Number and Distribution of Fiducial Fibres in a Spectroscopic Survey Telescope

To date, the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) has been in operation for 12 years. To improve the telescope’s astronomical observation accuracy, the original open-loop fibre positioning system of LAMOST is in urgent need of upgrading. The upgrade plan is to locate several fibre view cameras (FVCs) around primary mirror B to build a closed-loop feedback control system. The FVCs are ~20 m from the focal surface. To reduce a series of errors when the cameras detect the positions of the optical fibres, we designed fiducial fibres on the focal surface to be fiducial points for the cameras. Increasing the number of fiducial fibres can improve the detection accuracy of the FVC system, but it will also certainly reduce the number of fibre positioners that can be used for observation. Therefore, the focus of this paper is how to achieve the quantity and distribution that meet the requirements of system detection. In this paper, we introduce the necessity of using fiducial fibres, propose a method for selecting their number, and present several methods for assessing the uniformity of their distribution. Finally, we use particle swarm optimization to find the best distribution of fiducial fibres.

Thermomechanical performance of carbon fiber reinforced polymer synchronizer friction liners

To improve the ability of a thermomechanical simulation model for carbon fiber reinforced polymer lined synchronizers to predict synchronization performance and reliability, temperature dependent material data for the specific carbon fiber reinforced polymer lining is needed. The compressive modulus, coefficient of thermal expansion, specific heat and thermal conductivity are determined experimentally. The effect of each material property on the focal surface temperature is analyzed, and it is shown that the compressive modulus has the largest influence for all analyzed load cases. Physical tests show that surface hot spots begin to appear at a simulated focal surface temperature of 200[Formula: see text]C, while performance degradation occurs at a simulated focal surface temperature of 230[Formula: see text]C–250[Formula: see text]C.

Pre-flight qualification tests of the Mini-EUSO telescope engineering model

Mini-EUSO is part of the JEM-EUSO program and operates on board the International Space Station (ISS). It is a UV-telescope with single-photon counting capability looking at nighttime downwards to the Earth through a nadir-facing UV-transparent window. As part of the pre-flight tests, the Mini-EUSO engineering model, a telescope with 1/9 of the original focal surface and a lens of 2.5 cm diameter, has been built and tested. Tests of the Mini-EUSO engineering model have been made in laboratory and in open-sky conditions. Laboratory tests have been performed at the TurLab facility, located at the Physics Department of the University of Turin, equipped with a rotating tank containing different types of materials and light sources. In this way, the configuration for the observation of the Earth from space was emulated, including the Mini-EUSO trigger schemes. In addition to the qualification and calibration tests, the Mini-EUSO engineering model has also been used to evaluate the possibility of using a JEM-EUSO-type detector for applications such as observation of space debris. Furthermore, observations in open-sky conditions allowed the studies of natural light sources such as stars, meteors, planets, and artificial light sources such as airplanes, satellites reflecting the sunlight, and city lights. Most of these targets could be detected also with Mini-EUSO. In this paper, the tests in laboratory and in open-sky conditions are reported, as well as the obtained results. In addition, the contribution that such tests provided to foresee and improve the performance of Mini-EUSO on board the ISS is discussed.

Analysis of meteors observed in the UV by the Mini-EUSO telescope onboard the International Space Station

<p>During its first six months of operations onboard the Zvezda module of the International Space Station, the Mini-EUSO wide-field telescope detected more than two thousand meteors in approximately 40 hours of data taking. Mini-EUSO observes the Earth’s atmosphere in the UV range (290 – 430 nm) with a field of view of about 44° x 44° through a nadir-facing, UV-transparent window with a focal surface of 48 x 48 pixels and a resolution of about 6.3 km on ground. While temporal resolution and triggering are at the timescales of 2.5 μs to potentially record UHECR showers and TLEs, Mini-EUSO performs a continuous monitoring of the UV emission at a 40.96 ms timescale, where meteors are recorded. We developed an analysis pipeline able to offline detect, track and characterize meteor events and subsequently compute their physical parameters, such as tangential speed, magnitude, duration and trajectory azimuth. In this contribution, we present the implemented reduction methods and the results of the analysis of the sample, providing comparisons with existing databases of meteors observed in the optical band.</p>

Observation of ELVES from the International Space Station with the Mini-EUSO telescope

<p>Mini-EUSO is a telescope that observes the Earth from the International Space Station by recording ultraviolet emissions (290 ÷ 430 nm) of cosmic, atmospheric and terrestrial origin with a field of view of 44◦, a spatial resolution of 6.3 km and a temporal resolution of 2.5 mus.</p><p>The instrument is based on an optical system composed of two Fresnel lenses and a focal surface composed of 36 multi-anode photomultiplier tubes, 64 channels each, for a total of 2304 channels with single photon counting sensitivity.</p><p>Mini-EUSO is a UV telescope launched in 2019   and observing the Earth from the inside the Russian Zvezda module, through a nadir-facing UV-transparent.</p><p>It is composed of a Fresnel optics (25 cm diameter, 44 deg field of view) and a Multi Anode Photomultiplier focal surface (2304 pixels, 6km on the surface) with a single-photon counting capability and a sampling rate of 400kHz.</p><p>Its scientific objectives include the search for ultra-high energy cosmic rays (E>1e21eV), the study of  meteors and search for interstellar objects and Strange Quark Matter, the  mapping   of the Earth's night-time ultraviolet emissions, the search for space debris.</p><p>The characteristcs of the detector make it also well suited for the detection of TLEs, especially ELVES and the study of its development to extract spatial and temporal evolution.  In this article we will focus our attention on the observation of single and multi-ringed elves.</p>

Effect of Fiber Optic Plate on Centroid Locating Accuracy of Monocentric Imager

We propose a method for obtaining the centroid locating accuracy (CLA) of a monocentric imager with a fiber optic plate (FOP) as a relay image transmission element in order to reduce the loss of CLA due to the addition of FOP. We constructed a two-stage image transmission coupling model of spherical focal surface (FOP) image sensor. By analyzing the influences of FOP parameters, including the fill factor and the fiber diameter, and FOP in-plane displacements, including rotation and translation on CLA, the loss of the lowest CLA that the monocentric imager can withstand caused by the addition of the FOP was reduced by 20%.