ATHENA is currently in Phase A, with a view to adoption in 2021. This paper will present the design status for the spacecraft (SC), covering the overall configuration of the SC, as well as the main design features of the main modules. Then the focus will be on the functional and environmental requirements, the thermo-mechanical design and the Assembly, Integration and Test considerations related to the very large Mirror Assembly Module housing the Silicon Pore Optic (SPO) Mirror Modules. Initially functional requirements on the optics accommodation are presented, with the Effective Area and Half Energy Width (HEW) requirements leading to a preliminary HEW budget allocated across the main contributors. This is then used as a reference to derive subsequent requirements and engineering considerations, including: The procedures and technologies under consideration for AIT to achieve the required alignment; stiffness requirements and handling scheme required to constrain deformation under gravity during x-ray testing; temperature control to constrain thermo-elastic deformation during flight; and the capability to focus using the Instrument Switching Mechanism. Next, our best understanding of the launch mechanical environment imposed by the forthcoming Ariane-64 launch vehicle is presented along with the mechanical requirements of the MMs, and the need to minimize shock-loading of the MMs is stressed. Methods to achieve this are presented, including: Modal-tuning of the MAM to act as a low-pass filter during launch shock events; low-shock release-mechanisms; the possibility to deploy a passive vibration solution in the launcher interface plane to reduce loads.
Silicon Pore Optics (SPO) provide high angular resolution with low effective area density as required for the Advanced Telescope for High Energy Astrophysics (Athena). The x-ray telescope consists of several hundreds of SPO mirror modules mounted in a telescope structure. During the development of the SPO technology, specific requirements of a future mass production have been considered right from the beginning. We present an updated analysis of the time and resources required for the Athena flight programme. A preliminary timeline for building and commissioning the required infrastructure, and for flight model production and integration of the mirror modules, is presented.
The development of the X-ray optics for ATHENA (Advanced Telescope for High ENergy Astrophysics)[1-4], the selected second large class mission in the ESA Science Programme, is progressing further, in parallel with the payload preparation and the system level studies. The optics technology is based on the Silicon Pore Optics (SPO) [5-48], which utilises the excellent material properties of Silicon and benefits from the extensive investments made in the semiconductor industry. With its pore geometry the SPO is intrinsically very robust and permits the use of very thin mirrors while achieving good angular resolution. In consequence, the specific mass of the resultant ATHENA optics is very low compared to other technologies, and suitable to cope with the imposed environmental requirements. Further technology developments preparing the ATHENA optics are ongoing, addressing additive manufacturing of the telescope structure, the integration and alignment of the mirror assembly, numerical simulators, coating optimisations, metrology, test facilities, studies of proton reflections and meteorite impacts, etc. A detailed Technology Development Plan was elaborated and is regularly being updated, reflecting the progress and the mission evolution. The required series production and integration of the many hundred mirror modules constituting the ATHENA telescope optics is an important consideration and a leading element in the technology development. The developments are guided by ESA, implemented in industry and supported by research institutions. The many ongoing SPO technology development activities aim at demonstrating the readiness of the optics technology at the review deciding the adoption of ATHENA onto the ESA Science flight programme, currently expected for 2021. Technology readiness levels of 5/6 have to be demonstrated for all critical elements, but also the compliance to cost and schedule constraints for the mission.
The large Halo orbit in L2 of the ATHENA mission will expose the spacecraft (SC) to a significant flux of charged particles which is expected to overlap with the energy range of the instruments. This is a source of measurement background that needs to be minimized as much as possible to achieve the strict requirements of the mission. The need to know and mitigate this type of background has been identified as critical, and has led to a number of technology development activities which are progressing in parallel to the Phase A activities. Particularly, this paper details the status of the on-going activities to develop a set of charged particle diverters whose goal is to reduce the background generated by soft-protons which are focused by the Silicon Pore Optics (SPO) mirror modules towards the instrument detectors. This paper explains the considerations leading to an accommodation of the charged particle diverters close to the instruments in the Science Instrument Module (SIM), and details the analytical approach followed to choose the massoptimal location for the case of a uniform magnetic field Halbach design. The case of graded (non-uniform) magnetic fields is also explained in an effort to further decrease the mass. Preliminary magnetic field maps are presented as a proxy to compare the mass from different options. Finally, the first engineering models, manufacturing and test plans are presented which are the focus of a technology development activity aiming at the validation of the technologies involved up to TRL5.
The work on the definition and technological preparation of the ATHENA (Advanced Telescope for High ENergy Astrophysics) mission continues to progress. In parallel to the study of the accommodation of the telescope, many aspects of the X-ray optics are being evolved further. The optics technology chosen for ATHENA is the Silicon Pore Optics (SPO), which hinges on technology spin-in from the semiconductor industry, and uses a modular approach to produce large effective area lightweight telescope optics with a good angular resolution. Both system studies and the technology developments are guided by ESA and implemented in industry, with participation of institutional partners. In this paper an overview of the current status of the telescope optics accommodation and technology development activities is provided.
