THESEUS is a space mission concept currently under Phase A study by ESA as candidate M5 mission, aiming at exploiting Gamma-Ray Bursts for investigating the early Universe and at providing a substantial advancement of multi-messenger and time-domain astrophysics. In addition to the full exploitaiton of high-redshift GRBs for cosmology (pop-III stars, cosmic re-ionization, SFR and metallicity evolution up to the "cosmic dawn"), THESEUS will allow the identification and study of the electromagnetic counterparts to sources of gravitational waves which will be routinely detected in the late '20s / early '30s by next generation facilities like aLIGO/aVirgo, LISA, KAGRA, and Einstein Telescope (ET), as well as of most classes of transient sources, thus providing an ideal sinergy with the large e.m. facilities of the near future like LSST, ELT, TMT, SKA, CTA, ATHENA. We present an overview of the mission science case, concept design (instruments and spacecraft) and expected performances.
The Soft X-ray Imager instrument on the ESA THESEUS mission will provide high-energy imaging and spectroscopy observations of fast transients, providing significant steps forward in our understanding and characterisation of the early Universe. The instrument will utilise high performance microchannel plate optics (MPOs) and some of the first X-ray optimised CMOS devices to be used for space applications. The instrument team are currently developing a flight-like prototype instrument in order to enable full and appropriate characterisation of the instrument, and in particular the performance of candidate detectors. Here we present early results from the focal plane requirement study programme (including performance modelling and trade-off studies).
The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a Chinese – French satellite mission due to be launched in the summer of 2022. It is composed of four instruments: ECLAIRs, for detecting X-ray and gamma-ray transients (4-250 keV); GRM, a gamma-ray spectrometer (15 keV-5 MeV); VT, a visible telescope and the Microchannel X-ray Telescope (MXT). The MXT’s main goal is to precisely localize, and spectrally characterize X-ray afterglows of Gamma-Ray Bursts. The MXT is a narrow-field-optimised lobster eye X-ray focusing telescope comprising an array of 25 square Micro Pore Optics (MPOs), with a detectorlimited field of view of ∼1 square degree, working in the energy band 0.2-10 keV. The SVOM qualification model (QM) MXT optic (MOP) was designed and built at the University of Leicester, and is the first complete, lobster eye optic to be X-ray tested. We present results from the PANTER facility (MPE), where a full calibration of the QM MOP was carried out. The response of the optic was studied at seven energies from C-K to Cu-K, and the effective area at multiple off-axis angles at each energy was measured. The focal length of the MOP was confirmed and the PSF was studied on and off-axis. In addition, we present details of the modelling and analysis, which was used to calculate the results from the test campaign. The effective area and PSF are in good agreement with the modelling, indicating that the optic is performing as expected.
The Gravitational-wave Optical Transient Observer (GOTO) is a wide-field telescope project focused on detecting optical counterparts to gravitational-wave sources. GOTO uses arrays of 40 cm unit telescopes (UTs) on a shared robotic mount, which scales to provide large fields of view in a cost-effective manner. A complete GOTO mount uses 8 unit telescopes to give an overall field of view of 40 square degrees, and can reach a depth of 20th magnitude in three minutes. The GOTO-4 prototype was inaugurated with 4 unit telescopes in 2017 on La Palma, and was upgraded to a full 8-telescope array in 2020. A second 8-UT mount will be installed on La Palma in early 2021, and another GOTO node with two more mount systems is planned for a southern site in Australia. When complete, each mount will be networked to form a robotic, dual-hemisphere observatory, which will survey the entire visible sky every few nights and enable rapid follow-up detections of transient sources.
The Transient High Energy Sources and Early Universe Surveyor is an ESA M5 candidate mission currently in Phase A, with Launch in ∼2032. The aim of the mission is to complete a Gamma Ray Burst survey and monitor transient X-ray events. The University of Leicester is the PI institute for the Soft X-ray Instrument (SXI), and is responsible for both the optic and detector development. The SXI consists of two wide field, lobster eye X-ray modules. Each module consists of 64 Micro Pore Optics (MPO) in an 8 by 8 array and 8 CMOS detectors in each focal plane. The geometry of the MPOs comprises a square packed array of microscopic pores with a square cross-section, arranged over a spherical surface with a radius of curvature twice the focal length of the optic. Working in the photon energy range 0.3-5 keV, the optimum L/d ratio (length of pore L and pore width d) is upwards of 50 and is constant across the whole optic aperture for the SXI. The performance goal for the SXI modules is an angular resolution of 4.5 arcmin, localisation accuracy of ∼1 arcmin and employing an L/d of 60. During the Phase A study, we are investigating methods to improve the current performance and consistency of the MPOs, in cooperation with the manufacturer Photonis France SAS. We present the optics design of the THESEUS SXI modules and the programme of work designed to improve the MPOs performance and the results from the study.
