Subjects -> INSTRUMENTS (Total: 63 journals)
 Showing 1 - 16 of 16 Journals sorted alphabetically Annali dell'Istituto e Museo di storia della scienza di Firenze Applied Mechanics Reviews       (Followers: 27) Bulletin of Social Informatics Theory and Application       (Followers: 1) Computational Visual Media       (Followers: 4) Devices and Methods of Measurements Documenta & Instrumenta - Documenta et Instrumenta EPJ Techniques and Instrumentation European Journal of Remote Sensing       (Followers: 9) Experimental Astronomy       (Followers: 39) Flow Measurement and Instrumentation       (Followers: 18) Geoscientific Instrumentation, Methods and Data Systems       (Followers: 4) Geoscientific Instrumentation, Methods and Data Systems Discussions       (Followers: 1) IEEE Journal on Miniaturization for Air and Space Systems       (Followers: 2) IEEE Sensors Journal       (Followers: 103) IEEE Sensors Letters       (Followers: 3) IJEIS (Indonesian Journal of Electronics and Instrumentation Systems)       (Followers: 3) Imaging & Microscopy       (Followers: 9) InfoTekJar : Jurnal Nasional Informatika dan Teknologi Jaringan Instrumentation Science & Technology       (Followers: 7) Instruments and Experimental Techniques       (Followers: 1) International Journal of Applied Mechanics       (Followers: 7) International Journal of Instrumentation Science       (Followers: 40) International Journal of Measurement Technologies and Instrumentation Engineering       (Followers: 2) International Journal of Metrology and Quality Engineering       (Followers: 4) International Journal of Remote Sensing       (Followers: 278) International Journal of Remote Sensing Applications       (Followers: 45) International Journal of Sensor Networks       (Followers: 4) International Journal of Testing       (Followers: 1) Journal of Applied Remote Sensing       (Followers: 83) Journal of Astronomical Instrumentation       (Followers: 3) Journal of Instrumentation       (Followers: 32) Journal of Instrumentation Technology & Innovations       (Followers: 2) Journal of Medical Devices       (Followers: 5) Journal of Medical Signals and Sensors       (Followers: 3) Journal of Optical Technology       (Followers: 5) Journal of Sensors and Sensor Systems       (Followers: 11) Journal of Vacuum Science & Technology B       (Followers: 3) Jurnal Informatika Upgris Measurement : Sensors       (Followers: 3) Measurement and Control       (Followers: 36) Measurement Instruments for the Social Sciences Measurement Science and Technology       (Followers: 7) Measurement Techniques       (Followers: 3) Medical Devices & Sensors Medical Instrumentation Metrology and Instruments / Метрологія та прилади Metrology and Measurement Systems       (Followers: 6) Microscopy       (Followers: 8) Modern Instrumentation       (Followers: 50) Optoelectronics, Instrumentation and Data Processing       (Followers: 4) PFG : Journal of Photogrammetry, Remote Sensing and Geoinformation Science Photogrammetric Engineering & Remote Sensing       (Followers: 29) Remote Sensing       (Followers: 55) Remote Sensing Applications : Society and Environment       (Followers: 8) Remote Sensing of Environment       (Followers: 93) Remote Sensing Science       (Followers: 24) Review of Scientific Instruments       (Followers: 22) Science of Remote Sensing Sensors and Materials       (Followers: 2) Solid State Nuclear Magnetic Resonance       (Followers: 3) Standards Transactions of the Institute of Measurement and Control       (Followers: 13) Труды СПИИРАН
Similar Journals
 Experimental AstronomyJournal Prestige (SJR): 0.908 Citation Impact (citeScore): 2Number of Followers: 39      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1572-9508 - ISSN (Online) 0922-6435 Published by Springer-Verlag  [2655 journals]
• AEDGE: Atomic experiment for dark matter and gravity exploration in space
• Abstract: This article contains a summary of the White Paper submitted in 2019 to the ESA Voyage 2050 process, which was subsequently published in EPJ Quantum Technology (AEDGE Collaboration et al. EPJ Quant. Technol. 7,6 2020). We propose in this White Paper a concept for a space experiment using cold atoms to search for ultra-light dark matter, and to detect gravitational waves in the frequency range between the most sensitive ranges of LISA and the terrestrial LIGO/Virgo/KAGRA/INDIGO experiments. This interdisciplinary experiment, called Atomic Experiment for Dark Matter and Gravity Exploration (AEDGE), will also complement other planned searches for dark matter, and exploit synergies with other gravitational wave detectors. We give examples of the extended range of sensitivity to ultra-light dark matter offered by AEDGE, and how its gravitational-wave measurements could explore the assembly of super-massive black holes, first-order phase transitions in the early universe and cosmic strings. AEDGE will be based upon technologies now being developed for terrestrial experiments using cold atoms, and will benefit from the space experience obtained with, e.g., LISA and cold atom experiments in microgravity.
PubDate: 2021-03-12

