The ASTRO-H mission was designed and developed through an international collaboration of JAXA, NASA, ESA, and the CSA. It was successfully launched on February 17, 2016, and then named Hitomi. During the in-orbit verification phase, the on-board observational instruments functioned as expected. The intricate coolant and refrigeration systems for soft X-ray spectrometer (SXS, a quantum micro-calorimeter) and soft X-ray imager (SXI, an X-ray CCD) also functioned as expected. However, on March 26, 2016, operations were prematurely terminated by a series of abnormal events and mishaps triggered by the attitude control system. These errors led to a fatal event: the loss of the solar panels on the Hitomi mission. The X-ray Astronomy Recovery Mission (or, XARM) is proposed to regain the key scientific advances anticipated by the international collaboration behind Hitomi. XARM will recover this science in the shortest time possible by focusing on one of the main science goals of Hitomi,“Resolving astrophysical problems by precise high-resolution X-ray spectroscopy”.<sup>1</sup> This decision was reached after evaluating the performance of the instruments aboard Hitomi and the mission’s initial scientific results, and considering the landscape of planned international X-ray astrophysics missions in 2020’s and 2030’s. Hitomi opened the door to high-resolution spectroscopy in the X-ray universe. It revealed a number of discrepancies between new observational results and prior theoretical predictions. Yet, the resolution pioneered by Hitomi is also the key to answering these and other fundamental questions. The high spectral resolution realized by XARM will not offer mere refinements; rather, it will enable qualitative leaps in astrophysics and plasma physics. XARM has therefore been given a broad scientific charge: “Revealing material circulation and energy transfer in cosmic plasmas and elucidating evolution of cosmic structures and objects”. To fulfill this charge, four categories of science objectives that were defined for Hitomi will also be pursued by XARM; these include (1) Structure formation of the Universe and evolution of clusters of galaxies; (2) Circulation history of baryonic matters in the Universe; (3) Transport and circulation of energy in the Universe; (4) New science with unprecedented high resolution X-ray spectroscopy. In order to achieve these scientific objectives, XARM will carry a 6 × 6 pixelized X-ray micro-calorimeter on the focal plane of an X-ray mirror assembly, and an aligned X-ray CCD camera covering the same energy band and a wider field of view. This paper introduces the science objectives, mission concept, and observing plan of XARM.
The JWST Optical Telescope Element (OTE) assembly is the largest optically stable infrared-optimized telescope currently being manufactured and assembled, and is scheduled for launch in 2018. The JWST OTE, including the 18 segment primary mirror, secondary mirror, and the Aft Optics Subsystem (AOS) are designed to be passively cooled and operate near 45K. These optical elements are supported by a complex composite backplane structure. As a part of the structural distortion model validation efforts, a series of tests are planned during the cryogenic vacuum test of the fully integrated flight hardware at NASA JSC Chamber A. The successful ends to the thermal-distortion phases are heavily dependent on the accurate temperature knowledge of the OTE structural members. However, the current temperature sensor allocations during the cryo-vac test may not have sufficient fidelity to provide accurate knowledge of the temperature distributions within the composite structure. A method based on an inverse distance relationship among the sensors and thermal model nodes was developed to improve the thermal data provided for the nanometer scale WaveFront Error (WFE) predictions. The Linear Distance Weighted Interpolation (LDWI) method was developed to augment the thermal model predictions based on the sparse sensor information. This paper will encompass the development of the LDWI method using the test data from the earlier ‘pathfinder’ cryo-vac tests, and the results of the notional and as tested WFE predictions from the structural finite element model cases to characterize the accuracies of this LDWI method.
The Soft X-Ray Telescope (SXT) modules are the fundamental focusing assemblies on NASA's next major X-ray
telescope mission, the International X-Ray Observatory (IXO). The preliminary design and analysis of these assemblies
has been completed, addressing the major engineering challenges and leading to an understanding of the factors effecting
module performance. Each of the 60 modules in the Flight Mirror Assembly (FMA) supports 200-300 densely packed
0.4 mm thick glass mirror segments in order to meet the unprecedented effective area required to achieve the scientific
objectives of the mission. Detailed Finite Element Analysis (FEA), materials testing, and environmental testing have
been completed to ensure the modules can be successfully launched. Resulting stress margins are positive based on
detailed FEA, a large factor of safety, and a design strength determined by robust characterization of the glass properties.
FEA correlates well with the results of the successful modal, vibration, and acoustic environmental tests. Deformation of
the module due to on-orbit thermal conditions is also a major design driver. A preliminary thermal control system has
been designed and the sensitivity of module optical performance to various thermal loads has been determined using
optomechanical analysis methods developed for this unique assembly. This design and analysis furthers the goal of
building a module that demonstrates the ability to meet IXO requirements, which is the current focus of the IXO FMA
technology development team.
The International X-ray Observatory mission is a collaborative effort of NASA, ESA, and
JAXA. It will have unprecedented capabilities in spectroscopy, imaging, timing and
polarization measurement. A key enabling element of the mission is a flight mirror
assembly providing unprecedented large effective area (3 m<sup>2</sup>) and high angular resolution
of (5 arcseconds half-power diameter). In this paper we outline the conceptual design of
the mirror assembly and development of technology to enable its construction.
The Flight Mirror Assembly (FMA) preliminary mechanical design for NASA's next major X-ray telescope mission, the
International X-Ray Observatory (IXO), has been developed at NASA Goddard Space Flight Center (GSFC). The design
addresses some unique engineering challenges presented by the unprecedented combination of high angular resolution
and large effective area required to achieve the desired scientific objectives. To meet these requirements, the Wolter-I
Soft X-Ray Telescope (SXT) optical design consists of about 14,000 0.4 mm thick glass mirror segments densely packed
into a 3.4 m diameter FMA and supported with micron level accuracy and stability. Key engineering challenges
addressed include ensuring positive stress margins for the glass segments with a high Factor of Safety, keeping the
structure light enough to launch, providing a large effective area, and preventing unacceptable thermal distortion.
Standard mechanical design techniques such as FEM modeling and optimization, integrated optomechanical analysis,
and development testing were applied to this unique problem. The thin mirror segments are mounted into 60
intermediate wedge shaped structures called modules. Modules are kinematically mounted to the FMA primary structure
which is optimized for minimum mass and obscuration of the clear aperture. The preliminary design demonstrates the
feasibility of building and launching a large space-based SXT using slumped glass mirrors which meets the IXO
effective area, mass, structural, and thermal requirements.
We present a conceptual design for a scalable (10-50 meter segmented filled-aperture) space observatory operating at UV-optical-near infrared wavelengths. This telescope is designed for assembly in space by robots, astronauts or a combination of the two, as envisioned in NASA's Vision for Space Exploration. Our operations concept for this space telescope provides for assembly and check-out in an Earth Moon L2 (EML2) orbit, and transport to a Sun-Earth L2 (SEL2) orbit for science operations and routine servicing, with return to EML2 for major servicing. We have developed and analyzed initial designs for the optical, structural, thermal and attitude control systems for a 30-m aperture space telescope. We further describe how the separate components are packaged for launch by heavy lift vehicle(s) and the approach for the robot assembly of the telescope from these components.