Experimental Astronomy最新文献

In the framework of the ALOHA (Astronomical Light Optical Hybrid Analysis) project, dedicated to high resolution imaging in the L-band using optical fibre and nonlinear optics, we have implemented a servo controlled hectometric outdoor fibre link between two telescopes and the recombination beam facility of the CHARA telescope array. A two-stage servo system using optical fibre modulator, fibre delay line, and a metrology laser at 1064 nm allows to stabilise the optical path difference within 3 nm RMS over a 3000 s record. Using an internal source at 810 nm, the signal-to-noise ratio of the fringe modulation peak is enhanced by a factor better than two when the servo control is switched on. This study can be also considered as a seminal work towards very long base fibre linked telescope arrays and allows to scale the perturbative environment of an outdoor fibre link.

The specific problem considered is the number of radial velocity measurements required to obtain good estimates of physical parameters of binary star. It is assumed that observations are made at random binary phases. The loss of information due to poor phase coverage is explored, and a suggested limit on the largest acceptable gap introduced. The statistical distribution of maximum gap lengths can then be used to specify the minimum number of velocity measurements to obtain good phase coverage with a specified confidence limit. The effects of non-zero orbital eccentricity are discussed, as are the ramifications of having multiple binary targets. The theory is also applicable to the characterisation of the radial velocity curves induced by exoplanets on their host stars, provided that the periods and eccentricities are known (from e.g. transit observations).

Large scale Radio Telescopes for Radio Astronomy highly depend on the availability of large (digital) processing capacities for imaging. Estimates concerning power efficiency for future Radio Telescopes lead to anticipated power consumption numbers beyond feasibility. To reduce the power budget, the use of approximate multipliers within the correlator is explored. A baseband equivalent executable model of a radio synthesis telescope is constructed to assess the effects of approximate multipliers. Besides ideal multipliers with floating point accuracy, the use of accurate 8-bit multipliers and 4 different types of approximate multipliers is explored. For each of these multipliers, the energy efficiency of an individual multiplier is known and used to determine the energy efficiency improvement of a correlator when using approximate multipliers. The effects of approximation are quantified by 3 metrics (Signal-to-Noise-Ratio (SNR), Spurious-Free-Dynamic-Range (SFDR) and Root-Mean-Square (RMS) level) derived from maps constructed by the executable model based on an empty sky with only a single point source. This is considered to be the worst case scenario. For illustration purposes, a more realistic input is processed by the model as well. The metrics have been determined based on different SNR levels at the input of each antenna element. For input SNR levels up to 10 dB, all types of approximate multipliers used in this paper can be exploited to improve energy efficiency of correlators, leading to a maximum energy reduction of 19 %. For input SNR values up to 30 dB an energy improvement up to 12 % can be achieved. These percentages are based on implementations in a 40nm low power IC technology at 1 GHz.

We report on results of the on-ground X-ray calibration of the Lobster Eye Imager for Astronomy (LEIA), an experimental space wide-field (18.6 (times ) 18.6 square degrees) X-ray telescope built from novel lobster eye micro-pore optics. LEIA was successfully launched on July 27, 2022 onboard the SATech-01 satellite. To achieve full characterisation of its performance before launch, a series of tests and calibrations have been carried out at different levels of devices, assemblies and the complete module. In this paper, we present the results of the end-to-end calibration campaign of the complete module carried out at the 100-m X-ray Test Facility at the Institute of High-energy Physics, Chinese Academy of Sciences (CAS). The Point Spread Function (PSF), effective area and energy response of the detectors were measured in a wide range of incident directions at several characteristic X-ray line energies. Specifically, the distributions of the PSF and effective areas are roughly uniform across the FoV, in large agreement with the prediction of lobster-eye optics. The mild variations and deviations from the prediction of idealized, perfect lobster-eye optics can be understood to be caused by the imperfect shapes and alignment of the micro-pores as well as the obscuration of incident photons by the supporting frames, which can be well reproduced by Monte Carlo simulations. The spatial resolution of LEIA defined by the full width at half maximum (FWHM) of the focal spot ranges from (textbf{4}) to (textbf{8}) arc minutes with a median of (mathbf{5.7}) arcmin. The measured effective areas are in range of (mathbf{2-3}~mathbf {cm^2}) at (mathbf{sim })1.25 keV across the entire FoV, and its dependence on photon energy is also in large agreement with simulations. The gains of the four complementary metal-oxide semiconductor (CMOS) sensors are in range of (mathbf{6.5-6.9}~mathbf {eV/DN}), and the energy resolutions in the range of (mathbf{sim 120 - 140}) eV at (mathbf{1.25}) keV and (mathbf{sim 170-190}) eV at (mathbf{4.5}) keV. These calibration results have been ingested into the first version of calibration database (CALDB) and applied to the analysis of the scientific data acquired by LEIA. This work paves the way for the calibration of the Wide-field X-Ray Telescope (WXT) flight model modules of the Einstein Probe (EP) mission.

This study addresses the complexity and importance of developing a method of calibrating digital observations of meteor spectra with all-sky cameras. It aims to present novel approaches to spectral sensitivity, atmospheric extinction and flat-field corrections. Images of a known line emission spectrum were captured at various positions within the field of view using a camera with a fish-eye lens and plastic holographic grating. The flat-field correction was separated into a wavelength-independent and wavelength-dependent component, both dependent on the position of the spectral line in the field of view (FoV). Total profile intensities of spectra obtained from the images were compared throughout the spectral range at different positions in the FoV. The flat-field was constructed by fitting those dependencies with high-degree polynomial functions. Using a simplified atmospheric model, a novel approach was constructed to determine the atmospheric extinction curve throughout the spectral range, allowing it to be separately considered from the spectral sensitivity which was previously not the case. A comparison of the newly developed and previously used methodology was tested on several meteor spectra of the same meteor captured from different stations of the European Fireball Network. It revealed a significantly improved correspondence of the analysed spectra in the part of the spectral range unaffected by the limitations imposed by the newly developed methodology. Failing to follow the correct calibration methodology precisely may introduce varying degrees of uncertainty in computations of elemental abundances and other physical properties, depending on the equipment’s specific effect magnitude.

