The author provides the background necessary to use the author's proprietary, dynamic data-driven predictive algorithms used in a PHM program. The author's results from using PHM for predicting equipment failures with 100% certainty, something that has been believed impossible since probability analysis began used by the U.S. military and government in the early 1960's. PHM programs allow for predicting spacecraft behavior by illustrating premature aging (a.k.a. non repeatable transient event) and then discriminate and identify premature aging from other normal occurring transient behavior. Premature aging is present prior to all equipment failures but is usually diagnosed as systemic noise or other non-repetitive transient events in telemetry behavior at the spacecraft factory during manufacturing and test, after factory testing is completed, on the launch pad, during launch if equipment telemetry is available and while in orbit. Using the author's proprietary, predictive algorithms, whose use began on the Air Force'd GPS program when the author was Boeing's GPS Space and Ground Segment Manager on contract to the Air Force to win funding for the GPS program, used predictive algorithms to predict GPS satellite atomic clock failures during system wide multi-service testing, The presence of premature aging is used to predict with certainty when the equipment will fail by converting the equipment telemetry to reliability data. PHM technology converts the performance data, known as equipment or product telemetry into a measurement of remaining usable life when the presence of premature aging is confirmed by a prognostic analysis. The use of the prognostic analysis is only valid for electrical and mechanical spacecraft related equipment and products that have passed qualification, certification and/or acceptance testing because the equipment will have have adequate design margins. PHM cannot be used to predict failures and determine design margins. Using Telemetry Science and PHM technology allows engineers to predict equipment failures weeks and months in advance with 100% certainty allowing many advantages including providing 100% reliable equipment, for increasing mission success at a lower mission cost. The authors describes the relationship between RF communications principles with the spacecraft telemetry behavior on spacecraft in Earth orbit, lunar orbit or interplanetary trajectory that allows the presence of premature aging to be identified with 100% certainty among other transient spacecraft equipment behavior in telemetry. This book can be used in conjunction with the author's others that describe PHM technology and its application on spacecraft.