The author provides a technical background necessary to use the proprietary, dynamic data-driven and model-based predictive algorithms used in a PHM program. The results from using PHM is predicting equipment behavior with 100% certainty, something that has been wrongly believed impossible since the use of probability analysis began by the U.S. military and government in the early 1960's. PHM programs allow for predicting normal spacecraft behavior and then illustrate the presence of premature aging (a.k.a. non repeatable transient event) and then discriminate and identify premature aging from other normal occurring transient behavior. Premature aging has been present for all spacecraft equipment failures but was usually diagnosed as 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 and on an interplanetary trajectory. Using the author's proprietary predictive algorithms, whose use began on the Air Force'd GPS program when the author was the Boeing GPS Space and Ground Segment Manager on contract to the Air Force to win funding for the GPS program, 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 from performance data 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 with 100% certainty. Using Telemetry Science and PHM allows engineers to predict equipment failures weeks and months with 100% certainty prior to their failure 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 other books that describe PHM technology and its application on spacecraft.