China is planning to construct a new space-borne gravitational-wave (GW) observatory, the TianQin project, in which the spaceborne telescope is an important component in laser interferometry. The telescope is aimed to transmit laser beams between the spacecrafts for the measurement of the displacements between proof-masses in long arms. The telescope should have ultra-small wavefront deviation to minimize noise caused by pointing error, ultra-stable structure to minimize optical path noise caused by temperature jitter, ultra-high stray light suppression ability to eliminate background noise. In this paper, we realize a telescope system design with ultra-stable structure as well as ultra-low wavefront distortion for the space-based GW detection mission. The design requirements demand extreme control of high image quality and extraordinary stray light suppression ability. Based on the primary aberration theory, the initial structure design of the mentioned four-mirror optical system is explored. After optimization, the maximum RMS wavefront error is less than λ/300 over the full field of view (FOV), which meets the noise budget on the telescope design. The stray light noise caused by the back reflection of the telescope is also analyzed. The noise at the position of optical bench is less than 10-10 of the transmitted power, satisfying the requirements of space gravitational-wave detection. We believe that our design can be a good candidate for TianQin project, and can also be a good guide for the space telescope design in any other similar science project.

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Quick superplastic forming is a new technology, which combines hot drawing preforming and superplastic forming. It makes full use of the high speed of hot drawing and good formability of superplasticity. This article uses this method to have an experiment of the side wall outer panel of metro vehicle. The results show that the production efficiency is high, the cost is low and the method is feasible. For aluminum alloy complex components, it can solve the difficulties of stamping and low speed of superplasticity.Keywords: Aluminum alloy / superplasticity / quick superplasticity / side wall outer panel / metro vehicle Schlüsselwörter: Aluminiumlegierung / Superplastizität / schnelle Superplastizität / Seitenwand-Außenblech / U-Bahn-Wagon