Satellites and Orbits Once a vehicle has climbed above the atmosphere (approx 100 miles altitude for Earth) and achieved a velocity of 17,500 miles per hour, tangent to the Earths surface, it will be in orbit. To achieve orbit, a vehicle must be high enough to avoid drag from the atmosphere, with a tangent velocity (v) which matches the gravitational descent (g) and curvature of the planets surface. The velocity is fast enough that the vehicle “falls around the planet”. g v g v g v Newton’s Law of Gravity Where: F = Force G = Gravitational Constant m 1 = mass 1 m 2 = mass 2 r = distance between masses Notice from the equation that there is an “inverse square” function ( r 2 ). This means the further apart the masses are The weaker the gravitational force between them. Or, the higher the satellite orbit the weaker the force

Various Earth orbits approx. scale Cyan represents Low Earth Orbit, Yellow represents Medium Earth Orbit, Black dashed line represents Geo- synchronous Earth Orbit, Green dash-dot line - Global Positioning System (GPS) satellites, Red dashed line the orbit of the International Space Station (ISS). Blue dotted line Equatorial Orbit, Red dotted line is a Polar Orbit Halo Orbits above poles Orbit Altitude in Miles Low Earth Orbit (LEO) ,240 miles Medium Earth Orbit (MEO) 1,240-6,000-12,000 miles Geo-Synchronous Earth Orbit (GEO) ~22,300 miles. High Earth Orbit (HEO) Above 22,400 miles. Satellite Orbits Source - Wikipedia S. Akerley 2011

Orbital Satellites & Debris Courtesy NASA S. Akerley 2011

2010 TK7 is an Earth Trojan Asteroid. It has a type of orbit relative to the Earth- Sun gravitational neutral points (Also See Gravity Wells), which are called LaGrange Libration Points. In 2010/2011, TK 7 was at the near-Earth end of its tadpole, 3 which facilitated its discovery. 3 From Wikipedia, the free encyclopedia LaGrange Libration Points And Trojan Asteroids S. Akerley 2011