org.opencadc.erfa

Class ERFALib

java.lang.Object

org.opencadc.erfa.ERFALib

public class ERFALib
extends java.lang.Object

ERFALib is a Java JNI wrapper around Time transformations in the ERFA (Essential Routines for Fundamental Astronomy) C library. Specifically:

TIA to TT TAI to UTC TT to TAI UTC to TAI

where

TAI - International Atomic Time TT - Terrestrial Time UTC - Coordinated Universal Time

Constructor Summary

Constructors

Constructor and Description
ERFALib()

Method Summary

Modifier and Type	Method and Description
static double[]	tai2tt(double tai1, double tai2) Time scale transformation: International Atomic Time, TAI, to Terrestrial Time, TT.
static double[]	tai2utc(double tai1, double tai2) Time scale transformation: International Atomic Time, TAI, to Coordinated Universal Time, UTC.
static double[]	tt2tai(double tt1, double tt2) Time scale transformation: Terrestrial Time, TT, to International Atomic Time, TAI.
static double[]	tt2utc(double tt1, double tt2) Convenience method to transform TT to UTC by calling TT to TAI and TAI to UTC.
static double[]	utc2tai(double utc1, double utc2) Time scale transformation: Coordinated Universal Time, UTC, to International Atomic Time, TAI.
static double[]	utc2tt(double utc1, double utc2) Convenience method to transform UTC to TT by calling UTC to TAI and TAI to TT.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ERFALib

public ERFALib()

Method Detail

tt2utc

public static double[] tt2utc(double tt1,
                              double tt2)
                       throws ERFALibException,
                              DubiousYearException,
                              UnacceptableDateException

Convenience method to transform TT to UTC by calling TT to TAI and TAI to UTC.

tt1+tt2 is a two part Julian Date, apportioned in any convenient way between the two arguments, for example where tt1 is the Julian Day Number and tt2 is the fraction of a day. The returned utc1+utc2 form an analogous pair, except that a special convention is used, to deal with the problem of leap seconds.

JD cannot unambiguously represent UTC during a leap second unless special measures are taken. The convention in the present function is that the returned quasi-JD UTC1+UTC2 represents UTC days whether the length is 86399, 86400 or 86401 SI seconds.

Parameters:

tt1 - TT as a 2-part Julian Date.

tt2 - TT as a 2-part Julian Date.

Returns:

UTC as a 2-part quasi Julian Date.

Throws:

ERFALibException - if an error occurs doing the transformation.

DubiousYearException - if a date predates the introduction of the UTC timescale or are too far in the future to be trusted.

UnacceptableDateException - if a date is so early that a Julian Date could not be computed.

utc2tt

public static double[] utc2tt(double utc1,
                              double utc2)
                       throws DubiousYearException,
                              UnacceptableDateException,
                              ERFALibException

Convenience method to transform UTC to TT by calling UTC to TAI and TAI to TT.

utc1+utc2 is a 2-part Julian Date, apportioned in any convenient way between the two arguments, for example where tai1 is the Julian Day Number and tai2 is the fraction of a day. The returned tt1+tt2 follow suit.

JD cannot unambiguously represent UTC during a leap second unless special measures are taken. The convention in the present function is that the JD day represents UTC days whether the length is 86399, 86400 or 86401 SI seconds. In the 1960-1972 era there were smaller jumps (in either direction) each time the linear UTC(TAI) expression was changed, and these "mini-leaps" are also included in the ERFA convention.

Parameters:

utc1 - UTC as a 2-part quasi Julian Date.

utc2 - UTC as a 2-part quasi Julian Date.

Returns:

TT as a 2-part Julian Date.

Throws:

ERFALibException - if an error occurs doing the transformation.

DubiousYearException - if a date predates the introduction of the UTC timescale or are too far in the future to be trusted.

UnacceptableDateException - if a date is so early that a Julian Date could not be computed.

tai2tt

public static double[] tai2tt(double tai1,
                              double tai2)
                       throws ERFALibException

Time scale transformation: International Atomic Time, TAI, to Terrestrial Time, TT.

tai1+tai2 is a two part Julian Date, apportioned in any convenient way between the two arguments, for example where tai1 is the Julian Day Number and tai2 is the fraction of a day. The returned tt1,tt2 follow suit.

Parameters:

tai1 - TAI as a 2-part Julian Date

tai2 - TAI as a 2-part Julian Date

Returns:

TT as a 2-part Julian Date.

Throws:

ERFALibException - if an error occurs doing the conversion.

tai2utc

public static double[] tai2utc(double tai1,
                               double tai2)
                        throws ERFALibException,
                               DubiousYearException,
                               UnacceptableDateException

Time scale transformation: International Atomic Time, TAI, to Coordinated Universal Time, UTC.

tai1+tai2 is a 2-part Julian Date, apportioned in any convenient way between the two arguments, for example where tai1 is the Julian Day Number and tai2 is the fraction of a day. The returned utc1+utc2 form an analogous pair, except that a special convention is used, to deal with the problem of leap seconds.

JD cannot unambiguously represent UTC during a leap second unless special measures are taken. The convention in the present function is that the JD day represents UTC days whether the length is 86399, 86400 or 86401 SI seconds. In the 1960-1972 era there were smaller jumps (in either direction) each time the linear UTC(TAI) expression was changed, and these "mini-leaps" are also included in the ERFA convention.

Parameters:

tai1 - TAI as a 2-part Julian Date.

tai2 - TAI as a 2-part Julian Date.

Returns:

UTC as a 2-part quasi Julian Date.

Throws:

ERFALibException - if an error occurs doing the transformation.

DubiousYearException - if a date predates the introduction of the UTC timescale or are too far in the future to be trusted.

UnacceptableDateException - if a date is so early that a Julian Date could not be computed.

tt2tai

public static double[] tt2tai(double tt1,
                              double tt2)
                       throws ERFALibException

Time scale transformation: Terrestrial Time, TT, to International Atomic Time, TAI.

tt1+tt2 is a two part Julian Date, apportioned in any convenient way between the two arguments, for example where tt1 is the Julian Day Number and tt2 is the fraction of a day. The returned tai1+tai2 follow suit.

Parameters:

tt1 - TT as a 2-part Julian Date

tt2 - TT as a 2-part Julian Date

Returns:

TAI as a 2-part Julian Date.

Throws:

ERFALibException - if an error occurs doing the conversion.

utc2tai

public static double[] utc2tai(double utc1,
                               double utc2)
                        throws ERFALibException,
                               DubiousYearException,
                               UnacceptableDateException

Time scale transformation: Coordinated Universal Time, UTC, to International Atomic Time, TAI.

utc1+utc2 is a 2-part Julian Date, apportioned in any convenient way between the two arguments, for example where tai1 is the Julian Day Number and tai2 is the fraction of a day. The returned tai1+tai2 follow suit.

JD cannot unambiguously represent UTC during a leap second unless special measures are taken. The convention in the present function is that the JD day represents UTC days whether the length is 86399, 86400 or 86401 SI seconds. In the 1960-1972 era there were smaller jumps (in either direction) each time the linear UTC(TAI) expression was changed, and these "mini-leaps" are also included in the ERFA convention.

Parameters:

utc1 - UTC as a 2-part quasi Julian Date.

utc2 - UTC as a 2-part quasi Julian Date.

Returns:

TAI as a 2-part Julian Date.

Throws:

ERFALibException - if an error occurs doing the transformation.

DubiousYearException - if a date predates the introduction of the UTC timescale or are too far in the future to be trusted.

UnacceptableDateException - if a date is so early that a Julian Date could not be computed.