VERITAS: the Boundary Conditions

Based upon 30 years of experience on the ridge of Mt. Hopkins $\sim$800 clear, moon-less hours can be expected in any year on average. The baseline VERITAS site in the Montosa Canyon, owing to its lower elevation compared to the Mt. Hopkins ridge, is expected to yield $\sim$900 clear, moon-less hours a year on average. The first three years of operation of the full VERITAS array would then have $\sim$2,700 hours of clear, moon-less conditions to carry out its scientific program. We identify four distinct modes of the full VERITAS array: mode A trains all seven telescopes on the scientific target to achieve the highest sensitivity and lowest energy threshold observations; mode B1 divides the full array into two sub-arrays (one sub-array consists of four telescopes and the second sub-array consists of three telescopes) so that two scientific programs can be carried out in parallel; mode B2 consists of two sub-arrays, each of three telescopes, for carrying out two scientific programs simultaneously while a single telescope monitors variable sources; mode C utilizes each telescope as a separate instrument to search for new sources and to monitor sources in active states.