MOUSE was conceived by Kenneth W. Gatland, Anthony Kunesch, and Alan Dixon of England. Dr. S. F. Singer of the University of Maryland designed the MOUSE and constructed the model on exhibit. The model displays some of the earliest solar cells produced by the Bell Telephone Laboratories. The MOUSE is from S. F. Singer. Agena-B [Illustration: 31. Thor-Agena launch vehicle and its satellite payload before launch.] The Agena launch vehicle has been an integral part of both unmanned and manned space programs. Flown as an upper stage on Thor and Atlas boosters, Agena orbited an impressive roster of spacecraft including the Echo communications satellites, the Ranger and Lunar Orbiter Moon probes, and the Mariner vehicles that traveled to Venus and Mars. As the target for docking experiments during Project Gemini, Agena made substantial contributions to the eventual success of the Apollo program. The vehicle earned the distinction of being the first to place a payload in polar orbit, and was also the first to achieve circular orbit. The Agena engine was the first which could be stopped and restarted in space. The Agena launch vehicle was developed and manufactured by the Lockheed Missiles and Space Company for the United States Air Force. Length 7.1 m. (23.25 ft.) Diameter 1.5 m. (5 ft.) Weight Empty 674 kg. (1484 lb.) Fuel Unsymmetrical dimethylhydrazine Oxidizer Inhibited red-fuming nitric acid Thrust 7260 kg. (16,000 lb.) The Agena-B is from the United States Air Force and the Lockheed Missile and Space Company. [Illustration: 32. The Agena Target Docking Vehicle seen from the _Gemini 8_ spacecraft during rendezvous approach.] Science Satellites [Illustration: 33. _Vanguard 1_, second American satellite launched. Information from _Vanguard_ showed that the Earth is not quite round.] The first artificial earth satellites were sometimes called “long-playing rockets” because they carried the same instruments and investigated the same problems as had the sounding rockets. The great advantage of the satellite was its ability to provide a continuous flow of information for long periods of time. The first science satellites were the forerunners of later vehicles that would demonstrate the direct benefits that satellites could offer to such varied fields as weather observation and communication. The advent of the earth satellite provided scientists with a new and valuable research tool. Science satellites have been used for such tasks as solar and astronomical observations, biology experiments, or atmospheric investigation. Explorer 1 (launched January 31, 1958) and Vanguard 1 (launched March 17, 1958), the first American earth satellites, carried scientific payloads into space.