Telescope Applications Research Articles

Multi-facial freeform monolith optics for astronomical and space applications

The utilization of a multi-facial freeform monolithic (MFFM) component in a compact Cassegrain configuration design offers unprecedented capabilities to accommodate various next-generation science instruments. The concept of the MFFM component can be employed for applications in telescopes working at ultra-violet, optical, infrared, terahertz, microwave, and even radio frequencies. MFFM finds its scope in space optical and astronomical systems where the risks are associated with the alignment, manufacturability, and maintaining large-sized apertures, large number of components, cost, and volume of the flight optical terminals and instruments. The current challenges faced at the manufacturing phase of MFFM are the precision positioning of each surface concerning the optical axis and maintaining the required edge thickness. This paper presents the optical design, fabrication, measurement, and in-laboratory characterization of MFFM. The results of a prototyping effort through ultra-precision single-point diamond turning (SPDT) and coating demonstrate the feasibility of producing these elements as per size and weight requirements. The experimental results show excellent surface qualities in terms of nanometric surface roughness and close-to-submicron form accuracy on each surface of the freeform monolith. Focusing performance and imaging performance are carried out to validate the designed and manufactured precision component. The main contribution is highlighted in terms of the optimized fabrication process for producing the precision MFFM for a fast optical system while balancing the alignment errors. The demonstrated research work highlights the intriguing possibilities of the monolith and creates new avenues for research in domains that use huge optical systems, such as astrophysical study, planetary observation, earth monitoring, and geosciences.

Empowering Astronomical Exploration: Advancement of New Moon Observation Devices in Sarawak, Malaysia

Understanding the motion of celestial objects is essential for space exploration. Observing the new crescent Moon requires advanced technological devices due to the moon’s position in the atmosphere and the refraction of sunlight on the horizon. Nowadays, theodolite and telescope applications are commonly used for new crescent moon sightings because they offer superior visibility compared to the naked eye. In Sarawak, the Falak Section holds the authority to observe the new crescent Moon to determine the beginning of the Hijree month. Thus, this study aims to examine the development of devices to observe the new moon crescent in the Sarawak Mufti Department. Qualitative methods are employed, involving the perspectives of astronomers and data on new crescent Moon observations using the observation devices in the Falak Section. From 1997 onwards, the Sarawak Mufti Department had three theodolites and seven telescopes specifically for new crescent moon observations. Additionally, there are 22 recorded data of new crescent Moon sightings using these devices. These findings indicate a direct correlation between the observation devices and the potential visibility of the new crescent Moon in Sarawak. This study will benefit the Sarawak Mufti Department in evaluating suitable devices for new crescent Moon observations, whether acquiring new devices or selecting devices for new crescent moon observations.

Molecular dynamics simulation analysis of energy deposition on the evolution of single crystal silicon defect system

The understanding of the evolution of subsurface damage layer (SDL) in monocrystalline silicon materials following energy deposition holds significant importance in guiding the service process of single-crystal silicon devices. Therefore, on the basis of previous studies on defect generation and evolution of perfect monocrystalline silicon system, the structure evolution of monocrystalline silicon nano-grinding defect system after energy deposition was analyzed by molecular dynamics simulation. The results show that with the energy deposition, part of the crystal structure undergoes a phase transformation, which leads to the increase in the volume of the material and the surface bulge. The thickness of the subsurface damage layer gradually increases, reaches a maximum at a power density of 15×108 W/cm2, and then decreases before increasing again. The impact of energy deposition on surface roughness exhibits an initial gradual increase followed by a subsequent decrease. The work reveals the evolution of sedimentary systems at the atomic level, thus contributing to the application of ultra-precision monocrystalline silicon mirrors and telescopes.

