the vacuum chamber, leaving the rest of the interferometer outside. The variation of the interference fringe due to the relocation of the diverger lens has been investigated with optical simulations and the solutions for compensation have also been proposed. Together with a specific alignment procedure for the proposed architecture, the interferogram has been successfully acquired from a prototype testbed. Full article

(This article belongs to the Special Issue Optical Systems for Astronomy)

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14 pages, 21051 KiB

Open AccessArticle

Ghost Fringe Suppression by Modifying the f-Number of the Diverger Lens for the Interferometric Measurement of Catadioptric Telescopes

by Yi-Kai Huang and Cheng-Huan Chen

Photonics 2024, 11(5), 453; https://doi.org/10.3390/photonics11050453 - 11 May 2024

Viewed by 1739

Abstract

A high-precision catadioptric telescope such as a space-borne telescope is usually tested with interferometer to check the optical quality in assembly. The coarse and fine alignment of the telescope are mainly based on the information from the coordinate measuring machine and the fringe [...] Read more.

A high-precision catadioptric telescope such as a space-borne telescope is usually tested with interferometer to check the optical quality in assembly. The coarse and fine alignment of the telescope are mainly based on the information from the coordinate measuring machine and the fringe pattern of the interferometer, respectively. In addition, further fine-tuning can be achieved according to the variation in wavefront error and Zernike data. The issue is that the vast majority of the catadioptric telescopes contain plural lens surfaces which could produce unwanted ghost fringes, disturbing the wavefront measurement. Technically, off-axis installation to shift away ghost fringes from central interferogram could be acceptable in some cases. Nevertheless, in this paper, the source of ghost fringe in interferometric measurement for catadioptric telescopes is investigated with light path simulation, and a solution of reducing the f-number of the diverger lens is proposed to eliminate the ghost fringe disturbance. Both simulation and experimental results verify the effectiveness of the proposed concept. Full article

(This article belongs to the Special Issue Optical Systems for Astronomy)

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11 pages, 3555 KiB

Open AccessArticle

Control of the Optical Wavefront in Phase and Amplitude by a Single LC-SLM in a Stellar Coronagraph Aiming for Direct Exoplanet Imaging

by Andrey Yudaev, Alla Venkstern, Irina Shulgina, Alexander Kiselev, Alexander Tavrov and Oleg Korablev

Photonics 2024, 11(4), 300; https://doi.org/10.3390/photonics11040300 - 26 Mar 2024

Viewed by 1377

Abstract

This article presents a novel approach to actively compensate wavefront errors in both phase and amplitude using a Liquid Crystal Spatial Light Modulator (LC-SLM) for direct exoplanet imaging. This method involves controlling the wavefront to address challenges posed by stellar coronagraphy. Experimental results [...] Read more.

This article presents a novel approach to actively compensate wavefront errors in both phase and amplitude using a Liquid Crystal Spatial Light Modulator (LC-SLM) for direct exoplanet imaging. This method involves controlling the wavefront to address challenges posed by stellar coronagraphy. Experimental results demonstrate successful wavefront error compensation in both phase and amplitude components. This technique shows promise for direct exoplanet imaging and may be applied onboard orbital telescopes in the future. Full article

(This article belongs to the Special Issue Optical Systems for Astronomy)

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36 pages, 12180 KiB

Open AccessArticle

Development of Cryogenic Systems for Astronomical Research

by Yuri Balega, Oleg Bolshakov, Aleksandr Chernikov, Aleksandra Gunbina, Valerian Edelman, Mariya Efimova, Aleksandr Eliseev, Artem Krasilnikov, Igor Lapkin, Ilya Lesnov, Mariya Mansfeld, Mariya Markina, Evgenii Pevzner, Sergey Shitov, Andrey Smirnov, Mickhail Tarasov, Nickolay Tyatushkin, Anton Vdovin and Vyacheslav Vdovin

Photonics 2024, 11(3), 257; https://doi.org/10.3390/photonics11030257 - 13 Mar 2024

Cited by 2 | Viewed by 2416

Abstract

The article presents a brief review of cooling systems that ensure various temperature levels (from 0.1 K to 230 K) for radio astronomical receivers of photonic and electronic (or optical and radio) devices. The features of various cooling levels and the requirements for [...] Read more.

