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To obtain higher navigation accuracy of skylight polarization,the polarization model for skylight was researched.An automatic detecting system of skylight polarized pattern was designed to get a large number of images to build an accurate model of skylight.The system overcomes the complex operation and the low efficiency from traditional detecting systems.It integrates a camera and the control system of precision rotating platform in an acquisition system to acquire the polarized images rapidly and easily in a key gathering a group of images.The test indicates that the acquisition system can get all of images in the angle that we expect,and can obtain images with a clear polarized pattern.Furthermore,the detecting accuracy is better than 0.237 5(3σ) gray level(8 bits) for light intensity and average time-consuming is 3.02 s for every measuring point.These results demonstrate that the system has higher detecting efficiency and can execute an efficient detection of skylight polarized pattern.

This paper reported on the microfabrication of alkali metal vapor cells based on the two-step low temperature anodic bonding for the chip-scale integration of atomic clock,atomic magnetometer,atomic gyroscope and other atomic devices.Cell structures were fabricated by Micro-electromechanical System(MEMS) bulk silicon process,and the etched silicon with cells was firstly bonded to Pyrex glass to fabricate preformed chambers by the standard anodic bonding process.Then,nitrogen buffer gas and micro-scale alkali metal(rubidium or cesium) were introduced into the preformed cells.The two-step anodic bonding process was used to seal the cells at a temperature lower than the paraffin flash point(198 ℃).In the first step,bonding voltage was lower than the breakdown voltage of nitrogen buffer gas to pre-seal the cells.In the second step,the bonding was in air atmosphere,and the bonding voltage increased up to 1 200 V to strengthen packaging quality.A high power laser system locally heated the micro-scale alkali metal packets to release alkali metal,and a uniform coating of paraffin was formed on cell walls to prolong the life of the polarized atoms.With proposed method,95% bonding is achieved by the two-step low temperature anodic bonding,and the alkali rubidium still has a metallic luster after anodic packaging.The achieved minimum volume of double-cells is about 6.5 mm×4.5 mm×2mm.Rubidium absorption spectrum shows that alkali rubidium is effectively encapsulated in the cells.It is feasible to fabricate MEMS alkali metal vapor cells by the two-step low temperature anodic bonding process.

On the basis of the principle of a VISNAV sensor,this paper researches how to determine the vision-based relative state between two satellites with disturbances.By taking the VISNAV sensor as a relative state sensor,the problem mentioned above is solved by a modified Kalman filter algorithm.In consideration of the relative orbit dynamics equation with disturbance and the relative attitude kinematic equation,it gives modified discrete equation and a calculation method for the error covariance matrix.By which the method avoids the complicated real-time operations of large dimensional matrices in every loop and reduces computation amounts.Finally,the corresponding modified Unscented Kalman Filter(UKF)method followed by a numerical simulation experiment is performed under STK and MATLAB.Results demonstrate that the method is feasible,effective and has good convergence.Under disturbance condition,its determination accuracy in 200 m is an angle second level for the relative attitude and a millimeter level for the relative position,which meets the requirements of determining the relative state between two satellites in a shorter distance.