deltaUT1

Calculate difference between Coordinated Universal Time (UTC) and Principal Universal Time (UT1)

Syntax

DUT1=deltaUT1(utc)

[DUT1,DUT1Error]=deltaUT1(utc)

DUT1=deltaUT1(utc,Name,Value)

[DUT1,DUT1Error]=deltaUT1(utc,Name,Value)

Description

DUT1=deltaUT1(utc) calculates the difference between Coordinated Universal Time (UTC) and Principal Universal Time (UT1) for UTC, specified as a modified Julian date (MJD). By default, this function uses a prepopulated list of International Astronomical Union (IAU) 2000A Earth orientation (IERS) data. This list contains measured and calculated (predicted) data supplied by the IERS. The IERS measures and calculates this data for a set of predetermined dates. For dates after those listed in the prepopulated list, deltaUT1 calculates the data by using this equation, limiting the values to +/- .9s:

UT1-UTC=0.5309-0.00123(MJD-57808)-(UT2-UT1) 

[DUT1,DUT1Error]=deltaUT1(utc) returns the error for the difference between Coordinated Universal Time (UTC) and Principal Universal Time (UT1) for UTC.

DUT1=deltaUT1(utc,Name,Value) calculates the difference between UTC and UT1 using additional options specified by one or more Name,Value pair arguments.

[DUT1,DUT1Error]=deltaUT1(utc,Name,Value) returns the error for the difference between Coordinated Universal Time (UTC) and Principal Universal Time (UT1) for UTC.

Examples

Calculate Difference Value for December 28, 2015

This example shows how to calculate the difference between UT1 and UTC values for December 28, 2015.

mjd = mjuliandate(2015,12,28)

mjd = 
57384

dUT1 = deltaUT1(mjd)

dUT1 = 
0.0886

Calculate Difference Value and Error Using IERS Data

This example shows how to calculate the difference between UT1-UTC values for December 28, 2015 and January 10, 2016 using the custom file, aeroiersdata.mat.

mjd = mjuliandate([2015 12 28;2016 1 10])

mjd = 2×1

       57384
       57397

[dUT1,dUT1Err] = deltaUT1(mjd,'Source','aeroiersdata.mat')

dUT1 = 2×1

    0.0886
    0.0648

dUT1Err = 2×1
10-5 ×

    0.3900
    0.7300

Input Arguments

utc — Principal Universal Time (UT1) for UTC

M-by-1 array

Array of UTC dates, specified as an M-by-1 array, represented as modified Julian dates. Use the mjuliandate function to convert the UTC date to a modified Julian date.

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: 'Source','aeroiersdata.mat'

Source — Custom list of Earth orientation data

aeroiersdata.mat (default) | MAT-file

Custom list of Earth orientation data, specified in a MAT-file.

action — Out-of-range action

warning (default) | action

Out-of-range action, specified as a string.

Action to take in case of out-of-range or predicted value dates, specified as a string:

• Warning — Displays warning and indicates that the dates were out-of-range or predicted values.

• Error — Displays error and indicates that the dates were out-of-range or predicted values.

• None — Does not display warning or error.

Data Types: string

Output Arguments

DUT1 — Difference between UT1 and UTC

M-by-1 array

Difference between UT1 and UTC, specified as an M-by-1 array.

DUT1Error — Error for difference between UT1 and UTC

M-by-1 array

Error for difference between UT1 and UTC (UT1-UTC), according to the International Astronomical Union (IAU) 2000A resolutions, specified as an M-by-1 array, in seconds.

Version History

Introduced in R2017b

R2020b: Updated aeroiersdata.mat file

The contents of the aeroiersdata.mat file have been updated. Correspondingly, the output of this function will have different results when using the default value ('aeroiersdata.mat') as the value of Source. The results reflect more accurate external data from the International Earth Rotation and Reference Systems Service (IERS).