Position Sensing and Formation Flying Using Optical Beacons

One way of imaging exoplanets around nearby stars is to use a starshade in conjunction with a space telescope. Typically, the starshade, which resembles a sunflower in outline, is ~ 30 meters in diameter. The starshade is flown about 50,000 km in front of the telescope, and when positioned directly in the telescope’s line of sight to the star, blocks the starlight, casting a deep shadow onto the telescope. Exoplanets orbiting the star and having a small angle to the line of sight will be visible because the starlight is extinguished. During the observation period, the position of the telescope needs to be maintained within about 1 m of the center of the shadow for maximum shading of the starlight.