• All-sky visible and near infrared space astrometry
• Abstract: The era of all-sky space astrometry began with the Hipparcos mission in 1989 and provided the first very accurate catalogue of apparent magnitudes, positions, parallaxes and proper motions of 120 000 bright stars at the milliarcsec (or milliarcsec per year) accuracy level. Hipparcos has now been superseded by the results of the Gaia mission. The second Gaia data release contained astrometric data for almost 1.7 billion sources with tens of microarcsec (or microarcsec per year) accuracy in a vast volume of the Milky Way and future data releases will further improve on this. Gaia has just completed its nominal 5-year mission (July 2019), but is expected to continue in operations for an extended period of an additional 5 years through to mid 2024. Its final catalogue to be released $$\sim$$ 2027, will provide astrometry for $$\sim$$ 2 billion sources, with astrometric precisions reaching 10 microarcsec. Why is accurate astrometry so important' The answer is that it provides fundamental data which underpin much of modern observational astronomy as will be detailed in this White Paper. All-sky visible and Near-InfraRed (NIR) astrometry with a wavelength cutoff in the K-band is not just focused on a single or small number of key science cases. Instead, it is extremely broad, answering key science questions in nearly every branch of astronomy while also providing a dense and accurate visible-NIR reference frame needed for future astronomy facilities.
PubDate: 2021-03-11

• The Ariel Instrument Control Unit
• Abstract: Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey mission (Tinetti 2019; Puig et al. 2018; Pascale et al. 2018), has been selected in March 2018 by ESA for the fourth medium-class mission (M4) launch opportunity of the Cosmic Vision Program, with an expected lift off in late 2028. It is the first mission dedicated to measuring the chemical composition and thermal structures of the atmospheres of hundreds of transiting exoplanets, enabling planetary science far beyond the boundaries of our own Solar System. Its Payload (P/L) (Eccleston and Tinetti 2018; Eccleston et al. 2017; Middleton et al. 2019), has been designed to perform transit spectroscopy from space during primary and secondary planetary eclipses in order to achieve a large unbiased survey concerning the nature of exoplanets atmospheres and their interiors, to determine the key factors affecting the formation and evolution of planetary systems (Tinetti et al. 2017, 2018). Ariel will observe hundreds of warm and hot transiting gas giants, Neptunes and super-Earths around a wide range of host star types, targeting planets hotter than $$\sim$$ 600 K to take advantage of their well-mixed atmospheres. It will exploit primary and secondary transit spectroscopy in the 1.10 to 7.80 μm spectral range and broad-band photometry in the optical (0.50 - 0.80 μm) and Near IR (0.80 - 1.10 μm) . One of the two instruments of the Ariel Payload is the Fine Guidance System (FGS), including three photometric channels (two used for guiding as well as science) between 0.5-1.1 μm plus a low resolution NIR spectrometer for 1.1-1.95 μm range. Along with FGS an IR Spectrometer (AIRS) (Amiaux et al. 2017) is foreseen, providing low-resolution spectroscopy in two IR channels: Channel 0 (CH0) for the 1.95 − 3.90 μm band and Channel 1 (CH1) for the 3.90 − 7.80 μm range. Finally, an Active Cooler System (ACS) including a Ne Joule-Thomson cooler is adopted to provide active cooling capability to the AIRS detectors working at cryogenic temperatures. AIRS is located at the intermediate focal plane of the telescope and common optical system and it hosts two HgCdTe-based hybrid IR detectors and two cold front-end electronics (CFEE) for detectors control and readout. Each CFEE is driven by a Detector Control Unit (DCU) part of AIRS but hosted within and managed by the Instrument Control Unit (ICU) of the Payload (Focardi et al. 2018). ICU is a warm unit residing into the S/C Service Module (SVM) and it is based on a cold redundant configuration involving the Power Supply Unit (PSU) and the Commanding and Data Processing Unit (CDPU) boards; both DCUs are instead cross-strapped and can be managed by the nominal or the redundant (PSU+CDPU) chain. ICU is in charge of AIRS management, collecting scientific and housekeeping (HK) telemetries from the spectrometer and HK from the telescope (temperatures readings), the P/L Optical Bench (OB) and other Subsystems (SS), thanks to a warm slave unit (TCU, Telescope Control Unit) interfaced to the ICU. Science and HK telemetries are then forwarded to the S/C, for temporary storage, before sending them to Ground. Here we describe the status of the ICU design at the end of B1 Phase, prior to the Mission Adoption Review (MAR) by ESA, with some still open architectural choices to be addressed and finalised once selected the ICU industrial Prime contractor.
PubDate: 2021-03-11

