Design And Test Of Large Size Baffle For Off-axis Three-mirror Space Optical Remote Sensor

The space optical remote sensor has great significance of scientific research andmilitary affairs in the observations of the earth and the outer space. As the observationrequirement and the development of the space optical remote sensor with largeaperture, wide coverage, long focal length, large field of view, high resolution andlightweight is much in demand, the optical system changes from refractive system toreflective system, from the on-axis Cassegrain refractive optical system to the off-axisrefractive optical system. The on-axis optical systems have small field of view andcentral obscuration, which reduces the light-gathering capability of the remote sensor;but the off-axis refractive optical systems are just the reverse, which eliminate thecentral obscuration. In this paper, the off-axis Wetherell TMA (three mirroranastigmat) optical system is adopted in the space optical remote sensor.The baffle is an important component of the space optical remote sensor, whichis the main way to weaken the stray light from the out-of-field radiation source, andthe imaging quality of the space optical remote sensor is dependent on the baffle’sperformance. The baffle’s geometrical form, the locations and the number of the vanestructure, and coating a highly absorbing paint can attenuate stray light into the opticalsystem, and thereby ensure the space optical remote sensor to obtain a higher signalnoise ratio.The mechanical properties should be considered in the process of designingbaffle’s layout. During the transportation, rocket launching and being in orbit, theharsh mechanical environments (such as static overload, dynamic load, randomvibration) and thermal environments of the space sensor require that the baffle has tohave sufficient strength and rigidity and high reliability, to avoid deformation crackand damage, and affecting the structural stability of the support frame, and reducingthe imaging quality of the optical system.In this paper, a large size baffle layout will be designed to meet the off-axisWetherell TMA optical system. The baffle is made of carbon fiber reinforced polymer(CFRP). The modal analysis and frequency response analysis are conducted with the FEM analysis, helping to understand the dynamics function of the conjunction of thebaffle and the supporting frame. The conjunction undergos the mechanical vibrationtest, the thermal vacuum test and the thermal optical test. The baffle never tearing andbeing broken shows the accuracy of dynamics analysis and the baffle’s having enoughstrength. After the test, the MTF of the optical remote sensor can still reach to0.2,verifying that the large baffle has no effect on the structural precision of thesupporting frame, and having no differences with the MTF before the test, showingthat the baffle has better structure stability and reliability. The baffle can meet therequirements of space applications.