Ultra Violet Imaging Telescope (UVIT) is one of the 5 instruments on AstroSat satellite, which was launched on September 28, 2015. UVIT was designed to make images with a resolution of \(< 1.8''\), simultaneously in two ultraviolet channels: Far Ultraviolet (130–180 nm) and Near Ultraviolet (200–300 nm). Images are also made in visible region (320–550 nm) for tracking drifts in pointing. The shortest wavelengths to be observed with UVIT can be heavily absorbed by mono-molecular deposits/contamination on the optical surfaces. Keeping contamination under control in UVIT was a major challenge and it required a variety of actions: (i) strict control of the payload materials and process, (ii) mechanical configuration, (iii) baking of all the parts to release all the adsorbed molecules etc., (iv) assembly in ultra cleanrooms, (v) pre-inspection and auditing of all the areas, in which UVIT was placed, for any potential for contamination, (vi) continuous purging, with ultra-pure nitrogen gas, till a few days before the launch, etc. In order to minimise any possible cross contaminations from the other payloads/satellite, the doors of UVIT were opened 2 months after the launch. The high performance in the orbit and high stability of the sensitivity over 4 years in the orbit shows that the contamination was negligible. This paper presents the processes and protocols followed during the integration and testing phase to minimise the contamination in order to prevent any performance degradation.

紫外成像望远镜 (UVIT) 是 AstroSat 卫星的 5 种仪器之一，于 2015 年 9 月 28 日发射。UVIT 旨在制作分辨率为\(< 1.8''\), 同时在两个紫外线通道中：远紫外线 (130–180 nm) 和近紫外线 (200–300 nm)。图像也在可见区域 (320–550 nm) 中制作，用于跟踪指向中的漂移。使用 UVIT 观察到的最短波长会被光学表面上的单分子沉积物/污染物严重吸收。在 UVIT 中控制污染是一项重大挑战，需要采取多种措施：(i) 严格控制有效载荷材料和工艺，(ii) 机械配置，(iii) 烘烤所有部件以释放所有吸附分子等，(iv) 在超洁净室中组装，(v) 对放置 UVIT 的所有区域进行预检查和审核，以了解任何潜在的污染，(vi) 使用超纯氮气持续吹扫，直到发布前几天，等等。为了尽量减少来自其他有效载荷/卫星的任何可能的交叉污染，发射后 2 个月打开了 UVIT 的大门。轨道上的高性能和4年在轨灵敏度的高稳定性表明污染可以忽略不计。本文介绍了在集成和测试阶段遵循的流程和协议，以最大限度地减少污染，以防止任何性能下降。