This subpackage defines several constants that are used in analyzing gravity, topography, and magnetic field data of the terrestrial planets. Each object is an astropy Constant that possesses the attributes name, value, unit, uncertainty, and reference.

## Fundamental constants

Constant Description
G Gravitational Constant
mu0 Magnetic constant

## Mercury

Constant Description
r_mercury Average radius of Mercury
gm_mercury Gravitational constant times the mass of the Mercury
mass_mercury Mass of Mercury
omega_orbit_mercury Angular rotation rate of Mercury about the Sun
omega_mercury Angular rotation rate of Mercury
density_mercury Average density of Mercury
g0_mercury Gravitational acceleration at r_mercury, not including rotation

## Venus

Constant Description
r_venus Average radius of Venus
gm_venus Gravitational constant times the mass of the Venus
mass_venus Mass of Venus
omega_venus Angular rotation rate of Venus
density_venus Average density of Venus
g0_venus Gravitational acceleration at r_venus, not including rotation

## Earth

Constant Description
gm_egm2008 Gravitational constant times the mass of Earth from the EGM2008 model
mass_egm2008 The mass of Earth from the EGM2008 model
a_wgs84 The semi-major axis of the WGS84 ellipsoid
b_wgs84 The semi-minor axis of the WGS84 ellipsoid
r3_wgs84 The radius of a sphere of Earth’s volume
f_wgs84 The flattening of the WGS84 ellipsoid
gm_wgs84 The adopted GM of the WGS84 model, which includes the atmosphere
mass_wgs84 The mass of Earth from the WGS84 model, which includes the atmosphere
gma_wgs84 The GM of the atmosphere adopted by the WGS84 model
omega_wgs84 The adopted angular rotation rate of the Earth of the WGS84 model
u0_wgs84 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
density_moon Average density of the Moon
a_orbit_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
omega_moon Angular rotation rate of the Moon
i_solid_moon Average moment of inertial of the solid portion of the Moon
gamma_moon Libration parameter of the Moon, (B-A)/C
beta_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
density_mars Average density of Mars
g0_mars Gravitational acceleration of Mars at r_mars, not including rotation
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
u0_mars Reference potential of Mars
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