The Hubble Space Telescope, the most complex and sensitive optical telescope ever made, was built to study the cosmos from low-Earth orbit for 10 to 15 years or more. The Compton Gamma Ray Observatory is a complex spacecraft fitted with four different gamma ray detectors, each of which concentrates on different but overlapping energy range and was designed to help astronomers learn about the most powerful celestial bodies and events in the universe. This educational product for grades 5 and up contains detailed descriptions to assemble a Hubble Space Telescope model and a Compton Gamma Ray Observatory model.