Orbit design based on global maps of telecom metrics

Abstract

This paper describes a tool to aid orbit design called the Telecom Orbit Analysis and Simulation Tool (TOAST). By specifying the six orbital elements of an orbit, a time frame of interest, a horizon mask angle, and some telecom parameters such as transmitter power, frequency, antenna gains, antenna losses, required link margin, and received threshold powers for the rates, TOAST enables the user to view orbit performance as animations of two- or three-dimensional telecom metrics at any point on the planet (i.e., on global planetary maps). Supported metrics include: (i) number of contacts; (ii) total contact duration; (iii) maximum communication gap; (iv) maximum supportable rate; and (v) return data volume at a best single rate or with an adaptive rate, along with; (vi) the orbiter's footprint and (vii) local solar times. Unlike other existing tools, which generally provide geometry, view periods and link analysis for an orbiter with respect to a single location on the planet, TOAST generates telecom performance metrics over the entire planet. The added capabilities provide the user an extra degree of freedom in analyzing orbits and enable the user to focus on meeting specific mission requirements, such as what data rates can be supported, what data volume can be expected, and what the time gap will be between communication periods. Although TOAST can be used to study and select orbits about any planet, we describe here its use for missions to Mars. TOAST is being used to analyze candidate orbits for the 2009 Mars Telecommunications Orbiter mission. Telecom predicts generated by TOAST for MTO orbit candidates are laying a foundation for selecting the MTO service orbit. This paper presents numerical simulations and telecom predicts for four candidate MTO orbits.