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TWTAs (Traveling Xhuna Tube Amplifiers) are presently the primary life-limiting element of a communications satellite transponder. Satellite operators rely on spare ‘TWTAs to ensure that most of the transponders will be operating at the spacecraft end·of-life. We wish to track the °health° of the operating TWTAs in order to accurately predict the remaining useful lifetime of the satellite transponder. This information is very useful for system planning and risk assessment. The primary failure mechanism of a TWTA is cathode deactivation, symptoms of which are measurable from an earth station. Present testing methods require the interruption of the communications traffic signal, which leads to a loss in revenue generated by the satellite. We present new methods to test TWTAs without significant interference to the communications signal. These methods include the use of test—tone signals and spread spectrum techniques. The test—tone method is readily implemented using commercially available hardware. The spread-spectrum technique requires customized hardware, and so is more expensive. Finally, the data from these tests can be inserted into a transponder reliability model. The model is then used to predict the availability of the satellite transponder, up to and including the end-ef-life of the satellite. / Master of Science

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This report describes the study of a new approach to resolve pulse radar range bin ambiguity problem. The nature and the cause of the problem are discussed, and various methods presently used to solve this problem are presented. The report points out the disadvantages of these methods and, thus, introduces a new approach to resolve the radar range bin ambiguity problem by examining the reasonableness of the trajectory of the object being traced. Necessary algorithm and computer programs to support the study are given in Appendices I, II, and III.

The solution to the problem of a satellite with a small constant thrust and under the influence of a central force field presents difficulties due to equations non-linearity. An investigation was made to determine what range of values of the thrust parameter could be utilized to obtain a valid approximate solution for the case of tangential thrusting. The investigation was accomplished by developing programs for the 1620 High Speed Digital Computer, since the solution to the exact and approximate equations would otherwise be exceedingly laborious. Under the assumption of no atmosphere, and neglecting the earth's oblateness, the study showed that the validity of the Kryloff and Bogoliuboff method was dependent on both the specific thrust aud the vehicle speed. For a Speed corresponding to an orbit of smaller eccentricity it was determined that the method of Kryloff and Bogoliuboff remained valid for larger values of W than when V was a velocity corresponding to an orbit with a greater eccentricity. The method of Kryloff and Bogoliuboff represents a practical approach to the solution of satellite motion both from the aspect of ease of application and reasonable calculation times. / Master of Science