A dramatic exchange bias behaviour was found in superior soft Co58Fe5Ni10Si11B16 amorphous ribbons with proper thermomagnetic annealing conditions. This characteristic, which was directly obtained at room temperature, is quite different from that of the traditional ferromagnetic–antiferromagnetic system. The observation of microstructure indicated that the matrix of the annealed ribbons with the exchange bias behaviour includes a few crystalline phases. The magnetic domains of the ribbon surface were scanned to clarify the configuration of local magnetic moments. A subsequent magnetic torque measurement revealed that unidirectional magnetic anisotropy was induced in the amorphous ribbons with a longitudinal field. The obtained evidence supports our point of view that the local crystalline phases in the ribbons along with the longitudinal thermomagnetic treatment are the key factors in promoting the formation of an exchange bias. A simple phenomenological discussion was developed to expound this interesting behaviour in ribbons.

No abstract

High-precision state estimation lies at the core of asteroid exploration. This paper investigates the high-precision state estimation methods in asteroid approaching, orbiting, and touching phases. The system and measurement models are established, and state estimation strategies are designed respectively for each phase. In the approaching phase, the star image is used to directly determine the relative orbit of the spacecraft to the target asteroid. To improve the optical state estimation precision, a deceleration-orientation-deceleration strategy is developed. In the orbiting phase, coupled orbit-attitude estimation is realized based on the terrain features of the asteroid, and the effect of dynamic error on the accuracy of state estimation is analysed. Then, a decoupled orbit-attitude state estimation method is developed to avoid the affection of dynamic error. In the touching phase, lidar measurement is used to determine the relative orbit and attitude of the spacecraft with respect to the landing spot. Based on the triple-stage state estimation framework proposed in this paper, the relative state error of the spacecraft converges from 100km level to 1mm level.