It sent a hydrogen maser, a highly accurate frequency standard, into space to measure the rate change of a clock in lower gravity with high precision.

Examples of primary time, (i.e., frequency standards) are caesium standards and hydrogen masers.

Data received at each antenna in the array include arrival times from a local atomic clock, such as a hydrogen maser.

Among the most stable frequency references in the world are caesium standards, including caesium fountains, and hydrogen masers.

In the active hydrogen maser, the cavity oscillates by itself.

He also participated in developing an extremely stable clock based on a hydrogen maser.

The development of a passive hydrogen maser for QZSs was abandoned in 2006.

Ramsey could therefore confidently proceed with the building of the hydrogen maser.

Another test involving a space-borne hydrogen maser increased the accuracy of the measurement to about 10 (0.01%).

Atomic hydrogen determines the frequency of hydrogen masers which are used as precise frequency standards.