• Detecting the gravito-magnetic field of the dark halo of the Milky Way -
• Abstract: We propose to locate transponders and atomic clocks in at least three of the Lagrange points of the Sun-Earth pair, with the aim of exploiting the time of flight asymmetry between electromagnetic signals travelling in opposite directions along polygonal loops having the Lagrange points at their vertices. The asymmetry is due to the presence of a gravito-magnetic field partly caused by the angular momentum of the Sun, partly originating from the angular momentum of the galactic dark halo in which the Milky Way is embedded. We list also various opportunities which could be associated with the main objective of this Lagrange Dark Halo Detector (LaDaHaD).
PubDate: 2021-03-09

• A preliminary design of the magnetic diverter on-board the eXTP
observatory
• Abstract: Charged particles in the space environment can degrade the scientific performances of X-ray detectors in astronomical telescopes. An efficient countermeasure is to place a magnetic diverter at the exit pupil of optics to deflect charged particles away from the sensitive detection area. In this work, we have performed a preliminary design of the magnetic diverter on-board the enhanced X-ray Timing and Polarimetry (eXTP) observatory. It relies on a Monte Carlo method via the GEANT4 toolkit to simulate the mirror responses to charged particles, using the single scattering physics for electrons and the elastic Remizovich physics for protons. It also implements a numerical method to calculate magnetic fields generated by an assembly of permanent magnets and its impact on the trajectories of charged particles. The compact calculation scheme provides efficient access to the background level estimation given the certain radiation environment, which enables the verification of the diverter configuration with the scientific requirements.
PubDate: 2021-03-09

• Determination of stellar parameters for Ariel targets: a comparison
analysis between different spectroscopic methods
• Abstract: Ariel has been selected as the next ESA M4 science mission and it is expected to be launched in 2028. During its 4-year mission, Ariel will observe the atmospheres of a large and diversified population of transiting exoplanets. A key factor for the achievement of the scientific goal of Ariel is the selection strategy for the definition of the input target list. A meaningful choice of the targets requires an accurate knowledge of the planet hosting star properties and this is necessary to be obtained well before the launch. In this work, we present the results of a bench-marking analysis between three different spectroscopic techniques used to determine stellar parameters for a selected number of targets belonging to the Ariel reference sample. We aim to consolidate a method that will be used to homogeneously determine the stellar parameters of the complete Ariel reference sample. Homogeneous, accurate and precise derivation of stellar parameters is crucial for characterising exoplanet-host stars and in turn is a key factor for the accuracy of the planet properties.
PubDate: 2021-03-05

