osculating orbit مدارِ آبوسنده madâr-e âbusandé
*Fr.: orbite osculatrice*
The Keplerian orbit that a satellite would follow after a specific time *t*
if all forces other than central inverse-square forces ceased to act from time *t* on.
An osculating orbit is tangent to the real, perturbed, orbit and has the same
velocity at the point of tangency. → *osculating*; → *orbit*. |

parabolic orbit مدار ِ سهمی madâr-e sahmi
*Fr.: orbite parabolique*
An orbit whose overall shape is like a parabola; it is the limiting case
between an elliptical orbit (eccentricity less than 1) and a hyperbolic orbit
(eccentricity larger than 1). The speed necessary to form a parabolic orbit is known as
the escape velocity. → *parabolic*; → *orbit*. |

polar orbit مدار ِ قطبی madâr-e qotbi (#)
*Fr.: orbite polaire*
A spacecraft orbit that passes over, or close to, the geographic poles of the
Earth or some other solar system object. → *polar*; → *orbit*. |

polar orbiting satellite ماهواره با مدار ِ قطبی mâhvâré bâ madâr-e qotbi
*Fr.: satellite en orbite polaire*
A satellite that revolves around the Earth in an almost north-south orbit,
passing close to both poles. The orbits are sun synchronous, allowing the
satellite to cross the equator at the same local time each day.
These satellites orbit at a height of 830-880 km and
take about 100 minutes to complete a turn around the Earth. → *polar*; → *orbit*;
→ *satellite*. |

prograde orbit مدار ِ فرارو madâr-e farârow
*Fr.: orbite prograde*
Same as →*prograde motion*. → *prograde motion*; → *orbit*. |

resonance orbit مدار ِ بازآوایی madâr-e bâzâvâyi
*Fr.: orbite de résonance*
An orbit which is in → *orbital resonance* with
another orbit. → *resonance*; → *orbit*. |

retrograde orbit مدار ِ پسرفت madâr-e pasraft
*Fr.: orbite rétrograde*
An orbit with an inclination between 90° and 270° such as those of
some comets and small asteroids orbiting the Sun. → *retrograde*; → *orbit*. |

Solar Orbiter مدارگرد ِ خورشیدی madârgard-e xoršidi
*Fr.: orbiteur solaire*
A → *European Space Agency* (ESA)
mission with strong
→ *National Aeronautics and Space Administration*
(NASA) participation aimed at
studying the Sun up close and from high latitudes, launched on 10
February 2020. Solar Orbiter is equipped with 10 instruments and will
provide the first images of the Sun's poles.
It will make a close approach of the Sun every six
months. Its distance from the Sun varies from within the orbit of
→ *Mercury*
to close to the orbit of Earth.
At closest approach, Solar Orbiter will be about approximately 42 million
km from the Sun.
Solar Orbiter will combine in situ measurements of the
→ *solar wind*
around the spacecraft with remote sensing, looking at the Sun's
features from afar, to connect the two together.
The spacecraft has been tested to withstand temperatures up to
500 °C -- enduring thirteen times the amount of solar heating
that satellites in Earth's orbit experience.
Solar Orbiter will help us understand how our star creates and
controls the → *heliosphere*, i.e.
the giant bubble of → *plasma*
that surrounds the whole → *Solar System*
and influences the planets within it. → *solar*; → *orbiter*. |

spin-orbit coupling جفسری ِ اسپین-مدار، جفتش ِ ~ jafsari-ye espin-madâr, jofteš-e ~
*Fr.: couplage spin-orbite*
1) *Astro.*: A relationship between the orbital period of one body around another
and its rotational period on its axis. The relationship results from tidal forces
between the two bodies. For example, the rotation period of the Moon equals its revolution
period around the Earth.
2) *Quantum mechanics*:
The interaction between a particle's → *spin angular momentum*
and its → *orbital angular momentum*. → *spin*; → *orbit*;
→ *coupling*. |

stationary orbit مدار ِ ایستور madâr-e istvar
*Fr.: orbite stationnaire*
An orbit in which the satellite revolves about the primary at the
angular rate at which the primary rotates on its axis. From the
primary, the satellite thus appears to be stationary over a point on
the primary. → *stationary*; → *orbit*. |

synchronous orbit مدار ِ همگام madâr-e hamgâm
*Fr.: orbite synchrone*
→ *synchronous rotation*. → *synchronous*; → *orbit*. |

tadpole orbit مدار ِ وگیزی madâr-e vagizi
*Fr.: orbite en forme de têtard*
A shorter → *horseshoe orbit* confined to the
→ *Lagrangian points* L4 or L5. → *tadpole*; → *orbit*. |