Uhrich P M, Guillernot P, Aubry P, Gonzalez F, Salomon C
Lab. Primaire du Temps et des Frequences, Bur. Nat. de Metrol.
IEEE Trans Ultrason Ferroelectr Freq Control. 2000;47(5):1134-9. doi: 10.1109/58.869050.
Atomic Clock Ensemble in Space (ACES) is a project of the European Space Agency on-board the future International Space Station (ISS). The payload consists mainly of two atomic frequency standards, one space hydrogen maser (SHM) prepared by the Observatoire de Neuchatel (Switzerland), and one cold atom caesium clock called PHARAO prepared by the CNES (France), with the participation of the BNM-LPTF, the ENS-LKB, and the CNRS-LHA. Because of the anticipated performances of these clocks on-board the ISS, the requirements of the links between the payload and the clocks on the Earth are at the limits of the known potential of the optical or microwave techniques. The microwave link (MWL) requirements are described in this paper. Taking into account the characteristics of the ISS orbit, and fixing an arbitrary limit to the additional noise brought to the clock readings by the MWL, the computation of the required stability leads to two kinds of requirements: the first one at the subpicosecond level over each single continuous pass of the ISS above any Earth station, and the second one at the level of one part in 10(16) and below over a one day or more averaging period. Moreover, the ISS orbit parameters should lead to a knowledge of the ACES clock position at the m level, and of the ACES clock speed at the mm/s level.
空间原子钟组（ACES）是欧洲航天局在未来国际空间站（ISS）上开展的一个项目。该有效载荷主要由两个原子频率标准组成，一个是由瑞士纳沙泰尔天文台研制的空间氢脉泽（SHM），另一个是由法国国家空间研究中心（CNES）研制的名为PHARAO的冷原子铯钟，其中法国国家计量与测试实验室（BNM-LPTF）、巴黎高等师范学校-路易·巴斯德实验室（ENS-LKB）和法国国家科学研究中心-阿道夫·洛朗实验室（CNRS-LHA）参与了该研制工作。鉴于这些时钟在国际空间站上预期的性能表现，有效载荷与地球上的时钟之间链路的要求已达到光学或微波技术已知潜力的极限。本文描述了微波链路（MWL）的要求。考虑到国际空间站轨道的特性，并对微波链路给时钟读数带来的额外噪声设定一个任意限制，所需稳定性的计算得出了两种要求：第一种要求是在国际空间站每次连续飞越任何地面站上空时达到亚皮秒级，第二种要求是在一天或更长平均周期内达到10的16次方分之一及以下水平。此外，国际空间站轨道参数应能使人们了解ACES时钟位置达到米级精度，以及ACES时钟速度达到毫米/秒级精度。
