The Narrow Field Infrared Adaptive Optics System (NFIRAOS) within the Thirty Meter Telescope (TMT) will unlock new potential for ground-based astronomy. This subsystem is a series of optics that correct for atmospheric turbulence seen in the Infrared wavelength. One of the critical challenges in the NFIRAOS system is the ability to operate at -30 degrees Celsius. The use of RTV (Room Temperature Vulcanizing) silicone as an adhesive allows a more flexible bond between the optic and its mount. This material is capable of withstanding temperature changes without losing bond strength. Additionally, the large Off Axis Parabola (OAP) mirrors provide a unique technical challenge in their mounting configurations. The optics have with a mass of 90 kilograms and must be mounted able to withstand a 50-degree temperature differential from their ambient temperature bonding. This paper builds of initial conceptual and prototyping work done by ABB and provides the next steps scaling towards a final design of large RTV bondspot optical mounting. Through a combination of simulations, iterative prototyping, room temperature and operational temperature stress testing, a final design proposal is presented backed by statistical and in-house life cycle testing methods. The findings in this work have applications as the industry moves towards mounting larger optics in increasingly challenging environments.
The high spectral resolution mode of the SpicA FAR-infrared Instrument (SAFARI) is enabled by inserting a Fourier Transform Spectrometer (FTS), based on a Martin-Puplett interferometer, into the signal path of the instrument. The cryogenic mechanism (FTSM) enables linear scans of two back-to-back rooftop mirrors sharing a common apex. ABB Inc. is under contract with the Canadian Space Agency to develop and test at 4 K an FTSM Engineering Demonstration Unit (EDU) for TRL-5 demonstration. The main SAFARI FTSM performance drivers are the stringent mechatronic demands (position stability of roof-top mirrors <10 nm RMS, <34 mm linear stroke), severely constrained by a tight thermal budget (heat dissipation <1.5 mW) under a specific micro-vibrations environment (30 μg/√Hz external), all at cryogenic temperatures (4 K). In this paper, we describe a novel cryogenic FTSM design using a reactionless and longstroke flexure-based 4-bar linkage with stiffness compensation. This 1-DOF mechanism passively controls the guiding of the roof-top mirrors with flex pivots while the axial scanning is actuated and controlled with a custom moving magnet actuator (MMA). Static and dynamic balancing of the FTSM ensures that low vibration levels are transferred to/from the FTSM baseplate, and compensation of the mechanism stiffness reduces the force and drive current required from the MMA by a factor <10. Both features lead to MMA power consumption/dissipation <1.5 mW. Results from an engineering analysis of a dynamic model developed for the FTSM EDU are discussed to assess the compliance of this design to the challenging cryogenic SAFARI FTSM performance requirements.
High Energy Astrophysics (HEA) encompasses a broad range of astrophysical science, with sources that include stars and stellar clusters, compact objects (black holes, neutron stars, and white dwarfs), supernova remnants, the interstellar medium, galaxies and clusters of galaxies, Active Galactic Nuclei (AGN), and gamma ray bursters, as well as a variety of fundamental physical processes. The physics involved includes extremes of gravity, density and magnetic field and is often inaccessible via any other waveband. HEA investigates and answers crucial questions in all fields of contemporary astrophysics.
Unlike the focusing of radio and optical light, X-rays are brought to focus through shallow, grazing incident angles. The analogy of skimming a stone across a pond is appropriate in describing how X-rays are focused. The higher the energy of the X-ray photon the shallower the incident angle must be, thereby introducing the requirement of longer focal lengths for focusing high-energy X-rays (E > 10 keV). This technical challenge has hindered scientific advancement in the high-energy regime, while at lower X-ray energies the community has prospered immensely with spectacular data from focusing observatories like XMM-Newton, Chandra, and Suzaku. Now, with ASTRO-H, the community will reap similar rewards from the tremendous improvement in spatial and spectral resolution at high energies. ASTRO-H is a JAXA mission. More information can be found on the ASTRO-H web site [1].
Because of the grazing-angle optics, high-energy X-ray instruments have a long focal length. The Hard X-ray Imager (HXI) of ASTRO-H has its detector housed in a boom that will extend by about 6 m in orbit so that a focal length of 12 m can be achieved for that instrument. This long structure will inevitably oscillate and flex, especially when passing across the orbital day/night boundary. In order to retain the essential imaging resolution, it is important that the boom has a metrology system that measures this flexion in order to allow post-acquisition compensation in generating the science images. In the current paper, we describe a possible Alignment Monitoring System (AMS) to measure in real time the relative position of the boom. The AMS will be an important element to guaranty that the ASTRO-H observatory will meet its performance requirements.
The Canadian Space Agency has the intention of providing the AMS to the ASTRO-H mission. The current paper reports a study that was conducted to support that intention.
A development program was conducted to further improve the technology readiness level of the Generic Flight
Interferometer (GFI), a candidate technology for the future hyperspectral sounder on MTG. Interferometer-based
sounders have already demonstrated their performance and reliability in conducting advanced sounding tasks in recent
missions (METOP-A, IBUKI, SCISAT). The transition from previous single-pixel (or few) to large-format array
detectors offering strong hyperspectral capabilities adds technical challenges to the interferometer design. Some of the
improvements required to address those challenges have already been implemented in recent deployment of
hyperspectral commercial products but must be adapted to the space environment and constraints. Other improvements
are dictated by mission specifics but still tend to be recurrent in recent opportunities. The GFI design intent is to regroup
these innovations in a generic modular interferometer platform in order to address a variety of missions with minor
modifications and hence lower development costs and risks.
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