Constants

Units

Symbol	Unit
wgs84_a, earth_radius, au, sun_radius, moon_radius, geo_r, jgm3_a	m
mu_earth, mu_moon, mu_sun, GM, jgm3_mu	m³/s²
omega_earth	rad/s
c	m/s
wgs84_f, earth_moon_mass_ratio, jgm3_j2	unitless

consts

Some constants that are useful for satellite dynamics

wgs84_a class-attribute

WGS-84 semiparameter, in meters

wgs84_f class-attribute

WGS-84 flattening, unitless

earth_radius class-attribute

Earth radius along major axis, meters

mu_earth class-attribute

Gravitational parameter of Earth, m^3/s^2

mu_moon class-attribute

Gravitational parameter of Moon, m^3/s^2

mu_sun class-attribute

Gravitational parameter of sun, m^3/s^2

GM class-attribute

Gravitational parameter of Earth, m^3/s^2

omega_earth class-attribute

Scalar Earth rotation rate, rad/s

c class-attribute

Speed of light, m/s

au class-attribute

Astronomical Unit, mean Earth-Sun distance, meters

sun_radius class-attribute

Radius of sun, meters

solar_pressure_1au class-attribute

Solar radiation pressure at 1 AU (1367 W/m^2 / c), N/m^2.

The cannonball SRP force scales this by (AU / d)^2, with d the satellite-Sun distance. The measured solar constant is 1361 W/m^2 (Kopp & Lean 2011; IAU 2015 Resolution B3); 1367 matches GMAT and STK.

moon_radius class-attribute

Radius of moon, meters

earth_moon_mass_ratio class-attribute

Earth mass over Moon mass, unitless

geo_r class-attribute

Distance to Geosynchronous orbit from Earth center, meters

jgm3_mu class-attribute

Earth gravitational parameter from JGM3 gravity model, m^3/s^2

jgm3_a class-attribute

Earth semiparameter from JGM3 gravity model, m

jgm3_j2 class-attribute

"J2" gravity due oblateness of Earth from JGM3 gravity model, unitless