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A new version of the stellar intensity interferometry instrument for the ASTRI Mini-Array telescopes
This paper will introduce the different printing methods and post-processing steps to convert AM ceramic samples into reflective mirrors. The samples are flat disks, 50mm diameter and 5mm in height, with three samples printed in SiC + Si and three printed in fused silica. Early results in polishing the SiC + Si material demonstrated that a micro-roughness of ∼2nm Sq could be achieved. To build on this study, the 50mm SiC + Si samples had three different AM finishing steps to explore the best approach for abrasive lapping and polishing, the reflective surfaces achieved demonstrated micro-roughness values varied between 2nm and 5nm Sq for the different AM finishing steps. To date, the printed fused silica material has heritage in lens applications; however, its suitability for mirror fabrication was to be determined. Abrasive lapping and polishing was used to process the fused silica to reflective surface and an average micro-roughness of <1nm Sq achieved on the samples.
The secondary mirrors of the ASTRI telescopes were realized already at the beginning of the ASTRI Project. After a few years, some of them revealed a clear degradation of the surface reflective coating. Therefore, it was necessary to look for a qualified industrial supplier able to perform a new coating of these mirrors. To this aim, the ASTRI Collaboration identified the French company CILAS as the best option. In this paper, we present the activities performed by CILAS on the mirrors. We first describe the coating approach adopted by CILAS and its tuning to the case of the ASTRI M2 mirrors. Then, we describe the qualification activities of the coating process, the problems arisen and the remedial actions that were adopted. Finally, we report the obtained results from the reflectivity and homogeneity points of view.
The facility is compact (just 8 m x 14 m). Thanks to an innovative optical design based on an asymmetrical-cut crystal associated with a paraboloidal grazing incidence mirror, it can produce an expanded X-ray beam (170 mm x 60 mm) with low divergence (about 2 arcsec measured for the 4.51 keV beamline) at the two monochromatic energies of 4.51 keV and 1.49 keV. This allows us to calibrate each SPO MM's Effective Area and Point Spread Function precisely.
The first beamline, at 4.51 keV photon energy, is already operational, as the commissioning was completed in Q1-2023. The second beamline, at 1.49 keV energy, is being developed. It presents some more challenging aspects from both the design and implementation points of view. The monochromator stage is based on two Quartz (100); two ADP asymmetric-cut crystals (101) will provide the horizontal expansion of the beam. The X-ray source needs to be very brilliant (5 x 1011 - 1012 ph/s/sterad) due to the large fraction of photons rejected by the crystals.
This paper describes the ongoing activities. It will present the results of the 4.51 keV X-ray beamline optimization and the tests performed on a coated MM. It will also describe the progress in implementing the 1.49 keV components and discuss the comparison with other X-ray testing facilities.
The Silicon Pore Optics (SPO) enables the NewAthena mission, delivering an unprecedented combination of good angular resolution, large effective area and low mass. The SPO technology builds significantly on spin-in from the semiconductor industry and is designed to allow a cost-effective flight optics implementation, compliant with the programmatic requirements of the mission.
The NewAthena X-ray optics is highly modular, consisting of hundreds of compact mirror modules arranged in concentric circles and mounted on a metallic optical bench. All aspects of the optics are being developed in parallel, from the industrial production of the mirror plates, over the highly efficient assembly into mirror modules, to the alignment of the mirror modules and their fixation on the optical bench. Dedicated facilities are being built to measure the performance of the NewAthena X-ray telescope optics, demonstrating their compatibility with the environmental and scientific requirements.
An overview is provided of the activities preparing the implementation of the NewATHENA optics.
The next generation x-ray observatory ATHENA (advanced telescope for high energy astrophysics) requires an optics with unprecedented performance. It is the combination of low mass, large effective area and good angular resolution that is the challenge of the x-ray optics of such a mission. ATHENA is the second large class mission in the science programme of ESA, and is currently in a reformulation process, following a design-to-cost approach to meet the cost limit of an ESA L-class mission.
The silicon pore optics (SPO) is the mission enabler being specifically developed for ATHENA, in a joint effort by industry, research institutions and ESA. All aspects of the optics are being addressed, from the mirror plates and their coatings, over the mirror modules and their assembly into the ATHENA telescope, to the facilities required to build and test the flight optics, demonstrating performance, robustness, and programmatic compliance.
The SPO technology is currently being matured to the level required for the adoption of the ATHENA mission, i.e., the start of the mission implementation phase. The monocrystalline silicon material and pore structure of the SPO provide these optics with excellent thermal and mechanical properties. Benefiting from technology spin-in from the semiconductor industry, the equipment, processes, and materials used to produce the SPO are highly sophisticated and optimised.
