"Gazing at the night sky full of stars has been a fascination for human beings for ages. The sun, the moon, and the stars have guided several phenomena that affect our lives. They have helped in navigation, occurrence of tides, have been a part of our myths and religions, and are a source of light and energy on the earth. From the human eye, life outside the earth seems so small but it was later realized that the earth is just a small part of this universe. The universe comprises of several galaxies, each of which comprises of stars, planets, asteroids, comets, meteors, and other heavenly bodies. The nineteenth century aroused man's interest in exploring space. Growing technology has fulfilled this dream. From rockets to space shuttles, and from human astronauts to robots, man has changed the entire scenario of space exploration"--