BSTAR

BSTAR is a way of modeling aerodynamic drag on a satellite in the SGP4 satellite orbit propagation model.

Traditionally, aerodynamic resistance ("drag") is given by

F_{D}={\frac {1}{2}}\rho C_{d}Av^{2}

where $\rho$ is the air density, $C_{d}$ is the drag coefficient, $A$ is the frontal area, and $v$ is the velocity.

The acceleration due to drag is then

a_{D}={\frac {F_{D}}{m}}={\frac {\rho C_{d}Av^{2}}{2m}}

In aerodynamic theory, the factor

B={\frac {C_{d}A}{m}}

is called the ballistic coefficient, and its unit is area per mass. Further incorporating a reference air density and the factor of two in the denominator, we get the starred ballistic coefficient:

B^{*}={\frac {\rho _{0}B}{2}}={\frac {\rho _{0}C_{d}A}{2m}}

thus reducing the expression for the acceleration due to drag to

a_{D}={\frac {\rho }{\rho _{0}}}B^{*}v^{2}

As it can be seen, $B^{*}$ has a unit of inverse length. For orbit propagation purposes, there is a field for BSTAR drag in Two-line element set (TLE) files, where it is to be given in units of inverse Earth radii. The corresponding reference air density is given as 2.461e-5 kg/m^2/Earth radii.^[1]

References

↑ https://celestrak.com/NORAD/documentation/spacetrk.pdf

Gravitational orbits

Types

General	Box Capture Circular Elliptical / Highly elliptical Escape Graveyard Hyperbolic trajectory Inclined / Non-inclined Osculating Parabolic trajectory Parking Synchronous semi sub Transfer orbit

Geocentric	Geosynchronous Geostationary Sun-synchronous Low Earth Medium Earth High Earth Molniya Near-equatorial Orbit of the Moon Polar Tundra

About other points	Areosynchronous Areostationary Halo Lissajous Lunar Heliocentric Heliosynchronous

Parameters

Shape Size	$e$ Eccentricity $a$ Semi-major axis $b$ Semi-minor axis $Q$ , $q$ Apsides

Orientation	$i$ Inclination $Ω$ Longitude of the ascending node $ω$ Argument of periapsis $ϖ$ Longitude of the periapsis

Position	$M$ Mean anomaly $ν$ True anomaly $E$ Eccentric anomaly $L$ Mean longitude $l$ True longitude

Variation	$T$ Orbital period $n$ Mean motion $v$ Orbital speed $t 0$ Epoch

Maneuvers

Orbital mechanics

List of orbits

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