ATHENA, Europe’s next generation x-ray telescope, is currently under Assessment Phase study with parallel candidate industrial Prime contractors after selection for the 'L2' slot in ESA's Cosmic Vision Programme, with a mandate to address the 'Hot and Energetic Universe' Cosmic Vision science theme. This paper will consider the main technical requirements of the mission, and their mapping to resulting design choices at both mission and spacecraft level. The reference mission architecture and current reference spacecraft design will then be described, with particular emphasis given to description of the Science Instrument Module (SIM) design, currently under the responsibility of the ESA Study Team. The SIM is a very challenging item due primarily to the need to provide to the instruments (i) a soft ride during launch, and (ii) a very large (~3 kW) heat dissipation capability at varying interface temperatures and locations.
ATHENA is currently in Phase A, with a view to adoption upon a successful Mission Adoption Review in 2019/2020. After a brief presentation of the reference spacecraft (SC) design, this paper will focus on the functional and environmental requirements, the thermo-mechanical design and the Assembly, Integration, Verification & Test (AIVT) considerations related to housing the Silicon Pore Optics (SPO) Mirror Modules (MM) in the very large Mirror Assembly Module (MAM).
Initially functional requirements on the MM accommodation are presented, with the Effective Area and Half Energy Width (HEW) requirements leading to a MAM comprising (depending on final mirror size selected) between ~700-1000 MMs, co-aligned with exquisite accuracy to provide a common focus. A preliminary HEW budget allocated across the main error-contributors is presented, and this is then used as a reference to derive subsequent requirements and engineering considerations, including: The procedures and technologies for MM-integration into the Mirror Structure (MS) to achieve the required alignment accuracies in a timely manner; stiffness requirements and handling scheme required to constrain deformation under gravity during x-ray testing; temperature control to constrain thermo-elastic deformation during flight; and the role of the Instrument Switching Mechanism (ISM) in constraining HEW and Effective Area errors.
Next, we present the key environmental requirements of the MMs, and the need to minimise shock-loading of the MMs is stressed. Methods to achieve this Ø are presented, including: Selection of a large clamp-band launch vehicle interface (LV I/F); lengthening of the shock-path from the LV I/F to the MAM I/F; modal-tuning of the MAM to act as a low-pass filter during launch shock events; use of low-shock HDRMs for the MAM; and the possibility to deploy a passive vibration solution at the LV I/F to reduce loads.
ATHENA, Europe’s next generation x-ray telescope, has recently been selected for the 'L2' slot in ESA's Cosmic Vision Programme, with a mandate to address the 'Hot and Energetic Universe' Cosmic Vision science theme. The mission is currently in the Assessment/Definition Phase (A/B1), with a view to formal adoption after a successful System Requirements Review in 2019. This paper will describe the reference mission architecture and spacecraft design produced during Phase 0 by the ESA Concurrent Design Facility (CDF), in response to the technical requirements and programmatic boundary conditions. The main technical requirements and their mapping to resulting design choices will be presented, at both mission and spacecraft level. An overview of the spacecraft design down to subsystem level will then be presented (including the telescope and instruments), remarking on the critically-enabling technologies where appropriate. Finally, a programmatic overview will be given of the on-going Assessment Phase, and a snapshot of the prospects for securing the ‘as-proposed’ mission within the cost envelope will be given.
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.
LOFT (Large Observatory For x-ray Timing) is one of four candidates for the M3 slot (launch in 2024, with the option of a launch in 2022) of ESAs Cosmic Vision 2015 – 2025 Plan, and as such it is currently undergoing an initial assessment phase lasting one year. The objective of the assessment phase is to provide the information required to enable the down selection process, in particular: the space segment definition for meeting the assigned science objectives; consideration of and initial definition of the implementation schedule; an estimate of the mission Cost at Completion (CaC); an evaluation of the technology readiness evaluation and risk assessment. The assessment phase is divided into two interleaved components: (i) A payload assessment study, performed by teams funded by member states, which is primarily intended for design, definition and programmatic/cost evaluation of the payload, and (ii) A system industrial study, which has essentially the same objectives for the space segment of the mission. This paper provides an overview of the status of the LOFT assessment phase, both for payload and platform. The initial focus is on the payload design status, providing the reader with an understanding of the main features of the design. Then the space segment assessment study status is presented, with an overview of the principal challenges presented by the LOFT payload and mission requirements, and a presentation of the expected solutions. Overall the mission is expected to enable cutting-edge science, is technically feasible, and should remain within the required CaC for an M3 candidate.