137 lines
4.6 KiB
Rust
137 lines
4.6 KiB
Rust
//! Physical and astronomical constants used across the workspace.
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//!
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//! All values are expressed in SI units unless the name or doc comment
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//! states otherwise. Values that are fixed by definition are given exactly;
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//! measured values carry the number of significant digits justified by the
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//! public source.
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//!
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//! Sources:
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//!
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//! - SI defining constants: BIPM, *The International System of Units (SI)*,
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//! 9th edition, 2019.
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//! - CODATA 2018 recommended values: E. Tiesinga et al., *CODATA
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//! recommended values of the fundamental physical constants: 2018*,
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//! Rev. Mod. Phys. 93, 025010, 2021.
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//! - Earth gravitational parameter and equatorial radius: WGS 84,
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//! NIMA TR8350.2, 2000.
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//! - Astronomical unit: IAU 2012 Resolution B2.
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//!
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//! Where a value is defined exactly by a standard, the doc comment says so,
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//! because several derived quantities depend on the exact value rather than
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//! the rounded printed one.
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/// Speed of light in vacuum, in meters per second.
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///
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/// Exact by definition of the metre in the SI.
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pub const SPEED_OF_LIGHT: f64 = 299_792_458.0;
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/// Newtonian constant of gravitation, in cubic meters per kilogram per
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/// second squared.
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///
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/// CODATA 2018 value with its standard uncertainty of
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/// `1.5e-11 m^3 kg^-1 s^-2`.
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pub const GRAVITATIONAL_CONSTANT: f64 = 6.674_30e-11;
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/// Boltzmann constant, in joules per kelvin.
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///
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/// Exact by definition of the kelvin in the SI.
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pub const BOLTZMANN: f64 = 1.380_649e-23;
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/// Planck constant, in joule seconds.
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///
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/// Exact by definition of the kilogram in the SI.
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pub const PLANCK: f64 = 6.626_070_15e-34;
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/// Elementary charge, in coulombs.
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///
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/// Exact by definition of the ampere in the SI.
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pub const ELEMENTARY_CHARGE: f64 = 1.602_176_634e-19;
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/// Astronomical unit, in meters.
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///
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/// Exact by IAU 2012 Resolution B2.
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pub const ASTRONOMICAL_UNIT: f64 = 149_597_870_700.0;
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/// Standard gravity, in meters per second squared.
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///
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/// Exact by definition of the standard atmosphere.
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pub const STANDARD_GRAVITY: f64 = 9.806_65;
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/// One minute, in seconds.
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pub const MINUTE: f64 = 60.0;
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/// One hour, in seconds.
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pub const HOUR: f64 = 3_600.0;
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/// One day of 24 hours, in seconds.
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///
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/// This is the SI day. It is not the mean solar day, which is slightly
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/// longer, and not the Julian day of 86 400 seconds used in Julian date
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/// arithmetic, which is identical to this value.
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pub const DAY: f64 = 86_400.0;
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/// One Julian year of 365.25 days, in seconds.
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///
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/// Exact by definition of the Julian year.
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pub const JULIAN_YEAR: f64 = 31_557_600.0;
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/// One Julian century of 36 525 days, in seconds.
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///
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/// Exact by definition of the Julian year, used by precession and secular
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/// rate expressions quoted per Julian century.
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pub const JULIAN_CENTURY: f64 = 3_155_760_000.0;
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/// Julian date of the Unix epoch, 1970-01-01T00:00:00 UTC.
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///
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/// This is `2 440 587.5` in the Julian date system.
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pub const JULIAN_DATE_UNIX_EPOCH: f64 = 2_440_587.5;
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/// Julian date of the J2000.0 epoch, 2000-01-01T12:00:00 TT.
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///
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/// Exact by definition of the J2000.0 epoch.
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pub const JULIAN_DATE_J2000: f64 = 2_451_545.0;
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/// The number of seconds between the J2000.0 epoch and the Unix epoch.
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///
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/// Derived from [`JULIAN_DATE_J2000`] and [`JULIAN_DATE_UNIX_EPOCH`].
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pub const SECONDS_J2000_TO_UNIX: f64 = (JULIAN_DATE_J2000 - JULIAN_DATE_UNIX_EPOCH) * DAY;
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/// Earth gravitational parameter, in cubic kilometers per second squared.
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///
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/// WGS 84 value, `GM = 398 600.4418 km^3/s^2`, with an uncertainty that is
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/// dominated by the uncertainty in the Newtonian constant of gravitation.
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/// Orbit propagation uses kilometers, so the value is given in those units
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/// rather than in SI.
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pub const EARTH_MU: f64 = 398_600.441_8;
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/// Earth equatorial radius, in kilometers.
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///
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/// WGS 84 semi-major axis, `a = 6 378.137 km`.
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pub const EARTH_EQUATORIAL_RADIUS: f64 = 6_378.137;
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/// Earth flattening, dimensionless.
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///
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/// WGS 84 value, `f = 1 / 298.257 223 563`.
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pub const EARTH_FLATTENING: f64 = 1.0 / 298.257_223_563;
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/// Earth rotation rate, in radians per second.
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///
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/// WGS 84 value. This is the nominal mean angular velocity of the Earth,
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/// `omega = 7.292 115e-5 rad/s`.
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pub const EARTH_ROTATION_RATE: f64 = 7.292_115_0e-5;
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/// Earth second zonal harmonic, dimensionless.
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///
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/// WGS 84 value, `J2 = 1.082 626 683e-3`.
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pub const EARTH_J2: f64 = 1.082_626_683e-3;
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/// Standard atmosphere sea level pressure, in pascals.
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///
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/// Exact by definition of the standard atmosphere.
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pub const STANDARD_ATMOSPHERE: f64 = 101_325.0;
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/// Zero degrees Celsius on the thermodynamic temperature scale, in kelvin.
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///
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/// Exact by definition of the Celsius scale.
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pub const ZERO_CELSIUS_IN_KELVIN: f64 = 273.15;
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