It is determined by their pay grade and their length of time in military service. Basic Pay, also known as Base Pay, is the same for all the services. The enlisted pay chart includes pay rates for all grades from E-1 through E-10 and for durations of military service ranging from less than four months to over 40 years.
Perturbation is an anxiety or disturbance, or is a cause of disturbance, or a from what is normal, especially when the deviation is caused by an outside influence.
When you're perturbed, you're upset by something, and rattled enough by it to be thrown off your usual calmness into a state of confusion. In astronomy, perturbation is defined as the effects on a large body when it is subjected to gravitational effects from more than one other large body..