The article presents a brief review of cooling systems that ensure various temperature levels (from 0.1 K to 230 K) for radio astronomical receivers of photonic and electronic (or optical and radio) devices. The features of various cooling levels and the requirements for the design of the cooling systems are considered in detail, as well as the approaches to designing interfaces for cooled receivers: vacuum, cryogenic, electrical, mechanical, optical, and other interfaces required for effective operation. The presented approaches to design are illustrated by a series of joint developments of the authors carried out over the past 45 years, including those produced over the past year. Full article

(This article belongs to the Special Issue Optical Systems for Astronomy)

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25 pages, 3033 KiB

Open AccessArticle

SAINT (Small Aperture Imaging Network Telescope)—A Wide-Field Telescope Complex for Detecting and Studying Optical Transients at Times from Milliseconds to Years

by Grigory Beskin, Anton Biryukov, Alexey Gutaev, Sergey Karpov, Gor Oganesyan, Gennady Valyavin, Azamat Valeev, Valery Vlasyuk, Nadezhda Lyapsina and Vyacheslav Sasyuk

Photonics 2023, 10(12), 1352; https://doi.org/10.3390/photonics10121352 - 7 Dec 2023

Cited by 1 | Viewed by 1917

Abstract

In this paper, we present a project of a multi-channel wide-field optical sky monitoring system with high temporal resolution—Small Aperture Imaging Network Telescope (SAINT)— mostly built from off-the-shelf components and aimed towards searching and studying optical transient phenomena on the shortest time scales. [...] Read more.

In this paper, we present a project of a multi-channel wide-field optical sky monitoring system with high temporal resolution—Small Aperture Imaging Network Telescope (SAINT)— mostly built from off-the-shelf components and aimed towards searching and studying optical transient phenomena on the shortest time scales. The instrument consists of twelve channels each containing 30 cm (F/1.5) GENON Max objectives mounted on separate ASA DDM100 mounts with pointing speeds up to 50 deg/s. Each channel is equipped with a 4128 × 4104 pixel Andor Balor sCMOS detector and a set of photometric

g r i z

filters and linear polarizers. At the heart of every channel is a custom-built reducer-collimator module allowing rapid switching of an effective focal length of the telescope—due to it the system is capable of operating in either wide-field survey or narrow-field follow-up modes. In the first case, the field of view of the instrument is 470 square degrees (39 sq.deg. for a single channel) and the detection limits (5

σ

level at 5500 Å) are 12.5, 16.5, 19, 21 with exposure times of 20 ms, 1 s, 30 s and 20 min, correspondingly. In the second, follow-up (e.g., upon detection of a transient of interest by either a real-time detection pipeline, or upon receiving an external trigger) regime, all telescopes are oriented towards the single target, and SAINT becomes an equivalent to a monolithic 1-meter telescope, with the field of view reduced to 11

^{'}

× 11

^{'}

, and the exposure times decreased down to 0.6 ms (1684 frames per second). Different channels may then have different filters installed, thus allowing a detailed study—acquiring both color and polarization information—of a target object with the highest possible temporal resolution. The telescopes are located in two pavilions with sliding roofs and are controlled by a cluster of 25 computers that both govern their operation and acquire and store up to 800 terabytes of data every night, also performing its real-time processing using a dedicated fast image subtraction pipeline. Long-term storage of the data will require a petabyte class storage. The operation of SAINT will allow acquiring an unprecedented amount of data on various classes of astrophysical phenomena, from near-Earth to extragalactic ones, while its multi-channel design and the use of commercially available components allows easy expansion of its scale, and thus performance and detection capabilities. Full article

(This article belongs to the Special Issue Optical Systems for Astronomy)

