Useful life means the relevant period of distance and/or time over which compliance with the relevant gaseous and particulate emission limits has to be assured.
Useful beam means the radiation emanating from the tube housing port or the radiation head and passing through the aperture of the beam-limiting device when the exposure controls are in a mode to cause the system to produce radiation.
Direct Expenses means “Operating Expenses” and “Tax Expenses.”
Protected Space Operations means all Launch or Transfer Vehicle activities, ISS activities, and Payload activities on Earth, in outer space, or in transit between Earth and outer space in implementation of the IGA, MOUs concluded pursuant to the IGA, implementing agreements, and contracts to perform work in support of NASA’s obligations under these Agreements. It includes, but is not limited to:
useful heat means heat produced in a cogeneration process to satisfy economically justifiable demand for heating or cooling;