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Technical Paper

The Submillimeter-Wave Astronomy Satellite: Instrument Thermal Design and Verification

A large telescope aperture, stringent thermal stability and temperature range requirements, and a passively-cooled 150°K module presented major challenges in thermal design and hardware fabrication of this Small Explorer science instrument. This paper details SWAS thermal system design, problems that were revealed in thermal testing, and the hardware changes that brought the design into an acceptable condition. Thermal test techniques that helped verify design adequacy are described, as well as the analytical methods used to correlate the thermal model and predict flight performance.
Technical Paper

Thermal Control Study of the Constellation-X Telescope Aperture

Focusing mirrors for X-ray astronomy are almost always located near the open aperture of the X-ray telescope. Such a mirror is typically a concentric nest of near-cylindrical paraboloids. Controlling the mirror temperature and reducing thermal radiation to space is essential to reducing optical distortion of the mirror assembly. This has been successfully done in the past by a partially open structure, termed a precollimator, between the mirror and space; or in the case of metal mirrors, by conduction from the support structure. As designs for future missions strive for more collecting area to “see” fainter objects, the individual mirrors become more numerous and thinner, presenting new challenges to thermal control. We report here studies by the Smithsonian Astrophysical Observatory on thermal control of a 1.6m-diameter X-ray mirror assembly for the Constellation-X mission. The mirrors are 0.3 mm thick, and the nest contains of order 100-200 mirrors.
Technical Paper

Thermal Effects on Imaging Performance of the AXAF Telescope

In the paper the we discuss how the thermal behavior of the Advanced X-ray Astrophysics Facility (AXAF) optical system has been modeled and tested, and how these efforts have influenced the design of the telescope, especially as it relates the imaging performance. This includes the passive/active system covering the space-facing aperture known as the thermal “precollimator”, the mechanical support system that allows the large optical elements to survive the rigors of test in one-G and launch yet minimally affecting on-orbit optical performance, and the active thermal control design of the telescope. Methodologies for the frequently difficult task of transferring results from thermal analysis software to mechanical finite-element analyzers to model thermal deformations are discussed. The complexity of these distortions of the surfaces of the mirror elements required the use of optical raytrace models to assess imaging performance of the telescope.
Technical Paper

Precollimators: Passive On-Orbit Thermal Control for Space-Based Telescope Apertures

The large optical apertures required by many space-based telescopes make thermal control of these optics a significant challenge. One technique which has been used for x-ray telescopes involves placing insulating tubes forward of the entrance aperture. The reduction in both conduction and direct view produces a thermal gradient along the tubes, increasing the effective sink temperature for the optics and reducing the effective radiant source temperature and heat flow to space. In another configuration the “tubes” are formed by aperture slots in a stacked assembly of flat, low-conduction baffle plates. Because these apertures collimate both incident x-rays and thermal radiation, such an assembly has been termed a “thermal precollimator.” This paper describes precollimator design principles and design, analysis and testing of a precollimator for the Advanced X-ray Astrophysics Facility (AXAF).
Technical Paper

Experiences with the ODX Diagnostic Database Standard

ODX (Open Diagnostics data eXchange) is a standard diagnostic data format specified by the European ASAM group, to simplify the exchange of vehicle diagnostic data between manufacturers, suppliers and service dealerships. The ODX database contains diagnostic data for the whole vehicle together with details of all vehicle ECUs. This paper gives an overview of the main categories of data contained in the ODX diagnostic database. A Windows-based diagnostic application was developed to execute ISO 15765 diagnostic services on ECUs, using an ODX database to define the allowed services and parameters for each ECU. The paper describes the structure of the diagnostic application and the steps that were necessary to process the ODX and tailor it to a production ECU.