Computational adaptive telescope imaging via self-interference digital holography

Conventional optical telescope only collect the amplitude of optical wavefront with incoherent light, while self-interference incoherent digital holography offers a unique method of coding both the optical wavefront amplitude and phase information by interference patterns. We developed an adaptive non-scanning three-dimensional (3D) telescopic imaging technique based on self-interference incoherent holography with a geometric phase lens (GP-SIDH). The phase recorded in the point spread hologram and the incoherent self-interference extended holograms are employed to detect spatial positions, correct optical aberration and extract edges by computational reconstruction. The 3D imaging and position detection performances of our proposed method are investigated. Both simulations and experimental results show that the proposed method exhibits better performances for different depth objects imaging and space position detection. Furthermore, this system can be easily modularization and implanted into any existing optical telescopic system owing to its simplicity and convenience. The proposed approach can be a powerful tool for the multi-objects long-working-distance imaging, which is more valuable for telescope application.

Reactive ion plasma etched surface relief gratings for low/medium/high resolution spectroscopy in astronomy (Erratum)

The <i>Journal of Astronomical Telescopes, Instruments, and Systems</i> (JATIS) publishes peer-reviewed papers reporting on original research in the development, testing, and application of telescopes, instrumentation, techniques, and systems for ground- and space-based astronomy.

Synthesis mechanism of Ni–Co alloy uniting ultrahigh strength with tensile ductility via abrasive-assisted electroforming

Persistent efforts are being made to combine strength and ductility in metallic nanomaterials. We successfully prepared a homogeneous nanocrystalline Ni−27%Co alloy exhibiting ultrahigh strength and sufficient ductility using abrasive-assisted electroforming (AAE) with free ceramic beads. The AAE process permits superior control of the microstructure of nanocrystalline Ni–Co alloy. Our results demonstrated that the structure of the Ni−27%Co alloy (AAE) consists of ultrafine equiaxed nanocrystals with an average grain size of 88 nm and a twin boundary fraction of 24%. The alloy structure results from the combined effect of the addition of Co as an alloying element and the electrochemical and physical action of the moving ceramic beads on the nucleation and growth. The Ni−27%Co alloy (AAE) exhibited superior yield and tensile strength of 1103 ± 47 and 1639 ± 19 MPa, respectively, while having excellent ductility with tensile elongation to failure of 8.5 ± 0.5%. The yield strength of the Ni−27%Co alloy (AAE) was approximately 1.6 times that of the Ni−26%Co alloy (Direct current electroforming, DCE). This result can be attributed to the contribution of strengthening mechanisms that involve frictional stress, dislocation, grain boundary, solid solution, and twin boundary strengthening. Among them, the grain boundary (Hall-Petch) strengthening, arising from grain boundary-dislocation interactions, and twin boundary strengthening, arising from the intersection of the twin-dislocation, account for approximately 70% of the total yield strength. The tensile ductility of the Ni−27%Co alloy (AAE) at ultrahigh flow stress can be preserved by simultaneous strain and strain-rate hardening using the AAE method. This study provides a novel strategy for synthesizing ductile ultrahigh strength materials for applications in microelectromechanical systems, surface coatings, and X-ray telescopes.

State-of-art Facilities and Prospect of Radio Telescopes

The radio telescopes play a crucial role in astrophysical observations; hence it is necessary to discuss about the significance, structure, and applications of radio telescope and analyse the difference between the state-of-art radio telescopes (FAST and SKA) based on present information. Specifically, the background and present conditions as well as the history of radio telescopes will be introduced initially. Subsequently, the significance of radio telescope will be explained, including structure and application of radio telescopes. Subsequently, the doubts on FAST and SKA and strengths of them will be clarified. Eventually, the problems and limitations about radio telescope and the future prospect will be discussed. Overall, these results shed light on offering suggestions for future development of galaxy and cosmology observations.

Special Section Guest Editorial: Extremely Large Telescopes

The <i>Journal of Astronomical Telescopes, Instruments, and Systems</i> (JATIS) publishes peer-reviewed papers reporting on original research in the development, testing, and application of telescopes, instrumentation, techniques, and systems for ground- and space-based astronomy.