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22 pages, 6105 KiB

Open AccessArticle

Cryogenic Systems for Astronomical Research in the Special Astrophysical Observatory of the Russian Academy of Sciences

by Yurii Balega, Oleg Bolshakov, Aleksandr Chernikov, Valerian Edelman, Aleksandr Eliseev, Eduard Emelyanov, Aleksandra Gunbina, Artem Krasilnikov, Ilya Lesnov, Mariya Mansfeld, Sergey Markelov, Mariya Markina, Guram Mitiani, Evgenii Pevzner, Nickolay Tyatushkin, Gennady Valyavin, Anton Vdovin and Vyacheslav Vdovin

Photonics 2023, 10(11), 1263; https://doi.org/10.3390/photonics10111263 - 15 Nov 2023

Cited by 3 | Viewed by 2055

Abstract

This article presents the main results and new plans for the development of receivers which are cooled cryogenically to deep cryogenic temperatures and used in optical and radio astronomy research at the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) [...] Read more.

This article presents the main results and new plans for the development of receivers which are cooled cryogenically to deep cryogenic temperatures and used in optical and radio astronomy research at the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) on both the Big Telescope Alt-Azimuthal optical telescope (BTA) and the Radio Astronomical Telescope Academy of Sciences (RATAN-600) radio telescope, 600 m in diameter. These two instruments almost completely cover the frequency range from long radio waves to the IR and optical bands (0.25–8 mm on RATAN and 10–0.3 μm, on BTA) with a certain gap in the terahertz part (8–0.01 mm) of the spectrum. Today, this range is of the greatest interest for astronomers. In particular, the ALMA (Atacama Large Millimeter Array) observatory and the worldwide network of modern telescopes called the EVH (Event Horizon Telescope) operate in this range. New developments at SAO RAS are aimed at mastering this part of the spectrum. Cryogenic systems of receivers in these ranges are a key element of the system and differ markedly from the cooling systems of optical and radio receivers that ensure cooling of the receivers to sub-Kelvin temperatures. Full article

(This article belongs to the Special Issue Optical Systems for Astronomy)

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17 pages, 6326 KiB

Open AccessArticle

A Tutorial on Retroreflectors and Arrays Used in Satellite and Lunar Laser Ranging

by John J. Degnan

Photonics 2023, 10(11), 1215; https://doi.org/10.3390/photonics10111215 - 31 Oct 2023

Cited by 7 | Viewed by 4358

Abstract

The present paper discusses the basics of retroreflector theory and the manner in which they are combined in arrays to service the laser tracking of artificial satellites and the Moon. We begin with a discussion of the relative advantages and disadvantages of solid [...] Read more.

The present paper discusses the basics of retroreflector theory and the manner in which they are combined in arrays to service the laser tracking of artificial satellites and the Moon. We begin with a discussion of the relative advantages and disadvantages of solid versus hollow cube corners and the functional dependence of their optical cross-sections and far-field patterns on cube diameter. Because of velocity aberration effects, the design of an array for a particular space mission depends on many factors, including the desired range accuracy and the satellite’s orbital altitude, velocity, and pass geometry relative to the tracking station. This generally requires the individual retroreflectors in the array to be “spoiled” by perturbing one or more of the 90-degree angles that define a perfect cube corner, or alternatively, by adding a curved surface to a hollow cube. In order to obtain adequate return signal strengths from all points along the satellite path, the rotational orientation of the retroreflectors within the array may need to be varied or “clocked”. Possible approaches to developing millimeter-accuracy arrays with both large cross-sections and ultrashort satellite signatures are discussed, as are new designs proposed to replace aging reflectors on the Moon. Finally, we briefly discuss methods for laser ranging beyond the Moon. Full article

(This article belongs to the Special Issue Optical Systems for Astronomy)

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14 pages, 4673 KiB

Open AccessArticle

Atmospheric Turbulence with Kolmogorov Spectra: Software Simulation, Real-Time Reconstruction and Compensation by Means of Adaptive Optical System with Bimorph and Stacked-Actuator Deformable Mirrors

by Ilya Galaktionov, Julia Sheldakova, Vadim Samarkin, Vladimir Toporovsky and Alexis Kudryashov

Photonics 2023, 10(10), 1147; https://doi.org/10.3390/photonics10101147 - 12 Oct 2023

Cited by 13 | Viewed by 2301

Abstract

Atmospheric turbulence causes refractive index fluctuations, which in turn introduce extra distortions to the wavefront of the propagated radiation. It ultimately degrades telescope resolution (in imaging applications) and reduces radiation power density (in focusing applications). One of the possible ways of researching the [...] Read more.