Einstein Probe is a Chinese Academy of Science (CAS) mission due for launch at the end of 2022 with its primary goals to discover high-energy transients and monitor variable objects. The mission consists of two instruments, the Wide field X-ray Telescope (WXT), a lobster eye X-ray telescope consisting of twelve identical modules; and the Follow-up X-ray Telescope (FXT), which is a traditional Wolter X-ray telescope, which is jointly developed by CAS, the European Space Agency (ESA) and the Max Planck Institute for Extraterrestrial Physics (MPE). Each of the WXT modules comprise of 36 micro pore optics (MPOs), with a 375 mm focal length, a field of view of more than 3600 square degrees, a goal of 5 arcmin resolution and working in the energy range of 0.5-4 keV. As part of the collaboration between CAS and ESA, the University of Leicester (UoL) is acting as a testing facility and repeatability check for several elements of the WXT optic development. This includes calibration of individual MPOs, temperature measurements on a prototype module, calibration of a qualification module and full calibration of one of the flight module optics. The majority of these tests will be performed in the two X-ray facilities at the University of Leicester, the Tunnel Test Facility (TTF) and the Vertical Test Facility (VTF). Presented here are details of the tests carried out and the results obtained from the first batch of individual MPOs and the plan for the thermal tests of the prototype in the TTF.
We are entering a new era for high energy astrophysics with the use of new technology to increase our ability to both survey and monitor the sky. The Soft X-ray Imager (SXI) instrument on the THESEUS mission will revolutionize transient astronomy by using wide-field focusing optics to increase the sensitivity to fast transients by several orders of magnitude. The THESEUS mission is under Phase A study by ESA for its M5 opportunity. THESEUS will carry two large area monitors utilizing Lobster-eye (the SXI instrument) and coded-mask (the XGIS instrument) technologies, and an opticalIR telescope to provide source redshifts using multi-band imaging and spectroscopy. The SXI will operate in the soft (0.3- 5 keV) X-ray band, and consists of two identical modules, each comprising 64 Micro Pore Optics and 8 large-format CMOS detectors. It will image a total field of view of 0.5 steradian instantaneously while providing arcminute localization accuracy. During the mission, the SXI will find many hundreds of transients per year, facilitating an exploration of the earliest phase of star formation and comes at a time when multi-messenger astronomy has begun to provide a new window on the universe. THESEUS will also provide key targets for other observing facilities, such as Athena and 30m class ground-based telescopes.
We present a ray tracing simulation of the Soft X-ray Imager (SXI) optics for the THESEUS observatory using the open-source McXtrace software package. THESEUS is a candidate mission within the Cosmic Vision programme of the European Space Agency and is designed to monitor high-energy transient events in the entire sky, therefore relying on fast slewing of the spacecraft. This capability will however impose large temperature variations and gradients across the optics which can cause thermoelastic deformation of the Soft X-ray Imager microchannel optics. The purpose of this study is to evaluate the impact on the point spread function (PSF) due to in-orbit temperature variation. Based on thermal analysis of the Soft X-ray Imager, perturbations to the ideal microchannel geometry are derived and provided as input to the ray tracer.
The SVOM (Space-based multi-band astronomical Variable Objects Monitor) French-Chinese mission is dedicated to the detection, localization and study of Gamma Ray Bursts (GRBs) and other high-energy transient phenomena. We first present the general description of the French payload composed of the ECLAIRs instrument, dedicated to GRB detection and localization and the MXT instrument, dedicated to GRB follow-up observation in soft X-ray band. Then the paper describes more in detail the design and the performances of the MXT instrument, finally a status of MXT development will be given.
The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a French-Chinese space mission to be launched in 2021 with the goal of studying gamma-ray bursts, the most powerful stellar explosions in the Universe. The Microchannel X-ray Telescope (MXT) on-board SVOM, is an X-ray focusing telescope with a detector-limited field of view of ∼1 square° , working in the 0.2-10 keV energy band. The MXT is a narrow-field-optimised lobster eye telescope, designed to promptly detect and accurately locate gamma-ray bursts afterglows. The breadboard MXT optic comprises of an array of square pore micro pore optics (MPOs) which are slumped to a spherical radius of 2 m giving a focal length of 1 m and an intrinsic field of view of ∼6° . We present details of the baseline design and results from the ongoing X-ray tests of the breadboard and structural thermal model MPOs performed at the University of Leicester and at Panter. In addition, we present details of modelling and analysis which reveals the factors that limit the angular resolution, characteristics of the point spread function and the efficiency and collecting area of the currently available MPOs.
