THz source requirements for astrophysics receivers

A discussion is given of current and projected needs for local oscillators for submillimeter and terahertz receivers used in astrophysical and astrochemical applications. Arguments are given for frequency range, tunability, power, and noise specifications for local oscillators in various applications. The receivers will generally employ SIS or Schottky diode mixers, and these may be used in single elements, receiver arrays or aperture synthesis interferometry, each of which has differing requirements. The platforms may be ground-based, probably on high mountain sites, balloons, air or space-based, again each demanding somewhat varying local oscillator capabilities