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[nb 1] Earth's orbital speed averages 29.78 km/s (19 mi/s; 107,208 km/h; 66,616 mph), which is fast enough to cover the planet's diameter in 7 minutes and the distance to the Moon in 4 hours. [3] The point towards which the Earth in its solar orbit is directed at any given instant is known as the "apex of the Earth's way". [4] [5]
Transatmospheric orbit (TAO): geocentric orbits with an apogee above 100 km and perigee that intersects with the defined atmosphere. [4] Very low Earth orbit (VLEO) is defined as altitudes between approximately 100 - 450 km above Earth’s surface. [5] [6] Low Earth orbit (LEO): geocentric orbits with altitudes below 2,000 km (1,200 mi). [7]
Earth radius (denoted as R 🜨 or R E) is the distance from the center of Earth to a point on or near its surface. Approximating the figure of Earth by an Earth spheroid (an oblate ellipsoid), the radius ranges from a maximum (equatorial radius, denoted a) of nearly 6,378 km (3,963 mi) to a minimum (polar radius, denoted b) of nearly 6,357 km (3,950 mi).
Accurately determining its size is difficult: one indicative estimate of its radius is 350 ± 57.5 km. [7] Two objects were named as dwarf planets, under the expectation that they would prove to be so (though this remains uncertain). Haumea has two moons, Hiʻiaka and Namaka, of radii ~195 and ~100 km, respectively. [8]
The actual Hill radius for the Earth-Moon pair is on the order of 60,000 km (i.e., extending less than one-sixth the distance of the 378,000 km between the Moon and the Earth). [ 9 ] In the Earth-Sun example, the Earth ( 5.97 × 10 24 kg ) orbits the Sun ( 1.99 × 10 30 kg ) at a distance of 149.6 million km, or one astronomical unit (AU).
The energy required to reach Earth orbital velocity at an altitude of 600 km (370 mi) is about 36 MJ/kg, which is six times the energy needed merely to climb to the corresponding altitude. [4] Spacecraft with a perigee below about 2,000 km (1,200 mi) are subject to drag from the Earth's atmosphere, [5] which decreases the orbital altitude. The ...
A geostationary equatorial orbit (GEO) is a circular geosynchronous orbit in the plane of the Earth's equator with a radius of approximately 42,164 km (26,199 mi) (measured from the center of the Earth). [21]: 156 A satellite in such an orbit is at an altitude of approximately 35,786 km (22,236 mi) above mean sea level. It maintains the same ...
Clickable image, highlighting medium altitude orbits around Earth, [a] from Low Earth to the lowest High Earth orbit (geostationary orbit and its graveyard orbit, at one ninth of the Moon's orbital distance), [b] with the Van Allen radiation belts and the Earth to scale To-scale diagram of low, medium, and high Earth orbits Space of Medium Earth orbits (MEO) as pink area, with Earth and the ...