Co-phase state detection for segmented mirrors by dual-wavelength optical vortex phase-shifting interferometry.

The application of large-aperture telescopes requires the support of co-phase measurement techniques for segmented mirrors. This paper proposes a novel method to detect the co-phase state of segmented mirrors by applying a dual-wavelength phase-shifting interferometer based on optical vortex. Theory and experiments indicate that the wrapped phase map edges obtained by phase-shifting interference of the vortex beam are distributed in the form of a Fermat spiral. The piston error of the segmented mirrors corresponds to the rotation of the standard Fermat spiral center. In contrast, the tip/tilt error corresponds to the alteration of the center position of the deformed Fermat spiral. The rotation angle and the center position of the spiral are obtained by curve fitting, and the co-phase errors can be inversely solved. The experiments achieved an accuracy of approximately 4.04 nm in the piston and 0.16″ in the tip/tilt. The method avoids using complex lens arrays and devices, has an extended measurement range, high accuracy, and allows the co-phase errors between all sub-mirrors to be obtained in real-time. This study provides a novel and general method for detecting co-phase errors in a segmented primary mirror.

Special Section Guest Editorial: The SKA Observatory

The <i>Journal of Astronomical Telescopes, Instruments, and Systems</i> (JATIS) publishes peer-reviewed papers reporting on original research in the development, testing, and application of telescopes, instrumentation, techniques, and systems for ground- and space-based astronomy.

Design, implementation, and qualification of high-performance time and frequency reference for the MeerKAT telescope (Erratum)

The <i>Journal of Astronomical Telescopes, Instruments, and Systems</i> (JATIS) publishes peer-reviewed papers reporting on original research in the development, testing, and application of telescopes, instrumentation, techniques, and systems for ground- and space-based astronomy.

New design of large fully-steerable radio telescope reflector based on homogenized mesh structure

The self-weight of a large fully-steerable radio telescope is one of the important factors affecting its performance. In the existing reflector system scheme, the problem of surface accuracy caused by its large and heavy structure has seriously restricted the application and implementation of large radio telescopes. Therefore, a new mesh structure scheme for a large fully-steerable radio telescope reflector is proposed in this paper. This scheme is based on a homogenized mesh back-up structure in the form of a quasi-geodesic grid and regular quasi-tri-prism or tetrahedron, which can significantly reduce the structural complexity and self-weight of the reflector under the condition that the reflector can meet the desired performance requirements. Finally, the feasibility and rationality of the scheme are evaluated by numerical simulation analysis, which has significant advantages and provides a new design for the reflector of a large fully-steerable radio telescope.

Experimental realization of a Fresnel hologram as a super spectral resolution optical element

A highly dispersive, diffractive optical element is designed and realized for an extremely high spectral resolution spectroscopy for exoplanet telescope application. Our design uses an annular Fresnel hologram to transform incident starlight directly into a spectrogram. The recording of the hologram is accomplished using two spherical waves of different radius of curvature. The resultant hologram consists of an annular grating structure with a gradually shrinking period as a function of increasing radius. The variable period not only could bring the incoming star-light into focus, but also exhibits a large on-axis chromatic behavior. We demonstrate a dispersion of wavelength 430–700 nm over 190 mm on-axis distance, leading to a super fine spectral resolution 0.0266 nm at wavelength 515 nm for a detector size of 20 µm.

Fabrication of integrated silicon PIN detector based on Al-Sn-Al bonding for ΔE-E telescope application

The conventional monolithic integration of silicon PIN detector as △E-E telescope suffer from incompatibility with IC process, signal crosstalk, high cost, etc.. In this paper, integrated silicon PIN detector based on Al-Sn-Al bonding is proposed. The intermediate conductive layer between thin and thick PIN structure comprises of metallic bonding layer, which can reduce the signal crosstalk. Moreover, the novel integration process enables known-good-die (KGD) bonding of thin and thick PIN structure, which increases flexibility and reliability of the fabrication process. Besides, the fabrication reduces the cost and increases reliability by utilizing silicon integrated process.

