Answer
The answer is orbit. Eleanor Helin's initial observation of 4015 Wilson–Harrington allowed her to establish its orbit. This was achieved by using astrometric techniques to measure the position and velocity of the asteroid over time, allowing its orbital parameters to be calculated. These parameters include the asteroid's semi-major axis, eccentricity, inclination, and orbital period, which define the shape, size, and orientation of its orbit around the Sun.