Space Missions — Flashcards

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Space missions are of two main types: 1) missions that place artificial satellites in orbit around the earth for research and useful applications, and 2) missions that send spacecraft to outer space t…

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An artificial satellite is a manmade object revolving around the earth or any other planet in a fixed orbit. It is used for communication, weather study, navigation, and observation.

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A satellite needs a tangential velocity called critical velocity. At that speed, the gravitational force provides the centripetal force needed to keep it revolving in orbit.

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Centripetal force = gravitational force (m v_c^2)/(R + h) = (G M m)/(R + h)^2 So, v_c^2 = (G M)/(R + h) Therefore, v_c = sqrt((G M)/(R + h)) Here, v_c is critical velocity, G is gravitational constant…

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No. Critical velocity does not depend on the mass of the satellite. It depends on the mass of the earth and the height of the orbit.

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Critical velocity decreases when the height of the orbit increases. A higher orbit needs a smaller orbital speed than a lower orbit.

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This is a High Earth Orbit. A satellite at this height takes around 24 hours for one revolution, so if it moves parallel to the equator, it appears stationary with respect to the earth. Such satellite…

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Geostationary satellites orbit above the equator. Because of this, they cannot observe polar regions properly. For polar regions, elliptical medium earth orbits passing over the polar region are used.