• ExoSim: the Exoplanet Observation Simulator
• Abstract: A new generation of exoplanet research beckons and with it the need for simulation tools that accurately predict signal and noise in transit spectroscopy observations. We developed ExoSim: an end-to-end simulator that models noise and systematics in a dynamical simulation. ExoSim improves on previous simulators in the complexity of its simulation, versatility of use and its ability to be generically applied to different instruments. It performs a dynamical simulation that can capture temporal effects such as correlated noise and systematics on the light curve. It has also been extensively validated, including against real results from the Hubble WFC3 instrument. We find ExoSim is accurate to within 5% in most comparisons. ExoSim can interact with other models which simulate specific time-dependent processes. A dedicated star spot simulator allows ExoSim to produce simulated observations that include spot and facula contamination. ExoSim has been used extensively in the Phase A and B design studies of the ARIEL mission, and has many potential applications in the field of transit spectroscopy.
PubDate: 2021-03-05

• Thermoelastic evaluation of the payload module of the ARIEL mission
• Abstract: The ARIEL mission is a space project consisting of a spacecraft with the goal of detecting exoplanets and observing the characteristics of their atmospheres. One of the main sub-systems of the payload is the telescope that must operate under cryogenic conditions to guarantee its adequate performance and the mission success. One of the critical aspects in the development of a space telescope is the stability and the related analyses required to evaluate the degree of deformation of the system under all environmental conditions, with special emphasis on the different and extreme temperature ranges reached during the mission. This assessment involves the close collaboration between three different disciplines: thermal, structural and optical design. This paper describes the work done in the ARIEL project in the field of the structural stability analysis, showing the process to achieve reliable and accurate results. The main novelty of this work is the validation of the structural model to achieve the required level of precision in the displacements fields calculated numerically to provide reliable and accurate deformations that will allow the assessment of the thermoelastic effects on the optical performance of the main telescope. The results of the structural simulations show how the telescope assembly is deformed under the different analysed conditions, which will allow the design of compensation mechanisms to mitigate these effects.
PubDate: 2021-02-19

• A chemically etched corrugated feedhorn array for D-band CMB observations
• Abstract: We present the design, manufacturing, and testing of a 37-element array of corrugated feedhorns for Cosmic Microwave Background CMB) measurements between 140 and 170 GHz. The array was designed to be coupled to Kinetic Inductance Detector arrays, either directly (for total power measurements) or through an orthomode transducer (for polarization measurements). We manufactured the array in platelets by chemically etching aluminum plates of 0.3 mm and 0.4 mm thickness. The process is fast, low-cost, scalable, and yields high-performance antennas compared to other techniques in the same frequency range. Room temperature electromagnetic measurements show excellent repeatability with an average cross polarization level about − 20 dB, return loss about − 25 dB, first sidelobes below − 25 dB and far sidelobes below − 35 dB. Our results qualify this process as a valid candidate for state-of-the-art CMB experiments, where large detector arrays with high sensitivity and polarization purity are of paramount importance in the quest for the discovery of CMB polarization B-modes.
PubDate: 2021-02-12

• CAPTURE: a continuum imaging pipeline for the uGMRT
• Abstract: We present the first fully automated pipeline for making images from the interferometric data obtained from the upgraded Giant Metrewave Radio Telescope (uGMRT) called CAsa Pipeline-cum-Toolkit for Upgraded Giant Metrewave Radio Telescope data REduction - CAPTURE. It is a python program that uses tasks from the NRAO Common Astronomy Software Applications (CASA) to perform the steps of flagging of bad data, calibration, imaging and self-calibration. The salient features of the pipeline are: i) a fully automatic mode to go from the raw data to a self-calibrated continuum image, ii) specialized flagging strategies for short and long baselines that ensure minimal loss of extended structure, iii) flagging of persistent narrow band radio frequency interference (RFI), iv) flexibility for the user to configure the pipeline for step-by-step analysis or special cases and v) analysis of data from the legacy GMRT. CAPTURE is available publicly on github (https://github.com/ruta-k/uGMRT-pipeline, release v1.0.0). The primary beam correction for the uGMRT images produced with CAPTURE is made separately available at https://github.com/ruta-k/uGMRTprimarybeam. We show examples of using CAPTURE on uGMRT and legacy GMRT data. In principle, CAPTURE can be tailored for use with other radio interferometric data.
PubDate: 2021-02-01

