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Module ut1

celestial_time::scales

Module ut1 

Source
Expand description

Universal Time UT1 time scale.

UT1 is the principal form of Universal Time, defined by Earth’s rotation angle. Unlike atomic time scales (TAI, TT), UT1 tracks the actual rotational position of the Earth, making it essential for astronomical observations and coordinate transformations.

§Background

Earth’s rotation is irregular due to tidal friction, core-mantle coupling, and atmospheric effects. UT1 accumulates an unpredictable offset from UTC (typically |DUT1| < 0.9s). The offset UT1-UTC is published by IERS in Bulletin A/B.

UT1 = UTC + DUT1    (where DUT1 from IERS observations)

§Usage

use celestial_time::{JulianDate, UT1};
use celestial_time::scales::ut1::ut1_from_calendar;

// From Unix timestamp components
let ut1 = UT1::new(0, 0);  // Unix epoch in UT1

// From calendar date
let ut1 = ut1_from_calendar(2000, 1, 1, 12, 0, 0.0);

// From Julian Date
let ut1 = UT1::from_julian_date(JulianDate::j2000());

§Relationship to Other Scales

UT1 is required for:

  • Sidereal time calculations (GMST, GAST, ERA)
  • Earth orientation parameters
  • Topocentric coordinate transformations

Conversion from UTC requires external Earth Orientation Parameters (EOP) data.

Structs§

UT1
Universal Time UT1, based on Earth’s rotation angle.

Functions§

ut1_from_calendar
Creates UT1 from Gregorian calendar components.