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A non-Sun-synchronous orbit (magenta) is also shown for reference. Dates are shown in white: day/month. A Sun-synchronous orbit (SSO), also called a heliosynchronous orbit, [1] is a nearly polar orbit around a planet, in which the satellite passes over any given point of the planet's surface at the same local mean solar time.
Much more commonly, synchronous orbits are employed by artificial satellites used for communication, such as geostationary satellites. For natural satellites, which can attain a synchronous orbit only by tidally locking their parent body, it always goes in hand with synchronous rotation of the satellite. This is because the smaller body becomes ...
The value of a solar beta angle for a satellite in Earth orbit can be found using the equation = [ + ()] where is the ecliptic true solar longitude, is the right ascension of ascending node (RAAN), is the orbit's inclination, and is the obliquity of the ecliptic (approximately 23.45 degrees for Earth at present).
The synodic period is the amount of time that it takes for an object to reappear at the same point in relation to two or more other objects. In common usage, these two objects are typically Earth and the Sun. The time between two successive oppositions or two successive conjunctions is also equal to the synodic period. For celestial bodies in ...
This prolongs the life-time of the satellite as it consumes less fuel over time, but the satellite can then only be used by ground antennas capable of following the N-S movement. [21]: 156 Geostationary satellites will also tend to drift around one of two stable longitudes of 75° and 255° without station keeping. [21]: 157
[2]: 24 Many other reference frames can be used to meet various application requirements, including those centered on the Sun or on other planets or moons, the one defined by the barycenter and total angular momentum of the solar system (in particular the ICRF), or even a spacecraft's own orbital plane and angular momentum.
In the context of spaceflight, launch period is the collection of days, and launch window is the time period on a given day, during which a particular rocket must be launched in order to reach its intended target. [1] [2] If the rocket is not launched within a given window, it has to wait for the window on the next day of the period. [3]
Two medium Earth orbits are particularly significant. A satellite in the semi-synchronous orbit at an altitude of approximately 20,200 kilometres (12,600 mi) has an orbital period of 12 hours and passes over the same two spots on the equator every day. [1] This reliably predictable orbit is used by the Global Positioning System (GPS ...