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Download Notes: Unmanned Space Programs
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Unmanned Space Programs What is the difference? Artificial Earth Satellite A space vehicle built to orbit the earth and perform a specific function Space Probe Leaves the vicinity of Earth to study planets, the sun, or another aspect of the heavens Determining the Orbit of a Satellite Three kinds of orbits around earth: 1. Low Earth orbit (weather & cell phones) 2. Polar orbit (same light for comparison) 3.Geosynchronous orbit (same viewpoint) Two factors : 1. Gravity pulling it downward 2. Its sideways speed Artificial Earth Satellites Two types: Scientific satellites Applications satellites Applications satellites: Communications Weather Earth survey/resources Navigation (GPS) Surveillance (“spy”) satellites Missile launch warning satellites Temporary satellites (such as the unmanned replenishment vehicles for the International Space Station) How accurately can the GPS determine a location on earths surface? WITHIN 3-5 METERS A satellite in a low Earth orbit is moving ________ than a satellite in a geosynchronous* orbit. FASTER *the orbital period of the satellite is exactly the same as the earth’s rotational period – 24 hours, and it is about 22,250 miles above the earth Specialized Probes Why they are “special”: They visit comets or asteroids They are placed in special orbits to observe the sun or some other aspect of the heavens A ________________is placed between two massive objects at a location where their gravities exactly balance each other. It orbits around this point in space. HALO ORBIT Space Missions Ways that probes may carry out their missions: Fly by Orbit Crash into Land on Detach a lander Leave the solar system completely (headed toward stars) Planets, moons, asteroids, comets, etc. Why missions to Mercury and Pluto are difficult: Mercury – close to sun, high temperatures, strong radiation Pluto – distant from earth, probe would require a large boost or special propulsion system Mercury Ten years ago, on August 3, 2004, NASA’s MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft blasted off from Cape Canaveral, Florida, for a risky mission that would take the small satellite dangerously close to Mercury’s surface, paving the way for an ambitious study of the planet closest to the Sun. The spacecraft traveled 4.9 billion miles (7.9 billion kilometers) — a journey that included 15 trips around the Sun and flybys of Earth once, Venus twice, and Mercury three times — before it was inserted into orbit around its target planet in 2011. Pluto: New Horizons Operators at the Johns Hopkins University Applied Physics Laboratory are preparing to “wake” the spacecraft from electronic hibernation on Dec. 6, when the probe will be more than 2.9 billion miles from Earth. Distant observations of the Pluto system begin Jan. 15 and will continue until late July 2015; closest approach to Pluto is July 14.