The abbreviation “eXTP” represents the enhanced x-ray timing and polarimetry, which is a key science mission initiated by the Chinese scientists, designed to study the state of matter under extreme conditions of density, gravity and magnetism [1]. Various payloads would be on board of the satellite. The SFA, namely the spectroscopy focusing array, consisting of nine identical x-ray telescopes working in the energy range of 0.5-10 keV, will be the focus here [1]. SFA has a field-of-view of 12 arcmin for each and a collecting area of 900 cm2 and 550 cm2 for each at 2 keV and 6 keV respectively [1].
This paper starts with a brief introduction of the general optics, and then goes across some important design aspects. It covers contents from the structural and thermal designs to the CAE analyses as well as the current status. The large diameter and huge focal length of the optics will definitely bring big issues to the robustness of the carrying structure under the severe conditions given by the launcher.
According to the current design, the mirror assembly will have 3 feet and 24 spokes. Vibration tests were already performed on a few prototypes by IHEP, and a preliminary evaluation on the feasibility of the design has been achieved. It clearly stated that the current design with only a single spider can probably survive the vibration tests assuming a compromised test condition somewhere. CAE models were adjusted thereafter to match the test results, which could be used for further assessments in a near future.
Of course, there are always uncertainties associated with our arguments. More detailed prototypes with mechanically fully representative shells were still under design. Hopefully, highly reliable results could be retrieved soon.
The ASTRI Mini-Array is an international project led by the Italian National Institute for Astrophysics (INAF) aiming at building and operating an array of nine Imaging Atmospheric Cherenkov Telescopes (IACTs) at the Observatorio del Teide in Tenerife (Canary Islands, Spain). UVSiPM, a calibrated small photon counter working in the 280-900 nm wavelength range, is one of the auxiliary instruments of the ASTRI Mini-Array.
UVSiPM is mainly devoted to measure the level of night sky background during the ASTRI Mini-Array observations in the same energy range of the ASTRI cameras. It is composed of one single multi-pixel SiPM sensor (the same model adopted in the ASTRI Mini-Array Cherenkov cameras) coupled to an electronic chain working in single photon counting mode. The design of the optical system foresees a pin-hole mask equipped with a collimator to regulate the UVSiPM field of view. UVSiPM will be mounted on the external structure of one of the ASTRI Mini-Array telescopes and co-aligned with its camera. In addition, it will be used as a support instrument for the absolute end-to-end calibration of the ASTRI Mini-Array telescopes performed with the illuminator, a further auxiliary device devoted to perform the optical throughput calibration of each telescope of the array. Last but not least, UVSiPM can be used as diagnostic tool for the camera functionalities. In this contribution we present the overall design of the UVSiPM instrument and some preliminary results of its performance based on simulations.
The main scientific instrument of the ASTRI-Horn telescope is an innovative and compact Camera with Silicon- Photomultiplier based detectors and a specifically designed fast read-out electronics based on a custom peak-detector mode. The thermo-mechanical assembly is designed to host both the entire electronics chain, from the sensors to the raw data transmission system and the calibration system, and the complete thermoregulation system.
This contribution gives a high level description of the T/M and electrical design of the Cherenkov Camera, it describes the assembling procedure of its different subsystems and their integration into the complete camera system. A discussion about possible design improvements coming from the problems/difficulties encountered during assembly is also presented. Finally, results from engineering tests conducted in-field are also presented.
To overcome these limitations, we started in 2012 to design a facility aimed at generating a broad (170 x 60 mm2), uniform and low-divergent (1.5 arcsec HEW) X-ray beam within a small lab (∼ 9 x 18 m2), to characterize the ATHENA MM. BEaTriX (the Beam Expander Testing X-ray facility) makes use of an X-ray microfocus source, a paraboloidal mirror, a crystal monochromation system, and an asymmetrically-cut diffracting crystal for the beam expansion. These optical components, in addition to a modular low-vacuum level (10-3 mbar), enable to match the ATHENA SPO acceptance requirements.
The realization of this facility at INAF-OAB in Merate (Italy) is now on going. Once completed, BEaTriX can be used to test the Silicon Pore Optics modules of the ATHENA X-ray observatory, as well as other optics, like the ones of the Arcus mission. In this paper we report the advancement status of the facility.
Taking advantage of emerging technology in mirror manufacturing and spacecraft formation flying, Simbol-X will push grazing incidence imaging up to ~ 80 keV and beyond, providing a strong improvement both in sensitivity and angular resolution compared to all instruments that have operated so far above 10 keV. This technological breakthrough will open a new highenergy window in astrophysics and cosmology. Here we will address the problematic of the development for such a distributed and deformable instrument. We will focus on the main performances of the telescope, like angular resolution, sensitivity and source localization. We will also describe the specificity of the calibration aspects of the payload distributed over two satellites and therefore in a not “frozen” configuration.
