greenwichsrt

Greenwich mean and apparent sidereal times

Syntax

[thGMST,thGAST] = greenwichSRT(utcJD)

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

Description

[thGMST,thGAST] = greenwichSRT(utcJD) calculates Greenwich mean and apparent sidereal times at a specific Universal Coordinated Time (UTC). Mean sidereal time accounts only for secular motion (precession). Apparent sidereal time includes secular and periodic contributions.

[thGMST,thGAST] = greenwichSRT(utcJD,dUT1,dAT)calculates Greenwich mean and apparent sidereal times at a higher precision using Earth orientation parameters.

Examples

Calculate Greenwich Sidereal Times

Calculate Greenwich sidereal times at 12:00 on January 4, 2019.

jd = juliandate([2019 1 4 12 0 0]);
[thGMST, thGAST] = greenwichSRT(jd)

thGMST =
  283.8103

thGAST =
  283.8065

Input Arguments

utcJD — UTC as Julian date

scalar

Universal Coordinated 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 seconds.

thGAST — Greenwich apparent sidereal time

scalar

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

Limitations

This function requires the Mapping Toolbox™ license.

References

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