Space applications of telerobots are characterized by significant communication delays between operator commands and resulting robot actions at a remote site. A high degree of telepresence is also desired to enable operators to safely conduct teleoperation tasks. This paper provides tools for quantifying teleoperation system performance and stability when communication delays are present. A general multivariable system architecture is utilized which includes all four types of data transmission between master and slave: force and velocity in both directions. It is shown that a proper use of all four channels is of critical importance in achieving high performance telepresence in the sense of accurate transmission of task impedances to the operator. It is also shown that transparency and robust stability (passivity) are conflicting design goals in teleoperation systems. The analysis is illustrated by comparing transparency and stability in two common architectures, as well as a recent ''passivated'' approach and a new ''transparency optimized'' architecture, using simplified one degree of freedom examples.
