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Delta UT1

Calculate difference between principal Universal Time (UT1) and Coordinated Universal Time (UTC) according to International Astronomical Union (IAU) 2000A reference system

  • Delta UT1 block

Aerospace Blockset / Environment / Celestial Phenomena
Aerospace Blockset / Utilities / Axes Transformations


The Delta UT1 block calculates the difference between principal UT1 and UTC according to the IAU 2000A reference system and Earth orientation data. By default, this block uses a prepopulated list of International Earth Rotation and Reference Systems Service (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, Delta UT1 calculates the data using this equation, limiting the values to +/- .9s:




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UT1 for UTC, specified as a modified Julian date. Use the mjuliandate function to convert the UTC date to a modified Julian date.

Data Types: double

Output Arguments

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Difference between UT1 and UTC.

Data Types: double


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

Programmatic Use

Block Parameter: FileName
Type: character vector
Values: 'aeroiersdata.mat' | MAT-file
Default: 'aeroiersdata.mat'

Out-of-range block behavior, specified as:



No action.


Warning in the Diagnostic Viewer, model simulation continues.

Error (default)

Error in the Diagnostic Viewer, model simulation stops.

Programmatic Use

Block Parameter: action
Type: character vector
Values: 'None' | 'Warning' | 'Error'
Default: 'Warning'

Web site or Earth orientation data file containing the Earth orientation data according to the IAU 2000A, specified as a web site address or file name.


If you receive an error message while accessing the default site, use one of these alternate sites:



Programmatic Use

Block Parameter: iersurl
Type: character vector
Values: '' | web site address | file name
Default: ''

Folder for IERS data file, specified as a character array or string. Before running this function, create foldername with write permission.

To create the IERS data file in the destination folder, click the Create button.

Programmatic Use

Block Parameter: folder
Type: character vector
Values: 'Current Folder' | folder name
Default: 'Current Folder'

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2017b

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