• Expanding the field of view: station design for the AAMID SKA radio
telescope
• Abstract: The new generation radio telescopes, such as the Square Kilometre Array (SKA) currently under construction, will use aperture array, technology for the low frequency regime. For SKA2, the second phase scheduled after the realization of SKA1, aperture array technology is proposed up to 1.4 GHz. The antenna element count, as well as the signal processing cost, of such a system will be high. In this paper we analyze an option to reduce the number of antenna elements by making the array sparse. To reduce the signal processing cost Fast Fourier Transform Beamforming is proposed and it performance is compared to traditional beamforming. To guide the system design a Figure of Merit for the performance cost ratio is proposed and evaluated for various levels of sparsity of the antenna array. It is concluded that, for equal front-end and back-end costs, a sparse system is only marginally better than a dense system. Only when signal processing cost is significantly lower than the front-end hardware, a sparse system can be competitive.
PubDate: 2021-02-01

• First light of SOVAG, a spectrograph for visible and near-infrared
observation of asteroids
• Abstract: Spectroscopy in the visible and near-infrared has been the main tool for characterising the surface properties of asteroids for decades. For a given target, the two wavelength regimes are usually acquired by different telescopes/instruments, separated by years. They are seldom obtained simultaneously. However, it is not straightforward to combine datasets from different sources because of the spectral reddening linked with phase angle. We present the first-light result of SOVAG (Spectrographe pour l’Observations dans le Visible et infrarouge proche d’Astéroïdes Géocroiseurs), a new concept of spectrograph for observing both wavelength ranges at the same time. It is compact in design and portable. We developed a prototype of this instrument between 2016 and 2018. In July 2018, we mounted SOVAG on the 1 m-telescope in Pic du Midi observatory (for which it was designed) and conducted its on-sky first light experiment. We present a spectrum of (4) Vesta which demonstrates the reliability of observations and the accuracy of the calibration. Ongoing development will allow us to push observation-limits toward fainter objects.
PubDate: 2021-02-01

• Wide band, tunable gamma-ray lenses
• Abstract: A new concept for an astronomical telescope in the MeV energy band is presented. The concept builds on Bragg diffraction in crystals, which has been discussed in the past, but so far a design with good sensitivity over a wide energy range has seemed out of reach. In this paper we point out that if we find ways to adjust, in orbit, the individual tilt of all the crystals in the lens this would allow one single lens to cover with excellent efficiency the full range of energies from 200 keV to 2.5 MeV in a few observation steps. Secondly, we note that the use of lenses with double crystal layers will increase the photon collection significantly. In an accompanying paper we describe our overall lens design in more detail and present our first prototype tilt adjustment pedestal for use with the individual lens facets.
PubDate: 2021-02-01

• An upper limit calculator (UL-CALC) for undetected extended sources with
PubDate: 2021-02-01
DOI: 10.1007/s10686-020-09692-7

