•A telescope in space does not suffer from light pollution (Figure 1) caused by neighboring countries and cities. The earth's atmosphere introduces considerable distortion in images (properly called optical aberration). The resolutive capacity of large land-based telescopes is therefore greatly reduced.
•An observatory in space should not look through miles of atmosphere, and always has performance close to its theoretical maximum. This problem is today partially solved even on the ground. using adaptive optics techniques, which are however complex and they do not solve the problem altogether. ( Figure 2)