graph LR
skyfield_timelib_Time["skyfield.timelib.Time"]
skyfield_timelib_delta_t["skyfield.timelib.delta_t"]
skyfield_timelib_build_delta_t["skyfield.timelib.build_delta_t"]
skyfield_nutationlib_iau2000a["skyfield.nutationlib.iau2000a"]
skyfield_earthlib_sidereal_time["skyfield.earthlib.sidereal_time"]
skyfield_timelib_gast["skyfield.timelib.gast"]
skyfield_data_earth_orientation_morrison_and_stephenson_2004_table["skyfield.data.earth_orientation.morrison_and_stephenson_2004_table"]
skyfield_timelib_nutation_matrix["skyfield.timelib.nutation_matrix"]
skyfield_timelib_Time -- "queries" --> skyfield_timelib_delta_t
skyfield_timelib_Time -- "computes" --> skyfield_timelib_gast
skyfield_timelib_Time -- "generates" --> skyfield_timelib_nutation_matrix
skyfield_timelib_Time -- "provides time context to" --> skyfield_earthlib_sidereal_time
skyfield_timelib_delta_t -- "provides value to" --> skyfield_timelib_Time
skyfield_timelib_build_delta_t -- "consumes data from" --> skyfield_data_earth_orientation_morrison_and_stephenson_2004_table
skyfield_nutationlib_iau2000a -- "is relied on by" --> skyfield_timelib_gast
skyfield_nutationlib_iau2000a -- "is relied on by" --> skyfield_timelib_nutation_matrix
skyfield_earthlib_sidereal_time -- "takes input from" --> skyfield_timelib_Time
skyfield_timelib_gast -- "relies on" --> skyfield_nutationlib_iau2000a
skyfield_data_earth_orientation_morrison_and_stephenson_2004_table -- "provides data to" --> skyfield_timelib_build_delta_t
skyfield_timelib_nutation_matrix -- "relies on" --> skyfield_nutationlib_iau2000a
The Time & Ephemeris Core subsystem is central to Skyfield, handling all time-related calculations, conversions between different time scales, and managing Earth orientation parameters. It embodies the "Computational Engine" and "Data Processing Pipeline" architectural patterns, providing foundational data and calculations for astronomical computations.
The primary class representing time, serving as the central interface for users to interact with various time scales (UTC, TAI, TT, TDB, UT1) and perform time arithmetic. It acts as the main entry point for time-related operations.
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A function responsible for calculating and managing the Delta T (ΔT) value, which is critical for converting between Terrestrial Time (TT) and Universal Time 1 (UT1). It's a core computational element for time scale synchronization.
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A function responsible for preparing the necessary lookup tables for Delta T calculation. It acts as a data preparation component, ensuring delta_t has the required empirical data.
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Implements the International Astronomical Union (IAU) 2000A model, providing the fundamental calculations for Earth's nutation in longitude and obliquity. This is a core computational engine for Earth orientation.
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A function that computes Earth's rotational orientation, specifically Greenwich Sidereal Time. It's a key calculation for determining Earth's precise orientation in space.
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A function that computes Earth's rotational orientation, specifically Greenwich Apparent Sidereal Time (GAST). It refines sidereal time by incorporating nutation effects.
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A data component that provides the empirical historical and predictive data for Earth orientation parameters, including Delta T values. It serves as a crucial data source for time and orientation calculations.
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Generates rotational data for nutation, translating the nutation angles into a transformation matrix. This component is essential for applying Earth orientation corrections in coordinate transformations.
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