siderealTime

R2026b

Greenwich mean and apparent sidereal times

collapse all in page

Syntax

thGMST = siderealTime(utcJD)
thGMST = siderealTime(utcJD, dUT1, dAT)
[thGMST,thGAST] = siderealTime(utcJD,dUT1,dAT)

Description

thGMST = siderealTime(utcJD) calculates mean sidereal time at a specific Coordinated Universal Time (UTC), specified as a Julian date.

thGMST = siderealTime(utcJD, dUT1, dAT) calculates mean sidereal time at a specific Coordinated Universal Time (UTC) at a higher precision using Earth orientation parameters.

[thGMST,thGAST] = siderealTime(utcJD,dUT1,dAT) calculates mean and apparent sidereal times.

Note

Apparent sidereal time calculation requires that you download ephemeris data using the Add-On Explorer. To start the Add-On Explorer, in the MATLAB® Command Window, type aeroDataPackage. on the MATLAB desktop toolstrip, click the Add-Ons button.

example

Examples

collapse all

Open Live Script

This example shows how to calculate Greenwich sidereal times at 12:00 on January 4, 2019.

jd = juliandate([2019 1 4 12 0 0]);
[thGMST, thGAST] = siderealTime(jd);
Open Live Script

This example shows how to calculate Greenwich sidereal times at 12:00 for the month of January, 2019.

dates = datetime([2019 1 4 12 0 0]);
dates = dates + days(1:30)';
jdJan = juliandate(dates);
[thGMST, thGAST] = siderealTime(jdJan);

Input Arguments

collapse all

Coordinated Universal Time (UTC) as a Julian date, specified as a scalar.

Tip

To calculate the Julian date for a particular date, use the juliandate function.

Data Types: double

Difference between UT1 and UTC, defined as dUT1 = UT1 – UTC, specified as a scalar, in seconds. This value is published by the International Earth Rotation and Reference Systems Service (IERS) as part of Earth orientation parameter (EOP) data.

Difference between International Atomic Time (TAI) and Coordinated Universal Time (UTC), specified as a scalar, in seconds.

Output Arguments

collapse all

Greenwich mean sidereal time, specified as a scalar, in degrees.

Greenwich apparent sidereal time, specified as a scalar, in degrees.

References

[1] Vallado, D. A. Fundamentals of Astrodynamics and Applications. alg. 1 and eqs. 1-63. New York: McGraw-Hill, 1997.

Version History

Introduced in R2021a

See Also

| | | (Aerospace Blockset)