siderealTime

Greenwich mean and apparent sidereal times

Since R2021a

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.

Examples

Calculate Greenwich Sidereal Times for Particular Date

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);

Calculate Greenwich Sidereal Times for Whole Month

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

utcJD — UTC as Julian date

scalar

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

dUT1 — Difference between CUT and UT1

0 (default) | scalar

Difference between the Coordinated Universal Time (UTC) and Universal Time (UT1), specified as a scalar, in seconds.

dAT — Difference between TAI and UTC

0 (default) | scalar

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

Output Arguments

thGMST — Greenwich mean sidereal time

scalar

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

thGAST — Greenwich apparent sidereal time

scalar

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

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