*2.1. Constellation Design Baseline Assumptions*

The achievable coverage of a constellation of remote sensing satellites is determined by both the orbit placements of the satellites within the constellation as well as the capability of the instruments carried on each satellite making the observations. Each individual satellite's orbit is defined by the traditional six Keplarian elements: eccentricity, semi-major axis, inclination, right ascension of the ascending node (RAAN), argument of periapsis (AoP) and true anomaly [12]. For purposes of remote sensing efficacy, the key design factors of the instrument itself include antenna configuration, number of parallel observations, and minimum observation signal strength. The principle design considerations for the constellation are the total number of satellites and their orbits relative to each other. Analyzing all the possible combinations of satellites, their orbits, and instrument configurations is not impractical. Therefore, we have made several assumptions and simplifications in order to isolate and evaluate the primary parameters driving the overall measurement coverage performance. This reduces the number of constellation design variables to a manageable and useful subset. The simulations below all include the following orbit and instrument configuration constraints and assumptions:


Using the above assumptions and constraints on the GNSS-R constellation configuration, the design parameters considered have been reduced to a manageable number: number of planes (incl. number of satellites per plane), inclinations of the planes, and minimum observation RCG. Each is explored individually in the sections below. The results and analysis are intended to examine the impacts of the design parameters on sampling and Earth coverage properties for possible future constellation missions.
