Source: https://ntrs.nasa.gov/api/citations/20110007876/downloads/20110007876.pdf

• Generally only effects spacecraft in LEO
• Important consideration for orbit planning (out of scope of this project)
• Important consideration for orbit prediction and tracking

Theory: When center of atmospheric pressure is not aligned with center of mass, a torque results

Type: Constant

Formula:

$$ T_a=\frac{1}{2}\rho C_d A_rV^2(cp_a-cm) $$

$T_a$ is the atmospheric drag torque

$\rho$ is the atmospheric density in $kg/m^3$

$C_d$ is the drag coefficient (usually between 2.0 and 2.5 for spacecraft)

$A_r$ is the ram area in $m^2$

$V$ is the spacecraft’s orbital velocity in $m/s$

$cp_a$ and $cm$ are the centers of aerodynamic pressure and mass in $m$

“Average atmospheric density and orbital velocity as functions of altitude are tabulated in the Appendices of this text” - from Source

Taken from SMAD (2005) Table 11-9A

Type: Constant for Earth-oriented vehicles, variable for inertially oriented vehicle

Influenced Primarily By:

• Orbit altitude