Questions tagged [celestial-mechanics]

Questions regarding the movements and interactions of astronomical bodies as it relates to spacecraft, their trajectories, and their maneuvers. For the motion of spacecraft themselves, see [orbital-mechanics].

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Understanding formula for geocentric position of Moon

I am trying to understand a basic formula in a Celestial Mechanics reference. The formula is for the position of the Moon in a geocentric frame. The reference claims in line (981) that this should be ...
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Planetary migration due to tidal forces

The fine U. Washington article Some potentially habitable planets began as gaseous, Neptune-like worlds mentions twice that tidal forces can induce inward planet migration. Two phenomena known to ...
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Why does ESA's TGO satellite not permanently serve as relay for Perseverance?

This question is about the orbital parameters of ESA's ExoMars Trace Gas Orbiter (TGO), so I am optimisitic that it belongs on astronomy SE. More specifically, it is about the orbital geometry of TGO ...
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How to calculate the maximum heliocentric speed during a flyby?

The following graphs are related to the Voyager 2 / Jupiter flyby occurred on July 1979 (I did the calculation with the SPICE library and NAIF’s data files). We see that the maximum speed relative to ...
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Is Mercury's orbit still considered potentially unstable (in the very long term)?

The subsection Mercury–Jupiter 1:1 perihelion-precession resonance in the Wikipedia article Stability of the Solar System links to the article Solar system could go haywire before the Sun dies in the ...
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What does the term “libration point gateway” mean?

In the Circular Restricted Three Body Problem, natural paths exist between periodic orbits or the libration points that have negligible cost. These are commonly known as free transfers between ...
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Can the location of an unknown planet that is absent from a planetary system be calculated from the orbits of the remaining planets?

In the book ‘Seeker’ by Richard McDevitt, two characters search for a lost planet. They know the star system currently has a number of celestial bodies in orbit around it and their orbits are ...
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How can you construct the periodic orbits around libration points L1 and L2 in the circular restricted three-body problem and prove their existence?

Following up on a previous question about the classification of periodic orbits, how can they be constructed, especially the planar Lyapunov family, around libration points $L_1$ and $L_2$? And how ...
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How to get the coordinates from NASA JPL Ephemerides DE430 ( ECRS) to ECI?

I'm trying to make a software that determines the orbit of a satellite which is affected by the Sun and Moon. The coordinates [x y z] that I have for the satellite are in Eci. For the position of the ...
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How to derive the differential equations of motion for a dumbbell system ,eg. dumbbell satellites around earth?

From Eq. 2.13 from Orbital Mechanics for Engineering Students (Curtis, 2005) the equation of relative motion between two bodies orbiting around a center of mass can be written as: $$\ddot{\mathbf{r}}...
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How to calculate the time of closest approach between two orbiting objects

I have two objects each one moves in elliptic orbit I calculated the distance of closest approach using (the minimum intersection disatnce).Knowing the true anomalies for both objects corresponding to ...
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Calculating the length of a launch window?

May somebody guide me what exactly determines the length of a launch window? When doing the (basic) celestrial mechanics caclulations for e.g. a transit from Earth to Venus, one usually assumes point-...
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Calculating Orbital Velocity without Semi-Major-Axis

When playing Kerbal Space Program, I realized that there is a difference between surface speed and orbital speed; this difference is quite variable, although the Kerbin's surface speed is only 175 m/s....
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How is it possible to connect trajectories at a Poincare section using the “bisection” method?

When constructing a heteroclinic connection (a connection between two different periodic orbits at two different libration points), the stable and unstable manifolds of two different libration points ...