Atmospheric drag on an artificial satellite orbiting the Earth

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Discussion Overview

The discussion revolves around calculating the atmospheric drag on an artificial satellite orbiting the Earth, particularly considering the effects of the Earth's rotation on the atmosphere. Participants explore the components of atmospheric drag in a rotating frame versus an inertial reference frame, focusing on the calculations needed for low Earth orbit scenarios.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant notes the need to calculate the x, y, and z components of atmospheric drag while considering the Earth's rotation, expressing confusion about the rotating atmosphere.
  • Another participant points out that the altitude of the satellite is crucial, as atmospheric drag is significant only in low Earth orbits, and mentions the lack of information about the satellite's shape, size, and orientation.
  • Some participants suggest calculating the x/y/z motion of the atmosphere at the satellite's position and subtracting that from the satellite's velocity to determine the relative velocity.
  • A later reply reiterates the method of calculating the atmospheric motion using the Earth's rotation speed and raises a question about how to derive the x/y components of the atmosphere in the satellite's inertial reference frame.
  • One participant introduces the equation for relative velocity using the cross product of position and angular velocity vectors.

Areas of Agreement / Disagreement

Participants generally agree on the need to account for the Earth's rotation in calculating atmospheric drag, but there is no consensus on the specific methods for determining the x/y components of the atmospheric motion or the implications of the satellite's altitude and characteristics.

Contextual Notes

Limitations include the unspecified altitude of the satellite and the lack of details regarding its shape, size, and orientation, which may affect the calculations of atmospheric drag.

Cristiano
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Consider an artificial satellite orbiting the Earth and suppose that the atmosphere co-rotates with the Earth.

I need to calculate x, y and z components of the atmospheric drag.

I know how to calculate the drag in a non-spinning atmosphere and I have all the data to do that, but the Earth’s rotation confuses me.

I know the x, y and z components of the satellite state (position and velocity). The z-axis is the Earth’s rotation axis and the x-axis and y-axis lie on the equatorial plane. The exes do not rotate (it’s an inertial reference frame).

Please, could somebody help me?
 
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The altitude of the satellite is not stated. Atmospheric drag is only significant for objects in low Earth orbits. The shape, size, and orientation of the satellite are also not stated.
 
You can calculate the x/y/z motion of the atmosphere at the position of the satellite and subtract that from the satellite velocity to find the relative velocity.
 
mfb said:
You can calculate the x/y/z motion of the atmosphere at the position of the satellite and subtract that from the satellite velocity to find the relative velocity.

There is no doubt, but how to calculate x/y of the atmosphere (rotating frame) in the satellite reference frame (inertial frame)?
I know that the atmosphere rotates with speed (with an adequate accuracy for me):
Vrot= (6378.137 + alt_satellite) * (2 * PI) / 86162 * cos(lat_satellite) [km/s]
the z component is always 0, but how to calculate x/y components?
 
##\vec v = \vec r \times \vec \omega## with the cross product.
 

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