• Experimental evaluation of complete safe coordination of astrobots for
Sloan Digital Sky Survey V
• Abstract: The data throughput of massive spectroscopic surveys in the course of each observation is directly coordinated with the number of optical fibers which reach their target. In this paper, we evaluate the safety and the performance of the astrobots coordination in SDSS-V by conducting various experimental and simulated tests. We illustrate that our strategy provides a complete coordination condition which depends on the operational characteristics of astrobots, their configurations, and their targets. Namely, a coordination method based on the notion of cooperative artificial potential fields is used to generate safe and complete trajectories for astrobots. Optimal target assignment further improves the performance of the used algorithm in terms of faster convergences and less oscillatory movements. Both random targets and galaxy catalog targets are employed to observe the coordination success of the algorithm in various target distributions. The proposed method is capable of handling all potential collisions in the course of coordination. Once the completeness condition is fulfilled according to initial configuration of astrobots and their targets, the algorithm reaches full convergence of astrobots. Should one assign targets to astrobots using efficient strategies, convergence time as well as the number of oscillations decrease in the course of coordination. Rare incomplete scenarios are simply resolved by trivial modifications of astrobots swarms’ parameters.
PubDate: 2020-12-19
DOI: 10.1007/s10686-020-09687-4

• Ground calibration of Solar X-ray Monitor on board the Chandrayaan-2
orbiter
• Abstract: Chandrayaan-2, the second Indian mission to the Moon, carries a spectrometer called the Solar X-ray Monitor (XSM) to perform soft X-ray spectral measurements of the Sun while a companion payload, CLASS, measures the fluorescence emission from the Moon. Together these two payloads will provide quantitative estimates of elemental abundances on the lunar surface. The XSM with its high time cadence and high energy resolution spectral measurements, is also expected to provide significant contributions to solar X-ray studies. For this purpose, the XSM employs a Silicon Drift Detector and carries out energy measurements of incident photons in the 1 – 15 keV range with a resolution of < 180 eV at 5.9 keV, over a wide range of solar X-ray intensities. Extensive ground calibration experiments have been carried out with the XSM using laboratory X-ray sources as well as X-ray beam-line facilities to determine the instrument response matrix parameters required to carry out quantitative spectral analysis. This includes measurements, under various observing conditions, of gain, spectral redistribution function, and effective area. The capability of the XSM to maintain its spectral performance at high incident flux as well as its dead-time and pile-up characteristics have also been investigated. The results of these ground calibration experiments of the XSM payload are presented in this article.
PubDate: 2020-11-25
DOI: 10.1007/s10686-020-09686-5

• Study of particle multiplicity of cosmic ray events using 2 m × 2 m
resistive plate chamber stack at IICHEP-Madurai
• Abstract: An experimental setup consisting of 12 layers of glass Resistive Plate Chambers (RPCs) of size 2 m × 2 m has been built at IICHEP-Madurai (9∘56 $$^{\prime }$$ 14.5 $$^{\prime \prime }$$ N 78∘0 $$^{\prime }$$ 47.9 $$^{\prime \prime }$$ E) to study the long term performance and stability of RPCs produced on a large scale in Indian industry. This setup has been collecting data triggered by the passage of charged particles. The measurement of the multiplicity of charged particles due to cosmic ray interactions are presented here. Finally, the results are compared with different hadronic models of the CORSIKA simulation.
PubDate: 2020-11-19
DOI: 10.1007/s10686-020-09685-6

• Simulations of orbital debris clouds due to breakup events and their
characterisation using the Murchison Widefield Array radio telescope
• Abstract: In this paper we consider the use of wide field of view radar sensors such as the Murchison Widefield Array (MWA), a low frequency radio telescope designed for astrophysics and cosmology, for rapid response observations of the debris clouds produced by collisions between objects in Earth orbit. With an increasing density of objects in Low Earth Orbit, including legacy assets used by the astronomy community over decades, the risk of new debris clouds forming is also increasing. The MWA constitutes a wide field, rapid response passive radar system and we explore its likely performance in the detection and characterisation of debris clouds. In general, astronomy facilities such as the MWA can play a role in protecting the space environment for the future. In order to undertake this work, we adapt the NASA EVOLVE 4.0 breakup model, utilising the EVOLVE outputs to produce representative dynamic debris clouds. We find that the MWA is likely to detect a large fraction (> 70%) of modelled debris cloud fragments for collision masses between 100 kg and 1000 kg for orbits in the lower part of LEO, if the MWA can achieve close to optimal detection sensitivity. Useful detection fractions are still achieved for more conservative assumptions. The detection fraction of fragments decreases as a function of altitude and inversely with collision mass. Encouragingly, we find that the wide field nature of the MWA allows the full evolving debris clouds to be observed in a single observation, with only ∼2% of the debris fragments escaping the sensitive portion of the field of view after 100 seconds, for all collision masses and altitudes. These results show that the MWA is an intrinsically useful facility for the rapid characterisation of debris clouds, but that work is required to achieve the data processing within an appropriate timeframe to provide rapid alerts.
PubDate: 2020-11-15
DOI: 10.1007/s10686-020-09684-7

