Lightweight and dimensionally ultra stable materials and structures are becoming more and more important for spaced based applications. For scientific and earth observation missions, instruments with ultra high precision requiring ultra-stable structural materials are necessary to achieve the mission goals. Ultra stable glass ceramics exhibit a very good behavior in terms of dimensional stability, but its huge mass is a disadvantage. Composite materials like CFRP (Carbon Fiber Reinforced Plastic) are lightweight and their CTEs (coefficient of thermal expansion) are tunable to be low at a specific temperature. On the other hand these composite materials are changing their geometry during time and environmental situations caused by outgassing. Structures combining the stiffness and lightweight properties of CFRP and the dimensional stability of Zerodur are a key technology for future space missions. Building such structures and measuring their stability are both challenging tasks. Our focus is to measure the dimensional stability of lightweight and dimensionally stable structures for LISA/NGO and GRACE-FO. We characterized an optical breadboard consisting of two 5 mm thick Zerodur plates connected via a CFRP honeycomb structure leading to a weight reduction of 70%. For GRACE-FO the thermal stability of the triple mirror assembly (TMA) of the laser ranging instrument consisting of a 0.5 m CFRP spacer and Zerodur endfittings on each side was characterized. For these measurements a new facility was built. To measure the CTE of the structures a heterodyne interferometer is used to detect the expansion of the device under test. Two beams are reflected at two mirrors attached representatively to the structure on each side. The noise level of our interferometer was demonstrated to be below 2pm/sqrt(Hz) ensuring an ultra-high sensitivity of our measurements. The temperature is measured using PT100 sensors. Temperature changes are applied radiatively by a heating system in vacuum. In this paper, we present our new measurement facility and first measurements of the dimensional stability of the GRACE-FO TMA.
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机译：轻型和尺寸超稳定的材料和结构对于基于间隔的应用正变得越来越重要。对于科学和地球观测任务，需要具有超稳定结构材料的超高精度仪器才能实现任务目标。就尺寸稳定性而言，超稳定的玻璃陶瓷表现出非常好的性能，但是其巨大的质量是不利的。诸如CFRP（碳纤维增强塑料）之类的复合材料重量轻，其CTE（热膨胀系数）在特定温度下可调节至较低的水平。另一方面，这些复合材料在排气引起的时间和环境状况下正在改变其几何形状。结合CFRP的刚度和轻质特性以及Zerodur的尺寸稳定性的结构是未来太空任务的关键技术。建造这样的结构并测量其稳定性都是具有挑战性的任务。我们的重点是为LISA / NGO和GRACE-FO测量重量轻且尺寸稳定的结构的尺寸稳定性。我们表征了一种光学面包板，该面包板由两个5毫米厚的Zerodur板组成，这些板通过CFRP蜂窝结构连接，从而使重量减轻了70％。对于GRACE-FO，表征了激光测距仪的三反射镜组件（TMA）的热稳定性，该组件由0.5 m CFRP垫片和每一侧的Zerodur末端配件组成。为了进行这些测量，建立了新的设施。为了测量结构的CTE，使用外差干涉仪检测被测设备的膨胀。两束光在代表每侧结构的两个反射镜上反射。干涉仪的噪声水平证明低于2 pm/sqrt（Hz），确保了我们测量的超高灵敏度。使用PT100传感器测量温度。温度变化是通过真空中的加热系统以辐射方式施加的。在本文中，我们介绍了我们的新测量设备以及GRACE-FO TMA尺寸稳定性的首次测量。
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