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航天器轨道精确测定重要环节之一是有效地消除观测系统误差,在轨道测量数据处理时,一类是利用轨道约束自校准技术来估算和校准系统误差,另一类可以应用测元差分方法来消除系统误差(例如导航卫星测定目标)。本文提出一种新的差分技术,即利用观测数据时序差分消除系统误差技术,并推导相应确定航天器轨道的公式。 相似文献
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ATLAS2K--以信号描述为核心的可扩展的可移植的自动测试语言 总被引:2,自引:0,他引:2
详细介绍了以信号描述为核心的新一代测试语言ATLAS2K的特点及层模型,并提出了ATLAS2K在自动测试设备ATE中的应用。 相似文献
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Interplanetary transfer of photosynthesis: an experimental demonstration of a selective dispersal filter in planetary island biogeography 总被引:2,自引:0,他引:2
Cockell CS Brack A Wynn-Williams DD Baglioni P Brandstätter F Demets R Edwards HG Gronstal AL Kurat G Lee P Osinski GR Pearce DA Pillinger JM Roten CA Sancisi-Frey S 《Astrobiology》2007,7(1):1-9
We launched a cryptoendolithic habitat, made of a gneissic impactite inoculated with Chroococcidiopsis sp., into Earth orbit. After orbiting the Earth for 16 days, the rock entered the Earth's atmosphere and was recovered in Kazakhstan. The heat of entry ablated and heated the rock to a temperature well above the upper temperature limit for life to below the depth at which light levels are insufficient for photosynthetic organisms ( approximately 5 mm), thus killing all of its photosynthetic inhabitants. This experiment shows that atmospheric transit acts as a strong biogeographical dispersal filter to the interplanetary transfer of photosynthesis. Following atmospheric entry we found that a transparent, glassy fusion crust had formed on the outside of the rock. Re-inoculated Chroococcidiopsis grew preferentially under the fusion crust in the relatively unaltered gneiss beneath. Organisms under the fusion grew approximately twice as fast as the organisms on the control rock. Thus, the biologically destructive effects of atmospheric transit can generate entirely novel and improved endolithic habitats for organisms on the destination planetary body that survive the dispersal filter. The experiment advances our understanding of how island biogeography works on the interplanetary scale. 相似文献
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