Optical calibration and first light for the deformable mirror demonstration mission CubeSat (DeMi)

Microelectromechanical systems (MEMS) deformable mirrors (DMs) can provide high-precision wavefront control with a small form-factor, low power device. This makes them a key technology option for future space telescopes requiring adaptive optics for high-contrast imaging of exoplanets with a coronagraph instrument. The Deformable Mirror Demonstration Mission (DeMi) CubeSat payload is a miniature space telescope designed to demonstrate MEMS DM technology in space for the first time. The DeMi payload contains a 50-mm primary mirror, an internal calibration laser source, a 140-actuator MEMS DM from Boston Micromachines Corporation, an image plane wavefront sensor, and a Shack–Hartmann wavefront sensor (SHWFS). The key DeMi payload requirements are to measure individual actuator wavefront displacement contributions to a precision of 12 nm and correct both static and dynamic wavefront errors in space to less than 100-nm RMS error. The DeMi mission will raise the technology readiness level of MEMS DM technology from a five to at least a seven for future space telescope applications. We summarize the DeMi optical payload design, calibration, optical diffraction model, alignment, integration, environmental testing, and preliminary data from in-space operations. Ground testing data show that the DeMi SHWFS can measure individual actuator deflections on the MEMS DM to within 10 nm of interferometric calibration measurements and can meet the 12-nm precision mission requirement for actuator deflection voltages between 0 and 120 V. Payload data from throughout environmental testing show that the MEMS DM and DeMi payload survived environmental testing and provides a valuable baseline to compare with space data. Initial data from space operations show the MEMS DM actuating in space with a median agreement between individual actuator measurements from space and equivalent ground testing data of 12 nm.

Design and Analysis of Variable Flux Arc Permanent Magnet Motor With Multiple Excitations

Arc permanent magnet (PM) motors show good prospects in large telescope application. To explore an appropriate arc PM motor (APMM) used in the large telescope drive, this article investigates a variable flux APMM (VFAPMM) with dual-PM excitation (DPM-VFAPMM). The DPM-VFAPMM incorporates the merits of the APMM, the hybrid excited motor, and the DPM excited motor. The motor structure and working principle of the DPM-VFAPMM are described. Then, a special winding cross-connection method is adopted to mitigate the torque ripple caused by the end effect. Finally, the electromagnetic performances of the DPM-VFAPMM, the rotor-PM VFAPMM, the stator-PM VFAPMM, and the surface-mounted-PM VFAPMM are investigated and compared. The comparison results show that compared with the other three motors, the DPM-VFAPMM shows the highest flux linkage, the highest back electromotive force, the highest average torque, the highest efficiency, and the second lowest torque ripple. Simultaneously, the DPM-VFAPMM shows high torque/effective PM usage. The advantages of high average torque and low torque ripple show that the DPM-VFAPMM is suitable for the potential application of the large telescope drive.

Special Section Guest Editorial: The Origins Space Telescope

The <i>Journal of Astronomical Telescopes, Instruments, and Systems</i> (JATIS) publishes peer-reviewed papers reporting on original research in the development, testing, and application of telescopes, instrumentation, techniques, and systems for ground- and space-based astronomy.

Comprehensive line-spread function error budget for the off-plane grating rocket experiment (Erratum)

The <i>Journal of Astronomical Telescopes, Instruments, and Systems</i> (JATIS) publishes peer-reviewed papers reporting on original research in the development, testing, and application of telescopes, instrumentation, techniques, and systems for ground- and space-based astronomy.