Atmospheric turbulence causes refractive index fluctuations, which in turn introduce extra distortions to the wavefront of the propagated radiation. It ultimately degrades telescope resolution (in imaging applications) and reduces radiation power density (in focusing applications). One of the possible ways of researching the impact of turbulence is to numerically simulate the spectrum of refractive index fluctuations, to reproduce it using a wavefront corrector and to measure the resultant wavefront using, for example, a Shack–Hartmann sensor. In this paper, we developed turbulence simulator software that generates phase screens with Kolmogorov spectra. We reconstructed the generated set of phase screens using a stacked-actuator deformable mirror and then compensated for the introduced wavefront distortions using a bimorph deformable mirror. The residual amplitude of the wavefront reconstructed by the 19-channel stacked-actuator mirror was 0.26 λ, while the residual amplitude of the wavefront compensated for by the 32-channel bimorph mirror was 0.08 λ. Full article

(This article belongs to the Special Issue Optical Systems for Astronomy)

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11 pages, 6515 KiB

Open AccessArticle

Spektr–UF Mission Spectrograph Space Qualified CCD Detector Subsystem

by Andrey Shugarov and Mikhail Sachkov

Photonics 2023, 10(9), 1032; https://doi.org/10.3390/photonics10091032 - 8 Sep 2023

Cited by 4 | Viewed by 1426

Abstract

Spektr–UF (World Space Observatory Ultraviolet, WSO-UV) is a Russian-led international collaboration aiming to develop a large space-borne 1.7 m Ritchey–Chretién telescope with science instruments to study the Universe in ultraviolet wavelengths. The WSO-UV spectrograph (WUVS) consists of three channels: two high-resolution channels (R [...] Read more.

Spektr–UF (World Space Observatory Ultraviolet, WSO-UV) is a Russian-led international collaboration aiming to develop a large space-borne 1.7 m Ritchey–Chretién telescope with science instruments to study the Universe in ultraviolet wavelengths. The WSO-UV spectrograph (WUVS) consists of three channels: two high-resolution channels (R = 50,000) with spectral ranges of 115–176 nm and 174–310 nm, and a low-resolution (R = 1000) channel with a spectral range of 115–305 nm. Each of the three channels has an almost identical custom detector consisting of a CCD inside a vacuum enclosure, and drive electronics. The main challenges of the WUVS detectors are to achieve high quantum efficiency in the FUV-NUV range, to provide low readout noise (3 e

^{-}

at 50 kHz) and low dark current (<12 e

^{-}

/pixel/hour), to operate with integral exposures of up to 10 h and to provide good photometric accuracy. A custom vacuum enclosure and three variants of a custom CCD272-64 sensor with different UV AR coatings optimised for each WUVS channel were designed. The enclosure prevents contamination and maintains the CCD at the operating temperature of −100

^{\circ}

C, while the temperature of the WUVS optical bench is +20

^{\circ}

C. A camera electronics box (CEB) that houses the CCD drive electronics was developed. Digital correlated double sampling technology allows for extremely low readout noise and flexible frequency for normal and binned pixel readout modes. This paper presents the WUVS detector design drivers, methods for extending the service life of the CCD sensors working with low signals in a space radiation environment and the key calculated parameters and results of the engineering qualification model qualification campaign. Full article

(This article belongs to the Special Issue Optical Systems for Astronomy)

