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我国研制的氢原子频标在陕西天台运行已二十多年了,对我们的时间工作起到了重要的作用,１９７９年至１９８０年间,陕西天台没有铯原子钟,氢频标曾作为基准钟,为我台原子时尺度的建立立下首功,１９８３年后,长期性能得到改进,１９９３年,在我国氢原子钟同行中,率先在国际时间局取到权,随着科学技术的发展,对时间工作精神的要求日益提高,陕西天台仍然需要世界一流水平的氢原子频标。 相似文献
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本文叙述了作为中国科学院陕西天文台原子时TA(CSAO)基准的两台氢原子频率标准的工作情况,短稳、长稳、准确度等技术指标的测试结果。 相似文献
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1976年,NBS 提出了采用射频检测的被动型氢原子频标的设计,经过几年的研制实践证明,这种有腔频伺服的被动型氢原子频标具有优良的长期频率稳定度性能,由于被动型氢原子频标无需满足振荡条件,腔的 Q 值可以选得较低,可以做成介质腔或其它结构形式的腔,缩小腔的体积,易实现氢原子频标的小型化。NBS 的小型化氢原子频标亦已制成,用陶瓷作腔介质,腔直经为14.6cm,高为13.7cm,腔的无载 Q 为600,激射器容积仅为20升。此小型化氢原子频标稳定度为5×10~(-15)/7天,漂移为1.2±5×10~(-18)/天,守时能力为5±3ns/7天。 相似文献
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1979年6月18日至27日,中国科学院陕西天文台、上海天文台和邮电部第一研究所联合组成试验小组,利用法德联合研制的“交响乐”通讯卫星,与法国巴黎天文台成功地进行了一次洲际时间比对试验。这次试验是通过上海虹桥地面站与法国普勒默—博杜地面站进行的,采用的是双向模式。在试验期间,同时接收Loran—C西北太平洋链的信号以及陕西天文台的BPL长波授时信号,并在上海与陕西之间进行了搬钟验证。试验结果表明,利用卫星进行时间比对的平均精度为±8ns(1σ),时间比对的准确度优于100ns。这个结果,在卫星低仰角(6°)的情况下,接近国际上同类试验的水平。本文概述了这次试验的一般情况以及对试验结果的简单分析。 相似文献
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在时频技术和设备研制方面颇有影响的美国(Datum)FTS(Frequency and Time Systems,Inc.)公司副总裁 David S.Briggs 先生于今年3月初访问陕西天文台,介绍 Sigma Tau 氢钟(ActiveHydrogen MASERs)及其它时频技术。原先在美国 NASA 哥达德航天中心工作的 Harry Peters 于1977年创建 Sigma Tau 公司。1982年为 VLBA 射电天文观测,开发研制新型氢脉泽——更新设计原子束光学系统、腔谐振调节 相似文献
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Solar System Research - Finding and studying possible collisions of asteroids approaching the Earth requires a significant amount of computation. This paper describes the R0 program created to... 相似文献
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Many asteroids with a semimajor axis close to that of Mars have been discovered in the last several years. Potentially some of these could be in 1:1 resonance with Mars, much as are the classic Trojan asteroids with Jupiter, and its lesser-known horseshoe companions with Earth. In the 1990s, two Trojan companions of Mars, 5261 Eureka and 1998 VF31, were discovered, librating about the L5 Lagrange point, 60° behind Mars in its orbit. Although several other potential Mars Trojans have been identified, our orbital calculations show only one other known asteroid, 1999 UJ7, to be a Trojan, associated with the L4 Lagrange point, 60° ahead of Mars in its orbit. We further find that asteroid 36017 (1999 ND43) is a horseshoe librator, alternating with periods of Trojan motion. This asteroid makes repeated close approaches to Earth and has a chaotic orbit whose behavior can be confidently predicted for less than 3000 years. We identify two objects, 2001 HW15 and 2000 TG2, within the resonant region capable of undergoing what we designate “circulation transition”, in which objects can pass between circulation outside the orbit of Mars and circulation inside it, or vice versa. The eccentricity of the orbit of Mars appears to play an important role in circulation transition and in horseshoe motion. Based on the orbits and on spectroscopic data, the Trojan asteroids of Mars may be primordial bodies, while some co-orbital bodies may be in a temporary state of motion. 相似文献
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In the text-books of astronomy, sections generally related to the Moon deal with the orbital elements of the Earth-Moon system such asa, e, i, ,
and the time of perigee passage. While the MEAN of the first of the three elements do not vary, mean longitude of the ascending node-mean longitude of the lunar perigee and the time of perigee passage undergoes secular as well as periodic changes due predominantly to the action of the Sun's gravitational attraction. While to a certain degree, explanations related to the calculation of the lunar orbit parameters are given, not a single graphical representation of these short- or long-periodic changes are presented. We allow the number of data related to these periodic changes must cover a large span of time; and if regression of the line of nodes or advances of the line of apses are to be graphically seen, data covering 18.61 and 8.85 yr, respectively, are needed. In this work we particularly aim at the graphical representation of the periodic changes of the line of nodes. 相似文献
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《Chinese Astronomy and Astrophysics》1982,6(3):233-242
We solve by an appropriate method the difficulty of near-commensurability, , in the motion of Hyperion (Saturn VII) and give a first-order solution of its motion. Our result explains two interesting observed features, the regression of the apsidal line and the exclusive occurrence of apocentre C conjunction of SVII and SVI. 相似文献