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I.INTRODUCTIONThis paper describes the main thermo-mechanical design features and performances of the Co-Alignment Sensor (CAS) developed by LIDAX and CRISA under ESA program with AIRBUS Defence & Space as industry prime. The CAS can be generally described as a Focal Plane Assembly with integrated Optics, Detector, and Electronics. The Co-Alignment Sensor (CAS) is a part of ATLID Instrument, whose mission responds to the need to provide a picture of the 3-dimensional spatial and temporal structure of the radiative flux field at the top of the Earth atmosphere, within the atmosphere and at the Earth’s surface. The CAS is located on the ATLID Optical Bench and is part of the control loop that allows identifying the pointing direction of the Laser signal return used to control the Laser co-Alignment with Optical Bench. CRISA is the final responsible of the whole CAS project design and development II.MODELS & PROJECT STATUSThe following deliverable models are considered:
Actually, the STM became a Qualification Model from thermo-mechanical point of view. Currently, the STM qualification testing has been successfully completed. III.MAIN REQUIREMENTSFollowing main mechanical requirements are applicable: Mass, Structural & Thermal
Stability & Alignment IV.MECHANICAL DESIGN DESCRIPTIONA.GeneralThe CAS is shown in Fig. 1, and it is divided in three main components:
The whole assembly is supported by means of three bipods to get the appropriate relation between stiffness and loads induced at the interface. B.Mechanical Bench AssemblyMechanical Bench Assembly shown in Fig. 2 is the main thermo-structural component of CAS and it is composed of different thermo-mechanical components such as: Main Bracket The Main Bracket is a Ti6Al4V bracket of complex geometry, which is the main structural element of CAS, and its complex shape provides the following functionalities:
Titanium choice (with respect to invar) is based on its lower mass density, high strength and better machining capabilities in spite of a higher thermal expansion coefficient (worst thermal performance). Bipods Three identical Bipods also made of Ti6Al4V supports the Main Bracket (and all elements mounted on) providing the following functionalities:
Manufacturing Manufacturing has become a complex issue due to the following:
Above points have driven to use Electrostatic Discharge Machining (EDM) manufacturing process for manufacturing the Main Bracket & Bipods Assembly, with the drawback of the exhaustive process controls required to assure the removal of alpha-case and hydrogen in the titanium surfaces. A specific manufacturing process has been defined and successfully implemented for STM Model. Thermal Straps Thermal Straps with specific shapes due to AIV issues have been developed and submitted to qualification; they are based on piled sheets and terminals all made of golden copper. Manufacturing process and correlation between design and measured conductance have been proven during the straps qualification campaign. V.PERFORMANCESComparison between specified and measured performances is shown in the below table.
VI.CONCLUSIONSThe following conclusions can be established:
VII.ACKNOWLEDGEMENTSThe activities described in this paper were made possible with the help and support of the LIDAX staff, and the following colleagues from different companies and institutions. We would like to thank, from INTA: Gonzalo Ramos & Tomás Belenguer and Christophe Delettrez & Philippe Lingot from Airbus Defence & Space for their collaboration and support. |