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18 pages, 1882 KiB

Open AccessArticle

Benefits of Intelligent Fuzzy Controllers in Comparison to Classical Methods for Adaptive Optics

by Victor Costa and Wesley Beccaro

Photonics 2023, 10(9), 988; https://doi.org/10.3390/photonics10090988 - 30 Aug 2023

Cited by 2 | Viewed by 1394

Abstract

Adaptive Optics (AO) systems have been developed throughout recent decades as a strategy to compensate for the effects of atmospheric turbulence, primarily caused by poor astronomical seeing. These systems reduce the wavefront distortions using deformable mirrors. Several AO simulation tools have been developed, [...] Read more.

Adaptive Optics (AO) systems have been developed throughout recent decades as a strategy to compensate for the effects of atmospheric turbulence, primarily caused by poor astronomical seeing. These systems reduce the wavefront distortions using deformable mirrors. Several AO simulation tools have been developed, such as the Object-Oriented, MATLAB, and Adaptive Optics Toolbox (OOMAO), to assist in the project of AO. However, the main AO simulators focus on AO models, not prioritizing the different control techniques. Moreover, the commonly applied control strategies in ground-based telescopes are based on Integral (I) or Proportional-Integral (PI) controllers. This work proposes the integration of OOMAO models to Simulink to support the development of advanced controllers and compares traditional controllers with intelligent systems based on fuzzy logic. The controllers were compared in three scenarios of different turbulence and atmosphere conditions. The simulations were performed using the characteristics/parameters of the Southern Astrophysical Research (SOAR) telescope and assessed with the Full Width at Half Maximum (FWHM), Half Light Radius (HLR), and Strehl ratio metrics to compare the performance of the controllers. The results demonstrate that adaptive optics can be satisfactorily simulated in OOMAO adapted to Simulink and thus further increase the number of control strategies available to OOMAO. The comparative results between the MATLAB script and the Simulink blocks designed showed a maximum relative error of

3 %

in the Strehl ratio and

1.59 %

in the FWHM measurement. In the assessment of the control algorithms, the fuzzy PI controller reported a

25 %

increase in the FWHM metrics in the critical scenario when compared with open-loop metrics. Furthermore, the fuzzy PI controller outperformed the results when compared with the I and PI controllers. The findings underscore the constraints of conventional control methods, whereas the implementation of fuzzy-based controllers showcases the promise of intelligent approaches in enhancing control performance under challenging atmospheric conditions. Full article

(This article belongs to the Special Issue Optical Systems for Astronomy)

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15 pages, 2480 KiB

Open AccessArticle

Astronomical Camera Based on a CCD261-84 Detector with Increased Sensitivity in the Near-Infrared

by Irina Afanasieva, Valery Murzin, Valery Ardilanov, Nikolai Ivaschenko, Maksim Pritychenko, Alexei Moiseev, Elena Shablovinskaya and Eugene Malygin

Photonics 2023, 10(7), 774; https://doi.org/10.3390/photonics10070774 - 4 Jul 2023

Cited by 8 | Viewed by 1985

Abstract

Herein, we describe the design, implementation and operation principles of an astronomical camera system, based on a large-format CCD261-84 detector with an extremely thick 200 μm substrate. The DINACON-V controller was used with the CCD to achieve high performance and low noise. The [...] Read more.

Herein, we describe the design, implementation and operation principles of an astronomical camera system, based on a large-format CCD261-84 detector with an extremely thick 200 μm substrate. The DINACON-V controller was used with the CCD to achieve high performance and low noise. The CCD system photometric characteristics are presented. A spatial autocorrelation analysis of flat-field images was performed to reveal the dependence of substrate voltage on the lateral charge spreading. The investigation of the dispersion index for the optimal choice of exposure time is discussed. Studies of the patterns of fringes were carried out in comparison with previous detectors. The amplitude of fringes with CCD261-84 was significantly lower, compared to previous-generation detectors. The results of using a new camera for imaging and spectral observations at the Russian 6 m telescope with the SCORPIO-2 multimode focal reducer are considered. The developed CCD camera system makes it possible to significantly increase the sensitivity in the 800–1000 spectral range. Full article

