Ultra-precision processing and detection technology for space lightweight mirror

With the development of space optical remote sensing technology, in order to meet the observation requirements of large field of view, wide coverage, and high resolution, the aperture of the mirror is getting larger and larger, the weight reduction rate is getting higher and higher, and the requirements for the machining accuracy of the surface shape are also increasing, which the RMS of surface precision tends to reach
$1/50\ \lambda$
(about 12.7 nm) or even higher. The mirror processing process is carried out under the gravity environment on the ground, so how to eliminate the influence of gravity and ensure the consistency of space and earth is an important link in the processing. In this paper, an efficient and fast processing flow for 650 mm aperture space lightweight ULE mirror was given, and an active supporting gravity compensation device was designed. Through theoretical simulation analysis, the support point layout was optimized, and the final optimized support point number was 18 and the RMS of theoretical surface precision under gravity compensation was better than 1/100
$\lambda$
. The actual machining test showed that using this gravity compensation technique, the final machining surface precision of the 650 mm aperture mirror under the vertical optical axis was better than
$1/80\ \lambda$
- RMS(about 7.9 nm), which fully met the requirements of the optical system.