• Technologies for tunable gamma-ray lenses
• Abstract: The tunable gamma-ray lens has turned out to be a promising alternative to the classical fixed-energy Laue-lenses discussed in the past. We describe here our development work on a miniature pedestal with one-axis tilt adjustment. We also outline our design for an optical system, capable of monitoring the alignment of the many crystals needed. An added benefit of the tunable crystal pedestal is that it relieves both the demands for high precision in the crystal mounting and the stringent requirements for long-term stability of the support platform on which the crystals are mounted. Moreover, mounting the individual crystals on separate pedestals facilitates the use of double layers of crystals.
PubDate: 2020-11-09
DOI: 10.1007/s10686-020-09683-8

• The CHEOPS mission
• Abstract: The CHaracterising ExOPlanet Satellite (CHEOPS) was selected on October 19, 2012, as the first small mission (S-mission) in the ESA Science Programme and successfully launched on December 18, 2019, as a secondary passenger on a Soyuz-Fregat rocket from Kourou, French Guiana. CHEOPS is a partnership between ESA and Switzerland with important contributions by ten additional ESA Member States. CHEOPS is the first mission dedicated to search for transits of exoplanets using ultrahigh precision photometry on bright stars already known to host planets. As a follow-up mission, CHEOPS is mainly dedicated to improving, whenever possible, existing radii measurements or provide first accurate measurements for a subset of those planets for which the mass has already been estimated from ground-based spectroscopic surveys. The expected photometric precision will also allow CHEOPS to go beyond measuring only transits and to follow phase curves or to search for exo-moons, for example. Finally, by unveiling transiting exoplanets with high potential for in-depth characterisation, CHEOPS will also provide prime targets for future instruments suited to the spectroscopic characterisation of exoplanetary atmospheres. To reach its science objectives, requirements on the photometric precision and stability have been derived for stars with magnitudes ranging from 6 to 12 in the V band. In particular, CHEOPS shall be able to detect Earth-size planets transiting G5 dwarf stars (stellar radius of 0.9R⊙) in the magnitude range 6 ≤ V ≤ 9 by achieving a photometric precision of 20 ppm in 6 hours of integration time. In the case of K-type stars (stellar radius of 0.7R⊙) of magnitude in the range 9 ≤ V ≤ 12, CHEOPS shall be able to detect transiting Neptune-size planets achieving a photometric precision of 85 ppm in 3 hours of integration time. This precision has to be maintained over continuous periods of observation for up to 48 hours. This precision and stability will be achieved by using a single, frame-transfer, back-illuminated CCD detector at the focal plane assembly of a 33.5 cm diameter, on-axis Ritchey-Chrétien telescope. The nearly 275 kg spacecraft is nadir-locked, with a pointing accuracy of about 1 arcsec rms, and will allow for at least 1 Gbit/day downlink. The sun-synchronous dusk-dawn orbit at 700 km altitude enables having the Sun permanently on the backside of the spacecraft thus minimising Earth stray light. A mission duration of 3.5 years in orbit is foreseen to enable the execution of the science programme. During this period, 20% of the observing time is available to the wider community through yearly ESA call for proposals, as well as through discretionary time approved by ESA’s Director of Science. At the time of this writing, CHEOPS commissioning has been completed and CHEOPS has been shown to fulfill all its requirements. The mission has now started the execution of its science programme.
PubDate: 2020-11-05
DOI: 10.1007/s10686-020-09679-4

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