(This article belongs to the Special Issue Optical Systems for Astronomy)

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21 pages, 2906 KiB

Open AccessArticle

Optical Design of a Slitless Astronomical Spectrograph with a Composite Holographic Grism

by Eduard Muslimov, Damir Akhmetov, Danila Kharitonov, Erik Ibatullin, Nadezhda Pavlycheva, Vyacheslav Sasyuk and Sergey Golovkin

Photonics 2023, 10(4), 385; https://doi.org/10.3390/photonics10040385 - 31 Mar 2023

Cited by 1 | Viewed by 2453

Abstract

In the present work, we consider an optical design of a slitless spectrograph for an existing 0.5 m-class telescope. This design concept has a number of advantages such as compact size, simplicity, and simultaneous coverage of a large field of view. A challenge [...] Read more.

In the present work, we consider an optical design of a slitless spectrograph for an existing 0.5 m-class telescope. This design concept has a number of advantages such as compact size, simplicity, and simultaneous coverage of a large field of view. A challenge with this design is correcting aberrations caused by placing a dispersing element in a converging beam. To overcome this issue, we propose to use a composite grism, which represents a combination of a prism and a volume-phase holographic grating, the latter which is split into zones with independently optimized parameters. We demonstrate two designs of such a grism. In both designs, the spectrograph operates in the range of 450–950 nm in an

F / 6.8

beam and covers a field of view of 35.6

^{'}

× 7.2

^{'}

. Through advanced modeling, it is shown that a composite grism having four rectangular zones with different thickness and index modulation depth of the hologram and recorded with an auxiliary deformable mirror decreases the astigmatic elongation by a factor of 85, increases the spectral resolving power by 4.4 times, and reaches

R 1389

while increasing the average diffraction efficiency by a factor of

1.31

. If we reduce the number of zones to only two, replace the deformable mirror with two static corrector plates, and fix the hologram thickness, the corresponding performance gains still remain high: the astigmatism is reduced by a factor of 61, the spectral resolving power is up to

1.7

times higher, reaching

R 1067

, and the efficiency is increased by a factor of

1.27

. This shows that the proposed design allows the construction of a simple and compact instrument, providing high performance over the entire field of view and spectral range. Full article

(This article belongs to the Special Issue Optical Systems for Astronomy)

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20 pages, 5969 KiB

Open AccessArticle

Wavefront Sensing by a Common-Path Interferometer for Wavefront Correction in Phase and Amplitude by a Liquid Crystal Spatial Light Modulator Aiming the Exoplanet Direct Imaging

by Andrey Yudaev, Alexander Kiselev, Inna Shashkova, Alexander Tavrov, Alexander Lipatov and Oleg Korablev

Photonics 2023, 10(3), 320; https://doi.org/10.3390/photonics10030320 - 16 Mar 2023

Cited by 1 | Viewed by 2386

Abstract

We implemented the common-path achromatic interfero-coronagraph both for the wavefront sensing and the on-axis image component suppression, aiming for the stellar coronagraphy. A common-path achromatic interfero-coronagraph has its optical scheme based on a nulling rotational-shear interferometer. The angle of rotational shear can be [...] Read more.

We implemented the common-path achromatic interfero-coronagraph both for the wavefront sensing and the on-axis image component suppression, aiming for the stellar coronagraphy. A common-path achromatic interfero-coronagraph has its optical scheme based on a nulling rotational-shear interferometer. The angle of rotational shear can be chosen at a small angular extent of about 10 deg. Such a small angular shear maintains the coronagraphic contrast degradation known as the stellar leakage effect, caused by a finite stellar size. We study the phase and amplitude wavefront control by a liquid crystal spatial light modulator of reflection type which is used as the pixilated active adaptive optics unit. Therefore, adaptive optics perform a wavefront-correcting input toward a stellar interfero-coronagraph aiming at the direct exoplanet imaging. Presented here are both the numeric evaluations and the lab experiment stand to prove the declared functionality output. Full article