Today the scientific community is facing an increasing complexity of the scientific projects, from both a technological and a management point of view. The reason for this is in the advance of science itself, where new experiments with unprecedented levels of accuracy, precision and coverage (time and spatial) are realised. Astronomy is one of the fields of the physical sciences where a strong interaction between the scientists, the instrument and software developers is necessary to achieve the goals of any Big Science Project. The Cherenkov Telescope Array (CTA) will be the largest ground-based very high-energy gamma-ray observatory of the next decades. To achieve the full potential of the CTA Observatory, the system must be put into place to enable users to operate the telescopes productively. The software will cover all stages of the CTA system, from the preparation of the observing proposals to the final data reduction, and must also fit into the overall system. Scientists, engineers, operators and others will use the system to operate the Observatory, hence they should be involved in the design process from the beginning. We have organised a workgroup and a workflow for the definition of the CTA Top Level Use Cases in the context of the Requirement Management activities of the CTA Observatory. Scientists, instrument and software developers are collaborating and sharing information to provide a common and general understanding of the Observatory from a functional point of view. Scientists that will use the CTA Observatory will provide mainly Science Driven Use Cases, whereas software engineers will subsequently provide more detailed Use Cases, comments and feedbacks. The main purposes are to define observing modes and strategies, and to provide a framework for the flow down of the Use Cases and requirements to check missing requirements and the already developed Use-Case models at CTA sub-system level. Use Cases will also provide the basis for the definition of the Acceptance Test Plan for the validation of the overall CTA system. In this contribution we present the organisation and the workflow of the Top Level Use Cases workgroup.
The Large Observatory For x-ray Timing (LOFT) is a mission concept which was proposed to ESA as M3 and M4 candidate in the framework of the Cosmic Vision 2015-2025 program. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument and the uniquely large field of view of its wide field monitor, LOFT will be able to study the behaviour of matter in extreme conditions such as the strong gravitational field in the innermost regions close to black holes and neutron stars and the supra-nuclear densities in the interiors of neutron stars. The science payload is based on a Large Area Detector (LAD, >8m2 effective area, 2-30 keV, 240 eV spectral resolution, 1 degree collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e.g., GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the current technical and programmatic status of the mission.
We present simulations of the detection probability for absorption lines from ions in the warm and hot ionized medium (WHIM) with Athena in the spectra of Gamma-ray burst afterglows. The simulations are based on Swift XRT lightcurves of these afterglows and are performed using the end-to-end simulation framework SIXTE. We simulate both the case of single and multiple absorption lines, as well as results for line searches in absorption structures from a more complex medium. We show that the Athena X-IFU can detect WHIM lines with strong Ovii lines (equivalent widths larger than 0.14 eV) in spectra containing 3 x 106 counts.
The Transient High Energy Sky and Early Universe Surveyor (THESEUS) is a mission concept under development by a large international collaboration aimed at exploiting gamma-ray bursts for investigating the early Universe. The main scientific objectives of THESEUS include: investigating the star formation rate and metallicity evolution of the ISM and IGM up to redshift ~9–10, detecting the first generation (pop III) of stars, studying the sources and physics of re-ionization, detecting the faint end of galaxies luminosity function. These goals will be achieved through a unique combination of instruments allowing GRB detection and arcmin localization over a broad FOV (more than 1sr) and an energy band extending from several MeVs down to 0.3 keV with unprecedented sensitivity, as well as on-board prompt (few minutes) follow-up with a 0.6m class IR telescope with both imaging and spectroscopic capabilities. Such instrumentation will also allow THESEUS to unveil and study the population of soft and sub-energetic GRBs, and, more in general, to perform monitoring and survey of the X-ray sky with unprecedented sensitivity.
We identify all the significant aberrations that limit the performance of square pore micro-channel plate optics (MPOs) used as an X-ray lobster eye. These include aberrations intrinsic to the geometry, intrinsic errors associated with the slumping process used to introduce a spherical form to the plates and imperfections associated with the plate manufacturing process. The aberrations are incorporated into a comprehensive software model of the X-ray response of the optics and the predicted imaging response is compared with the measured X-ray performance obtained from a breadboard lobster eye. The results reveal the manufacturing tolerances which limit the current performance of MPOs and enable us to identify particular intrinsic aberrations which will limit the ultimate performance we can expect from MPO-lobster eye telescopes.
