中国每年将10%的观测时间（约450小时）交给其他国家的科学家。
China is giving 10% of its observation time, around 450 hours a year, to scientists from other countries.
对于获得更新更大的8米级望远镜或者哈勃太空望远镜的观测时间仍具有挑战性。
Obtaining observing time on one of the newer, more powerful 8-meter telescopes or on the HST was, and remains, more challenging.
目标运动的基本假设是在一段观测时间中保持常速度，并有随机速度扰动。
A basic assumption concerning source motion is to consider it to be of constant velocity with random perturbations over the observation intervals.
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