动量轮微振动扰振频谱对三反同轴相机的影响

Effects of Momentum Wheel Jitter Spectrum on Three-mirror-anastigmatic Imaging

随着遥感卫星分辨率的不断提高,动量轮扰振对遥感成像的影响逐渐成为卫星总体设计时需要关注的问题。目前对动量轮微振动的研究多侧重于时域分析,经常把卫星平台和载荷分立开来单独研究。鉴于平台和相机之间具有耦合作用,分立研究会带来较大误差。动量轮的输出响应并不是一个单一频率的时域信号,不同频谱对相机的影响不同,频谱分析往往更能反映问题。文章联合卫星平台和相机进行整星建模,分析了微振动扰振从动量轮处传递到相机光学元件的频谱特征,得到动量轮扰振不同频谱对相机造成的具体影响。分析结果显示,低于相机基频的动量轮扰振频谱造成相机光轴晃动,相机特征频率区间的扰振频谱不仅会放大光轴晃动,还会造成相机内部的光学元件光轴不一致。最后文章定量计算比较了这两种影响带来的MTF下降。

With the development of remote sensing satellite, the jitter of momentum wheels has more and more influence on the imaging quality. Current research of the momentum wheel vibration usually focuses on time domain, and it is usual to separate satellite platform from payload. As the platform and the payload have coupling relationship, the separate research will bring bigger deviation. On the other hand, the output of momentum wheel is not a single frequency signal, different spectrum has different effect on the camera, spectrum analysis tends to reflect more this problems like this. This paper combines the satellite platform and the camera in the same model, then analyses the frequency spectrum characteristic of the micro-vibration transmission from the momentum wheel to the optical mirrors. The result shows that the frequency spectrum below camera’s characteristic frequency mainly causes the optical axis jitter, while the frequency spectrum which fits the camera frequency causes the deviation of optical alignment as well as the optical axis jitter. Finally this paper analyses the optical axis jitter and the deviation of the optical alignment caused by momentum wheel jitter in the time domain, then calculates the decline of MTF caused by the two factors.