Beginning in the 1600s, astronomers had realized that their telescopes had serious limits. They had managed to build stronger and better telescopes, but no matter how strong the new telescopes were, they were less than satisfactory. The astronomers were able to view objects only when the objects were in view of Earth. At the same time, however, Earth’s light and atmosphere made it difficult to see many heavenly objects. Thanks to the Hubble Telescope, this has been solved, because the Hubble is not just a telescope. It is a digital camera on a satellite that travels about 370 miles (600 km) above Earth, making a complete orbit every ninety-seven minutes. Since 1990, Hubble has been able to take digital pictures of planets, galaxies, comets, and more, and these are sent back to Hubble headquarters for scientists to study.