For context, a femtosecond (1×10−15 s) is to a second what a second is to about 31.71 million (31.71×106) years and an attosecond (1×10−18 s) is to a second what a second is to about 31.71 billion (31.71×109) years.
The MAC is a passive atomic clock, incorporating the interrogation technique of Coherent Population Trapping (CPT) and operating upon the D1 optical resonance of atomic Rubidium Isotope 87.
A rubidium clock is basically a crystal oscillator locked to an atomic reference. The rubidium physics package serves as a passive discriminator, producing an error signal that varies in magnitude and sense as a function of the difference in frequency between the applied RF excitation and the atomic resonance. Rubidium is a small, low weight and low cost atomic standard that is quickly activated. It delivers good phase noise performance, exhibits low G force sensitivity, and operates in a wide temperature range. These advantages make it an ideal alternative to quartz technology. Rubidium clocks provide rapid operational stability after turn on, exhibit better long term aging characteristics, and are less susceptible to physical effects.