(This article belongs to the Special Issue Optical Systems for Astronomy)

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12 pages, 1166 KiB

Open AccessArticle

Statistical Tool Size Study for Computer-Controlled Optical Surfacing

by Weslin C. Pullen, Tianyi Wang, Heejoo Choi, Xiaolong Ke, Vipender S. Negi, Lei Huang, Mourad Idir and Daewook Kim

Photonics 2023, 10(3), 286; https://doi.org/10.3390/photonics10030286 - 9 Mar 2023

Cited by 3 | Viewed by 1984

Abstract

Over the past few decades, computer-controlled optical surfacing (CCOS) systems have become more deterministic. A target surface profile can be predictably achieved with a combination of tools of different sizes. However, deciding the optimal set of tool sizes that will achieve the target [...] Read more.

Over the past few decades, computer-controlled optical surfacing (CCOS) systems have become more deterministic. A target surface profile can be predictably achieved with a combination of tools of different sizes. However, deciding the optimal set of tool sizes that will achieve the target residual error in the shortest run time is difficult, and no general guidance has been proposed in the literature. In this paper, we present a computer-assisted study on choosing the proper tool size for a given surface error map. First, we propose that the characteristic frequency ratio (CFR) can be used as a general measure of the correction capability of a tool over a surface map. Second, the performance of different CFRs is quantitatively studied with a computer simulation by applying them to guide the tool size selection for polishing a large number of randomly generated surface maps with similar initial spatial frequencies and root mean square errors. Finally, we find that CFR = 0.75 achieves the most stable trade-off between the total run time and the number of iterations and thus can be used as a general criterion in tool size selection for CCOS processes. To the best of our knowledge, the CFR is the first criterion that ties tool size selection to overall efficiency. Full article

(This article belongs to the Special Issue Optical Systems for Astronomy)

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16 pages, 3893 KiB

Open AccessArticle

EXPLANATION: Exoplanet and Transient Event Investigation Project—Optical Facilities and Solutions

by Gennady Valyavin, Grigory Beskin, Azamat Valeev, Gazinur Galazutdinov, Sergei Fabrika, Iosif Romanyuk, Vitaly Aitov, Oleg Yakovlev, Anastasia Ivanova, Roman Baluev, Valery Vlasyuk, Inwoo Han, Sergei Karpov, Vyacheslav Sasyuk, Alexei Perkov, Sergei Bondar, Faig Musaev, Eduard Emelianov, Timur Fatkhullin, Sergei Drabek, Vladimir Shergin, Byeong-Cheol Lee, Guram Mitiani, Tatiana Burlakova, Maksim Yushkin, Eugene Sendzikas, Damir Gadelshin, Lisa Chmyreva, Anatoly Beskakotov, Vladimir Dyachenko, Denis Rastegaev, Arina Mitrofanova, Ilia Yakunin, Kirill Antonyuk, Vladimir Plokhotnichenko, Alexei Gutaev, Nadezhda Lyapsina, Vladimir Chernenkov, Anton Biryukov, Evgenij Ivanov, Elena Katkova, Alexander Belinski, Eugene Sokov, Alexander Tavrov, Oleg Korablev, Myeong-Gu Park, Vladislav Stolyarov, Victor Bychkov, Stanislav Gorda, A. A. Popov and A. M. Sobolev Show full author list Hide full author list

Photonics 2022, 9(12), 950; https://doi.org/10.3390/photonics9120950 - 8 Dec 2022

Cited by 7 | Viewed by 2879

Abstract

Over the past decades, the achievements in astronomical instrumentation have given rise to a number of novel advanced studies related to the analysis of large arrays of observational data. One of the most famous of these studies is a study of transient events [...] Read more.

