Which of the following is NOT an advantage of space-based telescopes over balloon-mounted telescopes?

Space-based telescopes offer a variety of advantages over balloon-mounted telescopes, primarily due to their positioning above the Earth's atmosphere. The correct choice highlights that space-based telescopes are not necessarily self-propelled, which sets them apart from balloon-mounted telescopes, which can be maneuvered to some extent within the atmosphere.

One of the main benefits of space-based telescopes is that they operate outside of the Earth's atmosphere, eliminating issues such as atmospheric distortions that can affect observations made from ground level or from balloons. This means they can capture clearer and more precise images of celestial objects. Additionally, space-based telescopes are typically designed to accommodate a larger array of instruments and equipment, allowing for more varied and comprehensive scientific research.

While both types of telescopes have unique capabilities, the notion that space-based telescopes are self-propelled is not accurate; they are positioned in orbit and do not require propulsion for their primary function of observation. Instead, they maintain their position through the balance of gravitational forces and their initial launch trajectory. This context clarifies why self-propulsion is not an inherent advantage of space-based telescopes when compared to their balloon-mounted counterparts.