(Invited) Electroforming in Space and Ground Telescopes

In the last 25 years, electroforming process has been extensively optimised to produce grazing incidence optics for the X-ray space telescopes, enabling the renown observatories Beppo-SAX for the Italian Space Agency, SWIFT for NASA, XMM Newton for ESA, eROSITA for MPE.These optics are made of thin Nickel mirrors that are grown by electroforming process in an electrolytic bath on a Gold coated mandrel.Mandrels are manufactured in Aluminium alloy with NiP coating, which allows, after polishing to reach very smooth roughness in the order of 0.3 nm.After separation of the mirror from the mandrel, Gold layer becomes the X-Ray optical reflecting coating, preserving the low roughness of the mandrel.The Nickel Mirror shells are nested tightly in high-performance optical structures, the X ray telescope.The electroforming cycle ranged between 40 and 100 hours, depending on the thickness of the mirrors, typically between 0.2 and 0.6 mm for the innermost and outermost shells, respectively. The average electroforming time is 65 hours per mirror, with 1 hour for assembly and preparation of the mandrel and 1 hour for separation after electroforming.Electroforming has also been adopted for production of large reflector panels for sub-millimetre radio telescope applications. These are laminated panels made of electroformed Nickel skins bonded to an Aluminium honeycomb core over a precise mould, resulting in typical shape accuracy of 8 µm at only 10 kg/m² mass density.Between 2006 and 2016, 3000 mirror panels for 25 antennas of the ALMA radio-telescope array of ESO and 1600 mirror panels for the 50-m diameter Large Millimetre Telescope (LMT) “Alfonso Serrano” of INAOE were designed, produced and tested.Electroforming replica consists of the replication of mirror substrates from high precision mandrels by means of the electroforming process.The mandrel is machined and polished to the shape accuracy and surface roughness requirements of the final mirror.In the electroforming process, the mandrel is Gold-coated by e-beam evaporation and then immersed in the electrolytic bath. Nickel ions, deposit onto the Gold-coated mandrel creating a low-stress Nickel mirror.Upon reaching the desired thickness, the mandrel is removed from the bath and the mirror is separated from the mandrel. In this process, the Gold layer is bonded to the mirror, creating an integrated reflective layer with the same roughness as the mandrel. The mandrel is then qualified for the next electroforming cycle, where another mirror is replicated from the same mandrel, and so on for the following cycles.Process cycles, key inspection points, verification and testing as part of the production cycles will be described and presented.Panoramic view of ALMA radio-telescopes. Photo courtesy of ESO. Figure 1

Hypersensitive Tunable Josephson Escape Sensor for Gigahertz Astronomy

Sensitive photon detection in the gigahertz band constitutes the cornerstone to study different phenomena in astronomy, such as radio burst sources, galaxy formation, cosmic microwave background, axions, comets, gigahertz-peaked spectrum radio sources and supermassive black holes. Nowadays, state of the art detectors for astrophysics are mainly based on transition edge sensors and kinetic inductance detectors. Overall, most sensible nanobolometers so far are superconducting detectors showing a noise equivalent power (NEP) as low as 2x10-20 W/Hz1/2. Yet, fast thermometry at the nanoscale was demonstrated as well with Josephson junctions through switching current measurements. In general, detection performance are set by the fabrication process and limited by used materials. Here, we conceive and demonstrate an innovative tunable Josephson escape sensor (JES) based on the precise current control of the temperature dependence of a fully superconducting one-dimensional nanowire Josephson junction. The JES might be at the core of future hypersensitive in situ-tunable bolometers or single-photon detectors working in the gigahertz regime. Operated as a bolometer the JES points to a thermal fluctuation noise (TFN) NEP_TFN 1x10-25 W/Hz1/2, which as a calorimeter bounds the frequency resolution above 2 GHz, and resolving power below 40 at 50 GHz, as deduced from the experimental data. Beyond the obvious applications in advanced ground-based and space telescopes for gigahertz astronomy, the JES might represent a breakthrough in several fields of quantum technologies ranging from subTHz communications and quantum computing to cryptography and quantum key distribution.