Cold and Hot Slumped Glass Optics with interfacing ribs for high angular resolution x-ray telescopes
Laboratory demonstration of the piezoelectric figure correction of a cylindrical slumped glass optic
The ASTRI SST-2M telescope structure and mirrors have been installed at the INAF observing station at Serra La Nave, on Mt. Etna (Sicily, Italy) in September 2014. Its performance verification phase began in autumn 2015. Part of the scheduled activities foresees the study and characterization of the optical and opto-mechanical performance of the telescope prototype.
In this contribution we report the results achieved in terms of kinematic model analysis, mirrors reflectivity evolution, telescopes positioning, flexures and pointing model and the thermal behavior.
Deflectometry is an interesting technique because it allows the fast characterization of free-form optics. The capabilities of deflectometry in measuring medium-high frequencies are well known, but the low frequencies error characterization is more challenging. Our facility design foresees an innovative approach based on the acquisition of multiple direct images to enhance the performance on the challenging low frequencies range.
This contribution presents the error-budget analysis of the measuring method and a study of the configuration tolerances required to allow the use of deflectometry in the realization of optical components suitable for astronomical projects with a requirement of high accuracy for the optics. As test examples we took into account mirrors for the E-ELT telescope.
We present first results of demonstrating Silicon Pore Optics for the extreme radial positions of the Athena telescope. For the inner most radii (0.25 m) a new mirror plate design is shown which overcomes the challenges of larger curvatures, higher stress values and bigger plates. Preliminary designs for the mounting system and its mechanical properties are discussed for mirror modules covering all other radial positions up to the most outer radius of the Athena telescope.
In this framework, the Italian ASTRI program, led by the Italian National Institute of Astrophysics (INAF), is currently developing a scientific and technological SST dual-mirror end-to-end prototype named ASTRI SST-2M. It is a 4-meter class telescope; it adopts an aplanatic, wide-field, double-reflection optical layout in a Schwarzschild-Couder configuration. The ASTRI SST-2M telescope structure and mirrors have been already installed at the INAF observing station at Serra La Nave, on Mt. Etna (Sicily, Italy).
In this contribution we report about the on-site deployment and the latest results on the opto-mechanical performance test conducted soon after the telescope installation
As an example, we describe the results obtained measuring the primary mirror segments of the Cherenkov prototypal telescope manufactured by the Italian National Institute for Astrophysics in the context of the ASTRI Project. This specific case is challenging because the segmentation of the polynomial primary mirror lead to individual mirrors with deviations from the spherical optical design up to a few millimeters.
The aim of this article is to report the progress of the two telescope projects prototyping telescope structures and cameras for the Small Size Telescopes for CTA. After a discussion of the CTA project and its scientific objectives, the performance of the SC design is described, with focus on the specific designs of SST-GATE and ASTRI telescopes. The design of both prototypes and their progress is reported in the current prototyping phase. The designs of Cherenkov cameras, CHEC and ASTRI, to be mounted on these telescopes are discussed and progresses are reported.
The next generation of Imaging Atmospheric Cherenkov Telescope will explore the uppermost end of the Very High Energy domain up to about few hundreds of TeV with unprecedented sensitivity, angular resolution and imaging quality.
To this end, the Italian National Institute of Astrophysics (INAF) is currently developing a scientific and technological telescope prototype for the implementation of the Cherenkov Telescope Array (CTA) observatory. The Italian ASTRI program foresees the full design, development, installation and calibration of a Small Size 4-meter class Telescope, adopting an aplanatic, wide-field, double-reflection optical layout in a Schwarzschild-Couder configuration.
In this paper we discuss about the technological solutions adopted for the telescope and for the mirrors. In particular we focus on the structural and electro-mechanical design of the telescope, now under fabrication. The results on the optical performance derived from mirror prototypes are here described, too.
Future high energy astrophysics missions will require high performance novel X-ray optics to explore the Universe beyond the limits of the currently operating Chandra and Newton observatories. Innovative optics technologies are therefore being developed and matured by the European Space Agency (ESA) in collaboration with research institutions and industry, enabling leading-edge future science missions.
Silicon Pore Optics (SPO) [1 to 21] and Slumped Glass Optics (SGO) [22 to 29] are lightweight high performance X-ray optics technologies being developed in Europe, driven by applications in observatory class high energy astrophysics missions, aiming at angular resolutions of 5” and providing effective areas of one or more square meters at a few keV.
This paper reports on the development activities led by ESA, and the status of the SPO and SGO technologies, including progress on high performance multilayer reflective coatings [30 to 35]. In addition, the progress with the X-ray test facilities and associated beam-lines is discussed [36].
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