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Extra-close oppositions of Mars happen every 15 to 17 years, when we pass between Mars and the Sun around the time of its perihelion (closest point to the Sun in orbit). The minimum distance between Earth and Mars has been declining over the years, and in 2003 the minimum distance was 55.76 million km, nearer than any such encounter in almost ...
In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter (the combined center of mass) or, if one body is much more massive than the other bodies of the system combined, its speed relative to the center of mass of the most massive body.
If the same sphere were made of lead the small body would need to orbit just 6.7 mm above the surface for sustaining the same orbital period. When a very small body is in a circular orbit barely above the surface of a sphere of any radius and mean density ρ (in kg/m 3), the above equation simplifies to (since M = Vρ = 4 / 3 π a 3 ρ)
A synchronous orbit around Earth that is circular and lies in the equatorial plane is called a geostationary orbit. The more general case, when the orbit is inclined to Earth's equator or is non-circular is called a geosynchronous orbit. The corresponding terms for synchronous orbits around Mars are areostationary and areosynchronous orbits.
As noted above, the orbit as a whole rotates with a mean angular speed Ω=(k−1)ω, where ω equals the mean angular speed of the particle about the stationary ellipse. If the particle requires a time T to move from one apse to the other, this implies that, in the same time, the long axis will rotate by an angle β = Ω T = ( k − 1) ωT ...
Tracking Mars’ wobble, or nutation, enabled the team to measure the size of the core. The RISE data suggested the core has a radius of about 1,140 miles (1,835 kilometers).
An areosynchronous orbit that is equatorial (in the same plane as the equator of Mars), circular, and prograde (rotating about Mars's axis in the same direction as the planet's surface) is known as an areostationary orbit (AEO). To an observer on the surface of Mars, the position of a satellite in AEO would appear to be fixed in a constant ...
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