Earth-centered frame with Earth-Sun line fixed

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Discussion Overview

The discussion revolves around the concept of an Earth-centered frame where the line from the Earth (or the barycenter of the Earth-Moon system) to the Sun is fixed. Participants explore the implications of such a frame, particularly in relation to the equations of motion and its applications in celestial mechanics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant inquires about references for a frame where the origin is the Earth and the line to the Sun is fixed, suggesting a need for specific literature on this topic.
  • Another participant proposes the synodic coordinate system as a relevant framework, noting its use in analyzing the circular restricted three-body problem (CR3BP) and suggesting keywords for further research.
  • A different participant reiterates the need for references that discuss the equations of motion in the specified frame, emphasizing the importance of this aspect.
  • Further clarification is provided regarding the synodic coordinate system, indicating that if the origin is at the barycenter of the Earth-Sun system, it aligns with this system. However, if the origin is at the Earth's center, the frame becomes non-inertial, introducing additional inertial forces.

Areas of Agreement / Disagreement

Participants do not reach a consensus on specific references but share insights about the synodic coordinate system and its implications. Multiple viewpoints regarding the nature of the frame and its characteristics are present.

Contextual Notes

The discussion highlights the complexity of defining inertial versus non-inertial frames and the associated forces, but does not resolve the mathematical details or assumptions involved in these definitions.

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TL;DR
Looking for references to an Earth-centered frame rotating with the angular velocity of the Earth around the Sun.
I have seen plenty of references to Earth centered inertial frames (axes fixed with respect to the stars) and Earth-centered Earth fixed frames (axes fixed with respect to the Earth, rotating at the Earth's angular velocity of rotation with respect to the stars).

Does anyone know of a reference that uses a frame in which the origin is the Earth (or the barycenter of the Earth-Moon system), and in which the line from the origin to the Sun is fixed (so that the frame rotates at the angular velocity of the Earth around the Sun)?
 
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I think you're looking for the synodic coordinate system. It's used in analysing the circular restricted three-body problem (aka 'CR3BP').
I'm not sure what references you're after, exactly, but maybe looking those keywords up will nett you something. Anything on Lyapunov and horseshoe orbits, or Lagrange points, might be a good place to check.
 
Bandersnatch said:
I'm not sure what references you're after, exactly

Basically looking for something that will discuss the equations of motion in the type of frame I described.
 
PeterDonis said:
Does anyone know of a reference that uses a frame in which the origin is the Earth (or the barycenter of the Earth-Moon system), and in which the line from the origin to the Sun is fixed (so that the frame rotates at the angular velocity of the Earth around the Sun)?
If the origin is at the barycenter of the Earth-Sun system, it's the synodic coordinate system. Used for example to compute the effective potential for Lagrangian points:
https://en.wikipedia.org/wiki/Lagrangian_point#Mathematical_details

If the origin is the Earth's center (or the barycenter of the Earth-Moon system), the rotation axis of the frame is non-inertial, so you have an additional linear inertial force. Like in this link below, Case 5 (just replace Earth & Moon with Sun & Earth):
https://www.vialattea.net/content/tides-and-centrifugal-force/
 
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