Dynamic link analysis tool for a telemetry downlink system

Abstract

A model is described in this paper for dynamic S-band telemetry link analysis for the spacelift range system (SLRS). From an operational standpoint, this tool determines telemetry link closure of a launch vehicle to different ground terminal sites. This model allows the users to react accordingly to any anomalies and to perform subsequent corrective actions. One application of the tool was to determine antenna characteristics required for the support of the SLRS missions. The application of the model is of considerable importance to the Air Force, Navy, and the nation. Specifically, the software's ability to analyze the various launches is critical to the National Defense and the National Space program of the United States. The Aerospace Corporation developed the dynamic link analysis (DLA) tool for SLRS S-band telemetry. This tool determines the telemetry link margin during the flight of a launch vehicle as monitored by the SLRS. The model takes into account several dynamic effects in calculating the link budget including transmit antenna pattern, space loss, beam spreading, polarization diversity, rain attenuation, and plume attenuation. The trajectory of the launch vehicle in addition to its orientation is also taken into account. As a result, a clock and a cone angle are calculated in order to compute the dynamic antenna gain. Also, an aspect angle is calculated to compute the impact of plume attenuation. A slant range is computed at each instant in time to calculate the corresponding space loss. Finally, a link margin is determined and plotted versus time. Different aspects of the analytical model with respect to the waveform, transmitter, receiver, plume effects, antenna pattern, and dynamics of a launch vehicle for the SLRS S-band telemetry system are presented in this paper. The results of several analysis tools are presented for different launch vehicles and their associated flight trajectories. This sophisticated tool provides a new, powerful, and useful capability to perform trade studies and to analyze link closure for generalized launch vehicle S-band telemetry to its appropriate range ground sites.