The purpose of a telemetry system is to reliably and transparently convey
measurement information from a remotely located data-generating source to
users located in space or on Earth. Typically, data generators are scientific
sensors, science housekeeping sensors, engineering sensors, and other subsystems
aboard a spacecraft.
In the past, most of the telemetry resources used by a science mission have
been wholly contained within a project office and are completely dedicated to
that mission. The lack of effective standardization among various missions
forces the multimission tracking network to implement the lowest level of
telemetry transport service, i.e., bit transport. Higher-level data delivery
services, oriented more toward computer-to-computer transfers and typical of
modern commercial and military networks, had to be custom designed and
implemented on a mission-to-mission basis.