constants

This module contains constants that are used in the tudatpy library or commonly used in astrodynamic calculations.

References

[1] (1,2,3,4)

NASA SSD. Astrodynamic Parameters, http://ssd.jpl.nasa.gov/?constants#ref, 6th September, 2011, last accessed: 21st February, 2012.

[2] (1,2)

Standish, E.M. (1995) “Report of the IAU WGAS Sub-Group on Numerical Standards”, in Highlights of Astronomy (I. Appenzeller, ed.), Table 1, Kluwer Academic Publishers, Dordrecht

[3]

IAU 2012, Resolution B2. https://www.iau.org/static/resolutions/IAU2012_English.pdf

[4]

Anderson, J.D. Jr. Hypersonic and High-Temperature Gas Dynamics, Second Edition, p469, 2006

[5] (1,2,3)

NIST reference on constants, units and uncertainty. http://physics.nist.gov/cuu/Constants/index.html, last accessed: 11th January, 2013

[6]

Wolfram Research, http://scienceworld.wolfram.com/physics/Stefan-BoltzmannLaw.html, last accessed: 11th January 2013.

Constants

SEA_LEVEL_GRAVITATIONAL_ACCELERATION = 9.80665

Type:

float

Standard gravitational acceleration at sea-level.

JULIAN_DAY = 86400.0

Type:

float

Julian day in seconds [1].

JULIAN_YEAR_IN_DAYS = 365.25

Type:

float

Julian year in Julian days [1].

JULIAN_YEAR = 31557600.0

Type:

float

Julian year in seconds. Result of JULIAN_YEAR_IN_DAYS * JULIAN_DAY.

SIDEREAL_DAY = 86164.09054

Type:

float

Sidereal day in seconds [1].

SIDEREAL_YEAR_IN_DAYS = 365.25636

Type:

float

Sidereal year in Julian days in quasar reference frame [1].

SIDEREAL_YEAR = 31558149.504

Type:

float

Sidereal year in quasar reference frame. Result of SIDEREAL_YEAR_IN_DAYS * JULIAN_DAY.

SPEED_OF_LIGHT = 299792458.0

Type:

float

Speed of light in meters per second [2].

GRAVITATIONAL_CONSTANT = 6.67259e-11

Type:

float

Gravitational constant in \(\mathrm{m}^3/\mathrm{s}^2\) [2].

ASTRONOMICAL_UNIT = 149597870700.0

Type:

float

Astronomical Unit in meters [3].

SPECIFIC_GAS_CONSTANT_AIR = 287.0

Type:

float

The specific gas constant of air in \(\mathrm{J}/(\mathrm{kg} \, \mathrm{K})\) [4].

MOLAR_GAS_CONSTANT = 8.3144598

Type:

float

The molar gas constant in \(\mathrm{J}/(\mathrm{mol} \, \mathrm{K})\) [5]. Also known as universal gas constant.

PLANCK_CONSTANT = 6.62606957e-34

Type:

float

Planck’s constant in \(\mathrm{m}^{2} \, \mathrm{kg}/\mathrm{s}\) [5].

BOLTZMANN_CONSTANT = 1.3806488e-23

Type:

float

The Boltzmann constant (gas constant per particle) in \(\mathrm{m}^{2} \, \mathrm{kg} / ( \mathrm{s}^{2} \, \mathrm{K} )\), [5].

STEFAN_BOLTZMANN_CONSTANT = 5.6703726225913323e-08

Type:

float

Stefan-Boltzmann constant, used for calculating black body radiation intensity in \(\mathrm{J} / (\mathrm{s} \, \mathrm{m}^{2} \, \mathrm{K}^{4} )\) [6].

INVERSE_SQUARE_SPEED_OF_LIGHT = 1.1126500560536185e-17

Type:

float

Precomputed inverse-square of speed of light.

INVERSE_CUBIC_SPEED_OF_LIGHT = 3.711401092196984e-26

Type:

float

Precomputed inverse 3rd power of speed of light.

INVERSE_QUARTIC_SPEED_OF_LIGHT = 1.2379901472361205e-34

Type:

float

Precomputed inverse 4th power of speed of light.

INVERSE_QUINTIC_SPEED_OF_LIGHT = 4.129490633270435e-43

Type:

float

Precomputed inverse 5th power of speed of light.

VACUUM_PERMEABILITY = 1.2566370614359173e-06

Type:

float

Permeability of vacuum.

VACUUM_PERMITTIVITY = 8.85418781762039e-12

Type:

float

Permittivity of vacuum.

LG_TIME_RATE_TERM = 6.969290134e-10

Type:

float

Relative time rate difference between TCG and TT time scales.

JULIAN_DAY_ON_J2000 = 2451545.0

Type:

float

Julian day at J2000, i.e. 01-01-2000, at 12:00 (in TT).

JULIAN_DAY_AT_0_MJD = 2400000.5

Type:

float

Julian day at Modified Julian Date 0, i.e. Nov 17, 1858, 00:00.

E = 2.718281828459045

Type:

float

The constant E is base of the natural logarithm, and is also known as Napier’s constant.

GOLDEN_RATIO = 1.618033988749895

Type:

float

The golden ratio, also known as the divine proportion, golden mean, or golden section, is a number often encountered when taking the ratios of distances in simple geometric figures such as the pentagon, pentagram, decagon and dodecahedron.

COMPLEX_I = 1j

Type:

complex

Independent root of -1, typically denoted \(i\).

PI = 3.141592653589793

Type:

float

The constant PI, denoted \(\pi\), is a real number defined as the ratio of a circle’s circumference \(C\) to its diameter, \(d = 2r\).

TUDAT_NAN = nan

Type:

float

Tudat Not-A-Number (NaN) value.