The transition-edge sensor (TES) as a type of low-temperature superconducting detector offers superior sensitivity due to its low thermal noise. In this work, we present a prototype TES bolometer designed for cosmic microwave background (CMB) polarization measurements. This TES is made of aluminum doped with a low concentration of manganese (2000 ppm by atomic percentage), and is deposited on the SiNx membrane which connects to the silicon substrate via narrow legs. In order to calculate its electrothermal parameters we have performed dark characterizations, which include measuring voltage-current (IV) curve at different bath temperatures, square-wave time response at various bias voltages, and noise level. This TES bolometer shows a noise equivalent power (NEP) of about (5times 10^{-17}) W/(sqrt{textrm{Hz}}), which meets the requirement of CMB observation. However, its saturation power is smaller and time constant is larger than what are expected. We have analyzed the reasons and will make corresponding improvements in our future work.

Aditya-L1 is the first Indian space mission to explore the Sun and solar atmosphere with seven multi-wavelength payloads, with Visible Emission Line Coronagraph (VELC) being the prime payload. It is an internally occulted coronagraph with four channels to image the Sun at 5000 Å  in the field of view 1.05 - 3 (varvec{R}_{odot }), and to pursue spectroscopy at 5303 Å, 7892 Å  and 10747 Å  channels in the FOV (1.05 - 1.5 (varvec{R}_{odot })). In addition, spectropolarimetry is planned at 10747 Å  channel. Therefore, VELC has three sCMOS detectors and one InGaAs detector. In this article, we aim to describe the technical details and specifications of the detectors achieved by way of thermo-vacuum calibration at the CREST campus of the Indian Institute of Astrophysics, Bangalore, India. Furthermore, we report the estimated conversion gain, full-well capacity, and readout noise at different temperatures. Based on the numbers, it is thus concluded that it is essential to operate the sCMOS detectors and InGaAs detector at (varvec{-5^circ }) and (varvec{-17^{circ }}) C, respectively, at the spacecraft level.

The Low Energy X-ray telescope (LE) is one of the main instruments of the Insight-Hard X-ray Modulation Telescope (Insight-HXMT), the first Chinese X-ray astronomical satellite. The scientific objectives of LE focus on scanning and pointed observations of the X-ray sources in the soft X-ray band (0.7–13 keV). LE consists of three detector boxes (LEDs) and an electric control box (LEB). The LEB is composed of data handling unit, monitoring unit, and power distribution unit, with functions including data processing, communication, monitoring, power supply, and distribution. All the functions designed in the LEB were verified during the operation in orbit. To improve the efficiency of astronomical observations and reliability of LE, onboard data processing is designed in the LEB. The results of onboard data processing are immediately transmitted to the ground as important housekeeping data and are verified by comparing them with the processing results of the data transmitted to the ground. In the six years since launch, the LEB has performed well, operated smoothly, and met all expected requirements. The LEB has participated in numerous scientific observations, transmitted a large amount of scientific data, and obtained several observational results.

The Yarkovsky drift represents the semi-major axis variation of a celestial body due to the Yarkovsky effect. This thermodynamic effect acts more significantly on bodies with a diameter between (approx 10 ,text {m}) and (approx 30 ,text {km}). Therefore, the orbits of many minor bodies of the solar system are affected: knowing the value of the Yarkovsky drift can be crucial to accurately predict their positions, especially if the asteroids are Near Earth Asteroids (NEAs) and there may be a non-zero impact probability with the Earth. The direct computation of this effect is not easily achieved due to the scarce availability of NEAs physical information. Thus, the more promising method to estimate the Yarkovsky effect is through an orbital fit using seven parameters, the six orbital elements and a seventh parameter accounting for non-gravitational interactions. In this paper, we show the analysis of 1262 NEAs with Signal-to-Noise Ratio (SNR) greater or equal 2, of which 279 have the parameter S (absolute ratio between the Yarkovsky drift and its expected value) less than 1.5 and are therefore more reliable. Among these, 91 are not present in the literature, thus represent new Yarkovsky drift detections. Furthermore, we used our results to estimate the ratio of the retrograde over prograde rotators and to validate the dependence of the Yarkovsky drift from the diameter, da/dt (approx D^{-1}).

State-of-the-art 19th century spectroscopy led to the discovery of quantum mechanics, and 20th century spectroscopy led to the confirmation of quantum electrodynamics. State-of-the-art 21st century astrophysical spectrographs, especially ANDES at ESO’s ELT, have another opportunity to play a key role in the search for, and characterization of, the new physics which is known to be out there, waiting to be discovered. We rely on detailed simulations and forecast techniques to discuss four important examples of this point: big bang nucleosynthesis, the evolution of the cosmic microwave background temperature, tests of the universality of physical laws, and a real-time model-independent mapping of the expansion history of the universe (also known as the redshift drift). The last two are among the flagship science drivers for the ELT. We also highlight what is required for the ESO community to be able to play a meaningful role in 2030s fundamental cosmology and show that, even if ANDES only provides null results, such ‘minimum guaranteed science’ will be in the form of constraints on key cosmological paradigms: these are independent from, and can be competitive with, those obtained from traditional cosmological probes.