Vai's Uni Notes

Satellite-Centered Coordinate Systems

1 min read

Frames that ride along with a satellite: the natural frames for Relative Motion.

Definition

  • In terms of the three choices:
    • Center: the particular satellite of interest
    • Type: usually Cartesian
    • Orientation: the polar axis is ̂𝐖=̂𝐡, perpendicular to the orbital plane
      • RSW: principal axis aligns with the radial vector
      • NTW: the second axis aligns with the velocity vector

Names

  • RSW = local vertical local horizontal “LVLH”
  • Not used here: radial-in-track-crosstrack “RIC”
    • “in-track” is corrected to along-track in the notes
  • Radial-transverse-normal “RTN”

RSW Frame

  • ̂𝐑 = radial direction
  • ̂𝐖 = angular momentum direction
  • ̂𝐒=̂𝐖×̂𝐑
  • ̂𝐒 is along the velocity only for circular orbits (in general the velocity has a radial part)

NTW Frame

  • ̂𝐓 = velocity vector direction
  • ̂𝐖 = angular momentum direction
  • ̂𝐍=̂𝐓×̂𝐖
  • ̂𝐍 is in the orbital plane, normal to the velocity

Building RSW from a state vector

Graph View

Backlinks