Iterative method of baffle design for modified Ritchey-Chretien telescope

Stray light control for the space-agile optical system with a pointing mirror

The space-agile optical composite detection (SOCD) system with a pointing mirror possesses flexible and fast response ability. Like other space telescopes, if the stray light is not properly eliminated, it may result in a false response or noise that floods the real light signal due to the low illuminance and large dynamic range of the target. The paper shows the optical structure layout, the decomposition of the optical processing index and roughness control index, the stray light suppression requirements, and the detailed stray light analysis process. The pointing mirror and ultra-long afocal optical path increase the difficulty of stray light suppression in the SOCD system. This paper presents the design method of a special-shaped aperture diaphragm and entrance baffle, black baffle surface testing, simulating, selection, and stray light suppression analysis process. The special-shaped entrance baffle has a significant effect on the suppression of stray light and reduced dependence on the platform posture of the SOCD system.

Optical design and stray light control for a space-based laser space debris removal mission

In low-Earth orbit, the already existing population of small and medium debris (between 1 cm and several dozens of cm) is a concrete threat to operational satellites. A space-based laser space debris removal (SLDR) system that can remove hazardous debris around selected space assets appears to be a flexible and effective project. To achieve high-precision tracking and emitting, the optical system of the SLDR mission includes a target-detection telescope and emitting telescope, adopting a common light path structure. The optical design results, system performance, tolerance budget, and detailed stray light control design are presented in this paper. The large-aperture off-axis two-mirror beam-narrowing system characteristics are also discussed in terms of stray light control. This paper will present the lateral-displacement (LD) setting, two-stage fore baffle design, black baffle surface selection, and opening direction of the telescope door. The results showed that the stray light elimination reaches a 10^-9 order, meeting design requirements.

Optical design of the visible telescope for the SVOM mission

This paper describes the optical design of the visible telescope (VT), which is the primary payload for the Chinese-French Space-based multi-band astronomical Variable Objects Monitor (SVOM) mission, for the detection and observation of high-redshift gamma-ray bursts. The VT aims at reaching a limiting magnitude of +22.5Mv with the exposure time of 300 s in the 630 km Sun-synchronous orbit with an inclination of 30°. The VT, also known as the fine guidance sensor for the SVOM, aims to measure the relative performance error (RPE) of the platform during the tracking and provide the RPE to the platform to correct its stability. The optical design is presented in this paper. The mirror manufacture and test results are presented. The optical system performance, tolerance budget, thermal analysis, and stray light design of VT are fully analyzed. Finally, the diffraction encircled energy and point source transmittance are tested in the lab for the finished telescope.

Design of a built-in baffle for a Ritchey-Chretien optical system

A baffle effectively prevents direct rays of stray light from entering an optical system. Existing design methods can result in very long outer baffle lengths, increasing the weight and volume of the optical system, or large secondary mirror baffle sizes, increasing the central obscuration and resulting in the reduction of the illumination beam on the image. To overcome these challenges, a design method for a built-in baffle is presented. The designed built-in baffle for a typical Ritchey-Chretien optical system is compared with a conventionally designed baffle. The results show that when the length of outer baffle is shortened from 3456 to 2349.9 mm, the modulation transfer function (MTF) increases from 0.361 to 0.421 in case 1, and when the length is shortened from 3456 to 1924.2 mm, the MTF increases from 0.361 to 0.408 in case 2. Meanwhile, the stray light suppression capability is close to that of the traditional method.