The constant subpackage defines several constants that are useful when working with gravity and topography data of the terrestrial planets. All units are SI. Confer with the constant’s info() method for exact values and references.

Fundamental constants

Constant Description
grav_constant Gravitational Constant
pi_constant Pi
mu0_constant Magnetic constant

Mercury

Constant Description
r_mercury Average radius of Mercury
gm_mercury Gravitational constant times the mass of Mercury
mass_mercury Mass of Mercury
r0_pot_mercury Reference radius used for the spherical harmonic gravity solutions
omega_mercury_orbit Angular rotation rate of Mercury about the Sun
omega_mercury_spin Angular rotation rate of Mercury
rho_bar_mercury Average density of Mercury
g0_mercury Gravitational acceleration at r_mercury, not including rotation

Venus

Constant Description
r_venus Average radius of Venus
r0_pot_venus Reference radius of the gravitational-potential models of Venus
gm_venus Gravitational constant times the mass of Venus
mass_venus Mass of Venus
omega_venus Angular rotation rate of Venus
rho_bar_venus Average density of Venus
g0_venus Gravitational acceleration at R_Venus, not including rotation

Earth

Constant Description
gm_earth Gravitational constant times the mass of Earth
r0_pot_earth Reference radius of the terrestrial gravitational-potential models
mass_earth The mass of Earth
wgs84_a The semi-major axis of the WGS84 ellipsoid
wgs84_b The semi-minor axis of the WGS84 ellipsoid
wgs84_r3 The radius of a sphere of Earth’s volume
wgs84_f The flattening of the WGS84 ellipsoid
wgs84_gm The adopted GM of the WGS84 model, which includes the atmosphere
wgs84_gma The GM of the atmosphere adopted by the WGS84 model
wgs84_omega The adopted angular rotation rate of Earth of the WGS84 model
wgs84_u0 The theoretical normal potential associated with the WGS84 model

The Moon

Constant Description
r_moon Mean radius of the Moon
gm_moon Gravitational constant times the mass of the Moon
mass_moon Mass of the Moon
rho_bar_moon Average density of the Moon
a_moon Semi-major axis of the lunar orbit
g0_moon Mean gravitational acceleration of the Moon at the mean surface radius (r_moon), not including rotation
r0_pot_moon Reference radius of the gravitational-potential models of the Moon
omega_moon Angular rotation rate of the Moon
c_moi_moon Polar moment of inertia of the Moon, using R=1738 km
i_moi_moon Average moment of inertia of the Moon, using R=1738 km
gamma_moi_moon Libration parameter of the Moon, (B-A)/C
beta_moi_moon Libration parameter of the Moon, (C-A)/B

Mars

Constant Description
r_mars Average radius of Mars
gm_mars Gravitational constant times the mass of Mars
mass_mars Mass of Mars
rho_bar_mars Average density of Mars
g0_mars Gravitational acceleration of Mars at r_mars, not including rotation
r0_pot_mars Reference radius of the gravitational-potential models of Mars
omega_mars Angular rotation rate of Mars
f_mars Topographic flattening of Mars
a_mars Semi-major axis radius of Mars
b_mars Semi-minor axis radius of Mars
w0_mars Reference potential of Mars
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