The flight model of the laser cooled cesium atomic clock, PHARAO, has been qualified for operation in space. The clock has passed the vibration, thermal and electromagnetic compatibility tests required to fly in low Earth orbit (400 km). On ground, the clock realized a typical frequency stability of 3.0x10-13 t-1/2 with an estimated accuracy of 2.3x10-15. Frequency comparisons with the SYRTE primary frequency standard FOM agree within their stated accuracies. Because PHARAO is optimized for the longer interaction times possible in microgravity, we expect a frequency stability of 1.1x10-13 t-1/2 and a frequency accuracy of 1.1x10-16 for operation in space. The clock has been delivered to the European Space Agency for the assembly of the ACES payload and is scheduled to be launched into space in 2021.

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天基主频标准PHARAO的资质和频率精度

激光冷却铯原子钟的飞行模型PHARAO已获得在太空运行的资格。该时钟已通过在低地球轨道（400 公里）飞行所需的振动、热和电磁兼容性测试。在地面上，时钟实现了 3.0x10-13 t-1/2 的典型频率稳定性，估计精度为 2.3x10-15。与 SYRTE 主要频率标准 FOM 的频率比较在其规定的精度范围内一致。由于 PHARAO 已针对微重力条件下可能的更长交互时间进行了优化，因此我们预计在太空中运行时频率稳定性为 1.1x10-13 t-1/2，频率精度为 1.1x10-16。该时钟已交付给欧洲航天局用于组装 ACES 有效载荷，并计划于 2021 年发射到太空。