The Large Observatory For x-ray Timing (LOFT) was studied within ESA M3 Cosmic Vision framework and participated in the final downselection for a launch slot in 2022-2024. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument, LOFT will study the behaviour of matter under extreme conditions, such as the strong gravitational field in the innermost regions of accretion flows close to black holes and neutron stars, and the supranuclear densities in the interior of neutron stars. The science payload is based on a Large Area Detector (LAD, 10 m2 effective area, 2-30 keV, 240 eV spectral resolution, 1° collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e.g. GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the status of the mission at the end of its Phase A study.
We present the Microchannel X-ray Telescope, a new light and compact focussing telescope that will be ying on the Sino-French SVOM mission dedicated to Gamma-Ray Burst science. The MXT design is based on the coupling of square pore micro-channel plates with a low noise pnCCD. MXT will provide an effective area of about 50 cm2, and its point spread function is expected to be better than 3.7 arc min (FWHM) on axis. The estimated sensitivity is adequate to detect all the afterglows of the SVOM GRBs, and to localize them to better then 60 arc sec after five minutes of observation.
The LOFT mission concept is one of four candidates selected by ESA for the M3 launch opportunity as Medium Size missions of the Cosmic Vision programme. The launch window is currently planned for between 2022 and 2024. LOFT is designed to exploit the diagnostics of rapid X-ray flux and spectral variability that directly probe the motion of matter down to distances very close to black holes and neutron stars, as well as the physical state of ultradense matter. These primary science goals will be addressed by a payload composed of a Large Area Detector (LAD) and a Wide Field Monitor (WFM). The LAD is a collimated (<1 degree field of view) experiment operating in the energy range 2-50 keV, with a 10 m2 peak effective area and an energy resolution of 260 eV at 6 keV. The WFM will operate in the same energy range as the LAD, enabling simultaneous monitoring of a few-steradian wide field of view, with an angular resolution of <5 arcmin. The LAD and WFM experiments will allow us to investigate variability from submillisecond QPO’s to yearlong transient outbursts. In this paper we report the current status of the project.
How structures of various scales formed and evolved from the early Universe up to present time is a fundamental
question of astrophysics. EDGE will trace the cosmic history of the baryons from the early generations of massive
stars by Gamma-Ray Burst (GRB) explosions, through the period of galaxy cluster formation, down to the very low
redshift Universe, when between a third and one half of the baryons are expected to reside in cosmic filaments undergoing
gravitational collapse by dark matter (the so-called warm hot intragalactic medium). In addition EDGE, with its
unprecedented capabilities, will provide key results in many important fields. These scientific goals are feasible with a
medium class mission using existing technology combined with innovative instrumental and observational capabilities
by: (a) observing with fast reaction Gamma-Ray Bursts with a high spectral resolution (R ~ 500). This enables the study
of their (star-forming) environment and the use of GRBs as back lights of large scale cosmological structures; (b)
observing and surveying extended sources (galaxy clusters, WHIM) with high sensitivity using two wide field of view
X-ray telescopes (one with a high angular resolution and the other with a high spectral resolution). The mission concept
includes four main instruments: a Wide-field Spectrometer with excellent energy resolution (3 eV at 0.6 keV), a Wide-
Field Imager with high angular resolution (HPD 15") constant over the full 1.4 degree field of view, and a Wide Field
Monitor with a FOV of 1/4 of the sky, which will trigger the fast repointing to the GRB. Extension of its energy response
up to 1 MeV will be achieved with a GRB detector with no imaging capability. This mission is proposed to ESA as part
of the Cosmic Vision call. We will briefly review the science drivers and describe in more detail the payload of this
We describe the design of Lobster-ISS, an X-ray imaging all-sky monitor (ASM) to be flown as an attached payload on the International Space Station. Lobster-ISS is the subject of an ESA Phase-A study which will begin in December 2001. With an instantaneous field of view 162 x 22.5 degrees, Lobster-ISS will map almost the complete sky every 90 minute ISS orbit, generating a confusion-limited catalogue of ~250,000 sources every 2 months. Lobster-ISS will use focusing microchannel plate optics and imaging gas proportional micro-well detectors; work is currently underway to improve the MCP optics and to develop proportional counter windows with enhanced transmission and negligible rates of gas leakage, thus improving instrument throughput and reducing mass. Lobster-ISS provides an order of magnitude improvement in the sensitivity of X-ray ASMs, and will, for the first time, provide continuous monitoring of the sky in the soft X-ray region (0.1-3.5 keV). Lobster-ISS provides long term monitoring of all classes of variable X-ray source, and an essential alert facility, with rapid detection of transient X-ray sources such as Gamma-Ray Burst afterglows being relayed to contemporary pointed X-ray observatories. The mission, with a nominal lifetime of 3 years, is scheduled for launch on the Shuttle c.2009.