Over the past decades, the achievements in astronomical instrumentation have given rise to a number of novel advanced studies related to the analysis of large arrays of observational data. One of the most famous of these studies is a study of transient events in the near and far space and a search for exoplanets. The main requirements for such kinds of projects are a simultaneous coverage of the largest possible field of view with the highest possible detection limits and temporal resolution. In this study, we present a similar project aimed at creating an extensive, continuously updated survey of transient events and exoplanets. To date, the core of the project incorporates several 0.07–2.5 m optical telescopes and the 6-m BTA telescope of the Special Astrophysical Observatory of RAS (Russia), a number of other Russian observatories and the Bonhyunsan observatory of the Korea Astronomy and Space Science Institute (South Korea). Our attention is mainly focused on the description of two groups of small, wide-angle optical telescopes for primary detection. All the telescopes are originally designed for the goals of the project and may be of interest to the scientific community. A description is also given for a new, high-precision optical spectrograph for the Doppler studies of transient and exoplanet events detected within the project. We present here the philosophy, expectations and first results obtained during the first year of running the project. Full article

(This article belongs to the Special Issue Optical Systems for Astronomy)

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13 pages, 8791 KiB

Open AccessArticle

Image Degradation Model for Dynamic Star Maps in Multiple Scenarios

by Haima Yang, Yan Jin, Yinan Hu, Dawei Zhang, Yong Yu, Jin Liu, Jun Li, Xiaohui Jiang and Xiaojun Yu

Photonics 2022, 9(10), 673; https://doi.org/10.3390/photonics9100673 - 20 Sep 2022

Cited by 3 | Viewed by 1688

Abstract

To meet the ground test requirements of star sensors, we establish the star map simulation algorithm and the interactive interface in multiple scenarios. The combination of the degradation model of star points, the imaging noise model, and the attitude disturbance model is introduced [...] Read more.

To meet the ground test requirements of star sensors, we establish the star map simulation algorithm and the interactive interface in multiple scenarios. The combination of the degradation model of star points, the imaging noise model, and the attitude disturbance model is introduced to solve the problem of different patterns of noise existing in the actual measurement, improving the traditional simulation model. In addition, a user-friendly interface design makes it easier for both scholars and average individuals to understand the parameters and then generate static single-frame star maps—or a series of dynamic sequence star maps—under various conditions. The results of the proposed star map simulation method are highly comparable to the actual captured star images, and this method can be applied for the tests and calibrations of star sensors. Full article

(This article belongs to the Special Issue Optical Systems for Astronomy)

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Review

Jump to: Research

18 pages, 814 KiB

Open AccessReview

Overview on Space-Based Optical Orbit Determination Method Employed for Space Situational Awareness: From Theory to Application

by Zhe Zhang, Gaopeng Zhang, Jianzhong Cao, Cheng Li, Weining Chen, Xin Ning and Zheng Wang

Photonics 2024, 11(7), 610; https://doi.org/10.3390/photonics11070610 - 27 Jun 2024

Cited by 3 | Viewed by 2887

Abstract

Leveraging space-based optical platforms for space debris and defunct spacecraft detection presents several advantages, including a wide detection range, immunity to cloud cover, and the ability to maintain continuous surveillance on space targets. As a result, it has become an essential approach for [...] Read more.

Leveraging space-based optical platforms for space debris and defunct spacecraft detection presents several advantages, including a wide detection range, immunity to cloud cover, and the ability to maintain continuous surveillance on space targets. As a result, it has become an essential approach for accomplishing tasks related to space situational awareness. However, the prediction of the orbits of space objects is crucial for the success of such missions, and current technologies face challenges related to accuracy, reliability, and practical efficiency. These challenges limit the performance of space-based optical space situational awareness systems. To drive progress in this field and establish a more effective and reliable space situational awareness system based on space optical platforms, this paper conducts a retrospective overview of research advancements in this area. It explores the research landscape of orbit determination methods, encompassing orbit association methods, initial orbit determination methods, and precise orbit determination methods, providing insights from international perspectives. The article concludes by highlighting key research areas, challenges, and future trends in current space situational awareness systems and orbit determination methods. Full article

(This article belongs to the Special Issue Optical Systems for Astronomy)

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